孙坚
利用高分辨电子显微镜对材料的晶体缺陷和微结构进行分析表征、特别是应用电子能量损失谱并结合密度函数理论研究研究材料的电子结构;材料性质的计算机原子模拟计算和基于密度函数理论的量子力学计算;金属间化合物以及先进陶瓷功能材料等
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- 姓名:孙坚
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学术头衔:
博士生导师
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学科领域:
材料科学基础学科
- 研究兴趣:利用高分辨电子显微镜对材料的晶体缺陷和微结构进行分析表征、特别是应用电子能量损失谱并结合密度函数理论研究研究材料的电子结构;材料性质的计算机原子模拟计算和基于密度函数理论的量子力学计算;金属间化合物以及先进陶瓷功能材料等
孙坚,教授,博士生导师。1984年毕业于浙江大学材料科学与工程系,1984-1986年上海电器科学研究所工作,1989、1992年上海交通大学材料科学系获硕士、博士学位。1992年上海交通大学材料科学与工程学院任教,1995-1997年香港城市大学物理及材料科学系合作研究,2003-2004美国亚利桑那州立大学John M. Cowley高分辨电镜中心高级访问学者,现为上海交通大学材料学院教授,博士生导师,上海市金属学会理事。主要研究方向:利用高分辨电子显微镜对材料的晶体缺陷和微结构进行分析表征、特别是应用电子能量损失谱并结合密度函数理论研究研究材料的电子结构;材料性质的计算机原子模拟计算和基于密度函数理论的量子力学计算;金属间化合物以及先进陶瓷功能材料等。先后承担了10余项包括国家自然科学基金项目、上海市科委基础重点项目以及国际合作项目的研究任务,在国内外学术刊物上累计发表学术论文80余篇,获国家发明专利1项,钛铝锰系金属间化合物晶体结构X射线研究结果被国际衍射数据中心 (International Center for Diffraction Data) 收录。
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【期刊论文】THEORETICAL AND POSITRON ANNIHILATION STUDY OF POINT DEFECTS IN INTERMETALLIC COMPOUND Ni3Al
孙坚, JIAN SUN and DONGLIANG LIN (T.L. LIN)
Acta metall. Mater. Vol.42, No.1, pp.195-200, 1994,-0001,():
-1年11月30日
The equilibrium equation of point defects in Li2 types of intermetallic compounds was established in a new simple method, which is independent of the chermical potentials. The formation energies of the relevant point defects in Ni3Al were calculated by EAM Potentials and statical relaxtions. The concentration of point defeots at 1000K as a function of bulk composition and the effect of temperature on them were studied for Ni3Al alloy. The results show that the Al-antisites are the constitutional defects in hypostoichiometric Ni3Al and the Ni-antisite defects in hyperstoichiomctric Ni3Al. The two types of vacancies belong to thermal defects. The positron annihilation technique was also conducted to measure the concentration of vacancies in Ni3Al alloys with and without boron. Although vacancies interact with the boron dopant, the changes of vacancy concentration in Ni3Al Alloys can not be considered as the main reason in explaining the effect of stoichiometry on the segregation of boron. The effect of stoichiometry on diffusion in Ni3Al alloys was discussed additionally.
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孙坚, S.M. ZHU and S.C. TJONG
VOLLME 28A, APRIL 1997,-0001,():
-1年11月30日
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孙坚, J. Sun*, J.X. Zhang, Y.Y. Fu, G.X. Hu
Materials Science and Engineering A329-331(2002)703-707,-0001,():
-1年11月30日
Microstructural evolution of the ordered L12+DO22 multiphase Al67Mn8Ti24Nb1 alloy during mechanical milling and subsequent annealing were investigated by X-ray diffractometer (XRD), transmission electron microscope (TEM) and hot-stage TEM. The transitions induced by severe plastic deformation during mechanical milling with increase of milling time were as follows: L12+DO22→disordered fcc supersaturated solid solution→amorphous structure. The amorphization of the Al67Mn8Ti24Nb1 alloy resulted from the increase of the free energy by introducing high dense nano-crystalline grain boundaries and the large internal lattice strain caused by the super-saturated dissolving of the Al3(TiNb) second phase in fcc solid solution. Transitions during subsequent annealing of the as-milled powders were amorphous-fcc crystalline transition at 250℃, disorder fcc transforming into the L12 ordered structure at 300℃ and DO22 structured second phase precipitating in the L12 matrix around 500-650℃, meanwhile grains growing up to the sub-micron.
A: trialuminides, C: mechanical alloying and milling, F: transmission electron microscopy
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【期刊论文】Dislocation dissociations and fault energies in Ni3Al alloys doped with palladium
孙坚, J. Sun a, b, *, C.S. Lee b, J.K.L. Lai b, J.S. Wu a
Intermetallics 7(1999)1329-1335,-0001,():
-1年11月30日
Dislocation structures in polycrystalline Ni3A1 alloy doped with palladium deformed at room temperature have been investigated by transmission electron microscopy. The structure consists mainly of dislocations dissociated into a/2<011> super partials bounding an anti-phase boundary (APB). Dislocations dissociated into a/3<112> super Shockley partials bounding a superlattice intrinsic stacking fault (SISF) were often observed. The majority of the SISFs are truncated loops, i.e. the partials bounding the SISF are of similar Burgers vector. These faulted loops are generated from APB-coupled dislocations, according to a mechanism for formation of SISFs proposed by Suzuki et al. (Suzuki K, Ichihara M, Takeuchi S. Acta Metall 1978;26:183) and recently modified by Chiba et al. (Chiba A, Hanada S. Philos Mag 1994; 69:751). The APB energies for {111} and {100} slip planes are measured to be 144
Dislocation
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孙坚, J. Sun, , S.J. Liu, N. Newman, and David. J. Smith
Mat. Res. Soc. Symp. Proc. Vol. 783,-0001,():
-1年11月30日
Ordered structures of Ba (Cd1/3Ta2/3) O3 ceramics with and without boron additive were investigated systemically by electron diffraction and high resolution transmission electron microscopy. The results showed a well-ordered structure of 1:2 with hexagonal symmetry for Ba (Cd1/3Ta2/3)O3 with boron additive. No significant changes in ordered structures were observed after long-period annealing. The 1:2 ordered domain structures (average domain size~18nm) and high-density domain boundaries induced by ordering were observed for Ba (Cd1/3Ta2/3) O3 without boron additive sintered at relatively high temperature. The sintering process has a profound influence on the microstructure of Ba (Cd1/3Ta2/3) O3 ceramics.
