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以浓度分布差小和退火后光学均匀性好为目的,通过改造温场,分阶段调整生长界面、搅拌速度、提拉速度、温度、时间等工艺参数,改善了Nd:YVO4激光晶体的光学质量和光学均匀性. 相似文献
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首先测量了KDP溶液的亚稳区,并据此开展“点籽晶”KDP晶体快速生长实验.在实验中采用两种晶体运动方法-“二维平动法”和“旋转法”来生长晶体,分别得到尺寸为55 mm×55 mm×48 mm和60 mm×60 mm×45 mm的晶体.将两种运动方式生长的晶体通过透过光谱,锥光干涉图以及化学腐蚀方式进行质量对比.结果表明,两种方式生长的晶体透过光谱没有太大区别,都具有较高的透过率,但“二维平动法”生长的晶体具有较好光学均匀性,位错密度明显降低.说明“二维平动法”生长晶体的方式能够减少晶体内部缺陷,提高晶体质量. 相似文献
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采用Perkin Elmer公司的Diamond TMA热机械分析仪对KDP/DKDP晶体在25~100℃范围内的平均线性热膨胀系数进行了研究.得到KDP/DKDP晶体x切向、z切向、Ⅰ类切向和Ⅱ类切向的平均线性热膨胀系数,分别为:KDP(2.454×10-5/℃、4.168×10-5/℃、3.465×10-5/℃和2.884×10-5/℃),DKDP(2.602×10-5/℃、4.284×10-5/℃、3.568×10-5/℃和3.052×10-5/℃).另外,实验结果表明大尺寸KDP/DKDP晶体不同部位热膨胀系数存在不均匀性. 相似文献
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硒铟锂(LiInSe2,LISe)晶体在长波红外激光领域有重要应用价值.目前高质量、大尺寸LISe晶体的稳定生长仍然面临挑战,通过气氛退火后处理工艺能够有效提高晶体光学质量.本文采用定向籽晶垂直布里奇曼法,通过精确控制籽晶熔接,实现大尺寸(φ40 mm×60 mm)LISe晶体的批量稳定制备,为目前国际上报道的最大尺寸LISe晶体.另外,系统探索了LISe晶体的退火工艺,研究表明在740℃、LISe本征气氛下退火150 h,可以明显提高LISe晶体器件光学质量. 相似文献
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为了明确Al3+在KDP晶体生长过程中对光学性质和力学性质的具体影响,采用第一性原理计算程序包VASP软件计算并分析了Al取代K对KDP晶体的晶体结构、电子能态密度和光学性质,并同理想KDP晶体进行对比研究.结果表明,KDP晶体中Al取代K的缺陷形成能为0.974 eV,并且Al替位K点缺陷引起的晶格畸变非常微弱,缺陷比较容易形成. Al取代K后晶体能带中价带顶附近的态密度发生了变化,并且带隙中存在缺陷能级,取代后KDP晶体的带隙宽度减小为4.37 eV,缺陷增加了KDP晶体对可见到紫外波段的光子吸收,影响KDP晶体光学质量及其激光损伤性能.计算力学性质发现,Al替位掺杂KDP晶体比理想KDP晶体的杨氏模量增加了,这会减弱晶体抗激光损伤能力. 相似文献
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Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi3 existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species. 相似文献
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P.J. Lezzi 《Journal of Non》2011,357(10):2086-2092
The enthalpy of mixing of mixed alkali (Na2O and K2O) silicate glasses containing various concentrations of alumina was determined using an ion-exchange equilibrium method. For glasses with a constant alkali concentration, the enthalpy of mixing was found to become less negative with alumina addition. Consistent with our previous results on the enthalpy of mixing of alumina-free mixed alkali silicate glasses, the magnitude of enthalpy of mixing exhibited a good correlation with the molar volume mismatch of the corresponding two single alkali glasses as well as with the extent of conductivity mixed alkali effect, e.g. excess activation energy of conductivity, ΔE. The reduction of the magnitude of the enthalpy of mixing with alumina addition can be attributed to the reduction of non-bridging oxygen and ionic field strength. Combining the present results with results obtained earlier, the magnitude of the enthalpy of mixing for all mixed alkali (Na2O and K2O) silicate glasses with and without alumina was expressed by a simple function of a modified Tobolsky parameter, which takes into account the alkali concentration and the difference in cation-to-effective anion distances. The enthalpy of mixing data of the mixed alkali glasses was then compared with reported experimental data on the conductivity of mixed alkali aluminosilicate glasses. What appears to be conflicting experimental data can be understood in terms of the magnitude of the enthalpy of mixing and we can conclude that the mixed alkali effect is closely correlated with the negative enthalpy of mixing. 相似文献
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A novel homologous series of ethylene derivatives of thermotropic liquid crystals has been synthesized. The methoxy to octyloxy derivatives are nematogenic, the decyloxy to tetradecyloxy derivatives are smectogenic, in addition to nematogenic, and the hexadecyloxy homologue is smectogenic only. All the members of the series are enantiotropically mesogenic. Thermotropic behavior was determined by an optical polarizing microscope equipped with a heating stage and Differential Scanning Calorimetry (DSC) study. Analytical and spectral data confirm the molecular structures of homologues (infrared, nuclear magnetic resonance, mass spectra, X-ray, and DSC data). Textures of the nematic phase are threaded or Schlieren and that of smectic phase are focal conic fan-shaped of smectic A or C. Transition curves of the phase diagram behave in a normal manner except one or two deviations from the normal trend. The mesophase range (Sm+N) varies from 3°C to 44°C. The average thermal stability for smectic is 93°C and that for nematic 117.4°C. The LC behavior of the novel series is compared with a structurally similar known series. 相似文献
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原位氮化法制备TiN纳米粉体 总被引:3,自引:0,他引:3
