Linear Thermal Expansion Coefficient Research Articles

Synthesis and properties of modified thermoplastic polyimide films with good dielectric properties at high frequency and enhanced thermal stability via incorporation of rigid ester and biphenyl structural units

AbstractA series of ester‐ and fluoro‐containing thermoplastic polyimide (PI) films, PEsI‐1 ~ PEsI‐4 have been prepared by the two‐step thermal imidization procedure via the soluble poly(amic acid) (PEsAA) precursors from the copolymerization of four monomers, including the dianhydrides of bisphenol A dibenzoate‐3,3′,4,4′‐tetracarboxylic acid dianhydride (TMBPA) and 3,3′, 4,4′‐biphenyl tetracarboxylic acid dianhydride (BPDA) and the diamine monomers of 4‐aminophenyl‐4′‐ aminobenzoate (APAB) and 2,2′‐bis(trifluoromethyl)‐4,4′‐diamino biphenyl (TFMB) in the polar aprotic solvent of N‐methyl‐2‐pyrrolidinone (NMP). The PI films obtained from the high‐temperature dehydration of the PEsAA solutions exhibited the good thermal stabilities with the glass transition temperatures (Tg) over 269°C, the 5% weight loss temperatures (T5%) higher than 480°C, and the linear coefficients of thermal expansion (CTE) values in the range of 17.7 × 10−6/K–33.6 × 10−6/K in the temperature range of 50–250°C. Meanwhile, the PI films showed good thermoplasticity in the dynamic mechanical analysis (DMA) tests, in which the storage modulus of the PI films dropped sharply in the temperature range of glass transition of the polymers. At last, the PI films exhibited the good dielectric properties with the breakdown voltages (Vb) over 5200 V, the dielectric strength (Ds) higher than 210 V/μm, the dielectric constants (Dk) in the range of 3.26 ~ 3.32 at the frequency of 10 GHz, and the dielectric dissipation factors (Df) of 0.0038 ~ 0.0047. Compared with the commonly used PEsI‐ref film for high‐frequency flexible copper clad laminates (FCCL), the currently developed PI films exhibited the obviously increased Tg values, decreased CTE values, and comparable dielectric properties.

Thermal expansion coefficient of ScN(111) thin films grown on Si(111) determined by X-ray diffraction

Scandium nitride (ScN) has emerged as a promising material in various fields due to its exceptional characteristics, including high mechanical strength, hardness, high melting point, high thermal stability, and wide bandgap. This work investigates the thermal behavior of ScN by the measurement of its coefficient of linear thermal expansion (TEC). A (111)-oriented ScN thin film on a (111)-oriented Si substrate is used for the measurements. The lattice parameter is determined using x-ray diffraction, and in situ measurements are performed at elevated temperatures of up to 923 K. The expansion of the material with increasing temperature is modeled using Debye's phonon dispersion. The fitted lattice parameters are used to calculate the TEC, which we measured to be (6.61±0.60)×10−6 K−1 at 300 K. Thus, the value is 1.37×10−6 K−1 lower than the value published by Tahri et al. [J. Phys.: Condens. Matter 24, 035401 (2011)]. who simulated the TEC for a ScN bulk crystal. This work contributes to the knowledge on thermal properties of ScN and paves the way for further research in this field.

Temperature Coefficient of Electronic Polarizability in Thin Polymer Films Deposited on Si and SiO2 Substrates Determined via Spectroscopic Ellipsometry

Ellipsometry is widely used to determine the thermo-optical properties of thin polymer films. However, if the thermo-optic coefficient (TOC) and the linear thermal expansion coefficient (LTEC) are to be used to determine the temperature coefficient of electronic polarizability (TCEP) in thin polymer films, their values must be determined with the greatest possible accuracy, as both have the opposite effect. In this article, we analyze changes in ellipsometric parameters resulting from changes in the thin film temperature in order to develop a data analysis method for temperature-dependent spectroscopic ellipsometry that will facilitate the accurate determination of thermo-optical parameters, including the TCEP, in polymer thin films. As practical application examples, we identified optimal spectral windows to accurately determine the thermo-optical parameters of 50 to 150 nm-thick PMMA thin films deposited on Si and SiO2 substrates. The influence of thin-film thickness on the accuracy of TOC and LTEC determination is discussed.

