检索结果-南通市图书馆

Purified oxygenand nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation

引用

Journal of Energy Chemistry 2013年第2期22卷 312-320页

作者： Peirong Chen Ly May Chew aleksander kostka Kunpeng Xie Martin Muhler Wei Xia Laboratory of Industrial Chemistry Ruhr-University Bochum Department of Microstructure Physics and Alloy Design Max-Planck-Institute for Iron Research

Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.

关键词： multi-walled carbon nanotubes nitrogen-containing functional groups oxygen-containing functional groups metal-free catalyst selectiveolefin hydrogenation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Laser metal deposition of refractory high-entropy alloys for high-throughput synthesis and structure-property characterization

引用

International Journal of Extreme Manufacturing 2021年第1期3卷 98-120页

作者： Henrik Dobbelstein Easo P George Evgeny L Gurevich aleksander kostka Andreas Ostendorf Guillaume Laplanche Applied Laser Technologies Ruhr-University BochumUniversitätsstr.15044801 BochumGermany Material Science and Technology Division Oak Ridge National LaboratoryOak RidgeTN 37831-6115United States of America Materials Science and Engineering Department University of TennesseeKnoxvilleTN 37996-2100United States of America Center for Interface-Dominated High Performance Materials Ruhr-University BochumUniversitätsstr.15044801 BochumGermany Institute for Materials Ruhr-University BochumUniversitätsstr.15044801 BochumGermany

Progress in materials development is often paced by the time required to produce and evaluate a large number of alloys with different chemical *** applies especially to refractory high-entropy alloys(RHEAs),which are difficult to synthesize and process by conventional *** evaluate a possible way to accelerate the process,high-throughput laser metal deposition was used in this work to prepare a quinary RHEA,TiZrNbHfTa,as well as its quaternary and ternary subsystems by in-situ alloying of elemental *** graded variants of the quinary RHEA were also *** results show that the influence of various parameters such as powder shape and purity,alloy composition,and especially the solidification range,on the processability,microstructure,porosity,and mechanical properties can be investigated *** strength of these alloys was mainly affected by the oxygen and nitrogen contents of the starting powders,while substitutional solid solution strengthening played a minor role.

关键词： high-entropy alloy HfNbTaTiZr refractory powder blend laser metal deposition additive manufacturing high-throughput synthesis

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Grain Refinement of CrCoNi Multi-principal-element Alloy

Grain Refinement of CrCoNi Multi-principal-element Alloy

引用

第十三届全国铸造年会暨2016中国铸造活动周

作者： Liu Xinwang Guillaume Laplanche aleksander kostka Suzana G.Fries Janine Pfetzing-Micklich Liu Gang Fan Zitian Easo P.George Department of Materials Design Ruhr-University Bochum State Key Laboratory of Materials Processing and Die & Mould Technology Huazhong University of Science and Technology Interdisciplinary Centre for Advanced Materials Simulation Ruhr-University Bochum

The equiatomic multi-principal-element alloy, CrCoNi, as a single-phase FCC solid solution, displays excellent strength-toughness properties that exceed those of all high entropy alloys, which is considered as a promising engineering alloy at cryogenic temperatures. Cast, as a common-used method to form complex-shaped components, is a necessary technique for engineering alloys, whereas the cast multi-principal-element alloys have not be systematically investigated previously. Here we study the grain refinement of cast CrCoNi alloy and their corresponding mechanical properties. The alloys were produced by arc melting and drop casting, which are much simpler than the preparation procedures of deformed alloys by cold deformation and recrystallization in the previous studies. The cast CrCoNi alloy consists with anisotropic coarse columnar grains with the average width of more than 210 m. Their microstructures, however, become equiaxed grains after grain modification which exhibit uniform fine equiaxed grains with the size of 76 m nearly throughout the entire ingots. The tensile tests at an engineering strain rate of 10-3 s-1 reveals that yield strength, ultimate tensile strength and elongation to fracture are all improved by grain refinement both at 293 and 77 K. Meanwhile, the cast alloy shows the comparable mechanical properties with the alloys after cold working and recrystallization. The corresponding mechanism was also discussed related to the constitutional supercooling.

关键词： multi-principal-element alloy grain refinement microstructures tensile properties

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：