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The present study focuses on correlations between three parameters: (1) graphite particle size, (2) the ratio of graphite to oxidizing agent (KMnO4 ), and (3) the ratio of graphite to acid (H2SO4 and H3PO4 ), with the reaction yield, structure, and properties of graphene oxide (GO). The correlations are a challenge, as these three parameters can hardly be separated from each other due to the variations in the viscosity of the system. The larger the graphite particles, the higher the viscosity of GO. Decreasing the ratio of graphite to KMnO4 from 1:4 to 1:6 generally leads to a higher degree of oxidation and a higher reaction yield. However, the differences are very small. Increasing the graphite-to-acid-volume ratio from 1 g/60 mL to 1 g/80 mL, except for the smallest particles, reduced the degree of oxidation and slightly reduced the reaction yield. However, the reaction yield mainly depends on the extent of purification of GO by water, not on the reaction conditions. The large differences in the thermal decomposition of GO are mainly due to the bulk particle size and less to other parameters

Nickel-based superalloys are widely employed to manufacture aero-engine turbines due to their high mechanical strength and resistance to corrosion and creep. Vacuum Induction Melting (VIM) is a suitable manufacturing technology because of the reactive nature of the alloying elements; however, the melting process is time-consuming and energy-demanding. This research focuses on increasing the overall efficiency of the process in two ways. Initially, studying the influence of metal-containing crucible composition and thermal properties on the melting. In a semi-industrial VIM facility, 2 kg of Inconel 718 alloy was melted employing Al2O3, ZrO2, MgO, and Al6Si4O13-based crucibles. The Al6Si4O13 and ZrO2-based crucibles reduced energy consumption by 28% and 23%, respectively, compared to the reference crucible of Al2O3. Subsequently, an optimized melting procedure is proposed to reduce the process cycle time and energy demand, saving 10%–20% for all crucibles compared to the standard melting procedure. In addition, the ZrO2 and Al6Si4O13 crucibles reduced total cycle time by 13% and 21%, respectively. During melting, intense dross formation was detected for all crucibles, dissipating faster for Al6Si4O13 and MgO crucibles. Therefore, the metal-crucible interface product was analyzed to understand these mechanisms better, and the four crucibles' chemical reactivity was examined.

Bio-based epoxy thermoset resins have been developed from epoxidized soybean oil (ESO) cured with tannic acid (TA). These two substances of vegetable origin have been gathering attention due to their accessibility, favorable economic conditions, and convenient chemical functionalization. TA’s suitable high phenolic functionalization has been used to crosslink ESO by adjusting the −OH (from TA):epoxy (from ESO) molar ratio from 0.5:1 to 2.5:1. By means of Fourier-transform infrared spectroscopy, resulting in thermosets that evidenced optimal curing properties under moderate conditions (150–160 °C). The thermogravimetric analysis of the cured resins showed thermal stability up to 261 °C, with modulable mechanical and thermal properties determined by differential scanning calorimetry, dynamical mechanical thermal analysis, and tensile testing. Water contact angle measurements (83–87°) and water absorption tests (0.6–4.5 initial weight% intake) were performed to assess the suitability of the resins as waterproof coatings. Electrochemical impedance spectroscopy measurements were performed to characterize the anti-corrosive capability of these coatings on carbon steel substrates. Excellent barrier properties have been demonstrated due to the high electrical isolation and water impermeability of these oil-based coatings, without signs of deterioration over 6 months of immersion in a 3.5 wt.% NaCl solution. These results demonstrate the suitability of the developed materials as anti-corrosion coatings for specific applications.

The Oliana anticline (Southern Pyrenees) has been characterized as an outcrop analogue of a geothermal reservoir using field data (stratigraphy and fracturing) and petrological, petrophysical and petrothermal analyses. Five lithofacies were established including conglomerates, hybrid arenites, lithic arenites, carbonates and evaporites. Petrophysical measurements indicate widely dispersed values of bulk density, connected porosity, permeability and velocity of compressional acoustic waves. Connected porosity is the factor that mostly influences bulk density, compressional wave velocity and permeability. In turn, diagenetic processes (such as dissolution and cementation) and fracturing, coupled with petrological features such as mineral composition, matrix content and grain size, are the most critical factors controlling rock porosity along the Oliana anticline. Thermal conductivity measures reveal a compositional control on the thermal properties of rocks. Thermal characterization of the structure reveals a low conductive area that matches the carbonate and evaporite succession of the anticline core and a highly conductive zone associated with the detrital succession of the fold limbs. The Oliana anticline has been classified as a petrothermal system due to the low permeability values of the studied sedimentary succession. Despite such classification, this contribution provides a useful exploration tool for future studies of non-conventional geothermal and CO storage sites located in folded sedimentary successions in the proximal domain of foreland basins.

The recovery and storage of process heat in industrial applications are some of the key factors to improve the sustainability and reliability of high temperature applications. In this sense, one of the main drawbacks is focused on the selection of proper thermal energy storage (TES) materials. This paper performs a full characterization of four phase change storage materials (PCM), KOH, LiOH, NaNO3 and KNO3, which are proposed for storage applications between 270 and 500 °C, according to the results obtained through differential scanning calorimeter and thermogravimetric analysis. One of the main innovations includes the corrosive evaluation of these materials in a promising alumina forming alloy (OC4), close to their corresponding phase change temperature during 500 h. The physicochemical properties obtained confirm the optimal use of NaNO3 and KNO3 and recommend the use, with caution, of KOH, due to its higher corrosive potential. FeCr2O4, NiCr2O4 and FeAl2O4 were the main protective spinels formed in the alloy surface, however, the cross-section study in the alloy immersed in KOH, revealed a non-uniform behavior, presenting some cracks and spallation in the surface. On the other hand, the proposal of LiOH was disregarded since it presents a narrow operation temperature range between melting and solidification point.

The recovery and storage of process heat in industrial applications are some of the key factors to improve the sustainability and reliability of high temperature applications. In this sense, one of the main drawbacks is focused on the selection of proper thermal energy storage (TES) materials. This paper performs a full characterization of four phase change storage materials (PCM), KOH, LiOH, NaNO3 and KNO3, which are proposed for storage applications between 270 and 500 °C, according to the results obtained through differential scanning calorimeter and thermogravimetric analysis. One of the main innovations includes the corrosive evaluation of these materials in a promising alumina forming alloy (OC4), close to their corresponding phase change temperature during 500 h. The physicochemical properties obtained confirm the optimal use of NaNO3 and KNO3 and recommend the use, with caution, of KOH, due to its higher corrosive potential. FeCr2O4, NiCr2O4 and FeAl2O4 were the main protective spinels formed in the alloy surface, however, the cross-section study in the alloy immersed in KOH, revealed a non-uniform behavior, presenting some cracks and spallation in the surface. On the other hand, the proposal of LiOH was disregarded since it presents a narrow operation temperature range between melting and solidification point.

