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Effect of Filler Composition on the Brazing of Alumina to Copper Using Ultrasonic Wave

Khalid M.HAFEZ , Masaaki NAKA

材料科学技术(英文)

An ultrasonic wave was applied during brazing of alumina to Cu. First alumina was metallized by applying ultrasonic wave in braze bath. Then the metallized alumina was brazed with Cu using the same filler alloy. The filler used were Zn-Al alloys and Zn-Sn Alloys. The weight percent of Al in filler was ranging between 0, 5%, 10%, respectively. The weight percent of tin in filler was ranging between 0, 30%, 60% and 91%, respectively. The joining mechanism was investigated by measuring the joining strength, hardness and analyzing the microstructure at interface of the joint. The shear strength and microstructure of the joint strongly depend on the filler composition. The effect of ultrasound was derived primarily from acoustic cavitations, impact and friction of the filler against alumina ceramic. This improved the wetting between alumina and the filler, and reflected to improve the joint strength. Another ultrasonic advantage as to reduce of the joining temperature, that reduced the thermal stress in the braze joint.

关键词: Alumina , null , null , null , null , null

Fabrication of Ni-alumina Composite Membrane via Powder and Bulk Impregnation Method for Hydrogen Separation

Supawan Vichaphund Duangduen Atong

材料科学技术(英文)

This work reports two preparation methods of Ni-Al2O3 composite to be used as a hydrogen separation membrane. The first method was powder impregnation while the second method was soaking-drying-firing or bulk impregnation. In the first method, the 10 wt pct Nickel (II) nitrate hexahydrate solution was mixed with Al2O3 powder. The mixed powders were dried at 100°C and uniaxially pressed into a disk shape at 7 MPa. The densification of composite membranes was accomplished by pressureless sintered at 900-1300°C. For the second preparation method, the Al2O3 disk support was prepared firstly by uniaxially pressing Al2O3 powder at 7 MPa and then sintered at 1000-1200°C for 2 h. After that, the Al2O3 support was soaked into 10 wt pct Ni solution, dried at 100°C and calcined at 900°C for 2 h. The soaking-drying-firing sequence was repeated ten times to finally obtain the Ni-Al2O3 membranes. After preparation process, the membranes fabricated from these two methods were reduced at 910°C for 2 h in hydrogen atmosphere. The effect of the preparation method on properties of membranes in terms of density, porosity, phase and microstructure are discussed.

关键词: Composite membrane , hydrogen separation , Nickel , Alumina

Cu-ZnO-Al2O3复合催化剂上甘油选择氢解合成丙二醇

王帅 , 刘海超

催化学报 doi:10.1016/S1872-2067(14)60094-2

分别采用均匀共沉淀法、沉积-沉淀法和传统的共沉淀法制备了3种具有相似组成的Cu-ZnO-Al2O3催化剂(CZA-HP, CAZ-DP和CZA-CP);同时还采用均匀共沉淀法制备了Cu-ZnO催化剂(CZ-HP)以用于比较. X射线衍射表征结果表明,以上方法制备的Cu-Zn-Al碱式碳酸盐前体中Cu2+, Zn2+和Al3+的混合均匀程度的顺序为CZA-DP90%). Cu-ZnO-Al2O3催化剂表面单位Cu原子的本征活性顺序为CZA-DP < CZA-CP < CZ-HP < CZA-HP,与它们的氧化还原能力相一致.此外, Al2O3的添加还显著地抑制了Cu粒子在反应过程中的聚集,提高了催化剂的稳定性.经6次循环使用后, CZ-HP中Cu粒子的粒径从13.2增至45.2 nm,活性相应下降了45%;而CZA-HP中Cu粒子的粒径从8.3增至19.0 nm,活性仅下降了10%.

