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Manufacturing Techniques
Published in Sumit Sharma, Composite Materials, 2021
During CVD, flowing gas-phase materials react on the surface of a hot solid material (substrate) and solid reaction products deposit on the surface of the substrate. Three major processes have been used: (1) reduction of metal halides by hydrogen with a catalyst, (2) thermal decomposition of gas phases, and (3) the reaction of the substrate with gas phases. The deposition rate or crystallization rate mainly depends on the temperature of the substrate. Therefore, the microstructure of the deposited layer also depends on the substrate temperature. Generally, at high temperature, several kinds of single crystals grow, and at lower temperature, polycrystalline or amorphous phases grow. Fine polycrystalline deposits having dense and homogeneous mechanical properties are desirable for coating purposes. An example of the apparatus for this process, which has a heating system around the furnace inner wall, is shown in Figure 3.36. This equipment is suitable for coating of many small substrates at the same time and is called a “hot wall-type” apparatus. Alternatively, when high-frequency induction heating is used, the furnace wall is not hot; this is the “cold wall type” of apparatus.
M
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
metal 2 the second layer applied in a fabrication process. In general the nth layer of the fabrication process is called metal n. metal halide molecule formed by the reaction of metals and halogen atoms. metal-electrode semiconductor field-effect transistor (MESFET) a specific type of FET that is the dominant active (amplifying) device in GaAs MMICs. An FET is composed of three terminals called the gate, drain, and source, and a conducting "channel." In an amplifier application, the source is connected to ground, and DC bias is applied between the drain and source causing a current to flow in the channel. The current flow is controlled and "modulated" by the AC or DC voltage applied to the gate. metal-insulator-metal (MIM) capacitor a capacitor, which has a thin insulator layer between two metal electrodes. Generally, this capacitor is fabricated in semiconductor process, and this insulator layer provides high capacitance. Two extreme behaviors of a capacitor are that it will act as an open circuit to low frequencies or DC (zero frequency), and as a short frequency at a sufficiently high frequency (how high is determined by the capacitor value). Also called a thin film capacitor. metal-organic chemical vapor deposition (MOCVD or OMCVD) a material growth technique that uses metal organic molecules in an atmospheric or low pressure growth chamber and a controlled chemical reaction on a heated substrate to grow a variety of II-VI, III-V, and group IV materials with atomic layer control. Used to create material structures for a variety of electronic and
Light Sources
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
Metal-halide lamps are high-pressure mercury lamps with added metal halides to improve the luminous efficiency and color rendering. As the excitation energy of the additive metals (about 4 eV) is lower than that of mercury (7.8 eV), the metal halides can produce a substantial amount of light and thus alter the emitted spectrum. The emission spectrum can be modified by varying the halide composition: for example, line spectra can be obtained by introducing sodium, scandium, thallium, indium, cesium, and rare-earth iodides, whereas tin or tin–sodium halides (iodides with addition of bromides and chlorides) produce more continuous spectra. The luminous efficiency is 70–110 lm/W, depending on the wattage (from 20 to 18,000 W) and additive metals used. CRIs are typically above 60 and may reach 95 for some rare-earth compounds. A 400 W fluorescent triphosphor lamp at an operation temperature of 4100 K provides a luminous flux of 2850 lm, luminous efficiency of 84 lm/W, and CRI Ra = 78 [5]. The lifetime is 2,000–30,000 h. HID lamps are typically used when high light levels over large areas are required. Since metal-halide lamps produce well-balanced white light with high brightness, they are widely used in indoor lighting of high buildings, parking lots, shops, roadways, and sport terrains.
Zwitterionic π-coordination compounds of copper(I) with monosubstituted alkynes: synthesis, crystal and electronic structure of two copper(I) halide π-complexes with 4-amino-1-propargylpyridinium
Published in Journal of Coordination Chemistry, 2021
G. V. Noshchenko, B. M. Mykhalichko, V. V. Kinzhybalo
Copper(I) halides are known to be practically insoluble in water and alcohols, but soluble in concentrated aqueous or aqueous-alcohol solutions of ammonium halides, alkali metal halides or organic amine halides. The characteristic feature of these concentrated solutions is the formation of a large variety of polynuclear [CumCln](n–m)– complexes [37]. In the course of the interaction of alkynes with the concentrated solutions (e.g. under conditions of the Nieuwland’s oligomerization of acetylene), alkyne molecules form π-metalorganic compounds with these [CumCln](n–m)– anions. In our case, the appBr compound plays the role of both an ammonium halide (to increase the solubility of CuX) and an alkyne (to π-coordinate to a metal center of [CumCln](n–m)–).
Selective Extraction of Scandium by a Long Alkyl Chain Carboxylic Acid/Organophosphonic Ester Binary Extractant
Published in Solvent Extraction and Ion Exchange, 2018
Maha Sharaf, Wataru Yoshida, Fukiko Kubota, Masahiro Goto
Scandium (Sc) is a rare earth element (REE), and it is found in the same ore as lanthanides. Compared with lanthanides, Sc has a smaller ionic radius and forms more stable complexes.[1] Sc has important uses in high-technology industries. For example, it is used in alloys[2] and metal halide lamps. Sc occurs in low concentrations in deposits, although it is produced as a by-product in many effluents from tailing and industrial processes. The applications of Sc are increasing, requiring alternative techniques for Sc separation to fulfill the demand.