加入Al粉和Si粉对低碳MgO-Al_2O_3-C材料性能的影响

以电熔镁砂、电熔镁铝尖晶石及鳞片石墨为原料,以酚醛树脂作结合剂,在MgO-A l2O3-C材料中加入A l粉和Si粉,混练后在180 MPa压力下成型,185℃12 h热处理,制成了加入4.5%质量分数A l粉、0~3.5%质量分数Si粉的AS系列试样和同时加入2%质量分数石墨的ASC系列试样,研究了试样的常温物理性能、高温抗折强度、抗热震性及其相组成和显微结构。结果表明:(1)AS系列中,仅加入4.5%A l粉试样的高温抗折强度从未加A l粉的3.0 MPa提高到22.3 MPa,热震后抗折强度保持率从60%提高到77%;再加入1.5%Si粉后,高温抗折强度提高到27.9 MPa,热震后抗折强度保持率提高到79%;(2)加入A l粉、Si粉和石墨的ASC系列试样的高温抗折强度略高于AS系列试样的,热震后抗折强度保持率在71%~75%之间;(3)这类复合材料具有良好的热态强度和抗热震性的原因为:A l粉、Si粉在埋炭加热过程中与C、N2原位生成针状A lN和SiC等非氧化物,填充、穿插在方镁石和尖晶石骨架中,起到增强、增韧的作用。     

加入不同量Al粉和Si粉的低碳Al2O3-C滑板的高温力学性能

以板状刚玉、α-Al2O3微粉、石墨、Al粉、Si粉为原料,固定板状刚玉、α-Al2O3微粉、石墨的加入质量分数分别为85%、5%、2%,加入8%(w)不同比例的Al粉和Si粉(Al、Si质量比分别为0∶8、5∶3、3∶5和8∶0),以酚醛树脂为结合剂,制备了低碳Al2O3-C滑板,并研究了该滑板材料于1 500℃保温3 h埋石墨热处理后的热态抗折强度、应力-应变关系和抗热震性,同时分析了其物相组成和显微结构。结果表明,此低碳Al2O3-C滑板材料具有较高的高温强度和优良的抗热震性:当Al、Si质量比从0∶8变为8∶0时,材料在1 400℃的高温抗折强度从10.4 MPa增至32.4 MPa;在6.5 MPa载荷下1 400℃时的最大变形量从215μm降至90μm;1 100℃风冷热震3次后的抗折强度保持率从80%降至65%。这是由于Al、Si在使用的高温下与C、CO和N2反应生成了非氧化物Al4C3、AlN和SiC,这些非氧化物填充在刚玉骨架结构中起增强、增韧作用,有利于提高低碳Al2O3-C滑板材料的高温力学性能。     

The graphitization of carbon nanofibers produced by catalytic decomposition of methane: Synergetic effect of the inherent Ni and Si

The catalytic effect of the inherent Ni and Si on the graphitization of carbon nanofibers produced by catalytic decomposition of methane is reported. The participation of the inherent Ni and Si metals as co-catalysts in the graphitization of the carbon nanofibers through the formation of Ni₂Si and SiC was inferred. Taking advantage of this catalytic effect, graphite materials showing structural characteristics comparable to oil-derived graphites which are employed in several industrial applications have been prepared from the carbon nanofibers. Unlike SiC which is further descomposed to graphite, the role of Ni₂Si remains unclear. At the CNFs heat treatment temperatures employed, Ni₂Si is in a liquid state where the carbon can be dissolved to form a supersaturated solution from which the SiC can be produced by segregation, thus being an intermediate stage in the catalytic graphitization of the carbon nanofibers. Further work are currently in progress to go insight this issue.     

Dehydrogenation of ethylbenzene to styrene over Fe2O3/Al2O3 catalysts in the presence of carbon dioxide

An Fe₂O₃ (10 wt%)/Al₂O₃ (90 wt%) catalyst prepared by a coprecipitation method was found to be effective for dehydrogenation of ethylbenzene to produce styrene in the presence of CO₂ instead of steam used in commercial processes. The dehydrogenation of ethylbenzene over the catalyst in the presence of CO₂ was considered to proceed both via a one-step pathway and via a two-step pathway. CO₂ was found to suppress the deactivation of the catalyst during the dehydrogenation of ethylbenzene. This revised version was published online in July 2006 with corrections to the Cover Date.     

Calculation of the limit pore ranges of the reaction of porous carbon materials with CO2

In the production of activated carbon materials reaction temperature is important for the course of the chemical reaction. The higher the reaction temperature the faster the increase of the reaction rate as against the diffusion rate. In the range of small carbon burn-off reactions the decrease in k_meff values can be ascribed to a reduction of the surface area available for the reaction. Depending on the pore size distribution the surface area can be determined from the walls of the cylindrical tubes. With the help of the pore efficiency value determined from the k_meff values, the limit pore ranges for C0₂ diffusion can be calculated.     

