Search

Liner materials have extensive applications in automobile industry, packaging, and aeronautics. One of the specific uses of such materials is in thermal barrier, coating rockets, missile, and other systems used in space and defense. Each liner material exhibits different properties according to their chemical structure and composition. In this study, accelerated thermal aging of the liner material, silicone‐hollow glass microsphere composite (SHGC) has been studied along with the determination of its life span. The effect of such aging on the thermal properties of SHGC has been studied using thermogravimetry. Activation energy of the process has been determined to be in the range of 45–55 KJmol−1. The results have been compared with already reported silicon polymers. Shelf‐life of SHGC composite has also been determined using Arrhenius model. Stochastic model has been applied to determine the lower and upper limits of shelf‐life. Shelf‐life of SHGC is found to be 24 years with 28 and 18 years of upper and lower error limits. [ABSTRACT FROM AUTHOR]

Dithienylethene photoswitches with an aromatic π‐linker as the bridge between the two thiophene units are attractive starting materials for developing molecular solar thermal energy (MOST) storage systems, partly because the aromaticity of their ring‐open forms is a favorable feature with regard to the energy‐storage densities of their ring‐closed forms produced by photoinduced electrocyclization (photocyclization) reactions. At the same time, this typically leads to small barriers for their thermal cycloreversion reactions, which are not desirable in this context. Here, we use computational methods to show that this problem can be circumvented with polycyclic heteroaromatic π‐linkers. Specifically, through the tuning of the aromatic character of the individual rings of such a π‐linker (like indole or isoindole), it is shown to be possible to strike a delicate balance between the seemingly contrasting requirements of simultaneously achieving both a high energy‐storage density and a large cycloreversion barrier. Furthermore, this design is also found to provide for a quick and efficient photocyclization reaction, owing to the onset of excited‐state antiaromaticity in the π‐linker upon light absorption of the ring‐open form. Altogether, dithienylethenes with polycyclic heteroaromatic π‐linkers appear to have both thermal and photochemical properties suitable for further development into future MOST systems. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing concern to counter environmental pollution, and as a result the development of biodegradable materials in various applications has become a major focus. This study aimed to fabricate a biodegradable composite by utilizing discarded hair keratin from beamhouse processing in leather production along with incorporating graphene oxide (GO) to reduce pollution. The composite was prepared using a simple solution mixing method, where the amino functional group of keratin and the carboxyl group of GO were covalently bonded under a redox system. Various analyses, including UV–visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, SEM, biodegradability and oxygen gas transmittance rate, were carried out to evaluate the composite's structure and performance. The results demonstrated that GO was successfully integrated into the keratin matrix, with uniform dispersion of GO observed instead of agglomeration. The composite with the optimum ratio exhibited a 173.98% increase in tensile strength and a 33.52% decrease in elongation as well as improved thermal and biodegradation properties compared to pure keratin. Furthermore, the composite displayed significantly better gas barrier properties (39%) than pure keratin, which can be attributed to the reduction of intermolecular gaps through the composite's strong bonding. Hence, the keratin‐GO composite is a cost‐effective and biodegradable solution to waste materials, with potential use as a packaging material. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Poly(3‐hydroxybutyrate) (P3HB), a biologically produced, biodegradable natural polyester, exhibits excellent thermal and barrier properties but suffers from mechanical brittleness, largely limiting its applications. Here we report a mono‐material product design strategy to toughen stereoperfect, brittle bio or synthetic P3HB by blending it with stereomicrostructurally engineered P3HB. Through tacticity ([mm] from 0 to 100 %) and molecular weight (Mn to 788 kDa) tuning, high‐performance synthetic P3HB materials with tensile strength to ≈30 MPa, fracture strain to ≈800 %, and toughness to 126 MJ m−3 (>110× tougher than bio‐P3HB) have been produced. Physical blending of the brittle P3HB with such P3HB in 10 to 90 wt % dramatically enhances its ductility from ≈5 % to 95–450 % and optical clarity from 19 % to 85 % visible light transmittance while maintaining desirably high elastic modulus (>1 GPa), tensile strength (>35 MPa), and melting temperature (160–170 °C). This P3HB‐toughening‐P3HB methodology departs from the traditional approach of incorporating chemically distinct components to toughen P3HB, which hinders chemical or mechanical recycling, highlighting the potential of the mono‐material product design solely based on biodegradable P3HB to deliver P3HB materials with diverse performance properties. [ABSTRACT FROM AUTHOR]

The industry desires to create robust, resilient, thermally stable, and environmentally friendly composites. In this study, we created a poly (lactic acid) (PLA) composite via a straightforward method. The Ti3C2TX was surface‐coated with polydopamine (PDA) via a bioinspired approach and was then reinforced in the PLA using melt blending. The PDA layer adorned on the Ti3C2TX provided several functional groups for the MXene nanosheets and strengthened the PLA‐MXene interaction by hydrogen bonding. The well‐dispersed PDA@Ti3C2TX in the PLA improved mechanical, thermal, and tribological properties. For PLA/PDA@Ti3C2TX‐1, the tensile strength and elongation at the break of the nano‐composite were 9.03% and 25.5% higher than pure PLA, respectively. The flexural strength and modulus were increased by 49.5% over pure PLA, reaching 148.8 and 6702 MPa, respectively. The nanocomposite toughness increased by up to 53.3%. The nanocomposites had 3.8% and 49.08% lower friction coefficient and specific wear rate, respectively, than pure PLA. The addition of Ti3C2TX and PDA@Ti3C2TX increased the thermal stability of PLA at lower temperatures and promoted carbonization. PLA/PDA@Ti3C2TX‐1 showed the maximum char yield of 10 wt.% at 800°C, proving the highest thermal barrier effect due to MXene exfoliation during PDA and increased PLA dispersion state. [ABSTRACT FROM AUTHOR]

This article investigates the impact of gamma irradiation on the thermal properties of porous silicon with varying levels of porosity. Porous silicon is a crucial nanomaterial in modern materials science, widely utilized in electronics, optoelectronics, and various applications. Understanding how its thermal transport properties change under gamma irradiation is of importance for various industries, including military, space, and nuclear technologies, where materials may be exposed to ionizing radiation. For this purpose, we employed the non-destructive photoacoustic method with gas-microphone registration. We assessed thermal conductivity as a function of porosity and irradiation time by simulating the experimental amplitude-frequency dependencies using an appropriate model. Our findings reveal that prolonged gamma irradiation of samples using Iridium-192 with an activity of 50 Curie for up to 20 minutes leads to a decrease in thermal conductivity in porous silicon. This is due to the emergence of defects in the crystalline structure of porous silicon and even its possible amorphization. These defects and alterations in the material's structure restrict the movement of heat carriers, thereby reducing its thermal conductivity. It is worth noting that the most significant change observed in this study is a two-fold reduction in thermal conductivity, particularly evident in samples with the highest level of porosity (60 %). Samples with higher porosity exhibit a stronger response to gamma irradiation because they contain less material within their volume that can conduct heat. The constraints within the crystalline structure of samples with greater porosity create additional barriers to heat transfer, leading to increased vulnerability of the material to radiation and a decrease in its thermal conductivity [ABSTRACT FROM AUTHOR]