用溶胶凝胶法合成的纳米TiO2粉体作为原料,将该粉体在氨气中进行原位氮化制备了TiN纳米粉体.用XRD,TEM,化学分析等手段对合成的TiN纳米粉体的物相组成、形貌、成分进行了分析.实验分析表明:在1000℃和1100℃下分别氮化5h,可以制备粒径大约为40nm和80nm的TiN粉体,其TiN的含量分别为95.40;和98.37;;而在1000℃条件下氮化时间减少到2h时,TiN的含量仅为58.36;.氮化温度和氮化时间是合成纳米TiN的重要因素,提高合成温度和延长氮化时间均可形成纯度较高的TiN纳米粉体,但延长氮化时间更有利于获得粒径小的氮化钛粉体. 相似文献
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On the influence of structural features of DNA on the possibility of metabolic transfer of electrons
A. D. Suprun 《Molecular Crystals and Liquid Crystals》2020,701(1):28-39
AbstractA fragment of a DNA molecule is considered as one of the channels of metabolic electron transfer. The heterogeneity of the complementary chains is effectively taken into account. This made it possible to find the speed of the electron injected into the DNA conduction band and the current density that it creates. Estimates of electron mobility in nucleic acid chains are made. They were an order of magnitude smaller than that of typical semiconductors. For the specific conductivity of nucleic acid chains, estimates provide a conductivity of one to two orders of magnitude lower than in graphite. 相似文献
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O. Dryuchko D. Storozhenko A. Vigdorchik N. Bunyakina I. Ivanytska K. Kytaihora 《Molecular Crystals and Liquid Crystals》2018,672(1):199-214
AbstractThe complex study provides a reliable idea of ??the trends in the joint behavior of structural components in the water-salt systems of nitrate precursors of REE, alkaline, alkaline earth metals in the preparatory stages of the processes of forming multicomponent oxide polyfunctional materials on their basis with thermal activation. Stages of such transformations are revealed; The regularities of complex and phase formation in systems and factors influencing them are determined; A number of physicochemical properties of the intermediate phases formed - coordination lanthanides nitrates: their composition, types of compounds, atomic-crystalline structure, regularities of transformations during heat treatment were studied. 相似文献
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K. Sethuraman R. Ramesh Babu N. Vijayan R. Gopalakrishnan P. Ramasamy 《Crystal Research and Technology》2006,41(8):807-811
A new organic single crystal of semicarbazone of cyclohexanone (SCCH) has been synthesized and grown as a bulk single crystal by low temperature solution growth technique for the first time in the literature. The grown crystal has been confirmed by X‐ray diffraction and proton nuclear magnetic resonance spectral analyses and also characterized by FT‐ir and FT‐Raman studies. Thermal properties of the grown crystals were studied by thermogravimetric and differential thermal analyses. Optical transmittance was studied by ultraviolet‐visible spectrum and the second harmonic generation property was tested by using Q switched Nd: YAG laser as a source. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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M. Thamilselvan K. Premnazeer D. Mangalaraj Sa. K. Narayandass Junsin Yi 《Crystal Research and Technology》2004,39(2):137-142
A systematic investigation on the effect of substrate temperature on the structure, optical absorption and density of states of vacuum evaporated gallium monoselenide (GaSe) thin films is reported. The X‐ray diffraction analysis shows an occurrence of amorphous to polycrystalline transformation in the films deposited at higher‐temperature substrates (573K). The compositional analysis is made with Auger Electron Spectroscopy (AES). The thickness of the film (175nm) is measured by a multiple beam interferometery. Optical characteristics of the GaSe sample have been analyzed using spectrophotometer in the photon energy range of 1.0 ‐ 4 eV. The absorption mechanism has been recognized and the allowed indirect as well as forbidden direct transitions have been found. As‐deposited films show two indirect and allowed transitions due to spin‐orbit splitting of the valence band, as reported here for the first time. Low field conduction have enabled us to determine the density of states in amorphous and poly‐GaSe films. The amorphous and polycrystalline GaSe thin films have localized states density values of N (EF) = 1.686 × 1017 cm‐3 eV‐1 and 1.257 × 1015 cm‐3 eV‐1 respectively. The experimental results are interpreted in terms of variations in the density of localized states due to progressive decrease of the unsaturated bonds during deposition. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献