G.M. Cao
,
C.G. Li
,
Z.Y. Liu
,
D. Wu
,
G.D. Wang
,
X.H. Liu
金属学报(英文版)
Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten
pool, corresponding control strategy is also proposed.
关键词:
Twin-roll strip casting
,
null
Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences
This paper presents a cluster approach to the calculation of the g factors for 3d(7) ions in cubic octahedral crystals, in which the parameters related to the configuration interaction and the covalency reduction effects are obtained from optical spectra of the studied crystals, and so no adjustable parameters are applied. From the approach, the g factors for MgO:Co2+ and CaO:Co2+ are calculated. The calculated results show good agreement with the observed values. The experimental values of g < 4.333 (the first order value in absence of configuration and covalency interactions) for MgO:Co2+ and g > 4.333 for CaO:Co2+ are also explained.
关键词:
electron paramagnetic resonance (EPR);crystal-field theory;Co2+ ion;MgO;CaO
张锡平
,
陈树江
,
薛文东
,
孙加林
,
马莹
,
石桐军
耐火材料
doi:10.3969/j.issn.1001-1935.2008.01.007
以镁钙砂、中档镁砂、高纯镁砂粉、单斜氧化锆(m-ZrO2)、锆英石等为原料,研究了ZrO2的加入形式与加入量对MgO-CaO砖性能的影响.结果表明:当ZrO2以m-ZrO2的形式加入到MgO-CaO砖中时,可以提高试样的常温性能、抗水化性、抗热震性等,m-ZrO2加入量(质量分数,下同)为2%～7%时,试样具有良好的常温性能,加入量为5%时抗水化效果较好,加入量为10%～15%时抗热震效果较好;当ZrO2以锆英石细粉的形式加入时,会明显提高试样的抗水化性及抗热震性,锆英石加入量为5%时,试样的抗水化性及抗热震性优越,但随着锆英石加入量的增加,试样的体积密度、强度明显下降,加入量大于10%以后,制品大多疏松开裂.
关键词:
氧化锆
,
镁钙砖
,
锆英石
,
抗水化性
,
抗热震性
Communications in Theoretical Physics
The calculations of the whole energy spectrum and the g factor of the ground state for CaO:Ni2+ at normal pressure and their pressure-induced shifts have been carried out on the basis of the theory of pressure-induced shifts and the diagonalization of the complete dg energy matrix in a regular octahedral field. The calculated results are in very good agreement with experimental data. The physical essentials of the pressure-induced shifts of typical levels and g factor for the ground state have been revealed by using the wavefunctions and energy spectra at various pressures.
关键词:
high pressure;ligand field;energy spectra;optical properties;electronic spin resonance
马敬翙
,
刘光明
,
曾潮流
,
杜楠
,
赵晴
表面技术
doi:10.3969/j.issn.1001-3660.2006.04.005
采用电化学方法、扫描电镜、能谱分析等技术,研究了常温下镍基高温合金M17和M38G在NaCl溶液和含S2O2-3的NaCl溶液中的腐蚀行为.结果表明,在含质量分数为3.5% NaCl的溶液中,M17和M38G均会遭受严重的点腐蚀;向NaCl溶液(NaCl质量分数为3.5%)添加Na2S2O3(Na2S2O3质量分数为1.5%)后,由于溶液中的S2O2-3在试样表面活性点与Cl-竞争吸附并与H+结合,使两种合金的点蚀均受到抑制;M38G中存在微量的Nb、Ta、Mo等元素使得M38G合金在NaCl溶液中的耐腐蚀性能明显优于M17合金.
关键词:
镍基
,
高温合金
,
点蚀
,
电化学方法
,
腐蚀行为
林水东
,
丁马太
功能材料
用示差扫描量热法(DSC)考察了聚丙烯(PP)、聚丙烯/云母(PP/M)和聚丙烯/聚(丙烯-g-甲基丙烯酸甲酯)/云母复合材料(PP/PP-g-MMA/M)的非等温结晶过程.用Avrami方程和Ozawa方程对上述过程进行分析,n、t1/2、F(T)、Tp等参数表明,M和PP-g-MMA,特别是PP-g-MMA的掺入改变了PP的结晶成核和生长机理.用Dobreva方法分析填料的成核活性,ε数值表明,M有较强的成核活性,PP-g-MMA的掺入又进一步增强其成核活性,从而使结晶温度明显提高.Kissinger方法的计算结果表明,添加M可使PP的结晶活化能减小,再添加PP-g-MMA又使PP/M复合体系的结晶活化能进一步减小.
关键词:
聚丙烯
,
聚(丙烯-g-甲基丙烯酸甲酯)
,
云母
,
复合材料
,
非等温结晶动力学
Intermetallics
The phase transformation of alumina formed during oxidation of beta-NiAl coating prepared on M38G alloy by pack cementation was investigated. Oxidation experiments were conducted at 950 degrees C for various times from 2 to 180 min. The phase composition and microstructure of the oxide scales were investigated by using glancing angle XRD, AFM and SEM. The results showed that at the initial oxidation stage needle-like theta-Al2O3 was formed and then it covered the sample surface rapidly. The formation of alpha-Al2O3 grains beneath the theta-Al2O3 layer was favored by depletion of Al in the beta-NiAl coating during oxidation. alpha-Al2O3 preferred growing on the top (ridge) of beta-NiAl grains, which resulted in the formation of net-like alpha-Al2O3 inner layer. With increasing time, theta-Al2O3 transformed to alpha-Al2O3 gradually. After 180 min oxidation, most of alpha-Al2O3 grains transformed into alpha-Al2O3. A mechanism of excessive voids' formation at the oxide/coating interface was also proposed in this paper. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
nickel aluminides, based on NiAl;oxidation;phase transformations;coatings, intermetallic and otherwise;high-temperature oxidation;theta-alpha-al2o3 transformation;behavior;coatings;superalloy;transition;layers
Journal of Magnetism and Magnetic Materials
The electron paramagnetic resonance g factors g(parallel to) and g(perpendicular to) for the trigonal Er3+-V-K centers (where V-K denotes K+ vacancy) in KMF3 (M = Mg and Zn) are theoretically investigated from the perturbation formulas of the g factors for a 4f(11) ion in trigonal symmetry. In these formulas, the contributions to the g factors from the second-order perturbation terms and the admixture of various energy levels are taken into account. In the above trigonal centers, the impurity Er3+ resides in the octahedral M2+ site of both crystals, associated with one V-K in the C-3-axis due to charge compensation. By analyzing their g factors, we find that the impurity Er3+ in both centers would move towards the V-K by an amount DeltaZ along the C-3-axis due to electrostatic attraction. The calculated g factors for the Er3+ centers based on the above displacements DeltaZ show good agreement with the observed values. The validity of the results is discussed. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
electron paramagnetic resonance (EPR);defects and impurities;crystal-field and spin hamiltonians;Er3+;KMF3;(M = Mg and Zn);crystal-field;superposition-model;perovskite kmgf3;conversion;parameters;fluorides;kznf3
