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Material Characterization and Analysis
Published in Muhammad E. Fayed, Thomas S. Skocir, Mechanical Conveyors, 2018
Muhammad E. Fayed, Thomas S. Skocir
Particle hardness is usually given by its relative position on the Mohs’ scale. Mohs hardness is based on comparative scratch hardness with various standard materials assigned a relative Mohs number. A diamond being the hardest known material is assigned a Mohs number of ten. A material with a given hardness will scratch any other material with a lower Mohs number. There are more precise methods of gauging a material’s hardness such as the Brinell or Rockwell methods. For conveying purposes, the Mohs scratch test is of sufficient accuracy. Particle hardness is used mainly in determining the abrasive index of a bulk solid. The test is done by scratching a sample with various standards. Particle hardness is also an indirect method of gauging a material’s attrition rate, which is how easily it cracks, crumbles, or breaks down.
Emerging Mirror Technologies
Published in Paul Yoder, Daniel Vukobratovich, Opto-Mechanical Systems Design, 2017
William A. Goodman, Paul R. Yoder
Silicon carbide, also known as carborundum, is a compound with equal portions of silicon and carbon atoms. It was first produced by Edward Acheson around 1893. Acheson developed an electric batch furnace to produce the material in bulk, and the Carborundum Corporation was born. Interestingly, natural crystals of silicon carbide, also known as the mineral moissanite (moys-uh-nite), were not discovered until 1904. Professor Moissan found the first samples of the mineral while exploring in California and Arizona. Some 85 years later, Kurt Nassau created moissanite gem stones. These gem stones are harder than sapphire, ruby, or emerald and register 9.25 on the Mohs hardness scale, a gemstone hardness that is second only to diamond. Moissanite gems have an index of refraction (n = 2.69) greater than diamond (n = 2.42) and 2.4 times the spectral dispersion. Mirrors made of silicon carbide are discussed in considerable detail in Section 6.5.4 of this volume.
Material Hardness and the Size Effect
Published in Yichun Zhou, Li Yang, Yongli Huang, Micro- and MacroMechanical Properties of Materials, 2013
Yichun Zhou, Li Yang, Yongli Huang
Mohs hardness measures hardness by testing a material's resistance to surface scratches. There are 10 different standards for Mohs hardness, categorized into 10 levels from soft to hard (see Table 4.4). If a material's hardness cannot be expressed using the scratch of a material level n but can only be expressed using the scratch of a material level n+1, then the hardness of the material lies between the two standard materials, ((n+1)/2). The application for Mohs hardness has expanded with time, and the numbers of standard levels have also increased. For Mohs hardness results for pure metals, see Table 4.5.
Pre-separation of low-grade collophane by an enhanced gravity separator
Published in Particulate Science and Technology, 2023
Xuebin Zhang, Youjun Tao, Yushuai Xian
Figure 6 presents the grinding fineness of the rod grinding products after grinding at different time. As shown in Figure 6, with the increase of grinding time, the increasing trend of −0.074 mm content gradually becomes slower and slower. The increasing trend of −0.045 mm content changes little at first, and grows faster after grinding for 13 min, which may theoretically has a negative impact on the enhanced gravity separation (Zhu, Tao, and Sun 2016b). Based on Mohs Hardness Scale, minerals with lower hardness, such as carbonate, are easily ground in the early stage of grinding. As the grinding time increases, the target mineral apatite is gradually dissociated from the gangue minerals. However, some other minerals with higher hardness are not easy to grind, and the apatite will be over-ground as the grinding time continues to increase, which will increase the energy consumption and affect the separation effect.
Ergonomic design and evaluation of gemstone polishing workstation
Published in International Journal of Occupational Safety and Ergonomics, 2022
Dipayan Das, Ashish Kumar Singh
Several limitations should be taken into account while considering the implications of the findings of the present study. In this study, all of the experimental trials were performed with a particular type of gemstone (sapphire, Mohs hardness number = 9). Hence, the same analysis with a different type of gemstone (due to differences in gemstone properties) may have different results. The findings cannot be generalized and should be interpreted with caution until future studies incorporate different types of gemstones. We plan to extend this research using different gemstones such as topaz (Mohs hardness number = 8), quartz (Mohs hardness number = 7), feldspar (Mohs hardness number = 6) and apatite (Mohs hardness number = 5). Further, the findings of this study were limited to the white light illumination condition. Since there is enormous variation in colour (warm to cold colours) across the many gemstone varieties, the colour contrast may have an impact on the upper limb postures and muscle recruitment patterns during polishing operation. Future work may also investigate the effect of colour contrast on the upper limb postures of gemstone polishers. In this study, some of the postural effects were found to be insignificant at a significance level of 0.05. Hence, a greater number of test subjects may be incorporated in future research for a better demonstration of the findings.
Coessential-connection by microwave plasma chemical vapor deposition: a common process towards wafer scale single crystal diamond
Published in Functional Diamond, 2022
Guoyang Shu, Bing Dai, Andrey Bolshakov, Weihua Wang, Yang Wang, Kang Liu, Jiwen Zhao, Jiecai Han, Jiaqi Zhu
While in the point of view of material science, the beautiful attribute of diamond seems to be at the bottom of its values, as it holds various of other excellent properties. The most well-known and used nature of diamond is the superhard, with the Mohs hardness of 10 and elasticity modulus of >1000 GPa. Such super large hardness makes diamond capable for cutting tools, drills [1], core of drawing die [2] and high pressure anvils [3]. Besides, diamond also has super high thermal conductivity, up to 2380 W/mK for single crystals [4] and up to 2000 W/mK for polycrystalline films and wafers [5, 6], depending on its quality. What’s more, the ultra-wide electromagnetic wave transparent window from UV to radio waves together with the high thermal conductivity and irradiation hardness make diamond very competitive candidate for the windows of high-power laser, microwave, and synchrotron radiation facilities. Large band gap (5.4 eV) together with rather high carrier mobility (>2000 cm2 V−1 s−1) qualifies diamond excellent semiconductor property, which is honored as the leader of the 3rd generation semiconductor materials for high power devices, computing chips and 5G stations, etc. Advanced applications in industry are regarded more valuable than the jewelry, the most traditional use of diamond. Praises such as “ultimate semiconductor,” “the 21st century is a century of diamond,” expressing enough prospect of this fundamental material.