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1.
通过测量B含量从0.00至2.22at%的单晶和多晶Ni3Al合金的正电子寿命谱,研究了单晶和多晶Ni3Al合金中的微观缺陷和电子结构。结果表明,多晶Ni3Al合金晶界中存在着开空间大于空位的缺陷。晶界缺陷处参与形成Ni-Ni和Ni-Al键的价电子浓度比基体或位错处的低,晶界是结合力弱化区域。偏聚到Ni3Al合金缺陷上的B与缺陷处的Ni或Al原子形成强的共价键而增强了这些地方的结合力。以间隙方式固溶到Ni3< 关键词:  相似文献   

2.
研究了掺Ba对Bi2Sr2-xBaxCaCu2Oy(0≤x≤0.15,0.3)单晶和多晶样品超导电性的影响,结果表明,有少量Ba2+离子进入了超导相,且有固溶度极限.对于2212相单晶,c轴参数和Tc均随Ba含量增加而增加;对于慢冷多晶样品,掺Ba可明显提高Tc;然而对于淬大多晶样品,Tc没有明显变化,用掺Ba 关键词:  相似文献   

3.
本文对Ge/An,Ge/Ag,双层膜和Ge-An,Ge-Ag合金膜的退火过程进行了透射电子显微镜观测,对Ge/多晶Au(或Ag)还进行了加热过程的原位观测。观测表明,多晶Au和单晶Au膜的存在使非晶Ge的晶化温度Tc的下降显著不同,可由晶界三叉点等处为非晶Ge的有利形核位置来解释,双层膜的缩聚区中由于局域优先晶化的影响,不仅Tc(=100℃)比非缩聚区中(Tc=150℃)低,而且形成直径为1—2μm的Ge大晶粒,而Ge/多晶Ag和Ge/单晶Ag膜的Tc均约为280℃,合金膜中金属含量较低时(CAu<17at%,CAg<18at%),Tc高于相应的Ge/多晶Au(Ag)膜;金属含量较高时,Tc低于Ge/多晶Au(Ag)膜。这说明过饱和金属原子的存在使得非晶Ge的晶化势垒大大降低。 关键词:  相似文献   

4.
铁基纳米晶合金的热膨胀研究   总被引:1,自引:0,他引:1       下载免费PDF全文
研究了铁基纳米晶合金Fe13.5CuNbSi13.5和Fe91Zr的热膨胀特性,并与相应成分的非晶合金做了比较。结果表明,在居里温度以下,纳米晶合金的热膨胀系数比非晶合金大得多,而在居里温度以上,两者几乎相等。认为上述的热膨胀的差别可能与铁基非晶态合金中存在的因瓦效应有关。 关键词:  相似文献   

5.
介绍了一种基于纳米粉末真空烧结技术的新型固体激光材料——Yb:Y2O3多晶陶瓷的制备工艺、物理化学特性、能级结构和光谱特性,并与Yb:YAG单晶进行了对比.采用紧凑型有源镜激光器(CAMIL)的抽运方式,验证了Yb:Y2O3透明陶瓷的激光输出性能.在35W的最大抽运功率下,得到波长1078 nm,功率10.5 W 的连续激光输出,斜率效率达到37.5%.实验中还观察到激光输出波长随抽运功率增加而红移以及随输出耦合镜变化而漂移的现象.Yb:Y2O3多晶陶瓷是一种理想的激光材料,不仅具有与Yb:YAG单晶同样优秀的物理化学性能和光谱特性,而且其热导率和发射带宽约为Yb:YAG单晶的两倍,非常适合于高亮度激光器和超短脉冲激光器领域的发展应用. 关键词: 2O3陶瓷')" href="#">Yb:Y2O3陶瓷 陶瓷激光器 透明陶瓷  相似文献   

