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1.
A. A. Soltamova I. V. Il’in F. M. Shakhov S. V. Kidalov A. Ya. Vul’ B. V. Yavkin G. V. Mamin S. B. Orlinskii P. G. Baranov 《JETP Letters》2010,92(2):102-106
A giant concentration of nitrogen vacancy defects has been revealed by the electron paramagnetic resonance (EPR) method in
a detonation nanodiamond sintered at high pressure and temperature. A high coherence of the electron spins at room temperature
has been observed and the angular dependences of the EPR spectra indicate the complete orientation of the diamond system. 相似文献
2.
给出了一种由特殊炸药的爆轰参数确定不同种分子间势函数参数的方法:由基于统计物理的爆轰产物物态方程程序类CHEQ,计算炸药RX-23-AB,HNB和PETN的爆轰参数,反推分子间的相互作用.给出了炸药主要爆轰产物H2O,CO2和N2之间的非理想混合修正系数:KN2-H2O=1.03,kN2-CO2=1.035,kH2O-CO2=0.96,将本文确定的不同种分子间势函数参数用于计算炸药PBX9404的超高压雨贡纽,获得了与实验一致的结果,验证了方法和参数的合理性. 相似文献
3.
给出了一种由分子流体的冲击Hugoniot实验数据确定原分子之间和离解产物分子、原子相互间作用势参数的方法. 在较低压强下,采用Ross硬球微扰理论软球修正模型确定原分子之间的相互作用势参数;在较高压强下,采用基于统计物理的化学平衡方法来确定分子离解后的分子和原子之间的相互作用势参数. 与传统的由对应状态定律确定势函数参数的方法相比,所得到的势函数参数在很大的压强范围内都能较好地描述冲击实验.
关键词:
高温高压
化学平衡
冲击Hugoniot实验 相似文献
4.
FeNiMnCo-C体系中,在压力6.5 GPa、温度1280—1300℃的极端物理条件下,采用温度梯度法成功合成了硼(B)、硫(S)协同掺杂金刚石大单晶.通过傅里叶红外光谱测试对高温高压所制备金刚石中的杂质进行了表征.借助霍尔效应对典型金刚石样品的电输运性能进行了测试,测试结果表明:硼硫协同掺杂有利于提高p型金刚石的电导率,而且硼硫在合成体系中的添加比例可以决定金刚石的p, n特性.此外,第一性原理计算结果表明,合成体系中不同比例的硼硫协同掺杂对金刚石的p, n特性以及电导率有着直接的影响,计算结果与实验测试结果相吻合. 相似文献
5.
Feoktistov N. A. Sakharov V. I. Serenkov I. T. Tolmachev V. A. Korkin I. V. Aleksenskii A. E. Vul’ A. Ya. Golubev V. G. 《Technical Physics》2011,56(5):718-724
The aerosol deposition of detonation nanodiamonds (DNDs) on a silicon substrate is comprehensively studied, and the possibility
of subsequent growth of nanocrystalline diamond films and isolated particles on substrates coated with DNDs is demonstrated.
It is shown that a change in the deposition time and the weight concentration of DNDs in a suspension in the range 0.001–1%
results in a change in the shape of DND agglomerates and their number per unit substrate surface area N
s
from 108 to 1011 cm−2. Submicron isolated diamond particles are grown on a substrate coated with DND agglomerates at N
s
≈ 108 cm−2 using microwave plasma-enhanced chemical vapor deposition. At N
s
≈ 1010 cm−2, thin (∼100 nm) nanodiamond films with a root-mean-square surface roughness less than 15 nm are grown. 相似文献
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8.
