材料期刊网

Preparation of a SiC/Cristobalite-AlPO4 Multi-layer Protective Coating on Carbon/Carbon Composites and Resultant Oxidation Kinetics and Mechanism

Jianfeng Huang Wendong Yang Liyun Cao

材料科学技术（英文）

In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a SiC/C-AlPO₄ multi-layer coating was fabricated on the C/C composites by a simple and low-cost method. The internal SiC bonding layer was prepared by a two-step pack cementation process and the external C-AlPO₄ coating was deposited by hydrothermal electrophoretic deposition process. Phase compositions and microstructures of the as-prepared multi-layer coating were characterized by X-ray diffraction (XRD), scaning electron microspocy (SEM) and energy dispersive spectrometer (EDS). Anti-oxidation properties, oxidation behavior and the failure behavior of the coated composites were investigated. The results indicate that the multi-layer coating exhibits obviously two-layer structure. The inner layer is composed of β-SiC, α-SiC phase with a scale of silicon phase. The outer layer is composed of cristobalite aluminum phosphate (C-AlPO₄) crystallites. The SEM observation shows the good bonding between the inner and outer layers. The multi-layer coating displays an excellent oxidation resistance in air in the temperature range from 1573 to 1773 K, and the corresponding oxidation activation energy of the coated C/C composites is calculated to be 117.2 kJ/mol. The oxidation process is predominantly controlled by the diffusion of O₂ through the C-AlPO4 coating. The failure of the multi-layer coating results from the generation of the microholes that may be left by the escape of the oxidation gases.

关键词: Carbon/carbon composites , 磷酸铝 , 水热电泳沉积 , 涂层 , 氧化

液态CaO-SiO_2和CaO-Al_2O_3-SiO_2渣中CaO的活度

邹元爔 , 赵彭年 , 曹兆民

金属学报

利用石灰的加碳还原反应,设计了一个新的研究方法,以直接测定液态高炉型渣中CaO的活度.这一方法的成功,依靠溶剂金属的正确选择以降低熔液中钙的化学位,而使金属钙量提高到可以用化学分析测定的水平.我们估计钙在锡稀溶液中的活度系数很小,可能符合于我们的要求,因此研究了下列反应:CaO+C(石墨)=Ca(锡)+CO(气).以测定液态CaO-SiO_2和CaO-Al_2O_3-SiO_2渣中CaO的活度,在上式中符号下波纹线表示溶于渣中的组分,直线表示溶子金属中的组分,下同.对于CaO-Si0_2系,应用Gibbs-Duhem关系从CaO活度值算出了SiO_2的活度值,并根据一个统计力学模型讨论了活度曲线的形状.从CaO-Al_2O_3-SiO_2系的研究结果,可知在所研究的整个碱度范围內,渣中存在10%Al_2O_3都使CaO的活度增加;当Al_2O_3为20%时,则对CaO活度的影响视碱度不同而异.对Al_2O_3的这种行为,根据炉渣的离子结构理论提出了解释.

关键词:

MgO-CaO耐火材料性能研究进展

王宏联 , 崔庆阳 , 薛群虎 , 闫振华 , 宋鹏涛 , 田晓丽

耐火材料 doi:10.3969/j.issn.1001-1935.2010.01.018

介绍了MgO-CaO耐火材料的特性,总结了提高MgO-CaO耐火材料的抗水化性、烧结性、抗渣性、抗剥落性等的技术措施.提出了MgO-CaO耐火材料的发展方向,即:开发高CaO含量的MgO-CaO耐火材料;进一步开发不烧MgO-CaO耐火材料;开发水泥回转窑用MgO-CaO耐火材料.

关键词: MgO-CaO耐火材料 , 抗水化 , 应对措施

Investigations of the g factors of Fe+ in MgO and CaO

Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences

The g factors of Fe+ in MgO and CaO are theoretically investigated by the perturbation formula of the g factor of a V ion in cubic octahedral symmetry based on the cluster approach. By considering the partial quenching of the spin-orbit coupling interaction and the effective Lande factor due to the dynamic Jahn-Teller effect (DJTE), the experimental g factors of the studied systems are reasonably interpreted. It can be suggested that the small g factors of the Fe+ centers in MgO and CaO can be likely attributed to the DJTE, rather than the covalency effect within the scheme of the static crystal-field model.

