Anne E Shanahan
,
Mary McNamara
,
James A Sullivan
,
Hugh J Byrne
新型炭材料
doi:10.1016/S1872-5805(17)60121-5
采用原位还原技术制备出以单壁碳纳米管、炭黑(P90)和TiO2为支撑的3种金纳米复合材料,并通过多种表征手段来探讨物理性能.再将他们作为1-苯基乙醇、2-苯基乙醇和苯甲醇的绿色需氧氧化杂化催化剂来测试稳定性.在所有反应中,与P90和TiO2相比,以单壁碳纳米管作支撑的金纳米杂化催化剂呈现出最优的反应效率和特异性.这些金纳米杂化催化剂经多次反应循环后反应活性衰减很小,从而能被重复使用.同时探讨了金纳米杂化催化剂活性高的原因,包括颗粒形貌、尺寸和支撑体性能.可以推断,基底上功能团迁移的位置、支撑材料的性质和活性金纳米颗粒相的颗粒尺寸分布均有助于使这些催化剂在反应中显示出高的选择性.
关键词:
芳香的
,
醇
,
金
,
纳米催化剂
,
选择性
J. T. Niu
,
H. T. Li
,
X. D. Meng and P. Karjaleinen 1) Analysis and Measurement Center
,
Harbin Institute of Technology
,
Harbin 150001
,
China 2) Department of Mechanocal Engineering
,
The University of Oulu
,
Finland
金属学报(英文版)
With the development of modern science and technology, especially computer science, the numerical simulation method has been widely used in material hot-working. Mary achievements have been made in this field by using the numerical simulation method. The numerical simulation method, especially finite element method fully described in this paper.Applications of the numerical simulation method in material hot-working are also discussed. Finally, the future of the numerical simulation method is outlined.
关键词:
numerical simulation
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null
,
null
J.X.Dong
,
M.C.Zhang
,
S.K.Mannan
金属学报(英文版)
INCONEL725 is a highly corrosion resistant nickel based alloy capable of being age-hardened to high strength levels.The microstructure observations and the phase iden-tification after a standard heat treatment were investiguted.The results show that the precipitation phases include the strengthening phases γ′，γ″and δ phase,pri-mary carbide phase TiC,as well as M6C corbide and a little extent MC(mainly TiC) precipitates which nucleate mainly at grain boundaries.An isothermal aging study was carried out on this alloy for up to 10000 hours at 599℃.This additional aging did not affect the tensile strength.However,microstructures show that the thermal exposure has a little additional effect.With increasing the exposure time,the size of γ″ phase slightly increases,almost no change for γ′ phase,while M6C carbides pre-cipitated at grain boundaries have an increased and complex tendency on a few grain boundaries.The experimental results illustuate the excellent structure stability of the age-hardenable IN725 at 599℃.
关键词:
superalloy
,
null
,
null
Y.D.Xiao
,
W.X.Li
,
D.Jacovkis
,
M.T.Clavaguera-Mora
,
J.Rodriguez-Viejo
,
N.Clavaguera
金属学报(英文版)
Rapidly solidified Al87Ni7Cu3Nd3 metallic glasses, prepared by using melt spinning, were treated under both isothermal and non-isothermal regime. The amorphous rib-bon and the annealed samples were closely examined by means of differential scan-ning calorimetric, conventional X-ray diffraction and high resolution transmission electron microscopy with selected-area electron diffraction, with special interest in pri-mary crystallization into α-Al nanocrystalline particles, in order to understand struc-tural characteristics of Al-based amorphous/nanocrystalline alloys, and nucleation and grain growth mechanism on the nanometer scale during primary crystallization. The results show that, the as-prepared ribbons are fully amorphous and homogeneous in the micron scale, but contain high density of quenched-in clusters or crystallite embryos. Primary crystallization mainly leads to formation of two-phase mixture of α-Al crystal and residual amorphous phase. The annealed ribbons exposed isother-mally at 110℃ for 5, 130 minutes and heated continuously up to less than 310℃ at 40℃/min consist of large amount of α-Al fec crystal nanoparticles dispersed uni-formly in an amorphous matrix. However, a very little amount of finer orthorhombic Al3Ni intermetalics particles exist in the annealed ribbons heated up to 310℃. During primary crystallization, the leading kinetic mechanics to impede growth of the α-Al crustal is soft impinaement, instead of geometric impinqement.
关键词:
rapid solidification
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null
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null
