Growth and characterization of a new metal-organic crystal: Potassium thiourea iodide

Single crystals of potassium thiourea iodide (PTI), a semiorganic nonlinear optical crystal, have been grown from low temperature solution growth method by a slow evaporation technique at room temperature. Single crystal X-ray diffraction pattern and FTIR spectrum analysis has confirmed the formation of the new crystal. PTI has good optical transmission in the entire visible region, which is an essential requirement for a nonlinear crystal.     

The crystal growth of bismuth iodide

The growth of platelet crystals of bismuth iodide 1 to 10 microns thick by an open flow sublimation technique is described. The best crystals were prepared in a Pyrex glass apparatus by passing argon, at a flow rate of 40 cc/min. over iodine at 25°C. and reacting this gas mixture with elemental bismuth heated to 310°C. Bismuth iodide crystals, suitable for optical absorption measurements grew in a temperature gradient ranging from 210°C. to 90°C. The optical properties of the crystals were dependent on the growth temperature.     

Simultaneous investigation of the crystal structure and electrical properties of crystallized germanium films by UHV in situ electron microscopy

Three types of crystallization have been observed, depending on the gaseous contamination of the a-Ge films. A correlation between the crystallized structures and the corresponding electrical properties was found. In order to explain the measured Hall mobility of the crystalline Ge films, a model has been constructed in which the potential barrier of the grain boundaries is taken into account.     

The crystal structure of a new ternary silicide in the system rare-earth-ruthenium-silicon

The structural properties of a new group of ternary silicides in the system M-Ru-Si (M = Y, La, Th and RE) have been investigated. The structure is presented as determined from X-ray powder diffraction.     

Magnetic properties and structure of cobalt-platinum thin films

The magnetic properties of RF sputtered Co-Pt alloy thin films were studied as a function of Pt content from 0 to 80 at%. At room temperature, ferromagnetic films were obtained in the range 0-32 and 40-80 at% Pt. For Pt contents between 32 and 40 at%, discontinuities in the magnetization, magnetostriction, and coercivity versus Pt content were observed; however no discontinuity was observed in the resistivity. The structure of films containing about 25 at% Pt is a mixture of hexagonal and face-centered cubic (FCC) phases. At this composition the magnetostriction is small, but coercivities are large-700 to 2000 Oe-and dependent upon film thickness. The coercivities of these films do not change with heat treatment up to temperatures of 600°C but decrease markedly at 700°C. The properties of equiatomic Co-Pt film s are similar to those of bulk alloys. In particular the large coercivity observed in films after heal treatment at 500° to 700°C is due to the formation of an ordered tetragonal phase within the face-centered cubic matrix. The structure of films of about 75 at% Pt is initially a disordered face-centered cubic phase and with heat treatment beginning at 500°C an ordered face-centered cubic phase forms. The coercivity of these films (∼200 Oe) does not change with annealing at 500°C. It decreases slightly upon further annealing at 600°C to 700°C. Electron microscope observations were used to correlate the magnetic properties with film structure.     

Magnetic properties of vacancies on the triangular plane 3He crystal

The ground state of the plane quantum Fermi crystal with a triangular lattice is considered. Using symmetry properties, the ground state wave function is constructed and a variational estimate of the ground state energy is obtained. The ground state corresponds to an unsaturated ferromagnet with spin equal to one-third of the maximum spin. Some other nonalternate lattices are also considered. The spectrum of elementary excitations for a finite concentration of the vacancies is studied. The existence of low-lying spin excitations with a small gap is predicted. Ordinary gapless spin waves also exist.     

Domain structure and optical properties of colloidal photonic crystal

Thin colloidal photonic crystals were grown using shear-flow crystallization of polystyrene colloidal nanoparticles. The arrays consist of two types of domains, which are clearly visible on scanning electron microscopy patterns. Both domains have cubic close packing and are distinguished by their orientation with regards to substrate surface. The positions of the main minima in the visible-near-IR transmittance spectrum of the arrays as well as the dependence of these minima on the angle of the light incidence have been measured and interpreted using photon band structure of the two-component media.     

水热合成法制备微纳米MnO_2晶体不同形貌的电磁特性

本文采用水热合成法,以(NH4)2S2O8作氧化剂,以MnSO4为锰源,在不同水热反应时间下制备了不同晶体结构和形貌的二氧化锰。利用X射线粉末衍射(XRD),扫描电子显微镜(SEM)和透射电子显微镜(TEM)对产物进行成分、晶型和形貌进行分析,并通过电磁参数的测试对产物的电磁特性以及电磁波损耗机制进行讨论。结果表明,水热反应时间由1h逐渐增加到48h后,二氧化锰晶体结构由纯γ型逐渐转变为纯β型,中间产物为γ、α和β的混合体,二氧化锰的形貌也由球状经团絮状后逐渐转变为直径约为5-10nm纳米线状。复介电常数随反应时间增加而增加,复磁导率却正好相反,由此最后分析了二氧化锰的电磁波损耗机制。     