Aliphatic polycarbonates (APCs) have become an essential packaging material because of their renewability, biodegradability, and biocompatibility. In this study, a series of high molecular weights APCs have been successfully synthesized using dimethyl carbonate (DMC) and different lengths of aliphatic diols with even carbon (n-CH2 = 4–12) via melt polymerization. Thermal properties, isothermal crystallization behavior, crystal structure, and scale of microstructure of APCs indicated that the flexibility and crystallization of molecular chains gradually increased with the increasing number of methylene groups of repeating units. However, due to the rigidity of ester group was higher than methylene group, and crystallization could increase the rigidity of chain segments, yielding strength and Young's modulus of APCs decreased first and then gradually increased with the increasing number of methylene groups in the repeating units. Furthermore, the scale of microstructure indicated that Brill transition increased the distance between intermolecular chains. Therefore, although the trans-gauche coexistence chain conformation simultaneously decreased the rigidity and crystallization of chain segments, barrier property of poly(octamethylene carbonate) with Brill transition was similar to long-chain APCs because of the lengthened diffusion path. The analytical mechanism of structure-performance relationship from the viewpoint of molecular interactions and chain structure will provide an entirely new thought for developing new barrier materials. [ABSTRACT FROM AUTHOR]

With the increasing number of electric vehicles (EVs) rises the need to recycle their used lithium-ion batteries (LIBs). During the mechanical process of the recycling of the LIB cells, a fine fraction, the so-called black mass, is created. This black mass consists mostly of the coatings originating from the cells' electrodes and residues from the electrolyte, together with a low amount of Al and Cu from the crushed current collector foils. The amount of black mass as well as its composition is influenced by the chosen grid size at the crusher discharge. To reduce solvent emissions during the recycling process, a thermal pre-treatment can be added before crushing, which also influences the black mass and its properties due to changes in the adhesion between electrode foils and coating. This study investigates the influence of the crusher settings as well as the pre-treatment temperatures to find an optimum between the recovery of the coating and conductive salt, while limiting the amount of Al and Cu in the black mass. [ABSTRACT FROM AUTHOR]

Mechanical, barrier, and thermal properties of films based on blends of corn starch and chitosan plasticized with ethylene glycol, glycerol, and sorbitol were investigated. Starch amylopectin variation was explored, and contents of 100% and 73% were employed to blend with chitosan and polyols. The findings showed that high amylopectin content has a significant effect (p < 0.05), resulting in films with lower tensile strength (TS) and reduced water vapor permeability (WVP). On the other hand, the incorporation of polyols showed a significantly high (p < 0.05) elongation at break (EB) for films plasticized with glycerol and sorbitol at high amylopectin content. For chitosan/73% amylopectin film, the addition of plasticizers exhibited no significant difference (p < 0.05) among the samples for TS and WVP results. The amylopectin content played no influence in the degradation stability of the films measured by thermogravimetry (TGA). However, amylopectin content influences the endothermic peak temperature observed by differential scanning calorimetry (DSC) analysis. A reduction of about 15 °C was noticed for the film prepared with high amylopectin content, a behavior correlated to its amorphous structure, capable of retaining more water than a crystalline region. [ABSTRACT FROM AUTHOR]

In this work, the effects of different ZnO-decorated graphene (Graphene-ZnO) proportions on the comprehensive properties of Poly(butylene succinate) (PBS) nanocomposites were investigated. The results show that the nanocomposites have stronger mechanical properties, higher thermal stability, greater crystallinity, better barrier ability, and excellent antibacterial property due to the influence of Graphene-ZnO. The tensile strength, crystallinity, melting temperature, thermal stability and barrier performance of the nanocomposites reached the maximum when Graphene-ZnO with a content of 0.2 phr was added. Compared with pure PBS, when Graphene-ZnO was added to PBS at 0.2 phr, the tensile strength, yield strength, elongation at break and moisture barrier performance of PBS were significantly increased by 22.5%, 31.34% ,62.84% and 42.57% respectively. This improvement in barrier performance might be attributed to the presence of Graphene-ZnO extended the penetration path of molecules and the coordination from PBS and Graphene-ZnO, so as to narrow the H2O transmission path. The results of the buried soil test show that the weight loss rate of the nanocomposite increased with increase Graphene-ZnO content, which may be caused by boundary defects between nanofiller and matrix, and poor compatibility at high content of Graphene-ZnO. [ABSTRACT FROM AUTHOR]

Pullulan-based smart packaging films were prepared by mixing cooked amaranth juice and bergamot essential oil. The impact of cooked amaranth juice and bergamot essential oil on the color-changeability, structural characterization, and barrier, antioxidant, mechanical and thermal properties of pullulan-based films was determined. Results showed the cooked amaranth juice contained pH-response color-changing betacyanins. The pullulan films containing cooked amaranth juice were color-changeable in pH 9–12 buffers and in ammonia vapor. The color-changeable property of betacyanins in cooked amaranth juice was unaffected by bergamot essential oils. The inner structure of pullulan films was greatly affected by cooked amaranth juice, forming big and ordered humps in film cross-sections. The crystallinity of pullulan films was improved by the combined addition of cooked amaranth juice and bergamot essential oil. Among the films, the pullulan film containing cooked amaranth juice and 6% bergamot essential oil showed the highest UV-vis light barrier property, antioxidant activity, and tensile strength; while the pullulan film containing cooked amaranth juice and 4% bergamot essential oil showed the highest oxygen barrier property and thermal stability. Moreover, the pullulan films containing cooked amaranth juice were able to monitor the freshness of shrimp by presenting color changes from reddish purple to dark red. [ABSTRACT FROM AUTHOR]

Utilizing 3D-printing techniques to fabricate novel composites with multifunctional properties is a real challenge. This study deals with the synthesis of graphitic carbon nitride (g-C3N4) using melamine and reinforcing it with Poly (lactic acid) (PLA) to achieve enhanced mechanical and thermal properties. g-C3N4 is a silane surface modified to increase the bonding strength between filler and matrix. PLA/ g-C3N4 composite filament is extruded using a controlled speed of 30 rpm and a temperature of 170 °C, and samples are 3D-printed. To improve mechanical and thermal properties, varying weight percentages (0, 0.5, 1, 3, 5) of g-C3N4 are reinforced into the PLA matrix. The PLA composite (3% filler) exhibited a tensile strength of 62 MPa. The flexural and impact strengths of the composite containing 3% g-C3N4 were 63 MPa and 6.5 KJ/m2, respectively. Mechanical properties of 3D printed PLA/g-C3N4 composites were enhanced due to dispersed g-C3N4 filler particles, which shared the stress produced in the polymer and the g-C3N4 entrapped the polymer matrix molecular chain. Compared to PLA composite (5% filler) and pure PLA, the initial and final degradation temperatures were increased by about 4.15% and 4.38%, respectively. The thermal properties improved owing to the g-C3N4 particles acting as a thermal barrier in the PLA matrix. Additionally, silane-treated g-C3N4 particles meet the PLA matrix, and the organo-functional group of the silane interacts with the PLA matrix, thus enhancing the interfacial bonding, which restricts the motion of polymer chains at elevated temperatures. The 3D printing process could make them more competitive in the market by making commercial PLA parts that are better for the environment and have better mechanical and thermal properties. [ABSTRACT FROM AUTHOR]

