Estimation of the drawing efficiency of hot spinning of co-polyester fibres in producing high degrees of preferred orientation

A range of liquid crystalline polyester fibres varying in diameter from 65 to 440m were produced by spinning from a hot melt. These were analysed for preferred orientation by flatplate X-ray diffraction to produce equatorial azimuthal densitometry scans/() which were processed to produce the corresponding planar orientation profiles/() corresponding to a Bragg separation of 0.448nm. A further mathematical analysis was applied to these to produce the respective molecular orientation profiles/() which may be more directly related to fibre mechanical properties,/() profiles from this analysis were matched against theoretical/() calculated by assuming an idealized mechanism of affine deformation with no orientation losses due to thermal perturbations. The theoretical draws ratios corresponding to the experimentally observed cos² were matched against experimentally observed draw ratios to produce ratios which indicate drawing efficiencies. Although preferred orientation increased with increasing draw ratios, the drawing efficiency diminished with draw ratio.     

Frictional property with preferred crystal orientation of platinum oxide and palladium oxide coatings synthesized by combinatorial sputter coating system

The combinatorial sputter coating system (COSCOS) has been newly developed, that can fabricate various kinds of coatings under precisely controlled lots of conditions such as selection of sputter gas and gas pressure, gas partial pressure, r.f. power, substrate temperature, distance between a substrate and a target, etc. COSCOS can also control the crystal preferred orientation of coatings which strongly affect those frictional property. Platinum oxide and palladium oxide coatings were synthesized by COSCOS, then the crystal structure was analyzed with X-ray diffraction spectroscopy and frictional properties of the coatings were measured by a tribometer at an atmospheric pressure.     

Droplet orientation and optical properties of polymer dispersed liquid crystal composite films

The electro-optic and thermo-optic properties of polymer dispersed liquid crystal (PDLC) films have been investigated. The effects of applied voltage and temperature on liquid crystal droplet morphology and its transmission characteristics were studied. Threshold voltage (V_th) and optical transmission increases with increasing temperature. It may be due to the reduction in effective voltage drop across the liquid crystal droplets in the composite matrix. The liquid crystal droplet size was found to vary in the range of 5–28 μm.     

The quantitative effects of crystal habit change on the film surface form and the preferred orientation during the growth of vacuum-condensed films

Our recent systematic observations by reflection electron diffraction showed that a basic feature of film growth of high melting point materials condensed in vacuum on substrates initially at room temperature is that, after the initial thin film of randomly oriented crystals, and the growth of faces and preferred orientation of a particular type at the film surface, a new type of face and preferred orientation is often developed in further strata of deposit growth.Calculations are made showing the effect of a change in crystal habit on the film surface element distribution and the nature of the new preferred orientation which is developed.The {211} habit and orientation in gold films, in further growth after the first-developed {111} habit and orientation, is discussed as an example of the calculations, which indicate a tilt δ of approximately 25° for the {211} orientation when the vapour angle of incidence i is 45°. This agrees with our observations, confirming that the {211} orientation arises from the habit change and not from nucleation by secondary {111} twinning.     

Mapping of the atomic lattice orientation of a graphite flake using macroscopic liquid crystal texture

The electronic properties of graphene depend critically on its lattice orientation and edge type. However, it is very difficult to identify them, and they are accessible only using sophisticated tools. In this paper, we show an easy and reliable way to reveal the lattice orientation and edge type of graphene and graphite flakes, i.e.?multi-layered graphene. Nematic liquid crystals have the potential to align themselves into three symmetric and equivalent orientations on crystalline graphite. The director of macroscopic texture due to the elasticity indicates the lattice orientation of the top graphite layer. By analyzing the director orientation using a polarizing optical microscope, we were able to show the lattice orientation, chiral angle and edge type of graphene and graphite flakes on the macroscopic scale. As liquid crystals are soft and easily removable, our technique has little chance of influencing the following processes for graphene manipulation.     

Morphology and preferred orientation of titanium nitride plates prepared by chemical vapour deposition

Thick titanium nitride (TiN _x ; x = 0.74–1.0) plates (up to 2 mm thick) were prepared by chemical vapour deposition using TiCl₄, NH₃ and H₂ as source gases at a total gas pressure, P _tot, of 4 kPa, deposition temperatures, T _dep, from 1373–1873 K, and NH₃/TiCl₄, m _N/Ti, gas molar ratio from 0.17–1.74. The effects of deposition conditions on morphology, preferred orientation and composition of CVD-TiN _x plates were investigated. Surface morphology changed from faceted to nodular texture with increasing m _N/Ti and T _dep. The faceted and nodular deposits showed columnar and shell-like fracture cross-sections, respectively. The composition (x = N/Ti) increased with increasing m _N/Ti and T _dep below m _N/Ti = 1.0, and was constant above m _N/Ti = 1.0. Three kinds of preferred orientations were observed: (100) orientation at low T _dep, (110) orientation at intermediate T _dep and low m _N/Ti, and (111) orientation at high T _dep and high m _N/Ti. This tendency is discussed thermodynamically, and explained as being due to changes in the degree of supersaturation in the gas phase.     

Observations of preferred orientation in high-Tc oxide superconductor tapes

Thin tapes of YBa₂Cu₃O_7−δ superconductor have been tape cast by the doctor blade technique. X-ray diffraction studies showed that the (00l) planes of these tapes, to a modest degree, became preferentially aligned parallel to surface of the tape. This modest degree of preferential alignment resulted in a significant increase in measured critical current density.     