关键词: 甘油 , 选择性氢解 , 丙二醇 , , 氧化锌 , 氧化铝 , 碱式碳酸盐前体 , 构效关系 , 催化剂稳定性

机械化学法制备的Al/Ce复合氧化物负载NiMo催化剂的加氢脱硫活性

Květa Jirátová , Alla Spojakina , Luděk Kalu?a , Radostina Palcheva , Jana Balabánová , Georgi Tyuliev

催化学报 doi:10.1016/S1872-2067(15)61016-6

将Al和/或Ce的硝酸盐与NH4HCO3球磨混合,采用机械化学法制备了Al2O3-CeO2载体(其中Ce含量为1–10 wt%),再以杂多钼酸盐(NH4)4NiMo6O24为活性金属Ni和Mo的前驱体,通过浸渍法制备NiMo6/Al2O3-CeO2催化剂,并将其用于1-苯并噻吩(BT)的加氢脱硫(HDS)反应中.运用化学分析、X射线衍射、N2吸附-脱附法、H2程序升温还原、NH3程序升温脱附和X射线光电子能谱对催化剂的物化性质进行了表征.结果表明,催化剂的酸性随着载体中Ce含量的增加而下降. Ce修饰的Al2O3载体表面的NiS/MoS原子比下降了2倍. NiMo6/Al2O3催化剂表现出最高的HDS活性(以单位重量催化剂计),其酸性和表面MoOxSy物种的浓度(Mo5+浓度)也最高;当催化剂中Ce含量逐渐增加到10 wt%以上时,其活性逐渐将为0.与浸渍法制得的参比催化剂相比,前驱体和催化剂组成相同的情况下,采用机械化学法制得的所有催化剂活性明显提高.

关键词: , , 氧化铝 , 氧化铈 , Anderson型杂多钼酸盐 , 1-苯并噻吩 , 加氢脱硫 , 机械化学法

Microstructure of Co-Ni-Al2O3 Composite Coatings by Electroforming

Gang WU , Ning LI , Derui ZHOU , Kurachi Mitsuo

材料科学技术(英文)

The metal matrix composite coatings of Co-Ni- Al2O3 were studied by electrolytic codeposition of Co-Ni alloys and Al2O3 on a Cu substrate from a sulfamate electrolyte containing Al2O3 particles. It was illustrated from the examined results of SEM, AFM and XRD that surface morphology and microstructure of Co-Ni- Al2O3 coatings appear to be mainly influenced by variations in Co content. The high Co content coatings with hcp lattice structure have a more uniform and fine structure than that of low Co content coatings with fcc lattice structure. The codeposition of Al2O3 particles in Co-Ni alloys can not change the phase structure of solid solution, only affects the growth and orientation of crystal planes and mostly increase the d value of lattice.

关键词: Electroforming , null , null , null

Characterization and Photoluminescence Properties of AluminaNanowires Elaborated by Arc-Plasma

C.Arnoult , X.Devaux , H.Rinnert , M.Vergnat

材料科学技术(英文)

Ultrafine powders containing alumina nanowires are synthesized by DC arc plasma from pure aluminium metal. Nanowires grow only when reactive gases are composed of nitrogen and less than ten percent of oxygen. Nanowires have the diameters ranging from 20 to 80 nm and lengths ranging from hundreds nanometers to tens of micrometers. A first assumption of the mechanism process is proposed, in which nanowires grow starting directly from the aluminium. Photoluminescence measurements show that the powders have three emission peaks around 435, 530 and 750 nm resulting from different kinds of defects such as oxygen vacancies, aluminium interstitial ions and surface defects.

