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Polylactic acid/chitosan (PLA/CS) and poly(vinyl alcohol)/chitosan (PVA/CS) are considered potential blends for use in tissue engineering, since when obtained in the form of 3D fibers they can form structures with high porosity, biocompatibility, antimicrobial activity and morphology similar to tissues and organs. However, there is a scarce number of reports in the literature addressing the production of systems based on 3D fibrous mixtures of PVA or PLA with high chitosan amount because of the difficulty in spinning CS into stable structures using acidic solutions, and without further employment of cross-linking agents. Therefore, this work focused on a novel procedure to prepare 3D fibrous structures of PVA and PLA with high chitosan content, combining the solution blow spinning technique, a heated air environment and the use of eco-friendly solvents, without using crosslinking agents. The influence of CS incorporation on the as-prepared structures was assessed by scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, contact angle measurement, porosity, swelling and degradation tests. Rheological tests evidenced that an increase in the CS content implies a greater viscosity of the spinning solutions, hindering the fibrillar structures formation. Fibers produced showed a randomly interconnected and highly porous fibrous cotton-wool-like structure, with fiber diameters ranging from 481 to 637 nm for PVA/CS systems, and from 1276 to 2050 nm for PLA/CS systems. A decrease in the thermal stability of the blend-based fibers and an increase in hydrophilicity, porosity, swelling and in vitro biodegradation were observed in the blend systems. Results indicate that the obtained fibrillar structures possess morphological and physical characteristics that may be interesting for application as 3D fibrous scaffolds in tissue engineering. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) boosted its technological applications because of its piezoelectric and pyroelectric properties, together with mechanical, chemical, and thermal resistance. In this review, we address the PVDF chemical structure and its synthesis procedure, also describing the occurrence of polymorphism (alpha (α), beta (β), gamma (γ), and delta (δ) of this semicrystalline polymer, and the processes involved in phase transformation that govern the adaptability of the PVDF crystalline phases and properties for several industrial uses. It can be used as a component of implants and sutures, as engineering plastic to play a structural role in aggressive environments, acting in the field of process control as a component of transducers and sensors, as well as in the synthesis of separation membranes, fuel cells, and a long list of new applications that include an important role in robotics. The main physicochemical techniques used for PVDF characterization, i.e., differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, that highlight its unique properties, are also discussed, showing the versatility of PVDF for a range of biomedical and pharmaceutical applications. [ABSTRACT FROM AUTHOR]

The polyacrylonitrile multifilament yarn underwent a multistep heat treatment process including stabilization times ranging from 5 to 75 min following impregnation with a 30% ethylenediamine (EDA) aqueous solution. A series of measurements were employed to determine the structure and properties of thermally stabilized PAN samples. These included fiber thickness, fiber density, flame testing, tensile testing, X-ray diffraction, thermal analysis (differential scanning calorimetry and thermogravimetric analysis), and infrared spectroscopy. The results from XRD and IR spectroscopy indicated that the rate of aromatization reactions increased with longer stabilization times. A detailed examination of the XRD curves obtained through curve-fitting procedures suggested a rapid transformation of the original structure into a disordered amorphous phase containing pre-graphitic domains, evidenced by a gradual reduction in the degree of apparent crystallinity of the original PAN sample. The integration of EDA before the thermal stabilization stage significantly reduced the cyclization time of nitrile groups in the PAN polymer structure, thereby accelerating the stabilization reactions. This chemical pretreatment also improved the thermal stability of the samples by promoting oxidative cross-linking of the PAN polymer chains. After a 75 min multistep stabilization, the carbon yield at 1000 °C was 70.5%. Conversion index values, calculated using IR, XRD, and DSC methods, were 98.3%, 94.8%, and 89.5% respectively for the 75 min sample. These findings highlight the importance of EDA in accelerating the formation of an aromatic structure, which is critical for withstanding the high temperatures of subsequent carbonization stages. [ABSTRACT FROM AUTHOR]

Two series based on poly(propylene 2,5-furandicarboxylate)-block-poly(tetramethylene oxide) (PPF-b-F-PTMO) containing carbon and mineral nanofillers that differ in shape (1D and 2D) were synthesized via in situ polymerization. The influence of the addition of the 1D-type nanoparticle, i.e., carbon nanofibers (CNFs) and halloysite nanotubes (HNTs), and the so-called 2D-type, i.e., graphene nanoplatelets (GNPs) and organoclay (C20A), on the properties of a biobased block copolymer was analyzed. The dispersion of nanoadditives in the nanocomposites was determined using a scanning electron microscope (SEM). The thermal properties were studied employing differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The introduction of nanoparticles increased the crystallinity (Xc) and the mean values of tensile modulus (E) of the bionanocomposites. In turn, one observed that the decrease in the limited viscosity number (LVN) was visible along with incorporating nanoadditives. The synthesized polymer bionanocomposites reveal the mechanical properties of elastomers during mechanical testing. Moreover, the good processability of the obtained materials by injection molding combined with the comprehensive ability to change mechanical and thermal properties of PPF-b-F-PTMO by tailoring the type and content of the nanofillers can indicate their possible applications in packaging, automotive, sports, construction, and many other industries. [ABSTRACT FROM AUTHOR]

This article investigates the thermal, mechanical, and shape memory performances of 3D-printed polylactic acid (PLA), polyethylene terephthalate glycol (PETG), and their blends for potential applications in 4D printing. Differential Scanning Calorimetry reveals distinct glass transition temperatures for PLA-PETG blends, confirming their immiscibility. The integration of PETG alters the crystalline structure of PLA, shifting its behavior from brittle to ductile. This confirms PETG's function as an effective plasticizer. The tensile strength and Young's modulus are influenced by material composition and printing orientation. The results show that 75% PLA and 25% PETG blend demonstrated enhanced mechanical properties compared to other polymer blends. Shape memory experiments demonstrate exceptional fixity and recovery rates, reaching 100%, with the 75% PLA blend exhibiting outstanding performance across 15 cycles. These findings, coupled with insights into the impact of programming temperature, offer valuable perspectives for designing 4D-printed structures with shape memory attributes, unlocking innovative applications across diverse fields. [ABSTRACT FROM AUTHOR]

This study employed reactive extrusion to produce micro-composites of high-density polyethylene (HDPE) with different fractions of diatomaceous earth, both unmodified and modified, using a novel reversible crosslinking reaction agent (RXR) consisting of a combination of sulfur, organic peroxide, and an accelerator. The rheological behavior and crosslinking response of the system were measured using dynamic rheological analysis using a torque rheometer. The mechanical characteristics of the system were evaluated through tensile and impact tests. The thermal characteristics were analyzed using differential scanning calorimetry and thermogravimetric analysis, while the structural and morphological properties were analyzed using wide-angle X-ray scattering, Fourier infrared transform, and scanning electron microscope. The mechanical properties of the HDPE resin were diminished by the inclusion of the diatomaceous earth due to aggregation and inadequate interfacial connections, whereas the thermal stability remained unaffected. Furthermore, the presence of diatomaceous earth led to enhancements in both crystallinity and lamellar thickness. The addition of the RXR agent improved the tensile and impacts strengths, caused by the crosslinking reaction. However, it had a detrimental effect on the degree of crystallinity and the size of the crystals formed. Analysis of mechanical, rheological, and crystallization properties demonstrated that the incorporation of diatomaceous earth and the diatomaceous earth-RXR agent combination showed potential as additives for HDPE. [ABSTRACT FROM AUTHOR]

