W.Tong
,
N.Zhang
材料科学技术（英文）
Serrated plastic flows in an Al sheet (AA5182-H19) were first characterized temporally and spatially under quasistatic uniaxial tension. Discrete types B and C serrations or Portevin Le-Chatelier (PLC) bands started to appear at a plastic strain of 2.54% with an average stress drop of 2.5 MPa and an average time interval of 7.75 s between serrations. The width of the individual PLC bands was about twice of the thickness of the sheet (0.235 mm) and the plastic strain inside the bands was as high as 2%. V-notched tear test coupons made of the same Al alloy were then stretched under both continuous monotonic and periodic interrupted loading conditions and their crack initiation and growth processes were monitored by direct digital imaging. The crack tip opening angle (CTOA) and the crack tip opening displacement (CTOD) were measured to be about 2.5～3℃ and 0.07～0.1 mm, respectively. While no major load serrations were observed before crack initiation at the notch tip, discontinuous or intermittent crack advances or crack jumps were unambiguously detected in the crack growth stage. The unstable crack propagation in the AA5182-H19 sheet seems to be related closely with its strong dynamic strain aging behavior exhibited under quasistatic loading conditions at the ambient temperature.
关键词:
Crack growth
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null
,
null
,
null
Y.B. Hou
金属学报(英文版)
In this paper, the PMMA films doped with N,N'-diphenyl-N,N'-di(m-tolyl)-benzidineand rubrene were fabricated by spin coating, and the effect of photooxidation onthe photoluminescence of the doped PMMA thin films was investigated. The resultsshowed that under the irradiation of 350nm UV light, N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine can sensitized rubrene and results in the enhancement in the photooxrationof rubrene. The effect of photooxidation on the photoluminescence from rubrene w asmore obvious. Both lifetime measurement and in situ measurement of photolumines-cence showed that rubrene molecules exist in two chemical surroundings.
关键词:
photoluminescence
,
null
Ceramics International
The dispersion behavior of Si3N4 nanopowders prepared by laser-induced gas-phase reaction in a non-aqueous solvent, N-N-dimethylformamide (DNIF) was studied, and triethanolamine (TEA) was selected as a dispersant. One hundred and sixty-six-day sedimentation tests were used to study the stability of the suspensions. Photon correlation spectroscopy was employed to measure the sizes of aggregates and coagulation rates. TEA was proved an effective dispersant for nano-Si3N4 in DMF, presoaking treatment could enhance the effect of the dispersant. TEA 1.0 wt.% referred to Si3N4 and a 1-month-presoaking gave the best dispersion, the dispersion stability was improved from several minutes to several months, and the average size of the aggregates was reduced to about a twenty-fifth. The dispersion ability of TEA was believed being related to its strong affinities both to the powder surface and to the solvent. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.
关键词:
Si3N4;dispersion;nanopowders;N-N-dimethylformamide;triethanolamine;composite;powders
Journal of Magnetism and Magnetic Materials
We present first-principles study on the magnetic properties of the 3D metal-ligand coordination polymer [Cu(mal)(DMF)]n within the framework of density functional theory ( DFT) by using the full-potential linearized augmented plane-wave (FP-LAPW) method. The total and partial density of states ( DOS), the band structure, and the atomic spin magnetic moment of [ Cu( mal)( DMF)] n are calculated. The calculation reveals that [ Cu( mal)( DMF)] n is a ferromagnetic semiconductor. The calculated spin magnetic moment is about 1.000 mu B per molecule, which is in agreement with experimental value. (c) 2007 Elsevier B.V. All rights reserved.
关键词:
first-principles;electronic structure;ferromagnetic properties;complexes;acid
柴生勇
,
安忠维
液晶与显示
doi:10.3969/j.issn.1007-2780.2001.02.007
通过Ulmann缩合反应合成了在有机电致发光（OEL）显示器件上有使用前景的四苯基联苯二胺类空穴传输材料N， N′-二苯基-N， N′-双(3-甲基苯基)-［1， 1′-联苯］-4， 4′-二胺、 N， N′-二苯基-N， N′-双(4-甲基苯基)-［1， 1′-联苯］-4， 4′-二胺和N， N， N′， N′-四苯基-［1， 1′-联苯］-4， 4′-二胺。 对产品从混合物中分离的方法作了改进。 其产率及含量分别为85%、 97.6%； 95%、 98.5%； 70 %、 98.1% 。 对3种化合物均用红外光谱进行了表征。
关键词:
制备
,
四苯基二胺化合物
,
空穴传输材料
,
有机电致发光
沈颖旎
,
罗智伟
,
严新焕
催化学报
以硝基苯为原料, Pt/γ-Al2O3为催化剂,乙醇水溶液为溶剂和氢供体,采用原位液相加氢一步法合成了N-乙基苯胺和N,N-二乙基苯胺. 采用低温N2吸附-脱附、电感耦合等离子体发射光谱、X射线衍射、程序升温化学吸附和透射电子显微镜等对Pt/γ-Al2O3催化剂进行了表征,并考察了所制备催化剂的原位液相加氢性能. 结果表明,在温度为503 K、压力为5.0 MPa、空速为3.2 h-1、溶剂水含量为30%以及硝基苯浓度为8%的反应条件下,在Pt/γ-Al2O3催化剂上原位液相加氢合成N-乙基苯胺及N,N-二乙基苯胺有较好的结果,硝基苯转化率达到100%, N-乙基苯胺和N,N-二乙基苯胺的总收率达到99.5%. 讨论了硝基苯原位液相加氢合成N-乙基苯胺和N,N-二乙基苯胺的反应机理.
关键词:
铂
,
氧化铝
,
硝基苯
,
原位液相催化加氢
,
N-乙基苯胺
,
N
,
N-二乙基苯胺
,
乙醇
