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Fabrication of Skutterudites
Published in Ctirad Uher, Thermoelectric Skutterudites, 2021
Ball milling, also known as mechanical alloying, is a versatile fabrication process used with many thermoelectric materials and beyond. The high energy generated in ball milling is usually sufficient to form the desired phase. Unfortunately, ball milling does not directly fuse elemental powders into the skutterudite phase, even after prolonged ball milling times of 50 h, as was found early on by Yang et al. (2004, 2006). However, the fine grained (submicron size) powders can be consolidated by hot pressing or SPS, and it is during this stage of the process that the skutterudite phase forms (Jie et al. 2013). Because the ball milled powders are very fine, great care must be exercised to prevent their exposure to air, otherwise significant oxidation takes place. Moreover, the powders are also often “dirtied” by the contact with the walls of the vessel and the milling balls.
Preparation of Thermoelectric Materials by Mechanical Alloying
Published in D.M. Rowe, CRC Handbook of Thermoelectrics, 2018
B. A. Cook, J. L. Harringa, S. H. Han
Cu-Dy2S3 compounds have been examined as thermoelectric materials because of their high melting points (~1500°C) and low thermal conductivities (—20 mW/cm-°C). In these systems, copper is a dopant and dysprosium sesquisulfide is the host material. Therefore, the carrier concentration varies with the amount of Cu. Mechanical alloying is a reliable process to prepare alloys in which the two components have widely different melting points. This is especially true of the Cu-Dy2S3 system. When copper is added to Dy2Sj as a dopant by the melting technique, it is very difficult to maintain the nominal composition because at the melting point of Dy2S3 (1775°C) the vapor pressure of copper exceeds 5 mm. However, since MA is a solid-state diffusion process, material loss by vaporization is negligible. In addition, MA can also produce the metastable high temperature or the metastable high pressure y-rare earth sesquisulfide compounds.'9,20
Synthesis and Characterization of Copper–Ruthenium Composites
Published in Ajay Kumar Mishra, Lallan Mishra, Ruthenium Chemistry, 2018
Rasidi Sule, Iakovos Sigalas, Joseph Kwaku Ofori Asante, Peter Apata Olubambi
Another method of producing metal/ruthenium powder is the mechanical alloying process. Mechanical alloying process has been widely employed in the production of composite metal powders with controlled fine microstructure (Tjong and Ma, 2000; Murty and Ranganathan, 2013). In mechanical alloying, elemental powders were milled under controlled atmosphere using attrition, planetary and centrifugal. Among these mechanical alloying process, attrition ball mill has been widely used because it is simple to operate and very effective in powder particles reduction. In an attrition mill, the elemental powders are repeatedly cold welded, fractured, and re-welded leading to mechanical alloying (Suryanarayana, 2001). However, it is critical to establish a balance between fracturing and cold welding in order to achieve and homogeneous alloyed powder.
Pressureless manufacturing of Cr2AlC compound and the temperature effect
Published in Materials and Manufacturing Processes, 2021
Qui Thanh Hoai Ta, Nghe My Tran, Jin-Seo Noh
Cr2AlC compounds were synthesized from elemental powders, following the route shown in Fig. 1. For this, a 36.6 g of elemental powders were mixed in the molar ratio of Cr:Al:C = 2:1.2:1, and ball-milled using a two-axis programmable ball mill (Daihan BML-2). Here, the ball milling might be considered a mechanical alloying process. The powder mixture was loaded in a zirconia jar (capacity = 500 mL), and two sets of zirconia balls with different sizes (2 mm and 10 mm) were employed to mill the powder. Here, ball to powder weight ratio was set at 30:1, and ethyl alcohol was also added to relieve the heat generation. After 24 h of ball milling at 400 rpm, ethyl alcohol was completely removed by evaporation in the oven at 60°C. Then, the ball-milled powder was packed into a cylinder-shaped stainless steel mold (diameter = 12 mm), and a pressure of 35 MPa was applied for 10 min for densification. Next, the compact lump was loaded in an alumina crucible with cover, and the crucible was placed in a tube furnace (STF-803, 3.3 KW, LABHOUSE). Subsequently, the furnace was heated at the rate of 4°C/min under argon (Ar) atmosphere. The sintering temperature was controlled from 1000°C to 1400°C with an interval of 100°C, and the sintering time was fixed at 2 h. At the last step, the sintered sample was cooled down to room temperature, then grinded using a pestle and a mortar.
Tribological Properties of FeS-Cu Copper-Based Self-Lubricating Bearing Materials Prepared by Mechanical Alloying
Published in Tribology Transactions, 2020
Kai-Yuan Zhang, Yan-Guo Yin, Guo-Tao Zhang, Shu-Guang Ding, Qi Chen
Therefore, in this article, a mechanical alloying method was used to eliminate the agglomeration and improve the interface bonding quality of the material to more evenly distribute FeS particles in the matrix. Mechanical alloying is a high-energy ball milling technology that is widely used in the preparation of dispersion-strengthened high-temperature alloys, intermetallic compounds, amorphous alloys, nanomaterials, and supersaturated solid solutions (Dai, et al. (15); Tian, et al. (16); Karslioglu, et al. (17)). However, research on the preparation of metal–non-metal self-lubricating composites by mechanical alloying technology is scarce at present (Tu, et al. (18); Kennedy, et al. (19)). In this article, the alloy CuSn8Ni1 was chosen as the matrix material, FeS was added as the solid lubricant, and the lead-free FeS-Cu copper matrix composite was prepared by mechanical alloying. The FeS content in the formulation was optimized to 6 wt% to prepare lead-free FeS-Cu copper matrix composites according to the preliminary test results of the research group (Yin, et al. (20)). The physical and mechanical properties of the material under different ball milling times were investigated. The tribological properties of the material under dry friction conditions were analyzed, with the purpose of improving the antifriction and antiwear properties of the material to provide a reference for the development of new environmentally friendly copper-based self-lubricating composites with high performance.
A review of processing techniques for graphene-reinforced metal matrix composites
Published in Materials and Manufacturing Processes, 2019
Abqaat Naseer, Faiz Ahmad, Muhammad Aslam, Beh Hoe Guan, Wan Sharuzi Wan Harun, Norhamidi Muhamad, Muhammad Rafi Raza, Randall M German
Mechanical alloying as a simple and conventional route for powder processing is among the most widely used solid state powder processing technique employed for fabrication of graphene reinforced metal matrix composites.[88–95] A general representation of the mechanical alloying process has been depicted in Fig. 2. Ball milling is the major dispersion and blending technique used for mechanical alloying and it is carried out not only to blend the metallic particles along with the reinforcement but also to control the morphology of the processed powders.[97] The repeated cycles of cold welding, particle fracture, and rewelding of metallic powders during ball milling control the distribution of graphene and its interfacial interaction with the matrix.[73]