Sintering behavior and thermal expansion of zirconia–titanium composites

The dilatometric and thermogravimetric methods were used to investigate the sintering conditions of 3Y–ZrO₂ and 3Y–ZrO₂–Ti composites. For the materials preparation, the nanometric zirconia stabilized by 3 mol% Y₂O₃ powder and micrometric titanium powder (3 and 10 vol%) were used. The green body samples were formed by slip casting method. The morphology of samples microstructures was determined by SEM observations. The stereological analysis of zirconia and zirconia–titanium composites was carried out using computer program. The density was measured using the Archimedes method. The hardness of sinters was also investigated. Addition of Ti into ZrO₂ influenced the sintering behavior and thermal expansion of obtained composites. The analysis of the sintering process and characteristic temperatures confirmed the increase of onset and final temperature of shrinkage with the increase in Ti content. The changes of the thermal expansion curves for the pure zirconia and 3Y–ZrO₂–Ti composites were the result of the αTi → βTi transformation and the transition temperature of the zirconia m → t transformation. The zirconia and composite samples were characterized by relative density about 98%, close to theoretical density. The slight growth of zirconia grains was observed.     

Electrochemical characterisation of MBaCo3ZnO7+δ (M = Y,Er, Tb) as SOFC cathode material with low thermal expansion coefficient

The electrochemical oxygen activation at high temperature was studied on a new class of oxygen-store material based on the system YBaCo₄O_7+δ. Three different porous layers made of YBaCo₃ZnO_7+δ, ErBaCo₃ZnO_7+δ and TbBaCo₃ZnO_7+δ were electrochemically tested as oxygen activation coatings and showed a very promising activity. The envisaged applications for these materials are principally as SOFC cathodes and as catalytic layer on oxygen membranes. The electrochemical performance followed the order Tb ? Y > Er at any tested temperature. Area specific resistance for the best performing material (TbBaCo₃ZnO_7+δ) ranges from 30 mΩ cm² at 850 °C to 0.46 Ω cm² at 650 °C. High temperature XRD showed that the thermal expansion coefficient (25–900 °C) in air of TbBaCo₃ZnO₇ is 9.45 × 10^?6 K^?1, which evidences the good thermochemical compatibility of this cobalt-rich electrocatalyst with YSZ/GDC electrolytes.     

Structure–property relationships of novel fluorinated polycarbonate polyurethane films with high transparency and thermal stability

Research on Chemical Intermediates - Novel polycarbonate diol (PCDL) was synthesized using dimethyl carbonate, 1,5-pentanediol (1,5-PD), 1,6-hexanediol (1,6-HD) and 1,4-cyclohexanedimethanol...     

Frost-resistant polyurethane compositions with a low temperature coefficient of Young’s modulus

Single-phase and microheterogeneous unplasticized and plasticized polyurethane compositions based on oligo(diisocyanates) and their blends were synthesized. The frost resistance and temperature dependence of Young’s modulus were examined for these materials in relation to their structural organization.     

Synthesis and characterization of sol–gel derived ZrV2O7 fibers with negative thermal expansion property

Novel ZrV₂O₇ fibers with negative thermal expansion were prepared via combination of sol–gel process and thermal decomposition. The as-prepared fibers were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy and Raman spectroscopy. The results showed that the synthetic pH value had little influence on the crystal structure of products while showed significant effect on morphology. The fibers obtained at pH = 9 exhibited cylindrical morphology and its mean diameter was about 1 μm. The thermal expansion property of the as-prepared fibers was investigated by in situ XRD and thermal mechanical analyzer. All of the as-prepared fibers showed positive thermal expansion first and then negative thermal expansion, resulting from a phase transition from 3 × 3 × 3 superstructure to 1 × 1 × 1 cubic structure. The macro thermal expansion coefficients of ZrV₂O₇ ceramic rods increased with decreasing of fiber diameter. The mechanism of the phase transition was also discussed.     

Effect of clay modification on structure–property relationships and thermal degradation kinetics of β-polypropylene/clay composite materials

Journal of Thermal Analysis and Calorimetry - The influence of neat and organically modified montmorillonite on the structure–property relationships of a β-nucleated polypropylene matrix...     

Modification of mechanical and thermal property of chitosan–starch blend films

Chitosan–starch blend films (thickness 0.2 mm) of different composition were prepared by casting and their mechanical properties were studied. To improve the properties of chitosan–starch films, glycerol and mustard oil of different composition were used. Chitosan–starch films, incorporated with glycerol and mustard oil, were further modified with monomer 2-hydroxyethyl methacrylate (HEMA) using gamma radiation. The modified films showed improvement in both tensile strength and elongation at break than the pure chitosan–starch films. Water uptake of the films reduced significantly than the pure chitosan–starch film. Thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) showed that the modified films experience less thermal degradation than the pure films. Scanning electron microscopy (SEM) and FTIR were used to investigate the morphology and molecular interaction of the blend film, respectively.     