Electronic materials represent a vast category with wide-ranging properties. Though definitionally, their electronic properties are of interest, study of their thermal properties provides additional important information. Whether to find materials with desirable thermal conductivity—high to dissipate heat or low to limit heat transport—or because the mechanisms underlying heat transport provide insight into the fundamental physics of the material, thermal characterization allows better understanding of such materials.In the study of the thermal properties of materials, optical pump-probe methods are a key tool. Laser-based measurements allow probing of small areas without requiring microfabrication, and the use of pulsed lasers and modulated beams allows measurement of high-speed effects and so small sample areas. Time domain thermoreflectivity (TDTR), which uses modulated pulsed laser beams, stands as a key tool for measurement of the thermal properties of both bulk and thin film samples. This work seeks to provide a detailed introduction to the technique and the mathematical analysis required for such measurements, apply TDTR to interesting materials systems, and push beyond the limits of traditional TDTR with the development of a transducerless time domain reflectance (tTDR) technique which uses the same equipment.Study of thermal properties can provide new insights into the fundamental properties of materials. Metallic vanadium dioxide nanobeams have a much lower thermal conductivity than would be expected given their electrical conductivity, implying that electrons are more effective at carrying charge than heat. This result is not always seen in other sample geometries, and TDTR measurements allow characterization of thin film samples, allowing further study. Unfortunately, the samples measured in this work did not provide high enough electrical conductivity to draw conclusions about electronic thermal transport, but this stands as an interesting line of inves

The recovery and storage of process heat in industrial applications are some of the key factors to improve the sustainability and reliability of high temperature applications. In this sense, one of the main drawbacks is focused on the selection of proper thermal energy storage (TES) materials. This paper performs a full characterization of four phase change storage materials (PCM), KOH, LiOH, NaNO3 and KNO3, which are proposed for storage applications between 270 and 500 °C, according to the results obtained through differential scanning calorimeter and thermogravimetric analysis. One of the main innovations includes the corrosive evaluation of these materials in a promising alumina forming alloy (OC4), close to their corresponding phase change temperature during 500 h. The physicochemical properties obtained confirm the optimal use of NaNO3 and KNO3 and recommend the use, with caution, of KOH, due to its higher corrosive potential. FeCr2O4, NiCr2O4 and FeAl2O4 were the main protective spinels formed in the alloy surface, however, the cross-section study in the alloy immersed in KOH, revealed a non-uniform behavior, presenting some cracks and spallation in the surface. On the other hand, the proposal of LiOH was disregarded since it presents a narrow operation temperature range between melting and solidification point.

Two important biophysical properties, the thermal and UV-Vis screening capacity, of isolated tomato fruit cuticle membranes (CM) have been studied by differential scanning calorimetry (DSC) and UV-Vis spectrometry, respectively. A first order melting, corresponding to waxes, and a second order glass transition (Tg) thermal events have been observed. The glass transition was less defined and displaced toward higher temperatures along the fruit ripening. In immature and mature green fruits, the CM was always in the viscous and more fluid state but, in ripe fruits, daily and seasonal temperature fluctuations may cause the transition between the glassy and viscous states altering the mass transfer between the epidermal plant cells and the environment. CM dewaxing reduced the Tg value, as derived from the role of waxes as fillers. Tg reduction was more intense after polysaccharide removal due to their highly interwoven distribution within the cutin matrix that restricts the chain mobility. Such effect was amplified by the presence of phenolic compounds in ripe cuticle membranes. The structural rigidity induced by phenolics in tomato CMs was directly reflected in their mechanical elastic modulus. The heat capacity (Cprev) of cuticle membranes was found to depend on the developmental stage of the fruits and was higher in immature and green stages. The average Cprev value was above the one of air, which confers heat regulation capacity to CM. Cuticle membranes screened the UV-B light by 99% irrespectively the developmental stage of the fruit. As intra and epicuticular waxes contributed very little to the UV screening, this protection capacity is attributed to the absorption by cinnamic acid derivatives. However, the blocking capacity toward UV-A is mainly due to the CM thickness increment during growth and to the absorption by flavone chalconaringenin accumulated during ripening. The build-up of phenolic compounds was found to be an efficient mechanism to regulate both the

Leather tanned with different agents was pyrolyzed in the presence of CoCl2 and MnCl2 catalysts. A bovine leather sample tanned with two inorganic tanning agents (chromium and titanium salts) and two organic tanning agents (glutaraldehyde and methylacrylic resin) has been used in this study. The samples were soaked in solutions of CoCl2 or MnCl2 of known concentration. The influence on decomposition temperature and the resultant pyrolysis compounds has been evaluated by using thermogravimetric analysis (TG/DTG) and flash pyrolysis (Py-GC/MS). A multivariate analysis has been applied to the pyrolysis products obtained confirming the effect of the catalyst treatment on leather, specifically on samples tanned with organic agents. According to the results, CoCi2 (higher Lewis acidity) shows a greater influence than the MnCI2 (lower Lewis acidity). The results indicate that the presence of chlorides affects the nature of the pyrolysis products, increasing the yield of the aromatic compounds in all the samples, thus improving the added-value of the volatiles. These catalysts reduced slightly the decomposition temperature.

The aim of this study was to evaluate the changes in the characteristics of Eucalyptus spp. from Paraíba Valley region, Sao Paulo - Brazil after torrification process. Torrification is a thermochemical process that occurs at temperatures lower than the pyrolysis process as a pretreatment to improve biomass characteristics for use as biofuel energy in power generation. An experimental study was carried out in a batch reactor at three temperatures (240 °C, 260 °C and 280 °C) with residence time of 30 and 60 minutes. At the indicated operating conditions by elemental analysis, higher heating value and thermogravimetric analysis were evaluated. Result showed that there was a reduction in the oxygen/carbon (O/C) and hydrogen/carbon (H/C) ratios, causing an increase in the thermal energy quality of torrified wood, about of 28 % and 47 % at temperatures of 260 °C with residence time of 60 minutes and 280 °C with 30 minutes, respectively. A thermogravimetric analysis showed that at 260 °C the hemicellulose was almost completely degraded leaving the fuel in better conditions for combustion or gasification processes

The aim of this study was to evaluate the changes in the characteristics of Eucalyptus spp. from Paraíba Valley region, Sao Paulo - Brazil after torrification process. Torrification is a thermochemical process that occurs at temperatures lower than the pyrolysis process as a pretreatment to improve biomass characteristics for use as biofuel energy in power generation. An experimental study was carried out in a batch reactor at three temperatures (240 °C, 260 °C and 280 °C) with residence time of 30 and 60 minutes. At the indicated operating conditions by elemental analysis, higher heating value and thermogravimetric analysis were evaluated. Result showed that there was a reduction in the oxygen/carbon (O/C) and hydrogen/carbon (H/C) ratios, causing an increase in the thermal energy quality of torrified wood, about of 28 % and 47 % at temperatures of 260 °C with residence time of 60 minutes and 280 °C with 30 minutes, respectively. A thermogravimetric analysis showed that at 260 °C the hemicellulose was almost completely degraded leaving the fuel in better conditions for combustion or gasification processes

The aim of this study was to evaluate the changes in the characteristics of Eucalyptus spp. from Paraíba Valley region, Sao Paulo - Brazil after torrification process. Torrification is a thermochemical process that occurs at temperatures lower than the pyrolysis process as a pretreatment to improve biomass characteristics for use as biofuel energy in power generation. An experimental study was carried out in a batch reactor at three temperatures (240 °C, 260 °C and 280 °C) with residence time of 30 and 60 minutes. At the indicated operating conditions by elemental analysis, higher heating value and thermogravimetric analysis were evaluated. Result showed that there was a reduction in the oxygen/carbon (O/C) and hydrogen/carbon (H/C) ratios, causing an increase in the thermal energy quality of torrified wood, about of 28 % and 47 % at temperatures of 260 °C with residence time of 60 minutes and 280 °C with 30 minutes, respectively. A thermogravimetric analysis showed that at 260 °C the hemicellulose was almost completely degraded leaving the fuel in better conditions for combustion or gasification processes

Current optical communication schema are based on TDMA. New schema have been proposed that are based on WDM. A WDM based scheme needs all lasers to be stable at a fixed wavelength. The wavelength of a laser can be modified by temperature changes. In this work, a typical laser used for optical communications is characterized. A thermal-electrical equivalent model is proposed to model the laser. The necessary experiments have been performed to characterize the laser and extract the model parameters. With the model completed, a PI control scheme has been implemented. This implemented control stabilizes the laser to a certain degree but the fabrication and the layout of the packaging prevent a feedback control to have a high performance. Then, a feed-forward control based on measuring the air temperature is implemented. This feed-forward control improves the stability of the laser in front of temperature changes to a satisfactory degree.