关键词: Nanowires , null , null , null

氧化铝载体对Pt-Sn/Al2O3催化剂上苯胺和苯甲醇一步合成N-苯基苄胺催化反应性能的影响

殷梦瑶 , 何松波 , 余正坤 , 吴凯凯 , 王连弟 , 孙承林

催化学报 doi:10.1016/S1872-2067(12)60608-1

以基于借氢策略的苯甲醇和苯胺一步合成N-苯基苄胺为模型反应,研究了三种不同表面结构的氧化铝对其负载的Pt-Sn催化剂上N-烷基化合成仲胺反应性能的影响.采用N2吸附-脱附法、压汞法、X射线衍射、透射电镜、扫描电镜、CO脉冲吸附、H2-程序升温还原及NH3-程序升温脱附等技术对载体和Pt-Sn/Al2O3催化剂进行了表征.结果表明,与Al2O3相互作用较弱且高度分散的Pt颗粒具有很高的催化活性,Al2O3载体较大的孔体积和大孔分布的孔结构有助于反应物扩散和吸附到催化剂表面并提高反应活性.同时也有利于反应产物从催化剂表面离开,从而提高催化剂的稳定性.然而Al2O3较强的酸性及酸性分布降低了产物仲胺的选择性和催化剂稳定性.

关键词: 氧化铝 , 铂-锡 , 苯胺 , 苯甲醇 , N-烷基化 , 借氢策略

钒氧化物催化CO2氧化异丁烷脱氢的研究

袁瑞雪 , 李杨 , 闫浩兵 , 王欢 , 宋健 , 张中申 , 樊卫斌 , 陈建刚 , 刘忠文 , 刘昭铁 , 郝郑平

催化学报 doi:10.1016/S1872-2067(14)60180-7

采用溶胶-凝胶法制备了一系列钒氧化物催化剂,并用于CO2氧化异丁烷脱氢反应.采用X射线衍射、低温N2吸附-脱附、O2程序升温氧化、程序升温表面反应和原位傅里叶变换红外光谱等方法研究了催化剂的性质.反应结果表明,尽管所有钒氧化物催化剂的丁烯选择性都大于85%,但随着催化剂组成和制备方法的改变,催化活性和稳定性差异显著.其中,12 wt% V2O5/Ce0.6Zr0.4O2(7 wt%)-Al2O3的催化活性最高,而6 wt% V2O5-Ce0.6Zr0.4O2(7 wt%)-Al2O3的稳定性最佳.关联分析催化反应结果与催化剂表征表明,钒氧化物的催化活性取决于VOx物种的结晶度和分散度,而催化剂表面所积重质焦炭的特性是决定催化剂稳定性的关键.非稳态反应和原位光谱结果确认, CO2氧化异丁烷脱氢遵循Mars-van Krevelen氧化还原机理.