Preparation and Properties of Atomic-Oxygen Resistant Polyimide Films Based on Multi-Ring Fluoro-Containing Dianhydride and Phosphorus-Containing Diamine.

Colorless and transparent polyimide (CPI) films with good atomic oxygen (AO) resistance and high thermal endurance are highly required in low earth orbit (LEO) space exploration. Conventional CPI films based on fluoro-containing 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) have been widely used in space applications. However, the AO erosion yields and glass transition temperatures (Tg) of the 6FDA-based CPI films have to be modified in order to meet the severe serving environments. In the current work, novel CPI films based on a multi-ring fluoro-containing 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylicdianhydride (6FCDA) monomer were developed. In order to enhance the AO resistance of the derived CPI film, a phosphorus-containing aromatic diamine, 2,5-bis[(4-aminophenoxy)phenyl]diphenylphosphine oxide (BADPO) was used to polymerize with the dianhydride to create the organo-soluble resin. Then, two phosphorus-containing CPI films (PPI), including PPI-1 (6FDA-BADPO) and PPI-2 (6FCDA-BADPO) were prepared by thermally curing of the PPI solutions at elevated temperatures. The PPI films maintained good optical transparency with transmittance values over 80% at a wavelength of 450 nm. PPI-2 exhibited a Tg value of 311.0 °C by differential scanning calorimetry (DSC) measurement, which was 46.7 °C higher than that of the PPI-1 counterpart (Tg = 264.3 °C). In addition, the PPI-2 film showed a coefficient of linear thermal expansion (CTE) value of 41.7 × 10-6/K in the range of 50~250 °C, which was apparently lower than that of the PPI-1 sample (CTE = 49.2 × 10-6/K). Lastly, both of the two PPI films exhibited good AO resistance with the erosion yields (Ey) of 6.99 × 10-25 cm3/atom for PPI-1 and 7.23 × 10-25 cm3/atom for PPI-2 at an exposure flux of 5.0 × 1020 atoms/cm2. The Ey values of the current PPI films were obviously lower than that of the standard polyimide (PI) film based on pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) (Ey = 3.0 × 10-24 cm3/atom).

Diborides of Multielement Transition Metals: Methods for Calculating Physical and Mechanical Characteristics

From the first principles simulation (using the method of “a priori pseudopotential” and the “quasi-harmonic approximation” method- author’s developments), the basic characteristics of diborides and diborides of multielement transition metals (DMTMs) with an AlB2 type structure were calculated. For both diborides and DMTMs, the linear coefficients of thermal expansion (LCTE) along the axial axes differ little from each other, i.e., transition metal diborides and hexagonal lattice DMTMs are quasi-isotropic. Quasi-isotropy makes it possible to estimate the LCTE using an analytical formula that depends on the melting temperature. In the absence of experimental data on the melting point of DMTMs, a method for calculating it from first principles is presented. The theoretical hardness values of transition metal diborides and DMTMs with averaged parameters were calculated from the first principles. The hardness of both bulk and nano-sized DMTMs was assessed using a hybrid method. There is agreement between the calculated and available experimental data.

Synthesis, thermal expansion and optical properties of ZrV2O7 thin films

Cubic ZrV2O7 thin films have been synthesized by sol-gel spin-coating method. The influences of annealing temperatures on the phase composition and morphology of ZrV2O7 thin films were investigated using XRD, SEM, and EDX. Negative thermal expansion (NTE) and optical performances of cubic ZrV2O7 thin films were analyzed using variable temperature XRD and UV–Vis spectroscopy. Results indicate that as-deposited ZrV2O7 thin films have an amorphous structure with smooth and dense surface. Cubic ZrV2O7 thin films were prepared after heat treatment at 720 °C for 1 h. It was found that the thin films contained V2O5 impurity with the Zr: V = 1:2 precursor solution. Pure cubic ZrV2O7 thin films were fabricated with the Zr: V = 1.75:2 precursor solution. Cubic ZrV2O7 thin films show isotropic NTE in the temperature range of 100–700 °C. The coefficients of thermal expansion (CTEs) of ZrV2O7 films along the a, b, and c axes are −6.88 × 10−6 °C−1, and the volumetric and linear CTEs are −20.56 × 10−6 °C−1 and -6.85 × 10−6 °C−1, respectively. The transmittance of cubic ZrV2O7 thin film is approximately 80 %.

