蓝宝石火花塞

在如何提高火花塞的工作质量方面有多种方法,但是其中最重要的一个问题还没有得到解决,那就是火花塞工作的热学模型问题。理想的火花塞应该能在点火的瞬间被立刻加热,并且在接下来的电脉冲过程中迅速冷却,由此在热量的存储与散发之间取得平衡,以避免自点火。本文力图展示一种具有自动调节源于点火区域热流能力的火花塞,其技术的关键是顶部绝缘体材料,它是由蓝宝石单晶制作,而非传统的氧化铝陶瓷。     

抗"灰迹"KTP晶体光学性能研究

用改进的熔盐顶部籽晶法生长了KTiOPO4(KTP)晶体并对该晶体进行了抗"灰迹"性能测试.测试表明,在功率密度为120kW/cm2的1064nm激光和10kW/cm2的532nm激光共同照射1000s后, 晶体在633nm处的吸收依然维持在1.05×10-4/cm左右,表明该晶体比普通KTP晶体具有更高的抗 "灰迹"性能.透过率测试表明,用本方法生长的KTP晶体在波长短于500nm的区域比普通KTP晶体有更高的透过率.通过实验测定,得出该晶体在室温下1064nm倍频Ⅱ类相位匹配角θ=90°时φ=24.40°.     

KDP晶体“二维平动法”生长及其品质分析

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.     

直拉单晶硅片“黑心”现象性质分析

对一种黑心片样品进行了分析.在确认黑心区为低少子寿命区的基础上,发现其电阻率明显偏高;发现黑心区经Secco刻蚀后,表面密布重叠圆形蚀坑,但与普通位错蚀坑有明显特征性区别;从其密度、形状与出现条件来看,它与电子半导体业中普遍报告的氧化堆垛层错(OSF)也不一致;进一步发现黑心区经Sirtle刻蚀后,表面呈现典型的大小明显不同的两种漩涡缺陷蚀坑,其密度明显低于上述Secco蚀坑.根据所得结果推测:黑心区主要密布一种性质上与普通位错相近,而所造成晶格畸变特征与范围不同于普通位错的晶格缺陷,它不属于已知的OSF微缺陷,而可能是一种由结晶生长过程中过饱和氧沉淀诱发形成的位错环;此外,黑心区还含有少量漩涡缺陷.     

Specific stereochemical features of metallochelate complexes with tridentate <Emphasis Type="Italic">N,N,N</Emphasis>(<Emphasis Type="Italic">N,N</Emphasis>,O)-donating ligands

Earlier X-ray diffraction studies of a series of 12 adducts (I–XII) between metallochelate complexes [M = Co(II), Ni(II), and Cu(II)] with tridentate N,N,N(N,N,O)-donating Schiff bases (L) and monodentate or bidentate ligands (L′) revealed a similarity in the stereochemistry of these compounds. The coordination polyhedron of metal atoms in compounds I–XII is a tetragonal pyramid (bipyramid) with two vertices occupied competitively. The L ligand occupies three coordination sites in the base of the pyramid. The L′ ligand approaches the metal atom, as a rule, in a direction perpendicular to the basal plane. The fourth site in the base of the pyramid and the apical vertex are occupied competitively. Different patterns of occupation of these positions are observed: they include the donor atoms of both the L and L′ ligands.     

共蒸发三步法制备CIGS薄膜的相变过程

本文采用共蒸发三步法沉积Cu(In,Ga) Se2 (CIGS)薄膜,其中关于Cu化合物的相转变过程是制约吸收层质量的关键.本文详细研究了三步法工艺中吸收层由贫Cu薄膜向富Cu薄膜转变的相变过程,通过X射线衍射仪(XRD)、X射线荧光光谱仪(XRF)及扫描电镜(SEM)结合的方法总结出三步法工艺的相变过程.     

