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Bulk Solids: Properties and Characterization
Published in Enrique Ortega-Rivas, Unit Operations of Particulate Solids, 2016
Particle size distribution measurement is a common method in any physical, mechanical, or chemical process because it is directly related to material behavior and/or physical properties of products. The bulk density, compressibility, and flowability of an industrial powder are highly dependent on particle size and its distribution. Segregation will take place in a free-flowing powder mixture because of the differences in particle sizes. There are many other properties of particulate systems that strongly depend on particle size, for example, activity of drugs, setting time of cement, and hiding power of pigments. Characterization of solid particles, which are in practice mostly irregular in shape, is usually done by analyzing particle size and its distribution. Other characteristic properties of the solid material may be included in the type of size measured; for example, Stoke’s diameter combines size, density, and shape all in one parameter. Quantitative measure of particle shape can be obtained indirectly by analyzing two or more types of particle size and looking at different “shape coefficients” that relate to those sizes. There are many different types of instruments available for measuring particle size distribution but most of them would fall into four general methods: sieving, microscope counting techniques, sedimentation, and stream scanning.
Granulation, Mixing, and Packing of Particles
Published in Mohamed N. Rahaman, Ceramic Processing, 2017
Both the powder characteristics and the mixing method influence the mixture quality. Powder characteristics that influence the mixture quality include the particle size distribution and volume fraction of each component in the mixture, the surface roughness, surface chemistry, and shape of the particles, the density of each component, and the state of agglomeration. The end use of a powder mixture determines the quality of mixture required. The end use imposes a scale of scrutiny or a characteristic volume on the mixture, which is defined as the smallest amount of material within which the quality of mixing is important.
Processing of Metal Matrix Composites (MMCs)
Published in Suneev Anil Bansal, Virat Khanna, Pallav Gupta, Metal Matrix Composites, 2023
In initial step of powder metallurgy, the matrix powder and reinforcement are mixed to attain uniform distribution of reinforced particles in the matrix. This mixing of powder is done by using a high-energy ball milling process, which is also known as the mechanical alloying process. In the mechanical alloying process, the powder mixture is blended by using balls made up of hard materials such as stainless steel, zirconium oxide, etc. After mechanical alloying, the powder mixture is filled in a die made up of steel or graphite for the compaction process. In the compaction process, pressure is applied to the powder for a certain period of time to form a solid sample. Further, this solid sample is kept in the furnace for the sintering process (Shirvanimoghaddam et al., 2017; Yue et al., 2017; Bhoi et al., 2020). In the sintering process, the temperature of the furnace is kept near the melting point of the matrix material. During the initial stage of heating, the development of thermal gradient in the sample and low penetration of heat lead to the formation of good interfacial bonding and an increase in matrix grain size. However, as the process progresses, this phenomenon changes and results in attainment of dense and homogenous microstructure for fabricated metal matrix composites (Bhoi et al., 2020). The schematic diagram of powder metallurgy process is shown in Figure 2.7. Powder metallurgy process is considered as better processing technique for fabrication of metal matrix composites in comparison with liquid state processing techniques. This was attributed to the ability of the powder metallurgy process to fabricate a wide range of product which has restrictions in size and composition of composite. Further, the scrap produced from this process is much less (Bhoi et al., 2020). In addition to this, the process parameters involved in different steps of powder metallurgy process are discussed as follows.
Development of hydrogen reduction method for La–Fe–Si materials from oxalate precursors
Published in Canadian Metallurgical Quarterly, 2023
Semih Ates, Oznur Karaagac, Hakan Köçkar, Sebahattin Gürmen
The graphical abstract of the process is given in Figure 1. The mixtures were put into alumina crucibles and placed in the middle of a hot zone in quartz glass that was passed through a vertical furnace (model: NaberTherm R30/250/23-B 170). The thermal treatment process was started at room temperature and continued to 650°C for 1 h under N2 (1L/min). Different reduction durations (1, 2, 3 h) at 900°C and different temperatures (700, 800, 900, 1000°C) during 2 h were studied to obtain optimum conditions. The optimisation process of reduction parameters was implemented to powder mixture which was prepared according to obtain x = 0.3 stoichiometric ratio of La1-xCexFe11.8Si1.2. After the determination of the optimum parameters, the powder mixtures of x = 0.3, 0.5, and 0.7 stoichiometric ratios were reduced with H2 (1 L/min). The powder mixture was prepared by mixing each material powder mechanically. The powder mixtures were prepared to be 12 g and added to alumina boat without any additional pressure. Also, 1 mm diameter cavities were created in the powder mixtures at regular intervals up to the bottom of the boat.
Additive manufacturing, the path to industrialisation at CSIRO
Published in Australian Journal of Mechanical Engineering, 2021
Robert Wilson, Shiqin Yan, Christian Doblin, Nazmul Alam, Daniel East, Daniel Liang, Alejandro Vargas-Uscategui, Andrew Urban, Emma Regos, Saden Zahiri, Peter C. King, Stefan Gulizia, Gary Savage, Darren Fraser, Sri Lathabai, Kishore Venkatesan, David Ritchie, Kun Yang, Ling Chen, Geoffrey de Looze
This powder conditioning technology is a solid-state process that modifies metal powder/swarf physical-chemical behaviour, such as surface modification, size distribution, and compositionally altered powder particles. The powder mixture is subjected to high mechanical impact due to collisions among the particles and particles and mill components. Using this technology, production of low-cost alloy powder from recycled powder/swarf for AM and PM is possible. Powder properties such as cold compactability, flow behaviour, bulk and tap density, etc., can be tailored to the requirements of the process.