6.
Cr3+:Al2O3透明多晶陶瓷光谱特性分析   总被引:4,自引:0,他引:4       下载免费PDF全文
曾智江  杨秋红  徐军 《物理学报》2005,54(11):5445-5449
对透光性良好的Cr3+:Al2O3透明多晶陶瓷的光谱性能 进行了研究,其吸收光谱中吸收峰与单晶红宝石相一致,按吸收光谱和Tanabe-Sugano能级 图,算出其晶场强度参数Dq及Racah参数B分别为1792cm-1, 689cm -1,Dq/B=2.6,陶瓷中Cr3+离子所处格位的晶体场强 比单晶弱一些,但Cr3+:Al2O3透明陶瓷仍属于强场晶 体材料;当Cr3+掺杂浓度到达0.8wt%时,陶瓷的发射谱仍保持较好的R线发射 ;随Cr3+掺杂浓度的增大,激发峰位发生“红移”.在Cr3+:Al2O3透明多晶陶瓷的荧光谱上,发现一个波长为670nm的发射峰,经激发 谱确认为Cr3+的发射峰. 关键词: 氧化铝 透明陶瓷 离子格位 光谱性质  相似文献   

7.
王娜  唐壁玉 《物理学报》2009,58(13):230-S234
运用第一性原理方法研究了L12型铝合金相Al3Sc和Al3Zr的晶体结构、电子结构和弹性.结合能和形成能的计算表明,两种合金具有较强的合金化能力,且Al3Zr较Al3Sc具有更强的结构稳定性.电子结构分析表明,费米能级以下较多的价电子数决定了Al3Zr具有较强的结构稳定性.计算并分析比较了两种合金相的单晶弹性常数(C11C12C44)以及多晶弹性模量(体弹性模量B、剪切模量G、杨氏模量Y、泊松比ν和各向异性因子A).通过对比实验和其他理论计算结果,进一步分析和解释了两种合金相的力学性质. 关键词: 铝合金 第一性原理 结构和电子性质 弹性  相似文献   

8.
邢雪  王小飞  张庆礼  孙贵花  刘文鹏  孙敦陆  殷绍唐 《物理学报》2014,63(24):248107-248107
LuTaO4是最高密度的闪烁体基质, 研究它的结构及其相变对单晶制备具有指导意义. 用固相法制备了Lu2O3和Ta2O5摩尔比为1:1时在不同温度下形成的多晶粉末, 用X射线衍射及Rietveld全谱拟合研究了多晶粉末的物相和结构. 结果表明, Lu2O3: Ta2O5摩尔比为1:1的样品在1740 ℃时合成的物相为M'-LuTaO4, 在1800 ℃时为M'-LuTaO4和M-LuTaO4的混合物, 在1840 ℃时全部转变为M-LuTaO4. 当温度升高到2058 ℃时, 样品呈熔融状态, 对淬火得到的样品进行结构精修, 给出了M-LuTaO4, Lu3TaO7和Ta2O5的晶胞和原子坐标参数, 它们的重量比分别占78.1%, 18.9%和3.0%. 这些结果为制备以LuTaO4为基质的高密度闪烁体单晶具有参考价值. 关键词: 4')" href="#">LuTaO4 相变 粉末衍射 Rietveld精修  相似文献   

9.
为了全面理解过渡金属硫族化合物合金成分变化对其带隙及光学性能的影响,通过调控非金属生长源S粉和Se粉的比例,采用化学气相沉积法,制备了一系列具有不同成分的大尺寸单晶WS2xSe(2(1-x))合金.通过扫描电子显微镜、拉曼光谱、光致发光光谱等对其形貌、结构及光学性能进行了研究.实验结果表明:单层单晶WS2xSe(2(1-x))合金成分均匀且具有非线性光学特性.随着合金中非金属S含量的增多,单层WS2xSe(2(1-x))合金的拉曼峰发生蓝移;且其带隙也随S的增多而逐渐变大,发光和吸收峰位均逐渐蓝移.  相似文献   

10.
报道使用C60粉末,利用双炉装置,通过闭管汽相法生长C60单晶的实验及结果。C60单晶的质量很好,较大单晶的尺寸为0.5mm×0.61mm×1.0mm。X射线衍射和电子衍射图的分析得到室温下C60单晶为fcc结构,确定了晶格常数,还进行了Raman光谱实验,实验结果表明,热、冷区温度及两者的温度差是影响大尺寸C60单晶汽相生长的主要因素,对此进行了详细的讨论。 关键词:  相似文献   