Crystal Structure of 2, 8, 14, 20-<Emphasis Type="Italic">tert</Emphasis>-Butylpyrogallol[4]arene

Abstract  The aromatic derivative 2, 8, 14, 20-tert-butylpyrogallol[4]arene was synthesized by the acid catalyzed condensation of pivalaldehyde and pyrogallol in refluxing aqueous ethanol. Single crystal X-ray analysis revealed that the molecule crystallizes in the monoclinic crystal system; space group: P2₁/c. Unit cell dimensions: a = 11.1175(7) ?, α = 90°, b = 23.4525(15) ?, β = 101.6720(10)°, c = 21.9595(14) ?, γ = 90°, D_calc = 1.205 Mg/m³ g/m³ for Z = 4. In the solid state, the macrocycle is found to adopt a crown structure that is unique for the rcct conformation. Graphical abstract   Crystal Structure of 2, 8, 14, 20- tert -Butylpyrogallol[4]arene Eric E. Dueno, Allen D. Hunter, Matthias Zeller, Thomas A. Ray, Ralph N. Salvatore, Cesar H. Zambrano Acid catalyzed condensation of pyrogallol and pivalaldehyde in refluxing aqueous ethanol afforded a pyrogallol[4]arene derivative in good yield. Single crystal X-ray diffraction analysis revealed that a new calyx-like structure was formed under the reaction conditions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Growth, morphological, mechanical and dielectric studies of semi organic NLO single crystal: l-argininium perchlorate

Optically good quality single crystal of l-argininium perchlorate (abbreviated as LARPCL), a promising analog of LAP was successfully grown by slow solvent evaporation technique at room temperature. The unit cell parameters and the morphology of LARPCL single crystals were determined by single crystal XRD. The Vickers microhardness measurements were carried out on the grown crystals to estimate the mechanical properties. The dielectric constant and dielectric loss of the crystal were measured as a function of frequency and temperature, and the results are discussed.     

Synthesis, growth and characterization of nonlinear optical crystal: l-tyrosine hydrobromide

l-tyrosine hydrobromide (l-THB) a semi organic nonlinear optical material with molecular formula C₉H₁₂NO₃Br has been synthesized at ambient temperature. Spectral, thermal and optical techniques have been employed to characterize the new material. The solubility of l-THB at varying temperatures was determined in different concentrations of hydrobromic acid. Bulk single crystals of size 15×7×4 mm³ of l-THB were grown by slow evaporation method at constant temperature. Powder X-ray diffraction pattern of the grown l-THB has been indexed. Functional groups present in the sample were identified by FTIR spectral analysis. Chemical composition of the synthesized material was confirmed by carrying out CHN analysis. Thermal stability of l-THB was determined from TGA/DTA and DSC response curves. Mechanical hardness of the grown crystal l-THB was determined and Vickers hardness number was calculated. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for optical second harmonic generation. The optical transparency range and the lower cut-off of UV transmission were identified from the recorded UV-vis spectrum of l-THB. The optical energy gap of l-THB is 3 eV.     

Crystal chemistry of silicates with three-layer <Emphasis Type="Italic">TOT</Emphasis> and <Emphasis Type="Italic">HOH</Emphasis> modules of layered,chainlike, and mixed types

In view of new data on the chemical composition and structure of a series of natural layered silicates containing three-layer blocks and their corresponding microporous minerals with related fragments, their structural features; the structural conditionality of their properties; their transformation in the presence of isomorphism, decationation, and hydration; and the problems related to typomorphism and some other questions urgent for modern mineralogy have been considered. The structures are described in terms of threelayer modules of different forms and dimensions that are present in these structures. The composition and design of the general structural base of related series—three-layer modules forming layered or linear radicals—are also discussed. The minerals of these families differ in chemical composition, symmetry, and unit-cell parameters, as well as in the topological features associated with the type of condensation of the Si tetrahedra into layers or ribbons and the degree of condensation of M polyhedra in the central part of blocks: from layers and octahedral ribbons of different widths to chains and isolated polyhedra.     

