材料期刊网

Mechanism and Kinetics of Transformation of Alumina Inclusions by Ca Treatment

Z.J. Han

金属学报(英文版)

Calcium treatment is nowadays a well-established method to improve steel castability and final properties e.g. machinability, toughness and surface quality. The effects of calcium are mainly based on its strong ability to form sulphides and oxides. The topic of the present paper concerns the basic mechanism and kinetics of the transformation process of alumina inclusions in steel when calcium introduced into the steel e.g. by wire feeding or powder injection. To clarify the mechanisms model experiments were performed by studying reactions between Al2O3 and CaO in a laboratory furnace as well as by performing Ca treatments in an 8 kg induction furnace for Al deoxidised melt. The phases formed during the reaction between Al2O3 and CaO were examined by SEM-EDS, and the proposed reaction sequence of Al2O3CA6CA2CACAx(liquid) was discussed based on the experimental observations. The kinetics of the reaction of calcium with alumina inclusions were simulated by immersing alumina plates in a Ca treated steel melt in the induction furnace. Results were compared with observations of real inclusion transformation. Based on the results a kinetic model was proposed.

关键词: Alumina inclusions , 夹杂 , 机理 , 钙处理 , 动力学

Removal Mechanism of Aqueous Lead by a Novel Eco-material: Carbonate Hydroxyapatite

Huanyan XU , Lei YANG , Peng WANG

材料科学技术（英文）

Kinetics and mechanisms on the removal of aqueous lead ion by carbonate hydroxyapatite (CHap) are investigated in the present work. Experimental results show that, in the whole pH range, the lead removal percentage increases with decreasing pH values and reaches a maximum at pH=2–3. Under some conditions, the lead residual concentration is below national integrated wastewater discharge standard, even drinking water standard. The removal behavior is a complicated non-homogeneous solid/liquid reaction, which can be described by two stages from kinetic point of view. At the earlier stage, reaction rate is so fast that its kinetic course is intricate, which requires further study. At the latter stage, the rate of reaction becomes slow and the process of reaction accords with one order reaction kinetic equation. Experimental results show that the relationship between reaction rate constant k1 and temperature T accords to Arrhenius Equation, and the activation energy of sorption (Ea) is 11.93 kJ/mol and frequency factor (A) is 2.51 s-1. X-ray diffraction (XRD), scanning electron microscopy with an energy dispersive X-ray fluoresence spectrometer (SEM-EDS) and toxicity characteristic leaching procedure (TCLP) test were conducted in this work. It is indicated that the main mechanism is dissolution-precipitation, accompanying with superficial sorption.

关键词: Carbonate hydroxyapatite , 铅离子 , 动力学 , 机理 , 溶解－沉淀

Fe-C-Mn-Al系TRIP钢两相区奥氏体转变模拟

钱海帆 , 张宇光 , 王炜 , 张建平

钢铁

为了研究Fe-C-Mn-A1系TRIP钢两相区奥氏体化过程中合金元素在奥氏体和铁素体中的分布,利用热膨胀仪、金相显微镜、电子探针等仪器,在对TRIP钢两相区奥氏体化过程进行热力学与动力学分析的基础上,建立了两相区奥氏体化过程的扩散模型,采用显式有限体积法对800℃与840℃的奥氏体化过程进行了数值求解.模拟结果表明:奥氏体转变初期受C元素在奥氏体中的扩散控制达到亚平衡,奥氏体转变速率较快；此时A1元素在奥氏体与铁素体界面处的浓度差较显著,Mn元素在奥氏体与铁素体界面处的浓度差不显著.奥氏体转变后期受Mn元素在铁素体内的扩散控制,转变速率较慢；此时A1元素在铁素体内已大量富集,Mn元素在奥氏体与铁索体界面处有较显著的浓度差.

关键词: 相变诱导塑性 , 两相区退火 , 奥氏体化 , 动力学 , 扩散 , 铝 , 锰 , 有限元法

Effect of Deposition Temperature on Dynamics and Mechanism of Deposition for Si-B-C Ceramic from BCla/SiCH3Cl3/H2 Precursor

