共查询到19条相似文献,搜索用时 718 毫秒
1.
2.
3.
4.
5.
6.
7.
以X射线衍射分析作参比,分析了高度三维有序到近乱层结构的9种六方氮化硼的红外和拉曼光谱,并进行了立方氮化硼的高温高压合成。光谱分析表明,随着晶性的降低,六方氮化硼的低频红外吸收峰的位置及拉曼谱线等基本振动光谱发生明显的特征性的变化,并伴随出现各自不同的次级光谱结构。合成结果表明,在触媒作用下,立方氮化硼的形成需要六方氮化硼原料有一定的结晶度,但立方氮化硼合成效果与六方氮化硼结晶度并非是简单的单调关系。对振动光谱和合成试验的结果进行了讨论。 相似文献
8.
9.
10.
11.
Abstract The effect of chemical composition of the crystallization medium in synthesis on and some properties of cubic boron nitride (cBN) has been studied. Cubic BN crystals with the lowest free boron content and a boron-nitrogen ratio close to the stoichiometric one are grown in a multicomponent crystallization medium in a Li3N-BN system. These crystals are characterized by a higher strength and thermal stability. 相似文献
12.
L. M. Gameza 《高压研究》2013,33(1-6):373-378
Abstract We have investigated the effect of beryllium additions on the kinetics of conversion of hexagonal graphite-like BN to cubic BN (hBN → cBN) as well as on the linear rate of cBN crystal growth in a Li-B-N (H, Be) system. Experiments were performed in the temperature range 1940-2080K at a pressure of 4.3GPa. With the addition of 0.25 and 0.50wt.% beryllium the activation energy of the cBN formation process is found to be 45.8 and 42.0kJ/mol, respectively. The resulting crystals showed p-type conductivity. The activation energy of the impurity carriers for the samples with 0.25 and 0.50 wt.% beryllium additions equalled 0.22 and 0.17eV, respectively. 相似文献
13.
Growth and annealing study of hydrogen-doped single diamond crystals under high pressure and high temperature 下载免费PDF全文
A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 C to 1350 C.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp 3-CH 2-symmetric(2850 cm-1) and sp 3 CH 2-antisymmetric vibrations(2920 cm-1).The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the sp 3 C-H bond is rather stable in diamond crystals. 相似文献
14.
利用FeMn粉末触媒在国产六面顶压机上进行了合成金刚石单晶的实验,研究了高温高压条件下(5.7 GPa、1 550 ℃),石墨-FeMn粉末触媒体系中金刚石单晶的生长特性。通过光学成像显微镜观测表明:合成出的金刚石单晶呈浅黄色,晶形完整,且都是八面体,晶体里含有白色物质,粒度集中在0.3~0.5 mm;通过扫描电镜观测了晶体的表面形貌,表面有熔坑;通过穆斯堡尔谱,发现粉末触媒里主要是FeMn合金和独立状态的Fe,金刚石内部主要是Fe和Fe3C;利用X射线荧光光谱,检测出样品里有Fe和Mn元素。 相似文献
15.
The tight-binding method has been used to calculate the density of states and X-ray photoelectron spectra of valence electrons in BN and SiC cubic crystals. It is shown that s- and p-states of atoms of various components contribute differently to the spectrum. 相似文献
16.
17.
Formation and crystal structure of metallic inclusions in a HPHT as-grown diamond single crystal 总被引:2,自引:0,他引:2
L.-W. Yin N.-W. Wang Z.-D. Zou M.-S. Li D.-S. Sun P.-Z. Zheng Z.-Y. Yao 《Applied Physics A: Materials Science & Processing》2000,71(4):473-476
One of the most important characteristics associated with crystal growth technology is the entrapment of inclusions by the
growing crystal. Diamond single crystals prepared under high temperature-high pressure (HPHT) usually contain metallic inclusions.
In the present paper, metallic inclusions in a diamond grown from a Fe-Ni-C system using the HPHT method have been, for the
first time, systematically examined by transmission electron microscopy (TEM). Energy dispersive X-ray spectrometry (EDS)
, combined with selected area electron diffraction (SAD) patterns, has been used to identify the chemical composition and
crystal structure of the metallic inclusions. The metallic inclusions were found to be composed mainly of cubic γ-(FeNi),
face-centered cubic (FeNi)23C6, ortho-rhombic Fe3C and hexagonal Ni3C, which may have been formed through the entrapment of molten catalyst by the growth front or through reaction of the trapped
melt with contaminants in the diamond.
Received: 19 June 2000 / Accepted: 21 June 2000 / Published online: 16 August 2000 相似文献
18.
L. V. Astaf'eva F. F. Gavrilov B. L. Dvinyaninov V. P. Panov 《Russian Physics Journal》1971,14(10):1385-1388
Nonactivated LiH crystals and crystals of LiH with Mg, In, Tl, Sn, Sb, and Bi impurities are investigated. Photoconductivity is found in luminescent crystals. The temperature dependence of the electrical conductivity and photoconductivity in the temperature range of 100–570 ° K is measured. Volt-ampere characteristics of the dark current and photocurrent in fields up to 104 V/cm at various temperatures are obtained. Data is presented on the inertia of the photocurrent and its dependence on the intensity of the exciting light. Conclusions are drawn concerning some connection of LiH photoconductivity with the type of activating impurity, the absence of a connection with the brightness of the luminescence, and the specific role of photoconductivity in color centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 10, pp. 94–98, October, 1971. 相似文献
19.
V. E. Yurasova S. S. Elovikov E. Yu. Zykova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(3):328-341
Results obtained in studying the sputtering of single crystals of hexagonal, rhombohedral, and cubic boron nitride modifications by computer simulations are reported. Data on sputtering the (0001) face of BN in two graphite-like modifications and the (111) face of BN crystals with a cubic lattice are presented. The energy and angular dependences of the sputtering yields and spatial and energy distributions of sputtered particles are considered for the cases of normal and oblique ion incidence. Specific features of the anisotropy of spatial distributions of sputtered particles and mechanisms of their formations are analyzed. 相似文献