Papers by Keyword: Morphology Control

Abstract: Semisolid process can be used as grain refining method to replace conventional chemical grain refining approach. Typical semisolid slurry making techniques were introduced in the paper as potential semisolid grain refining methods. The temperature and morphology control for grain refining through semisolid process were enhanced to achieve fine particle size and large particle number rather than spheroidal particle shape or low viscosity of the slurry comparing with conventional rheo-forming process. The grain refinement effect was demonstrated by a 40 mm cylinder casting of AZ31 alloy.

Abstract: High-quality flaky α-Al₂O₃ powder with regular morphology, uniform size, larger diameter-thickness proportion and excellent dispersibility in water and free from agglomeration and staggered growth was obtained on the basis of molten salt synthesis method. The effects of experiment parameter on the particle size and morphology of flaky alumina powder were studied. The mechanism of morphology control was discussed.

Abstract: A low-cost raw material, bittern obtained from the production process of sea salt, was used to prepare magnesium oxysulfate hydrate (MgSO₄·5Mg (OH)₂·2H₂O, abbreviated as 152MOS) whiskers via hydrothermal synthesis with ammonia and magnesium sulfate as the other starting raw materials. The bittern was firstly filtered and then used directly without de-coloring. X-ray powder diffraction (XRD), transmission electron microscope (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) were employed to investigate the composition and morphology of the products. It was found that the 152MOS whiskers synthesized from bittern at 190°C for 3 hours exhibited fanlike morphology. The formation of the fanlike whiskers was inhibited and most of the whiskers presented as single fibers when ethanol was used as crystal control agent in the hydrothermal process. From the two-dimensional steps observed at tips of the whiskers, a possible growth mechanism was speculated that it was the extension of dislocations that made the growth of the whiskers.

Abstract: We controlled morphologies of F-doped SnO₂ (FTO) thin films via an electrochemical method. To obtain rough and porous surface of the FTO thin films, a potentiostat/galvanostat was used. Field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were employed to demonstrate the morphological changes of FTO surface. The electrical and optical properties of the FTO thin films were analyzed using Hall effect measurement system and UV-vis spectrophotometry. Also, morphology controlled the FTO thin films would be applied to dye-sensitized solar cells.

Abstract: SAPO-11 and SAPO-47 crystals have been synthesized using diethylamine (DEA) as the structure-directing agent (SDA) and their morphology have been controlled successfully by varying aging duration. The single crystals were obtained in a short aging duration while film and island-like crystals were obtained in a long aging duration. The effect of SiO2/Al2O3 ration and content of HF on SAPO-47 crystals have been investigated. High molar ration of SiO2/Al2O3 and high content of HF is tend to synthesize larger crystals of SAPO-47. All the samples were characterized by XRD and SEM.

Abstract: High after-grow intensity with controllable morphology SrAl₂O₄: Eu, Dy phosphors were synthesized by an innovative combustion-melted-salt-assistant-Sol-Gel (CMSASG) method, by using Oxides, Carbonate, Nitric acid, Polyethylene glycols and Urea as raw materials, Gel-forming at 100°C, Combustion under 450°C, Melted-salt-calcination at 1250°C. The luminescent intensity and after-grow intensity of the SrAl₂O₄: Eu, Dy phosphors with the suitable pair-dope synthesized by CMSASG method are higher than those of commercial samples. The size of the phosphor with excellent luminescent characteristics and shape of sphericity or near sphericity synthesized can be controlled from about 200 nm to 10 μm.

Abstract: Shape-controllable polyaniline (PANI) nanostructures varying from fibers to hairy-PANI were synthesized via chemical oxidation polymerization with perchloric acid as dopant. It has been achieved just by adding extra aniline in the later phase of the same reaction or by adjusting reactive temperature. The diameters of the hairy-PANI fibers can be controlled to 300nm. Scanning electron microscopy was applied to investigate various kinds of morphologies. The mechanism of forming hairy-fiber morphologies was proposed to the mole ratio of aniline to APS in the later polymerization phase. X-ray diffraction pattern suggested that PANI were an amorphous character. Conductivity of polyaniline synthesized at room temperature was only 10-1 S cm−1 level. The specific surfacearea of the hairy- fibers PANI is more than that of fibers PANI.

Abstract: Nano-Cu₂O has wide application prospects in the fields of chemical industry and engineering due to its special optical, electrical and catalytic properties. The nano-particles with different morphological structure and particle size have different physical-chemical properties and different application fields. Therefore, this article reviewed the preparation methods of Nano-Cu₂O at high/room temperature and the key point of its morphology control.

Abstract: It is very important for spheroidic metal cobalt powders production to control the morphology of cobalt oxalate powders precursor. The spheroidic cobalt oxalate powders were prepared by conventional precipitation when a pulsed electromagnetic field (PEMF) was introduced. Scanning electron microscopy (SEM) images and X-ray powder diffraction (XRD) were used to characterize morphologies and phase structures of the cobalt oxalate powders. The research results show that a pulsed electromagnetic field (PEMF) play a key role in the process of preparation of spheroidic cobalt oxalate powders. In addition, a possible morphology control mechanism was preliminarily discussed based on the effects of PEMF on the process of growth of cobalt oxalate particles.

Abstract: The morphology of PVA/Na-MMT composite under different freezing technology conditions was studied. Inlfuence of PVA content and frozen conditions on microstructure and formation mechanism of PVA/Na-MMT composite materials were analyzed using scanning electron microscopy(SEM). The experiment results show that the structure of freeze-dried PVA/Na-MMT composite is influenced by both frozen technology and PVA dosage. PVA/Na-MMT composite frozen in Low-temperature refrigerator presented honeycomb-like structure when PVA dosage was 1%, and when the dosage of PVA was 2%, 3%, 4% respectively, the composite exposed wrinkle superposition structure. In liquid nitrogen frozen, Fiber-like structure of PVA/Na-MMT composite was obtained when the PVA content more than 3%.