J.H.Flores
,
M.E.H.MaiadaCosta
,
M.I.PaisdaSilva
催化学报
doi:10.1016/S1872-2067(15)61032-4
采用三种不同方法制备了Cu-Zn-Al基甲醇催化剂,然后在水相悬浮液中与H型镁碱沸石混合分散,以制得负载型甲醇催化剂.运用X射线衍射、N2吸附-脱附、透射电镜、程序升温还原、NH3程序升温脱附、H2程序升温脱附和X射线光电子能谱对催化剂进行了表征.考察了催化剂催化CO加氢反应生成二甲醚和烃类的性能.该催化剂是在低和高过饱和度条件下采用共沉淀法和均匀沉淀法制得的.制备方法对前驱体的结构特性(如纯度、结晶度和催化剂颗粒粒径分布)有显著影响.低过饱和度的沉淀条件有利于Cu物种的高度分散,增加了催化剂中金属的比表面积,所得催化剂粒径分布均匀.这些效应进而会影响分子筛的性质,导致其微孔孔体积较小,分子筛酸性位被堵塞.通过Cu比表面积和CO转化速率之间的关联可考察甲醇催化剂的性能.
关键词:
甲醇合成催化剂
,
低和高过饱和度下沉淀
,
合成气
,
镁碱沸石
,
烃类
,
二甲醚
陆景彬
,
刘运祚
,
孙亮
,
杨东
,
梁国栋
,
王守宇
,
马英君
,
赵广义
,
李险峰
,
崔兴柱
,
李明非
,
霍俊德
,
曾国模
,
竺礼华
,
吴晓光
原子核物理评论
doi:10.3969/j.issn.1007-4627.2005.02.003
在稀土区奇奇核πh11/2(×)νi13/2转动带中, 系统地观测到随转动频率或角动量增加, B(M1)/B(E2)曲线表现出所谓parabola-like形状, 即在增加到某一转动频率或自旋后, B(M1)/B(E2)比值快速增强. 基于推转模型和粒子转子模型关于奇奇核二准粒子转动带磁偶极约化跃迁几率的描述, 对稀土区双奇核的这一行为进行了讨论. 指出该现象的发生与νi13/2准中子转动顺排特性密切相关. B(M1)/B(E2)比值在接近第二带交叉(即BC准中子对顺排)的较高频率处的增强效果, 可以理解为主要来源于带交叉引起的波函数中混合四准粒子成分的结果. 通过对B(M1)/B(E2)比值的增强效果发生在较低频率处的分析, 对稀土区奇奇核πh11/2(×)νi13/2带角动量耦合图像有了进一步认识.
关键词:
高自旋态
,
奇奇核
,
电磁跃迁特性
,
顺排
Electrochimica Acta
The mechanism of the oxygen reduction reaction (ORR) in a naturally aerated stagnant 0.5 M H(2)SO(4) Was studied using electrochemical methods. The cathodic polarization curve showed three different regions; electrochernical impedance spectroscopy (EIS) measurement was used accordingly. The EIS data were analyzed, and the mechanism for the ORR was proposed consequently. The three regions include a limiting current density region with the main transfer of 4e(-) controlled by diffusion (-0.50V < E < -0.40V), a combined kinetic-diffusion region (-0.40V<E-0.20V) with an additional 2e(-) transfer due to the adsorption of the anions, and a hump phenomenon region (-0.20V<E-0.05V), in which the chemical redox between the anodic intermediate Cu(I)(ads)* and the cathodic intermediate (HO(x))(ads)*, together with the electrochemical reaction, synergistically results in the acceleration of the ORR. Therefore, a coupled electrochemical/chemical process (the EC mechanism) in the hump phenomenon region was proposed, and a good agreement was found between the experimental and fitted results. The EC mechanism was confirmed by the deaerated experiments. (C) 2009 Elsevier Ltd. All rights reserved.
关键词:
Oxygen reduction;Hump phenomenon;Chemical redox;Copper;Electrochemical impedance spectroscopy;sulfuric-acid electrolyte;anodic-dissolution;sulfate-solutions;corrosion;behavior;adsorption;chloride;cu(111);alloy;model
岳华
物理测试
针对生产中出现的Q390E热轧H型钢屈服强度不合格的原因进行了分析.通过工艺对比以及试样检测发现,轧制道次增加以及终轧温度过高会导致钢材晶粒较大,降低了钢材的强度.终冷温度过高导致位错、空位等缺陷在基体中保留较少,不利于组织细化,是导致屈服和抗拉强度强度不合格的主要原因.
关键词:
Q390E
,
H型钢
,
屈服强度
张冬海
,
李自强
,
田亚峻
,
邓平晔
,
陈运法
稀有金属材料与工程
α-磷酸锆与正丁胺(n-butylamine,BA)、四乙烯五胺(4E5A)在去离子水中混合均匀,0～25℃下搅拌6 h,制得具有捕收甲醛功能的层状复合粉体α-ZrP-4E5A.研究了物料用量及反应条件对插层产物收率的影响,并对产物进行了分析、表征,结果表明α-磷酸锆插层产物热稳定性较好,对甲醛的捕收率较高.
关键词:
α-磷酸锆
,
插层
,
甲醛捕收
周姣
,
蒋中刚
,
刘华龙
,
唐道文
,
刘现超
,
燕璞
贵金属
通过热力学计算绘制了298.15 K条件下FeS2-FeAsS-KMnO4-H2O系的E-pH图，找出了较理想的KMnO4氧化FeS2和FeAsS的电位和pH预处理条件。实验表明，经高锰酸钾预处理后，包裹金的黄铁矿和毒砂被打开，这一结果为难浸金矿氧化预处理提供重要的理论参考。
关键词:
有色金属冶金
,
E-pH图
,
难浸金矿
,
高锰酸钾
,
预处理
Xinbin HU
,
Mei ZHANG
,
Xiaochun WU
,
Lin LI
材料科学技术（英文）
Based on the local equilibrium assumption, coarsening behavior of M23C6 carbide at 700℃ in H13 steel was simulated by DICTRA software. The results from the calculations were compared with transmission electron microscopy (TEM) observations. The results show the interfacial energy for M23C6 in H13 steel at 700℃ is thus probably 0.7 J•m-2, which fits the experiments well. The influence of composition and temperature on the coarsening rate was also investigated by simulations. Simulations show a decrease in the coarsening rate when V/Mo ratio is increased, while the coarsening rate increases with increasing temperature.
关键词:
DICTRA Simulation
,
碳化物粗化
,
界面能
,
H13钢
Yong LIU
,
Baiyun HUANG
,
Kechao ZHOU
,
Hongwu OUYANG
,
Yuehui HE
材料科学技术（英文）
In order to overcome the shortcomings of conventional hot pressing, a novel near net-shape technique, called radial hot pressing, for P/M parts with large height-to-diameter (H/D) ratio was introduced. Effects of processing parameters on the microstructures and density of P/M TiAl base alloy valves were studied. Results show that the radial hot pressing is an effective technique for manufacturing valves with a H/D ratio of about 10:1, and the perfect joint interface between the Mo sheet and the parts is helpful for subsequent HIPing.
关键词:
Near net-shape technique
,
null
,
null
