Production Of High-quality Materials Research Articles

Возможные направления в совершенствовании малогабаритных бытовых сушильных установок

The main problem that we have to face in agriculture is processing and storage of agricultural products. One of the most preferred processing methods is drying. The dried product is stored longer, while the requirements for storage conditions are more tolerant. Standard dryers are a sealed chamber where the dried product is located; they work in cycles: loading-drying-unloading. Such characteristics are well suited for small agricultural enterprises. Traditional drying methods, as a rule, involve large energy costs and take a long time. The development of highly efficient drying equipment is possible because of improving the technology and designs of devices that intensify heat and mass transfer, by creating combined dryers and optimal drying schemes, combining the drying process with other processes. (Research purpose) The research purpose is in considering rational methods of physically justified processes of high-intensity drying of agricultural products for the development of effective drying equipment. (Materials and methods) The description of heat and mass transfer processes allows you to choose a rational method; solve the problem of forecasting processes; determine the way to increase the efficiency of drying and equipment. (Results and discussion) The rate of moisture transfer in the material depends on the moving of moisture inside and the surface of the material to the drying agent. The value of the drying speed depends on the temperature, humidity and air speed, the dried air accelerates the drying process. (Conclusions) The magnitude and relative direction of the thermodynamic forces of moisture conductivity and thermal moisture conductivity determines the intensity of material dehydration. For a specific drying method, optimal technological modes of dehydration should be created, ensuring the production of high-quality materials. Closed-cycle devices with recirculation of the drying agent and heat energy recovery reduce the energy consumption for the process.

Electron-Beam Melting and Reuse of Metallic Materials

We study the processes and mechanisms of electron-beam melting (EBM) used in the production of high-purity metals. We formulate the requirements that should be imposed on the EBM parameters for the production of high-quality materials and proposed some optimal modes.

(Invited) 2D Semiconductors in Large-Area Flexible Opto/Electronics

Successful implementation of two-dimensional layered materials (2DLMs) in opto/electronic applications of the future would require not only the production of high quality materials in large volumes, but also the design of innovative, low power devices that can be implemented onto arbitrary substrate materials, ideally using high-throughput manufacturing paradigms. In this presentation I will discuss the development of low operating voltage 2DLMs-based opto/electronic devices using a combination of self-assembly and top-down manufacturing techniques. Particular emphasis will be placed on the use of adhesion lithography (a-Lith) for the patterning of arbitrary width sub-20 nm nanogaps formed between various dissimilar electrode materials and its combination with 2DLMs for the development of prototype large-area, nano-gap devices including co-planar Schottky diodes, photodetectors, and low-power field-effect transistors.

Towards large-scale in free-standing graphene and N-graphene sheets

One of the greatest challenges in the commercialization of graphene and derivatives is production of high quality material in bulk quantities at low price and in a reproducible manner. The very limited control, or even lack of, over the synthesis process is one of the main problems of conventional approaches. Herein, we present a microwave plasma-enabled scalable route for continuous, large-scale fabrication of free-standing graphene and nitrogen doped graphene sheets. The method’s crucial advantage relies on harnessing unique plasma mechanisms to control the material and energy fluxes of the main building units at the atomic scale. By tailoring the high energy density plasma environment and complementarily applying in situ IR and soft UV radiation, a controllable selective synthesis of high quality graphene sheets at 2 mg/min yield with prescribed structural qualities was achieved. Raman spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and Near Edge X-ray-absorption fine-structure spectroscopy were used to probe the morphological, chemical and microstructural features of the produced material. The method described here is scalable and show a potential for controllable, large-scale fabrication of other graphene derivatives and promotes microwave plasmas as a competitive, green, and cost-effective alternative to presently used chemical methods.

Review on Modeling and Simulation of Electroslag Remelting

The Electroslag Remelting (ESR) is an advanced technology for the production of high quality materials, for example, hot work tool steels or nickel base alloys. In the past years, several models are developed aiming to predict the way in which the operational parameters affect the structure and chemical composition of the final ESR ingot. Proper modeling of this process depends on the ability of the model to predict the Multiphysics resulting from the complex coupling between many physical phenomena. This review includes the main findings starting from the 1970's, with a special focus on the results obtained in the period of 1999–2017. The difficulties related to the poorly known physical properties of ESR slags are discussed. Then, the main achievements in the field of electromagnetism, fluid flow, heat transfer, and solidification are also summarized. The review finishes by presenting the special topics representing the actual scientific frontiers, such as the physics of mold current, the importance of multiphase phenomena, and the difficulties in predicting the electrode melting rate.

Production of Antigens for ELISA.

Immunologic assays such as ELISA allow detection of either virus antigens or the host's immune response to antigens associated with prior infections and offer a powerful means to approach understanding the epidemiology and epizootiology of these agents. However, the success of these assays is highly dependent on the production of high-quality materials both to establish the assays (i.e., antigen target for antibody) and to serve as controls for establishing assay parameters and sensitivity. Here we describe methods for preparing ebolavirus antigens suitable for use as either reagents or controls in a variety of ELISA formats. Considering work with filoviruses is typically restricted to maximum containment laboratories; thus, we also provide methods for inactivating and safety testing of these antigens for safe use in properly established field laboratories.

Effect of Water Gap in Delivery System on Twin Roll Strip Caster by Simulation

In continuous casting process, the mould is the core of the continuous caster, and the vast majority of the surface defects of steel is originated in the crystallizer. Choosing a reasonable water gap in the delivery system is particularly important, especially in twin roll strip continuous casting, the flow delivery system thin belt has a close relationship with the quality of the products. Experiments to skateboard and water gap, STEEL AISI 4340 materials chosen as the simulation material at the same time, distribution water gap taking the form of a set themselves by using the finite element software COMSOL simulation calculation of different gaps opening mode of velocity field, and fluid line back to the high wall, made a comprehensive analysis in different speak way open comprehensive effect is best, the most conducive to the production of high quality material. The experiment determines the best form of water gap, improving the efficiency of the actual production. Make it to the actual production has a certain guiding significance.

