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Spark Erosion Machining
Published in Neelesh Kumar Jain, Kapil Gupta, Spark Erosion Machining, 2020
Mohri et al. (1996) demonstrated that using an auxiliary or assisting electrode can help in the machining of ceramics through any SEM process. They successfully diffused conductive particles from an assisting electrode to the surface of sialon ceramics or silicon nitride (Si3N4). Konig et al. (1998) characterized ceramics into non-conductors, natural conductors and conductors, and demonstrated that SEM of non-conducting ceramics can be facilitated by doping them with conductive elements. Lee et al. (1998) proved that a hybrid process enhances the circulation of the dielectric in the IEG and reduces the thickness of the white or recast layer. Sanchez et al. (2001) demonstrated the feasibility of SEM of boron carbide (B4C) and silicon-infiltrated silicon carbide (SiSiC) by combining ultrasonic vibrations with SEM. All these developments have turned SEM and SEM-based processes into competitive technologies for machining advanced ceramics.
Combustion in Porous Media for Porous Burner Application
Published in Yasser Mahmoudi, Kamel Hooman, Kambiz Vafai, Convective Heat Transfer in Porous Media, 2019
Ali (2014) studied the performance of conventional LPG cooking stove with different PM and found that the thermal efficiency could be improved by 10.71% with ball bearing as PM. In a similar study, Wu et al. (2014) demonstrated that, by using metallic PM in a conventional Bunsen flame burner, a flat flame could be stabilized while improving the operating range, turn-down ratio, and pollution emissions. Herrera et al. (2015) developed and tested a domestic LPG-fueled PM burner made with a combination of a bed of Al2O3 particles obtained from grinding residues and SiSiC (silicon-infiltrated silicon carbide) ceramic foam. Lapirattanakun and Charoensuk (2017) designed a PMB operating on wasted vegetable oil (WVO) for cooking application. The PM was made of a 2-cm diameter of spherical ceramic balls. In the proposed burner, steam was used to atomize the WVO droplets, to entrain air into the combustion zone, and to reduce soot and CO emission. The maximum achievable thermal efficiency was 42%, and the combustion efficiency was around 99.5%. Similar efforts on developing PMBs for household applications include those of Iral and Amell (2015), Laphirattanakul et al. (2016), and Pradhan et al. (2018).
State of the Art in the Die Sinking EDM Processes of Electrically Conductive Ceramics
Published in P. C. Thomas, Vishal John Mathai, Geevarghese Titus, Emerging Technologies for Sustainability, 2020
Mathew J. Joseph, M. Uthayakumar, Alvin Skaria Sajan, Amal Sajan, Arun Benny, S. Ashwin T.
Sanchez et al. [19], developed an optimum technology for the electro discharge machining of advanced ceramics with special focus on boron carbide (B4C) and silicon infiltrated silicon carbide (SiSiC). The researchers evaluated the surface roughness and removal rates for sinking and wire EDM for both of the ceramics. It was observed that, in the case of sinking EDM, the maximum removal rate was maximum if some capacitors were parallel connected between the electrode and work piece. EDM proves itself with as much competitiveness in the processing of advanced ceramics as other non-conventional machining process such as USM and laser, provided the work piece has at least a minimum electrical conductivity of 0.01 Scm-1.
Development of High Pressure–Velocity Contacting Plain Face Seals for Sealing Water
Published in Tribology Transactions, 2020
Reaction-bonded (with free silicon) silicon carbide, designated as SiSiC, has a high thermal conductivity and low friction coefficient when used as mating ring material to run against carbon in water. However, it has a lower Young’s modulus than tungsten carbide with a nickel binder (WC-Ni) and deforms more. It also has lower fracture toughness and chips more easily. This should be taken into account at the design stage, though sometimes designers prefer tungsten carbide. Carbon is the most commonly used primary ring material; an antimony-filled grade (C-Sb) was chosen for higher strengths in this application. However, under high pressure, this carbon material still reached its strength limit. The alternative primary ring material considered was graphite-loaded reaction-bonded silicon carbide (C/SiSiC). This reaction-bonded silicon carbide includes free graphite distributed throughout the volume. It has a higher Young’s modulus and strength than carbon to resist the distortion and stress from high-pressure sealing. The face rubbing contact was expected to be relieved by the graphite lubrication, and this material should perform better in occasional dry running than other silicon carbide materials when running against other hard seal face materials. Two graphite-loaded reaction-bonded silicon carbides, Grade P and Grade S, from different manufacturers were tested. The tested material combinations are shown in Table 1 and the relevant physical properties are summarized in Table 2.