Search results

Filters

  • Journals
  • Date

Search results

Number of results: 13
items per page: 25 50 75
Sort by:

Abstract

Polychlorinated biphenyls (PCBs) are one group of persistent organic pollutants (POPs) that are of international concern because of global distribution, persistence, and toxicity. Removal of these compounds from the environment remains a very difficult challenge because the compounds are highly hydrophobic and have very low solubility in water. A 900 W domestic microwave oven, pyrex vessel reactor, pyrex tube connector and condensing system were used in this experiment. Radiation was discontinuous and ray powers were 540, 720 and 900 W. The PCBS were analyzed by GC-ECD. The application of microwave radiation and H2O2/TiO2 agents for the degradation of polychlorinated biphenyl contaminated oil was explored in this study. PCB – contaminated oil was treated in a pyrex reactor by microwave irradiation at 2450 MHz with the addition of H2O2/TiO2. A novel grain TiO2 (GT01) was used. The determination of PCB residues in oil by gas chromatography (GC) revealed that rates of PCB decomposition were highly dependent on microwave power, exposure time, ratio to solvent with transformer oil in 3:1, the optimal amount of GT01 (0.2 g) and 0.116 mol of H2O2 were used in the study. It was suggested that microwave irradiation with the assistance of H2O2/TiO2 might be a potential technology for the degradation of PCB – contaminated oil. The experiments show that MW irradiation, H2O2 oxidant and TiO2 catalyst lead to a degradation efficiency of PCBs only in the presence of ethanol. The results showed that the addition of ethanol significantly enhanced degradation efficiency of PCBs.
Go to article

Abstract

The article takes into consideration the researches concerning inserting the Glassex additive to the microwaved-hardened and selfhardened moulding sands with water glass. In the research different types of ester hardeners to self-hardened moulding sands with water glass were used. The influence of Glassex additive on retained strength of moulding sands with different hardeners and prepared by different technologies of hardening were tested. The influence of different hardeners and the technology of hardening on retained strength of moulding sand with water glass and the Glassex additive were also estimated.
Go to article

Abstract

A method for manufacturing of Al-Si alloy (EN AC-44200) matrix composite materials reinforced with MAX type phases in Ti-Al-C systems was developed. The MAX phases were synthesized using the Self-propagating High-Temperature Synthesis (SHS) method in its microwave assisted mode to allow Ti2AlC and Ti3AlC2 to be created in the form of spatial structures with open porosity. Obtained structures were subjected to the squeeze casting infiltration in order to create a composite material. Microstructures of the produced materials were observed by the means of optical and SEM microscopies. The applied infiltration process allows forming of homogeneous materials with a negligible residual porosity. The obtained composite materials possess no visible defects or discontinuities in the structure, which could fundamentally deteriorate their performance and mechanical properties. The produced composites, together with the reference sample of a sole matrix material, were subjected to mechanical properties tests: nanohardness or hardness (HV) and instrumental modulus of longitudinal elasticity (EIT).
Go to article

Abstract

We fabricated two different kinds of composite materials for absorbing microwave in a frequency range of 2 to 18 GHz using coaxial airline and thru-reflect-line (TRL) method. The composite materials having carbon nanotube (CNT) with carbonyl iron (CI) or iron oxide (Fe3O4) were fabricated by mixing each components. Magnetic properties were measured by SQUID equipment. Complex permittivity and complex permeability were also obtained by measuring S-parameters of the toroidal specimen dispersing CI/CNT and Fe3O4/CNT into the 50 weight percent (wt%) epoxy resin. The real permittivity was improved by mixing the CNT however, the real permeability was same as pure magnetic powders. The CI/CNT had a maximum value of real permittivity and real permeability, 11 and 1.4 at 10 GHz, respectively. The CNT composites can be adapted to the radar absorbing materials, band width 8-12 GHz.
Go to article

Abstract

The organo-inorganic commercial binder Albertine F/1 (Hüttenes-Albertus) constituting the starch-aluminosilicate mixture was directed to structural studies. The paper presents a detailed structural analysis of the binder before and after exposure to physical curing agents (microwaves, high temperature) based on the results of infrared spectroscopy studies (FTIR). An analysis of structural changes taking place in the binder system with the quartz matrix was also carried out. Based on the course of the obtained IR spectra, it was found that during the exposure on physical agents there are structural changes within the hydroxyl groups in the polymeric starch chains and silanol groups derived from aluminosilicate as well as in the quartz matrix (SiO2). The curing of the molding sand takes place due to the evaporation of the solvent water and the formation of intramolecular and intermolecular cross-linking hydrogen bonds. Type and amount of hydrogen bonds presence in cured molding sand have an impact on selected properties of molding sand. Results indicates that for molding sand with Albertine F/1 during conventional heating a more extensive network of hydrogen bonds is created.
Go to article