Structural and thermal behavior of polystyrene thin films using ATR–FTIR–NanoDSC measurements

Most studies report a depression of the glass transition temperature in thin polymer films. To gain insight into this behavior, we have simultaneously investigated the structure of materials and their thermal behavior by developing an ATR–FTIR–nano-differential scanning calorimeter (nanoDSC) hybrid instrument consisting of a ZnSe ATR crystal upon which the sample and a DSC-on-a-chip rests. FTIR spectra showed property changes with film thickness; nanoDSC did not. The relative absorbance of an IR peak at 797 cm⁻¹ was found to correlate with aging time in thin films, suggesting that conformational structure of thin films is critical to their thermal behavior.     

Synthesis of L10 Fe–Pd films by electrodeposition and thermal annealing

Fe–Pd alloy films have been prepared by electrochemical deposition from an alkaline electrolyte containing Fe sulfate, Pd chloride and 5-sulfosalicylic acid onto polycrystalline titanium substrates. The as-deposited films were nanocrystalline and magnetically soft (coercivity ∼ 25 Oe). L1₀ Fe–Pd films with a (1 1 1) preferred orientation were obtained by post-deposition thermal annealing of films with composition about 37 at% Fe in an (Ar + 5% H₂) gas flow at 500 °C. Such films exhibit hard magnetic properties, with a coercivity up to 1880 Oe, and a slightly anisotropic magnetic response, with a larger in-plane remanence. Preliminary magnetic investigations support magnetization switching through pinning of domain walls.     

Multistage thermal decomposition in films of cadmium chloride-doped PVA–PVP polymeric blend

Several reports exist on the use of natural-oil-based materials as rejuvenators to restore the properties of aged binders—more specifically, regarding their ability to enhance the binders’ low-temperature properties and to reduce their stiffness. Rejuvenators are typically made of low molecular weight constituents which could easily volatilize and thus render the rejuvenated binder thermally unstable. Hence, the study of the thermal stability of rejuvenated binders is of paramount importance. In this research, a binder with a performance grade (PG) of PG58-28 modified with a soybean-derived rejuvenator at 12% by mass is added to an extracted reclaimed asphalt pavement (RAP) binder at a ratio of 1:5 resulting in a rejuvenator dosage rate of 2% by total mass of binder. The PG of the rejuvenated RAP binder is determined using both dynamic shear rheometer and bending beam rheometer. The thermal stability of the rejuvenator and the binders is verified using thermogravimetric analysis (TG). The rejuvenator shows good thermal stability up to a temperature of 302 °C. The RAP binder containing the rejuvenator shows similar thermal stability to the unrejuvenated RAP binder. The evolved gases from the TG analysis are analyzed using Fourier transform infrared (FTIR) to chemically characterize the rejuvenator and the binders. The FTIR spectrum of the rejuvenator reveals characteristic peaks. The intensity of these peaks serves as an indication of the rate of mass loss of the rejuvenator within the rejuvenated RAP binder.     

Transparent conductive tungsten-doped tin oxide thin films synthesized by sol–gel technique on quartz glass substrates

Transparent conductive tungsten-doped tin oxide (SnO₂:W) thin films were synthesized on quartz glass substrates by sol–gel dip-coating method. It was found that the films were highly transparent and the average optical transmission was about 90% in the visible and near infrared region from 400 to 2,500 nm. The optical band gap is about 4.1 eV. The lowest resistivity of 5.8 × 10^?3 ohm cm was obtained, with the carrier mobility of 14.2 cm² V^?1 s^?1 and carrier concentration of 7.6 × 10¹⁹ cm^?3 in 3 at.% W-doping films annealed at 850 °C in air. The structural properties, surface morphology and chemical states for the films were investigated.     

Bacterial cellulose films with controlled microstructure–mechanical property relationships

Bacterial cellulose (BC) films with different porosities have been developed in order to obtain improved mechanical properties. After 13 days of incubation of Gluconobacter xylinum bacteria in static culture, BC pellicles have been set. BC films have been compression molded after water dispersion of BC pellicles and filtration by applying different pressures (10, 50, and 100 MPa) to obtain films with different porosities. Tensile behavior has been analyzed in order to discuss the microstructure–property relationships. Compression pressure has been found as an important parameter to control the final mechanical properties of BC films where slightly enhanced tensile strength and deformation at break are obtained increasing mold compression pressure, while modulus also increases following a nearly linear dependence upon film porosity. This behavior is related to the higher densification by increasing mold compression pressure that reduces the interfibrillar space, thus increasing the possibility of interfibrillar bonding zones. Network theories have been applied to relate film elastic properties with individual nanofiber properties.     

High transparent thermal curable hybrid polycarbonate films prepared by the sol–gel method

Polycarbonate/epoxy/silica hybrid films were prepared by curing an epoxy reaction via in situ sol–gel process. The influence of the synthetic conditions, such as the ratio of different epoxy reagents and the contents of [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane on the physical and optical properties of these hybrid films were investigated in details. The coefficient of thermal expansion, surface roughness, and light transmittance at a wavelength range from 250 to 800 nm were measured. These excellent overall performances make it a promising photonic packaging material.     