Nanoclusters based on pentagondodecahedra with shells in the form of <Emphasis Type="Italic">D</Emphasis>32, <Emphasis Type="Italic">D</Emphasis>42, and <Emphasis Type="Italic">D</Emphasis>50 deltahedra in crystal structures of intermetallic compounds

The TOPOS software package has been used to form a database of intermetallic compounds containing pentagondodecahedral d clusters (528 crystal structures of intermetallic compounds, 111 topological types, and 47 space symmetry groups). On the whole, 606 atomic d configurations have been selected which are described by 14 point symmetry groups. Examples of nanoclusters are presented which are precursors of the crystal structures of intermetallic compounds with the outer shell in the form of deltahedra D, which are formed above dodecahedra. These nanoclusters are identified in the automatic mode of structural data processing: D32 (K₈In₆Ge₄₀, Cs₃₀Na₃Sn₁₆₂), D ₄₂ (Ru₃Be₁₇, Y₃Cd₁₈, Ca₃(Cd₁₇Al)), and D ₅₀ (Yb₃Zn₁₈, Ce₃(Au₁₄Sn₃), Pr₃Cd₁₈, Eu₄Cd₂₅), where 32, 42, and 50 are the numbers of atoms in the shell. Similar deltahedra were found previously in icosahedral nanoclusters (precursors of intermetallic compounds). Structures with the dodecahedral nanocluster precursors containing D42 and D50 deltahedra are approximants of MCd_5.7 (M = Yb or Ca) quasicrystals and belong to the family of MCd₆ (M = Ce, Pr, Nd, Sm, Eu, Gd, Dy, Yb, Y, or Ca).     

Purification,isolation, crystallization,and preliminary X-ray diffraction study of the BTB domain of the centrosomal protein 190 from <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The spatial organization of the genome is controlled by a special class of architectural proteins, including proteins containing BTB domains that are able to dimerize or multimerize. The centrosomal protein 190 is one of such architectural proteins. The purification, crystallization, and preliminary X-ray diffraction study of the BTB domain of the centrosomal protein 190 are reported. The crystallization conditions were found by the vapor-diffusion technique. The crystals diffracted to 1.5 Å resolution and belonged to sp. gr. P322₁. The structure was solved by the molecular replacement method. The structure refinement is currently underway.     

X-ray structures of uridine phosphorylase from <Emphasis Type="Italic">Vibrio cholerae</Emphasis> in complexes with uridine,thymidine, uracil,thymine, and phosphate anion: Substrate specificity of bacterial uridine phosphorylases

In many types of human tumor cells and infectious agents, the demand for pyrimidine nitrogen bases increases during the development of the disease, thus increasing the role of the enzyme uridine phosphorylase in metabolic processes. The rational use of uridine phosphorylase and its ligands in pharmaceutical and biotechnology industries requires knowledge of the structural basis for the substrate specificity of the target enzyme. This paper summarizes the results of the systematic study of the three-dimensional structure of uridine phosphorylase from the pathogenic bacterium Vibrio cholerae in complexes with substrates of enzymatic reactions—uridine, phosphate anion, thymidine, uracil, and thymine. These data, supplemented with the results of molecular modeling, were used to consider in detail the structural basis for the substrate specificity of uridine phosphorylases. It was shown for the first time that the formation of a hydrogen-bond network between the 2′-hydroxy group of uridine and atoms of the active-site residues of uridine phosphorylase leads to conformational changes of the ribose moiety of uridine, resulting in an increase in the reactivity of uridine compared to thymidine. Since the binding of thymidine to residues of uridine phosphorylase causes a smaller local strain of the β-N1-glycosidic bond in this the substrate compared to the uridine molecule, the β-N1-glycosidic bond in thymidine is more stable and less reactive than that in uridine. It was shown for the first time that the phosphate anion, which is the second substrate bound at the active site, interacts simultaneously with the residues of the β5-strand and the β1-strand through hydrogen bonding, thus securing the gate loop in a conformation     