Evolution of nitrogen structure in N-doped diamond crystal after high pressure and high temperature annealing treatment 下载免费PDF全文
In this paper, we have reported an investigation on the evolution of nitrogen structures in diamond crystals which contain nitrogen donor atoms in the range of 1500 ppm-1600 ppm following an annealing treatment at a high pressure of about 6.5 GPa and high temperatures of 1920 K-2120 K. The annealing treatment was found to completely transform nitrogen atoms originally arranged in a single substitutional form (C-center), into a pair form (A-center), indicated from infrared (IR) spectra. The photoluminescence (PL) spectra revealed that a small fraction of nitrogen atoms remained in C-center form, while some nitrogen atoms in A-center form were further transformed into N3 and H3 center structures. In addition, PL spectra have revealed the existence of two newly observed nitrogen-related structures with zero phonon lines at 611 nm and 711 nm. All these findings above are very helpful in understanding the formation mechanism of natural diamond stones of the Ia-type, which contains nitrogen atoms in an aggregated form. 相似文献
9.
Ge–Sn compound is predicted to be a direct band gap semiconductor with a tunable band gap. However, the bulk synthesis of this material by conventional methods at ambient pressure is unsuccessful due to the poor solubility of Sn in Ge. We report the successful synthesis of Ge–Sn in a laser-heated diamond anvil cell (LHDAC) at ~7.6 GPa &; ~2000 K. In situ Raman spectroscopy of the sample showed, apart from the characteristic Raman modes of Ge TO (Г) and β-Sn TO (Г), two additional Raman modes at ~225 cm?1 (named Ge–Sn1) and ~133 cm?1 (named Ge–Sn2). When the sample was quenched, the Ge–Sn1 mode remained stable at ~215 cm?1, whereas the Ge–Sn2 mode had diminished in intensity. Comparing the Ge–Sn Raman mode at ~225 cm?1 with the one observed in thin film studies, we interpret that the observed phonon mode may be formed due to Sn-rich Ge–Sn system. The additional Raman mode seen at ~133 cm?1 suggested the formation of low symmetry phase under high P–T conditions. The results are compared with Ge–Si binary system. 相似文献
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11.
P. G. Baranov I. V. Il’in A. A. Soltamova A. Ya. Vul’ S. V. Kidalov F. M. Shakhov G. V. Mamin S. B. Orlinskii M. Kh. Salakhov 《JETP Letters》2009,89(8):409-413
Individual nitrogen centers N0 and nitrogen pairs N 2 + have been detected and identified in natural diamond nanocrystals by means of the high-frequency electron spin resonance method. The N0 nitrogen centers have been observed in synthetic diamond nanocrystallites with a size of less than 10 nm produced by high-temperature high-pressure sintering of detonation nanodiamonds. Thus, the possibility of the stable state of impurity nitrogen atoms in diamond nanoparticles has been demonstrated. 相似文献
12.
Intrinsic paramagnetic defects in ~5 nm sized nanodiamonds, produced by various dynamic synthesis (DySND) techniques (detonation, shock-wave, pulsed laser ablation of solid carbon containing targets), have been studied by multi-frequency electron paramagnetic resonance (EPR). X-band (9-10 GHz) EPR spectra of DySND, in addition to the main intensive singlet Lorentzian-like EPR signal, reveal a low intensity doublet pattern within the half-field (HF) region (g ~ 4). On transferring spectra to the Q-band (34 GHz) the shape of the HF pattern changes and splitting between doublet components is reduced from 10.4 to 2.6 mT. The HF patterns observed are attributed to the 'forbidden' ΔM(S) = 2 transitions between the Zeeman levels of some spin-triplet (S = 1) centers. The model of two triplet centers with g ~ 2.003 and zero-field splitting parameters D(1) = 0.095 cm(-1) (TR1) and D(2) = 0.030 cm(-1) (TR2) satisfactorily describes experimental results at both microwave frequencies. The spin-triplet-type defects are observed in a wide variety of DySND samples irrespective of industrial supplier, cooling and carbon soot refinement methods, initial purity, disintegration, or subsequent targeted chemical modification. This indicates that the intrinsic defects with S = 1 in DySND systems are of universal origin. 相似文献
13.
A new structural phase of MgV2O6 was obtained by a high-pressure,high-temperature(HPHT) synthesis method.The new phase was investigated by the Rietveld analysis of X-ray powder diffraction data,showing space group Pbcn(No.60) symmetry and a = 13.6113(6) (1 = 0.1 nm),b = 5.5809(1) ,c = 4.8566(3) ,V = 368.93(2) 3(Z = 4).High pressure behavior was studied by Raman spectroscopy at room temperature.Under 22.5 GPa,there was no sign of a structural phase transition in the spectra,demonstrating stability of the HPHT phase up to the highest pressure. 相似文献
14.