ChemInform Abstract: Recent Developments in Colloidal Synthesis of CuInSe2 Nanoparticles

AbstractReview: 42 refs.

Recent Developments in Colloidal Synthesis of CuInSe2 Nanoparticles

Ternary semiconductor nanocrystals, such as CuInSe2 , are of high interest for photovoltaic application due to their relatively low toxicity and unique properties. During the last decades great success has been achieved in the colloidal synthesis of binary nanoparticles, but for ternary compounds this research is still in an early stage of development. These materials are a challenge for synthetic chemistry, because the interaction between the three components (copper, indium, and selenium) plays a major role for the production of high quality material. The purpose of this Minireview is to provide a summary of the achievements in colloidal synthesis of CuInSe2 nanoparticles--in particular, details of reaction mechanism and its characterization possibilities, which might be useful also for the colloidal synthesis of other multicomponent systems.

Study of the anomalous zinc distribution in vertical Bridgman grown CdZnTe crystals

The exploitation of CdZnTe crystals for the preparation of X- and gamma-ray detectors is still limited by the low yield in the production of high quality material. Twins and grain boundaries are still present in the state of the art melt-grown crystals, due to the difficulty to implement seeding procedures. In this paper, the zinc content of several CdZnTe crystals is analyzed in detail with the purpose of studying the phenomena occurring in the first part of growth. It is found that both the obtained experimental data as well as the ones reported by several other authors cannot be explained in terms of the usually reported model, based only on the effects of supercooling. Alternative explanations that take into account the possibility of nucleation from different sites and the possible effects of zinc thermodiffusion are suggested. These observations are very important in view of implementation of new growth configurations for obtaining larger single crystal yield.

Defect identification in strained Si/SiGe heterolayers for device applications

A variety of defects in the Si/SiGe system are known to have detrimental effects on the electrical performance of metal–oxide–semiconductor field-effect transistors with strained Si channels. The ability to characterize individual defect types is therefore key for the production of high quality material. In this work we examine defects in the strained Si/SiGe system using two etching techniques and atomic force microscopy (AFM). For the first time, wavelength filtering techniques were applied to AFM images to identify non-destructively surface steps associated with misfit dislocations (MDs). Quantification of dislocation density with this method was in good agreement with results obtained from the etching techniques. The material consisted of strained Si layers on thin strain-relaxed buffers (SRBs) grown by a carbon-induced relaxation technique. Using a single etch, threading dislocations (TDs) in the strained Si layer were observed separately from those in the SRB, while pit-defects which formed in strained Si following thermal annealing could be observed and distinguished from TDs. Using a different etching technique, stacking faults (SFs) formed in supercritical thickness strained Si layers were clearly distinguished from MDs at the Si/SiGe heterointerface, enabling the density of SFs in the strained Si to be evaluated. Together with the AFM image filtering, these procedures enable a comprehensive characterization of defects in the strained Si/SiGe system. The technique is suitable for high mobility epitaxial layers, employing high Ge contents, where partially relaxed supercritical thickness layers are often necessary.

Enzymatic Modification of Hemp Fibres for Sustainable Production of High Quality Materials

SUMMARY The main focus of this paper is the influence of processing parameters in enzymatic hemp separation on the fibre quality. The effect of NaOH-, EDTA- and Soda-pre-treatment, and enzymatic treatment with Lyvelin® was determined. The results show that processing parameters from, e.g., flax treatment can not easily be transferred to hemp, since there is a different pectin structure. NaOH treatment with low concentrations has only a very limited effect on fibre quality. In opposite to results known from flax, EDTA treatment has no effect on hemp separation. More successful is fibre pre-treatment by soda even in low concentrations. In addition the soda pre-treatment improves the efficiency of the subsequent enzymatic step.

An efficient fulleride production system

A complete system for the production of the fullerides C60 and C70 is described. Emphasis is placed on efficient, continuous production of high-quality materials. Carbon soot with a content of 2–5% of a mixture of C60 and C70 is prepared from carbon rods with an arc furnace. The mixture is separated from the carbon by using a Soxhlet extractor. The C60 and C70 are separated with a chromotography column in which the solvent is cycled continuously. The separated C60 is purified by sublimation. The C70 is separated from heavier fullerides with a second chromotography procedure. Single crystals of C60 are prepared from pure C60 powder by slow sublimation. The C60 is characterized by mass spectroscopy, X-ray diffraction, and Raman and infrared spectroscopy. Typical data obtained with these techniques are shown.

The production of high-quality materials by special melting processes

The three principal methods for aerospace engine alloy melting are vacuum induction melting, vacuum ore remelting, and electroslag remelting. These processes are now mature technologies with distinct limitations on producing defect-free materials. As the mechanical design of engines has advanced, particularly in respect of criteria related to fracture mechanics, these process limits have become critical in restricting advances in material performance. This paper outlines the defect types, their origins, and their relation to melting technologies. The solutions lie in the development of new melting methods, some of which are already being developed. These new methods show great promise in solving the present problems and could possibly supplant powder technologies as preferred routes for engine forging manufacture in the future. Most of the methods involve electron beam techniques which are now held to be acceptable and routine industrial practice. The vacuum induction melting system, vacuum arc remelting technique, and electroslag remelting processes will, however, continue to produce large quantities of alloys for less-demanding uses, while the new technologies will be used only for that small market fraction requiring the ultimate in alloy performance.