Nanocomposites are heterogeneous media with two or more micro‐structural levels. For instance, a nano‐level is characterized by isolated nano‐inclusions, and a micro‐level is represented by the clusters resulting from aggregation processes. Based on the reiterated homogenization method, we present a procedure to study the influence of this aggregation process and interfacial thermal resistance on the effective thermal conductivity for 2‐D square arrays of circular cylinders. First, an effective intermediate thermal property is obtained by taking into account only the influence of the individual nano‐inclusions in the matrix. Second, the final effective thermal coefficient (k^RH$$ {\hat{k}}_{RH} $$) is calculated considering the clusters immersed in the intermediate effective medium derived in the first step. The conductivity gain (kgain$$ {k}_{gain} $$) is defined as the quotient (k^RH/k^CH$$ {\hat{k}}_{RH}/{\hat{k}}_{CH} $$) where k^CH$$ {\hat{k}}_{CH} $$ is the effective thermal coefficient computed considering only one microstructural level with the same volumetric fraction of inclusions. We apply the theory of complex variable functions deriving in an infinite system of equations solvable by truncation method. The analytical formulas of the effective coefficient used in the calculations generalize other well‐known formulas reported in the literature. We also provide formulas for several truncation orders. The main novel contribution is in the reiterative application of the obtained formulas to illustrate the gain effect in nanocomposites, expressed as a function of the Biot number, thermal conductivities, volumetric fibers fraction, and an aggregation parameter. Furthermore, this result can be used to assess numerical computations and for nano‐reinforced fibers and nanofluids applications. An appendix is included showing similarities and differences with a three‐phase model. [ABSTRACT FROM AUTHOR]

This study investigated the impact of a Ge2Sb2Te5 (GST) thermal barrier on the performance of NbO2-based selector devices. Our findings showed that the GST barrier could significantly decrease the off-state leakage current from 3 μA to 300 nA without increasing the threshold switching voltage owing to its insulation properties and high thermal resistance. We also found that the GST barrier can effectively contain the Joule heat within the NbO2 switching region, as confirmed through a cryogenic analysis of the thermal resistance of GST. The results showed that the GST/NbO2 device had a thermal resistance 3.48 times higher than that of a single-layer NbO2 device. Our results provide design guidelines for utilizing a barrier layer to reduce the leakage current in low-power threshold switching devices. [ABSTRACT FROM AUTHOR]

Polymer nanoclay composites have received significant attention due to their substantially enhanced mechanical, thermal and barrier properties. However, the effect of these nanoclays on the dynamic fracture resistance of a polymer matrix during fast fracture events has not been documented. In this study, the effect of nanoclay addition on the rapid crack propagation (RCP) resistance of high-density polyethylene (HDPE) was investigated through the high-speed double torsion test. Results showed that the addition of 1, 3, and 5% of nanoclays improved the dynamic fracture resistance under the plane strain conditions ( G d 1 ) of HDPE up to 65%. An increase in the storage and loss modulus, and a decrease in crystallinity and melt flow index with nanoclay content was also found. Although the presence of agglomerates can hinder the enhancement of G d 1 as it promotes agglomerate fracture and debonding, the increase in energy consumption through fibrillation and crazing promoted by the nanoclay prevails, suggesting that the nanoclay's toughening effect that has been extensively reported under quasi-static and impact tests, is also present under RCP conditions, and that the HDPE nanocomposites could be used in applications in which RCP must be prevented. [ABSTRACT FROM AUTHOR]

The bioeconomy aims to discover new sources for producing energy and materials and to valorize byproducts that otherwise would get wasted. In this work, we investigate the possibility of producing novel bioplastics, made up of argan seed proteins (APs), extracted from argan oilcake, and amylose (AM), obtained from barley plants through an RNA interference technique. Argan, Argania spinosa, is a plant widespread in arid regions of Northern Africa, where it plays a fundamental socio-ecological role. Argan seeds are used to obtain a biologically active and edible oil, producing a byproduct, the oilcake, that is rich in proteins, fibers, and fats, and is generally used as animal food. Recently, argan oilcakes have been attracting attention as a waste to be recovered to obtain high-added-value products. Here, APs were chosen to test the performance of blended bioplastics with AM, because they have the potential to improve the properties of the final product. High-AM-starches present attractive features for use as bioplastics, including a higher gel-forming capacity, a higher thermal stability, and reduced swelling compared to normal starch. It has already been demonstrated that pure AM-based films provide more suitable properties than normal starch-based films. Here, we report on the performance of these novel blended bioplastics in terms of their mechanical, barrier, and thermal properties; and the effect of the enzyme microbial transglutaminase (mTGase) as a reticulating agent for AP's components was also studied. These results contribute to the development of novel sustainable bioplastics with improved properties and confirm the possibility of valorizing the byproduct, APs, using them as a new raw material. [ABSTRACT FROM AUTHOR]

The solution precursor plasma spray (SPPS) process involves injecting atomized droplets of a precursor solution into the plasma plume. In this study, two different solution precursors were used in the SPPS process including zirconium oxynitrate and zirconium acetate to make thermal barrier coatings (TBC). The effect of these solutions on microstructure and high-temperature properties of thermal barrier coating made by SPPS has been studied. The results showed that the use of zirconium acetate as a precursor compared to zirconium oxynitrate led to the formation of more vertical cracks with an average spacing of 150-200 μm in the microstructure of coatings. This was due to the presence of more un-pyrolysis or semi-pyrolysis materials in the coating structure and their shrinkage stresses during the deposition that was dependent on the solution chemistry in the plasma plume. The oxidation test at 1000 °C for various times of 12, 50, 120, and 250 h showed similar behavior for both coatings. In addition, the coating obtained from zirconium acetate precursor exhibited an average life of 648 cycles in a 1-h 1000 °C thermal cycling test, which was more than about 1.5 times that of SPPS-TBC coating made of zirconium oxynitrate precursor (431 cycles) due to the presence of much more vertical cracks in its structure. [ABSTRACT FROM AUTHOR]

The high-entropy ceramic materials (Zr 0.25 Ce 0.25 Hf 0.25 Y 0.25)O 1.875 (H-0) and (Zr 0.2 Ce 0.2 Hf 0.2 Y 0.2 RE 0.2)O 1.8 (H-RE) (RE = La, Nd and Sm) with fluorite structure and homogeneous element distribution were prepared. With fluorite structure, fine grain size and high density, the H-0 and H-RE ceramics displayed low thermal conductivity, suitable thermal expansion coefficient, high hardness and fracture toughness. The effect of La, Nd and Sm on the mechanical, heat conductivity and heat expansion properties of high entropy ceramics were discussed. The single-phase high-entropy ceramic materials in this work are very suitable for application as thermal barrier materials. [ABSTRACT FROM AUTHOR]

In this paper, a series of poly(ethylene terephthalate‐co‐2,6‐naphthalate) (PETN) (co)polyesters with different naphthalene ring contents were synthesized via a two‐step transesterification and polycondensation. The effects of the monomer compositions on the sequence distribution, crystallization, mechanical, thermal, and barrier properties of the (co)polymers were investigated systematically. The results showed that the introduction of naphthalene ring units (NDC) changed the sequence length of the PETN and disrupted the orderly arrangement of the PETN molecular chains, thus affecting the aggregated structure and properties of the copolymer. When the NDC content was less than 30%, the PETN copolymers displayed good ductility and higher yield strength comparable to PET, and the heat distortion temperature (HDT), thermal stability properties, and barrier properties of the copolymer were also improved. In addition, the diffusion kinetics of water and oxygen molecules in the (co)polymer were investigated by the MS program simulation software. The differences in gas barrier properties of the different PETN (co)polymers were explained at the molecular level. This study provides a systematic theoretical basis and comprehensive practical guidance for the preparation of high‐performance copolyester materials. [ABSTRACT FROM AUTHOR]