Influence of annealing treatment on as-grown Ib-type diamond crystal at a high temperature and high pressure 下载免费PDF全文
In this paper,we report on the influence of annealing treatment on as-grown Ib-type diamond crystal under high pressure and high temperature in a china-type cubic anvil high-pressure apparatus.Experiments are carried out at a pressure of 7.0 GPa and temperatures ranging from 1700 C to 1900 C for 1 h.Annealing treatment of the diamond crystal shows that the aggregation rate constant of nitrogen atoms in the as-grown Ib-type diamond crystal strongly depends on diamond morphology and annealing temperature.The aggregation rate constant of nitrogen remarkably increases with the increase of annealing temperature and its value in octahedral diamond is much higher than that in cubic diamond annealed at the same temperature.The colour of octahedral diamond crystal is obviously reduced from yellow to nearly colorless after annealing treatment for 1 h at 1900 C,which is induced by nitrogen aggregation in a diamond lattice.The extent of nitrogen aggregation in an annealed diamond could approach approximately 98% indicated from the infrared absorption spectra.The micro-Raman spectrum reveals that the annealing treatment can improve the crystalline quality of Ib-type diamond characterized by a half width at full maximum at first order Raman peak,and therefore the annealed diamond crystals exhibit nearly the same properties as the natural IaA-type diamond stones of high quality in the Raman measurements. 相似文献
15.
在压力为5.5–6.2 GPa, 温度为1280–1450 ℃的条件下, 利用温度梯度法详细考察了氮氢协同掺杂对100晶面生长宝石级金刚石的影响. 实验结果表明伴随合成腔体内氮、氢浓度的升高, 合成条件明显升高, 金刚石生长V形区间上移; 晶体的红外光谱中与氮相关的吸收峰急剧增强, 氮含量可达2000 ppm, 同时位于2850 cm-1和2920 cm-1对应于 sp3杂化 C–H 键的对称伸缩振动和反对称伸缩振动的红外特征峰逐渐增强, 表明晶体中既有高的氮含量, 同时又含有氢. 对晶体进行电镜扫描发现, 氮氢协同掺杂对晶体形貌影响明显, 出现拉长的{111}面, 且晶体表面上有三角形生长纹理. 拉曼测试表明, 晶体的峰位向高频偏移、半峰宽变大, 说明氮、氢杂质的进入对晶体内部产生了应力. 本文成功地以{100}晶面为生长面合成出高氮含氢宝石级金刚石单晶, 在探究氮氢共存环境下金刚石生长特性的同时, 也可为理解天然金刚石的形成机理提供帮助. 相似文献
16.
A. V. Tsvyashchenko L. N. Fomicheva M. V. Magnitskaya V. A. Sidorov A. V. Kuznetsov D. V. Eremenko V. N. Trofimov 《JETP Letters》1998,68(12):908-914
The compound CaCo2 with the C15 cubic Laves phase structure and an estimated density of 5.21 g/cm3 has been synthesized at 8.0 GPa pressure. Magnetization measurements showed that the compound CaCo2 is a ferromagnet with Curie temperature 528 K and magnetic moment per Co atom 1.75 μB at T=4.2 K. LMTO calculations of the electronic band structure showed that CaCo2 forms as a result of an s-d electronic transition of Ca and in the ground state it is a ferromagnet with a high magnetic moment per Co atom.
Pis'ma Zh. éksp. Teor. Fiz. 68, No. 12, 864–869 (25 December 1998) 相似文献
17.