Leather tanned with different agents was pyrolyzed in the presence of CoCl2 and MnCl2 catalysts. A bovine leather sample tanned with two inorganic tanning agents (chromium and titanium salts) and two organic tanning agents (glutaraldehyde and methylacrylic resin) has been used in this study. The samples were soaked in solutions of CoCl2 or MnCl2 of known concentration. The influence on decomposition temperature and the resultant pyrolysis compounds has been evaluated by using thermogravimetric analysis (TG/DTG) and flash pyrolysis (Py-GC/MS). A multivariate analysis has been applied to the pyrolysis products obtained confirming the effect of the catalyst treatment on leather, specifically on samples tanned with organic agents. According to the results, CoCi2 (higher Lewis acidity) shows a greater influence than the MnCI2 (lower Lewis acidity). The results indicate that the presence of chlorides affects the nature of the pyrolysis products, increasing the yield of the aromatic compounds in all the samples, thus improving the added-value of the volatiles. These catalysts reduced slightly the decomposition temperature.

The aim of this study was to evaluate the changes in the characteristics of Eucalyptus spp. from Paraíba Valley region, Sao Paulo - Brazil after torrification process. Torrification is a thermochemical process that occurs at temperatures lower than the pyrolysis process as a pretreatment to improve biomass characteristics for use as biofuel energy in power generation. An experimental study was carried out in a batch reactor at three temperatures (240 °C, 260 °C and 280 °C) with residence time of 30 and 60 minutes. At the indicated operating conditions by elemental analysis, higher heating value and thermogravimetric analysis were evaluated. Result showed that there was a reduction in the oxygen/carbon (O/C) and hydrogen/carbon (H/C) ratios, causing an increase in the thermal energy quality of torrified wood, about of 28 % and 47 % at temperatures of 260 °C with residence time of 60 minutes and 280 °C with 30 minutes, respectively. A thermogravimetric analysis showed that at 260 °C the hemicellulose was almost completely degraded leaving the fuel in better conditions for combustion or gasification processes

Heat dissipation and thermal management are central challenges in various areas of science and technology and are critical issues for the majority of nanoelectronic devices. In this review, we focus on experimental advances in thermal characterization and phonon engineering that have drastically increased the understanding of heat transport and demonstrated efficient ways to control heat propagation in nanomaterials. We summarize the latest device-relevant methodologies of phonon engineering in semiconductor nanostructures and 2D materials, including graphene and transition metal dichalcogenides. Then, we review recent advances in thermal characterization techniques, and discuss their main challenges and limitations.

[EN] Eco-effcient Wood Plastic Composites (WPCs) have been obtained using poly(hydroxybutyrate-co-hexanoate) (PHBH) as the polymer matrix, and almond shell flour (ASF), a by-product from the agro-food industry, as filler/reinforcement. These WPCs were prepared with different amounts of lignocellulosic fillers (wt %), namely 10, 20 and 30. The mechanical characterization of these WPCs showed an important increase in their stiffness with increasing the wt % ASF content. In addition, lower tensile strength and impact strength were obtained. The field emission scanning electron microscopy (FESEM) study revealed the lack of continuity and poor adhesion among the PHBH-ASF interface. Even with the only addition of 10 wt % ASF, these green composites become highly brittle. Nevertheless, for real applications, the WPC with 30 wt % ASF is the most attracting material since it contributes to lowering the overall cost of the WPC and can be manufactured by injection moulding, but its properties are really compromised due to the lack of compatibility between the hydrophobic PHBH matrix and the hydrophilic lignocellulosic filler. To minimize this phenomenon, 10 and 20 phr (weight parts of OLA-Oligomeric Lactic Acid per one hundred weight parts of PHBH) were added to PHBH/ASF (30 wt % ASF) composites. Differential scanning calorimetry (DSC) suggested poor plasticization effect of OLA on PHBH-ASF composites. Nevertheless, the most important property OLA can provide to PHBH/ASF composites is somewhat compatibilization since some mechanical ductile properties are improved with OLA addition. The study by thermomechanical analysis (TMA), confirmed the increase of the coeffcient of linear thermal expansion (CLTE) with increasing OLA content. The dynamic mechanical characterization (DTMA), revealed higher storage modulus, E¿, with increasing ASF. Moreover, DTMA results confirmed poor plasticization of OLA on PHBH-ASF (30 wt % ASF) composites, but interesting compatibilization effects.

[EN] In compliance with oncoming emission directives, turbocharging and increasing complexity in the turbocharger system demands a great effort from researchers on the development of effective procedures and tools to cope with the new technological exigencies. This article describes a methodology for studying oil-coking influence in turbocharger performance. A preliminary evaluation and calibration is done. The aim of this work focuses on the development of methodologies and tools that help to evaluate and understand the consequences that degraded oils can generate in the bearing system during enhanced oil-coking procedure. Several experimental tests have been carried out in an engine test bench and using an independent lubrication system that only feeds the turbocharger. The test campaign is done under a specific engine cycle and using oil artificially contaminated at two different levels. The work is divided into two parts. The first part provides a description and definition of test conditions for measuring of the maximum temperature in the bearing system and the second part tackles the measurement and post-processing of the main instantaneous parameters defining the engine and turbocharger behavior.

Almost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field.

Almost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field.

[EN] Eco-effcient Wood Plastic Composites (WPCs) have been obtained using poly(hydroxybutyrate-co-hexanoate) (PHBH) as the polymer matrix, and almond shell flour (ASF), a by-product from the agro-food industry, as filler/reinforcement. These WPCs were prepared with different amounts of lignocellulosic fillers (wt %), namely 10, 20 and 30. The mechanical characterization of these WPCs showed an important increase in their stiffness with increasing the wt % ASF content. In addition, lower tensile strength and impact strength were obtained. The field emission scanning electron microscopy (FESEM) study revealed the lack of continuity and poor adhesion among the PHBH-ASF interface. Even with the only addition of 10 wt % ASF, these green composites become highly brittle. Nevertheless, for real applications, the WPC with 30 wt % ASF is the most attracting material since it contributes to lowering the overall cost of the WPC and can be manufactured by injection moulding, but its properties are really compromised due to the lack of compatibility between the hydrophobic PHBH matrix and the hydrophilic lignocellulosic filler. To minimize this phenomenon, 10 and 20 phr (weight parts of OLA-Oligomeric Lactic Acid per one hundred weight parts of PHBH) were added to PHBH/ASF (30 wt % ASF) composites. Differential scanning calorimetry (DSC) suggested poor plasticization effect of OLA on PHBH-ASF composites. Nevertheless, the most important property OLA can provide to PHBH/ASF composites is somewhat compatibilization since some mechanical ductile properties are improved with OLA addition. The study by thermomechanical analysis (TMA), confirmed the increase of the coeffcient of linear thermal expansion (CLTE) with increasing OLA content. The dynamic mechanical characterization (DTMA), revealed higher storage modulus, E¿, with increasing ASF. Moreover, DTMA results confirmed poor plasticization of OLA on PHBH-ASF (30 wt % ASF) composites, but interesting compatibilization effects.