Polyurethane (PU) and zinc ionomer (ZnI)-based polymer composites films were developed by melt extrusion method. The structure, phase morphology, rheology, and mechanical properties of the PU/ZnI blends were studied. The X-ray diffraction analysis displaced that there is no major effect on the crystallinity of PU phase by the addition of ZnI. Scanning electron microscopic images confirmed the partial miscibility of PU and ZnI, which greatly influenced on the tensile and elongation at break (EB) properties of the composite films at a high ratio. Dynamic mechanical analysis indicated that with increasing the ZnI content, the storage modulus of the blends decreased and exhibited two T g temperature peaks. Tensile strength of the PU/ZnI composites decreased drastically and EB increased significantly by the addition of ZnI, however a degree of interaction has been found. PU/ZnI composite films improved surface hydrophobic with excellent water barrier properties. The ultraviolet transmittance of the PU increased with increasing the content of ZnI. [ABSTRACT FROM AUTHOR]

Titanium dioxide hollow microspheres (HMS-TiO 2) were successfully synthesized through a sol-gel and subsequent high-temperature calcination method using a hard template. These microspheres exhibit an average particle size of about 13.66 μm and a shell layer thickness approximately 1.18 μm. Furthermore, the thermal insulation effect is evident in cementitious materials coated with an HMS-TiO 2 -based composite film. The maximum average near infrared (NIR) reflectance and thermal insulation temperature difference of these coated materials are 46.81 % and 9.3 ℃, respectively. Notably, the modified composite film displays excellent mechanical and impermeable properties when applied to the surface of cement mortar samples. These comprehensive results indicate that introducing HMS-TiO 2 with the synergy of structure and composition significantly enhances the thermal, mechanical, and durability properties of modified waterborne coatings on cement-based materials. This augmentation makes them well-suited for thermal insulation and heat preservation applications in building structures. • Micro-scale hollow TiO 2 was synthesized using a hard template method. • The synergy of structure and composition is crucial for cement coatings. • Hollow TiO 2 -based coatings show excellent thermal insulation properties on buildings. [ABSTRACT FROM AUTHOR]

The mechanical properties especially the compression performance are very important for thermal interface materials (TIMs) to mitigate warpage failure caused by stress concentration and reduce contact resistance in practical applications. However, high thermal conductivity and excellent mechanical properties are generally incompatible in traditional TIMs. Herein, we fabricate a high-performance carbon fiber-based TIM by using an extrusion method based on the flow shearing effect. The vertically oriented composite shows a through-plane thermal conductivity up to 18.5 W·m−1·K−1 at 20 wt% carbon fiber content, which is 92.7 times that of pure matrix and 6.3 times that of the random structure. Moreover, the as-prepared material exhibits low hardness of 56 (Shore 00) and outstanding elastic compression performance of 51.4% compression under a pressure of 45 psi. These excellent properties are primarily attributed to the high orientation of the carbon fibers (CFs), thereby establishing a direct and effective thermal conductivity path in the vertical direction. In addition, the synergistic effect of carbon fibers and alumina particles is also beneficial for building thermal conduction pathways. Our work provides an insight to further research in fabricating high-performance flexible TIMs as a promising candidate for applying in advanced thermal management fields. • The composite achieves a thermal conductivity of 18.54 W·m−1·K−1. • The composites exhibit good elastic compliance under high through-plane thermal conductivity. • The synergistic effect of carbon fibers and alumina promotes the enhancement of thermal conductivity [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) is the most common material used as a thermal barrier in several engineering applications. In order to improve the insulator potential of these thin films, an oblique-angle deposition approach was used to grow YSZ with tilted columnar structures. Initially, the period (n) was defined as the repetition unit composed of two layers each with different columnar growth directions, and then, n was increased (n = 1, 2, 10, 30, and 50), keeping constant the total thickness (~3.50 µm). The influence of (n) on the structure, roughness, grain size, microstructure, and thermal conductivity (κ) of thin films deposited was determined by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy, and hot-plate technique, respectively. For all the samples, XRD patterns indicate the presence of the characteristic 8YSZ tetragonal phase peaks. Through AFM analysis, it was established that the roughness of the films deposited decreases from (4.0 ± 0.6) to (2.0 ± 0.6) nm when n is increased. Cross-sectional images recorded by SEM corroborate the formation of marked interfaces when growth direction changes occur, allowing to identify a multilayer system with a "zigzag" microstructure and an evolution towards more refined and isolated columns. Moreover, the SEM images reveal that for n = 10, 30, 50, and 70, the growth direction of the column is perpendicular to the substrate plane, losing its tilted form and the "zigzag" behavior becomes intracolumnar, reaching nanometer scale. Finally, analyses by hot-plate technique for different n repetition units showed that the thermal conductivity of YSZ films decreases from 0.151 W/m K to 0.064 W/m K, establishing the direct influence of the "zigzag" microstructure on the j value. This study shows the potential of growing YSZ thin films by oblique-angle deposition as an effective method to improving the thermal insulator potential of this material. [ABSTRACT FROM AUTHOR]

• Thermal transport through SEI of Li-ion batteries was studied using MD simulations. • Three representative inorganic components of SEI were considered. • Impact of structural properties and temperatures were investigated. • Thermal conductivity of amorphous compounds is closely related to the components. • Results provide valuable insights for the design of electrolytes and SEI. The thermal behavior during operation of Lithium-ion batteries (LIBs) is widely concerned with respect to their electrochemical performance and safety. The solid electrolyte interphase (SEI) is a critical layer formed during electrochemical reactions in LIBs. A thorough understanding of SEI's thermal transport properties is essential to identify limitations within the internal heat transfer of LIBs. In this work, a computational study of the thermal transport through SEI was performed based on classical molecular dynamics (MD) simulations. Three representative inorganic components of SEI, namely Li 2 CO 3 , Li 2 O and LiF, were explored. First, the force fields were evaluated for accurate MD simulations. Subsequently, the impact of structural properties and temperatures on the thermal conductivities of SEI were investigated, followed by discussion on radial distribution functions and vibrational density of states. It was found that the comparison of thermal conductivity of the ordered crystals is Li 2 O > LiF > Li 2 CO 3. As temperature increases, the thermal conductivity of inorganic components decreases significantly. Additionally, it was discovered that the thermal conductivity of amorphous compounds is notably lower than that of ideal crystals and is closely related to the molar ratio of inorganic components. The results of this work can help understand the thermal transport properties of SEI and offer valuable insights for the design of electrolytes and SEI toward improving the thermal safety performance of LIBs. [ABSTRACT FROM AUTHOR]

