Q. Y. Liu1
,
2) W. D. Fei2) and N. G. Liang1) 1) LNM
,
Institute of Mechanics
,
The Chinese Academy of Sciences
,
Beijing 100080
,
China 2) Schoolof Materials Science and Engineering
,
Harbin Institute of Technology
,
Harbin 150001
,
China
金属学报(英文版)
heinteracteach other among three kindsofthermalresidualstresses were analyzed firstly. Theresultsshown thatthe presenceof microstressandthermal mismatch stresshad noinflu enceon the measurement of macrostress, but macrostress can affect the measured value of thermal mismatch stress. Theeffectofthicknessofspecimen on thermalresidualstresses was discussed. Macrostresscan be neglected in thin specimen, thermal mismatch stressincreased with quenchingtemperatureincreasing, andobtainedtheir maximum valuesat400 ℃,then decreased . Forthethickspecimen, thecompressive macrostressatthesurfaceincreased with the quenching temperature increasing. The changing tendency of thermal mismatch stresswith quenchingtemperature wasquite differentcompared withthethinspecimens, which ob tainedtheir minimum valueat400℃.
关键词:
thermalresidualstresses
,
null
,
null
Journal of Physical Chemistry B
Size-controlled gold nanocrystals were conveniently synthesized through direct electroreduction of bulk AuCl4- ions in the presence of poly(N-vinylpyrrolidone) (PVP). PVP greatly enhanced the gold particle formation process and also significantly retarded the gold electrodeposition process, allowing the electrochemical synthesis of gold nanocrystals to be carried out in the form of simple electroreduction. This novel electrochemical method may be extended to synthesis of other noble metal nanoparticles with controllable size on a large scale. The PVPK90-protected gold nanocry.stals spontaneously self-assembled into nearly ordered 2D close-packed arrays and interesting 1D nanostructures. The aggregation of unstable PVPK17-protected gold nanocrystals resulted in the formation of ultrathin single-crystalline films. PVP plays multifunctional roles in controlling the size and shape of gold nanocrystals and in inducing individual gold nanocrystals to construct ID nanostructures. The nanoparticle self-assembling technique based on PVP offers a simple, but effective, path to organize individual gold nanoparticles into various 1D and 2D nanostructured materials.
关键词:
shape-controlled synthesis;uniform silver nanowires;optical-properties;size control;nanoparticles;nanorods;transition;mechanism;nanomaterials;microscopy
K. Zhang
,
W.P. Shen
,
C.C. Ge
,
null
,
null
金属学报(英文版)
W / Cu functionally gradient materials (FGMs) containing 1% La2O3 and 1% TiC were prepared using graded sintering under ultra-high pressure (GSUHP). The specimens have been found to exhibit low porosity (11.57% and 11.35%, respectively). Shearing strength of the specimens between layers is good. Moreover, the specimens have still demonstrated good performance in testing thermal-shock resistance. When power density of laser is 200MWm-2, the specimens have been tested for thermal-shock resistance (1000 times); the specimens that contained 1% La2O3 were not subjected to damage, whereas those that contained 1% TiC began to crack. Finally, effect of additives on thermal-shock resistance was also preliminarily discussed.
关键词:
W/Cu
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null
,
null
,
null
刘福田
,
王守德
,
常钧
,
黄世峰
,
芦令超
,
程新
硅酸盐通报
doi:10.3969/j.issn.1001-1625.2004.03.006
制备了钨铜酸锶掺杂PZT三元体系压电陶瓷,测量了不同烧结温度和不同组成的材料的压电常数值,以压电常数为依据,确定了不同组成的材料的最优烧结温度及在最优烧结温度下材料的压电常数.研究了钨铜酸锶的掺杂量对材料机电耦合系数和机械品质因数的影响.并对不同组成的材料进行了XRD和SEM分析,研究了材料的物相组成和微观结构对材料性能的影响.讨论了Sr2+,W6+,Cu2+离子对PZT压电陶瓷进行改性的作用机理.实验结果表明,钨铜酸锶可对PZT材料进行较好的改性作用,使材料的压电常数提高到570pC/N.