Substrate-induced crystal plastic phase of a discotic liquid crystal

A new phase of a known discotic liquid crystal is observed at the interface with a rigid substrate. The structure of the substrate-induced phase has been characterized by atomic force microscopy, specular X-ray diffraction, and small-angle and wide-angle grazing incidence X-ray diffraction. The substrate-induced phase, which has a thickness of ～30 nm and a tetragonal symmetry, differs notably from the bulk phase. The occurrence of such phase casts a new light on alignment of discotic liquid crystals.     

Determination of preferred orientation degree of portlandite by using rocking curve of diffraction line

It is pointed out by theoretical analyses that calculating the preferred orientation degree of portlandite within the interfacial zone between cement paste and the aggregate, according to the currently accepted formula, can only be used as a qualitative method. The authors propose a method using the rocking curve of the diffraction line for determining the preferred orientation degree of portlandite and obtaining more precise results. This method can be used as a quantitative one.     

多晶硅薄膜的铝诱导晶化法制备及其晶粒的择优取向特性

采用铝诱导非晶硅薄膜晶化技术制备了多晶硅薄膜,并研究了多晶硅的成核和生长特性。非晶硅薄膜采用等离子体增强化学气相沉积法制备,其表面沉积铝薄膜后经不同温度的氮氛围退火处理。结果表明,退火后的硅薄膜层与铝层发生置换,所生长的多晶硅颗粒的平均尺寸约为150nm。X射线衍射分析结果揭示,薄膜的晶向显著依赖于退火温度,较低温度下,铝诱导晶化速率较慢,薄膜的优化晶向与非晶硅薄膜中团簇的初始原子排列趋势紧密相关。而较高温度下,铝诱导晶化促使多晶硅(111)择优成核及随后的固相生长。     

Effect of chelating agents on the preferred orientation of ZnO films by sol-gel process

The effect of chelating agents of ZnO precursor solutions on crystallization behavior was investigated. Two different additives, monoethanolamine (MEA) and diethanolamine (DEA), and crystalline Pt (111)/Si and amorphous SiN _x /Si substrates, were used for this study. ZnO film grown on SiN _x /Si from a DEA-chelated precursor solution shows a poorly oriented microstructure with weak crystallization peaks, while ZnO film grown on Pt(111)/Si shows a c-axis preferred orientation. In the case of ZnO films prepared with a MEA-chelated precursor solution, all films show a strong preferred orientation irrespective of substrate type. This result clearly demonstrates the role of the chelating agent on the crystallographic orientation and crystallization behavior of sol-gel processed ZnO films.     

Single-cell gap-transflective liquid crystal display using two optical modes of a bistable liquid crystal

We present a single-cell gap-transflective liquid crystal display (LCD) characterized by a π cell having bulk-type liquid crystal (LC) bistability and an optical film configuration. The π cell has two stable states, which are a twisted and a nontwisted LC state. We used the twisted LC state for the reflective part connected with nonpatterned electrodes, producing a vertical field in the proposed transflective LCD. Also the nontwisted LC state was for the transmissive part with interdigitated patterned electrodes driving an in-plane field in the device. The simulated and experimental results show good electro-optical characteristics in both the reflective and transmissive parts.     

Discrimination and mapping of phase distributions by automated crystal orientation measurement

Abstract

Automated crystal orientation measurement/mapping (ACOM) in the SEM enables a fast phase discrimination and the automated acquisition of phase distribution maps at submicrometre resolution, if the phases belong to different Laue groups or if their lattice constants are at least significantly different. The database can further be used for quantitative determination of phase contents, phase boundary characterisation, and mesoscale texture analysis for each phase, such as crystal orientation mapping (COM), texture analysis (orientation density function, pole figures, misorientation distribution function), characterisation of grain and phase boundaries, and orientation stereology.     

溅射时间对Mo薄膜结晶取向的影响

采用直流磁控溅射法在SLG衬底上沉积Mo薄膜,并用XRD、SEM、四探针等对薄膜进行表征,研究了沉积时间对薄膜晶体结构、表面形貌以及电学性能的影响。研究发现,沉积时间能够调节Mo薄膜的择优取向。溅射时间较短(5～10min)时,沉积的Mo薄膜呈(110)择优取向。溅射时间超过15min后,薄膜呈现(211)取向,且(211)晶面择优程度随沉积时间的增加而提高。随着择优取向的改变,薄膜的表面形貌由三角形颗粒变为长条形颗粒,电阻率也发生相应变化,由3.92×10-5Ω·cm增加到4.27×10-5Ω·cm再降低,对应薄膜生长的晶带模型由晶带T型组织变为晶带2组织。     

The loading history and crystal orientation effects on the size-dependency of single crystal diamond properties

Much research has been conducted to study the size-dependency of material properties, as can be found from the open literature. Recent results on combined size, rate and thermal effects further demonstrate the dominant influence of specimen size on material strength, as compared with the loading rate and thermal effects. However, little has been done to understand the loading history and crystal orientation effects on the size-dependency of material properties. To evaluate the safety and integrity of MEMS devices under general loading conditions, a series of molecular dynamics simulations are performed to investigate the size-dependency of single crystal diamond properties with various crystal orientations under shear/tension and tension/shear loading conditions. It appears from the preliminary findings that the loading history and crystal orientation do have certain influence on the size-dependency of material properties. Specifically, the failure pattern is insensitive to the loading history, which provides useful information for formulating a multi-scale material model under general loading conditions.