Materials Science Forum Vol. 1088

Abstract: In the present study, Fe-0.2C-1.2Si-10.3Mn-3.4Al-0.33V multiphase steels were prepared by two different processing including intercritical annealing and warm rolling plus heat treatment. The microstructure changes induced by working processes and their effects on mechanical properties were investigated. By establishing the yield strength contribution model of each phase, the contribution of various strengthening mechanisms to the yield strength of each phase is calculated. The calculated results suggest that warm rolling plus heat treatment process improves the grain boundary strengthening, solid solution strengthening, precipitation strengthening and dislocation strengthening of each phase, and improves the yield strength.

Abstract: With the development of the material databases’ construction, the use of machine learning methods to process data mining to discover new materials has gradually become a hot topic. The mechanical properties of Mg alloys are related to their components and processing technologies, therefore, it is possible to build prediction model between components, processing technologies and mechanical properties. In order to improve the design efficiency of Mg alloys, using machine learning methods to build a prediction model for the mechanical properties of Mg alloys is of vital importance. To achieve efficient material design, this paper proposed an improved random forest (RF) method based on the Particle Swarm Optimization (PSO) algorithm, and built a Mg alloy performance prediction model. Experiments showed that the accuracy was greatly improved compared with the original RF model, and the prediction accuracy of mechanical properties can reach more than 90%.

Abstract: Using JMatPro numerical simulation to determine the range of process parameters, the solution aging treatment of Ni30 superalloy was carried out, and the influence of different solution treatment temperatures on the microstructure and hardness of the alloy was studied. The results show that with the increase of solution temperature, the grain grows rapidly, the grain growth process conforms to Arrhenius formula, and the activation energy Q of grain growth is about 74.33kJ/mol. The maximum hardness value of the sample is 41.80HRC after solution aging treatment at 980°C.

Abstract: High purity copper and copper alloy targets are the key supporting materials for the interconnection of integrated circuits in advanced processes. In this article, the chemical composition and microstructure of Cu-0.6wt%Mn alloy were characterized by means of Glow Discharge Mass Spectrometry, Inductive Coupled Plasma Emission Spectrometer, Optical Microscope and Scanning Electron Microscope. The results show that the total impurity content for Cu-0.69wt%Mn alloy is less than 1 ppm. The three key impurities contents of Ag and Fe and Si could meet the requirement of electronic materials for integrated circuits by use of high purity raw material and appropriate melting and casting methods. Mn content at different positions along the diameter direction fluctuates slightly between 0.66~0.72 wt%, and completely distributed uniformly in the Cu matrix without any trace of aggregation. Due to the influence of raw materials and casting technology, defects such as porosity and carbon inclusion are easy to appear in as-cast microstructure. Therefore, it is necessary to develop new casting mould and casting processing to improve the quality of ingots.

Abstract: In this work, a novel integrated shield gate 4H-SiC MOSFET structure, which is mainly used to reduce the reverse recovery losses of the device, is proposed. Compared with integrating Schottky barrier diode or heterojunction diode in the device to reduce reverse recovery losses, the technology of introducing field plates in MOSFETs is more mature and economical. At the same time, the new structure studied ensures the gate oxide reliability of the 4H-SiC trench gate. According to the simulation of the electrical characteristics of the source-contacted shield gate device, the effects of multiple factors such as electric field distribution, carrier concentration, and peripheral circuit are comprehensively discussed, the phenomenon of smaller reverse recovery losses caused by the shield gate explained in detail. Compared with the conventional structure device, the peak reverse current, the peak overshoot voltage, and the reverse recovery losses for the source-contacted shield gate MOSFETs are reduced by 81.4%, 77.1%, and 65.1%, respectively.

Abstract: A comparative TCAD (Technology Computer Aided Design) simulation study of various 4H-SiC trench gate MOSFET (Metal Oxide Semiconductor Field Effect Transistor) (or U-shaped trench gate MOSFET abbreviated for UMOSFET) architectures for high voltage and high-speed switching applications is reported. The DC (Direct Current) and AC (Alternating Current) characteristics of the different trench gate structures are investigated. Particularly, compared to conventional 4H-SiC UMOSFETs, the breakdown voltage of the UMOSFET having a p-type implanted bottom shield is increased by 44%. However, due to the extra JFET (Junction Field Effect Transistor) region, the specific on resistance also increases by 6%. Furthermore, under 1000 V drain bias, the peak electric field at the bottom oxide of the shielded trench gate is below 0.3 MV/cm. In contrast, the peak electric field of conventional UMOSFETs can be as high as 8 MV/cm, which might cause reliability issues. On the other hand, when the bottom oxide thickness of the trench gate is increased, the UMOSFET exhibits 22% less total gate charge, leading to 76% and 71% shorter switching delay time, compared to conventional UMOSFETs and bottom shield UMOSFETs, respectively. As revealed by the simulation results, the UMOSFETs with the p-type implanted bottom shield or thick bottom oxide are advantageous for high voltage and high-speed power switching applications.

Abstract: Currently, mining activities are mainly focused on economic efficiency and to a less extent on environmental safety. The natural environment experiences heavy impacts from mining activities. Various mining processes during the extraction of common mineral resources cause a significant increase in dust emissions. This article considers the dust fractions of granites, migmatites, marmorized limestone, ophicalcites, jades, and charoits. We determined the particle-size composition and morphology for all of the dust samples, calculated unit cell parameters and determined particle dimensions. As a result, we established that nanosize stone dust particles can enter living organisms, and their dimensions determine the impacts on the living organisms and environmental ecosystems, including the air. This research was conducted with financial support from RFBR within the scope of research project No 19-35-90096.

Abstract: This article presents the typification of zeolite raw materials from the Khonguruu deposit (Sakha Republic (Yakutia), Russia), in order to determine the area of its practical application in preparing the field for industrial development. The types of raw materials are distinguished by the difference in cation composition: clinoptilolite-geylandite composition (Na-and Ca-differences of zeolite) and geylandite composition (Ca-difference of zeolite). A brief description of the material composition and physicochemical properties of zeolite rocks is given. The physical and mechanical properties of the zeolite of the deposit and the possibility of its use for the purpose of drinking water purification are investigated. The performed studies have shown that the natural zeolite of Na-and Ca-differences has good sorption properties and can be used as filter materials in water purification systems intended for household and drinking purposes.

Abstract: The paper considers the possibility of utilization of oil-contaminated mineral waste when obtaining products of architectural and garden ceramics, or ceramic bricks. The aim of the study was to develop compositions of a ceramic charge, using oil-contaminated soil, in the form of loam and sand, instead of a weaker, that meet the requirements of state standards for operational characteristics. Optimal compositions and physical and mechanical characteristics of the obtained ceramic materials are presented. To study the composition of technogenic raw materials and the structure of synthesized ceramic materials, X-ray phase and differential thermal methods of analysis and atomic absorption spectrometry were used. An assessment of the environmental efficiency of utilization of oil-contaminated mineral waste is given, which shows a significant decrease in the anthropogenic load on the environment when obtaining ceramic products with improved operational characteristics.