Thermal Stability of Silica-Zirconia Membranes

The thermal stability, phase transformation, surface morphology, pore size distribution and permeation of the defect-free silica-zirconia membrane were investigated by using X-ray diffraction （XRD）, atomic force microscopy （AFM）, gas adsorption analyzer （BET）, and gas permeation apparatus, respectively. Using silica as the stabilizing agent, the defect-free membrane was much more stable than pure zirconia. The crystal transformation of zirconia in the silica-stabilized membrane could be prohibited by the interaction between silica and zireonia. ZrO2 crystals were kept tetragonal below 900℃, the size of which did not change with temperature between 700℃ and 900℃. It was further verified by the AFM observation, pore size analysis and permeation study. This thermal stability makes the silica-zirconia membrane a good choice as the intermediate layer for zeolite and Pd-based membranes.     

Mechanism of the Initial Stage of Thermal Decomposition of Nitroguanidine

A theoretical and experimental study of the thermal decomposition of nitroguanidine(NQ) has been carried out. Various thermolysis channels were studied by quantum chemistry methods at the CCSD(or DLPNO-CCSD) level using the aug-cc-pVDZ basis set. It is shown that the lowest activation enthalpies(170—180kJ/mol) are characteristic of the reactions of NO₂ abstraction from the initial NQ and the reaction channel with the transfer of oxygen from the nitro group to carbon in the limiting st...     

Thermal Properties of Carbon Nanotube–Copper Composites for Thermal Management Applications

Carbon nanotube–copper (CNT/Cu) composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS) technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.     

Thermal Stabilities and the Thermal Degradation Kinetics of Poly(ε-Caprolactone)

The thermal degradation behavior of poly(ε-caprolactone) (PCL) in nitrogen atmosphere was investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) techniques and Fourier Transform Infrared (FTIR) spectroscopy. TGA/DTG/DSC curves display only one main degradation step. TGA/FTIR results indicate PCL decomposes into CO₂ and hexanoic acid before 500°C. The activation energies were estimated by iterative isoconversional procedure. Friedman plot indicates a change in degradation mechanism. The differential method and integral method were used to confirm the exact kinetic mechanism. The best models are Dn (n = 1, 2, 3, and 4) when 0.08≤a≤0.2 and R2 when 0.25≤a≤0.8.     

Thermal Impedance of Rectangular Microwave Oven Linings

Amodel was preseted for calcultaing the thermal impedance of the insulation and refractory linings of rectangular microwave ovens,of which the oven cavity‘s dimensions are relatively small,while the linings re relatively thick.     

Thermal shock properties of β-sialon ceramics

An indentation–quench method based on Vickers cracks for measuring thermal-shock properties has been applied to β-sialon materials. The thermal-shock properties have been correlated with the morphology of the β-sialon grains, the z value in the β-sialon solid solution Si_6−zAl_zO_zN_8−z and the amount of residual intergranular glass phase. z Values in the range 0.6–3.0 were tested, and the amount of residual yttrium-containing glass phase was varied between 0 and 20 vol.%. The best thermal-shock resistance was found at low z values, and was further improved by adding an intergranular glass phase. The poorest resistance to thermal shock was found for the highest z value where the presence of glass had no measurable influence. One composition (z=1.5, 10 vol.% glass) was selected for studying the influence of the microstructure on the thermal-shock properties. The microstructure was varied by applying different sintering conditions. An improvement of the thermal-shock properties and the fracture toughness was found in samples containing elongated β-sialon grains formed in situ. In general, in-situ reinforced β-sialon materials with low z values and containing an intergranular glass phase exhibited the best thermal-shock resistance and improved fracture toughness (K_1c>4 MPa m^{$\text{1}\text{2}$}).     

Thermal Parametric Pumping of Air–-SO2

Abstract

The separation of air-SO₂ mixtures in a specially prepared silica gel column has been accomplished using a direct mode thermal parapump. The effect of the number of cycles, pumping cycle time, and operating temperature range and level on the extent of separation has been studied over a wide range of operating conditions. The separation factors obtained were several orders of magnitude greater than those typically reported in the literature for gas-solid systems, and compare favorably with those obtained in liquid-solid systems.     

Pro-Oxidant Effects of β-Carotene During Thermal Oxidation of Edible Oils

β-Carotene is one of the most important fat soluble pigments with well-known antioxidant and pro-vitamin A activity. It is used in industries as a food colorant and a source of vitamin A. The thermal induced degradation during processing of wide varieties of carotenoid-rich foods leads to color and properties losses. The thermal stability of edible oils is thus of great importance to food manufacturers. Corn oil, rapeseed, and sunflower oils were fortified with 50–300 μg/g of β-carotene and oxidized using a Rancimat apparatus (air flow rate 20 L/h) at 110 °C for 14 h. β-Carotene degradation was measured using high performance thin layer chromatography and confirmed by HPLC–DAD–MS. Triacylglycerols and polar compounds (PC) were determined using LC–ESI–MS. Results showed that most of the β-carotene was degraded during the first 5 h of the thermal oxidation. It was found that the addition of β-carotene produces significant effects (P < 0.05) on the peroxide index, free fatty acid values and radical scavenging activity of the three oils. Triacylglycerols containing high amounts of oleic acid show higher stability toward thermal oxidation and β-carotene treatment. Among the oils, rapeseed oil was the most stable oil in terms of the formation of polar compounds (PC), followed by corn oil, while sunflower oil was more prone to oxidation and thus higher amounts of PC were formed.     