[EN] In compliance with oncoming emission directives, turbocharging and increasing complexity in the turbocharger system demands a great effort from researchers on the development of effective procedures and tools to cope with the new technological exigencies. This article describes a methodology for studying oil-coking influence in turbocharger performance. A preliminary evaluation and calibration is done. The aim of this work focuses on the development of methodologies and tools that help to evaluate and understand the consequences that degraded oils can generate in the bearing system during enhanced oil-coking procedure. Several experimental tests have been carried out in an engine test bench and using an independent lubrication system that only feeds the turbocharger. The test campaign is done under a specific engine cycle and using oil artificially contaminated at two different levels. The work is divided into two parts. The first part provides a description and definition of test conditions for measuring of the maximum temperature in the bearing system and the second part tackles the measurement and post-processing of the main instantaneous parameters defining the engine and turbocharger behavior.

Almost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field.

Almost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field.

Almost 15 years have gone ever since the discovery of graphene as a single atom layer. Numerous papers have been published to demonstrate its high electron mobility, excellent thermal and mechanical as well as optical properties. We have recently seen more and more applications towards using graphene in commercial products. This paper is an attempt to review and summarize the current status of the research of the thermal properties of graphene and other 2D based materials including the manufacturing and characterization techniques and their applications, especially in electronics and power modules. It is obvious from the review that graphene has penetrated the market and gets more and more applications in commercial electronics thermal management context. In the paper, we also made a critical analysis of how mature the manufacturing processes are; what are the accuracies and challenges with the various characterization techniques and what are the remaining questions and issues left before we see further more applications in this exciting and fascinating field.

[EN] This work reports the potential of poly(lactic acid)-PLA composites with different halloysite nanotube (HNTs) loading (3, 6 and 9 wt%) for further uses in advanced applications as HNTs could be used as carriers for active compounds for medicine, packaging and other sectors. This work focuses on the effect of HNTs on mechanical, thermal, thermomechanical and degradation of PLA composites with HNTs. These composites can be manufactured by conventional extrusion-compounding followed by injection molding. The obtained results indicate a slight decrease in tensile and flexural strength as well as in elongation at break, both properties related to material cohesion. On the contrary, the stiffness increases with the HNTs content. The tensile strength and modulus change from 64.6 MPa/2.1 GPa (neat PLA) to 57.7/2.3 GPa MPa for the composite with 9 wt% HNTs. The elongation at break decreases from 6.1% (neat PLA) down to a half for composites with 9 wt% HNTs. Regarding flexural properties, the flexural strength and modulus change from 116.1 MPa and 3.6 GPa respectively for neat PLA to values of 107.6 MPa and 3.9 GPa for the composite with 9 wt% HNTs. HNTs do not affect the glass transition temperature with invariable values of about 64 degrees C, or the melt peak temperature, while they move the cold crystallization process towards lower values, from 112.4 degrees C for neat PLA down to 105.4 degrees C for the composite containing 9 wt% HNTs. The water uptake has been assessed to study the influence of HNTs on the water saturation. HNTs contribute to increased hydrophilicity with a change in the asymptotic water uptake from 0.95% (neat PLA) up to 1.67% (PLA with 9 wt % HNTs) and the effect of HNTs on disintegration in controlled compost soil has been carried out to see the influence of HNTs on this process, which is a slight delay on it. These PLA-HNT composites show good balanced properties and could represent an interesting solution to develop active materials.

[EN] This work reports the potential of poly(lactic acid)-PLA composites with different halloysite nanotube (HNTs) loading (3, 6 and 9 wt%) for further uses in advanced applications as HNTs could be used as carriers for active compounds for medicine, packaging and other sectors. This work focuses on the effect of HNTs on mechanical, thermal, thermomechanical and degradation of PLA composites with HNTs. These composites can be manufactured by conventional extrusion-compounding followed by injection molding. The obtained results indicate a slight decrease in tensile and flexural strength as well as in elongation at break, both properties related to material cohesion. On the contrary, the stiffness increases with the HNTs content. The tensile strength and modulus change from 64.6 MPa/2.1 GPa (neat PLA) to 57.7/2.3 GPa MPa for the composite with 9 wt% HNTs. The elongation at break decreases from 6.1% (neat PLA) down to a half for composites with 9 wt% HNTs. Regarding flexural properties, the flexural strength and modulus change from 116.1 MPa and 3.6 GPa respectively for neat PLA to values of 107.6 MPa and 3.9 GPa for the composite with 9 wt% HNTs. HNTs do not affect the glass transition temperature with invariable values of about 64 degrees C, or the melt peak temperature, while they move the cold crystallization process towards lower values, from 112.4 degrees C for neat PLA down to 105.4 degrees C for the composite containing 9 wt% HNTs. The water uptake has been assessed to study the influence of HNTs on the water saturation. HNTs contribute to increased hydrophilicity with a change in the asymptotic water uptake from 0.95% (neat PLA) up to 1.67% (PLA with 9 wt % HNTs) and the effect of HNTs on disintegration in controlled compost soil has been carried out to see the influence of HNTs on this process, which is a slight delay on it. These PLA-HNT composites show good balanced properties and could represent an interesting solution to develop active materials.

Thermal transient testing is widely used for LED characterization, derivation of compact models, and calibration of 3D finite element models. The traditional analysis of transient thermal measurements yields a thermal model for a single heat source. However, it appears that secondary heat sources are typically present in LED packages and significantly limit the model's precision. In this paper, we reveal inaccuracies of thermal transient measurements interpretation associated with the secondary heat sources related to the light trapped in an optical encapsulant and phosphor light conversion losses. We show that both have a significant impact on the transient response for mid-power LED packages. We present a novel methodology of a derivation and calibration of thermal models for LEDs with multiple heat sources. It can be applied not only to monochromatic LEDs but particularly also to LEDs with phosphor light conversion. The methodology enables a separate characterization of the primary pn junction thermal power source and the secondary heat sources in an LED package.

Thermal transient testing is widely used for LED characterization, derivation of compact models, and calibration of 3D finite element models. The traditional analysis of transient thermal measurements yields a thermal model for a single heat source. However, it appears that secondary heat sources are typically present in LED packages and significantly limit the model's precision. In this paper, we reveal inaccuracies of thermal transient measurements interpretation associated with the secondary heat sources related to the light trapped in an optical encapsulant and phosphor light conversion losses. We show that both have a significant impact on the transient response for mid-power LED packages. We present a novel methodology of a derivation and calibration of thermal models for LEDs with multiple heat sources. It can be applied not only to monochromatic LEDs but particularly also to LEDs with phosphor light conversion. The methodology enables a separate characterization of the primary pn junction thermal power source and the secondary heat sources in an LED package.