Initial dynamic thermal dissipation modes enhance heat dissipation in gold nanoparticle–polydimethylsiloxane thin films

Journal of Thermal Analysis and Calorimetry - Plasmonic nanocomposite materials have exhibited value for applications ranging from biological hyperthermia to optical sensing and waveguiding. Energy...     

Sustainable composites of surface-modified cellulose with low–melting point polyamide

The present study proposed a series of sustainable polyamide/cellulose composites with up to 60% bio-based content to address environmental issues arising from using fossil-based polymers. Furthermore, it addressed one of the most challenging cellulose/polymer composites' issues, filler/matrix compatibility. Accordingly, the microcrystalline cellulose (MCC) surface was treated through the grafting of n-octadecyl isocyanate (ODI) molecules. The elemental analysis confirmed the substitution of approximately 9 ODI molecules per 100 anhydroglucose units, resulting in superhydrophobic MCC formation with a water contact angle of 130°. The surface-modified MCC was melt blended with a bio-based low–melting point polyamide, developed through copolymerization of 11-aminoundecanoic acid and 12-aminolauric acid. Scanning electron microscopy images confirmed no evidence of surface-modified MCC agglomeration, even at a high loading of 30 wt%, suggesting a uniform dispersion of the filler particles and excellent compatibility between two phases. Consequently, the storage modulus, tensile modulus, and yield stress were enhanced by 40%, 100%, and 50%, respectively, in the composite sample with 30 wt% of MCC, proving excellent stress transformation from the matrix to particles arose from good adhesion between cellulose particles and polyamide chains. Furthermore, all samples revealed suitable melt flowability and viscoelastic performances, suggesting their excellent processability, a critical property for engineered thermoplastics. On top of that, the presence of the surface-modified particles considerably decreased water uptake capacity and water vapor transmission of the polymer matrix, making it interesting for specific applications like packaging films.     

Carbon nanotube–polyurethane shape memory nanocomposites with low trigger temperature

Ester-based polyurethane (PU) with low glass transition temperature was used to develop shape memory nanocomposites with low trigger temperature. Pristine carbon nanotubes (CNTs) and oxidized CNTs (ox-CNTs) were introduced by melt mixing to improve the mechanical and shape memory properties of the PU matrix. The dispersion of CNTs on the mechanical properties and shape memory behaviors of the nanocomposites were also investigated. The results show that better dispersion of ox-CNTs contributes to more stiffness effect below glass transition temperature (T_g) while lower storage modulus (E′) above T_g. The nanocomposites exhibit high shape fixity and recovery ratio above 98%. The ox-CNT/PU nanocomposite shows higher shape recovery ratio for the first cycle, faster recovery due to better dispersion of CNTs and have potential applications for controlling tags or proof marks in the area of frozen food. The trigger temperature can be tailored by controlling the T_g of the PU matrix or the content of the nanofillers.     

Structure and thermal properties of heterometallic complexes for chemical vapor deposition of Cu–Pd films

Novel volatile heterocomplex compounds based on copper(II) and palladium(II) fluorinated β-diketonates are studied. The crystals of the synthesized compounds are shown to be composed of 1D coordination polymers in the form of chains of alternating molecules of monometallic complexes. The crystallographic data for [Cu(hfa)₂?Pd(zif)₂] are as follows: C₂₆H₂₂F₁₈O₁₀CuPd, P2₁/c, a = 7.9947(18) Å, b = 19.277(4) Å, c = 13.609(3) Å, β = 118.298(15)°, V = 1846.7(7) ų, Z = 2, d = 1.810 g/cm³. The thermal properties of the compounds are examined by TG-DTA and vacuum sublimation. The complexes are studied as the precursors for producing copper-palladium alloy films by chemical vapor deposition. It is demonstrated that bimetallic alloy coatings with a ratio Cu/Pd = 1:1 can be prepared from [Cu(hfa)₂?Pd(zif)₂].     

Correction to: Multistage thermal decomposition in films of cadmium chloride-doped PVA–PVP polymeric blend

Core/shell composites of CuC₂O₄·2H₂O@AP and ZnC₂O₄·2H₂O@AP were prepared from metal oxalates on suspended AP particles in ethanol. CuO and ZnO nano-metal oxides as the nano-catalysts were made from CuC₂O₄·2H₂O and ZnC₂O₄·2H₂O simultaneously by thermal decomposition of AP. The particle size of CuO nano-particles was very finer, and the ZnO particles showed a considerable growth during formation. The kinetic triplet of activation energy, frequency factor, and model of thermal decomposition of pure AP, CuC₂O₄·2H₂O@AP, and ZnC₂O₄·2H₂O@AP composites were estimated by applying three model-free (FWO, KAS, and Starink) and model-fitting (Starink) methods. Based on the thermal analysis, the CuC₂O₄@AP composite has better catalytic performance and the thermal decomposition temperature of AP decreased to about 126.44 °C.