Сравнительный анализ термоупругих характеристик керамоматричных композиционных материалов, определенных по различным модельным представлениям структурно фазового состава матричного материала

A comparative analysis of thermoelastic characteristics of ceramic matrix composite materials (CMC) obtained by liquid and gas phase technologies, reinforced with two types of carbon fibers (CF), is carried out based on different model structural phase composition of the obtained matrix material. It is noted that when implementing the liquid phase siliconizing and using high modulus carbon fibers with high negative values of the absolute value of the coefficients of linear thermal expansion (CLTE), a simplified model of the matrix material consisting of only one SiC phase can be correctly used. When implementing PIP and CVI technologies, CMC with low modulus CF and CF with low negative CLTE values show the greatest sensitivity to an increase in matrix porosity. For CMC based on CF T800, the change in the longitudinal CLTE was about 66% with a porosity of 20%. An increase in porosity leads to a decrease in all elastic characteristics of the CMC, to the greatest extent for the transverse modulus of elasticity and the shear modulus.

THERMOMECHANICAL DEFORMATION OF CARBON NANOTUBES IN POLYMER MATRIXES

Annotation: A theoretical study of the effects of nucleation of intrastructural thermal stresses in polymer materials reinforced with carbon nanotubes, caused by thermomechanical incompatibility of materials, was performed. Differential equations of its thermoelastic interaction with epoxy, polyamide, phenol-formaldehyde, polyester, polycarbonate, polystyrene, and polypropylene media in uniform and non-uniform temperature fields were constructed on the basis of modeling of a nanotube with an elastic cylindrical shell with aggregated values of thickness, modulus of elasticity, Poisson's ratio, and coefficient of linear thermal expansion. The solutions of these equations are found in closed form. The distribution functions of thermal stresses in the matrix medium and thermal forces in the nanotube wall are constructed. It was demonstrated that the thermal stresses in the matrix medium have the form of concentrators on the interface surface between the phases of the system and decrease inversely proportional to the square of the distance to the axis of the nanotube. It is shown that the intensities of these thermal stresses increase with increasing incompatibility of the thermomechanical parameters of the system phases.

Analysis of the thermal expansion coefficient of glass- and carbon-fibre-reinforced composites

With the development of manufacturing processes, an increase in the importance of metal-fibre composites in materials engineering is observed. These are materials consisting of appropriately arranged layers of metal and various types of fibres. The very wide use of composite materials in the construction of machine and equipment components means they are often exposed to work in variable temperature conditions. The aim of this article was analysis of the thermal expansion of typical composites: carbon fibre-reinforced polymer, glass fibre-reinforced polymer, glass-reinforced aluminium laminate and carbon-fibre reinforced aluminium laminate. EN AW-6060 aluminium alloy was used as the reference material. The aim of the dilatometric tests was to determine the coefficient of thermal expansion and the dimensional stability of composite materials at elevated temperatures up to 100 °C. The EN AW-6060 aluminium alloy was characterized by the highest linear expansion coefficient (20.27×10−6 1/K). Composites containing glass fibres were characterized by the lowest positive linear thermal expansion coefficient. Among the composite materials tested, CARALLs exhibit the lowest thermal expansion coefficient.

Using the zirconium­containing binders for obtaining refractory concretes

Now the creation of new heat­resistance and refractory binding materials contributing towards reliable and durable service of high­temperature plants is paid great attention. To develop the physical and chemical principles of such materials technology first of all it is necessary to study the high­melting oxide systems and as a consequence, to obtain refractory products in terms of ones. Taking into consideration all mentioned above, the multicomponent zirconium­oxide systems are of potential interest.
 As a result of our investigations new compositions of high­strength, heat­resistance, and refractory zirconium­containing binders on the basis of different sections of the quaternary system CaO—Al2O3—ZrO2—SiO2 are obtained. Refractory concretes in terms of zirconium­containing cement and various aggregates, both natural (corundum, baddeleyite) and artificial (calcium zirconate), have been elaborated. It is revealed that the kind and granulometric composition of aggregates, molding methods, as well as cement­aggregate relation influence the physical and mechanical properties of concrete developed. Concretes obtained are characterized by high strength (50—60 MPa) and service property stability: refractoriness — more than 1700 °C thermal shock resistance — more than 30 cycles; thermal linear expansion coefficient — 4.8×10–6 ÷ 5.6×10–6 deg.–1, initial strain point under load of 0.2 MPa — 1400—1500 °C Materials developed comply with requirements to refractory materials and can be applied for monolithic linings of heat density parts of high­temperature plants.