Herein, the nanofibrillated poly(butylene succinate)/polytetrafluoroethylene (PBS/PTFE) composites were prepared. The relaxation time was prolonged by PTFE fibrils, resulting in an enhancement in storage modulus and melt viscosity. Differential scanning calorimetry was used to study the non-isothermal crystallization kinetics at different cooling rates. These results showed that PTFE fibrils could promote crystallization nucleation and excessive fibrils could inhibit crystallization growth. Lightweight PBS/PTFE composite foams were fabricated using core-back foam injection molding. Loading the PTFE fibrils increased the cell density of PBS foam from 2.7×106 to 1.4×108 cells/cm3 and improved the cell morphology of PBS foam. By controlling the foaming parameter, the tensile properties of PBS-based composite foam with 1 wt.% PTFE were improved overall, and the Izod impact strength was increased by 9–69% compared with the PBS foam. [ABSTRACT FROM AUTHOR]

Sustainable polymer composites (or biocomposites) based on renewable and green polymers are progressively under development in a technological paradigm shift from "just use more and more" to "convert into value-added products". Therefore, significant efforts should focus not only on their reduced environmental impact but also on maximizing their performance and broadening their application range. Herein, the bio-based blends based on Mater-Bi bio-plastic and poly(ε-caprolactone), at a weight ratio of 70:30, were developed, followed by the addition of UFC100 cellulose filler to yield sustainable biocomposites. The effects of cellulose chemical modification with three diisocyanates, i.e., hexamethylene diisocyanate (HDI), methylene diphenyl isocyanate (MDI), or toluene diisocyanate (TDI) on the surface properties of biocomposites were evaluated by water contact angle and surface roughness detected by atomic force microscopy (AFM). Biocomposites containing cellulose modified with HDI, MDI, or TDI revealed contact angle values of 93.5°, 97.7°, and 92.4°, respectively, compared to 88.5° for reference blend, indicating an enlarged hydrophobicity window. This action was further confirmed by increased fracture surface roughness and miscibility detected by microscopic observation (scanning electron microscopy (SEM) and AFM). An in-depth oscillatory rheological evaluation has identified MDI, followed by TDI, as the most efficient compatibilizer of the analyzed system. Correspondingly, thermogravimetric analysis and differential scanning calorimetry analyses showed more residue and higher melting temperatures for biocomposites, more promisingly with MDI and TDI modifiers. In conclusion, either incorporation or diisocyanate modification of cellulose affects both surface and bulk properties, providing vital insights into future developments in the field. Proper selection of diisocyanate modifier of cellulose may enable engineering of composites performance. [ABSTRACT FROM AUTHOR]

To address the issue of low mechanical strength in self-supported hollow fiber membranes, a research study was conducted to fabricate polysulfone braid-reinforced hollow fiber (PSF BRHF) membranes for natural gas purification. In this study, polyethylene (PET) was used as a braid support. PSF BRHF membranes were fabricated by employing dip coating and drying technique. The BRHF membranes underwent comprehensive analysis, including the manipulation of polymer (PSF) concentration (15 wt%, 18 wt%, and 21 wt%) and the number of coating layers (1–4). Characterization of the fabricated membrane samples involved scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gas separation performance testing, and mechanical strength testing. The results indicated that membranes fabricated with higher polymer concentrations exhibited a denser structure with a thicker separation layer. An increase in the separation layer thickness was also observed with an increasing number of coating layers. Importantly, all fabricated membrane samples demonstrated remarkable thermal stability. To assess the performance, gas separation tests were conducted using pure gases at 3 bar. Notably, the membrane sample with 21 wt% PSF and the 3rd coating layer (21_3 PSF) exhibited the most promising gas separation performance among all the samples selected to carry out the separation performance test, achieving a CO2/CH4 selectivity of 1.83. Mechanical strength testing revealed that 21_3 PSF BRHF (68.2 MPa) fabricated in this study outperformed conventional self-supported PSF hollow fiber membranes (9.44 MPa), as reported in the literature. These findings underscore the potential of BRHF membranes for natural gas purification, although further improvements are still possible. [ABSTRACT FROM AUTHOR]

The continuous development of new wound dressing materials is necessary in order to achieve the best skin tissue regeneration properties. In this research, renewable foams, based on thermoplastic polyurethane (TPU) blended with polylactic acid (PLA), with and without 5 wt.% zinc oxide (ZnO) nanofiller were fabricated, and their biocompatibility with fibroblast cells was evaluated. The composites were prepared by thermally induced phase separation method (TIPS) for wound dressing application. These porous materials were structurally and thermally characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform spectroscopy (FTIR). The materials were also tested for their water uptake ability, hydrophilic/hydrophobic properties and water vapor transmission rate (WVTR). The fibroblasts presented a good interaction with these foams by adhering to the materials surface, pointing out that a higher content of TPU is favorable for cell viability. Moreover, no toxic effects of these novel materials were detected. The antibacterial tests showed proper antibacterial properties against Staphylococcus aureus and Pseudomonas aeruginosa. Thus, blending TPU foams with PLA could be validated as biocompatible platforms, suitable for wound dressing application. [ABSTRACT FROM AUTHOR]

Tremolite asbestos is classified as a carcinogenic substance because it can cause a number of diseases when inhaled. The tremolite breakdown temperature reported in the literature varies by about 280 °C and has not been fully characterized from a thermal perspective. In order to address this gap in the scientific literature, a systematic study of the thermal behavior was conducted of twelve tremolite samples using thermogravimetric and differential scanning calorimetry (TG/DSC) supplemented by PXRD, SEM/EDS, EPMA/EDS and TEM/EDS. Tremolite samples from different locations (i.e., Italy, Switzerland and USA) were selected for their social, health, economic and industrial relevance. Data reveal that the breakdown of tremolite occurs in a temperature range of about 200 °C. The implications of this finding are discussed in light of chemical and morphological data. Variations in the breakdown temperature are mainly ascribed to the morphology of the studied tremolite samples. This study suggests that thermal analysis could be a new method for effectively distinguishing between asbestos and non-asbestos tremolite samples. The thermal oxidation of iron in the various tremolite samples occurs at different temperatures, and hence reduction of tremolite reactivity through the thermal oxidation of iron should be planned on a sample-by-sample basis. Given the different temperatures recorded for tremolite breakdown, the effectively detecting the presence of tremolite in bulk natural samples by thermal analysis can only be carried out if a thermogram of that specific sample is available. This is an important issue, especially in areas with a natural occurrence of asbestos outcrops. [ABSTRACT FROM AUTHOR]

Waterborne polyurethane (WBPUR) aerogels using acetone method and freeze-drying procedure have been successfully synthesized. The morphology, chemical structure, and thermal and mechanical properties of obtained aerogels were analysed by means of scanning electron microscopy, Fourier-transform infrared spectroscopy, contact angle, thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis. In addition, the influence of the solids content in the hydrogel (2–15 wt.%), obtained by varying the amount of water added in the suspension, on the density and thermal conductivity was evaluated. Obtained results demonstrated that the properties of aerogels strongly depend on the solids content assayed in the parent solution. As the solids content in the WBPUR aerogels increases, the density and thermal conductivity for materials with 2.5 and 10% solids content follow an upward trend, while their elasticity decreases. Materials with solids content below 2.5% and above 10% have not demonstrated adequate processability due to their high deformity and hardness, respectively. The drying methodology (freeze-drying) can be profitably used to prepare aerogels-like materials in a cost-effective way. Illustration of the alternative preparation process of WBPUR aerogels and its potential industrial application. [ABSTRACT FROM AUTHOR]