[EN] Each of the elements that make up the turbocharger has been gradually improved. In order to ensure that the system does not experience any mechanical failures or loss of efficiency, it is important to study which engine operating conditions could produce the highest failing rate. Common failing conditions in turbochargers are mostly achieve due to oil contamination and high temperatures in the bearing system. Thermal management becomes increasingly important for the required engine performance. Therefore, it has become necessary to have accurate temperature and heat transfer models. Most thermal design and analysis codes need data for validation; often the data available falls outside the range of conditions the engine experiences in reality leading to the need to interpolate and extrapolate disproportionately. This paper presents a fast 3D heat transfer model for computing internal temperatures in the central housing for non-water cooled turbochargers and its direct validation with experimental data at different engine operating conditions of speed and load. The presented model allows a detailed study of the temperature rise of the central housing, lubrication channels, and maximum level of temperature at different points of the bearing system of an automotive turbocharger. It will let to evaluate thermal damage done to the system itself and influences on the working fluid temperatures, which leads oil coke formation that can affect the performance of the engine. Thermal heat transfer properties obtained from this model can be used for to feed and improve a radial lumped model of heat transfer that predicts only local internal temperatures[1]. Model validation is illustrated and finally the main results are discussed.

[EN] Each of the elements that make up the turbocharger has been gradually improved. In order to ensure that the system does not experience any mechanical failures or loss of efficiency, it is important to study which engine operating conditions could produce the highest failing rate. Common failing conditions in turbochargers are mostly achieve due to oil contamination and high temperatures in the bearing system. Thermal management becomes increasingly important for the required engine performance. Therefore, it has become necessary to have accurate temperature and heat transfer models. Most thermal design and analysis codes need data for validation; often the data available falls outside the range of conditions the engine experiences in reality leading to the need to interpolate and extrapolate disproportionately. This paper presents a fast 3D heat transfer model for computing internal temperatures in the central housing for non-water cooled turbochargers and its direct validation with experimental data at different engine operating conditions of speed and load. The presented model allows a detailed study of the temperature rise of the central housing, lubrication channels, and maximum level of temperature at different points of the bearing system of an automotive turbocharger. It will let to evaluate thermal damage done to the system itself and influences on the working fluid temperatures, which leads oil coke formation that can affect the performance of the engine. Thermal heat transfer properties obtained from this model can be used for to feed and improve a radial lumped model of heat transfer that predicts only local internal temperatures[1]. Model validation is illustrated and finally the main results are discussed.

Micro and nanomechanical sensors are indispensable in modern consumer electronics, automotive and medical industries. Gas pressure sensors are currently the most widespread membrane-based micromechanical sensors. By reducing their size, their unit costs and energy consumption drops, making them more attractive for integration in new applications. Reducing the size requires the membrane to be as thin as possible, but also very strong. Graphene is the perfect material for such a membrane since it is only one atom thick but also the strongest material ever measured. This dissertation investigates the dynamics of suspended graphene membranes for sensing applications. These sensing applications are not restricted to pressure sensors alone, but the dynamics of graphene can also be used as a sensor for other physical properties. Thus, the topic of this thesis goes into the broader subject of the dynamics of interacting graphene membranes., Casimir PhD Series, Delft-Leiden 2018-39, QN/Steeneken Lab

The human eye has been the center of many studies at thermographic level, has little blood supply, which allows to demonstrate that the change of temperature in the ocular surface can be an important indicator for the diagnosis of different pathologies. In this study, a methodology was designed and implemented by means of which the influence of human lachrymal function on the ocular surface (cornea) was analyzed at thermal level, using infra-red thermography in a sample of 40 people without ocular pathologies (20 men - 20 women between 18 and 28 years of age). It is shown that the tear function has a thermal effect which can be described by the rate of decrease of the corneal temperature in the blinking exercise; it is demonstrated that this thermal effect is similar for men and women and can be converted into a quantitative type base for the study and diagnosis of ocular pathologies such as dry eye syndrome (SOS) in which the tear function is severely affected., El ojo humano ha sido el centro de numerosos estudios a nivel termográfico, tiene poca irrigación sanguínea, lo que permite demostrar que el cambio de temperatura en la superficie ocular puede ser un importante indicador para el diagnóstico de diferentes patologías. En este estudio se diseñó e implemento una metodología por medio de la cual se analizó a nivel térmico la influencia de la función lagrimal humana sobre la superficie ocular (córnea), utilizando para ello la termografía infrarroja en una muestra de 40 personas sin patologías oculares (20 hombres – 20 mujeres entre 18 y 28 años de edad). Se demuestra que la función lagrimal tiene un efecto térmico que se puede describir por la tasa de disminución de la temperatura de la córnea en el ejercicio del parpadeo; se demuestra que este efecto térmico es similar para hombres y mujeres y que se puede convertir en una base de tipo cuantitativo para el estudio y diagnóstico de patologías oculares, como el síndrome del ojo seco (SOS) en el cual la función lagrimal está gravemente afectada.

The human eye has been the center of many studies at thermographic level, has little blood supply, which allows to demonstrate that the change of temperature in the ocular surface can be an important indicator for the diagnosis of different pathologies. In this study, a methodology was designed and implemented by means of which the influence of human lachrymal function on the ocular surface (cornea) was analyzed at thermal level, using infra-red thermography in a sample of 40 people without ocular pathologies (20 men - 20 women between 18 and 28 years of age). It is shown that the tear function has a thermal effect which can be described by the rate of decrease of the corneal temperature in the blinking exercise; it is demonstrated that this thermal effect is similar for men and women and can be converted into a quantitative type base for the study and diagnosis of ocular pathologies such as dry eye syndrome (SOS) in which the tear function is severely affected., El ojo humano ha sido el centro de numerosos estudios a nivel termográfico, tiene poca irrigación sanguínea, lo que permite demostrar que el cambio de temperatura en la superficie ocular puede ser un importante indicador para el diagnóstico de diferentes patologías. En este estudio se diseñó e implemento una metodología por medio de la cual se analizó a nivel térmico la influencia de la función lagrimal humana sobre la superficie ocular (córnea), utilizando para ello la termografía infrarroja en una muestra de 40 personas sin patologías oculares (20 hombres – 20 mujeres entre 18 y 28 años de edad). Se demuestra que lafunción lagrimal tiene un efecto térmico que se puede describir por la tasa de disminución de la temperatura de la córnea en el ejercicio del parpadeo; se demuestra que este efecto térmico es similar para hombres y mujeres y que se puede convertir en una base de tipo cuantitativo para el estudio y diagnóstico depatologías oculares, como el síndrome del ojo seco (SOS) en el cual la función lagrimal está gravemente afectada.

The human eye has been the center of many studies at thermographic level, has little blood supply, which allows to demonstrate that the change of temperature in the ocular surface can be an important indicator for the diagnosis of different pathologies. In this study, a methodology was designed and implemented by means of which the influence of human lachrymal function on the ocular surface (cornea) was analyzed at thermal level, using infra-red thermography in a sample of 40 people without ocular pathologies (20 men - 20 women between 18 and 28 years of age). It is shown that the tear function has a thermal effect which can be described by the rate of decrease of the corneal temperature in the blinking exercise; it is demonstrated that this thermal effect is similar for men and women and can be converted into a quantitative type base for the study and diagnosis of ocular pathologies such as dry eye syndrome (SOS) in which the tear function is severely affected., El ojo humano ha sido el centro de numerosos estudios a nivel termográfico, tiene poca irrigación sanguínea, lo que permite demostrar que el cambio de temperatura en la superficie ocular puede ser un importante indicador para el diagnóstico de diferentes patologías. En este estudio se diseñó e implemento una metodología por medio de la cual se analizó a nivel térmico la influencia de la función lagrimal humana sobre la superficie ocular (córnea), utilizando para ello la termografía infrarroja en una muestra de 40 personas sin patologías oculares (20 hombres – 20 mujeres entre 18 y 28 años de edad). Se demuestra que lafunción lagrimal tiene un efecto térmico que se puede describir por la tasa de disminución de la temperatura de la córnea en el ejercicio del parpadeo; se demuestra que este efecto térmico es similar para hombres y mujeres y que se puede convertir en una base de tipo cuantitativo para el estudio y diagnóstico depatologías oculares, como el síndrome del ojo seco (SOS) en el cual la función lagrimal está gravemente afectada.

