Preparation and Thermal Stability of Ultrafine Nickel Powders Containing hcp-Ni Nanocrystallites Using Liquid-Phase Redu
- PDF / 1,078,259 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 11 Downloads / 208 Views
TRODUCTION
ULTRAFINE nickel powders have been studied extensively over the past decades owing to their potential technological applications in rechargeable batteries, cemented carbides, chemical catalysts, optoelectronics, magnetic recording media, and others.[1–3] Recently, attention has been increasingly focused on uniformly shaped high-purity nanometer nickel powders with the mean particle size ranging from several nanometers to 100 nm. Several methods for producing such metal powders with various sizes and shapes have been reported. Some of these are the pyrolysis of nickel carbonyl,[4] sonochemical method,[5] microemulsion technique,[6] microwave irradiation method, [7] polyol process,[8] reduction of metal salts using hydrazine,[9] and the mechanochemical method.[10] However, these methods are not appropriate for large-scale powder production due to the technical difficulty and expensive equipments involved. Chemical reduction in solution is generally suited for the preparation of nanometer powders. However, controlling the size and shape of the powders presents a challenge to this method.[11,12] Nickel has two different crystal structures, namely face-centered cubic (fcc) and hexagonal close-packed (hcp) structures. However, hcp-Ni has never been found in nature; therefore, the synthesis of hcp-Ni received a ZHIMEI XIA, Lecturer, is with the School of Metallurgical Engineering, Hunan University of Technology, Zhuzhou Hunan 412007, China. SHENGMING JIN, Associate Professor, is with the School of Minerals Processing and Bioengineering, Central South University, Changsha Hunan 410083, China. Contact e-mail: [email protected] KUN LIU, Assistant Engineer, is with the Shangyu Weili Recycle Resources Co., Ltd., Shaoxing Zhejiang 312369, China. Manuscript submitted March 25, 2016. Article published online August 4, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
great attention in the past. A few papers reported that hcp-Ni powders were prepared by the reaction with K/B alloy in an inert atmosphere,[13] inducing powder formation using a substrate or by introducing defects.[14,15] Furthermore, the nonmagnetic behavior and high thermal stability of hcp-Ni powders were also reported.[16] Here, we discuss the preparation of ultrafine nickel powders containing hcp-Ni (PDF No. 45-1027) and fcc-Ni (PDF No. 04-0850) using liquid reduction method with NiC2O4 as well as study its thermal stability in air flow.
II.
EXPERIMENTAL
The reagents used in the experiments, NiSO4Æ6H2O, (NH4)2C2O4ÆH2O, NaOH, C2H5OH, and EG, were all of analytical grade. Typically, a given amount of NiSO4Æ6H2O with 1 pct polyvinylpyrrolidone (PVP, molecular weight 10,000) was dissolved in distilled water and (NH4)2C2O4ÆH2O solution was added. The mixed solution was stirred at 333 K (60 °C) for 2 hours. Then the NiC2O4 slurry was filtered using a Buchner funnel. The NiC2O4 thus obtained and appropriate amounts of NaOH, PVP, and 100 mL EG were added into a three-necked flask. The mixture was refluxed at 453 K (180 °C) and then filtered using a Buchner funnel, wash
Data Loading...