Microstructure,mechanical property and thermal stability of diamond-like carbon coatings with Al,Cr and Si multi-doping

In this paper, AlCrSi atoms were co-doped into DLC coatings by using a high power impulse magnetron sputtering combining with an anode-layer linear ion beam. The doped AlCrSi contents were controlled via adjusting the Ar fraction in the sputtering gas mixture of Ar and C₂H₂. The influences of the AlCrSi multi-doping on the composition, microstructure, residual stress, mechanical property and tribological behavior of the as-deposited DLC coatings were studied systemically by using EDS, XPS, TEM, stress-tester, nanoindentation and ball-on-plate tribometer as a function of the Ar fraction. The thermal stability of the coatings was also researched by a vacuum heat treatment with various temperatures. The results show that the carbide former Cr preferred to form hard carbide components which were conducive to the hardness of the coatings, while the weak carbide former Al dissolved in the DLC matrix as metallic state, which can effectively released the stress of the DLC coatings. The doped Si would bond with sp²-C to form sp³ CSi, and thus maintained the sp³-C structure stability and improved the thermal stability of the coatings. Accordingly, the DLC coatings with AlCrSi multi-doping not only exhibited relatively low residual stress and high hardness, but also showed a high thermal stability over 500 °C. It was believed that the AlCrSi multi-doping may be a good way for improving the comprehensive properties of the DLC coatings.     

The formation and reaction of alkylidynes on Ni/Al2O3

Adsorption of the alkenes, ethene and propene on Ni/Al₂O₃ at 298 K gives initial formation of the corresponding alkylidyne while but-l-ene adsorption forms a mixed phase of trans and gauche butylidyne conformers. The alkylidynes are, however, unstable at this temperature and decompose to lower hydrocarbon fragments. Ethylidyne forms a surface methyl species whereas propylidyne decays to first ethylidyne and, in turn, to methyl. The two butylidynes decompose at substantially different rates forming, again, ethylidyne.     

ICP-AES有机进样法测定燃料油中铝、硅、钙、钒、铁、镍含量

采用ICP-AES有机进样法测定燃料油中铝、硅、钙、钒、铁、镍元素。采用航空煤油为稀释剂,按照油/溶剂(质量比)1/9加以稀释后直接进入ICP-AES(电感耦合等离子体发射光谱)仪器测定。方法检出限:钒为0.5μg/g,硅为1μg/g,铝、镍为0.2μg/g,铁、钙为0.05μg/g;相对标准偏差<5%;回收率在88.4%～109.8%之间;与无机灰化-碱熔法(IP 501/05)测定的结果进行了比对,结果基本一致。     

铝粉、硅粉加入比例对Al_2O_3-ZrO_2-C材料力学性能的影响

在A l2O3-ZrO2-C材料中加入总质量分数为5%的铝粉和硅粉,改变试样中铝粉和硅粉的质量比(分别为0:1、1:4、2:3和4:1),经配料、混练、成型、烘干后,在埋炭(煤焦炭)气氛中分别于800、1 000、1 300和1 400℃保温3 h煅烧,然后对烧后试样进行三点弯曲试验,并测定烧后试样的平均孔径,分析烧后试样的显微结构。结果表明:铝粉、硅粉的加入比例显著影响A l2O3-ZrO2-C材料的力学性能:经800和1 000℃煅烧后,试样的抗折强度、弹性模量和韧性均随铝粉加入量的增加而增大,而经1 300和1 400℃煅烧后,试样的抗折强度、弹性模量和韧性均随铝粉加入量的增加而减小;试样的平均孔径呈现出与力学性能相反的变化规律。上述这些变化规律是铝液的促烧结作用与高温下生成SiC、A lN晶须的强韧化作用和填隙作用以及生成A lN过多导致的结构疏松作用共同作用的结果。     

Effect of SiO2, Fe2O3, and TiO2 on stabilization of cubic ZrO2 in the presence of Al2O3

Several compositions are investigated in order to determine the essence of the phase transformations occurring at temperatures up to 1600°C in the ZrO₂ — Ln₂O₃ (Ln is Nd, Y, Yb) — Al₂O₃ — SiO₂ (Fe₂O₃, TiO₂) systems. The efficiency of using Y₂O₃ and Yb₂O₃ to stabilize cubic ZrO₂ in the presence of a mixture of Al₂O₃ and SiO₂ (Fe₂O₃, TiO₂) is shown. Data show the possibility of fabricating high-quality zirconium-corundum articles with any proportion of Al₂O₃ and ZrO₂.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 6, pp. 17 – 20, June 1996.     