The human eye has been the center of many studies at thermographic level, has little blood supply, which allows to demonstrate that the change of temperature in the ocular surface can be an important indicator for the diagnosis of different pathologies. In this study, a methodology was designed and implemented by means of which the influence of human lachrymal function on the ocular surface (cornea) was analyzed at thermal level, using infra-red thermography in a sample of 40 people without ocular pathologies (20 men - 20 women between 18 and 28 years of age). It is shown that the tear function has a thermal effect which can be described by the rate of decrease of the corneal temperature in the blinking exercise; it is demonstrated that this thermal effect is similar for men and women and can be converted into a quantitative type base for the study and diagnosis of ocular pathologies such as dry eye syndrome (SOS) in which the tear function is severely affected., El ojo humano ha sido el centro de numerosos estudios a nivel termográfico, tiene poca irrigación sanguínea, lo que permite demostrar que el cambio de temperatura en la superficie ocular puede ser un importante indicador para el diagnóstico de diferentes patologías. En este estudio se diseñó e implemento una metodología por medio de la cual se analizó a nivel térmico la influencia de la función lagrimal humana sobre la superficie ocular (córnea), utilizando para ello la termografía infrarroja en una muestra de 40 personas sin patologías oculares (20 hombres – 20 mujeres entre 18 y 28 años de edad). Se demuestra que la función lagrimal tiene un efecto térmico que se puede describir por la tasa de disminución de la temperatura de la córnea en el ejercicio del parpadeo; se demuestra que este efecto térmico es similar para hombres y mujeres y que se puede convertir en una base de tipo cuantitativo para el estudio y diagnóstico de patologías oculares, como el síndrome del ojo seco (SOS) en el cual la función lagrimal está gravemente afectada.

The human eye has been the center of many studies at thermographic level, has little blood supply, which allows to demonstrate that the change of temperature in the ocular surface can be an important indicator for the diagnosis of different pathologies. In this study, a methodology was designed and implemented by means of which the influence of human lachrymal function on the ocular surface (cornea) was analyzed at thermal level, using infra-red thermography in a sample of 40 people without ocular pathologies (20 men - 20 women between 18 and 28 years of age). It is shown that the tear function has a thermal effect which can be described by the rate of decrease of the corneal temperature in the blinking exercise; it is demonstrated that this thermal effect is similar for men and women and can be converted into a quantitative type base for the study and diagnosis of ocular pathologies such as dry eye syndrome (SOS) in which the tear function is severely affected., El ojo humano ha sido el centro de numerosos estudios a nivel termográfico, tiene poca irrigación sanguínea, lo que permite demostrar que el cambio de temperatura en la superficie ocular puede ser un importante indicador para el diagnóstico de diferentes patologías. En este estudio se diseñó e implemento una metodología por medio de la cual se analizó a nivel térmico la influencia de la función lagrimal humana sobre la superficie ocular (córnea), utilizando para ello la termografía infrarroja en una muestra de 40 personas sin patologías oculares (20 hombres – 20 mujeres entre 18 y 28 años de edad). Se demuestra que lafunción lagrimal tiene un efecto térmico que se puede describir por la tasa de disminución de la temperatura de la córnea en el ejercicio del parpadeo; se demuestra que este efecto térmico es similar para hombres y mujeres y que se puede convertir en una base de tipo cuantitativo para el estudio y diagnóstico depatologías oculares, como el síndrome del ojo seco (SOS) en el cual la función lagrimal está gravemente afectada.

The human eye has been the center of many studies at thermographic level, has little blood supply, which allows to demonstrate that the change of temperature in the ocular surface can be an important indicator for the diagnosis of different pathologies. In this study, a methodology was designed and implemented by means of which the influence of human lachrymal function on the ocular surface (cornea) was analyzed at thermal level, using infra-red thermography in a sample of 40 people without ocular pathologies (20 men - 20 women between 18 and 28 years of age). It is shown that the tear function has a thermal effect which can be described by the rate of decrease of the corneal temperature in the blinking exercise; it is demonstrated that this thermal effect is similar for men and women and can be converted into a quantitative type base for the study and diagnosis of ocular pathologies such as dry eye syndrome (SOS) in which the tear function is severely affected., El ojo humano ha sido el centro de numerosos estudios a nivel termográfico, tiene poca irrigación sanguínea, lo que permite demostrar que el cambio de temperatura en la superficie ocular puede ser un importante indicador para el diagnóstico de diferentes patologías. En este estudio se diseñó e implemento una metodología por medio de la cual se analizó a nivel térmico la influencia de la función lagrimal humana sobre la superficie ocular (córnea), utilizando para ello la termografía infrarroja en una muestra de 40 personas sin patologías oculares (20 hombres – 20 mujeres entre 18 y 28 años de edad). Se demuestra que lafunción lagrimal tiene un efecto térmico que se puede describir por la tasa de disminución de la temperatura de la córnea en el ejercicio del parpadeo; se demuestra que este efecto térmico es similar para hombres y mujeres y que se puede convertir en una base de tipo cuantitativo para el estudio y diagnóstico depatologías oculares, como el síndrome del ojo seco (SOS) en el cual la función lagrimal está gravemente afectada.

Micro and nanomechanical sensors are indispensable in modern consumer electronics, automotive and medical industries. Gas pressure sensors are currently the most widespread membrane-based micromechanical sensors. By reducing their size, their unit costs and energy consumption drops, making them more attractive for integration in new applications. Reducing the size requires the membrane to be as thin as possible, but also very strong. Graphene is the perfect material for such a membrane since it is only one atom thick but also the strongest material ever measured. This dissertation investigates the dynamics of suspended graphene membranes for sensing applications. These sensing applications are not restricted to pressure sensors alone, but the dynamics of graphene can also be used as a sensor for other physical properties. Thus, the topic of this thesis goes into the broader subject of the dynamics of interacting graphene membranes., Casimir PhD Series, Delft-Leiden 2018-39, QN/Steeneken Lab

The growing use of telecommunication technologies has led the industry to develop infrastructure to support this progress. The outer telecommunications cabinets are part of the Base Transceiver Station (BTS) allowing to accommodate and protect from outer adverse conditions, a set of electronic equipment needed to operate the mobile communication network. This kind of cabinets should have a proper thermal performance to ensure indoor air temperature below 55°C to avoid exceeding the maximum operating temperature of the electronic equipment. This work describes the analysis of the thermal performance of an outdoor telecommunication cabinet (OTC) using the computational tool DesignBuilder. The simulation results are compared to the experimental data collected in real cabinet under normal operating conditions. The simulation results show that the air temperature predicted by the model is closer to the temperature measured experimentally inside the cabinet particularly when the weather data files of the computational model have a similar behavior to the actual weather data. Numerical studies show that the use of mechanical ventilation is effective in the extraction of heat generated inside the cabinet. However, there is a limit beyond which increasing the air flow rate does not result in a significant decrease of the cabinet air temperature. The studies also show the importance of the radiant properties and the geographical location of the cabinet. High values of the outer surface cabinet emissivity impair the thermal performance of the cabinet during the day and for some locations, an operational mechanical ventilation system may not be enough to maintain the indoor air temperature below 55°C. Overall, the use of DesignBuilder proved to be very effective for characterizing the thermal performance of telecommunications outdoor cabinets.