A transmission electron microscopy study of polymer-stabilised liquid crystal structure

A method has been established for observing the internal structure of the network component of polymer-stabilised liquid crystals. In situ photopolymerisation of a mesogenic diacrylate monomer using ultraviolet light leads to a sparse network (1 wt%) within a nematic host. Following polymerisation, the host was removed through dissolution in heptane, revealing the network. In order to observe a cross-section through the network, it was embedded in a resin and then sectioned using an ultramicrotome. However, imaging of the network was not possible due to poor contrast. To improve this, several reagents were used for network staining, but only one was successful: bromine. The use of a Melinex-resin composite for sectioning was also found to be advantageous. Imaging of the network using transmission electron microscopy revealed solid droplets of width 0.07–0.20 m, possessing an open, yet homogeneous structure, with no evidence for any large-scale internal structures.     

Synthesis,crystal structure and thermal analysis of a new stilbazolium salt crystal

A new organic crystal of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium benzene sulfonate (DASBS) was synthesized and characterized for the first time. It is a derivative of 4-N, N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) with the benzene sulfonate replacing p-toluenesulfonate. Single crystal XRD demonstrated that the crystal structure of DASBS·H₂O was triclinic. The thermal analysis of this new crystal was also conducted, and the melting point was obtained to be 232°C.     

多面体低聚倍半硅氧烷晶粒诱导的聚乳酸结晶行为及性能

通过溶液及熔融两步共混方法,用带有环氧基的多面体低聚倍半硅氧烷(EVOS)对聚乳酸(PLA)进行改性,并对复合材料的力学性能、结晶性能和相态等方面进行了表征。实验结果表明,随着EVOS的加入,PLA冷结晶温度降低,结晶和熔融温度变化不大,结晶热和熔融热下降。1%的EVOS在PLA中实现了纳米尺度的分散,随着EVOS含量增加,球晶尺寸明显增加。当EVOS的添加量为5%时,材料的拉伸强度比纯PLA增加26.2%,达到最大值。     

晶体结构对化合物电学性质的影响

化合物的导电性包括电子(空穴)导电及离子导电两大部分.新材料的发展已将化合物的电学性质提到了急需研究的位置.随着对化合物电学性质研究的不断深入,发现了许多新现象,新性质和新材料,如氧化物高温超导体,稀土半导体,稀土巨磁阻材料等.这些都是电子(空穴)导电的实际应用.而由于新能源探索需适应保护环境的需要,传统的氧离子和质子导体成了人们的首选研究对象,以开发它们在燃料电池、氧分离膜,催化等方面的实际应用.由于不等价置换,价态变化及氧离子具有大的双电荷与阳离子基体的强相互作用及高迁移率,使得大多数的研究工作集中于化合物的结构畸变分析及精化,试图发现新的结构相或者新的电学材料.     

A new crystal structure for (BEDT-TTF)2SbF6 and some of its physical properties

A new crystal structure forbis (ethylenedithio)tetrathiafulvalene [(BEDT-TTF) ₂ SbF₆] was determined by single crystal X-ray diffraction. The crystal structure was refined in theP - 1 space group at room temperature. Crystal data for new structure are as follows: triclinic, a = 8.670 (2) Å,b = 8 664 (2) Å,c = 16.842 (5) Å,α = 89°.29 (2),β = 90°.71 (3),γ = 92°.67 (1),V = 1263.64 Å ³,Z = 2,D _x = 2.136 g cm ^-3, (Mo-Kα),λ = 0.7107 Å,R = 0.057 for a total of 5517 independent reflections. The donors form a trimerized column, and the band structure calculated by the tightbinding approximation shows band insulator properties. The temperature dependent of the d.c. resistivity shows a semiconducting behaviour with room temperature resistivity along the c-axis; ρ ₂₉₀ K = 5.6 ohm cm.     

Single crystal growth,structure and properties of TlHgBr3

High-quality inclusion-free single crystals of ternary thallium mercury bromide, TlHgBr₃, were successfully grown by Bridgman–Stockbarger method. For the pristine surface of the TlHgBr₃ single crystal, X-ray photoelectron core-level and valence-band spectra were measured. The comparison on a common energy scale of the X-ray photoelectron valence-band spectrum of TlHgBr₃ and the X-ray emission Br Kβ₂ band, representing peculiarities of the energy distribution of the Br 4p states revealed that the main contribution of the valence Br p states, occurred in the upper portion of the valence band, with also their significant contributions in other valence band regions. It has been determined that TlHgBr₃ is a semiconductor with the bandgap energy value of E_g = 2.51 eV at 100 K. The E_g value decreased up to 2.44 eV when temperature increased to 300 K.