11.
Soft magnetic ribbons of Finemet-type (Fe73.5Cu1Nb3Si13.5B9) alloys are synthesized by the twin-roller melt-spinning technique directly from the melt, at tangential wheel speeds of 15, 18, 19 and 20 m/s. The microstructure and the magnetic properties are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), thermo-gravimetric analysis (TGA) and hysteresis loops measurements. Samples cooled at 20 m/s are amorphous, while those quenched at lower wheel speeds are partially crystalline. All samples studied present saturation magnetization values (150-160 A m2/kg) higher than the commercial Finemet alloys (∼135 A m2/kg), obtained by controlled crystallization of amorphous single-roller melt-spun alloys. Optimal soft magnetic properties - σS=(154±8) A m2/kg and HC=(6.9±0.9) A/m - are found in samples quenched at 19 m/s, consisting of size-distributed bcc Fe-Si nanograins (∼18 nm in average) embedded in an amorphous residual matrix. A minority nanocrystalline magnetic phase (≤10 nm) is also detected.  相似文献   

12.
In this research, we detected superior values of the initial magnetic permeability for electrodeposited Ni–Co–P-M-type BaFe12O19 (BaM) composite films as magnetic soft–hard composites with a large amount of entrapped BaM particles. Furthermore, the initial magnetic permeability of Ni–Co–P-BaM composite films is significantly large and is comparable with corresponding values of the excellent corresponding values for permalloys, Sendust, Co-based amorphous alloys, nanocrystalline (Fe-based) and commercially sintered MnZn ferrite cores. Therefore, Ni–Co–P-BaM composite films are very attractive for magnetic devices, such as magnetic inductors, transformers, and magnetic recording heads.  相似文献   

13.
The superparamagnetism of an ensemble of ?-Fe2O3 nanoparticles with a mean size of 3.9 nm dispersed in a xerogel SiO2 matrix is studied by the Mössbauer spectroscopy method. It is shown that most nanoparticles at room temperature are in the superparamagnetic (unblocked) state. As the temperature decreases, the progressive blocking of the magnetic moments of the particles occurs, which is manifested in the Mössbauer spectra as the transformation of the quadrupole doublet into a Zeeman sextet. The analysis of the relative intensity of the superparamagnetic (quadrupole doublet) and magnetically split (sextets) spectral components in the range of 4–300 K provides the particle size distribution, which is in agreement with the transmission electron microscopy data. The values of the effective magnetic anisotropy constants (Keff) are determined, and the contribution of surface anisotropy (KS) is estimated for particles of various sizes. It is shown that the quantity Keff is inversely proportional to the particle size, which indicates the significant contribution of the surface to the magnetic state of the ?-Fe2O3 nanoparticles with the size of several nanometers.  相似文献   

14.
Nanoparticles of solid solution Fe x Pt1?x , where 0.25≥x≥0 (?fcc lattice) with γ-Fe2O3 shell (lattice of the spinel type) were synthesised and characterised by high-resolution transmission electron microscopy, energy dispersive X-ray analysis, electron energy loss spectroscopy, Mössbauer spectroscopy and magnetometry. From the point of view of magnetic properties, such two-phase particles are interesting because their core is antiferromagnetic or paramagnetic (at very small values of x) whereas the shell is ferrimagnetic. The size of the particles was in the range of several nanometers. The Mössbauer measurements revealed a blocking temperature of about 100 K above which the particles are superparamagnetic. Towards lower temperatures, the magnetic characteristics of an ensemble of such particles show an increase of magnetic rigidity.  相似文献   

15.
杨卫明  刘海顺  敦超超  赵玉成  窦林名 《物理学报》2012,61(10):106802-106802
晶粒尺寸在很大程度上决定了Fe基纳米晶合金的磁学性能,其随退火温度变化的物理机理是纳米晶领域重要的研究内容.研究了初始晶化温度与二次晶化温度之间退火1 h Fe基纳米晶合金晶粒尺寸随退火温度的变化,并建立了相应的模型.利用提出的模型分析了该温度范围内Fe基纳米晶合金晶粒尺寸随退火温度升高先减小后增大的物理机制. 研究发现,在初始晶化温度与二次晶化温度之间等时退火,当退火温度约为Fe基纳米晶合金熔点的0.6倍时其晶粒尺寸最小.在研究的温度区间内,理论研究结果与实验符合得较好. 本研究提供了一种快速获得小晶粒尺寸纳米晶合金的方法.  相似文献   