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孙坚, Shaojun Liu, Jian Sun, David J. Smith, Richard Taylor, N. Newman a)
J. Mater. Res., Vol. 19, No. 12, Dec 2004,-0001,():
-1年11月30日
The use of boron as a sintering aid reduces the sintering temperature, enhances the sintering density, and improves the microwave properties of Ba (Cd1/3Ta2/3)O3 ceramic dielectrics. Observations by transmission electron microscopy indicate that the liquid sintering mechanism contributes to the improvement in sintering density for boron concentrations exceeding 0.5wt%. The introduction of as small as 0.01% boron also results in the production of high-density samples (-95%), presumably indicating that a point defect mechanism may also play an important role in the sintering process. X-ray diffraction data combined with high-resolution transmission electron microscopy images show that boron-doped Ba (Cd1/3Ta2/3)O3 ceramic material has a well-ordered hexagonal structure. Annealing treatment is found to improve the microwave properties. The best sample has a dielectric constant of 32, a temperature coefficient of resonant frequency of 80±15 ppm/℃, and a quality factor of >25,000 at 2GHz.
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孙坚, J. Sun, Shaojun Liu and N. Newman, M.R. McCartney, David. J. Smith
J. Mater. Res., Vol. 19, No. 5, May 2004,-0001,():
-1年11月30日
The microstructure of Ba (Cd1/3Ta2/3)O3 ceramics with boron additive was investigated by high-resolution and analytical electron microscopy. Superlattice reflections were present at positions of (h
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【期刊论文】Ordered domains and boundary structure in Ba (Cd1/3Ta2/3) O3 perovskite dielectrics
孙坚, J. Sun a), Shaojun Liu and N. Newman, David J. Smith b)
APPLIED PHYSICS LETTERS VOLUME 84, NUMBER 19 10 MAY 2004,-0001,():
-1年11月30日
Ordered domains and boundaries have been observed in Ba(Cd1/3Ta2/3)O3 perovskite dielectrics by electron microscopy. Individual nanoscale domains were found to be well ordered with hexagonal symmetry. Electron diffraction revealed a twinned crystallographic relationship between domains. High-resolution electron microscopy showed further details of the boundary structure. Conservative twin boundaries along the 001! and 110! planes and nonconservative antiphase boundaries with a projected displacement vector of the type [001] were observed. The relationship between the energy and structure of the domain boundaries is briefly discussed.
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孙坚, J. SUN†‡, and B. JIANG§
Philosophical Magazine, 11 October 2004 Vol. 84, No. 29, 3133-3144,-0001,():
-1年11月30日
Ab initio calculations have been used to investigate the phase stability, mechanical properties and electronic structure of ZrCr2 Laves phase compounds, based on the method of augmented plane waves plus local orbitals with the generalized gradient approximation. The calculated lattice constants for the C15, C36 and C14 structures are in good agreement with experimental values. The calculation of heats of formation showed that C15 is a ground-state phase, whereas C36 is an intermediate phase and C14 the high-temperature phase. The elastic constants and elastic moduli for the C15 structure were calculated systematically and compared with experiments and previous theoretical calculations. The intrinsic and extrinsic stacking fault energies are found to be 112 and 98 mJm-2, respectively. The equilibrium separations between Schockley are also predicted using the calculated elastic moduli and stacking fault energies. Finally, the calculated electronic structures of these Laves phases are discussed based on these results.
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孙坚, J. Sun*, B. Jiang, David J. Smith
PHYSICAL REVIEW B 69, 1(2004),-0001,():
-1年11月30日
Laves-phase compounds TiCr2 and TiCo2 have been investigated by electron energy loss spectroscopy (EELS), and abinitio calculations have also been performed to relate the experimental spectra based on the method of augmented plane waves plus local orbitals (APW+lo) with the generalized gradient approximation. It is shown that the normalized EELS cross sections of Ti L2, 3 edges change only slightly between TiCr2 and TiCo2 compounds, and that variations of the calculated valence charge redistributions between these compounds are negligible. Therefore, there are no significant charge transfers between Ti and Cr (Co) atoms, and the local charge neutrality approximation is valid in these compounds. The charge densities of these compounds were also theoretically investigated. The results reveal a relatively strong covalent nature of atomic bonds between Cr-Cr (Co-Co) atoms compared with that between Ti and Cr (Co) atoms in TiCr2 and TiCo2, respectively. It is also demonstrated that the covalent bonding of the atoms in TiCo2 is stronger than that in TiCr2. This result could explain the significant difference of the calculated enthalpies of formation between TiCr2 and TiCo2 compounds.
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