电化学氧化法制取烟酸的研究进展

介绍了直接电氧化法和间接电氧化法制取烟酸的原料及相应的电极反应,同时对直接电氧化法制取烟酸的电解槽、电极材料、离子交换膜及支持电解质等的研究进展进行了评述。直接电氧化法多采用Pt、PbO2和PbO2/Ti为阳极,Pb和Ni为阴极,离子交换膜为隔膜,电流效率可达70%。     

纳米氧化硅-氧化铝负载氧化物催化氧化甲醛

采用溶胶-凝胶法制备了纳米氧化硅-氧化铝材料,并利用浸渍法将氧化物负载在该纳米材料上。研究了室温环境下,纳米氧化硅-氧化铝材料负载氧化物去除甲醛的效果。结果表明了相比其他氧化物,负载MnO2的催化材料去除甲醛的效果最好;当负载量为3%左右时,效果最好。     

常温下碳基活性材料催化氧化NO的研究进展

针对常温、含高浓度O₂ 的NO污染气体排放控制,典型的选择性催化还原（SCR）技术已不再适用。以碳基活性材料为催化剂的NO常温催化氧化技术得到了广泛关注,该技术在常温和高浓度O₂条件下将NO氧化为NO₂,并以硝酸或硝酸盐形式加以回收利用,因此具有环保和经济双重效益,应用前景广阔。本文简要综述了碳基活性材料常温催化氧化NO的研究进展,阐述了NO催化氧化机理,介绍了碳基活性材料的表面物化特性和反应条件（O₂浓度、NO浓度、GHSV、反应温度、水蒸气和催化剂粒径等）对催化氧化NO的影响,以及活性炭、活性炭纤维、碳纳米纤维、炭干凝胶、金属负载碳基活性材料、炭化污泥等不同碳基活性材料的催化特性,总结并展望了未来碳基活性材料低温催化氧化NO的发展方向。     

Corrosion of silicon nitride materials in gas turbine environment

In the present study the corrosion behavior of various silicon nitride materials will be presented. Hot gas tests were conducted in an atmosphere similar to that in a gas turbine (high temperature, pressure and flow rate and the water vapor pressure as the corrosive component). While some materials displayed a high degree of microstructural stability, all materials suffered surface degradation during the rig test. The oxidation surface layer of mainly SiO₂, which is essential for the oxidation protection of nonoxide materials because it induces a passive, diffusion-controlled oxidation mechanism, was found to be degraded by evaporation processes involving volatile silicon hydroxides. As the mechanism of these processes a combination of linear oxidation and corrosion was proposed. The stabilization of the protective oxidation layer of silica should be considered as the main factor in stabilizing these materials in hot gas environments. This can be achieved by environmental barrier coatings (EBC), however their long-term stability was found to be still insufficient.     

Antioxidant Coating of SEN for Thin Slab Con-casting

The SEN for thin slab con-casting is easy to break and damage because of the oxidation during preheating and application. The enamel coating material is generally applied on the surface of SEN to avoid the oxidation. The coating material with born glass and silicon as main starting materials and silica sol as binder was studied. ZrO2 - C and Al2O3 - C materials containing 15% carbon were isostatic pressed, and heated at 600 ℃ , 900 ℃ , 1 200 ℃ , 1 500 ℃ for 2 h, respectively. The results show that the coating material with 70% of boron glass and 30% of silicon bonded by silica sol can form denser protection layer in the above mentioned materials at the range of 600 -1 500 ℃. The oxidation area ratio and weight loss ratio with the coating are much lower than those without the coating.     

三元层状结构MAX相陶瓷材料的制备技术及其研究发展现状和发展趋势

三元层状结构陶瓷材料主要是指M_n+1AX_n相,三元层状结构MAX相陶瓷材料具有金属的特性还具有陶瓷的特性,三元层状结构MAX相陶瓷材料具有较高的力学性能,良好的耐磨损性能和良好的耐腐蚀性能,并具有良好的抗高温氧化性能等,还具有良好的可加工性能。三元层状结构MAX相陶瓷材料主要有Ti₃SiC₂,Ti₄SiC₃,Ti₃AlC₂,Ti₂AlC,Ti₄AlN₃和Ti₂AlN等。本文主要叙述三元层状结构MAX相陶瓷材料的制备技术,物相组成,显微结构,力学性能和耐磨损性能,耐腐蚀性能和抗高温氧化性能以及其他性能等。并叙述三元层状结构MAX相陶瓷材料的研究发展现状和发展趋势。并对三元层状结构MAX相陶瓷材料的未来研究发展趋势和发展方向进行分析和预测。     

氧化铈基HCl氧化循环制Cl2催化剂研究进展

氯化氢催化氧化技术在副产氯化氢的处理和利用方面有着巨大的应用价值和良好的工业前景。CeO₂基催化剂因其廉价、不易烧结及抗氯化性能优良等诸多优点,被认为是目前最具有应用前景的氯化氢氧化催化剂之一。本文简要地介绍了氯化氢氧化制氯循环工艺,评述了近年来用于氯化氢氧化反应的CeO₂基催化材料,包括CeO₂催化剂、掺杂改性CeO₂催化剂以及CeO₂作助催化剂等。同时在文中还对CeO₂基材料催化HCl氧化的表面反应机理进行阐述。最后结合目前的研究现状,对如何进一步提升CeO₂基催化HCl氧化的反应活性进行了展望。     