Carboxymethyl starch (CST) was introduced to improve gelatin films and its practical application as edible high-performance films for food packaging and cooking was also investigated. The gelatin films modified by carboxymethyl starch exhibited the transparent appearance, tensile strength, barrier properties (oxygen, water vapor and UV light), and thermal performance (TGA, thermal shrinkage and heat-sealing strength). Resulting from the effect of electrostatic interaction modes on the properties of films, electrostatic repulsion could surpass electrostatic attraction in improving the tensile strength, oxygen barrier property and thermal stability of the films probably due to extensive physical entanglement without aggregation. Analysis of FTIR, zeta potential, interfacial dilatational rheology, shear rheological properties, XRD, Raman, SEM and AFM suggested that hydrogen bonding and electrostatic repulsion contributed to the excellent performance. The packaged food could also be cooked with the prepared film for porridge; and the film slightly influenced the shear rheological properties of porridge and imposed little effect on the odors (Electronic-Nose) of porridge. Hence, the gelatin films modified by carboxymethyl starch could potentially work as the edible inner packaging or the edible quantitative packaging for food, offer convenience for consumers, reduce the packaging waste and avoid an extra burden on environment. • CST improved mechanical and barrier properties (O 2 , moisture and UV light) of films. • CST enhanced the thermal stability, thermal shrinkage and sealing strength of films. • Hydrogen bonds and electrostatic repulsion improved compact matrix and performance. • Excessive CST granules caused the weak interactions and the property deterioration. • The packaged food could cook porridge and slightly affect the rheology and odors. [ABSTRACT FROM AUTHOR]

The effects of substituting the B cation in A3BO7 ceramics on their thermal physical properties were investigated by applying a large mass difference. Y3(Nb1‐xTax)O7 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) ceramics were synthesized, and their structural characteristics were determined. All the fabricated Y3(Nb1‐xTax)O7 ceramics showed defective fluorite structures and glass‐like low thermal conductivity (1.18−2.04 W/m∙K at 25°C) because of the highly distorted crystal structure and significant mass difference. Substitution with Ta5+ enhanced the sintering resistance, leading to superior thermal‐insulating performance via grain boundary scattering. Furthermore, the ceramics exhibited excellent coefficients of thermal expansion, implying the promising applicability of Y3(Nb1‐xTax)O7 as new thermal barrier materials. The effect of mass difference on the thermomechanical properties of the ceramics was examined, suggesting a simple strategy for engineering the chemical composition of new thermal barrier materials. [ABSTRACT FROM AUTHOR]

In the present study, the effect of nanoclay and nanomica on the structural, thermal and barrier properties of poly (ethylene terephthalate) was investigated. The morphology of the papered nanocomposites (Clay and Mica) was illustrated by X-Ray Diffraction (XRD), Transmission electron microscopy (TEM) and Atomic force microscopy (AFM). According to Dynamic Mechanical Thermal Analyzer (DMTA) results, the samples' tanδ values ranged from 0.4 to 0.6. The results of Differential scanning calorimetry (DSC) revealed that the incorporation of nanoparticles increased both the crystallization temperature (Tc) and the degree of crystallization (Xc). Then, the higher aspect ratio of nanomica compared to nanoclay led to higher levels of Xc. A significant water vapor permeability decrease (maximum reduction at 1% loading level of nanomica) of nanocomposites was attributed to an increase in the tortuosity of water vapor molecules path diffusing into the nanocomposites. PET/mica nanocomposites presented larger tortuosity factors compared to PET/clay. As a result, improved barrier properties of nanocomposites were obtained in the case of food packaging. [ABSTRACT FROM AUTHOR]

In this study, a high-entropy approach was employed to design a new single-phase A 2 B 2 O 7 oxide for thermal insulation applications. Multicomponent high-entropy oxides, containing up to seven different cations, were successfully synthesized in a single defective fluorite structure. We observed that the incorporation of the functional cation, Zn2+, effectively blocked the heat radiation phenomenon by reducing the photon mean free path, and further reduced the high-temperature thermal conductivity owing to the larger free carrier concentration originated from the large number of oxygen vacancies. Although a large concentration of Zn2+ caused a slight reduction in thermal expansion, this study suggests that functional cations can be easily incorporated; thus, expanding the material diversity beyond the typical doping levels to develop new thermal barrier materials. [ABSTRACT FROM AUTHOR]

Because the CMAS corrosion and phase transformation at elevated temperatures above 1250 °C have limited the applications of traditional YSZ, the design of novel thermal barrier materials is a hotspot. GdTaO 4 is considered as a type of potential novel thermal barrier material owing to its low thermal conductivity. In this study, the mechanical and thermal properties, CMAS corrosion resistance, and the wettability of the GdTaO 4 were studied and compared with that of YSZ. The results show that the coefficient of thermal expansion and hardness of GdTaO 4 are 14.1 × 10−6 K−1 (1350 °C) and 534.2 Hv 0.3 respectively. The thickness of CMAS reaction layer of GdTaO 4 is ~30.8 μm after 24 h reaction at 1350 °C, which is thinner than that of YSZ. After corrosion reaction, the CMAS glass aggregated instead of completely disappearing or continuously extending over the surface of GdTaO 4. The main reaction product is Ca 2 Ta 2 O 7 , and the anorthite phase may not be detected, which is similar to YTaO 4. By comparison, the dense substrate of YSZ became porous and CMAS glass has disappeared after 10 h. CMAS corrosion at 1350 °C. The on-line contact angle results show that the wettability of CMAS on GdTaO 4 is worse than that on YSZ at 1350 °C, while the opposite of the work of adhesion, which indicates that GdTaO 4 can remove liquid CMAS more easily than YSZ TBCs during the service. Furthermore, the corrosion depth and areas of GdTaO 4 are smaller than those of YSZ in the same situation. These findings suggest that GdTaO 4 possesses better high-temperature properties and CMAS corrosion resistance than YSZ as a kind of potential of thermal barrier material. [ABSTRACT FROM AUTHOR]

Amine‐functionalized MIL‐101(Cr)‐NH2 metal–organic frameworks (MOF‐N)/epoxy nanocomposites with Excellent cure label and high thermal stability were developed. Structure–property relationship was discussed by comparison of the cure state, thermal and viscoelastic behavior of epoxy nanocomposites containing pristine MOF or MOF‐N applying differential scanning calorimetry (DSC), thermogravimetric analysis, and dynamic mechanical analysis. Epoxy containing 0.3 wt% MOF‐N exhibited high glass transition temperature (Tg) of 96°C compared with 85°C observed for epoxy/MOF system. Thus, MOF‐N played the role of catalyst in epoxy/amine curing reaction. Correspondingly, a lower activation energy was obtained based on cure kinetics modeling based on DSC measurements. Besides, incorporation of low amount (0.5 wt%) MOF‐N induced an early‐state resistance against decomposition, featured by 11°C rise in decomposition temperature at 5% weight loss. This was ascribed to the formation of porous metallic oxides during thermal decomposition of MOF‐N in the epoxy system acting as a heat barrier, which increased the activation energy of decomposition. Amine‐functionalization considerably prevented from further oxidation of the inner part of the matrix. [ABSTRACT FROM AUTHOR]

Cellulose nanofibrils (CNFs) can be used as an effective reinforcement material for biopolymer films intended for food packaging applications. The aim of this study was to improve the mechanical and barrier properties of xylan-alginate films by incorporating CNFs into the xylan-alginate matrix. CNFs was produced from maize stalk waste residues through a combination of chemical and mechanical treatment. The CNFs was incorporated into the xylan-alginate matrix between 1 and 10 wt%. The suitability of the CNFs reinforced composite films for food packaging applications was investigated by testing the mechanical, thermal and optical properties as well as the moisture sorption, solubility and water vapour permeability of the films. The CNFs produced had fibre diameters between 10 and 80 nm and transmission electron microscopy images showed that the CNFs were highly entangled hence forming a web like structure. It was found that the incorporation of CNFs into the xylan-alginate matrix increased the tensile strength and Young's modulus of the films. The incorporation of CNFs improved the WVP of the films but did not show any significant effect on the thermal properties of the films. [ABSTRACT FROM AUTHOR]