High pressure pyrolysis of melamine has been attracting great interest recently, due to it being considered as a suitable precursor to realize the g-C3N4 and even superhard C3N4. In this work, we studied the detailed pyrolysis behavior of melamine at 22 GPa. Melamine was stable at 800 ℃, and decomposed to diamond in the form of powder at 1500-2000 ℃ under this pressure condition. At 2000 ℃, the pure cubic diamond powders with 0.1-0.5 μm grain size were obtained. The diamond particles exhibited euhedral forms and dispersed to each other, we proposed that these novel features were caused by the presence of liquid N2 and NH3 during diamond formation. The high pressure pyrolysis of melamine may provide a new means of producing micrometer-sized diamond powders. 相似文献
18.
Synthesis of large diamond crystals containing high-nitrogen concentration at high pressure and high temperature using Ni-based solvent by temperature gradient method 下载免费PDF全文
This paper reprots that with Ni-based catalyst/solvent and with a dopant of NaN 3,large green single crystal diamonds with perfect shape are successfully synthesized by temperature gradient method under high pressure and high temperature in a China-type cubic anvil high-pressure apparatus (SPD-6×1200),and the highest nitrogen concentration reaches approximately 1214-1257 ppm calculated by infrared absorption spectra.The synthesis conditions are about 5.5 GPa and 1240-1300 C.The growth behaviour of diamond with high-nitrogen concentration is investigated in detail.The results show that,with increasing the content of NaN 3 added in synthesis system,the width of synthesis temperature region for growth high-quality diamonds becomes narrower,and the morphology of diamond crystal is changed from cube-octahedral to octahedral at same temperature and pressure,the crystal growth rate is slowed down,nevertheless,the nitrogen concentration doped in synthetic diamond increases. 相似文献
19.
Dating of samples of cave dripstones collected from the Jaskinia Czarna (the Polish Tatra Mountains) and fossil bones was
carried out by means of electron paramagnetic resonance (EPR). By this method the age of the sample is found as the ratio
of the total dose (TD) to the annual dose rate (D
a). TD is established on the basis of EPR spectra, whileD
a is the sum of the internal dose rate, calculated on the basis of the concentration and activity of radioactive nuclides in
the sample, and the external dose rate measured at the site of the sample collection by a calibrated γ-radiation probe. Two
models of uranium accumulation were used: the model of linear accumulation and the model on the basis of the assumption of
a disturbed radiation equilibrium in the uranium series. The results were compared with the age determined by the uranium-thorium
method. Moreover, by the computer resolution enhancement method the dynamics of paramagnetic centers in calcite annealed in
nitrogen atmosphere was studied in the range of 283–873 K, and the results were compared with earlier results for calcite
annealed in the air. On the basis of the study of paramagnetic center dynamics in dripstone calcite it was established that
the radicals responsible for the EPR signals were CO2− in different symmetries of the crystalline field, CO33− in the axial symmetry, CO3− in the axial and isotropic symmetry and HCO32−. The results implied that samples to be subjected to EPR dating should be kept at room temperature. 相似文献
20.
S. V. Goryainov A. S. Krylov A. N. Vtyurin Y. Pan 《Journal of Raman spectroscopy : JRS》2015,46(1):177-181
Using an in situ method of Raman spectroscopy and resistance‐heated diamond anvil cell, the system datolite CaBSiO4(OH) – water has been investigated at simultaneously high pressure and temperature (up to Р ~5 GPa and Т ~250 °С). Two polymorphic transitions have been observed: (1) pressure‐induced phase transition or the feature in pressure dependence of Raman band wavenumbers at P = 2 GPа and constant T = 22 °С and (2) heating‐induced phase transition at T ~90 °С and P ~5 GPа. The number of Raman bands is retained at the first transition but changed at the second transition. The first transition is mainly distinguished by the changes in the slopes of pressure dependence of Raman peaks at 2 GPa. The second transition is characterized by several strong changes: the wavenumber jumps of major bands, the merging of strong doublets at 378 and 391 cm−1 (values for ambient conditions), the splitting of the intermediate‐intensity band at 292 cm−1, and the transformation of some low‐wavenumber bands at 160–190 cm−1. No spectral and visual signs of overhydration and amorphization have been observed. No noticeable dissolution of datolite in the water medium occurred at 5 GPa and 250 °С after 3 h, which corresponds to typical conditions of the ‘cold’ zones of slab subduction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献