硼对炭材料氧化行为的综合效应

综述了硼在炭材料中的抗氧化机理，并阐述了炭材料在氧化过程中的行为。硼对炭材料的氧化反应具有催化作用和保护作用的双重特征。     

Reaction Kinetics in the Hydrothermal Oxidation of Hf

The hydrothermal oxidation of Hf was studied using metal powders and chips to change the surface-area effect. Fine monoclinic HfO₂ powders (32 to 34 nm) were formed through two parallel reaction paths, one the oxidation of Hf with H₂O and the other the consecutive reaction via formation of Hf hydride. Based on the experimental results at 500°C under 100 MPa, three reaction rate constants were determined for two kinds of starting materials. The relative widths of two paths were proved to be independent of the size of starting materials, and the pulverization and oxidation of both metal powders and chips could be explained by the same mechanism, where the formation of hydride was a driving force in pulverization.     

Oxidation and creep behavior of textured Ti2AlC and Ti3AlC2

The oxidation and creep behaviors of textured Ti₂AlC and Ti₃AlC₂ ceramics were characterized. The oxidation behavior of the two materials, which was studied in air at temperatures ranging from1000 to 1300 °C, was observed to be anisotropic and the materials exhibited a better oxidation resistance along a direction transverse to the c-axis. The correlation between the overall parabolic rate constant and oxidation temperature of both textured materials was characterized, providing new insights into the oxidation kinetics. The results indicate that the texturing has a negligible influence on the creep behavior in the assessed temperature range of 1000?1200 °C in air, for the applied stresses ranging from 40 to 80 MPa. In this stress regime, the creep behavior of textured Ti₂AlC and Ti₃AlC₂ appears to be controlled by grain boundary sliding. This behavior can be rationalized based on a model for superplastic deformation, indicating pure-shear motion under stationary conditions accommodated by lattice or grain-boundary diffusion.     

气体中微量甲醛的脱除研究进展

主要阐述了去除甲醛气体的常用材料（吸附材料、催化氧化材料、光催化降解材料和生物技术材料）的研究进展,文中指出碳基材料、分子筛、有机金属骨架常常被用作吸附挥发性有机气体,它们具备丰富的孔道结构和较大的比表面积,碳基材料和分子筛表面存在大量丰富的基团能够有效地增大甲醛的吸附容量,提高甲醛的吸附效率;有机金属骨架表面的金属与甲醛结合成键,有效提高材料的化学吸附;以金属氧化物为载体的材料常被用作催化氧化甲醛分子,将甲醛分子转化为无毒性的二氧化碳和水;半导体材料TiO₂常被用作光催化降解材料去除甲醛;除此之外还有一些利用生物技术来去除甲醛气体。本文对比了不同材料去除甲醛的优劣性,对不同的去除材料改性研究进行了归纳总结。     

三氧化二铝-碳化硅-碳浇注料防氧化技术研究进展

综述了三氧化二铝-碳化硅-碳浇注料防氧化技术的防氧化效果以及对材料性能、组成和结构的影响,根据含碳耐火材料的氧化损毁机理,主要分析了防氧化剂的两种作用形式即优先碳源氧化法和优化碳源法。防氧化剂法除了优先碳源氧化生成金属氧化物和碳化物阻止含碳材料的氧化外,还可以通过固相反应生成液相等物质堵塞材料内部气孔提升材料的致密度阻止氧气的进入来提高防氧化效果,优化碳源法则通过复合碳源以及在碳源的表面添加涂层达到一定的防氧化效果。详细阐述了3种方法的工艺特点以及目前存在的问题,并对其发展方向进行了展望,为开发新型三氧化二铝-碳化硅-碳浇注料防氧化技术提供参考。     

液相化学氧化表面处理的研究进展

分别以无机型、有机型以及化学氧化聚合型3种化学氧化处理液分类介绍了液相化学氧化处理在材料表面处理方面的应用，并对液相化学氧化处理在处理表面隋性有机材料和含碳材料方面的研究进展进行了综述。     

炭材料的高温抗氧化性研究进展

介绍了炭材料的氧化过程,综述了国内外目前提高炭材料抗氧化性能的两个主要途径;基体改性技术和涂层技术。重点阐述了抗氧化涂层的基本要求,涂层的制备方法以及各涂层体系,提出了对于炭材料高温抗氧化性研究方面的一些认识,阐明了其发展前景。     

Spherical activated carbon as an enhanced support for TiO2/AC photocatalysts

Titanium dioxide nanoparticles prepared in situ by sol–gel method were supported on a spherical activated carbon to prepare TiO₂/AC hybrid photocatalysts for the oxidation of gaseous organic compounds. Additionally, a granular activated carbon was studied for comparison purposes. In both types of TiO₂/AC composites the effect of different variables (i.e., the thermal treatment conditions used during the preparation of these materials) and the UV-light wavelength used during photocatalytic oxidation were analyzed. The prepared materials were deeply characterized (by gas adsorption, TGA, XRD, SEM and photocatalytic propene oxidation). The obtained results show that the carbon support has an important effect on the properties of the deposited TiO₂ and, therefore, on the photocatalytic activity of the resulting TiO₂/AC composites. Thus, the hybrid materials prepared over the spherical activated carbon show better results than those prepared over the granular one; a good TiO₂ coverage with a high crystallinity of the deposited titanium dioxide, which just needs an air oxidation treatment at low-moderate temperature (350–375 °C) to present high photoactivity, without the need of additional inert atmosphere treatments. Additionally, these materials are more active at 365 nm than at 257.7 nm UV radiation, opening the possibility of using solar light for this application.     

