Sintering kinetics of ZrO2 nanopowders modified by group IV elements

The sintering behavior of tetragonal zirconia nanopowders modified by the group IV elements at the initial sintering stage was investigated. It was found that different additives SiO₂, SnO₂, and GeO₂ have a significant influence on the densification kinetics of 3Y-TZP nanopowders obtained by coprecipitation during sintering as it depends on the amount of additives (0-5 wt%). The shrinkage of zirconia-based specimens during the nonisothermal sintering was analyzed using the dilatometric data. The constant rate of heating technique was applied in order to determine the dominant mass transfer mechanism at the initial stage of sintering in modified zirconia nanopowders. It was found that there was a change in the mass transfer mechanism and diffusion activation energy in 3Y-TZP as a result of the additives. The dominant sintering mechanism in 3Y-TZP changed from the volume diffusion to the grain boundary diffusion due to the addition of SiO₂ and SnO₂ and the sintering activation energy increased in these cases. However, GeO₂ additive activated the viscous flow mechanism in sintering process of 3Y-TZP nanopowders which led to acceleration of the densification due to the decrease in the diffusion activation energy.     

Study of trifluoromethane dissociation within wide pressure and temperature ranges by molecular resonance absorption spectroscopy

The concentration of CF₂ produced via trifluoromethane, CF₃H, dissociation behind reflected shock waves is measured by molecular resonance absorption spectroscopy method within wide ranges of CF₃H concentrations, temperatures, and pressures (38 ≤ n[CF₃H] ≤ 27000 ppm, 1180 ≤ T ≤ 2780 K, and P = 1.5–18 bar). The heat release of CF₂ radical formation in trifluoromethane pyrolysis is experimentally determined. We analyze the experimental data obtained at low and high pressures and find the normalization factor for the best coincidence of those data. We determine the activation energy E _a at low and high pressures and obtain the generalized activation energy E _a for all the experimental data.     

Experimental Determination of the Compressibility Factor of Natural Gas: Methods and Results

Measurement Techniques - The article discusses the applicability of the equations of state for the gas phase of natural gas at temperatures below 250 K. To tackle this problem, highly accurate...     

Lattice parameter of PbTe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cl<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> solid solutions

The lattice parameter of PbTe_1?x Cl _x solid solutions is shown to be a nonmonotonic function of chlorine content, with a minimum at x = 0.005. The results are interpreted in terms of a self-compensation model.     

Fatigue strength prediction of KhN73MBTYu-VD alloy compressor disks

System investigations were made of laws governing the mechanisms of formation of the complex of surface layer properties and the fatigue strength of interslot flanges of compressor disks made of KhN73MBTYu-VD alloy for different methods and modes of surface treatment finishing. Linear regression relationships were obtained for the hardening coefficient allowing one to select rational methods and modes of surface treatment finishing to predict disk fatigue strength with account of the main factors affecting the fatigue strength. Translated from Problemy Prochnosti, No. 4, pp. 125–131, July–August, 1999.     

烧结温度对Q235钢搪瓷涂层组织结构及性能影响

通过一次涂搪法在 Q235 低碳钢表面制备出 700 ~ 900 ℃ 烧结的搪瓷涂层。 采用 XRD、SEM、EDS、显微维氏硬度计、落球装置及电化学工作站研究了涂层物相组成、组织形貌、微区成分、机械性能及腐蚀行为。 结果表明:搪瓷涂层在烧结过程中表面孔隙率持续减小,截面孔隙率则先减小后增大再减小;磨加物石英逐渐溶解在涂层硅氧四面体 [SiO₄ ]网络中,使涂层显微硬度和光泽度提高;涂层与基体界面处氧化层逐渐减小并最终消失,而 Fe 扩散区逐渐扩大并形成富含 Fe-Co 和 Fe-Ni 枝晶的密着层;涂层表面釉质层形成及内部腐蚀通道的闭合使其耐腐蚀性能显著提高。     

Enamel coatings mill additives optimization for sulfuric acid corrosion

Different mill additives were optimized to improve enamel coatings anti sulfuric corrosion, the immersive corrosion behaviors in 30 wt. % H₂SO₄ solution for 120 days of the above enamel coatings were investigated by X-ray diffraction, scanning electron microscope-energy dispersive spectrometer, laser scanning confocal microscope, Raman spectra, open-circuit potential, and electrochemical impedance spectroscopy techniques. Results showed that the enamel coating with 12 wt. % quartz mill additives presents the best corrosion resistance. The mill additives significantly reduced the porosity, increased the silicon–oxygen network density, enhanced the gel passivation layer formation ability of enamel coatings, increased the alkaline oxide content, and prevented the ion exchange within the sulfuric acid solution.