Graphite-diamond conversion proceeded by the use of carburized cobalt solvent

Cobalt was carburized by CO -treatment and used as solvent metal in graphite-diamond conversion experiments. The products were correlated to those obtained by the usages of untreated solvents. In the case of carburized Co, a fairy amount of small crystals of diamond were found on a metal-graphite boundary and in a metallic portion close to the boundary. Most of the produced crystals exhibited irregular shape but some crystals had well-developed (111) plane. The temperatures for the synthesis were not necessarily high and sufficient to remain in the range below the melting point of metal, indicating that the nucleation and the growth of diamond took place under solid state. When untreated metals were used as the solvents, the yield of diamond after the synthesis was low at these temperature conditions.     

Microtopographical and Raman spectral studies on calcium sulphate dihydrate (gypsum) crystals grown in silica gel in the presence and absence of barium chloride as additive

A procedure for the growth of calcium sulphate dihydrate (gypsum) crystals, CaSO₄ · 2H₂O, by a gel technique in the presence of barium chloride as an additive as well as without the additive, is described. Optimum conditions for the growth of good quality crystals are worked out. Needle-shaped crystals with well-defined prism faces are obtained. Microtopographical studies of the crystals are carried out. The observed surface structures on the prism faces of the crystals include vertical striations and parallelogram-shaped, oriented growth hillocks. Etch patterns on these faces are described and discussed. Reciprocity of the growth and etch mechanisms is established. Laser Raman spectral studies of these crystals are also made. Splitting of the non-degenerate fundamental is observed in the spectrum of the crystals grown in the presence of the additive. The present studies indicate that the additive used enhances the quality of the crystals.     

Colour Separation of Pictures In High-Speed Photography

Single layers of silver bromide crystals about 0.1μ in diameter attached to microscopic slides were prepared by evaporating silver under vacuum onto the slide and converting this to silver bromide in bromine vapour. The slides were then placed in a gently flowing solution consisting either of 0-1M ammonium bromide or alternatively, of OJM ammonium bromide and 1% gelatin. The solutions were kept slightly supersaturated with respect to silver bromide by cooling them before they passed over the samples. Under these conditions some of the crystals grew to a diameter of a few microns while remaining attached to the glass slide.

Thin tabular crystals were obtained. Gelatin slowed down the growth rate and, under the conditions used, led to the formation of crystals of more regular shape.     

Defect characterization of KTP single crystals

Potassium titanyl phosphate (KTP) is a relatively new nonlinear optical material with excellent combination of physical properties. This paper presents the combined etching and X-ray topographic studies carried out on KTP crystals with a view to characterizing their defects. KTP crystals employed in this investigation were grown from flux. Optical microscopic study of habit faces revealed growth layers and growth hillocks on (100) and (011) faces respectively. Etching of (011) habit faces proved that growth hillocks corresponded to the emergence point of dislocation out crops on these faces. The suitability of the new etchant to reveal dislocation was confirmed by etching the matched pairs obtained by cleaving. The defects present in the crystal were also studied by X-ray topography. The defect configuration in these crystals is characteristic of crystals grown from solution. The dislocations arc predominantly linear with their origin either at the nucleation centre or inclusions. In general, grown crystals were found to have low dislocation density and often large volumes of crystals free from dislocation could be obtained.     

四丁基溴化铵水合物结晶过程的可视化研究

对静止状态下四丁基溴化铵水溶液在铜板表面上的降温结晶过程进行了研究。结合降温过程的温度测量和可视化研究,得出了水和不同质量分数四丁基溴化铵水合物结晶温度曲线,分析了曲线的异同,并对结晶过程的图像进行了分析讨论。研究表明:铜板表面结晶生成的位置具有随机性;质量分数为10%的TBAB溶液中A型晶体较B型晶体更容易生成,质量分数分别为20%和30%的TBAB溶液中A型晶体与B型晶体同时生成。结晶生长速度与铜板表面纹理方向有关。     

Effect of electric field on the growth of barium molybdate crystals in silica gel

The growth of BaMoO₄ crystals in silica gel under the influence of an externally applied uniform electric field is studied. The habit changes resulting from different growth parameters are reported. Crystals up to 4.0 mm×1.2 mm×0.9 mm were obtained under field. The morphology of some crystals is examined by optical and scanning electron microscopy.     

真空气相沉积可控制备有机半导体单晶薄膜

利用多温区温度可控的真空气相沉积设备,在热氧化硅片衬底上沉积了并五苯（PEN）与甲氧基寡聚苯乙烯撑（MOPV）2种有机半导体材料的薄膜。研究了不同的沉积条件下有机半导体材料在二氧化硅衬底上的成核和生长模式。MOPV的生长遵循Volmer-Weber模式。在理想的条件下分别得到了岛状与线状的单晶结构。偏振显微荧光研究证明单晶纳米线有显著的荧光各向异性。     

