Browse Topic: Chemical processing
SiC-based power devices are favored for high-voltage and high-power applications due to their superior material properties. However, the demand for higher breakdown voltages and improved channel mobility presents significant challenges to the etching process, especially the micro-trenching effect. In this study, etching results from inductively coupled plasma (ICP) have been presents, which focused on using various SF6/O2/Ar gas ratios to eliminate micro-trenching effect. The profile analysis of micro-trench was taken by cross-sectional scanning electron microscopy (SEM). The results demonstrate that micro-trenches primarily originate from the coupling effect between ion multi-reflection from sidewalls and redeposition of etch byproducts. Based on this mechanism, we propose a quasi-Bosch process: a combined polymerization and etching step in oxygen-fluorine-rich plasma deposits polymer on exposed SiC and the mask, while removing it from the structure bottom via ion bombardment to enable etching and passivation; then alternates with a short fluorine-plasma step, which consumes sidewall polymer through ion incidence and prevents SiFxOy charge accumulation, cycle etching gradually deepens the structure without micro-trenches. Different gas ratios and etching time not only change the plasma energy distribution but also affect the temporal synchronization between etching and passivation steps. This approach reduces the special demands on ICP equipment capabilities while achieving superior trench profiles. The optimal etching conditions produced a micro-trench-free SiC structure with a vertical sidewall angle and a surface roughness of less than 1 nm. This methodology and resulting structures significantly advance the manufacturability of high-performance SiC power devices, enabling next-generation applications in electric vehicles and grid infrastructure where device yield and reliability are paramount.
This standard establishes definitions, guidelines, and requirements governing the specific material (e.g., alloy and heat treat condition) to be used for chemical process test specimens when requirements call for “the same generic class of alloy”.
Liberation of oxygen from the mineral ilmenite (FeTiO3), which may be found on the Moon, Mars, or asteroids, is inefficient due to the abundance of other minerals in the excavated regolith that are present but not needed during the chemical processing. Energy for the reduction reaction is in short supply on the lunar, Martian, and asteroid surfaces. The ilmenite should be separated from other minerals to simplify and improve the process efficiency. Lunar and planetary basaltic lavas contain ilmenite, but they consist only of 12 to 20 percent by weight.
The task of chemical process operator in the parts cleaning area is generally considered unskilled labor and in the past, little or no training had been provided or recommended. Since overhaul cleaning is a critical process step prior to visual and fluorescent penetrant inspection processes, consideration must be given to minimum levels of training for these process operators. It is the responsibility of the department supervisor to ensure that all personnel within the department are trained to acceptable level in all general aspects of health and safety and basic operating procedures. This document is intended to augment the local quality control system which will control the application and frequency of the guidelines stated within.
Microwave heating is an important process for many commercial, industrial, and household applications. Industrial microwave ovens are widely used for chemical processing, agri-food, medical products, and consumer products applications. Resonant cavities are often used to speed up chemical reactions, and have the advantages of being small and producing efficient distributions of microwave energy. These multimode cavities can be considered as batch ovens where products can be treated; alternatively, microwave tunnels with multiple waveguides can be used to provide continuous production.
A compact, lightweight heat exchanger has been designed to be fault-tolerant in the sense that a single-point leak would not cause mixing of heat-transfer fluids. This particular heat exchanger is intended to be part of the temperature-regulation system for habitable modules of the International Space Station and to function with water and ammonia as the heat-transfer fluids. The basic fault-tolerant design is adaptable to other heat-transfer fluids and heat exchangers for applications in which mixing of heat-transfer fluids would pose toxic, explosive, or other hazards: Examples could include fuel/air heat exchangers for thermal management on aircraft, process heat exchangers in the cryogenic industry, and heat exchangers used in chemical processing.
A device based on the transport of water through a membrane to a vacuum has been developed for dehumidifying a stream of air in the life-support system of a spacecraft or space suit. The device could also be adapted to terrestrial use in dehumidification of air in an air-conditioning stream or drying of air or another gas in a chemical processing stream. The design of this device is an advance in that it decreases (relative to prior designs) the weight, power consumption, and volume of the dehumidifier in the life-support system or other gas-circulation system in which the device is used. In the case of a spacecraft or space suit, the design thereby also increases safety and health margins. Although the membranes in the device must be replaced periodically and a vacuum source is essential for its operation, no other dehumidifier works as well in a spacecraft or space suit.
Network Monitor and Control (NMC) Automation Assembly (AA) is a component of the NMC software system, which is used for controlling an antenna connection in the Deep Space Network. NMC AA could also be adapted to commercial applications (e.g., chemical processing), in which human operators must monitor and control multiple equipment subsystems simultaneously in real time. NMC AA is designed to reduce costs and increase efficiency and capacity by relieving human operators of labor-intensive and error-prone routine spacecraft-tracking activities. NMC AA includes software engines that communicate between automation scripts and DSN subsystems. The automation scripts are developed in the Automation Language for Managing Operations (ALMO), which is a programming language that includes specialized constructs for interacting with the subsystems. The contents of the scripts represent knowledge of operations gathered from DSN operators and engineers. The ALMO scripts are organized in a temporal-dependency network and managed via a graphical user interface that enables a human operator to monitor and control the automation at any time.
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