BaO, ZnO, B2O3, PbO, and SiC effects on phosphorescent afterglow damping and thermal stability of SrAl2O4 base pigments at industrial glazes

Phosphorescent glazes are usually used in direction signs of emergency routes. That is why afterglow damping and thermal stability of phosphorescent pigments are the most decisive factors of phosphorescent glazes. This study aims to choose a suitable glaze to enhance the time and intensity of the afterglow. For this reason, the effects of BaO, ZnO, B2O3, and PbO additives on the afterglow intensity and lifetime of reference industrial glaze containing SrAl2O4 phosphorescent material were investigated. 5, 7, 10, 15, and 20 %wt SrAl2O4 phosphorescence powder was mixed with base industrial glaze to recognize the optimum component. Samples were fired at 1040 °C for 40 min in the same conditions and then were analyzed by photoluminescence spectroscopy. Results showed that increasing the SrAl2O4 proportion increased samples afterglow damping time, and 10 %wt SrAl2O4 was chosen as the optimum amount. Also, BaO is more efficient for increasing the intensity and afterglow lifetime. Moreover, 0.02, 0.03, 0.05, and 0.1 %wt SiC were added to the reference industrial glaze containing 10 %wt SrAl2O4 to investigate the reduction firing conditions on the glaze afterglow. Increasing the SiC ratio up to 0.02 %wt increased the afterglow lifetime from 5 ± 0.4 to 27 ± 1.7 min, but the afterglow intensity was decreased. Despite this, adding 0.03, 0.05, and 0.1 %wt SiC darkened the glaze and reduced the intensity and afterglow lifetime. The sample containing 0.1 %wt SiC did not melt properly, and this sample did not have any afterglow. Furthermore, the temperature required for firing affects the afterglow of the samples. On the other hand, to investigate the effect of temperature, the base industrial glaze containing 10 %wt SrAl2O4 was fired at 1040, 1120, and 1140 °C to determine thermal stability. The sample fired at 1140 °C had almost no phosphorescent afterglow. Also, dilatometry tests at the temperature of 600 °C and hot-stage microscope analysis were performed to determine the linear coefficient of thermal expansion and the melting point of the samples, respectively. The results showed the linear coefficient of thermal expansion of the industrial glaze with 10 %wt SrAl2O4 was 73.3 × 10−7 1/°C, and it could be changed between 58.5 × 10−7 1/°C by adding 10 %wt B2O3 to 73.5 × 10−7 1/°C by adding 10 %wt BaO. The melting point of the pure industrial glaze was 1130 °C, and adding 10 %wt, SrAl2O4 decreased it to 1076 °C. Also, by adding 10 %wt BaO, ZnO, B2O3, and PbO to phosphorescent glaze, melting point was obtained 1128 °C, 1020 °C, 1030 °C, and 974 °C respectively. The same sample with 0.02 %wt SiC melted at 1154 °C.

Thermal Expansion of Polypropylene Part II: Depression of In‐Plane Linear Thermal Expansion of Polypropylene by Elastomer Incorporation and Elucidation of Its Mechanism Through Temperature‐Variable X‐ray Scattering

AbstractIn this study, the in‐plane linear thermal expansion behaviors from −20 °C to 100 °C along the flow direction (FD) for injection molded isotactic homo polypropylene (hPP) and their elastomer blends are thoroughly investigated. The elastomers used in this study are two different poly(ethylene‐co‐octene)(EO) thermoplastic elastomers which have the same density but different melt flow rate (MFR), 5.0 and 30 (dg/10 min). Thus, the blends are designated as hPP‐EO5.0 having the EO with 5.0 of MFR and hPP‐EO30 having the EO with 30 of MFR. It is found that from −20 °C to 40 °C, the linear thermal expansion profiles for neat hPP, hPP‐EO5.0, and hPP‐EO30 overlapped, indicating that with or without the EO, their linear thermal expansions proceeded under the same mechanism. On the other hand, above 40 °C, their thermal expansion behaviors greatly changed; the linear thermal expansions of hPP‐EO5.0 and hPP‐EO30 are suppressed to be much lower than that of neat hPP. The morphological observation by a transmission electron microscope (TEM) reveals that the shapes of the EO domains in the blend systems are found to be elongated along the FD. Thus, it would be expected that the suppressed linear thermal expansions of the hPP‐EO blends are attributed to the suppression of the linear thermal expansions of the hPP amorphous layers in the lamellae due to the retraction of the elongated EO domains caused due to the instability of the interfacial tension at elevated temperatures. Yet, temperature variable small‐angle X‐ray scattering (SAXS) results reveal that the linear thermal expansions of the hPP amorphous layers in the EO blends, on the contrary, increase. One of the plausible mechanisms is proposed to elucidate seemingly contradictory phenomenon that the EO blends have their suppressed bulk linear thermal expansions while enhanced linear thermal expansions of the hPP amorphous layers. Finally, the suitable elastomer design for low coefficient of linear thermal expansion (CLTE) PP is proposed.