关键词:
PZT
,
掺杂
,
钨铜酸锶
,
压电常数
姚春发
,
李财富
,
刘志权
,
尚建库
无机材料学报
doi:10.3724/SP.J.1077.2011.00649
以无机盐为前驱体, 利用溶胶?凝胶法固溶合成了(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3多铁性固溶体. XRD分析表明, 在0≤x≤1.0的掺杂范围内, 700℃煅烧所得产物都具有钙钛矿结构; x=0时得到的纯Pb(Fe2/3W1/3)O3为长程无序结构, x=1.0时可获得完全有序的纯Pb(Mg1/2W1/2)O3相, 其单胞为Pb(Fe2/3W1/3)O3单胞的2倍; 当0<x<1.0时, (1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3固溶体也为有序结构, 出现1/2 (111)及1/2 (311) XRD衍射峰, 且强度随掺杂系数x的升高逐渐增大. TEM分析证实, 煅烧产物为具有钙钛矿结构的单相固溶体, 而非两相复合物; 固溶相形貌以立方颗粒为主, 随掺杂量增加其晶胞常数线性增大, 而晶粒尺寸先减小后变大. 性能测试发现, 固溶相的磁学性能随x的增加而逐渐下降, 起因于抗磁性的Pb(Mg1/2W1/2)O3破坏了Pb(Fe2/3W1/3)O3原有的价键结构所致.
关键词:
多铁性材料
,
perovskite
,
Sol-Gel
,
ordering
,
magnetic property
姚春发
,
李财富
,
刘志权
,
尚建库
无机材料学报
doi:10.3724/SP.J.1077.2011.00649
以无机盐为前驱体,利用溶胶-凝胶法固溶合成了(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3多铁性固溶体.XRD分析表明,在0≤x≤1.0的掺杂范围内,700℃煅烧所得产物都具有钙钛矿结构;x=O时得到的纯Pb(Fe2/3W1/3)O3为长程无序结构,x=1.0时可获得完全有序的纯Pb(Mg1/2W1/2)O3相,其单胞为Pb(Fe2/3W1/3)O3单胞的2倍;当0＜x＜1.0时,(1-x)Pb(Fe2/3W1/3)O3-xPb(Mg1/2W1/2)O3固溶体也为有序结构,出现1/2(111)及1/2(311)XRD衍射峰,且强度随掺杂系数x的升高逐渐增大.TEM分析证实,煅烧产物为具有钙钛矿结构的单相固溶体,而非两相复合物;固溶相形貌以立方颗粒为主,随掺杂量增加其晶胞常数线性增大,而晶粒尺寸先减小后变大.性能测试发现,固溶相的磁学性能随x的增加而逐渐下降,起因于抗磁性的Pb(Mg1/2W1/2)O3破坏了Pb(Fe2/3W1/3)O3原有的价键结构所致.
关键词:
多铁性材料
,
钙钛矿结构
,
溶胶-凝胶
,
固溶有序
,
磁性能
International Journal of Modern Physics B
The EPR g factors g(//) and g(perpendicular to) for the six-coordinated Cu2+(1) site in YBa2Cu3O6+x are theoretically investigated from the perturbation formulas for a 3d(9) ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu2+(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu2+ cluster. Based on the calculations, the effective elongation (= 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Delta g (=g(//) - g(perpendicular to)). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.
关键词:
crystal fields and spin hamiltonians;electron paramagnetic resonance;Cu2+;YBa2Cu3O6+x;single-crystals;yba2cu3o7-delta;evolution;esr
臧洪俊
,
李正名
,
杨宇红
,
赵卫光
,
王素华
应用化学
doi:10.3969/j.issn.1000-0518.2006.03.003
通过5种糖基异硫氰酸酯(4)与β-氨基丁酸甲酯(3)经亲核加成反应,合成了5种N-(2-甲氧羰基-1-甲基)-乙基-(N'-D-乙酰基吡喃型糖)硫脲,所得化合物经元素分析、1H NMR测试技术确证了结构.生测结果表明,该类化合物对烟草花叶病毒(TMV)具有一定的诱导抗性,而对黄瓜花叶病毒(CMV)无诱导抗性.
关键词:
糖基硫脲
,
β-氨基丁酸
,
合成
,
生物活性
辛炳炜
,
孙昌俊
,
曲立强
,
曹晓冉
应用化学
doi:10.3969/j.issn.1000-0518.2003.06.019
在相转移催化条件下,2,3,4,6-四-O-乙酰基-1-溴-1-脱氧-α-D-吡喃葡萄糖1与6-(4-卤代苯基)-3(2H)-哒嗪酮2反应,合成了4种新的哒嗪酮葡萄糖苷3;然后用干燥的氨气在0～-5 ℃下处理,得相应的2-N-(β-D-吡喃葡萄糖-1-基)-6-(4-卤代苯基)-3-哒嗪酮4. 这些化合物的结构经IR、1H NMR、13C NMR及元素分析所证实.
关键词:
哒嗪酮葡萄糖苷
,
合成,相转移催化