关键词: 异丁烷 , 氧化脱氢反应 , 二氧化碳 , 五氧化二钒 , 三氧化二铝

银/氧化铝催化乙醇选择性还原氮氧化物过程中典型中间体的吸附态研究

邓华 , 余运波 , 贺泓

催化学报 doi:10.1016/S1872-2067(15)60873-7

机动车污染物排放是我国大气复合污染形成的重要原因之一.尽管柴油车在我国机动车保有量中所占比例不到20%,但其排放的颗粒污染物(PM)和氮氧化物(NOx)分担率均超过60%.因此,控制柴油车尾气排放成为我国亟待解决的大气污染问题.目前,氨选择性催化还原NOx技术(NH3-SCR)已规模化应用于柴油车污染排放控制,出于安全性考虑,以尿素水溶液作为氨的来源.但NH3-SCR技术应用于柴油车尾气净化存在如下缺点:需要布建庞大的尿素添加基础设施、后处理系统复杂等.与此相反,以车载燃油为还原剂来源的HC-SCR技术可有效规避上述难题,展现了较好的应用前景.但是,直接以柴油为还原剂时, HC-SCR对NOx净化的效率还难以满足日益严格的排放法规的要求,因此需要深入研究HC选择性还原NOx的微观机制与构效关系,并以此为指导,发展以车载燃料为还原剂来源的高效净化NOx的新原理和新方法.已有的研究表明,银/氧化铝(Ag/Al2O3)具有优异的催化乙醇选择性还原NOx的能力,是最有希望应用于柴油车尾气NOx净化的催化剂-还原剂组合体系.鉴于此,本论文以Ag/Al2O3催化剂上乙醇-SCR反应为研究对象,以密度泛函理论计算方法(DFT)搭建了Ag/Al2O3催化剂的理论模型,考察了反应物乙醇(CH3CH2OH)、关键中间体(烯醇式物种CH2=CHO?和?NCO)在Ag/Al2O3催化剂上的吸附特征,采用电子态密度分析(DOS)研究了以上物种被活化的电子机制,以期甄别Ag/Al2O3催化乙醇选择性还原NOx的活性位结构,为高性能的HC-SCR催化剂设计提供指导.
  依据化学态的不同, Ag/Al2O3催化剂上活性组分银可分为:高度分散的离子态(Ag+、在催化剂表面以Ag?O形式存在)、部分氧化团簇(Agnδ+)和金属颗粒银(Agn0),其中氧化态的银是催化乙醇选择性还原NOx的活性组分. Al2O3载体的主要暴露晶面为(110)和(100),在上述晶面上Al的配位状态存在明显差异,显著影响了银物种的锚定与分散,形成了具有不同键合特征的Ag?O?Al结构.基于对Al2O3暴露晶面上Al配位状态的分析,搭建了6种Ag?O?Al结构模型.结合Al MAS NMR对Ag/Al2O3实际催化剂的表征结果和理论模型吸附能的分析,获得了最为可能的两种Ag?O?Al结构: Ag?O?Altetra(AlO4)和Ag?O?Alocta(AlO6);前者为AgO与Al2O3(110)面Altrip位键合形成的特征结构(Al最终为四配位),后者系AgO锚定于Al2O3(100)面Alpenta位的能量最优结构(Al最终为六配位).
  在Ag?O?Altetra上, Altetra位具有较强的酸性, Ag、Al原子轨道的杂化融合有利于电子转移;以上特性促进CH3CH2OH、CH2=CHO?、?NCO的吸附活化.在HC-SCR反应中,关键中间体?NCO通过与NOx直接反应可形成最终产物N2和CO2.可见,?NCO中N=C键的拉伸活化、断裂对上述反应的发生至关重要.由电子态密度分析可知, N=Cσ键能向Ag?O?Altetra中Altetra位转移电子,而Ag与Al的轨道融合能反馈电子到N=C π键;在这两种电子转移机制作用下,?NCO中的N=C键被最大程度弱化,有利其断裂,转化为最终产物N2和CO2.而Ag?O?Alocta上,并没有N=C键的活化拉伸,反而呈现出N=C键收缩趋势,不利于N=C键的断裂与最终产物的形成.由此推定, Ag?O?Altetra是Ag/Al2O3催化剂上HC-SCR反应的活性中心.

关键词: , 氧化铝 , 氮氧化物 , 选择性催化还原 , 密度泛函理论

Ni基催化剂催化燃油重整耦合选择性催化还原NOx反应

赵娇娇 , 余运波 , 韩雪 , 贺泓

催化学报 doi:10.1016/S1872-2067(12)60598-1

分别以La2O2CO3,CeO2,ZrO2和Al2O3为载体,采用浸渍法制备了Ni基重整催化剂,并以正十二烷模拟车载燃油进行催化重整反应以同时制备小分子碳氢化合物(HCs)和H2,考察了其在4wt% Ag/Al2O3上选择性催化还原(HC-SCR)氮氧化物(NOx)的性能采用N2吸附-脱附、X射线粉末衍射、H2程序升温还原和热重等手段对Ni基催化剂进行了表征.结果表明,随着重整催化剂氧化还原性能增强,产物中H2浓度增加,可参与SCR反应的HCs含量减少,从而导致重整-SCR耦合体系上NOx净化活性温度窗口向低温移动,NOx最高转化率降低.Ni/ZrO2+Ag/Al2O3耦合体系中H2/HCs符合SCR反应所需的最优比例,在柴油车典型排气温度范围内表现出良好的NOx净化能力.同时,在Ni/ZrO2+Ag/Al2O3耦合体系上考察了其燃油重整-SCR的活性稳定性.结果显示,重整催化剂的耐久性有待进一步提高.

关键词: 燃油重整 , 镍基催化剂 , 氮氧化物 , 选择性催化还原 , , 氧化铝

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