过饱和度对KDP晶体生长与光学性能的影响研究

在不同过饱和度的溶液中生长了KDP晶体,对生长晶体的透过率,光散射和激光损伤阈值进行了表征.研究了不同过饱和度对KDP晶体生长及光学性能的影响.实验表明:KDP晶体可以在高过饱和度(σ＞3;)溶液中实现快速生长,生长速度可大于10 mm/d;但随着溶液过饱和度的增加,KDP晶体生长溶液的稳定性降低,晶体容易出现包藏、开裂和添晶等缺陷,晶体的光学性能也随之降低.     

KDP晶体的点状籽晶法生长及其缺陷研究

研究了溶液Ph值对KDP晶体生长形态的影响,进行了晶体生长实验和参数对比.以提高溶液Ph值为主要手段在低过饱和度下进行KDP晶体点状生长.对点状法生长的晶体进行了缺陷分析,测定了晶体不同区域的金属离子含量并进行了对比分析.实验表明溶液Ph值对晶体各向的相对生长速度有显著的影响.在Ph=5.0、低过饱和度(σ＜0.02)条件下生长出50×50×50mm3的晶体.     

溶液降温法快速生长KDP晶体的新装置

利用溶液降温法分别在锥形底生长装置和传统晶体生长装置中进行了KDP晶体点状籽晶法快速生长实验,对KDP晶体的生长条件进行了对比,分析了不同生长装置对KDP溶液稳定性的影响,利用扫描电镜观察了KDP晶体中的包裹体,测定了晶体的透过率,对比分析了锥形瓶快速生长装置的优越性.     

KDP晶体生长过程中溶液稳定性的研究

在KDP晶体生长过程中,溶液的稳定性对KDP晶体的光学质量影响较大.溶液的稳定性是多种因素共同作用的结果.本文主要研究了过饱和KDP溶液中晶胚的分布情况、降温过程中晶体生长驱动力与降温速度之间的关系,并分析了KDP晶体实际生长过程中影响溶液稳定性的主要因素.我们认为,通过改善KDP晶体生长过程中溶液的稳定性,并与其它措施和技术相结合,是提高KDP晶体光学质量的有效途径.     

Na+对KDP晶体生长的影响

本文利用传统的降温法和"点籽晶"快速生长法在不同Na+掺杂浓度的溶液中生长KDP晶体,定量研究了Na+对KDP晶体生长的影响.实验发现:Na+的存在降低了溶液的稳定性,致使KDP晶体柱面容易扩展.Na+的存在对KDP晶体的光学性能基本没有影响.     

点状籽晶法生长KDP晶体中散射颗粒分布

在不同的溶液pH值条件下进行了点状籽晶法慢速和快速生长KDP晶体实验,发展了观察晶体中散射颗粒分布的激光层析技术,通过图像处理得到了KDP晶体内部(100)面完整的散射颗粒分部图,对不同生长速度、不同pH值条件下点状籽晶法生长的KDP晶体的散射颗粒分部做了对比.利用表面光学投影技术观察了晶体表面宏观形貌,并由此分析了不同生长条件下生长机制对散射颗粒分布的影响.测定了散射颗粒密度不同部位的晶体透过率.     

Fe3+对KDP晶体生长影响的研究

金属离子对KDP晶体的影响是多方面的.本文采用不同的过饱和度,在不同的Fe3+掺杂浓度的生长溶液中生长KDP晶体,定量地研究了Fe3+对KDP晶体生长的影响.实验发现,无论是在高过饱和度还是在低过饱和度下生长KDP晶体,在一定的浓度范围内,Fe3+的掺入既可以增加生长溶液的稳定性,又可以有效抑制晶体柱面的扩展,而且晶体基本不楔化,同时,对晶体光学性能的影响也不大.     

传统法KH2PO4(KDP)晶体生长温场和速度场的数值模拟研究

在不同转速下用传统法生长了KDP晶体,并根据生长槽的实际情况,建立了三维数学模型.利用有限容积法,对晶体生长槽内的速度场和温度场进行了数值模拟,分析了不同晶体转速和晶体生长对速度场和温度场的影响规律.结果表明,随着晶体转速的增大,溶液流速越来越大,晶体生长更快,杂晶减少;较高转速(55 r/min和77r/min)较于较低转速(9.0～40 r/min)更有利于晶体生长.     

非线性光学晶体丁二酸锌的生长研究

本文报道了一种金属有机配位聚合物非线性光学晶体--丁二酸锌Zn(C4H4O4)大尺寸单晶生长.通过恒温蒸发法生长出尺寸为7 mm×8 mm×2 mm 的单晶.测定了它在水中溶解度-温度曲线.通过水溶液红外光谱阐明了不同pH值时溶液中各种粒子的浓度分布.借助红外光谱研究了pH值、温度等对晶体生长的影响.Kurtz粉末倍频效应测定证实了丁二酸锌具有非线性光学性能,其倍频强度是KDP的6.5倍.     