Synthesis,Characterization, Structure,Ab Initio and DFT Calculations of 2-Amino-<Emphasis Type="Italic">N</Emphasis>-(3-phenylprop-2-enylidene)aniline

Abstract  

New Schiff base compound 2-amino-N-(3-phenylprop-2-enylidene)aniline, 1, was prepared by condensation of cinnamaldehyde with o-phenylenediamine and characterized by elemental analyses, UV–Vis and FT-IR spectroscopy. The crystal structure of 1 was determined by X-ray crystallography from single-crystal data and displays a trans configuration about the C=N double bond. In the crystal structure of 1, the molecule is located on an inversion center, so that it is disordered around the center of central C–C bond. The results from both the experimental and theoretical calculations are compared in this paper.     

Synthesis,Crystal Structure,and Rotational Energy Profile of 3-Cyclopropyl-1,2,4-benzotriazine 1,4-Di-<Emphasis Type="Italic">N</Emphasis>-oxide

Abstract  

1,2,4-Benzotriazine 1,4-di-N-oxides are potent antitumor drug candidates that undergo in vivo bioreduction leading to selective DNA damage in the low oxygen (hypoxic) cells found in tumors. Tirapazamine (TPZ) is the lead compound in this family. Here we report on the synthesis, crystal structure, and conformational analysis of a new analog, 3-cyclopropyl-1,2,4-benzotriazine 1,4-di-N-oxide (3). Compound 3 (C₁₀H₁₀N₃O₂) crystallized in the monoclinic space group C2/c. Unit cell parameters for 3: a = 16.6306 (12), b = 7.799 (5), c = 16.0113 (11) ?, α = 90, β = 119.0440 (10), γ = 90, and z = 8.     

Nucleation kinetics,micro-crystallization and surface morphology studies of the nonlinear optical single-crystal l-lysinium trifluoroacetate

The organic nonlinear optical crystal of amino-carboxyl acid family, l-lysinium trifluoroacetate (abbreviated as LLTF) was successfully grown from its aqueous solution by the temperature-lowering technique. Its growth morphology was investigated based on the X-ray single-crystal diffraction data and the growth habits were studied using the micro-crystallization method. The metastable zonewidth and induction period were determined for the aqueous solution growth of LLTF. The surface free energy values were calculated from the experimental data. Nucleation kinetics and fundamental growth parameters such as critical radius, critical free energy and volume free energy change were also evaluated. Crystals of LLTF were obtained by the optimized nucleation parameters.     

“类金字塔”状ZnO改善硅异质结电池近红外波段外量子效率

因晶体硅是间接带隙半导体材料,其较低的吸收系数限制了对近红外波段入射光的吸收.为此,引入金属有机化学气相沉积(MOCVD)技术制备的ZnO薄膜,并通过改变掺杂流量和沉积时间调节ZnO∶ B(BZO)薄膜的光学和电学性能.将BZO薄膜用于硅异质结(SHJ)太阳电池的背反射电极,相比于传统结构,电池的反射率和外部量子效率在近红外波段得到显著改善.为进一步解释外量子效率增加的原因,在四甲基氢氧化铵(TMAH)湿法制绒的硅衬底上沉积BZO薄膜,得到了新型微纳米嵌套结构,并对其光吸收进行了测试分析.     