16.
Polycrystalline Fe3?x V x Al alloys with the DO3 type structure were investigated by magnetostatic and Mössbauer methods. In alloys with 0.2<x<0.5 the ferro- and superpara-magnetic phases coexist. For alloys withx≥0.5 these investigations showed that in spite of the lack of magnetic order, they are characterized by strong nonlinear variations of the magnetization in a magnetic field over a wide temperature range. This indicates the presence of magnetic clusters of Fe atoms with very large magnetic moments. Analysis of the magnetization isotherms indicates that in these alloys a distribution of magnetic moments of clusters (μc) from 10 μB to 104 μB exists.  相似文献   

17.
Well-crystallized ultrafine ZnFe2O4 particles of several nanometers in size have been prepared by the coprecipitation method, and their particle morphology and magnetic properties, especially at low temperatures, examined. Room-temperature X-ray diffraction, transmission electron microscopy, magnetization measurements at various temperatures from 300 K to 4.2 K, and Mössbauer spectroscopy at various temperatures from 300 K to 4.2 K, and at 4.2 K with a longitudinal magnetic field of 16.4 kOe applied have been employed. The formation of short-range and long-range magnetic order in small ZnFe2O4 particles above and below approximately 30 K is discussed. Below 30 K, the appearance of spontaneous magnetization and its hysteretic property is confirmed for small ZnFe2O4 particles.  相似文献   

18.
The formation of a short-range order in soft magnetic Fe-Si alloys depending on the annealing temperature has been investigated theoretically and experimentally. The B2-type short-range order has been observed in samples quenched from temperatures T > T C (where T C is the Curie temperature) with the content c Si close to the boundary of the two-phase region. Annealing at temperatures T < T C for the content c Si ≥ 0.08 leads to an increase in the fraction of regions with the D03-type short-range order. The mechanism of the formation of the short-range order in Fe-Si solid solutions has been analyzed by the Monte Carlo simulation with the ab initio calculated interatomic interaction parameters. It has been shown that the energy of the effective Si-Si interaction in bcc iron strongly depends on the magnetic state of the matrix. As a result, the B2-type short-range order is formed at T > T C and is fixed at quenching, whereas the D03-type shortrange order is equilibrium in the ferromagnetic state. The results reveal the decisive role of magnetism in the formation of the short-range order in Fe-Si alloys and allow the explanation of the observed structural features of the alloys depending on the composition and temperature.  相似文献   

19.
The quasi-lattice model has been used to study the concentration dependant thermodynamic properties and microscopic structure of Fe-Si alloys in molten state. We have determined the free energy of mixing, excess entropy of mixing, the concentration-concentration structure factor in long wavelength limit [SCC(0)] and the Warren-Cowley short range order parameter (α1) of Fe-Si liquid alloy at 1873 K. The observed asymmetry in the properties of mixing of Fe-Si alloy in molten state is successfully explained on the basis of the quasi-lattice model. The analysis suggests that the Fe2Si complexes are most likely to exist in the liquid state and are strongly interacting in nature. The theoretical analysis suggests that the pairwise interaction energies between the species depend considerably on temperature and the alloy is more ordered towards Fe rich region.  相似文献   

20.
We have observed magnetic anisotropy in bulk Nd55−xCoxFe30Al10B5 (x=10, 15 and 20) alloys prepared by copper mold suction casting method with a presence of external magnetic field (quenching field) μ0H=0.25 T. By changing direction of the measuring field from perpendicular to parallel one in comparison with that of the quenching field, coercive force of the alloys slightly decreases while remanent magnetization and squareness of hysteresis loop increase more clearly. It is also found that the higher Co-concentration in the alloys the larger magnetic anisotropy is induced. The structure analyses manifest nanocrystalline particles embedded in residual amorphous matrix of the alloys. The size of the particles is in range of 10-30 nm and their crystalline phases consist of Nd2(Fe,Co)14B, Nd3Co, Nd3Al, NdAl2 and Nd.  相似文献   

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