Paraffin and Silica (SiO2)-based encapsulated phase change materials (ePCMs) were synthesized to enhance thermal and phase change performance. Nano-encapsulation of paraffin by SiO2 shell was accomplished via the sol–gel method using the triethoxymethylsilane precursor. Fifteen different samples of ePCMs were synthesized and analyzed for their varied core/shell mass ratio and thermal properties. Additionally, these ePCMs were characterized using X-Ray diffraction (XRD), Fourier transform infrared spectrophotometer (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive X-ray (EDX), and dynamic light scattering (DLS). The synthesis procedures were verified to properly encapsulate paraffin inside the silica shell with varying degrees of reaction efficacy as documented in this work. The maximum effective latent heat of melting and solidification for the ePCMs was got to be 115.07 J/g and 114.19 J/g. The best-performing sample reached an encapsulation ratio of 81.8% which also successfully completed shell leakage testing after melting/freezing cycles. Latent heat and temperature values remained unaffected after 100 melting/freezing cycles confirmed by differential scanning calorimetry (DSC). [ABSTRACT FROM AUTHOR]

Softwood lignin nanoparticles (SLNs) and microparticles (SLMs) were incorporated as bio-additives into poly(L-lactic acid) (PLLA) composite films, and crystallization behaviors were compared with neat PLLA film using polarized optical microscopy (POM), differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) techniques. The Avrami and Hoffman secondary nucleation theory as well as the Hoffman-Weeks plot were used to determine key information of crystallization behavior. Non-isothermal crystallization results showed an increase in crystallinity (%Xc) of PLLA by 7% and 9% when incorporating a small amount (1.0 wt.%) of SLMs and SLNs, respectively. Spherulite number (N), crystallization rate (G) and final degree of crystallinity ( ϕ ∞ ) of neat PLLA film were 4, 0.05 min−1 and 0.48, respectively. These values increased to 116, 0.12 min−1 and 0.52, respectively, when 1.0 wt.% of SLNs was added into PLLA (1%SLNs/PLLA). A Hoffman-Weeks plot was used to examine the equilibrium melting temperature ( T m 0 ), while energy required for nuclei formation (Kg) and free energy on lamellar surface ( σ e ) values were evaluated. Kg and σ e values of neat PLLA film were 3.01 × 10−5 K2 and 6.31 × 10−12 J m−2, respectively, and significantly decreased to 2.89 × 10−5 K2 and 6.05 × 10−12 J m−2 when incorporating 1 wt.% of SLMs. Lowest Kg and σ e values of 2.72 × 10−5 K2 and 5.65 × 10−12 J m−2 were recorded in 1%SLNs/PLLA composite film. Results confirmed lignin nanoparticles (SLNs) as an alternative promising bio-additive for enhancing PLLA crystallizability toward the development of fully biobased and biodegradable plastic. [ABSTRACT FROM AUTHOR]

Poly(butylene succinate-co-terephthalate) is a biodegradable polymer with good biodegradability, high flexibility and toughness. However, its relatively low modulus, low yield strength and low heat distortion temperature limit its applicability. Herein, equimolar poly(L-lactic acid) (PLLA) and poly(D-lactide acid) (PDLA) were blended with PBST to form stereocomplex poly(lactic acid) (sc-PLA) in situ during melt blending process and prepare a novel and environmentally friendly PBST/sc-PLA blend. Differential scanning calorimetry and wide-angle X-ray diffraction confirmed that sc-PLA had formed in PBST matrix. The morphology of the cryo-fractured surfaces of PBST/sc-PLA blends showed that the sc-PLA was uniformly dispersed in PBST matrix. When the content of sc-PLA is up to 20 wt%, the PBST/sc-PLA blends showed a solid-like flow behavior at the low-frequency region. Moreover, sc-PLA could reinforce the PBST matrix. Young's modulus, yield strength and storage modulus of the PBST/sc-PLA blend increased with increasing sc-PLA content. In addition, the Vicat softening temperature and heat deflection temperatures of PBST/sc-PLA blends increased with the incorporation of sc-PLA, which enhanced the heat resistance. Compared with neat PBST, the hydrolytic degradation of the PBST/sc-PLA blends was improved. This work provides an effective way to obtain high performance PBST materials which could expand the application of PBST. [ABSTRACT FROM AUTHOR]

In this paper, the anti-aging properties of composites doped with nano and micro BiFeO3 and treated with different magnetic fields were studied by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and broadband dielectric spectroscopy. SEM results showed that thermal aging had a significant effect on LDPE and composites, and the effect of magnetization treatment on the structure was significantly weakened. FTIR results showed that with the increase in aging time, the carbonyl content increased, the carbonyl content of nanocomposites increased less, and the carbonyl content of micron composites increased gently. DSC results showed that the addition of BiFeO3 acted as heterogeneous nucleation agent, and the orientation of magnetic field changed the arrangement of molecular chain and improved the crystallinity of the composite. Compared with the aged LDPE, the aged composite had lower dielectric constant and loss factor. 0.2 wt% nano and micro BiFeO3/LDPE composites had significant anti-aging ability, and the dielectric constant and loss factor of the composites could be further reduced by magnetic field treatment. All the test results showed that the doping of BiFeO3 and magnetic field treatment could change the internal structure of the composite, increase the compactness of the material, and make the composite have obvious thermal aging resistance. [ABSTRACT FROM AUTHOR]

Complementary analytical approaches were employed to probe the effect of grain size on thermally induced oxidation of zirconium carbide (ZrC) utilizing thermogravimetric analysis, differential scanning calorimetry, and Raman spectroscopy, as well as synchrotron-based and laboratory-based X-ray diffraction (XRD) experiments. The oxidation mechanism and phase behavior of nanocrystalline ZrC (grain size ~ 20 nm) were compared with that of the more documented microcrystalline ZrC (grain size ~ 1 µm). Synchrotron XRD at the Advanced Photon Source with a hydrothermal diamond anvil cell (HDAC) used as a sample chamber revealed that the onset of oxidation is at ~ 380 °C for microcrystalline ZrC which is in agreement with previous work. In contrast, the critical oxidation temperature was ~ 330 °C for nanocrystalline ZrC. Additional high-temperature synchrotron XRD experiments at the National Synchrotron Light Source II using a lamp furnace in combination with Raman analysis showed that tetragonal ZrO2 forms as an initial oxidation product and transforms at higher temperatures to the monoclinic phase. Thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) confirmed the X-ray results of a lower critical oxidation temperature for the nanocrystalline sample. The phase transformations in the oxide phase with associated critical temperatures were also evident in the thermodynamic data as exothermic heat events. [ABSTRACT FROM AUTHOR]

In this study, Fe75Si12Ti6B7 and Fe73Si15Ti5B7 (wt. %) alloy powders were synthesized from pure elemental powders by a mechanical alloying (MA) method under argon atmosphere. The evolution in particles morphology, chemical composition, crystalline structure, magnetic and hyperfine proprieties of the mixture elements during MA(0–80 h) was investigated by scanning electron microscopy attached with energy-dispersive spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometer and Mössbauer spectroscopy (MS). The Rietveld refinement of the XRD pattern of the samples milled 5 h shows the formation of several structures: Fe3Si, α-Fe nanostructured, Fe2Ti and Fe2B, in addition, that the structure became much more amorphous together with increasing milling time at 80 h. The thermal stability of powders milled was characterized by differential scanning calorimetry (DSC). The annealing of samples milled 80 h shows that the crystallization of the amorphous phases and the activation energy determined by using Kissinger's equation was 462.23 ± 16.11 kJ mol−1 and 798.43 ± 16.12 kJ mol−1 for the Fe73Si15Ti5B7 and Fe75Si12Ti6B7, respectively. Moreover, the results from XRD and DSC for 80 h of milling were approved by the Mössbauer spectroscopy, and the spectra revealed that the sample Fe73Si15Ti5B7 is fully amorphous, but the sample Fe75Si12Ti6B7 still contains some of Fe with a 2.8% fraction non- detected by XRD. The saturation magnetization (Ms) and coercivity values were of about 151 emu/g, 38.5 G for Fe73Si15Ti5B7 and 171.6 emu/g, 35 G for Fe75Si12Ti6B7, respectively, after 80 h of milling. [ABSTRACT FROM AUTHOR]

