The effects of heat-treatment on the structure evolution and crystallinity of ZnTiO3 nano-crystals prepared by Pechini process

Sol-gel technique emphasing the Pechini process has been employed for the preparation of nano-sized ZnTiO₃ powders. Results of thermal analysis are given, including both DTA and TG. The decomposition of the precursor proceeded in four major steps, which include dehydration reaction, decomposition, combustion reaction and ZnTiO₃ phase formation. The optimum temperature for ZnTiO₃ powder calcination is 800 °C, which is determined by calculating the intensity and area of XRD peaks. The TEM observation shows that the powders existed in the mode of polycrystalline structure and the average grain size is about 30 nm. Moreover, FT-IR measurement is given for the relationship of the cationic environment in ZnTiO₃ structure during the heat-treatment.     

Ordering of silver flowerlike nanosheet structures on an aluminium substrate

We present a facile method for ordering flowerlike structures of silver nanosheets on an aluminium covered surface. It is shown that using a combination of electron-beam lithography and standard silver mirror reaction, structures of silver nanosheets can be grown at predefined positions as single or multiple “flowers”, depending on the underling bare aluminium pattern. Arbitrary shaped areas, defined by electron-beam lithography, can be covered with closely packed silver nanosheets.     

Hg Substitution Effect on Superconductivity and Crystal Structure of MgB2

Polycrystalline Mg1-xHgxB2 samples with x=0, 1%, 2.5%, 5%, 7.5%, and 10% have been synthesized by solid-state reaction. Different from the substitution effect of Al, C, Li, etc. on crystal structure of MgB2, Hg substitution for Mg results in an increase of the lattice constant in both a and c directions. The superconductivity of MgB2 is also suppressed by Hg substitution. The observed suppression of super-conductivity by Hg substitution is discussed in terms of the interband impurity scattering effect in two-band superconductors.     

Growth of Yb-doped Y2O3 single crystal rods by the micro-pulling-down method

The rare-earth sesquioxides (RE₂O₃, RE = Lu, Y and Sc) are very promising host crystals for advanced laser diode (LD)-pumped Yb³⁺-doped solid-state lasers due to unusual combination, almost unique of favourable structural, thermal and spectroscopic properties which are described. In spite of these favourable properties, the bulk single crystal growth technology for the rare-earth sesquioxides has not been established yet. The extremely high melting temperature at around 2400 °C has prevented it. However, we shall show that yttrium oxide crystals (Yb_xY_1−x)₂O₃, x = 0.0, 0.005, 0.05, 0.08 and 0.15 of cylindrical shape as laser rods with 4.2 mm in diameter and 15-20 mm in length have been grown from rhenium crucibles by the micro-pulling-down method. The crystal quality characterisation of undoped Y₂O₃ crystal was determined using X-ray rocking curve (XRC) analysis. Yb were homogeneously distributed in Y₂O₃ host crystal.     

Characterization and Growth Process of Copper Nanodisks

Copper nanocrystals with plate‐like morphologies and face‐centered cubic (fcc) structures have been synthesized in mixed reverse micelles with a large excess of reducing agent. High‐resolution transmission electron microscopy images and image simulations show the presence of multiple twin defects parallel to the (111) surface responsible for the forbidden reflections 1/3{422} of the fcc structure. A growth process related to the formation of twin defects is proposed to explain the existence of these morphologies.     

Influence of temperature on accelerated lactose crystallization in dulce de leche

The aims of the present work were to study the crystallization of lactose in dulce de leche and to evaluate the influence of temperature on this process. Samples of approximately 1 g were placed in plastic containers and stored at –5, 5, 20 and 35°C for 25 days. Lactose crystal and lactose crystal agglomerate numbers and size were measured by using an optical microscope. Results suggested that stirring and placing a small sample of dulce de leche in a small container induced lactose crystallization. Lower storage temperatures resulted in an increase of crystal and agglomerate number but in a decrease of crystal and agglomerate size. The effect of temperature on crystal and agglomerate growth rates could be attributed to the effect of temperature on viscosity, as lower temperatures resulted in decreased crystal mobility in dulce de leche and therefore reduced crystal and agglomerate growth rate.     

Intergranular pressure solution in internally wetted polycrystals: Effect of additives

Wetting of grain boundaries in polycrystalline materials leads to considerable changes in their physicochemical and mechanical properties. Under a constant compressive load, internally wetted materials display an enhanced deformability; creep rate increases sometimes by several orders of magnitude. The dominant creep mechanism is known as dissolution–precipitation or pressure solution; a stress-induced excessive chemical potential provides a driving force for dissolution of material within grain contacts, diffusion through the grain boundary solution film and re-precipitation elsewhere. Sensitivity of pressure solution rate to the chemical composition of the intergranular liquid was reported earlier, but the underlying mechanisms were poorly understood. In the present work, the creep experiments were carried out on poly- or monocrystalline sodium chloride in the presence of NaCl aqueous solution (pure or containing additives such as copper, magnesium and lead chlorides, K₄Fe(CN)₆ and urea). In all cases, pressure solution has been shown to be the main deformation mechanism. Creep rate decreases in the presence of additives which are known to affect the dissolution and growth processes of sodium chloride or its concentration in the brine. Rate-limiting stage (dissolution or diffusion) in various environments has been identified.     

Synthesis of ZSM-23/ZSM-22 intergrowth zeolite with a novel dual-template strategy

ZSM-23/ZSM-22 intergrowth zeolite with fixed proportion of 60%ZSM-23/40%ZSM-22 has been synthesized with a novel dual-template strategy. The products were characterized by X-ray diffraction and scanning electron microscopy. Dimethylamine and diethylamine were used together as a dual-template system. The molar ratio of diethylamine to dimethylamine, which was changed with the type of aluminum source, was the key factor for the synthesis of intergrowth zeolites. A molar ratio of diethylamine to dimethylamine of 1:24 could result in an ZSM-23/ZSM-22 intergrowth zeolite if aluminum sulfate was used as aluminum source, whereas a molar ratio of diethylamine to dimethylamine of 1:12 was required to get an ZSM-23/ZSM-22 intergrowth zeolite if sodium metaaluminate was used. Furthermore, fluoride anion could be involved in the process as a crystallization promoter.     

点阵式液晶显示系统的设计

本文介绍点阵式液晶显示系统的设计和编程。重点讨论了点阵液晶显示系统各模块之间的接口信号和显示控制器编程中的一些关键问题，如屏、层、区的概念、显示存储器管理以及自定义字符的实现。