Prospective evaluation of the use of various materials as matrices for active elements of lasers

Methods of prospective evaluation of the use of various materials as active elements for quantum generators for certain applications are considered. The way of evaluation for all kinds of dielectric crystal lasers with respect to optical quantum generators, applicable in technical designs is given. The influence of material properties on the prospective technical use is considered. The results are summarily analyzed.     

硼磷酸盐非线性光学晶体探索

我们实验室生长了ZBP、MZBP、BBP、SBP等硼磷酸盐晶体并研究了它们的基本特性.这些晶体机械性能良好、物化性质稳定、不潮解、倍频效应与KDP(KH2PO4)相当.     

利用化学键方法寻找新型光学晶体

利用化学键的观点定量地研究了一些具有各种晶体结构实用材料的介电性质。采用已建立的化学键方法，分析了这些晶体的介电性质与其组成化学键之间的关系。更进一步，基于晶体的化学键方法提出了一个组合方法用于定量确定具有相似晶体结构材料的介电性质。从目前的工作中可以推导出光学晶体非线性起源的结构信息，因此可以在一定程度上帮助人们开展非线性光学晶体工程的研究工作。     

Development of Methods for Growing LiIO3 and Ba(NO3)2 Crystals as Materials for Laser Frequency Converters

Crystallography Reports - New methods for growing LiIO3 and Ba(NO3)2 crystals have been developed. Barium nitrate crystals up to 12 × 12 × 100 mm3 in size and lithium iodate crystals up...     

激光晶体提拉生长模糊PID控制系统

本文设计了基于ARM Cortex-M3核、针对上称重法激光晶体的生长的控制方案硬件平台,运用模糊PID自适应控制算法对称重信号进行模糊处理确定晶体生长瞬间所需的温度场,根据生长模型在理论上进行了仿真,并实际运用到TDL-J50型激光单晶炉设备,实现了激光晶体的瞬时生长速率的精确而平稳的自动控制.     

硫/碳复合材料在锂硫电池正极中的应用

锂硫电池由于具有1675 mAh·g-1的高理论比容量和2600 Wh·kg-1的高理论能量密度,被看做是下一代最有前景的二次电池能源储存系统之一.但是,多硫化物的穿梭效应、活性物质导电性差以及充放电过程中的体积膨胀效应等问题阻碍了其进一步商业化.为了解决这些问题,不同的材料被引入和硫进行复合.在所有材料的选择中,碳材料由于具有高的表面积、优异的导电性、化学稳定性和低成本等优势在锂硫电池正极中得到了广泛应用.本文总结了几种不同的碳材料在硫/碳复合正极中的发展历程,讨论了碳材料的结构、孔径大小以及表面功能化对锂硫电池电化学性能的影响,并对其前景以及发展趋势作了预测.     

CoP纳米片制备及其电催化产氢性能的研究

高稳定性的催化剂对于规模化电催化产氢起着关键的作用.因此,采用简单的方法合成CoP纳米片,其表现出优越电催化活性和稳定性. CoP纳米片采用水热法和在氩气中磷化法制备的,纳米片的厚度为100～300 nm.CoP纳米片在0.5 M H2SO4的电解质中,表现出良好的电化学产氢性能,起始过电为～75 mV,塔菲尔斜率为～39. 67 mV/decade,当电流密度为10 mA· cm-2,过电压为～125 mV,经过1000次的循环后,保持良好的稳定性能.     

Yb:GdVO4晶体的光谱及激光损伤阈值

采用提拉法(Czochralski)生长出优质的GdVO4和Yb:GdVO4晶体,其中纯GdVO4晶体具有较高的透过率,可达81;.晶体在室温下的偏振吸收光谱与非偏振荧光光谱表明,Yb:GdVO4晶体是一种具有较大的吸收半峰宽和荧光半峰宽的激光晶体,分别为44～52nm和40～46nm;随着掺杂浓度增大,π偏振吸收系数呈现饱和趋势,且荧光峰的位置出现了红移.此外,还采用Nd:YAG激光器测试了晶体的激光损伤阈值,实验表明,随着Yb3+掺杂浓度从4.1at;增加到22.9at;,激光损伤阈值也相应地从19.9×109W/cm2逐渐减小到2.79×109W/cm2.     