关键词: electron paramagnetic resonance;crystal- and ligand-field theory;Fe+;MgO;CaO;atomic screening constants;electron spin resonance;paramagnetic-resonance;orbit interaction;scf functions;crystals;spectra;oxide;co2+

CaO-SiO_2-Al_2O_3熔渣中CaO的活度

张子青 , 周继程 , 邹元燨 , 田彦文

金属学报

本文以Sn为溶剂金属,直接用“渣-金属”化学平衡法,在较大组成范围内测定了CaO-Si0_2-Al_2O_3三元熔渣中CaO的活度。成功地用图示推测法推测了较难直接获得实验结果的低CaO浓度范围内CaO的活度。应用本文实验结果和数据分析得到了该渣系中较全面的等CaO活度曲线图,并对Al_2O_3在该渣系中的酸碱性行为进行了探讨。

关键词:

真空冶炼用MgO-CaO坩埚的研制

刘彦海 , 段百泉 , 胡希东

耐火材料 doi:10.3969/j.issn.1001-1935.2007.04.012

为了降低真空冶炼用MgO坩埚因MgO的高温不稳定性对冶炼合金造成的影响,同时发挥CaO的脱硫作用,以w(MgO+CaO)>97%的MgO-CaO熟料为原料,在对MgO-CaO熟料进行水化试验和烧结试验研究的基础上,研制了MgO-CaO坩埚,并且与CaO坩埚一起对一种纯金属和同材质的高温合金进行了对比冶炼试验.结果表明:MgO-CaO熟料的抗水化性远高于石灰熟料的;在添加适当种类和数量的烧结助剂后,MgO-CaO熟料的可烧结性明显改善;MgO-CaO坩埚的冶炼效果达到甚至超过了CaO坩埚.

关键词: 真空冶炼 , 坩埚 , CaO , MgO-CaO

ZrO2(CaO)纳米粉体的性能与CaO含量的关系

梁丽萍 , 党淑娥 , 高荫本

硅酸盐通报 doi:10.3969/j.issn.1001-1625.2002.06.018

采用凝胶-超临界流体干燥技术合成不同CaO含量的稳定化ZrO2超微粉体,对粉体的织构性能和烧结性能进行研究.实验表明:粉体中CaO的浓度会显著影响其粒度、相组成及烧结性能,而且这种影响作用与传统粉体的不同.

关键词: CaO稳定化ZrO2 , 粒度 , 相组成 , 烧结

PE/CaO复合材料的流变行为

游瑞云 , 肖荔人 , 刘欣萍 , 林葱里 , 黄宝铨 , 许兢 , 陈宇 , 陈庆华

材料工程 doi:10.3969/j.issn.1001-4381.2010.06.002

通过熔融共混法制备CaO含量不同的PE/CaO复合材料,借助熔体流动速率仪和AR2000旋转流变仪,对PE/CaO复合材料熔体的流变行为进行研究.结果表明:PE/CaO复合材料的黏流活化能随CaO含量的增加先上升后逐渐下降;当CaO含量(质量分数,下同)≤20%时,复合材料的线性黏弹性与纯PE相近,零剪切黏度变大的幅度较小;当CaO含量≥25%时,复合材料的时间稳定性下降,零剪切黏度明显增大.

关键词: 聚乙烯 , 氧化钙 , 复合材料 , 流变行为

CaO-NaCl焙烧分解独居石的研究

吴文远 , 陈旭东 , 陈杰 , 孙树臣 , 涂赣峰

稀土 doi:10.3969/j.issn.1004-0277.2004.02.006

研究了630℃～870℃焙烧温度范围内,CaO、NaCl对独居石分解率影响的变化规律,得出了相应的回归方程,并且用该方程讨论了CaO、NaCl、焙烧温度对独居石分解率的影响.研究结果表明:独居石分解率随CaO、NaCl增加、焙烧温度的升高而增加.当CaO和NaCl加入量分别都为45%,焙烧温度为870℃时,独居石的分解率达到78.39%.

关键词: CaO-NaCl , 独居石 , 分解率

CaO高温分离CO2过程的数值模拟

王保文 , 郑瑛 , 贺铸 , 宋侃 , 郑楚光

工程热物理学报

钙基吸收剂煅烧-碳酸化循环法(CCRs)是一种新兴的分离燃煤锅炉尾部烟气中CO2的方法.CaO与CO2碳酸化反应对于CCRs法的应用起着非常重要的作用.本文采用随机孔隙模型(RPM)对CaO与CO2碳酸化反应过程进行了研究,结果表明,适当提高CaO与CO2碳酸化反应的温度和系统压力,增加CaO吸收剂的初始孔隙率、优化CaO的初始比表面积等措施能够有效提高CaO碳酸化转化率和对CO2的吸收容量.

关键词: 煤燃烧 , CO2分离 , CaO碳酸化反应 , 数值模拟 , 随机孔隙模型(RPM)