Preparation and characterization of colorless and transparent semi‐alicyclic fluoro‐containing polyimide nanocomposite films with enhanced high‐temperature dimensional stability via incorporation of colloidal silica nanofillers

AbstractColorless and transparent semi‐alicyclic fluoro‐containing polyimide (PI) nanocomposite films with enhanced high‐temperature dimensional stability and sustained optical transparency were designed and prepared via incorporation of nano‐sized colloidal silica (SiO2) fillers into the PI matrix derived from hydrogenated pyromellitic dianhydride (HPMDA) and 2,2′‐bis[(4‐aminophenoxy)phenyl]hexafluoropropane (BDAF). The derived PI composite films, abbreviated as 6FCPI‐X in which X stands for the weight percent of the SiO2 in the composite films, exhibited superior thermal and comparable optical properties to the pristine 6FCPI‐0 (6FDA‐BDAF) matrix film. For example, as for the thermal properties, 6FCPI‐35 composite film showed a glass transition temperature (Tg) of 279.1°C and a residual weight ratio at 750°C (Rw750) of 66.1%, which were apparently higher than those of 6FCPI‐0 matrix (Tg = 272.2°C; Rw750 = 47.1%). More importantly, the 6FCPI/SiO2 nanocomposite films showed obviously lower linear coefficients of thermal expansion (CTE) values as compared with that of the 6FCPI‐0 matrix. 6FCPI‐35 composite film showed a CTE value of 36.1 × 10−6/K in the temperature range of 50–250°C, which was lower than half of that of the 6FCPI‐0 matrix (CTE = 77.9 × 10−6/K) in the same range of temperature. In addition, incorporation of nano‐sized colloidal SiO2 particles basically maintained the intrinsically good optical properties of the pristine 6FCPI‐0 matrix film. 6FCPI‐35 composite film showed the optical transmittances of 81.7%, 85.3%, and 87.2% at the wavelength of 400 nm (T400), 450 nm (T450), and 500 nm (T500), respectively, which were in the same level with those of the 6FCPI‐0 film (T400 = 84.0%; T450 = 86.3%; T500 = 87.6%). The 6FCPI series of nanocomposite films also exhibited similar CIE Lab color parameters, including the yellow indices (b*) lower than 2.0 and haze values lower than 1.0%.

Thermal Physical Properties of Metals in a Quasi-Two-Phase Model

Abstract—The applicability of the model of a two-phase locally equilibrium region for calculating the temperature dependences of heat capacities, linear thermal expansion coefficients, and thermal diffusivities of various metals is demonstrated. It is shown that the proposed relations make it possible to describe the increase in the thermal characteristic with increasing temperature and its changes associated with the implementation of the phase transition. The possibility of extrapolating the established dependences to experimentally unexplored areas is indicated. The relative simplicity of the established relationships, a certain universality of the model in describing various solids, and the visibility of the theoretical results obtained give hope for the use of the model in engineering and technical calculations.

Effect of calcium aluminate-based additive on properties of periclase-carbon refractories for steelteeming ladles

Premature decommissioning of steel-teeming ladle lining due to critical localized damage, whichi significantly reduces the functional properties of the lining, is one of the most acute problems in modern metallurgy. The main type of products used for steel-teeming ladle lining is periclase-carbon. In order to improve corrosion resistance and resistance to thermomechanical loads, additional additives, such as spinel, and high alumina CMA cement, are introduced into the periclase-carbon products. In this paper, the effect of calcium aluminate-based additive on the properties of periclasecarbon refractories is investigated. It is assumed that there is a potential for the formation of magnesium aluminate spinel (MA) in periclase-carbon products with calcium-aluminate additives during heat treatment. Fused periclase was used as the raw material, the carbon component was represented by natural flake graphite in an amount of 10 wt% and a combined binder. An additive based on calcium aluminates was introduced, with a fractional size from 0 to 3 mm, while the amount of main fractions of fused periclase was reduced by the corresponding amount of the additive introduced. The compressive strength, apparent porosity, and bending strength values before and after coking firing were analyzed. The thermal coefficient of linear expansion, phase composition and microstructure of the products were also investigated.

