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High-Electron-Mobility Transistors
Published in Vinod Kumar Khanna, Introductory Nanoelectronics, 2020
From growth technology viewpoint, there are two kinds of HEMTs: pseudomorphic and metamorphic. For HEMT fabrication, it is generally difficult to find two semiconductors with precisely matching lattice constants. So a thin film of the second semiconductor is deposited over the first semiconductor. Owing to its small thickness, the film stretches to cover and fit over the slightly unmatched lattice. HEMT fabricated in this way is said to be pseudomorphic HEMT or pHEMT. A material is pseudomorphic if it has the uncharacteristic crystalline form of another material instead of the form usually associated with its composition.
Metamorphic rocks
Published in W.S. MacKenzie, A.E. Adams, K.H. Brodie, Rocks and Minerals in Thin Section, 2017
W.S. MacKenzie, A.E. Adams, K.H. Brodie
Pseudomorphs are volume for volume replacement of one phase of mineral with a distinctive shape by another mineral or minerals, usually as a result of a retrograde reaction. In Figure 200 a euhedral garnet porphyroblast has been partially psudomorphed by fine grained green chlorite.
James Smithson on the Calamines: Chemical Combination in Crystals
Published in Ambix, 2018
An additional factor complicated the characterisation of some of the calamines: their crystals sometimes exhibited a phenomenon known as “pseudomorphism.” A mineral is said to be a “pseudomorph” when it assumes a shape that is characteristic of a different substance. This usually reflects the circumstances of its formation; one chemical component may have been gradually replaced by another, or the mineral compound may have formed in the shape of another body acting as a mould for it.21 Pseudomorphous crystals of carbonate of zinc can, in fact, exhibit the rhomboidal crystal forms that are commonly observed in calcite (carbonate of lime), and with the same angle measurements. After the publication of Smithson’s article it came to be understood that the crystal form proper to (non-pseudomorphous) carbonate of zinc is very similar to that of calcite, with the same shape but slightly different angle measurements.
Diagnosis of durability-related problems in concrete structures through comprehensive analysis and non-destructive testing: a case study
Published in Journal of Structural Integrity and Maintenance, 2023
Mati Ullah Shah, Muhammad Usman, Rao Arsalan Khushnood, Asad Hanif
The source of coarse aggregate in Islamabad is Margalla Hills quarries. These hills are composed of sedimentary rocks mainly limestone (Naeem et al., 2014). The limestone aggregates are non-reactive and cannot cause the ASR (Munir et al., 2018). Therefore, fine aggregate can be the possible source of reactivity. The sources of fine aggregate used in the construction of buildings in NUST are Lawrancepur and Ghazi Brotha sand quarries. The Lawrancepur sand is a little reactive and has ASR potential with ordinary Portland cement (Chaudhry et al., 1999; Jamil et al., 2012). No literature is available on the mineralogy of Ghazi Barotha sand. Therefore, the mineral composition of both sources has been determined through X-ray diffraction (XRD). The XRD pattern of both sand indicates amorphous nature from 0 to 30, indicating the presence of reactive silica as shown in Figures 9 and 10. However, in the case of Ghazi Barotha sand, the amorphous behavior is a little more prominent compared to Lawrencpur sand. Furthermore, there is the presence of chlorite-serpentine in Ghazi Barotha sand which indicates that it is alkali-silica reactive sand because chlorite-serpentine is a pseudomorph which means “false form” (Pascual et al., 2011). Pseudomorph minerals can easily replace their original mineral keeping the dimension and appearance constant. Thus, it is verified that both sands have ASR potential, but Ghazi Barotha sand is a little more reactive compared to Lawrencepur sand. Therefore, these aggregates can trigger the ASR with ordinary Portland cement. These XRD results complement the claim that map cracking is manifested due to the ASR.