Thermal decomposition of some poly(β-hydroxyalkanoates)

The thermal decomposition of some polyhydroxyalkanoates (PHA) has been investigated by means of thermogravimetry and differential thermogravimetry. The thermal stability of the studied polyesters decreases slightly with increasing hydroxyvalerate (HV) comonomer. This result is different from those reported in the literature. Other results agree with reaction mechanisms proposed in the literature. The data from dynamic thermogravimetric experiments are consistent with a first order reaction, as would be expected from the reaction mechanism. Infrared spectra of the thermally degraded and undegraded copolymers are evidence of the cis-elimination mechanism. © 1999 Society of Chemical Industry     

Refractory Material ——Determination of Thermal Expansion-Push Rod Method

GB/T 7320·1 -20001 ScopeThis standard specifies thermal expansion testmethod of refractories by push rod method.This standard is applicable to determination of lin-ear expansion or mean linear expansion coefficient ofrefractories over the range from room temperature to1300℃.Note: The temperature range can be extended to1500℃ if the condition is feasible.2 Referenced documentsThe following standards contain provisions, whichthrough reference in this text, constitute provisions ofthis stand…     

Thermal Shock Resistance of Bauxite-based β-Sialon Bonded Corundum Materials

Thermal shock resistant properties of reaction sintered bauxite-based β-Sialon bonded corundum have been investigated, and the results are compared with those of Al2 03 based counterpart. It is found they all have very good thermal shock resistance. Their residual strength ratios after one thermal shock cycle at AT=1200℃ and AT=1350℃ are61% -73% and53% -65% respectively. Their critical temperature difference(TSR) is 600℃-800℃. TSR parameters are calculated based on thermal expansion, modulus of elasticity,and fracture toughness determined. The reasons for improving TSR of these composite materials are discussed.Key words: Thermal shock resistance, Bauxitebased, Sialon, Corundum     

Study on Drying Organic Sludges by Thermal Jet Dryer—Part 1: Drying Performance of Thermal Jet Dryer

The authors are developing a thermal jet dryer (TJD), with a vertical disc-shaped drying tank, for the purpose of weight and volume reduction of solid wastes with high water content, such as organic sludges. In order to obtain the drying performance of TJD, drying experiments using three kinds of solid wastes were carried out. The following results were obtained: (1) Drying performance depended most on the disintegration characteristics of sample. (2) There was little influence of the samples' properties on the gas–solid multiphase flow in the tank. (3) There was a critical feed rate at which the drying performance changed drastically.     

Numerical Study of the Problem of Thermal Ignition in a Thick‐Walled Container

A problem of thermal ignition of an exothermic mixture with an inert filler in a thickwalled container is formulated. It was found that synthesis can be performed under conditions of a weakly changing temperature if an inert filler is added to the mixture. Variation of critical conditions separating different thermal regimes with different values of model parameters is examined: ignition and extinction or ignition and slow transformation.     

Thermal Decomposition of 2,4‐Dinitrobenzofuroxan and Some of Its Compounds with Metal Hydroxides

The kinetic regularities of the thermal decomposition of 2,4dinitrobenzofuroxan and its adducts with K, Na, and Cu hydroxides were studied. The variation in the reaction rate during the transformation and the relationship between the decomposition kinetics and the degree of filling of the vessel with the substance, the state of aggregation, and temperature were established. Possible mechanisms of the chemical reactions are considered on the basis of the kinetic data obtained, the compositions of gaseous and some condensed decomposition products, and an analysis of the element mass balance between the starting substance and products.     

Entropy Similarity of the Thermal Diffusion Properties of a Nitrogen–Argon Gas Mixture

The molecular thermal diffusion characteristics of a frozen nitrogen–argon binary gas mixture at normal pressure are calculated by the entropy similarity method over wide ranges of temperature and concentration. The calculated results agree satisfactorily with experimental data.     

Phase Composition and Thermal Expansion of CaO Stabilised ZrO2 Refactories

In this,phase compsition and thermal expansion behaviour of CaO Stabilised refractories were studied,Special attention was paid to the expasion behaviour of three materials with different phase composition,The research results indicated that the expansion behaviour could be improved by modifying the stabilization of ZrO2,which thus leads to the increase in the thermal shock resistance and possibly eroion resistace of as-obtained CaO stabilised ZrO material.