Magnet selection for permanent magnet synchronous machines by decision science

This work investigates magnet selection for permanent magnet synchronous machines (PMSMs) by decision science. 20 multiple-attribute decision-making (MADM) methods ranked a list of 45 industrial-grade permanent magnets based on eight property requirements―high energy density (BHMAX), high coercivity (HC), high magnetic remanence (BR), high electrical resistivity (ρ), high Curie temperature (TC), high maximum service temperature (TS), low linear thermal expansion coefficient (α), and low density (d)―targeted to selecting magnets for PMSMs. The Shannon's entropy method evaluated the objective attribute weights of ρ, BHMAX, and HC, as ∼46%, ∼24%, and ∼23%, respectively, and the rest—BR, TC, TS, d, and α―combined as ∼7%; equal weights (∼12.5% each) to all the attributes were the subjective weights. Principal component analysis (PCA) consolidated ranks from various MADM methods, and hierarchical clustering (HC) grouped magnets based on their similarities. For PMSMs in applications where ρ, BHMAX, and HC, are more critical compared to the rest of the properties, the eight top-ranked magnets are N35 (Neodymium® 35), N35H (Neodymium® 35H), N30 (Neodymium® 30), N30H (Neodymium® 30H), N27H (Neodymium® 27H), N27 (Neodymium® 27), F5–S (Ferrite 5, Sintered Iron Strontium Oxide), and F3–S (Ferrite 3, Sintered Iron Barium Oxide) in that order. On the other hand, for PMSMs in applications where all the attributes are equally important, the eight top-ranked magnets are N35 (Neodymium® 35), N35H (Neodymium® 35H), N30H (Neodymium® 30H), N30 (Neodymium® 30), N27H (Neodymium® 27H), N27 (Neodymium® 27), CS4 (Samarium Cobalt 4), and F5–S (Ferrite 5, Sintered Iron Strontium Oxide) in that order. The consolidated ranks of the magnets obtained by assigning objective and subjective attribute weights showed a strong correlation of ∼0.94. This investigation targeted magnet selection for PMSMs from a comprehensive dataset of industrial-grade permanent magnets, utilizing several property requirements, applying both objective and subjective attribute weights identified Neodymium® 35 as the top-ranked magnet.

DFT based computational investigations of the physical properties of perovskites-structure SrXO3 (X = Si, Tb, Th) for optoelectronic and thermo-mechanical applications

Density Functional Theory (DFT) method is employed for investigating the structural, elastic, electronic, optical, and thermal properties of Perovskite structure SrXO3 (X = Si, Tb, and Th). The studied lattice parameters show good agreement with the previous theoretical and experimental results. The elastic stiffness constants, (Cij) of SrSiO3, SrTbO3, and SrThO3 satisfied the born stability criteria which confirm the mechanical stability of these phases. It is observed that when Tb or Th is replaced with Si, the brittleness behaviours of SrTbO3 or SrThO3 change to ductility, which improves its machinability for industrial applications. The investigation of anisotropic factors of SrSiO3, SrTbO3, and SrThO3 ensured that SrSiO3 is more anisotropic than SrTbO3 and SrThO3. By evaluating the electronic properties, it can be advantageous for applying the topological insulators (TI), solar cells, or PV (Photovoltaic) cell fabrication. Furthermore, the optical properties are studied and detail discussed with SrXO3 (X = Si, Tb, and Th). The reason of low Debye temperature (ΘD) and low minimum thermal conductivity (Kmin) has been perfectly explicated through the consideration of the mean atomic weight (M/n) of the compounds. Temperature-dependent of heat capacities (Cv, Cp) and linear thermal expansion coefficient (α) are also estimated using the quasi-harmonic Debye model and discussed. The SrTbO3 and SrThO3 compounds can be employed as potential thermal barrier coating (TBC) materials for high-temperature applications, according to the low values of Kmin, ΘD and α.

