Hunan Boyun Dongfang Powder Metallurgy Co.

Changsha, China

Hunan Boyun Dongfang Powder Metallurgy Co.

Changsha, China
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Chen X.,Central South University | Li Y.,Hunan Boyun Dongfang Powder Metallurgy Co. | Zou D.,Hunan Boyun Dongfang Powder Metallurgy Co. | Liu Y.,Hunan Boyun Dongfang Powder Metallurgy Co. | And 5 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2017

Ultrafine complex basic cobalt carbonate and Co-Cr-V alloy powders were prepared by co-precipitation and thermal decomposition method. X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to analyze phase and crystal structure of as-synthesized powders, and inductively coupled plasma atomic emission spectrometer (ICP-AES) was used to determine element composition and content of alloy powders. The results show that the precursor can be indexed to pure phase of basic cobalt carbonate while alloyed powders consist of two cobalt phases corresponding to α-Co (fcc) and β-Co (hcp) respectively. The maximum content of α-Co reaches 82% (mass fraction) at pH=11. Combined the analysis of thermogravimetry-differential scanning calorimetry (TG-DSC), precursor powders were conducted in flowing argon with two characteristic peaks occurring at 259 and 951℃ associated to decomposition of basic cobalt carbonate. Scanning electron microscopy (SEM) was employed to observe the morphology change of as-synthesized powders and alloy powders. Specific surface area analyzer was used to determine the specific surface area of precursor and alloy powders. The precursor powders is extremely fine with average particle size ranged from 5~11 nm. The average particle size of alloy powders is much larger and in sub-micrometer range. The average particle size is a linear function of pH with the smallest partice size of 96 nm observed at pH=7. © 2017, Central South University Press. All right reserved.


Chen X.-Y.,Beijing University of Chemical Technology | Shang Y.-L.,Beijing University of Chemical Technology | Li Y.-H.,Beijing University of Chemical Technology | Wang J.-X.,Beijing University of Chemical Technology | And 7 more authors.
Chemical Engineering Journal | Year: 2015

Drugs with poor solubility in water, which indicates poor oral bioavailability, account for a considerable portion of new pharmaceutical candidates. Nanonization is a technique that overcomes this problem. However, current nanoionization methods have many disadvantages, including high energy demands, broad particle size distributions and the use of organic solvents. We report a new green method for preparing drug nano-particles by combining a subcritical water (SBCW) process with an anti-solvent precipitation method. The nano-particles processed through SBCW technology have a spherical morphology, a regular shape and a homogeneous particle size. Prednisolone nanoparticles averaging 31. nm in diameter were produced using this approach, and these particles were 10 times smaller size than the unprocessed drug. The resulting particle morphology depended strongly on operating conditions such as the temperature of the SBCW solution, the temperature of the anti-solvent and the concentration of the pharmaceutical excipients. Consequently, uniform prednisolone nanoparticles were produced through an environmentally friendly method. © 2014 Published by Elsevier B.V.


Yang X.-C.,Beijing University of Chemical Technology | Shang Y.-L.,Beijing University of Chemical Technology | Li Y.-H.,Beijing University of Chemical Technology | Zhai J.,China Coal Research Institute | And 4 more authors.
Journal of Nanomaterials | Year: 2014

Monodisperse iron oxide nanoparticles could be successfully synthesized with two kinds of precipitants through a precipitation method. As-prepared nanoparticles in the size around 10 nm with regular spherical-like shape were achieved by adjusting pH values. NaOH and NH· H were used as two precipitants for comparison. The average size of nanoparticles with NH· H precipitant got smaller and represented better dispersibility, while nanoparticles with NaOH precipitant represented better magnetic property. This work provided a simple method without using any organic solvents, organic metal salts, or surfactants which could easily obtain monodisperse nanoparticles with tunable morphology. © 2014 Xiao-Chen Yang et al.


Xiao H.-B.,Central South University | Li Y.-X.,Central South University | Li Y.-X.,Hunan Boyun Dongfang Powder Metallurgy Co. | Zou D.,Hunan Boyun Dongfang Powder Metallurgy Co. | And 4 more authors.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2014

Co-V-Cr composite powder was obtained after thermal decomposing oxalic acid salt precursor of Co-V-Cr powder prepared through oxalate co-precipitation method using Co, V, Cr soluble chloride and ammonium oxalate as raw materials. The decomposition process of precursor was studied by DSC and TG. The properties of composite were analyzed and characterized by SEM and BET. The results show that the particle size of Co-V-Cr composite powder is nanometer grade, well dispersing and V, Cr soluting in Co completely. The appropriate calcination temperature is 450℃. Precursor powder decompose into Co-V-Cr composite powder directly in argon atmosphere at 421℃; Whereas in air, DSC and TG curves present an exothermic peak at 366℃ indicating an oxidation reaction at this temperature, which suggests that the precursor powders first decompose into composite powder, then followed by a process of oxidation. Co-V-Cr composite powders with maximum specific area of 41.50 (m2/g) and the smallest grain size of 11~12 nm are obtained in argon atmosphere calcination. ©, 2014, Central South University. All right reserved.

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