On the Tactics of Ab Initio Search for the Shape of Protein Particles from Small-Angle X-Ray Scattering Data

Crystallography Reports - The determination of 3D particle shapes from the one-dimensional data on small-angle scattering from macromolecule solutions is ambiguous. In addition, due to the poor...     

Determination of the Optical Parameters of Uniaxial Crystals with Allowance for the Imperfection of the Spectrophotometric Complex Elements

The influence of the imperfection of a polarizer, an analyzer, and a photoelectron multiplier of a spectrophotometric complex on the intensity of light passed through a plane-parallel plate of a uniaxial transparent or absorbing crystal has been theoretically investigated. Expressions for calculating the birefringence and dichroism at different wavelengths are obtained and analyzed. It is established that the influence of the imperfection of optical elements is stronger for calculating the birefringence value, as compared with the calculation of dichroism.     

A Facile Route Towards the Synthesis of Nanocomposites for the Application as Solid Electrolytes via Grafting Polymer from TiO2 Nanoparticles

Poly(acrylic acid)/TiO₂ (PAA-g-TiO₂) nanocomposites were synthesized by the surface thiol-lactam initiated radical polymerization (TLIRP) technique. The synthetic strategy involved the modification of TiO₂by a one-step direct anchoring of thiol groups via reaction between the hydroxyl groups on the surface of TiO₂ and triethoxysilane groups of (3-mercapto)propyltrimethoxysilane (MPTMS). The modified TiO₂nanoparticles (NPs) were dispersed in acrylic acid monomers and subsequently polymerized by TLIRP to yield PAA-g-TiO₂nanocomposites. FT-IR spectra, XPS, EDS, UV-Vis spectroscopy and SEM images provided direct and clear evidence for the coordination of MPTMS and the presence of PAA on TiO₂ NPs. The immobilization of PAA onto TiO₂ NPs significantly improved their dispersibility in organic solvents. Additionally, laser diffraction spectroscopy of the TiO₂ NPs was examined in order to get the size distribution of nanocomposites.     

F-127作为模板剂合成微孔-介孔SAPO-11分子筛及其在长链烷烃异构化中的应用

在常规水热法合成SAPO-11的基础上,添加适量F-127作为软模板构造介孔结构,成功合成出了SAPO-11分子筛微介复合体.考察了F-127添加量对分子筛内部的孔道结构的影响,并通过XRD、N2吸附-脱附曲线、SEM和Py-FTIR等途径对催化剂进行表征.以正十二烷为原料,对负载Pt金属的SAPO-11分子筛进行临氢异构化反应性能评价.结果表明:添加F-127的分子筛内部出现了明显的介孔结构,并且随着F-127添加量的增加,分子筛的介孔孔容呈先增大后减小的趋势;异构化反应结果表明催化剂活性位的数量与分子筛介孔孔容有关;随着温度的升高,异构烷烃转化率升高,异构烃收率下降.催化剂的异构化转化率伴随着F-127的添加量的增加而降低,F-127添加量在一定范围内的增加可使异构烃收率得到提高.在F-127添加量为10;时,异构烃收率达到最高为57.62;.     

Application of mercury porosimetry to the study of xerogels used as stone consolidants

Alkoxysilanes, low-viscosity monomers that polymerize into the porous network of stone by a sol-gel process, are widely used in the restoration of stone buildings. We have used the mercury porosimetry technique to characterize changes in microstructure of three granites following their consolidation with two popular commercial products (Wacker OH and Tegovakon V). The suitability of this technique is questioned because a surprising increase of stone porosity is observed. In order to investigate the feasibility of porosimetry, we analyze the behavior of xerogels prepared from the two commercial products, under mercury pressure. Gels are basically compacted and not intruded by mercury. Thus, the increase of stone porosity after consolidation can actually be associated with gel shrinkage. Mercury porosimetry, therefore, has been found unsuitable for characterizing the microstructure of consolidated rocks. However, it can be employed usefully to evaluate shrinkage of gels under mercury pressure, which permits the behavior of a consolidant during the process of drying in stone to be predicted. It is a key factor because many problems of consolidants are related to their drying process within the stone. Gels under study exhibit a high rigidity and an elastic behavior, as consequence of their microporous structure. Finally, the reduction in the porous volume of gels after the porosimetry test demonstrates that the shrinkage mechanism is based on pore collapse.     