Biodegradable starch material is considered one of the best alternatives to traditional petroleum-based synthetic plastics. The effects of ultrasound (40 kHz) and ozone (20 g/h) modifications on corn starch were investigated using ultraviolet absorption, titration, Fourier transform, differential scanning calorimetry, and X-ray diffraction. As well as the effects of the dual modification on biodegradable films' morphology, thickness, water content, water solubility, moisture absorption, water vapor permeation, opacity, water contact angle, and mechanical and thermal properties were evaluated. For dual modification, the ultrasonic modification was carried out first, followed by oxidation under the same conditions as an individual modification. After ultrasonic and ozone modification, the crystallinity of starch decreased, and the solubility increased to some extent. Starch's swelling power and solubility increased by 4.90% and 159%, respectively, after 10 min of ozone treatment. The tensile strength of the films modified by ozone for 10 min increased by 276%, the elongation at break increased by 72.5%, the water contact angle of the films modified by ozone increased by 154%, and the water vapor permeability decreased by 34.7%. Compared with the natural and single-modified starch films, the dual-modified ones had lower water vapor transmittance, moisture absorption rate, and higher transparency. The water vapor permeability decreased by 32.2%, and the transparency increased by 73.7%. The modification in this study had little effect on the solubility of the films. [Display omitted] • The combination of ultrasonic and ozone was an innovation in the corn starch film. • Ultrasonic and ozonation dual-modification had positive effects on starch films. • The TS, WVP, and WCA of the O10 starch film were significantly improved. • The high MA of the oxidized starch film was reduced by ultrasonic treatment. [ABSTRACT FROM AUTHOR]

The demand for biopolymer-based green packaging has attracted growing attention because of its outstanding properties and consistency with clean environmental principle, unfortunately, its slow crystallization rate and narrow processing window are challenging. Inspired by combined functions in nanocellulose-based conductive hybrids, this work developed high-performance polylactic acid (PLA) composites using conductive cellulose nanofiber (CNFene). Interestingly, CNFene has multiple functions as highly graphitized carbon and abundant hydroxyl groups, delivering stimulating properties to PLA composites. As nucleating agents, 3 wt% CNFene has a carbon layer on the surface combined with a hydrogen bonding network synergistically enhancing the tensile and crystallization properties of PLA-C3, with a tensile strength of ∼ 53.7 MPa, crystallinity of ∼ 33.9 %, and 6.6 °C decrease in the cold crystallization temperature. Additionally, the compatibility between CNFene and PLA can form a multi-level "reinforcement" network structure, further improving thermal stability and barrier properties. The resultant PLA-C3 showed higher thermal decomposition onset temperature (T 0), wider melt-processing window (197.6 °C) and extremely lower overall migration levels in ethanol (68.6 μg/kg) and isooctane (16.3 μg/kg), due to that improved interaction between CNFene and PLA positively affects crystallization ability and kinetic/mechanism of PLA to meet the requirements of industrial and green biopackaging applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-based copolyesters involving 2,6-pyridine structure with isosorbide as a second diol were synthesized. • Incorporation of isosorbide enhanced thermal properties of the pyridine-based polyesters. • Isosorbide significantly improved the mechanical properties of the pyridine-based polyesters. • The copolyesters showed high gas barrier properties. Driven by sustainable development and low-carbon policies, many high-performance bio-based polyesters are produced. Our previous work uncovered the high barrier but low thermal and mechanical properties of a renewable 2,6-pyridinedicarboxylic-based polyester. In this article, the copolymerization with isosorbide as a second diol is considered to ameliorate these properties. The chemical structures of copolyesters and the successful introduction of isosorbide were confirmed by FT-IR and 1H NMR. The 1H NMR spectra also allowed the calculation of isosorbide ratio in polymers. GPC revealed a decrease in molar masses with the increase of isosorbide ratio. Contact angle and water/gas permeation measurements disclosed an increase in hydrophilicity and water/gas permeability with the introduction of isosorbide. TGA and DSC analyses demonstrated an enhancement in thermal stability: 8 mol% of isosorbide to the total diol ratio increased the 5 % weight loss temperature (T 5%) by 9 °C, the maximum weight loss temperature (T max) by 8 °C and the glass transition temperature (T g) by 6 °C. DSC investigation showed that the incorporation of isosorbide significantly influenced the crystallization properties, particularly from the melt, by decreasing the crystallinity. XRD patterns indicated the presence of similar crystallization units in these polyesters. Tensile test revealed that incorporating 8 mol% of isosorbide greatly improved the mechanical properties by doubling Young's modulus and tripling the strength at break. Such enhancement in thermal and mechanical properties is important for high gas barrier food packaging applications of these polyesters. [ABSTRACT FROM AUTHOR]

Packaging materials based on lightweight and flexible thermoplastic/graphene composite films are gaining popularity in both the academic and industrial sectors. In this research work, graphene nanoplatelet (GNP) of 1–5 wt% was integrated into linear low density polyethylene (LLDPE) by employing melt compounding technique at 160 °C to produce flexible composite films. The LLDPE/GNP nanocomposite films were irradiated with doses up to 50 kGy using a 2.5 MeV electron beam accelerator in air at ambient temperature. The uniform distribution of GNP in the thermoplastic matrix obtained from FESEM analysis improved the samples' mechanical characteristics. As the GNP concentration in the LLDPE matrix increases, both the thermal stability and impermeability qualities (oxygen and water vapor) get significantly improved. Electron beam irradiation of film samples further enhances the physico-mechanical, thermal and gas barrier properties compared to non-irradiated composite films and neat LLDPE film. The tighter connections between graphene and LLDPE chains as well as the development of cross-linked networks by E-beam irradiation are responsible for the improved performance properties. Therefore, GNP incorporation as well as electron beam irradiation of thermoplastic nanocomposite films could be a viable alternative for producing high-performance and high-barrier flexible LLDPE/GNP composite films for packaging applications. • Combine effects of GNP addition and electron beam irradiation on properties of LLDPE composite films. • The fabricated flexible composite films irradiated up to the dose of 50 kGy. • The E-beam irradiated samples improved mechanical, thermal and barrier properties. • These irradiated, and high-barrier composite films for flexible packaging materials. [ABSTRACT FROM AUTHOR]

Most of the synthetic polymers that are used for packaging industry come from fossil fuel; thus, when their life cycle is complete, they normally accumulate in the environment. The poly(3-hydroxybutyrate) is a biopolymer produced from bacteria; due to its microbial degradation, great attention has been paid to its research; nevertheless, it has been found to be necessary to improve its mechanical, thermal and barrier properties. One of the approaches to do so is the incorporation of inorganic compounds. Zirconium oxide (ZrO2) and zirconium hydroxide (Zr(OH)4) have outstanding thermal stability and are potential compounds for the improvement in PHB features. Along this study, hybrid films made of PHB with 0.01, 0.05 and 0.1 mass% of ZrO2 and Zr(OH)4 were produced; their properties were evaluated by TG and DSC, which permitted to observe that all the composites have improved thermal resistance; furthermore, 0.01 and 0.05% Zr(OH)4 showed lower Wc. These results suggest that zirconium-based PHB composites can increase the process temperature range, which opens the new door to future applications on food packaging. [ABSTRACT FROM AUTHOR]