Abstract

The effects of silica additive (Poraver) on selected properties of BioCo3 binder in form of an aqueous poly(sodium acrylate) and dextrin (PAANa/D) binder were determined. Based on the results of the thermoanalytical studies (TG-DTG, FTIR, Py-GC/MS), it was found that the silica additive results in the increase of the thermostability of the BioCo3 binder and its contribution does not affect the increase in the level of emissions of organic destruction products. Compounds from group of aromatic hydrocarbons are only generated in the third set temperature range (420-838°C). The addition of silicate into the moulding sand with BioCo3 causes also the formation of a hydrogen bonds network with its share in the microwave radiation field and they are mainly responsible for maintaining the cross-linked structures in the mineral matrix system. As a consequence, the microwave curing process in the presence of Poraver leads to improved strength properties of the moulding sand (���� �� ). The addition of Poraver's silica to moulding sand did not alter the permeability of the moulding sand samples, and consequently reduced their friability. Microstructure investigations (SEM) of microwave-cured samples have confirmed that heterogeneous sand grains are bonded to one another through a binder film (bridges).
Go to article

Abstract

This publication describes research on the course of the process of cross-linking new BioCo polymer binders - in the form of water-based polymer compositions of poly(acrylic acid) or poly(sodium acrylate)/modified polysaccharide - using selected physical and chemical factors. It has been shown that the type of cross-linking factor used influences the strength parameters of the moulding sand. The crosslinking factors selected during basic research make it possible to obtain sand strengths similar to those of samples of sands bonded with commercial binders. Microwave radiation turned out to be the most effective cross-linking factor in a binder-matrix system. It was proven that adsorption in the microwave radiation field leads to the formation of polymer lattices with hydrogen bonds which play a major role in maintaining the formed cross-linked structures in the binder-matrix system. As a result, the process improves the strength parameters of the sand, whereas the hardening process in a microwave field significantly shortens the setting time.
Go to article

Abstract

Microwave sintering process was employed to agglomerate ferromanganese alloy powders. The effects of sintering temperature, holding time and particle size composition on the properties and microstructure of sintering products were investigated. The results was shown that increasing sintering temperature or holding time appropriately is beneficial to increase the compressive strength and volume density. SEM and EDAX analysis shows that the liquid phase formed below the melting point in the sintering process, which leads to densification. XRD patterns indicate that the main reaction during microwave sintering is the decarbonization and carburization of iron carbide phase. The experiment demonstrate that the optimum microwave sintering process condition is 1150°C, 10 min and 50% content of the powders with the size of –75 μm
Go to article

Abstract

The paper presents results of initial research on the possibility of applying microwave radiation in an innovative process of making casting moulds from silica sand, where gypsum CaSO4∙2H2O was acting as a binding material. In the research were compared strengths and technological properties of moulding mixture subjected to: natural bonding process at ambient temperature or natural curing with additional microwave drying or heating with the use of microwaves immediately after samples were formed. Used in the research moulding sands, in which dry constituents i.e. sand matrix and gypsum were mixed in the ratio: 89/11. On the basis of the results of strength tests which were obtained by various curing methods, beneficial effect of using microwaves at 2.45 GHz for drying up was observed after 1, 2 and 5 hours since moisture sandmix was formed. Applying the microwaves for hardening just after forming the samples guarantees satisfactory results in the obtained mechanical parameters. In addition, it has been noted that, from a technological and economic point of view, drying the silica sand with gypsum binder in microwave field can be an alternative to traditional molding sand technologies.
Go to article

Abstract

In recent years, an increasing interest in sandmixes containing inorganic binders has been observed. These binders, including water-glass, are harmless for the environment, neutral for humans, and relatively cheap. In spite of numerous advantages, their wide application is restricted by poor knock-out properties and problems related to rebonding. Therefore, numerous researches aimed at eliminating the disadvantages of water-glass binders are directed, among others, to modifying the structure of hydrated sodium silicate or to applying new hardening techniques. An innovative method of rapid hardening by microwave heating, permitting the restriction of the quantity of binder used and thus improving knock-out properties, meets the expectations of present-day foundries. In this paper, available information is compiled on microwave hardening of water-glass containing sandmixes; furthermore, the costs of practical application of this technology are evaluated on the grounds of the authors' own research.
Go to article

This page uses 'cookies'. Learn more