材料科学技术（英文）

关键词: 沉积温度 , 化学成分 , 动力学 , 机理 , 陶瓷 , 沉积速率 , 形态学变化 , 微观结构

工业Fe-Mn催化剂上基于详细反应机理的F-T合成动力学模型Ⅱ.不同校正方法的动力学模型分析

滕波涛 , 常杰 , 王刚 , 张成华 , 刘颖 , 郑洪岩 , 杨骏 , 张荣乐 , 白亮 , 相宏伟 , 李永旺

催化学报

通过平衡闪蒸模拟催化剂孔道液体组成、烯烃物理吸附和虚拟烯烃分压等方法,考察了化学反应以外的非本征因素对F-T合成动力学模型的校正.平衡闪蒸模拟催化剂孔道中烯烃组成的校正计算结果表明,在烯烃浓度出现峰值前,溶解度效应对烯烃再吸附及参与二次反应起主导作用,而在烯烃浓度出现峰值后,烯烃的扩散和物理吸附等效应可能起主导作用.分析烯烃添加的反应器模拟结果发现,考虑烯烃物理吸附作用的动力学模型校正方法不能够正确反映烯烃添加实验的定性规律,而虚拟烯烃分压校正方法能够正确反映烃分布规律并可定量预测烯烃添加对产物分布规律的影响,这对需要尾气循环的F-T合成工业操作具有重要意义.

关键词: 费-托合成 , 动力学 , 溶解度 , 物理吸附 , 虚拟烯烃分压 , 铁 , 锰 , 工业催化剂

Coarsening Kinetics of γ＇ Precipitates in Dendritic Regions of a Ni_3 Al Base Alloy

材料科学技术（英文）

关键词: 镍铝基合金 , 粗化行为 , 树突 , 动力学 , 真空电弧重熔 , 扩散控制 , 体积分数 , 溶质元素

化学镀镍反应副产物H2的影响和措施

姬玉林

腐蚀与防护 doi:10.3969/j.issn.1005-748X.2006.04.013

阐述了H2的产生机理,H2的析出、成泡、富集、长大、上浮的动力学原理,分析了H2对施镀过程的不利影响及有利影响,提出促进H2的有利影响和降低其不利影响的措施.

关键词: 机理 , 析出 , 气泡 , 上浮 , 动力学 , 狭缝 , 凹坑 , 针孔

Crystallization Kinetics of Nanophase Glass-Ceramics as Magnetic Disk Substrate

Shengyu JIANG , Jiancheng ZHANG , Feng GU , Yue SHEN , Hua WANG

材料科学技术（英文）

Glass-ceramics containing β-quartz as a main crystal phase based on the system of SiO2-Al2O3-Li2O-K2O-MgO-ZnO were investigated for the application to magnetic storage substrate for higher storage capacity. Parent glasses were prepared, then nucleated and crystallized at certain temperatures for 3~4 h. The crystallization kinetics of glass-ceramics was also studied. The grain size was estimated by Scherrer formula and image treatment of transmission electron microscopy (TEM). The results π showed that the Avrami exponent was determined to be 3.88, the activation energy 189±7 kJ/mol and the grain size 30~60 nm. A detailed microstructure of the glass-ceramics, including grain distribution and the morphology of nano-crystalline was characterized by TEM, X-ray diffraction (XRD), differential scanning calorimeter (DSC), differential thermal analysis (DTA). The relationship between microstructure and mechanical properties was also discussed.

关键词: Glass-ceramics , 动力学 , 磁盘基片

Nd-Al双金属配合物催化双烯聚合反应动力学

董为民 , 杨继华 , 逄束芬 , 黄葆同

催化学报

以Nd-Al双金属配合物为催化剂,考察了丁二烯和异戊二烯聚合反应的动力学,得到稳态聚合速率方程式为Rp=k[M][Nd]n(n=1);丁二烯比异戊二烯有更大的表观增长速率常数k.这些与聚合体系中是否存在过量的烷基铝无关.对多组分稀土催化剂作用下异戊二烯聚合反应动力学方程中出现较高n值的现象进行了初步的探讨.

关键词: 钕配合物 , 铝配合物 , 双金属配合物 , 丁二烯 , 异戊二烯 , 定向聚合 , 动力学

轻烧白云石的动力学及工艺优化

高家诚 , 唐祁峰 , 陈小华

功能材料

对万盛白云石的热分解动力学进行了研究,并对该白云石煅烧工艺进行了正交实验,考虑了烧损温度、时间和粒度对锻白烧损率和水化活性的影响。动力学计算表明白云石的热分解过程中,活化能为148.16kJ/mol。煅烧正交实验表明白云石烧损率的影响因素的顺序为温度、时间、粒度,而水化活性的影响因素的顺序为温度、粒度、时间。优化后的煅烧工艺为温度1050℃,时间1.5h,白云石粒度6～13mm,在此工艺下,万盛白云石的烧损率为46.55%,水化活性为32.07%。

关键词: 白云石 , 热分解 , 动力学 , 煅烧工艺 , 正交实验 , 烧损率 , 活性