A non-equimolar multicomponent perovskite of Zn 0.1 Ca 0.1 Sr 0.4 Ba 0.4 ZrO 3 is successfully synthesized. Its single-phase stabilization is achieved by the designed non-equimolar composition that contributes to the nearly zero mixing enthalpy, the high configuration entropy and the moderate atomic difference. Its chemical bonds inhomogeneity is revealed, which contributes to the unique mechanical and thermal properties of Zn 0.1 Ca 0.1 Sr 0.4 Ba 0.4 ZrO 3. Its Young's modulus is 185.7 GPa and tends to be the average of its components'. The thermal conductivity of Zn 0.1 Ca 0.1 Sr 0.4 Ba 0.4 ZrO 3 ranges from 1.45 to 1.87 W/(m·K), being lower than those of its components (CaZrO 3 and BaZrO 3) and the typical low thermal conductivity material Y 2 O 3 partially stabilized ZrO 2. The low thermal conductivities suggest its potential as thermal barrier materials and this work is supposed to arouse future works on the non-equimolar multicomponent ceramics with targeted performances. [ABSTRACT FROM AUTHOR]

Epoxy composites doped with different content of graphene nanoplatelets (GNPs) and/or carbon nanotubes (CNTs) have been manufactured. Their chemical, thermal, electrical, and mechanical behaviors have been studied, evaluating also their performance as coatings of glass fiber composite substrates. It is confirmed that the graphitic nanofillers present different efficiency as nanofillers as a function of their geometry. CNTs are much higher efficient electrical nanofillers than graphene, but an important synergetic effect is determined in the electrical conductivity of hybrid GNP/CNT/epoxy composites. In contrast, the thermal conductivity scarcely depends on the geometry of graphitic nanofillers but on the graphitic nanofiller content. Adding up to 12 wt% GNP and 1 wt% CNT, the thermal conductivity of the epoxy resin can be increased more than 300%. GNP presents high efficiency to increase the barrier properties, reducing the water absorption up to 30%. The stiffness of nanocomposites proportionally increases with graphitic addition, up to 50%, regard to the modulus of the neat epoxy resin. The adherence of coatings over glass fiber composite substrates increases by nanofiller addition due to the nanomechanical anchoring. However, the water uptake induces a higher weakening on nanodoped composites due to the preferential water absorption by the interface. [ABSTRACT FROM AUTHOR]

The properties of the mixtures of fatty acids obtained by adding different concentrations of cocoa butter (CB) to a pectin matrix (PEC) were studied. The influence of the CB concentration on the optical properties, mechanical properties, barrier properties, surface properties, microstructure and thermal stability of pectin polysaccharide films were determined. The addition of the CB affected the main properties of the films, with the mechanical strength, transparency and water absorption being reduced. The addition of CB led to opaque films with a heterogeneous microstructure, resulting in an increase in the film opacity. The surface hydrophilicity of the PEC films was reduced following the addition of the CB. The degree of the PEC crystallinity increased with the addition of the butter, making the PEC/CB films more thermally stable and shiny. The new materials obtained present great potential to produce edible films or coatings for moisture-sensitive food applications. [ABSTRACT FROM AUTHOR]

High-density polyethylene (HDPE)/carbon filler composites for potential applications in food tray packaging were prepared by melt compounding HDPE with one-dimensional (1D)-multiwalled carbon nanotubes (MWCNT), two-dimensional (2D)-graphene oxide (GO) and three-dimensional (3D)-carbon black (CB) on a twin-screw extruder. The morphology of fillers inside the HDPE matrix was characterized and correlated to the mechanical, thermal and barrier properties of the nanocomposites. The results showed the distinct effect of CB on the mechanical, thermal and barrier properties of HDPE from MWCNT and GO. The morphological analysis revealed uniform dispersion for all the fillers, but the agglomerate formation was a lot more evident in MWCNT-based nanocomposites. Ball milling solved the large agglomerate formation for MWCNT and produced nanocomposites with improved mechanical properties. In comparison to 1D and 2D nanofillers, the 3D-CB filler showed remarkable contribution to tensile toughness but caused a reduction in barrier properties of HDPE, the increase in tensile toughness was attributed to uniform dispersion of the filler, enhanced mechanical interlocking between filler and polymer, appearance of high degree of crazing on tested samples and increase in nanocomposite internal temperature during tensile testing. [ABSTRACT FROM AUTHOR]

The mechanical properties and fire resistance of vinyl ester resin (VER) composites containing cage‐shaped octaphenyl silsesquioxane (OPS), incompletely cage‐shaped phenyl silsesquioxane (PhT7POSS), and ladder‐shaped phenyl silsesquioxane (PPSQ) were investigated. The POSS structure and dispersion have a great influence on the mechanical properties, thermal stability, and decomposition process of VER composites. The bending strength at break and modulus of the VER‐POSS composites were enhanced obviously, especially for VER‐PPSQ composite and VER‐OPS composite, respectively. In addition, PhT7POSS‐based VER composites revealed the lower values of the peak heat release rate, total heat release, and total smoke release in cone calorimetry tests due to the formation of dense carbon/silica protective layers that acted as a barrier to heat and mass transfer. Moreover, the flame‐retardant mechanisms of condensed phase and gas phase were also investigated in detail. These results illustrate VERs modified by OPS, PhT7POSS, and PPSQ are providing an applicable method to fabricate the composites with excellent flame‐retardant and mechanical properties. [ABSTRACT FROM AUTHOR]

The binding of donor‐acceptor Stenhouse adducts (DASAs) bearing hydrogen‐bond recognition groups by Hamilton‐type receptors significantly influenced their photoswitching properties by altering thermal barriers to isomerization. The thermal barrier between the most stable linear isomer and the photogenerated isomer is lowered on binding to a receptor, and this barrier is crucial for switching properties. The thermal isomerization was shown to proceed via a stepwise linear‐enol‐keto mechanism in DMSO where the tautomerisation barrier is within 2 kJ ⋅ mol−1 of that of the rate‐determining step, which may be important for analyzing switching properties. [ABSTRACT FROM AUTHOR]

Thermal barrier coating (TBC) system is an essential technology in many fields associated to high temperatures. The main function of these TBCs is to protect the metallic parts against high temperatures over 1000 °C. However, degradation occurs both in thermal and mechanical performances during service. Thus, understanding the underlying degradation and failure mechanisms of TBCs is significant to assess and further enhance the durability and reliability of TBCs. Regarding the durability of TBCs, this paper reviews different failures mechanisms of TBCs caused by residual stresses, phase transformations, sintering, hot corrosion attack and oxidation. Subsequently, some methods are summarized to alleviate the undesirable effects of the causes, so as to extend the lifetime of TBCs. Regarding the thermal barrier performance of TBCs, the neoteric advances to resist degradation in thermal conductivity of TBCs are reviewed. In addition, some new ceramic materials with superior intrinsic properties are introduced for ultra-high temperature applications. In brief, this review correlates the microstructure and properties of TBCs for finer interpretation and degradation-resistant design on their thermal and mechanical properties, which would benefit the advanced TBCs in future engineering applications. [ABSTRACT FROM AUTHOR]

