Modeling of the radiation induced electromagnetic field in finely-disperse media

Algorithms for supercomputer modeling of the radiation electromagnetic field in heterogeneous materials of a complex finely-dispersed structure are constructed. A geometric model of a heterogeneous medium is created using Stilinger-Lubachevsky algorithms for multimodal structures. The model includes a system of detectors for statistical evaluation of functionals on the space of solutions of the photon-electron cascade transport equations. Algorithms for the three-dimensional approximation of the results of modeling the radiation transport in a fine-dispersed medium to an electrodynamic difference grid are developed. The approximation methods based on the technology of neural networks. The method of numerical solution of the complete system of Maxwell's equations for calculating the electromagnetic field in a fine-dispersed medium is worked out. The results of demonstration calculations of the electromagnetic field are presented. The results of the calculations show that the spatial distribution of the radiation electromagnetic field has a sharply inhomogeneous structure caused by the presence of boundaries of materials with different radiation properties.

Mineral composition and commercial application feasibility of sericite ore in Ha Tinh Province

Sericite is a silicate mineral, a finely disperse and partly hydrated variety of muscovite. It is widely applied in many areas of engineering and production, and has a high economic value. Sericite has been produced and used in the world for a few hundred years. In Vietnam, a new-discovered sericite deposit holds commercial quality reserves. This article presents the studies into the mineral composition of sericite ore from Ha Tinh deposit using a set of the modern analytical techniques, which prove efficiency of the commercial-level production and processing of this ore. The integrated studies into material constitution of Ha Tinh sericite ore show the uniform structure of sericite and insignificant content of unwanted impurities. The size of sericite particles markedly differs from the size of other minerals in the initial ore. The content of quartz gradually increases with increasing size of ore particles, while the content of sericite gradually grows with decreasing size of particles. In particularly, in very fine particles (size less than 10 μm), the content of sericite is higher than in the initial ore by 2 times and reaches 70%, while the content of quartz is 4 times less than in the initial ore. Impurities feature nonuniform distribution and occur in some mineral grains such as apatite Ca5(PO4O)3, iron oxides and binding particles of solid solutions. During ore processing, impurities can be separated to waste, and it is possible to produce a marketable product in the form of a high quality sericite powder which meets the application standards of the porcelain, ceramic, resin and other industries. Thus, Hà Tĩnh sericite ore can be converted into valued products to be used in many various industries.

Investigation & Resolution of Current Leakage Failure caused by Carbon Black Aggregation in Mold Compound

Encapsulation materials (e.g. mold compounds) are inherently designed to have very high resistivity (volume resistivity of > 1013 Ohm.cm) to avoid any current leakage or shorting of pins. However, multiple ingredients in mold compound, if processed inappropriately, have enough conductivity to cause significant leakage resulting poor yield and/or inferior quality of products. For a Molded Array Process Ball Grid Array (MAPBGA) package, high current leakage (> 1 μA) failure was observed. For standard electronic packages, the allowable leakage is in the range of two to three order of magnitude lower than the leakage observed. Significant current leakage was observed at a specific pin using a standard organic substrate. The problem persisted across multiple substrate suppliers. Electrical and failure analysis did not suggest interlayer dielectric cracking or wire bond related anomalies. Secondary factors such as mold flow direction, mold cap thickness and substrate design aggravated the current leakage issue. Curve trace was able to isolate the problem away from die, and toward package assembly. Further, strategically designed experiments successfully led to the root cause. Current leakage was caused by formation of conductive path between two pins due agglomeration of carbon black in mold compound. Thermogravimetric analysis (TGA) technique was used to characterize the moisture uptake of carbon black and to differentiate between agglomerated and finely disperse carbon black. With the material improvement (change in the carbon black pH to avoid agglomeration), the leakage mechanism was fully understood and the problem was resolved. Surface of carbon black particle was modified by further oxidation process resulting in lower pH, finely dispersed carbon black.

Graphite Nanoplatelet Modified Epoxy Resin for Carbon Fibre Reinforced Plastics with Enhanced Properties

A simple approach to deliver graphene or graphite nanoplatelets (GNPs) into carbon fibre reinforced plastic (CFRPs) to enhance the multifunctional properties of carbon/epoxy laminates was demonstrated. GNPs improved the typically low interlaminar mechanical, thermal, and electrical properties of CFRPs after direct vacuum infusion of GNP doped resin obtained via in situ exfoliation by three-roll milling (TRM). Compared to high shear mixing or probe ultrasonication, TRM produces higher shear rates and stresses to exfoliate and finely disperse GNP particles within an epoxy matrix. This environmentally friendly and industrial scalable process does not require the use of solvents, additives, or chemical treatments. The flexural modulus and interlaminar shear strength (ILSS) of CFRPs was increased by 15% and by 18%, respectively, with the addition of 5 wt.% in situ exfoliated GNP in the doped epoxy resin. Out-of-plane electrical and thermal conductivity, at the same filler content, were, respectively, improved by nearly two orders of magnitude and 50%.

Polyfunctional Anion Exchangers on the Basis of Allyl Compounds, Glyсydilic Ethers of Dioxybenzenes and Some Di- and Polyamines

Scientific basis for preparation of new carbon-mineral adsorbents, supports, highly selective catalysts, and composite materials synthesized by a carbide cycle mechanism on the finely disperse particles of the iron subgroup metals, their alloys with some other metals is discussed. It was found that the carbide cycle mechanism involves the chemical and physical steps. The regularities of the process performance on the both stages are considered. Graphite filaments may be formed of graphite layers with either coaxial-cylindrical, coaxial-conic or stack orientations in the filament body. A number of primary and secondary properties of the graphite aggregates is being discussed. We have developed the methods for control the synthesis of carbon-mineral materials of the specified properties by varying the parameters of the metal particles, the nature of hydrocarbon decomposition, and the process mode.