钒系、钛系Ziegler—Natta催化体系电子作用过程描述

对Ziegler-Natta催化剂的形成和发展进行了介绍,并对其催化体系电子作用过程进行了描述。重点阐述了烷基铝化合物中铝原子与烷基的电子层分布情况、过渡金属元素的电子结构特点,描述以烷基铝和过渡金属卤化物为代表的类阴离子型催化剂和路易斯酸等阳离子型催化剂反应的具体过程以及钒催化剂的催化机理等。     

助剂对Ni/AC催化剂甲醇羰化的影响

分别以Ni(NO3)2.6H2O、ZnAc2.6H2O、Cu(NO3)2.6H2O、(NH4)6Mo7O24及La(NO3)3.4H2O为前体,采用同时浸渍法制备了主活性组分为镍的双金属活性炭负载型催化剂,考察了Zn、Cu、Mo及La等第二金属元素对甲醇羰化合成醋酸Ni/AC催化剂的助催化作用。活性评价表明:以Mo和La为助剂时,可有效地提高甲醇转化率和羰化产物收率,Mo的添加有利于醋酸甲酯的生成,La则使醋酸的选择性提高;Zn、Cu的加入反而使甲醇转化率及羰化产物收率下降。催化剂的羰基化活性顺序为:Ni-Mo/AC>Ni-La/AC>Ni/AC>Ni-Zn/AC>Ni-Cu/AC。关于稀土元素的影响,结果是La优于Ce。     

Effect of processing parameters on the elastic deflection of P/M Ni-Fe36Ni bimetal strips during heating

Electrolytic nickel powder and water-atomized Fe36Ni alloy powder were consolidated into combined compacts with the “two-layer pressing” technique. The compacts, 1.6 mm thick, were sintered at 1200 and 1300‡C in hydrogen, and then rolled into strips 0.8 mm thick. The rolled and annealed strips were fixed at one end as a cantilever beam,and heated gradually from room temperature to 200‡C, in order to measure the thermal deflection of the free end. The measured displacement was always less than the theoretically calculated value, due to the existence of pores in the sintered products. The effect of the temperature and time of sintering on the thermal deflection of the bimetal strips was investigated. It was found that the proper degree of sintering is essential for the bimetal strip to exhibit the largest displacement upon heating. The microstructure and chemical composition across the nickel layer, the contact interface, and the Fe36Ni layer were examined with a SEM and EPMA.     

Formation mechanism of bimetal composite layer between LCS and HCCI

A low carbon steel (LCS)/high chromium white cast iron (HCCI) bimetal wear plate about 20 mm in thickness was prepared by liquid-liquid bimetal composite casting technology to substitute for the welding wear plate. A clear and distinguishable composite layer between the LCS and the HCCI was detected with SEM, and the composition and phase were analyzed through EDS and XRD. The composite layer was composed of three sublayers from the LCS to the HCCI: pearlite transition layer, composite layer, and HCCI transition layer. The Vickers hardness from the pearlite transition layer to the HCCI transition layer was 360 HV to 855 HV. The austenite grows as dendrites between the composite layer and the HCCI transition layer under constitutional undercooling. A large amount of C and Cr, and a smal amount of Si and Mn dissolve in the matrix. Granular Cr7C3 is uniformly distributed. Due to the solute redistribution at the solid-liquid interface, the primary austenite grows from planar to celular and ifnaly to the distinct dendrite crystals. The dendrite crystals have an obvious growth direction perpendicular to the composite layer.     

Probing palladium-cobalt/NaY catalysts by neopentane conversion

Neopentane conversion in hydrogen was used as a catalytic probe for zeolite encaged PdCo particles. Activity and selectivity strongly depend on the pretreatment conditions. PdCo/NaY catalysts exhibit higher isomerization selectivity than Pd/NaY in conformity with previous results on SiO₂ supported Pd and PdCo. This is remarkable, because reduced Co/SiO₂ displays 100% selectivity for hydrogenolysis. The isomerization selectivity thus appears to be a useful measure for the extent of alloying between Pd and Co.On leave from Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.     

氧化铝负载Co-Mo双金属氧化物的共沉淀制备

采用双溶剂体系(硝酸铝和硝酸钴的乙醇溶液与钼酸铵的碳酸铵水溶液)共沉淀制备了氧化铝负载Co-Mo双金属氧化物。研究了双溶剂体系中乙醇和水的体积比对共沉淀的影响,考察了老化时间对氧化物结构参数的影响,研究了焙烧温度对氧化物还原性能的影响。结果表明:乙醇和水体积比对钼酸根离子的沉淀有重要影响,为了保证钼酸根离子的完全沉淀,乙醇的体积要随着MoO3负载量的增加而提高;随着老化时间的增加,氧化物的比表面积先增加后下降,6 h老化的样品具有最大的比表面积;低温焙烧制得的氧化物较容易还原。     

双金属复合管滚压塑性成形工艺及试验研究

分析了双金属复合管滚压塑性成形的过程,并对滚压塑性成型的双金属复合管进行了实验验证。     

Optimization procedures for GMAW of bimetal pipes

Autogenous gas tungsten arc welding (GTAW) and pulse rapid arc gas metal arc welding (GMAW) of butting bimetal (Bubi) pipelines were studied. GMAW was carried out from the outside of the pipe while GTAW was done from the inside to prevent lack of penetration and to promote a smooth internal weld bead surface. Current, welding speed, electrode diameter, shielding gas and orbital positions were defined as variables. The requirement for the GTA weld was to achieve 2 mm penetration depth without undercutting. The required penetration was difficult to achieve due to the outwards flow pattern in the molten pool driven by the Marangoni effect as a result of low sulphur content. It was shown that, under optimised conditions, it was possible to obtain sound welds with proper geometry and defect free. The conditions needed were a combination of current of 170 A, welding speed of 200 mm/min and an electrode angle of 30°, with shielding gas protection of He-25%Ar for narrow groove welding of a J-beveled pipe.     

M42/45钢双金属复合材料的SPS烧结及其界面研究

利用放电等离子烧结技术（SPS）实现了M42粉末高速钢的制备及与45钢的连接,对其界面的显微组织形貌、元素分布、显微硬度及相界面形成过程进行了测试分析。结果表明,接头过渡层的成分、显微硬度都呈现梯度变化,连接界面没有裂纹及大孔洞出现,界面结合紧密,其过渡层厚度可达10.2μm;界面连接为熔合连接与扩散连接的共同作用,其中烧结初期以熔合连接为主,烧结中后期,扩散连接逐渐成为主导。     

碳载金铂双金属催化剂催化活性研究

采用KBH4做还原剂、PVP做保护剂,化学法一步合成Au-Pt合金纳米粒子,应用UV-Vis、TEM、XRD等手段对其进行了表征.将所合成的合金纳米粒子负载在碳黑上,获得Au-Pt双金属碳载催化剂,应用循环伏安法(CV)检测了催化剂对甲醇的电催化氧化活性.研究表明,Au-Pt/C催化剂的催化活性明显高于Pt/C的,说明...