Настанак звучног таласа након осветљавања узорка модулисаним светлосним снопом назива се фотоакустички (ФА) ефекат. Теоријска истраживања предвиђају да је уз помоћ мерних техника заснованих на ФА ефекту могуће извршити одређивање карактеристика танких узорака. ФА технике нису инвазивне и због тога изазивају интересовање у разним областима науке, медицине и технике. У зависности од карактеристика које се желе проучавати, примењују се различите технике засноване на ФА ефекту. У фокусу предложеног истраживања је примена фреквенцијске ФА технике за термичку карактеризацију, док ће споредни правац истраживања разматрати могућности повезивања фреквенцијске ФА технике са ФА спектроскопијом ради симултане оптичке и термичке карактеризације. Предмет истраживања је развој ФА мерног система (ФАМС) за одређивање термичких параметара танких узорака, и то термичке дифузивности, термичке проводности и коефицијента термичког ширења. Систем се састоји од побудног дела, ФА ћелије и детекционог дела. Побудни део система чине извор светлости и модулатор светлосног снопа. Модулисани светлосни сноп погађа узорак у коме се апсорбује део светлосне енергије, што за последицу има формирање акустичког сигнала фреквенције једнаке фреквенцији модулације светлосног снопа. Генерисани акустички сигнал се детектује микрофоном, док се део светлости који се рефлектује од узорка детектује фотодетектором, па детекциони део система чине микрофон са претпојачавачем, фотодетектор, појачавачи детектованих сигнала и систем за аквизицију. У оквиру система за аквизицију се налазе аквизициона картица, lock-in детектор и рачунар. ФА ћелијом се назива затворени простор у коме се простире акустички сигнал генерисан ФА ефектом. Мада ФА ћелија може бити изведена као комора у коју се постављају узорак, микрофон и фотодетектор, чешће се узорак причвршћује директно за микрофон, тако да простор између узорка и микрофона представља ФА ћелију..., The formation of sound waves after exposition of a sample to a modulated light beam is called the photoacoustic (PA) effect. Theoretical researches predict that it is possible to determine characteristics of thin samples with the help of measurement techiques based on the PA effect. PA techniques are not invasive and for this reason cause interest in many different areas of science, medicine and technique. Depending on the characteristics to be studied, different techniques are applied based on the PA effect. In the focus of the suggested research is the application of the PA frequency technique for thermal catheterization, while the secondary direction of the research will consider possibilities of connecting the frequency PA technique with the PA spectroscopy aimed at the simultaneous optical and thermal characterization. The subject of research is the development of the PA measurement system for determination of thermal parameters of thin samples, namely thermal diffusivity, thermal conductivity and linear expansion coefficient. The system consists of an excitation part, a PA cell and a detection part. The excitation part of the system consists of a light source and a modulator of the light beam. The modulated light beam affects the sample, which absorbs a part of the light energy, and due to the PA effect, the created acoustic signal has the same frequency as the light-beam modulations. Generated acoustic signal is detected by a microphone, whereas the part of light reflected from the sample is detected by a photodetector, so the detection part of the system consists of the microphone with a preamplifier, photodetector, amplifiers of the detected signals and an acquisition system. The acquisition system includes an acquisition card, a lock-in detector and a computer. The PA cell is a closed space in which an acoustic signal is generated by the PA effect. Although a PA cell can be a chamber in which the sample, microphone and photodetector are placed, more often

Single phase microchannel cooling techniques are a promising solution to solve the problem of cooling requirements in the electronic devices and their increasing heat flux dissipation. The overall thermal resistance of the cooling solution needs to be reduced to improve the performance. The interface that attach the chip with its heat sink has a big impact on the overall thermal. Therefore a low thermal resistance interface is in focus in this work. Transient experiments and finite element models are used to characterize the interface. The heat sink is experimentally tested with different operating steady-states conditions to identify trends in its behaviour. The thermal properties of the heat sink are extracted. A comparison of the contribution of the heat sink and the interface to the total thermal resistance is made. The results show the high impact of the heat sink in the overall thermal resistance. It makes it possible to use this methodology for heat sink optimization. An error assessment study is made to analyse the accuracy of the results.

Single phase microchannel cooling techniques are a promising solution to solve the problem of cooling requirements in the electronic devices and their increasing heat flux dissipation. The overall thermal resistance of the cooling solution needs to be reduced to improve the performance. The interface that attach the chip with its heat sink has a big impact on the overall thermal. Therefore a low thermal resistance interface is in focus in this work. Transient experiments and finite element models are used to characterize the interface. The heat sink is experimentally tested with different operating steady-states conditions to identify trends in its behaviour. The thermal properties of the heat sink are extracted. A comparison of the contribution of the heat sink and the interface to the total thermal resistance is made. The results show the high impact of the heat sink in the overall thermal resistance. It makes it possible to use this methodology for heat sink optimization. An error assessment study is made to analyse the accuracy of the results.

The paper presents a study of possibilities to extend the present methodology for thermal characterization of thin solid samples by photoacoustic techniques. The present methodology consists of linear fitting of the experimental data to approximate the expressions derived from the composite piston model of photoacoustic response and it is mainly used for calculation of thermal diffusivity of thin samples. The study has shown that the methodology may be extended to calculation of thermal diffusivity, thermal conductivity and thermal expansion coefficients of thin samples by linear fitting in multiple frequency ranges and by analysis of the intersection frequency, which is the frequency where the magnitudes of two components of photoacoustic response in the composite piston model are equal. The analysis of numeric errors of the methodology has revealed the dominant sources and magnitude of the errors, leading to the conclusion that photoacoustic techniques should be carefully used as a tool for extensive thermal characterization of thin samples in the cases when other techniques are not applicable or have larger errors. (C) 2016 Elsevier Masson SAS. All rights reserved.

Thermal characterizations of high power light emitting diodes (LEDs) and laser diodes (LDs) are one of the most critical issues to achieve optimal performance such as center wavelength, spectrum, power efficiency, and reliability. Unique electrical/optical/thermal characterizations are proposed to analyze the complex thermal issues of high power LEDs and LDs. First, an advanced inverse approach, based on the transient junction temperature behavior, is proposed and implemented to quantify the resistance of the die-attach thermal interface (DTI) in high power LEDs. A hybrid analytical/numerical model is utilized to determine an approximate transient junction temperature behavior, which is governed predominantly by the resistance of the DTI. Then, an accurate value of the resistance of the DTI is determined inversely from the experimental data over the predetermined transient time domain using numerical modeling. Secondly, the effect of junction temperature on heat dissipation of high power LEDs is investigated. The theoretical aspect of junction temperature dependency of two major parameters – the forward voltage and the radiant flux – on heat dissipation is reviewed. Actual measurements of the heat dissipation over a wide range of junction temperatures are followed to quantify the effect of the parameters using commercially available LEDs. An empirical model of heat dissipation is proposed for applications in practice. Finally, a hybrid experimental/numerical method is proposed to predict the junction temperature distribution of a high power LD bar. A commercial water-cooled LD bar is used to present the proposed method. A unique experimental setup is developed and implemented to measure the average junction temperatures of the LD bar. After measuring the heat dissipation of the LD bar, the effective heat transfer coefficient of the cooling system is determined inversely. The characterized properties are used to predict the junction temperature distribution over the

The paper presents a study of possibilities to extend the present methodology for thermal characterization of thin solid samples by photoacoustic techniques. The present methodology consists of linear fitting of the experimental data to approximate the expressions derived from the composite piston model of photoacoustic response and it is mainly used for calculation of thermal diffusivity of thin samples. The study has shown that the methodology may be extended to calculation of thermal diffusivity, thermal conductivity and thermal expansion coefficients of thin samples by linear fitting in multiple frequency ranges and by analysis of the intersection frequency, which is the frequency where the magnitudes of two components of photoacoustic response in the composite piston model are equal. The analysis of numeric errors of the methodology has revealed the dominant sources and magnitude of the errors, leading to the conclusion that photoacoustic techniques should be carefully used as a tool for extensive thermal characterization of thin samples in the cases when other techniques are not applicable or have larger errors. (C) 2016 Elsevier Masson SAS. All rights reserved.