Metal–organic polymer CuBTC and composite with CuBTC and activated carbon (CuBTC/C) were prepared by hydrothermal method (BTC3− is a linker 1,3,5-benzenetricarboxylate ion, hydrolysis temperature 130 °C, ethanol + H2O in equal proportion as a solvent) and detailed characterized by a set of methods (X-ray diffraction—XRD, X-ray absorption spectroscopy—XAS, differential scanning calorimetry—DSC, scanning electron microscopy—SEM, low-temperature sorption capacity of samples to nitrogen—BET, X-ray photoelectron spectroscopy—XPS, FTIR-spectroscopy). According to XRD and XAS data, it was found that the composition of main phase CuBTC is [Cu3BTC2(H2O)3] × (nH2O + mC2H5OH) in both samples. The catalytic properties of CuBTC and CuBTC/C samples in the reaction of ethanol dehydrogenation were studied for the first time and the selectivity to acetaldehyde (AcH) was 100% in both cases. It was shown that on the CuBTC/C catalysis, the AcH yield is two times higher than on the CuBTC sample in the reaction of ethanol (Lewis base) dehydrogenation to acetaldehyde. This fact can be explained by the higher content of main phase CuBTC in composite CuBTC/C (~ 97.5 wt%) and the Cu2+ ions (Lewis acid sites) in bulk, the higher water and Cu2+ ions content on the particle surface in CuBTC/C (DSC, FTIR, XPS), the larger pore radii in CuBTC framework of the composite CuBTC/C (according to crystallochemical calculations) and the larger hydrogenation degree of CuBTC/C (XRD, DSC, FTIR) and the smaller specific surface area of CuBTC/C (SBET = 44.4 m2/g for CuBTC/C sample and SBET = 551.3 m2/g for CuBTC). It was found that in the reaction of propane conversion to ethylene C2H4 and methane CH4, the conversion degree on the samples CuBTC and CuBTC/C was the same from 100 °C up to 340 °C, which is caused by the absence of the Bronsted acid sites on the samples with CuBTC. [ABSTRACT FROM AUTHOR]

Integrating energetic materials with microelectromechanical systems (MEMS) to realize miniaturized energetic chips has shown broad application prospects in micro-spacecraft, micro-satellites, ballistic correction munitions, and smart munitions. In this work, a new type of MEMS compatible Cu/ICM-101 energetic film was successfully fabricated on copper substrates by in-situ electrochemical synthesis, the morphology and ignition property of which can be effectively controlled by adjusting the voltage and electrochemical deposition time. The morphology, composition, thermal properties, and ignition performance of as-prepared Cu/ICM-101 films were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and pulsed laser. The results show that the as-prepared Cu/ICM-101 films possesses nano porous framework structure with an exothermic heat of 1800.9 J·g−1 and a thermal decomposition peak temperature of 256.4 °C. In addition, the flame height and ignition duration of which reach 10 mm and 300 μs, respectively. This work provides a reference for the integration and application of energetic materials in MEMS systems. [ABSTRACT FROM AUTHOR]

Decomposition and precipitation processes in a binary Al–Li alloy and a technical Al–Li–Cu–Mg alloy were investigated using differential scanning calorimetry and X-ray Raman spectroscopy (XRS). The formation of δ ' and T1 precipitates in the Al–Li and the T8 heat-treated Al–Li–Cu–Mg alloy, respectively, was confirmed using DSC. The XRS measurements complemented by simulated spectra allowed for probing specifically Li and its environment within the Al matrix. Based on linear combination fits of the XRS spectra, the relative contributions of δ ′ and T1 precipitates were quantified. These results are in agreement with estimates of the relative amount of Li taking part in the precipitation process. Difficulties and limitations of the application of XRS to Al alloy systems are also discussed. [ABSTRACT FROM AUTHOR]

In the present work, polyvinylpyrrolidone (PVP)-assisted bismuth telluride (Bi2Te3) fibers were synthesized by electrospinning technique. These fibers were then compacted at a very slow rate at a constant temperature of 283 K. The as-prepared and compacted fibers were structurally and morphologically characterized via X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Thermogravimetric analysis (TGA) along with differential scanning calorimetry (DSC) were also carried out up to 800 K for the thermal analysis of the as-prepared and compacted composite fibers. Thermoelectric characterizations (Seebeck coefficient, electrical conductivity and thermal conductivity) along with diffusive reflectance spectroscopy (DRS) were performed to study the thermoelectric properties and optical properties of the as-synthesized and compacted electrospun fibers. High Seebeck coefficient value of 3062µVK−1 and an ultra-low thermal conductivity value of 0.5 Wm−1 K−1 have been observed for the fibers at room temperature. The compacted samples have shown much better thermoelectric performance, and their zT increased significantly from 10−12 to 10−2 due to the compaction. [ABSTRACT FROM AUTHOR]

The oxidative thermal stability of plant-based microcrystalline flax fiber was developed by incorporating diammonium phosphate (DAP), boric acid, and urea (in brief DAP-BAU) followed by a multistep thermal oxidation process. By utilizing a set of measurements, including X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy analysis, the impact of DAP-BAU inclusion on the thermal stability of flax fibers was studied. The findings of IR spectra and X-ray diffraction analysis revealed that the dehydrogenation and dehydration processes cause a progressive and steady loss of inter- and intramolecular H-bondings. Infrared spectra also showed the development of C = C double bonds associated with the crosslinked ladder structure formation. DSC and TGA findings revealed that DAP-BAU incorporation boosted thermal stability by generating ladder-like structure formation and restricted the development of volatile by-products by inhibiting the fundamental hydroxyl groups with increasing oxidation time. The overall findings of this study confirm that DAP-BAU incorporated and 125 min stabilized (at 245 °C) flax fibers attain complete thermal stability and are ready for utilizing in the subsequent carbonization and activation stages in activated carbon fiber manufacturing. [ABSTRACT FROM AUTHOR]

Both Sn addition and pre-ageing are known to be effective in maintaining the artificial ageing potential after natural ageing of Al–Mg–Si alloys. In this study, the combined effects of Sn addition and pre-ageing at 100 °C or 180 °C on natural secondary ageing and subsequent artificial ageing of an alloy AA6014 were investigated using hardness, electrical resistivity, differential scanning calorimetry and transmission electron microscopy characterizations. It is found that pre-ageing can suppress natural secondary ageing and improve the artificial ageing hardening kinetics and response after 1 week of natural secondary ageing in both alloys with and without Sn addition. The effect of pre-ageing at 100 °C is more pronounced in the Sn-free alloy while the combination of pre-ageing at 180 °C and adding Sn shows superiority in suppressing natural secondary ageing and thus avoiding the undesired hardening before artificial ageing. Moreover, when natural ageing steps up to 8 h are applied before pre-ageing at 100 °C, the effect of pre-ageing in Sn-added alloy can be further improved. The influence of Sn on vacancies at different ageing temperatures is discussed to explain the observed phenomena. [ABSTRACT FROM AUTHOR]