Erratum to: On the Tactics of Ab Initio Search for the Shape of Protein Particles from Small-Angle X-Ray Scattering Data

Crystallography Reports - An Erratum to this paper has been published: https://doi.org/10.1134/S1063774521340101     

Search for instantaneous radiation near the instant of break momentum of various fissioning nuclear systems at low excitation energies

The main results of studying the properties of “instantaneous” neutrons and γ photons during the fission of ^{233, 235}U(n _th, f) and ²³⁹Pu(n _th, f) nuclei and spontaneous fission of ²⁵²Cf, which were performed on the WWR-M reactor at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences, are presented. Along with obtaining the main characteristics of the instantaneous radiation from fission fragments, these studies were also aimed at gaining deeper insight into such exotic processes as the emission of break neutrons and γ photons from a fissioning nucleus near the break point. These investigations were performed on different experimental setups using different analytical methods. This approach allowed us not only to find but also to reduce to minimum possible systematic effects. The yields of break neutrons were found to be about (5–7) × 10⁻² of the total number of neutrons per ^{233, 235}U(n, f) fission event and approximately twice as much for ²³⁹Pu(n, f) and ²⁵²Cf. The coefficient of T-odd asymmetry for γ photons is in agreement with the estimate obtained on the assumption that the observed effect is mainly related to the γ photons emitted by excited fragments with highly oriented angular momenta. This fact gave grounds to conclude that the desired break γ photons cannot be reliably selected (within the obtained experimental accuracy) against the much larger background of γ photons from fission fragments.     

介孔Co3S4纳米棒的制备及电催化产氧性能的研究

以六水合硝酸钴(Co(NO3)2· 6H2O)为钴源,硫脲(CS(NH2)2)为硫源,采用溶剂热法和低温固相硫化的方法制备出了介孔Co3S4纳米棒.采用X射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)等手段对于介孔Co3S4纳米棒进行表征,同时对介孔Co3S4纳米棒进行了电催化产氧性能测试.结果表明:介孔Co3S4纳米棒的起始过电位为0.37 V,塔菲尔斜率为76.95 mV/dec,具有高的电催化产氧性能.     

The silicon impurity as a possible growth-regime indicator for LiNbO3 crystals

The influence of Si concentration and temperature regimes on the visually observable properties of LiNbO₃ single crystals grown by Czochralski method was studied. Si concentration measurements were carried out and minima in the radial and axial distribution curves have been established. An upper estimate is given for the equilibrium distribution coefficient of Si in LiNbO₃. A direct correlation has been found between the degree of opacity and the Si concentration. The variation of the Grashof number during growth and a correlated modification of the structure of the concentration layer width, implying a position dependent fulfilment of the Hurle-Bardsley criterium for constitutional supercooling, accounts reasonably well with the visually observable properties of the opaque regions appearing in the course of crystal growth. The use of Si as an overall indicator for the characterization of growth regimes is discussed.     

The IR Television Scanning Technique as Temperature Field Control for Growing Silicon Crystals

Outgoing from the idea that the temperature field of the growing crystal is the most general as well as characteristic representation of all technological parameters and equipment conditions the ir-television scanning technique was as a method for recording and controlling of temperature distributions at the surface of growing crystals and melts. Using a number of electronic treshold value switches, some video signal amplitude levels can be made visible at the monitor, giving an overlook on the isotherm distribution at the crystal surface. Records of such observations are helpful for reproduction and optimization of crystal growth technologies. For Silicon crystal growth, the process control by ir-television scanning technique is a fast, convenient, and nondisturbing one giving important informations.     

Development of Software for Determining the Parameters of Pores and Segregations of Alloying Elements in Austenitic Steels after Ion Irradiation

Crystallography Reports - SwellingProfile and ElementProfile software packages were developed to construct swelling profiles when processing cross-cut images obtained using scanning transmission...