Fe^3＋,Al^3＋,Mg^2＋对石膏结晶习性影响的研究

本文在ＭＳＭＰＲ结晶器中研究了无Ｆ存在下，Ｆｅ＾３＋、Ａｌ＾３＋、Ｍｇ＾２＋三咱离子共存时对石膏结晶习性的影响，结果发现，无论硫酸根过量２．４％还是过量４．８％，Ｆｅ＾３＋、Ａｌ＾３＋、Ｍｇ＾２＋共存得到的石膏晶体几乎都是针状晶体；当硫酸另两种相应的离子浓度保持一定水平时，增大Ｆｅ＾３＋含量，石膏晶体变长；增长Ｍｇ＾２＋含量，石膏晶体变小；增长Ａｌ＾３＋含量，石膏晶体长大，Ｆ与Ａｌ＾３＋同时存在     

Intermediate hydrocarbon species for the CO2-CH4 reaction on supported Ni catalysts

By using pulse surface reaction rate analysis (PSRA), the detailed structure of the intermediate hydrocarbon species was revealed by measuring the dynamic behavior of both CO and H₂ produced from the CO₂-CH₄ reaction on supported Ni catalysts. It was found that the number of hydrogen atoms involved in the intermediate was different from one catalyst support to another: 2.7 for MgO, 2.5 for ZnO, 2.4 for Al₂O₃,1.9 for TiO₂, and 1.0 for SiO₂.     

水泥生料硅铁铝钙的快速分析方法

1 前言 水泥生料中SiO2、Fe2O3、Al2O3、CaO的测定,是对水泥生料进行率值控制的重要依据,它对确保水泥产品质量,意义十分重大。众所周知,在生产控制分析中,要求整个分析快速准确,方可达到及时调整配方、提高产品质量的目的。目前,水泥生料的分析主要有仪器分析法和传统的化学分析法两种。大     

CH4/CD4 isotope effect on the reaction of adsorbed hydrocarbon species in CO2-reforming over Ni/Al2O3 catalyst

By replacing CH₄ with CD₄, the isotope effect on the reaction of adsorbed hydrocarbon species with CO₂ over Ni/Al₂O₃ catalyst was studied using pulse surface reaction rate analysis (PSRA). The first-order rate constant for this step was 1.45 times larger for CH₄ than for CD₄. The observed isotope effect suggests that the reaction of adsorbed hydrocarbon species with CO₂ (or adsorbed oxygen) is rate-controlling for the reforming of CH₄.     

Investigation of CH4 Reforming with CO2 on Meso-Porous Al2O3-Supported Ni Catalyst

Meso-porous Al₂O₃-supported Ni catalysts exhibited the highest activity, stability and excellent coke-resistance ability for CH₄ reforming with CO₂ among several oxide-supported Ni catalysts (meso-porous Al₂O₃ (Yas1-2, Yas3-8), -Al₂O₃, -Al₂O₃, SiO₂, MgO, La₂O₃, CeO₂ and ZrO₂). The properties of deposited carbons depended on the properties of the supports, and on the meso-porous Al₂O₃-supported Ni catalyst, only the intermediate carbon of the reforming reaction formed. XRD and H₂-TPR analysis found that mainly spinel NiAl₂O₄ formed in meso-porous Al₂O₃ and -Al₂O₃-supported catalysts, while only NiO was detected in -Al₂O₃, SiO₂, CeO₂, La₂O₃ and ZrO₂ supports. The strong interaction between Ni and meso-porous Al₂O₃ improved the dispersion of Ni, retarded its sintering and improved the activated adsorption of CO₂. The coking reaction via CH₄ temperature-programed decomposition indicated that meso-porous Al₂O₃-supported Ni catalysts were less active for carbon formation by CH₄ decomposition than Ni/-Al₂O₃ and Ni/-Al₂O₃.     

Effects of promoters on catalytic activity and carbon deposition of Ni/γ‐Al2O3 catalysts in CO2 reforming of CH4

Catalytic reforming of methane with carbon dioxide was studied in a fixed‐bed reactor using unpromoted and promoted Ni/γ‐Al₂O₃ catalysts. The effects of promoters, such as alkali metal oxide (Na₂O), alkaline‐earth metal oxides (MgO, CaO) and rare‐earth metal oxides (La₂O₃, CeO₂), on the catalytic activity and stability in terms of coking resistance and coke reactivity were systematically examined. CaO‐, La₂O₃‐ and CeO₂‐promoted Ni/γ‐Al₂O₃ catalysts exhibited higher stability whereas MgO‐ and Na₂O‐promoted catalysts demonstrated lower activity and significant deactivation. Metal‐oxide promoters (Na₂O, MgO, La₂O₃, and CeO₂) suppressed the carbon deposition, primarily due to the enhanced basicities of the supports and highly reactive carbon species formed during the reaction. In contrast, CaO increased the carbon deposition; however, it promoted the carbon reactivity. © 2000 Society of Chemical Industry