To expand the processing window of phthalonitrile resins, a novel self-catalyzed amino-epoxy 4-aminophenoxy phthalonitrile-resorcinol diglycidyl ether phthalonitrile (APRE-PN) resin was prepared via a two-step method of reacting amino and epoxy groups at a low temperature and then reacting nitrile with nitrile groups at a high temperature. The amine-epoxy, epoxy-nitrile, and nitrile-nitrile reactions were confirmed by Fourier-transform infrared spectroscopy and differential scanning calorimetry, and the probable polymerization mechanism was elucidated. The significant decrease in the melting point of the proposed APRE-PN prepolymers dramatically expands the processing window (173 °C) for an entire class of phthalonitrile matrices. The APRE-PN resin exhibits excellent thermal stability and dynamic mechanical properties owing to the presence of triazine, phthalocyanine, and oxazoline structures. The improved preparation method provides a new path for the preparation of phthalonitrile resins with large processing windows and new opportunities for the use of this type of thermosetting matrix in manufacturing various composite materials and prepregs. [ABSTRACT FROM AUTHOR]

The heating and extrusion process in fused filament fabrication (FFF) is significantly shorter than the conventional extrusion process where longer heating times and significant pressure are applied. For this reason, it is important to understand whether the crystal history of the feedstock is fully erased through the FFF process and whether the FFF process can be tailored further by engineering the crystallization of the feedstock filaments. In this context, a methodology for evaluating the influence of morphology and mechanical properties on different feedstock and extruded filaments is proposed. Filaments with three different PEEK 450G crystalline structures (standard crystallinity, drawn filament and amorphous filament) were selected and evaluated, before and after free extrusion. The resulting morphology, crystallinity and mechanical properties of the extruded filaments were compared against the feedstock properties. X-ray diffraction (XRD), transmission electron microscopy (TEM), differential and fast scanning calorimetry (DSC/FDSC) and tensile test were the techniques used to evaluate the materials. The results showed clear differences in the properties of the feedstock materials, while the analysis of the extruded filaments points to a homogenization of the resulting material producing mostly similar mechanical properties. However, the use of the drawn filament highlighted a statistically significant improvement in crystallinity and mechanical performance, especially in strain values. This conclusion suggests the innovative possibility of improving the quality of manufactured parts by tailoring the microstructure of the feedstock material used in the FFF process. [ABSTRACT FROM AUTHOR]

In this study coatings of kaolin and talc particles were successfully applied on the surface of polyamide 12 powder intended for laser sintering (LS). Microscopic observations revealed that using carboxymethyl cellulose (CMC) as surface modifier for fillers led to a better coverage of polymer grains with a surface coverage between 6 and 16% as a function of filler type and content. Differential scanning calorimetry measurements showed that the addition of talc and kaolin led to an increase in the crystallization temperature of PA12, but at the expense of processability. Process parameters were optimized in order to manufacture LS samples with the different coated powders. Fire behavior assessed by cone calorimetry showed that the use of CMC resulted in a significant decrease in the peak of heat release rate depending on the filler type and content. This behavior can be partially explained by an interaction between CMC, fillers and polymer, with the formation of amide linkage between carboxyl part of CMC and amine end groups of polyamide, resulting in an increase in the complex viscosity of materials. [ABSTRACT FROM AUTHOR]

The scope of this work was to investigate the quench sensitivity of a high-purity wrought aluminum alloy Al6Zn0.75 Mg (in this work called 7003pure). This is compared to a similar alloy with the additions of Fe, Si, and Zr at a sum less than 0.3 at.% (in this work called 7003Fe,Si,Zr). Differential scanning calorimetry (DSC) was used for an in situ analysis of quench induced precipitation in a wide range of cooling rates varying between 0.0003 and 3 K/s. In 7003pure, three main precipitation reactions were observed during cooling, a medium temperature reaction with a distinct double peak between 325 and 175 °C and a very low temperature reaction starting at about 100 °C. An additional high temperature reaction related to the precipitation of Mg2Si starting at 425 °C has been observed for 7003Fe,Si,Zr. In terms of hardness after natural as well as artificial aging, alloy 7003pure shows a very low quench sensitivity. Hardness values on the saturation level of about 120 HV1 are seen down to cooling rates of 0.003 K/s. The as-quenched hardness (5 min of natural aging) shows a maximum at a cooling rate of 0.003 K/s, while slower and faster cooling results in a lower hardness. In terms of hardness after aging, 0.003 K/s could be defined as the technological critical cooling rate, which is much higher for 7003Fe,Si,Zr (0.3–1 K/s). The physical critical cooling rates for the suppression of any precipitation during cooling were found to be about 10 K/s for both variants. [ABSTRACT FROM AUTHOR]

In this work, new bio-based copoly(ester amide)s were synthesized by a two-step melt polycondensation process, using 2,5-furanedicarboxylic acid dimethyl ester (DMFDC), 1,3-propanediol (PDO), and 1,3-diaminopropane (DAP), with different DAP content. The chemical structure of the obtained poly(trimethylene 2,5-furandicarboxylate)-co-poly(propylene furanamide) (PTF-co-PPAF) copolymers was confirmed by nuclear magnetic resonance (1H NMR) and Fourier-transform infrared (FTIR) spectroscopy. Gas chromatography/mass spectrometry was used to provide more details of the polycondensation process. Thermal properties of the obtained materials were characterized by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic–mechanical thermal analysis (DMTA). The copolymers were amorphous and their glass transition temperature increased with the increase in the poly(propylene furanamide) (PPAF) content. The synthesized PTF-co-PPAF copolymers exhibited improved thermal and thermo-oxidative stability up to 300 °C. In addition, from the performed mechanical tests, it was found that along with the increase in PPAF content, Young's modulus increased, while at the same time, the value of elongation at break decreased. [ABSTRACT FROM AUTHOR]

In this work, different formulations of a room-temperature silicone composite backing material (SCBM) composed of polydimethylsiloxane (PDMS), fumed silica and corn starch were investigated using different characterization techniques, i.e., differential scanning calorimetry, thermogravimetry analysis, X-ray diffraction (XRD) and small-angle X-ray scattering, as a function of controlled relative humidity. At ambient relative humidities in the range of about 20–80%, the equilibrium water content in the SCBM ranges from approximately 4–10%, which is predominantly absorbed by the corn starch. This amount of water content has been shown to have minimal effect on thermal transition temperatures (melting and glass transition) of the SCBMs. The enthalpy of melting increases with increasing relative humidity, which reflects the heterogeneous semicrystalline structure of starch granules and the role of moisture in facilitating the formation of amylopectin double helices mainly in the imperfect crystalline regions. The thermal degradation of SCBM exhibits three major mass loss steps that correspond to dehydration, decomposition of corn starch and decomposition of PDMS. The XRD patterns reveal a characteristic diffuse peak for amorphous PDMS and an A-type crystallinity for the corn starch. The XRD results show no observable changes in the crystal type and crystallinity as a function of moisture content. Results from this work help clarify the fundamental structure–property relationships in SCBMs, which are important for future development of documentary standards, especially the handling and storage specifications of next-generation ballistic witness materials for body armor testing. [ABSTRACT FROM AUTHOR]

