Ti has received considerable attention for aerospace, vehicle, and semiconductor industry applications because of its acid-resistant nature, low density, and high mechanical strength. A common precursor used for preparing Ti materials is TiCl₄. To prepare high-purity TiCl₄, a process based on the removal of VOCl₃ has been widely applied. However, VOCl₃ removal by distillation and condensation is difficult because of the similar physical properties of TiCl₄ and VOCl₃. To circumvent this problem, in this study, we have developed a process for VOCl₃ removal using Cu powder and mineral oil as purifying agents. The effects of reaction time and temperature, and ratio of purifying agents on the VOCl₃ removal efficiency are investigated by chemical and structural measurements. Clear TiCl₄ is obtained after the removal of VOCl₃. Notably, complete removal of VOCl₃ is achieved with 2.0 wt% of mineral oil. Moreover, the refined TiCl₄ is used as a precursor for the synthesis of Ti powder. Ti powder is fabricated by a thermal reduction process at 1,100ºC using an H₂-Ar gas mixture. The average size of the Ti powder particles is in the range of 1-3 μm.

In this paper, the recovery and nanoparticle synthesis of Ag from low temperature co-fired ceramic (LTCC) by-products are studied. The effect of reaction behavior on Ag leaching conditions from the LTCC by-products is confirmed. The optimum leaching conditions are determined to be: 5 M HNO₃, a reaction temperature of 75°C, and a pulp density of 50 g/L at 60 min. For the selective recovery of Ag, the [Cl]/[Ag] equivalence ratio experiment is performed using added HCl; most of the Ag (more than 99%) is recovered. The XRD and MP-AES results confirm that the powder is AgCl and that impurities are at less than 1%. Ag nanoparticles are synthesized using a chemical reduction process for recycling, NaBH4 and PVP are used as reducing agents and dispersion stabilizers. UV-vis and FE-SEM results show that AgCl powder is precipitated and that Ag nanoparticles are synthesized. Ag nanoparticles of 100% Ag are obtained under the chemical reaction conditions.

There has been much interest in recycling electronic wastes in order to mitigate environmental problems and to recover the large amount of constituent metals. Silver recovery from electronic waste is extensively studied because of environmental and economic benefits and the use of silver in fabricating nanodevices. Hydrometallurgical processing is often used for silver recovery because it has the advantages of low cost and ease of control. Research on synthesis recovered silver into nanoparticles is needed for application to transistors and solar cells. In this study, silver is selectively recovered from the by-product of electrodes. Silver precursors are prepared using the dissolution characteristics of the leaching solution. In the liquid reduction process, silver nanoparticles are synthesized under various surfactant conditions and then analyzed. The purity of the recovered silver is 99.24%, and the average particle size of the silver nanoparticles is 68 nm.

Spherical fine cobalt powders were fabricated by new liquid reduction method. Commercial cobalt sufate heptahydrate was used as raw material. Also ethylene glycol was used as solvent and hydrazine-sodium hypophosphite mixture was used as reduction agent for the new liquid reduction method. A plate shaped cobalt powders with an approximately 300 nm were prepared by a traditional wet ruduction method using distilled water as solvent and hydrazine. Spherical fine cobalt powders with an average size of 1-3 μm were synthesized by a new liquid reduction method in 0.3M cobalt sulfate and 1.5M hydrazine-0.6M sodium hypophosphite mixture at 333K.

Cobalt coated tungsten carbide-cobalt composite powder has been prepared through wet chemical reduction method. The cobalt sulfate solution was converted to the cobalt chloride then the cobalt hydroxide. The tungsten carbide powders were added in to the cobalt hydroxide, the cobalt hydroxide was reduced and coated over tungsten carbide powder using hypo-phosphorous acid. Both the cobalt and the tungsten carbide phase peaks were evident in the tungsten carbide-cobalt composite powder by X-ray diffraction. The average particle size measured via scanning electron microscope, particle size analysis was around 380 nm and the thickness of coated cobalt was determined to be 30~40 nm by transmission electron microscopy.

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• Pre-treatments of initial materials for controlling synthesized TaC characteristics in the SHS process
  Jae Jin Sim, Sang Hoon Choi, Ji Hwan Park, Il Kyu Park, Jae Hong Lim, Kyoung Tae Park
  journal of Korean Powder Metallurgy Institute.2018; 25(3): 251.     CrossRef
• Spark plasma sintering of WC–Co tool materials prepared with emphasis on WC core–Co shell structure development
  Sungkyu Lee, Hyun Seon Hong, Hyo-Seob Kim, Soon-Jik Hong, Jin-Ho Yoon
  International Journal of Refractory Metals and Hard Materials.2015; 53: 41.     CrossRef