用于连续激光器的磷酸钛氧钾晶体的制备和性能

采用掺杂生长了一系 列用于大功率LD泵浦连续激光器倍频的磷酸钛氧四（KTiOPO4,KTP）,如：Nb:KTP、Na:KTP、Ce:KTP及Rb：KTP、Cs：KTP等,虽然其中一些具有比普通KTP晶体高的效率和抗光损伤阈值,并在4%Nb:KTP中实现了NCPM,但是在大部分掺杂晶体中生长条纹、包裹体均较严重,影响了晶体的均匀性,不适于大功率连续激光器应用,为提高KTP晶体均匀性和抗光损伤阈值,采用特制原料和改进工艺生长了优质KTP晶体,可用于大功率LD泵浦的Nd:YVO4连续激光器倍频,最大的连续绿光输出功率达到5W。     

Nucleation and growth of CdC2O4·3H2O single crystals in silica gels

As part of our work on growth of cadmium oxalate single crystals in gels, we describe here variation of nucleation density and growth of these crystals as a function of concentration of feed solution, gel ageing, gel density, gel pH and intermediate neutral gel column. While high density and high pH gels have been found to produce opaque crystals, good quality transparent single crystals have been obtained in low density and low pH gels. It was observed that the intermediate neutral gel column and gel ageing considerably reduced the number of nucleation sites and increased the size of the crystals without affecting their quality. By concentration programming the size of the crystals increased.     

In situ measurement of crystal growth rate of zeolite

To clarify the growth behavior of zeolite crystals under hydrothermal synthesis conditions, the growth process of ZSM-5 type zeolite crystals was studied using two kinds of in situ observation apparatus. Direct observation of ZSM-5 crystals from amorphous gels during steaming and silicalite crystals from clear aqueous solutions was performed. During the stationary growing stage, a constant rate of crystal growth of zeolites was observed directly for both zeolite crystals. In the case of ZSM-5 zeolites from gels, it was also found that after a certain induction time, crystals grew to 10–20 μm in size, after which no further growth was observed. On the other hand, in the case of silicalite crystals from aqueous solutions, the induction time hardly existed. The size distribution of crystals and the activation energy for crystal growth are also discussed.     

Growth and study of barium oxalate single crystals in agar gel

Barium oxalate was grown in agar gel at ambient temperature. The effect of various parameters like gel concentration, gel setting time and concentration of the reactants on the growth of these crystals was studied. Prismatic platy shaped spherulites and dendrites were obtained. The grown crystals were characterized by X-ray powder diffractometry, infrared spectroscopy, thermogravimetric and differential thermal analysis. An attempt is made to explain the spherulitic growth mechanism.     

The effect of stationary and sweeping frequency AC electric fields on frost crystal removal on a cold plate

The effect of stationary and sweeping frequency AC electric fields on frost crystals growth and frost control/removal on a cold plate was studied for the first time in this paper. The main results of this study showed that the presence of AC electric fields can greatly affect both the frost crystals growth pattern and mass accumulation on cold surfaces. The ice surface electrical properties and basic electrostatics were used to explain the main findings in this paper. Up to 46% frost reduction was obtained when the electric field frequency spanned 370 Hz to 7.5 kHz while the applied voltage was 14.5 kV. Two different sets of environmental conditions were tested, which showed that the plate temperature placed an important effect on frost crystals growth under electric fields. An optimum application time of the AC electric fields was found based on least frost mass accumulation on the cold plate.     

Morphology Change of Metastable Regrown Graphite with Boron Additive under HPHT

By temperature gradient method under high pressure and high temperature(HPHT),with NiMnCo alloy as the solvent metal,at diamond-stable region of about 5.4 GPa and 1500 K,metastable regrown graphite crystals of different morphology were synthesized.With B as an additive incorporated into the NiMnCo-C system,metastable regrown graphite crystals of sphere-like shape were firstly obtained under HPHT.If the growth system does not contain B,sheet-like regrown graphite crystals,most with regular hexagonal morpholo...     

Immobilization of epidermal growth factor on titanium and stainless steel surfaces via dopamine treatment

Titanium and stainless steel were modified with dopamine for the immobilization of biomolecules, epidermal growth factor (EGF). First, the treatment of metal surfaces with a dopamine solution under different pH conditions was investigated. At higher pH, the dopamine solution turned brown and formed precipitates. Treatment of the metals with dopamine at pH 8.5 also resulted in the development of brown color at the surface of the metals. The hydrophobicity of the surfaces increased after treatment with dopamine, independently of pH. X-ray photoelectron spectroscopy revealed the formation of a significant amount of an organic layer on both surfaces at pH 8.5. According to ellipsometry measurements, the organic layer formed at pH 8.5 was about 1000 times as thick as that formed at pH 4.5. The amount of amino groups in the layer formed at pH 8.5 was also higher than that observed in the layer formed at pH 4.5. EGF molecules were immobilized onto the dopamine-treated surfaces via a coupling reaction using carbodiimide. A greater amount of EGF was immobilized on surfaces treated at pH 8.5 compared with pH 4.5. Significantly higher growth of rat fibroblast cells was observed on the two EGF-immobilized surfaces compared with non-immobilized surfaces in the presence of EGF. The present study demonstrated that metals can become bioactive via the surface immobilization of a growth factor and that the effect of the immobilized growth factor on metals was greater than that of soluble growth factor.     