The present study focuses on the preparation and characterization of a poly(ether ether ketone)/poly(ether imide) [PEEK/PEI] blend for application in additive manufacturing using fused filament fabrication (FFF). Polymer miscibility was evaluated using differential scanning calorimetry analysis and Fourier transform infrared analysis. The results confirmed the full miscibility of PEEK and PEI at all compositions. Seen as the best compromise between mechanical properties and glass transition temperature, a 70/30 wt/wt% PEEK/PEI blend was extruded into filaments for use by FFF. Nozzle temperature, layer orientation, and layer thickness were selected as printing parameters to evaluate their effect on the tensile properties and degree of crystallinity ( X c) . Optimum printing parameters were achieved at 380 °C nozzle temperature, a [0/15/−15°] layer orientation, and a 0.15 mm layer thickness. The printed PEEK/PEI samples were annealed at various temperatures to erase residual thermal stress generated during printing. Samples annealed for two hours at 200 °C have improved elastic modulus by 21.6%, while X c increased by 24.3%. Adding 30 wt% of PEI to the semicrystalline PEEK yielded three advantages, namely improving the operating and service temperatures by 20 °C, decreasing the processing temperature by 20 °C while maintaining most of the high tensile properties of PEEK. [ABSTRACT FROM AUTHOR]

In this study, poly(L-lactic acid) (PLA)/low molar mass alkali lignin (aL) (1%, 5% and 10% w/w) composites were prepared primarily for a comprehensive understanding of the effect of aL on their antimicrobial properties, biocompatibility and cytotoxic behavior. The properties were evaluated by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetry and X-ray diffraction. The mechanical, water vapor barrier properties and photodegradability were analyzed as well. The results showed a significant inhibiting effect of aL on the crystallization behavior of PLA, increased water barrier properties (up to 73%) and photodegradability. PLA/aL composites showed a tenfold reduction in Gram-positive bacteria viability, very good cellular response and very low cytotoxicity levels, thus validating these materials as non-cytotoxic and with high potential to be used as food packaging. [ABSTRACT FROM AUTHOR]

In this study, a novel hybrid multilayered electrospun nanocomposite membrane (MENM) was developed for activated wound dressing applications. An established electrospinning process was employed to fabricate a tri-layer nanocomposite membrane where the lower layer was composed of chitosan (CS)/polyvinyl alcohol (PVA) and fibrin (having regeneration of tissues and bleeding resistance properties), both of which are directly in contact with the burn wound (BW) skin, and a middle layer of PVA/sodium alginate (SA) (having antibacterial properties). The top layer consisted of gelatin (super hydrophilic properties). The MENM morphology was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) which confirmed the presence of the elemental and chemical structures of MENM. The MENM was identified by Fourier transform infrared spectroscopy (FTIR) with a maximum drug release which was ascended within 10-h duration. X-ray diffraction (XRD) showed long-term absorbency due to the presence of more amorphous and less crystallinity percentages in the MENM. The nanocomposites' thermal stability was also observed via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The developed MENM has shown excellent antibacterial activity with a zone of inhibition of 18.7 ± 0.9 mm, 18.9 ± 0.9 mm, 20.0 ± 1 mm and 19.3 ± 0.9 mm, respectively, against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The high water absorbant properties of MENM indicate that the produced membranes could absorb the maximum exudate from wounded skin within the shortest time and assist in healing the wound quickly. The produced MENMs could be potential wound dressing materials in the future. [ABSTRACT FROM AUTHOR]

The understanding of rapid solidification behaviour, e.g. the undercooling versus growth velocity relationship, is crucial for tailoring microstructures and properties in metal alloys. In most rapid solidification processes, such as additive manufacturing (AM), in situ investigation of rapid solidification behaviour is missing because of the lack of accurate measurement of the cooling rate and nucleation undercooling. In the present study, rapid solidification of single micro-sized Al-Si12 (mass%) particles of various diameters has been investigated via differential fast scanning calorimetry employing controllable cooling rates from 100 to 90,000 K s−1 relevant for AM. Based on nucleation undercooling and on microstructure analysis of rapidly solidified single powder particles under controlled cooling rates, two different heterogeneous nucleation mechanisms of the primary α-Al phase are proposed. Surface heterogeneous nucleation dominates for particles with diameter smaller than 23 μm. For particles with diameter larger than 23 μm, the nucleation of the primary α-Al phase changes from surface to bulk heterogeneous nucleation with increasing cooling rate. The results indicate that at large undercoolings (> 95 K) and high cooling rates (> 10,000 K s−1), rapid solidification of single particle can yield a microstructure similar to that formed in AM. The present work not only proposes new insight into rapid solidification processes, but also provides a theoretical foundation for further understanding of microstructures and properties in additively manufactured materials. [ABSTRACT FROM AUTHOR]

This study sought to analyze the semi-solid behavior of commercial 332 aluminum alloy during thixoforming in a mechanical eccentric press (thixoforging). The solid–liquid transition, i.e., the working temperatures corresponding to 77%, 67% and 54% fraction solid, was characterized using differential scanning calorimetry and simulation with Thermo-Calc® software. The alloy was then heated to the working temperature, held at that temperature for 0, 30, 90 and 210 s and thixoforged. The microstructure was characterized in three distinct regions of the thixoforged product: the end, the curved region and the central region. Different microstructures were observed along the product: in the central region, a completely deformed coarse dendrite microstructure was observed while in the region at the end of the product the microstructure was partially globular because the material flows into the die cavity without suffering significant deformation. The thixoforged alloy with the lowest fraction solid (52%), which was achieved at 572 ± 2 °C, had the most refined structure and smallest dendrite arm spacing (approximately 90 µm), leading to a yield strength of 151 MPa, ultimate tensile strength of 233 MPa and elongation of 0.6. These mechanical characteristics can be considered excellent as no prior preparation or modification of the raw material was carried out. The material thus has excellent potential for use in both thixoforming and rheocasting. [ABSTRACT FROM AUTHOR]

Among many β-metastable alloys explored for biomedical applications, alloys from the Ti-Nb-Fe-Zr system present great potential regarding cost and mechanical strength. In this article, we take a new look at the possibility of using Fe as a minor alloying element in the Ti-Nb-Fe-Zr system, with additions up to 2.0 wt% Fe. Additional compositions fixing the Nb/Fe ratio and changing Zr content from 7–13 wt% were also explored, resulting in a total of five different alloys. The samples were solution-treated and then subjected to three different conditions: water-quenched, furnace-cooled, and step-quenched to 450 ºC for 12 h. Resultant microstructures were analyzed using X-ray diffraction, differential scanning calorimetry, scanning, and transmission electron microscopy. DSC experiments indicate that Zr might alter the phase transformations that occur during heating and cooling cycles. First-principles calculations confirmed that Zr's addition is crucial to reduce the elastic modulus of the β matrix and increase the ω-phase formation energy relative to β. All alloys presented mechanical properties suitable for biomedical applications; however, Ti-23Nb-2.0Fe-10Zr (wt %) stands out with the best combination of mechanical strength and elastic modulus after aging. [ABSTRACT FROM AUTHOR]

The aluminum alloy 2618A is applied for engine components such as radial compressor wheels which operate for long time at elevated temperatures. This results in coarsening of the hardening precipitates and degradation in mechanical properties during the long-term operation, which is not taken into account in the current lifetime prediction models due to the lack of quantitative microstructural and mechanical data. To address this issue, a quantitative investigation on the evolution of precipitates during long-term aging at 190 °C for up to 25,000 h was conducted. Detailed transmission electron microscopy (TEM) was combined with Brinell hardness measurements and thorough differential scanning calorimetry (DSC) experiments. The results show that GPB zones and S-phase Al2CuMg grow up to < 1,000 h during which the GPB zones dissolve and S-phase precipitates form. For longer aging times, only S-phase precipitates coarsen, which can be well described using the Lifshitz–Slyozov–Wagner theory of ripening. A thorough understanding of the underlying microstructural processes is a prerequisite to enable the integration of aging behavior into the established lifetime models for components manufactured from alloy 2618A. [ABSTRACT FROM AUTHOR]