Polymer nanocomposite based on layered structure such as graphene, MoS2, MoO3 and WS2 has become an active field of research due to their exceptional thermal, mechanical and electrical properties. Achieving uniform dispersion of layered nanostructures within the polymer matrix is challenging because of the agglomeration of nanostructures which occurs due to the Van der Waals attraction and the cohesive nature between the two phases. In this work, we report the preparation of PVDF-modified MoS2 nanocomposites by the solvent blending method. The XRD results reveal the interaction of the negatively charged surface of MoS2 sheets and the positive CH2 group of PVDF through the predomination of β-phase. Morphological observation through SEM suggests the MoS2 induced formation of nanofibres in the composite. Enhancement in the thermal stability of the nanocomposite is observed and is possibly due to the heat barrier by the exfoliated MoS2 which in turn supports the tortuous effect. The DSC of the PVDF-modified MoS2 composite indicates the domination of β-phase and the hindrance to crystallization of PVDF. Improvement in the mechanical strength of the composites was also noticed on higher filler concentration. [ABSTRACT FROM AUTHOR]

This paper details the application of the finite element model, Bayesian regularized neural network, and genetic algorithm for metallic thermal protection system parameter optimization. The object is to minimize the structure weight and satisfy multiple performance constraints which consist of the deformation of the top face sheet, the stress around the lug hole, the stress of the honeycomb core, and the inner temperature. Firstly, a high-fidelity thermo-mechanical coupled finite element model was established to investigate the thermal and mechanical properties of the metallic thermal protection system. Then, surrogate models were constructed based on the Bayesian regularized neural network which assigns a probabilistic nature to the network weights and biases and allows the network automatically and optimally penalize complex models. To guarantee full exploration of the design space, an optimal orthogonal-maximin Latin hypercube design was adopted and modified to generate preliminary sampling points. Finally, an approach for genetic algorithm constraint handling, stochastic ranking, was introduced and modified by multiple constraint ranking to handle constraints. In addition, a sensitivity analysis was performed to disclose the effects of individual design variables on the thermal and mechanical responses. The results indicate that the structure mass is decreased by 41.2 % when compared to the initial design and all the constraints are satisfied. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO)-based zein nanocomposite films with superior mechanical, barrier and thermal properties were fabricated by incorporating GO nanoparticles into corn protein zein (Z), through the solvent casting process. The study offers a mechanistic understanding of the effect of graphene oxide nanofiller on the physicochemical properties of zein. TEM of the zein–graphene oxide (Z–GO) nanocomposites showed uniform dispersion of GO sheets up to 1%GO loading. Mechanisms for Z–GO nanocomposite formation through covalent and noncovalent bonding are developed based on FTIR, FT-Raman and DSC results. At only 3% loading, the Young's modulus of a nanocomposite film increased by 300% and tensile strength increased by 80%. The increases in mechanical property improvements are accompanied by surface roughness increases as indicated by AFM studies. Even though GO is hydrophilic, the Z–GO nanocomposite films showed hydrophobic tendencies. The amount and degree of exfoliation of GO as well as the relative orientation of GO nanoparticles within the zein film all play an important role in the physical property changes of the film. The films became less permeable with increasing amounts of GO addition, as shown by water vapor permeability tests. GO increased thermal stability as shown by TGA. [ABSTRACT FROM AUTHOR]

In this study, the influence of nanosilica (SiO2 NPs) on the mechanical, thermal and barrier properties of poly(butylene adipate-co-terephthalate) (PBAT) nanocomposites was investigated. The PBAT/SiO2 composites were prepared by solution blending technique. PBAT/SiO2 composites were prepared with different percentages of nano-SiO2 loading (1, 3, 5, 7 and 10 wt%). The relations of SiO2 NPs with PBAT matrix were analyzed by Fourier transform infrared spectroscopy. The mechanical properties such as tensile strength, % of elongation at break, tensile modulus and thickness were determined. The thermal properties such as thermo-gravimetric analysis were analyzed for the nanocomposites. The PBAT/SiO2 composites exhibit high mechanical and thermal performance than the pure PBAT. The nanocomposites were also investigated through scanning electron microscope (SEM) and transmission electron microscope micrographs to examine the morphology between PBAT and SiO2 NPs. In addition, the results of SEM acquired are in SiO2 agreement with the data resulting from FTIR and tensile strength of the nanocomposites. The nanocomposite shows improvement in mechanical and thermal stability than that of pure PBAT. [ABSTRACT FROM AUTHOR]

Thermal protective clothings are produced from multilayered textile materials. Fabric layers need to allow enough evaporation of perspiration, ventilation, and also thermal protection from fire. This study aimed to evaluate the effects of different fabric layers and their different combinations on the thermal properties of multilayered fabric samples. Three-layered fabric combinations were created using two types of outer shell fabrics, four types of moisture barrier fabrics with membrane, and two types of thermal barrier fabrics. Sixteen different fabric combinations that simulate three-layered thermal protective clothing were studied. As a result of the study, it was found that thermal and moisture comfort properties were significantly affected by different fabric layers. [ABSTRACT FROM AUTHOR]

The thermal diffusivity of vapor deposited thermal barrier coatings is measured using an all-optical approach. The method combines CO2 laser heating of the coating surface with detection of the temperature variation in the laser induced Cr3+ luminescence signal from the thermally grown oxide (TGO) formed under the coating during service. The thermal diffusivity is determined from the delay between a surface heating laser pulse and the heating of the TGO. Data analysis is performed using a three layer heat equation model. Various locations on several coatings were investigated with different average heating laser powers and modulation frequencies. The normalized standard deviation was found to be of the order of 20%, which is thought to be largely due to localized variations in coating thickness and density. The advantage of the method described here is that it does not require knowledge of either the thermal properties of the alloy, its temperature, or thickness, and is therefore well suited for measurement on coated parts of complex shape, such as a hot section gas turbine blade. [ABSTRACT FROM AUTHOR]

AZ91 Mg alloy has a wide range of applications in the automotive industry, although its use is restricted to powertrain applications due to its low creep resistance. In this study, the effect of the micro arc oxidation (MAO) coating on the creep resistance of an AZ91 Mg alloy was investigated to take advantage of the coating layer with high thermal insulation properties. In this context, the MAO process was applied to AZ91 Mg alloy using a bipolar pulsed DC power supply. The creep tests were conducted at different temperatures (150–200 °C) and stresses (25–90 MPa) for the bare and coated samples, and the minimum creep rates were determined. It has been shown that the MAO coating reduces the creep rate of the bare alloy by 35%–84% depending on the temperature and the stress due to the stress-reducing effect and thermal barrier properties of the MAO coating. Based on the calculated creep activation energy and stress exponents, creep mechanisms were proposed for the bare and coated alloys. Effective activation energy was also calculated and lattice diffusion-controlled dislocation climb was determined to be the effective creep mechanism for both samples at lower stresses, while pipe diffusion-controlled dislocation climb was effective at higher stresses. • Creep resistance of AZ91 alloy increased with the MAO coatings. • The minimum creep rates of the bare alloy were reduced by 35%–84% when MAO coating was applied. • MAO coatings decreased stress on AZ91 substrate by 28%. • Lattice and pipe diffusion controlled dislocation climb are the main mechanisms for low and high stresses, respectively. • MAO coatings remained intact after the creep tests owing to the thermal shock resistance of the coatings. [ABSTRACT FROM AUTHOR]