二价阳离子掺入KDP晶体能力的研究

本文旨在寻找影响杂质阳离子进入KDP晶体能力的因素,我们使用分析纯的KH2PO4和超纯水(电阻率≥18.2MΩ·cm)为原料,分别加入BaCl2·2H2O,CuCl2·2H2O和MgCl2·6H2O,通过降温方式快速生长出KDP晶体.结果表明,cu2+及Mg2+在晶体中的含量基本保持不变,不随其在生长溶液中量的增大而增大,cu2+在晶体中的含量大于Mg2+在晶体中的含量;不同的是,Ba2+在晶体中的含量随着其在生长溶液中量增大而增大.从实验结果我们推断出离子半径和离子水合热是影响二价杂质阳离子在水溶液晶体生长过程中进入KDP晶体能力的重要因素.     

A review of measurement of thermophysical properties of silicon melt

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.     

电子显微分析在表征纳米晶体化学组分中的应用

纳米材料的化学组分及含量影响其光、电、声、热、磁等物理性能,电子显微分析是表征纳米晶体化学组分的重要方法之一.本文综述了X-射线能谱(EDS)、X-射线波谱(WDS)、电子能量损失谱(EELS)和选区电子衍射(SAED)等现代电子显微分析技术在表征纳米晶体化学组分、形貌、尺寸和结构等方面的应用及其研究进展,并比较了这些分析方法存在的差异,提出了其应用中存在的不足及今后的研发方向.     

Mesomorphism Dependence on the Position of Substitution of a Pair of Esters

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.     

原位氮化法制备TiN纳米粉体

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.     

On the influence of structural features of DNA on the possibility of metabolic transfer of electrons

Abstract

A 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.     

Effect of alumina on enthalpy of mixing of mixed alkali silicate glasses

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.     

PEG聚合度对氧化铝造粒粉的性能影响

为制备适用于干压成型的氧化铝造粒粉,研究了PEG聚合度对氧化铝造粒粉微观形貌、流动性和松装密度的影响.结果表明PEG的聚合度对氧化铝浆料粘度影响显著,PEG2000-6000是较为理想的粘结剂选择,造粒粉的流动性与环境温度及湿度相关.采用正交实验设计,以造粒粉的流动性和松装密度为评价指标,对PEG聚合度、粘结剂添加量和固含量进行了优选,其影响顺序为PEG聚合度＞固含量＞粘结剂添加量.以优选参数PEG6000、添加量为4wt;、固含量为80wt;,制备了性能优良的氧化铝喷雾造粒粉.     

近化学计量比铌酸锂晶体组分测定与缺陷观察

采用助熔剂提拉法生长得到近化学计量比LiNbO3晶体.用多种方法测定了晶体组分,结果表明生长得到的晶体中[Li2O]含量为49.80;摩尔分数;对晶体缺陷的研究表明晶体质量有待提高,并分析了晶体中出现包裹物的原因.     

Statistical characterization of the pore space of random systems of hard spheres

An improved statistical characterization of disordered structures such as metallic glasses, random porous media, or granular matter is presented. Suitable structure models follow the idea of dense random packed spheres, where the spheres represent atoms and particles in the case of metallic glasses and porous or granular matter, respectively. The geometry of the empty space between the atoms or particles is described by means of the already otherwise successful concept of so-called contact distributions. Their exact mathematical forms are unknown for hard sphere systems. Knowledge on these is obtained by means of Monte Carlo simulations of the structure models. The numerical results are approximated by simple and general mathematical expressions, with parameters that can be easily determined. These may serve as additional tools for the structural characterization of disordered matter, including systems of partly penetrable spheres.     

前驱物合成条件对锰锌铁氧体结构和性能的影响

采用共沉淀-热处理工艺合成了尖晶石型锰锌铁氧体粉末,利用正交试验优化了制备工艺。利用X射线衍射仪(XRD)扫描电子显微镜(SEM)和振动样品磁强计(VSM)对粉体的显微结构和静磁性能进行了研究。结果表明:热处理温度为1350℃、保温时间为3.5 h、进料比为1.5时,若前驱物的pH值为6,制备的样品的主晶相为锰锌铁氧体;若前驱物的pH值为7 9,则形成单相尖晶石型锰锌铁氧体,样品的饱和磁化强度先增大后减小,矫顽力逐渐增大。pH值为7时,配方为Fe∶Mn∶Zn=68.4816∶17.1368∶14.381,进料比为1.5,滴加时间为40 min,反应温度为50℃,不加表面活性剂时得到的样品具有较高的饱和磁化强度。