The peritectic reactions, liquid + δ-(ferrite) → γ(austenite) and the related casting problems during fast manufacturing process remain a big challenge for the compositional design and commercial production of high-quality Fe–C–Mn–Si steels. The precise prediction of the peritectic range of composition in steel is important in order to avoid the failure of casting and rolling; however, the effects of alloying elements on the peritectic range are unclear not only due to the large compositional space in alloyed steels but also its occurrence at high-temperature ranges, > 1400 °C. A combination of experimental measurements and thermodynamic modeling was employed to study the effects of alloying elements on the peritectic range for the wide composition ranges of Fe–C–Mn–Si steels. The phase transformation sequences and temperatures of two model Fe–C–Mn–Si steels were evaluated by differential scanning calorimetry (DSC) and in-situ confocal laser scanning microscope (HT-CLSM) and compared with thermodynamic calculation with TCFE9 database. The total number of 1680 phase diagrams is calculated by varying Mn from 0.3 wt% to 3.0 wt%, Si 0.05 wt% to 2.95 wt% and with and without a 0.02 wt% Ti addition. Using linear regression analyses for the calculations, we have predicted the correlation between peritectic ranges and the compositional space of Fe–C–Mn–Si steels. These results are effectively represented by contour plots and linear regression equations to predict the future outcomes of casting practice with their testing accuracy. It is also revealed that the peritectic ranges are influenced by complex elemental interactions, rather than the single-element effects of Mn, Si or Ti. The composition design of widely-applied Fe–C–Mn–Si steels is subject to a strict manufacturing restriction due to peritectic reaction and the related casting problems. This boundary condition is the topic of the current study. [ABSTRACT FROM AUTHOR]

This paper describes the crystallization which occurs upon annealing of an amorphous Fe-24at.%W coatings, electrodeposited from a glycolate-citrate plating bath. A combination of Differential Scanning Calorimetry and in-situ Transmission Electron Microscopy annealing is used to study the onset of crystallization of the amorphous coating. The in-situ TEM analyses reveal the formation of first crystallites after annealing at 400 °C for 30 min. Upon a temperature increase to 500–600 °C, the crystallites develop into Fe-rich nanocrystals with ~ 40 nm grain size. The nanocrystals are dispersed in the remaining amorphous Fe-W matrix, which results in the formation of a mixed nanocrystalline-amorphous structure. The observed crystallization can be held responsible for the increase in the hardness obtained upon annealing of Fe-24at.%W coatings. In fact, the hardness of the as-deposited material increases from 11 to 13 GPa after annealing at 400 °C, and it reaches the maximum value of 16.5 GPa after annealing at 600 °C. [ABSTRACT FROM AUTHOR]

The degradation of poly(ε -caprolactone)/poly(l-lactic acid) (PCL/PLLA) electrospun membrane was carried out in the phosphate buffer of esterase and water, respectively. A three-dimensional (3D) porous morphology was cultivated during esterase degradation, which was confirmed by scanning electronic microscope (SEM), while the structural evolution was analyzed by differential scanning calorimetry (DSC) combining with wide-angle X-ray diffraction (WAXD). Compared with hydrolysis, the degradation rate of enzymolysis was significantly faster. With the rapid decline in PCL crystallinity, the crystallinity of PLLA increased slightly after enzymolysis. The formation of porous morphology should be attributed to the relatively rapid degradation of PCL crystal and PLLA amorphous region attacked by esterase. Also, the number of micropores on the fiber surface increased with degradation time, which provides new ideas for preparing porous materials with higher porosity. [ABSTRACT FROM AUTHOR]

Non-isothermal crystallization kinetics of polypropylene (PP)/polytetrafluoroethylene (PTFE) fibrillated composites is presented. In-situ fibrillated PP/PTFE-composites containing 1 and 3 wt% PTFE were prepared by melt compounding using a twin-screw extruder. The morphology and non-isothermal crystallization behavior of the composites were examined using scanning electron microscopy and differential scanning calorimetry, respectively. The Mo equation was used to analyze the kinetics of non-isothermal crystallization behavior. The PTFE created a three-dimensional (3-D) network. A low PTFE content promoted crystallization through fast nucleation, whereas a high PTFE content decreased the crystallization kinetics through hindering the crystal growth. These findings are all based on the Mo equation analysis. The activation energy and nucleation activity were also evaluated, and the way in which the PTFE nanofibers affected the crystallization was discussed in detail. Polarized optical microscopy images revealed that the size of PP spherulites decreased with the increase of PTFE content. Finally, the effect of PTFE on the crystalline phase of PP was investigated by wide angle X-ray diffraction. [ABSTRACT FROM AUTHOR]

A novel electroformed nanocrystalline nickel cobalt alloy (n-NiCo) developed for sheet metal applications was investigated in terms of microstructure, as well as mechanical, thermal stability, and corrosion properties. The as-received material with a grain size of 18 ± 5 nm exhibited enhanced hardness compared with conventional polycrystalline NiCo mainly due to the Hall–Petch strengthening effect. Differential scanning calorimetry and annealing treatment results revealed that the n-NiCo was stable up to 200 °C for at least 1 h, and the onset of abnormal grain growth was observed when the material was annealed to 250 °C. While low-temperature annealing treatment was shown to increase the hardness of the material slightly, annealing at temperatures of 300 °C and above resulted in a reduction in hardness due to rapid normal grain growth. The n-NiCo sheet exhibited mixed Ni/Co anodic polarization behavior in environments of varying pH. [ABSTRACT FROM AUTHOR]

Catalyst-free synthesis in three kinds of isocyanate-blocked imidazole compound was successfully achieved by chemically connecting 2-ethyl-4-methylimidazole (2E4MI) with hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI) or 4,4′-diphenylmethane diisocyanate (MDI), which were tested as the latent hardeners for epoxy (EP) resins. The chemical structures of the synthesized HDI-2E4MI, TMHDI-2E4MI and MDI-2E4MI were identified with Fourier transform infrared spectroscope (FTIR), 1H and 13C nuclear magnetic resonance (1H NMR and 13C NMR). Based on characterizations including thermogravimetry/differential scanning calorimetry (TG/DSC) simultaneous testing and hot-stage FTIR, it was found that both HDI-2E4MI and TMHDI-2E4MI exhibited two-step deblocking behavior, whereas the deblocking process of MDI-2E4MI was completed only via one step. Curing kinetics of HDI-2E4MI/EP, TMHDI-2E4MI/EP and MDI-2E4MI/EP systems were then studied by non-isothermal DSC using Kissinger model. The results revealed that MDI-2E4MI/EP system could be cured via a two-step reaction with the highest curing rate due to the high reactivity of MDI-2E4MI, which was much different from the four-step curing behaviors of both HDI-2E4MI/EP and TMHDI-2E4MI/EP systems. Compared to the reference 2E4MI, noticeably, the three synthesized hardeners showed the outstanding latent features with lower curing activity and longer shelf life and the EP systems cured by the hardeners exhibited desirable mechanical properties and thermal stability. This study provided a feasible approach to synthesize high-performance imidazole-based latent hardener for wide practical applications in a greenway via the blocking treatment through tailoring the isocyanate structure. [ABSTRACT FROM AUTHOR]