Exploration of novel structures and related physical properties of Fe2Pt ordered alloys

The Fe–Pt phase diagram suggests the possible existence of ordered Fe2Pt structures, however, the ordered structures of Fe2Pt and related physical properties are unclear until now. In this work, four new low-energy ferromagnetic Fe2Pt ordered structures are predicted based on the particle swarm optimization algorithm. Their structural stability is verified by the formation enthalpy, mechanical stability and lattice dynamic stability. The order of the thermodynamic stability is Cmcm > Immm > I4/mmm > P3¯m1. All four structures are dynamically (except tetragonal I4/mmm structure) and mechanically stable. The fundamental physical properties including magnetic, elastic, phonon and thermal properties are investigated in detail. Their total magnetic moments, as well as the bulk modulus are almost the same. The shear modulus and Young's modulus of Cmcm structure are close to the P3¯m1, and larger than that of other two structures. The order of the elastic anisotropy is Immm > P3¯m1 > I4/mmm > Cmcm. The orthorhombic Immm structure can be regarded as a distorted tetragonal I4/mmm structure, and the distortion effectively improves the physical properties of the I4/mmm structure. The thermal properties at finite temperatures show that the trigonal P3¯m1 structure is more suitable for high-temperature applications compared to other structures. The results of linear thermal expansion coefficient indicate that anisotropy order of thermal expansion is Immm > I4/mmm > Cmcm > P3¯m1. More interesting is the discovery of the Invar effect along the y-axis direction in orthorhombic Immm structure.

Tool material selection methodology for aircraft elements design

The technology and technological equipment selection have to be substantiating for the modern materials for product the aircraft construction elements from polymer composition. The physical and technical characteristics of the material, ensuring the required accuracy of manufacturing equipment, as well as economic feasibility are the main criteria for choosing the material of technological equipment. The material equipment choosing is depends on the polymer composite construction technology manufacturing. The methodic of rigging materials selection for aircraft constriction elements production from polymer composition by vacuum infusion is considered in that paper. The results of a comparative analysis of typical materials equipment used in production are presented are considered in that paper. It is shown that the main criteria for a comparative analysis are: temperature, resistance to solvents, resistance to mechanical stress; maintainability; the value of the coefficient of linear thermal expansion; the stability of the geometry of the equipment and its tightness. It was showing that the metals and carbon fiber composite are the most appropriate for equipment manufacture that used in high temperature processes manufacturing composite components. The materials equipment algorithm choosing for polymer composite components manufacturing is considered in that paper. It is noted that the same material have to be choosing for equipment manufacturing as the carbon fiber or fiberglass polymer composite component. This allows to ensure the same CLTE, which is important in hot forming of the composite component, and to eliminate warping of the composite component during its cooling on the equipment. However, the equipment gelcoat processing has to be taking into account for specified accuracy achievement. The quantitative assessment of the economic feasibility of material equipment choosing is considered in that paper. It is shown that only a combination of technical, technological and economic factors makes it possible to substantiate the expediency of the rigging material used for the specific production of aircraft construction elements.

Surface properties of 1T-TaS2 and contrasting its electron-phonon coupling with TlBiTe2 from helium atom scattering.

We present a detailed helium atom scattering study of the charge-density wave (CDW) system and transition metal dichalcogenide 1T-TaS2. In terms of energy dissipation, we determine the electron-phonon (e-ph) coupling, a quantity that is at the heart of conventional superconductivity and may even "drive" phase transitions such as CDWs. The e-ph coupling of TaS2 in the commensurate CDW phase (λ = 0.59 ± 0.12) is compared with measurements of the topo-logical insulator TlBiTe2 (λ = 0.09 ± 0.01). Furthermore, by means of elastic He diffraction and resonance/interference effects in He scattering, the thermal expansion of the surface lattice, the surface step height, and the three-dimensional atom-surface interaction potential are determined including the electronic corrugation of 1T-TaS2. The linear thermal expansion coefficient is similar to that of other transition-metal dichalcogenides. The He-TaS2 interaction is best described by a corrugated Morse potential with a relatively large well depth and supports a large number of bound states, comparable to the surface of Bi2Se3, and the surface electronic corrugation of 1T-TaS2 is similar to the ones found for semimetal surfaces.