“三明治”PbS纳米晶/rGO复合材料的制备及其对NH_3的室温气敏性能研究

采用一步溶液法制备"三明治"PbS纳米晶/rGO复合材料,通过X射线衍射仪和场发射扫描电子显微镜对样品的晶体结构和表面形貌进行表征,并制作旁热式气敏元器件,测试其气敏特性。研究结果表明在PbS纳米晶/rGO复合材料中,PbS纳米晶均匀负载在rGO片层上,且复合材料存在类似"三明治"的三维结构。该复合材料在室温下对NH_3具有良好检测能力,对1000 ppm NH_3的灵敏度达到3.45,与纯PbS纳米晶及rGO相比,气敏性能得到显著提升,其最低检测极限为1 ppm,且具有良好的氨气选择性。对"三明治"PbS纳米晶/rGO复合材料气敏机理进行分析认为,rGO加入起到载流子传输层的作用,三维结构增加气体扩散速度及吸附面积。三明治状PbS纳米晶/rGO复合材料因其特殊结构及优异的气敏性能,有望在气敏领域得到广泛应用。     

Synthesis,Crystal Structure and Spectroscopy of <Emphasis Type="Italic">catena-</Emphasis>poly-bis(azido-<Emphasis Type="Italic">N1,N1</Emphasis>)(2-Aminopyrimidine)Copper(II)

Abstract The compound [Cu(ampym)(μ_1,1-N₃)₂]_n (ampym = 2-aminopyrimidine) has been synthesized and characterized by X-ray crystallography and infrared spectroscopy. In addition, Ligand Field and powder EPR measurements have been performed. The structure is solved in space group P21/c with a = 7.303(2), b = 19.716(4), c = 5.949(1) ?, β = 98.17(3), V = 847.9(3) ?³, Z = 2 with final R = 0.0382. The coordination geometry around the Cu(II) ion is distorted square pyramidal, with four nitrogen atoms of four bridging azido anions in the basal plane with Cu–N distances that range from 1.998(3) to 2.069(3) ?. The apical position is occupied by a nitrogen atom of the ampym molecule at a Cu–N distance of 2.169(3) ?. The trans-basal angles are 165.7(1) and 143.9(1)°. Weak hydrogen bonding is observed between the two amine hydrogen atoms and nitrogen of an azide anion and the pyrimidine-ring nitrogen atom of a neighbouring molecule (N···N distances 3.174(5), 3.106(4) ?). These last hydrogen bonds (N7···N3) are forming so-called “Watson-Crick type” hydrogen bonds. In the infrared the vibrations of the coordinated azide anion are observed at 2,062, 1,273 and 655 cm⁻¹, while the Cu–N vibrations are observed at 370 and 224 cm⁻¹. Ligand-field and EPR spectra are uneventful and give spectral parameters expected in the range for such Cu(II) compounds. Magnetic susceptibility measurements reveal a weak antiferromagnetic interaction between the Cu(II) ions. Index Abstract A new Cu(II) compound, [Cu(2-aminopyrimidine)(μ_1,1-N₃)₂]_n has been synthesized and characterized by X-ray crystallography and by IR, Ligand Field, EPR spectroscopy and magnetic susceptibility. The coordination geometry around the Cu(II) ion is distorted square pyramidal, with four nitrogen atoms of four bridging azido ligands in the basal plane with Cu–N distances that range from 1.998(3) to 2.069(3) ?. The apical position is occupied by a nitrogen atom of the ampym molecule at a Cu–N distance of 2.169(3) ?. Also a very interesting hydrogen bond system occurs between pairs of ligands in the lattice. .     

On the dependence of the properties of glasses on cooling and heating rates: I. Entropy, entropy production, and glass transition temperature

The glass transition is theoretically described in terms of a generic non-equilibrium thermodynamics approach employing De Donder's structural order parameter method, appropriate expressions for the relaxation behavior of glass-forming systems and a simplified but qualitative correct model of glass-forming melts with one order parameter related to the free volume of the system. Employing this approach the behavior of a variety of thermodynamic quantities describing glass-forming systems in vitrification and devitrification processes is interpreted theoretically. The present paper is devoted to the computation of the entropy, the entropy production and the glass transition temperature in dependence on the cooling and heating rates, varying latter parameter in a broad interval. A comparison with experimental results is given and some further consequences and possible extensions are discussed briefly.