薄板坯连铸用浸入式水口的性能与使用

针对薄板坯连铸用浸入式水口的使用条件,选择了水口不同部位的材质。以板状刚玉、氧化铝粉、锆莫来石、电熔稳定氧化锆、电熔镁砂、天然鳞片状石墨等为原料制备了浸入式水口,重点研究水口本体铝碳材料的抗氧化性能和渣线锆碳材料的抗侵蚀性能,并模拟现场使用条件进行了烘烤试验。结果表明:所研制的水口材料性能完全满足使用要求,烘烤时无氧化和剥落;在薄板坯实际连铸生产条件下,所研制的浸入式水口稳定地实现了24炉连浇,为相关的浸入式水口研究提供了良好的基础。     

逆反应烧结制备碳化硅/氮化硅复合材料的工艺

制备Si3N4／SiC复合材料的常规反应烧结是以Si和SiC为原料进行氮化烧结,而逆反应烧结是以Si3N4和SiC为原料,首先使Si3N4反向反应为活性氧化物后再进行烧结。建立逆反应烧结工艺制备Si3N4／SiC复合材料的热力学基础。确定了Si3N4先于SiC氧化;氧化产物可以是SiO2,也可以是Si2N2O;形成的SiO2氧化膜不会与基体材料反应;在膜与基体之间可能生成Si2N2O。论证了逆反应烧结的热力学可行性。通过6个烧结实验,证实了其热力学分析的正确性,并从工艺参数与密度变化、残氮率和比强度等关系筛选出最佳的烧结工艺参数。     

Oxidation resistance of B6O-materials with different additives

The oxidation resistance of B₆O materials with and without Y₂O₃/Al₂O₃ additives and a typical cBN material were analysed in dry and wet air using TG measurements for up to 10 h and static experiments in a muffle furnace for up to 50 h. The results showed that the oxidation of the materials is sensitive to the composition of the atmosphere. In wet air with 17 vol.% H₂O a weight loss was measured for all materials. In dry air a parabolic increase of the mass and a formation of a glassy surface layer were observed for the B₆O materials whereas the cBN-material is characterized by the formation of a mostly crystalline layer.The oxidation resistance is the lowest for the pure B₆O and the highest for the investigated cBN material.     

Oxidation behavior of carbon materials derived from a carborane- and silicon-incorporated polymer

The oxidation behavior and oxidation mechanism of carbon materials containing silicon and boron elements (C–Si–B materials) were investigated at different high temperatures in air. The carbon materials were prepared by oxidative pyrolysis of the polymer precursor, carborane-incorporated poly(dimethylsilylene-ethynylenephenyleneethynylene) (CB-PSEPE), at 800, 1000, or 1200 °C for 1 h under static air. Homogeneous dispersion of silicon and boron components in the carbon matrix could be achieved in the carbon materials after the pyrolysis. The oxidation behavior of the C–Si–B materials during the oxidation process was studied. The evolution of elemental composition and morphology of the surface layers of carbon materials was monitored by X-ray photoelectron spectroscopy and scanning electron microscopy, respectively. The results imply that the formation of protective borosilicate layer in the surface is the main mechanism to provide remarkable oxidation resistance of the carbon materials. The obtained borosilicate layer with a self-healing property can withstand oxidation at 1000 °C in air.     

Effects of Si3N4 and WC on the oxidation resistance of ZrB2/SiC ceramic tool materials

ZrB₂/SiC, ZrB₂/SiC/Si₃N₄ and ZrB₂/SiC/WC ceramic tool materials were prepared by spark plasma sintering technology, and their oxidation resistance was tested at different oxidation temperatures. When the oxidation temperature is 1300 °C, the oxide layer thickness, oxidation weight gain and flexural strength of ZrB₂/SiC/Si₃N₄ ceramic tool material after oxidation are 8.476 μm, 1.436 mg cm^?2 and 891.0 MPa, respectively. Compared with ZrB₂/SiC ceramic tool materials, the oxide layer thickness and oxidation weight gain are reduced by 8.2% and 11.8%, respectively, and the flexural strength after oxidation is increased by 116.1%. However, the addition of WC significantly reduces the oxidation resistance of the ceramic tool material. A dense oxide film is formed on the surface of ZrB₂/SiC/Si₃N₄ ceramic tool material during oxidation, which effectively prevents oxygen from entering the inside of the material, thereby improving the oxidation resistance of the ceramic tool material.