Integrated technologies and the problem of creation of large-area silicone carbide devices for high-power converters

We consider limitations typical for semiconductor devices of up-to-date converter equipment based on silicon and silicone technologies. The reasons for processing complexities in creating the hardware components of heavy-current devices based on wide-band-gap semiconductors are analyzed. Possible approach to production of large area SiC-diodes and thyristors is formulated, which at post-processing stage allows performing modification of their voltage-current characteristics (VCC) and increasing in its non-linearity coefficient. Based on the concept of integrated power devices containing mesa-elements with VCC with random parameters, the possibility of sequential automated exclusion of those single “non-standard” micro-devices to adversely impact on general voltage-current characteristics of an array is considered. Algorithm is briefly described, and computer modelling of transformation of the reverse branch of integrated VCC occurring in the course of such modification is provided, which made it possible to establish relationship between the typical probability distributions of impurity (including in the presence of dislocations) and certain features of final VCC.

Identifying the Breakdown Voltages of Vegetable Oils with Silicone Carbide Nanoparticle Additive as Insulating Oil for Transformers

This paper discusses on the breakdown voltage of vegetable oils with nanoparticles added to be used as insulating oil for transformers. Raw samples of Palm Oil (PO) and Coconut Oil (CO) were used in this research. Different percentages of silicone carbide (SiC) nanoparticles was added into the samples of the vegetable oils. The different parameters of the vegetable oil mixtures were investigated through the breakdown voltage tests to analyse the effect of the additive on the dielectric strength of the oils. The performance of insulating oils varies according to the percentage of nanoparticles added through viscosity test and partial discharge (PD) measurement. The initial results for vegetable oils showed that the percentage of additives influenced the value of breakdown voltage of the oils highly. Furthermore, the result shows that PD measured became very low after the addition of silicone carbide nanoparticles.

Effect of Finishing and Polishing on the Surface Roughness and Gloss of Feldspathic Ceramic for Chairside CAD/CAM Systems

SUMMARY Objectives: To evaluate surface roughness and gloss of feldspathic ceramic blocks for chairside CAD/CAM systems before and after finishing and polishing. Methods: VITA Mark II ceramic blocks for the CEREC CAD/CAM system were cut perpendicularly in order to obtain a total of 70 specimens (14 × 18 × 3 mm). The flat surface was roughened using a grinder/polisher with dry 120-grit silicone-carbide paper. Surface roughness and gloss were measured using a digital profilometer (Ra) and a glossmeter (GU), respectively. Specimens were randomly divided into seven groups (n=10) based on the finishing/polishing system as follows: 1) Identoflex NGPorcelain Polisher (INP), 2) Identoflex Diamond Ceramic Polisher (IDP), 3) Hiluster Polishing System (HPS), 4) OptraFine (OF), 5) Identoflex Lucent (IL), 6) VITA Akzent Glaze Spray (AGS), and 7) VITA Shading Paste and Liquid (SPL). Surface analysis was repeated after the finishing/polishing treatment, and the obtained data were compared to the baseline in order to evaluate the ΔRa and ΔGU. Results were statistically analyzed. The surface morphology was observed by scanning electron microscopy. Results: The mean surface roughness of polished systems increased in the order (statistical groups designated) SPLa < ILa < OFab < IDPbc < AGSbc < INPbc < HPSc and mean gloss decreased in the order AGSa > SPLa > OFab > ILabc > HPSbcd > INPcd > IDPd. Conclusions: The smoothest surface of CAD/CAM feldspathic ceramic blocks was achieved using the furnace-based glaze systems VITA Akzent Glaze Spray and VITA Shading Paste and Liquid and manual systems Identoflex Lucent and OptraFine.

The Effect of Metal Forming Direction on the Tribological Properties of MMCp Composites

This article presents the results of the research on tribological composites with AlCu2SiMn matrix that underwent the process of extrusion. The research was conducted on the composites that underwent extrusion, which was carried out with a pneumatic press with a heated matrix of 14mm and 20mm diameter. The research was carried out under technical dry friction conditions in reciprocating motion. The results allowed to describe the influence of the plastic work direction on the tribological properties of the composites reinforced with silicone carbide and glassy carbon. The process of wearing was conducted in two directions: the perpendicular and parallel to the axis of the extruded composite rod. In the examined composites the tribological wear in the direction perpendicular to the direction of the extrusion was greater than wear in the parallel direction. The difference between the values for the parallel and perpendicular directions to the rod decreases with the increase of the degree of plastic work.

Influence of Silicone Carbide on the Reactivity of Nuclear Fuels Using Cerium Dioxide as a Surrogate Material

The most researched material in nuclear power industry is uranium dioxide however due to strict safety and sanitary restrictions this material can be researched only in specialized research institutes and universities which have sufficient technological background. For this reason it can be suitable to find material which would show physical properties similar to UO2 but would not suffer by the strict limitations in storage and handling. In this case much more workplaces could be incorporated in the material research and the list of investigated problems could be significantly enlarged. One of the possible substitutional materials is the cerium dioxide (CeO2) which shows similar chemical and physical properties like UO2 and in some cases shows also similar neutronic properties. The laboratory research was focused on comparing of the basic neutronic properties. For the comparison of nuclear properties the JANIS software [1] was used as it contains cross section libraries of both materials. It will be shown that similarity of both materials is significant and in several cases application of cerium dioxide as alternative material is possible with sufficient accuracy. As an example of the use of CeO2, research of influence of the SiC content on the reactivity of nuclear fuels is presented in this work.