Crystalline powder aggregates of a new nickel coordination polymer with 2-carboxyethylphosphonic acid (HPPAH) and 4,4′-bipyridine, Ni(HPPA)(4,4′-bipy)(HO), has been obtained by hydrothermal synthesis, and their crystal structure has been ab initio determined from synchrotron powder data. The compound shows a layer structure in bc plane, with Ni atoms in two different environments. The loss of the coordinated water by heating leads to the apparition of an anhydrous phase, which remains stable when cooling down to room temperature. Synthesized material presents a paramagnetic behaviour with weak antiferromagnetic interactions and zero-field splitting at low temperature (T < 50 K).

[EN] Recovery of recycled acrylonitrile butadiene styrene (ABS) through mixing with styrene-ethylene/butylene-styrene (SEBS) has been studied in this paper. To simulate recycled ABS, virgin ABS was processed through 5 cycles, at extreme processing temperatures, 220 degrees C and 260 degrees C. The virgin ABS, the virgin SEBS, the recycled ABS and the mixtures were mechanically and thermally characterized after the various cycles of reprocessing in order to evaluate their corresponding properties and correlate them with the number of cycles undergone. The results show that tensile strength of ABS remains practically constant as the number of reprocessing cycles increases, while in the material injected with SEBS the tensile strength decreases. Concerning the Charpy notched impact strength, the values of the ABS reprocessed at 220 degrees C remain more or less unchanged, while the values for 260 degrees C show a significant decrease. The adhesion of the SEBS causes, in both cases, an increase in impact strength. DSC techniques enabled us to observe how the glass transition temperature (Tg) remains more or less constant regardless of the number of cycles or the temperature, whereas the crosslinking is much greater in the samples reprocessed at 260 degrees C. As conclusion, it is suggested that the people who works handling and dealing with plastic that, when possible, use low temperatures of transformation of ABS instead of high temperatures. It is also recommended to recycle the ABS to those who work with it; to use 5% of SEBS added to the recycled ABS to recover the possible loss of properties., [ES] En este trabajo se estudia la recuperación de un Acrilonitrilo-Butadieno-Estireno (ABS) reciclado mediante mezcla con Estireno-Etileno/ Butadieno-Estireno (SEBS). Para simular el ABS reciclado se ha reprocesado ABS virgen durante cinco ciclos a las dos temperaturas extremas de procesamiento, 220ºC y 260ºC. Los materiales ABS virgen, SEBS virgen, ABS reprocesado y las mezclas han sido caracterizados mecánica y térmicamente para evaluar sus propiedades correspondientes y correlacionarlo con el número de ciclos de proceso. Los resultados muestran que la resistencia a tracción del ABS se mantiene prácticamente constante conforme aumenta el número de ciclos de reprocesado, en cambio, disminuye al aditivarlo con SEBS. Con respecto a la resistencia al impacto, los valores del ABS reprocesado a 220ºC permanecen prácticamente inalterables, mientras que para el reprocesado a 260ºC disminuyen de forma notable. La adhesión de SEBS provoca, en ambos casos, un incremento de energía de impacto. Las técnicas de DSC han permitido observar como la temperatura de transición vítrea se mantiene prácticamente constante independientemente del número de ciclos o de la temperatura; en cambio, el efecto de entrecruzamiento de las moléculas (crosslinking) es mucho mayor para las muestra reprocesadas a 260ºC. Como conclusión, se recomienda a los transformadores de plástico que, en lo posible, utilicen temperaturas de transformación del ABS bajas en vez de altas. También se recomienda a los transformadores que recuperen ABS, que utilicen un 5% de SEBS para mejorar las propiedades.

[EN] Recovery of recycled acrylonitrile butadiene styrene (ABS) through mixing with styrene-ethylene/butylene-styrene (SEBS) has been studied in this paper. To simulate recycled ABS, virgin ABS was processed through 5 cycles, at extreme processing temperatures, 220 degrees C and 260 degrees C. The virgin ABS, the virgin SEBS, the recycled ABS and the mixtures were mechanically and thermally characterized after the various cycles of reprocessing in order to evaluate their corresponding properties and correlate them with the number of cycles undergone. The results show that tensile strength of ABS remains practically constant as the number of reprocessing cycles increases, while in the material injected with SEBS the tensile strength decreases. Concerning the Charpy notched impact strength, the values of the ABS reprocessed at 220 degrees C remain more or less unchanged, while the values for 260 degrees C show a significant decrease. The adhesion of the SEBS causes, in both cases, an increase in impact strength. DSC techniques enabled us to observe how the glass transition temperature (Tg) remains more or less constant regardless of the number of cycles or the temperature, whereas the crosslinking is much greater in the samples reprocessed at 260 degrees C. As conclusion, it is suggested that the people who works handling and dealing with plastic that, when possible, use low temperatures of transformation of ABS instead of high temperatures. It is also recommended to recycle the ABS to those who work with it; to use 5% of SEBS added to the recycled ABS to recover the possible loss of properties., [ES] En este trabajo se estudia la recuperación de un Acrilonitrilo-Butadieno-Estireno (ABS) reciclado mediante mezcla con Estireno-Etileno/ Butadieno-Estireno (SEBS). Para simular el ABS reciclado se ha reprocesado ABS virgen durante cinco ciclos a las dos temperaturas extremas de procesamiento, 220ºC y 260ºC. Los materiales ABS virgen, SEBS virgen, ABS reprocesado y las mezclas han sido caracterizados mecánica y térmicamente para evaluar sus propiedades correspondientes y correlacionarlo con el número de ciclos de proceso. Los resultados muestran que la resistencia a tracción del ABS se mantiene prácticamente constante conforme aumenta el número de ciclos de reprocesado, en cambio, disminuye al aditivarlo con SEBS. Con respecto a la resistencia al impacto, los valores del ABS reprocesado a 220ºC permanecen prácticamente inalterables, mientras que para el reprocesado a 260ºC disminuyen de forma notable. La adhesión de SEBS provoca, en ambos casos, un incremento de energía de impacto. Las técnicas de DSC han permitido observar como la temperatura de transición vítrea se mantiene prácticamente constante independientemente del número de ciclos o de la temperatura; en cambio, el efecto de entrecruzamiento de las moléculas (crosslinking) es mucho mayor para las muestra reprocesadas a 260ºC. Como conclusión, se recomienda a los transformadores de plástico que, en lo posible, utilicen temperaturas de transformación del ABS bajas en vez de altas. También se recomienda a los transformadores que recuperen ABS, que utilicen un 5% de SEBS para mejorar las propiedades.