Critical roles for EGFR and EGFR–HER2 clusters in EGF binding of SW620 human carcinoma cells

Epidermal growth factor (EGF) signalling regulates normal epithelial and other cell growth, with EGF receptor (EGFR) overexpression reported in many cancers. However, the role of EGFR clusters in cancer and their dependence on EGF binding is unclear. We present novel single-molecule total internal reflection fluorescence microscopy of (i) EGF and EGFR in living cancer cells, (ii) the action of anti-cancer drugs that separately target EGFR and human EGFR2 (HER2) on these cells and (iii) EGFR–HER2 interactions. We selected human epithelial SW620 carcinoma cells for their low level of native EGFR expression, for stable transfection with fluorescent protein labelled EGFR, and imaged these using single-molecule localization microscopy to quantify receptor architectures and dynamics upon EGF binding. Prior to EGF binding, we observe pre-formed EGFR clusters. Unexpectedly, clusters likely contain both EGFR and HER2, consistent with co-diffusion of EGFR and HER2 observed in a different model CHO-K1 cell line, whose stoichiometry increases following EGF binding. We observe a mean EGFR : EGF stoichiometry of approximately 4 : 1 for plasma membrane-colocalized EGFR–EGF that we can explain using novel time-dependent kinetics modelling, indicating preferential ligand binding to monomers. Our results may inform future cancer drug developments.     

Crystallization of ZSM-5 zeolite under microgravity

Crystal growth of ZSM-5 zeolite under microgravity was carried out using a Soviet reentry system. The space-grown zeolite was composed of grains of uniform shape and size (ca. 10 μm). Most of zeolite grains were linked with each other by the edge of the grain. The electron diffraction of each grain showed a single-crystal diffraction pattern, indicating the presence of well-crystallized zeolite crystal. The relatively large difference in the surface Al concentration existed between different crystals of the space-grown zeolite, as compared with the zeolite crystals synthesized in the ground with stirring. Based on these results, the crystals growth of zeolite in the microgravity environment was discussed.     

有机小分子调控下的羟基磷灰石的合成

以甘氨酸和乙二胺为模型分子,在中性条件下采用水热法,研究有机小分子对羟基磷灰石(HAP)晶体生长形貌的影响。采用透射电子显微镜(TEM)、X射线衍射仪(XRD)和傅里叶变换红外光谱仪(FTIR)分析了合成产物的形貌、结构和组成。实验结果表明,甘氨酸诱导合成的HAP呈六方棒状,长500～2000nm,直径为50～100nm;在乙二胺的诱导下合成了长100～250nm、宽30～50nm的片状HAP晶体。对照空白实验可知,小分子上的极性基团通过静电吸附或分子占位显著影响HAP的形貌。     

超临界聚合法等规聚丙烯的结晶行为

采用差示扫描量热法及带热台在线偏光显微镜直接观察法,研究了超临界聚合与常规淤浆聚合这两种不同聚合工艺所制备等规聚丙烯的等温结晶行为.结果表明,超临界法聚丙烯（sc-iPP）由于其较低的分子量及较窄的分布,使得等温结晶速率比常规淤浆法聚丙烯（c-iPP）快,结晶度高,且sc-iPP的晶体呈负光性,倾向于异相成核.而c-iPP的晶体则呈混光性,倾向于均相成核,但两者均为典型的球晶,均体现热成核机理.     

Growth and characterization of large crystals of GdBa2Cu3O7 superconductor

We report here on the growth of large crystals of Gd-Ba-Cu-O superconductor by using the ‘K₂CO₃-method’ adopted earlier for preparing oriented ceramics and large crystals of Y-Ba-Cu-O superconductors. The temperature favourable for the growth of GdBaCuO crystals is found to be higher than that required for YBaCuO crystals. Also, the crystal perfection is better for these crystals and as a result, the oxygenation of the sample becomes more difficult. Resistivity measurements on these samples show a sharp drop in resistivity at 90 K which then tails off at lower temperatures and attains zero resistance around 35 K. Such behaviour is normally due to an inhomogeneous oxygen content in the sample. Chemical analysis shows that the deviation from ‘123’ composition in GdBaCuO-samples is much less as compared to YBaCuO-samples obtained by the same technique.     

Formation and characterization of diamond crystals synthesized by microwave plasma CVD system

Abstract

Diamond crystals have been successfully synthesized on (100) Si wafer using microwave plasma CVD. The growth was conditioned in a flowing system in which the parameters, such as CH₄/H₂ ratio, pressure, temperature and microwave power were varied. Cubo‐octahedra or tetrakaidecahedra are the equilibrium shape of diamond single crystals obtained under all conditions and are therefore the basic unit for the formation of polycrystalline diamond films, mostly through repetitive twinning and secondary growth of diamond crystals on {100} habit planes of cubo‐octahedra. Both X‐ray diffraction and Raman spectroscopy were used to facilitate the analysis of the diamond crystallinity and purity. These qualities are similar to those of natural diamonds.