掺杂立方氮化硼对金刚石聚晶致密化和显微结构的影响

 以小于0.5 μm的金刚石和氮化硼（以下简称cBN）微粉为原料,在6.0 GPa和1 450～1 480 ℃保温30 min的工艺条件下,成功地烧结出晶粒尺寸小于1 μm、以WC/Co硬质合金为衬底的金刚石聚晶。研究了cBN掺杂对金刚石基质密实化和显微结构的影响。研究表明,cBN可以有效地抑制金刚石异常长大。细晶而且致密的金刚石聚晶有优异的力学性能。     

Accurate prediction method for the microstructure of amorphous alloys without non-metallic elements

A new structural parameter of amorphous alloys called atomic bond proportion was proposed, and a topological algorithm for the structural parameter was proven feasible in the previous work. In the present study, a correction factor, λ, is introduced to optimize the algorithm and dramatically improve the calculation accuracy of the atomic bond proportion. The correction factor represents the ability of heterogeneous atoms to combine with one another to form the metallic bonds and it is associated with the uniformity of the master alloy, mixing enthalpy, cooling rate during preparation, and annealing time. The correction factor provides a novel pathway for researching the structures of the amorphous alloys.     

Zr-Cu Amorphous Films Prepared by Magnetron Co-sputtering Deposition of Pure Zr and Cu

ZrxCu100-x amorphous films are prepared on Si （111） substrates by magnetron co-sputtering of pure Zr and Cu. It is found that the glass forming ability （GFA） of the films increases with x when x is in the range from 35 to 65 and with the best glass forming ability at x = 65. It is therefore different from the bulk counterparts, for which only x = 35 and 50 were reported to have high glass forming ability during casting. The structure of the films is sensitive to the substrate temperature and the sputtering argon pressure.     

具有强酸位的六方和立方介孔硅铝分子筛合成及催化活性比较

六方 MCM- 41和立方 MCM- 48介孔分子筛是长程有序的介孔材料 ,由于其孔壁是无定形结构 ,具有较弱的酸性 ,限制了其应用范围 .若能提高它们的酸强度则可提高其在石油炼制和精细化工中的应用价值 .现已采用多种改进方法来提高其酸强度 [1～ 6 ] ,但所合成的介孔材料均为六方结构 ,而具有立方结构的材料未见文献报道 .本文采用两步晶化合成法 ,用低浓度的表面活性剂合成出具有强酸位的立方介孔分子筛 ( MB48) ,还通过调节溶液的酸碱性合成出六方介孔分子筛 ( MB41 ) ,对样品的结构、酸性和催化性能进行了表征和比较 .1　实验部分1 .1　 β…     

纳米级MCM-49分子筛催化苯与1-十二烯烷基化反应的性能

 在低碱度下合成了纳米级MCM-49分子筛,采用XRD,TEM,NH3-TPD,吸附吡啶的红外光谱和异丙苯裂解等技术对分子筛进行了表征. 催化剂评价结果表明,纳米级MCM-49分子筛在30~160 ℃下对苯与1-十二烯的烷基化反应具有良好的催化性能,烯烃的转化率高于99.6%,直链烷基苯的选择性大于97%,2-和3-位直链烷基苯的选择性大于67.5%. 常规的微米级MCM-49分子筛在低温下的催化活性低于纳米级MCM-49分子筛. ZSM-5,M型分子筛和MCM-41分子筛催化烷基化反应的活性较低,Y型分子筛虽具有较高的催化活性,但生成2-和3-位直链烷基苯的选择性明显低于MCM-49. MCM-49的骨架结构与MCM-22相似,晶体外表面上含有大量的12元环孔穴,该结构有利于烷基化反应的进行.