Continuous heating transformation (CHT) diagrams and continuous cooling transformation (CCT) diagrams of precipitation-hardening steels have the drawback that important information on the dissolution and precipitation of Cu-rich phases during continuous heating and cooling are missing. This work uses a comparison of different techniques, namely dilatometry and differential scanning calorimetry for the in situ analysis of the so far neglected dissolution and precipitation of Cu-rich phases during continuous heating and cooling to overcome these drawbacks. Compared to dilatometry, DSC is much more sensitive to phase transformation affecting small volume fractions, like precipitation. Thus, the important solvus temperature for the dissolution of Cu-rich phases was revealed from DSC and integrated into the CHT diagram. Moreover, DSC reveals that during continuous cooling from solution treatment, premature Cu-rich phases may form depending on cooling rate. Those quench-induced precipitates were analysed for a broad range of cooling rates and imaged for microstructural analysis using optical microscopy, scanning electron microscopy and transmission electron microscopy. This information substantially improves the CCT diagram. [ABSTRACT FROM AUTHOR]

A new material for boron-free brazing of nickel-based superalloys is described that utilizes a transient liquid-phase bonding (TLPB) mechanism. Commercially available AMS 4764 powder (52.8Cu–37.5Mn–9.7Ni) was mixed with pure Ni powder to increase Ni content in the filler metal. This alloy is a good candidate for TLPB in Ni superalloy applications because of its high strength, low liquidus temperature, low cost and the absence of brittle intermetallic phases. Analysis of in situ braze joint formation with IN625 base metal using differential scanning calorimetry measurements allowed for optimization of Ni content, braze temperature and hold time conditions of the brazing process. Calculated ternary phase diagrams coupled with EDS analysis of braze joints identified a low-temperature copper-rich segregated region in braze joints, which, through interdiffusion with the base metal, increases melting temperature with increasing hold time. This work concludes that a 50-µm half braze joint can be formed through full isothermal solidification with an 80-min hold at 1050 °C. Solidification occurs primarily through interdiffusion of base metal and filler metal. [ABSTRACT FROM AUTHOR]

This work investigates the effects of time dependency for isothermal sintering on additive manufactured Ni–Mn–Ga magnetic shape memory alloys. Binder jetting additive manufacturing was used to produce Ni–Mn–Ga parts from pre-alloyed powders. Additive manufacturing via the binder jetting technique produces parts with intrinsic porosities, based on the morphology of the source material. The Ni–Mn–Ga parts printed in this study using the binder jetting method possessed average densities of ~ 46% before sintering. These samples were sintered at 1353 K in increments of 10 h up to 50 h. Based on this temperature and time frame, (1) microstructural evolution, (2) crystallographic phase analysis, (3) transformation behaviors, and (4) thermal–physical properties were investigated. The additive manufactured Ni–Mn–Ga samples exhibited increases in densities, from ~ 74 to ~ 83% due to solid-state diffusion mechanisms. X-ray diffraction reveals that all of the additive manufactured samples have the 5 M martensitic phase at room temperature. Reversible martensitic transformation temperatures were recorded during heating and cooling cycles through differential scanning calorimetry, which indicate austenitic phase transformations occurring slightly above ambient temperatures. Additionally, analysis of the heating and cooling cycles prescribes that the entropy and Gibb's energies decrease over the reversible martensitic transformations as sintering time increases. It is envisioned that this study will support a more synergistic manufacturing process between binder jetting additive manufacturing and post-heat treatment processes for Ni–Mn–Ga shape memory alloys. [ABSTRACT FROM AUTHOR]

A composite material of ZIF-67 and hydroxylated carbon nanotube (CNTOH) was prepared by a simple method and applied to catalytic decomposition of ammonium perchlorate (AP). The AP-based composites with ZIF@CNTOH added were tested by thermal analysis methods including differential scanning calorimetry (DSC) and thermogravimetric (TG). The results showed that the low temperature decomposition peak of the samples was weakened and even disappeared after the addition of the catalyst, and the high temperature decomposition peak was significantly advanced. When the content of CNTOH in ZIF@CNTOH is 5% and ZIF@CNTOH accounts for 5% in AP composite, the pyrolysis peak temperature was reduced from the original 409.7 °C to 298.8 °C, proved the significantly catalytic effect. This is mainly due to the effective uniform loading of transition metal ions on ZIF and the excellent electrical and thermal conductivity of CNTOH. The combination of them makes it achieve the best synergistic catalytic effect. [ABSTRACT FROM AUTHOR]

The geothermal history of natural resins from different geographical locations was studied in terms of their age assessment and structure–properties relations. Thermal properties of resin samples were analyzed by thermogravimetry (TG) and differential scanning calorimetry (DSC), whereas infrared spectroscopy was used for analysis of the resins structure. Relative dependence between thermal parameters and degree of resin maturity was found. Glass transition process and thermal events during heating of raw materials were investigated by advanced stochastic-modulated DSC method, known as TOPEM®, that allowed to determine the "true" glass transition temperature in the first heating scan. It was observed that TG method is insufficient for the resin age assessment, although it was found that there is a certain correlation between the glass transition temperature, estimated by TOPEM® DSC, and resin age. The natural resins proved to be reactive and sensitive material under elevated temperatures up to 200 °C. Subsequent processes of evaporation, relaxation and curing without significant mass loss related to degradation were observed during heating of resin samples. The aging rate in natural resins has been assessed using the intensity of 1730 cm−1 and 1646 cm−1 band after deconvolution of IR spectra. It may be assumed that younger resins are characterized by relatively higher reactivity (higher number of C=C bonds) and lower oxidation level. [ABSTRACT FROM AUTHOR]

The effect of In on melting property, microstructure and mechanical properties of Sn–40Bi–xIn (x = 0, 1, 2, 4, 6, 8 wt%, respectively) alloys was investigated by means of differential scanning calorimetry, scanning electron microscope, X-ray diffraction and tensile test. The results show that the solidus temperature and the liquidus temperature decrease with the increase in In content. The 1In, 2In and 4In alloys are composed of Sn–Bi eutectic and β–Sn dendrites with In atoms dissolved, whereas 6In and 8In alloys composed of Sn–Bi eutectics, BiIn–Sn metastable phases, Bi particles and primary β–Sn phases. At room temperature, 6In exhibits the maximum ultimate tensile strength of 77 MPa, while 4In displays a more outstanding elongation rate of 42%. Moreover, 2In alloy exhibits an even outstanding elongation behavior (above 300%) at temperatures of 100 and 120 °C. [ABSTRACT FROM AUTHOR]

Single-crystalline LiNi0.5Co0.2Mn0.3O2 (denoted as SC-523) with micron size had been successfully synthesized through a facile method. Electrochemical impedance spectroscopy and differential scanning calorimetry were carried out to identify the improved electrochemical performance and desired thermal stability. Even after 100 cycles, SC-523 still delivered a discharge capacity of 151.1 mA h g−1 (capacity retention with 90.3%) at 1 C in voltage range from 3.0 to 4.5 V (vs. Li/Li+), while polycrystalline spherical LiNi0.5Co0.2Mn0.3O2 (denoted as PC-523) only exhibited 141.7 mA h g−1 (capacity retention with 78.4%). Besides, SC-523 shows a higher decomposition temperature of 332.13 °C, 14.61 °C higher than that of PC-523 during the thermal decomposition. Consequently, single-crystalline particles with robust morphological integrity ensure the enhanced cycling stability and thermal stability. [ABSTRACT FROM AUTHOR]