scholarly journals Comprehensive Assessment of Polymeric Materials for Foundry Tooling Used in Microwave Field

2015 ◽  
Vol 60 (1) ◽  
pp. 335-339 ◽  
Author(s):  
M. Stachowicz ◽  
B. Opyd ◽  
K. Granat
Keyword(s):  
Electrical Properties ◽  
Thermal Resistance ◽  
Microwave Heating ◽  
Abrasion Resistance ◽  
Microwave Field ◽  
Evaluation Criteria ◽  
Construction Materials ◽  
Polymeric Materials ◽  
Heating Process ◽  
Effectiveness And Efficiency

AbstractThe paper presents a research on abrasion resistance of selected construction materials designed for foundry tooling applied in the innovative microwave heating process of moulding and core sands. One of the main selection criteria of the materials for foundry tooling, in particular for models, moulding boards, moulding boxes and core boxes, is their good abrasive wear resistance. Usability of the selected polymeric materials, designed for foundry tooling used in electromagnetic field, is decided also by other evaluation criteria determined in the examinations, like thermal resistance and electrical properties. Abrasion resistance of the selected materials was determined for three grades of the moulding sand matrixes. Combined analysis of the determined abrasion resistance, considering also electrical properties and thermal resistance of the foundry tooling materials, characterising their usability for microwave heating of moulding and core sands, will make possible their systemising with respect to effectiveness and efficiency of the heating process, taking under consideration durability of such foundry tooling to be used in industrial conditions.

Thermal Runaway of the BaCO3 + Fe2O3 Homogenous Mixture and Mechanical Alloys at the Microwave Heating

2013 ◽  
Vol 837 ◽  
pp. 185-189 ◽  
Author(s):  
I. Danut Savu ◽  
Sorin Vasile Savu ◽  
Gabriel Constantin Benga
Keyword(s):  
Electrical Properties ◽  
Heat Source ◽  
Microwave Heating ◽  
Structural Changes ◽  
Critical Phenomenon ◽  
Ceramic Materials ◽  
Heating Time ◽  
Thermal Runaway ◽  
Heating Process ◽  
Active System

Microwave heating represents a modern technique to sintering the composites materials. The microwaves absorbance property of the materials is depending by the electrical permittivity of the materials. Researchers showed that the ceramic materials are suitable for sintering using microwave heating. The most important advantage of that sintering procedure is the reduced sintering time and temperatures. However, during the heating process these properties are changing and a pattern of the heating process cannot be established. The penetration depth of microwaves into materials depends on the electrical properties of them, and gives rise to a heat source. The electromagnetic wave absorption is responsible for the macro and micro structural changes in the materials morphology, and consequently for their electrical properties. Thermal runaway is one phenomenon which should be avoided during the microwave processing of the materials. The microwave heating consists in direct introduction of the energy in the volume of the material. If the absorbance properties of the material are increasing with temperature, than a critical phenomenon, called thermal runaway, appears during the heating process. This paper aims to study the thermal runaway of the BaCO3 + Fe2O3 homogenous mixture and mechanical alloy in a mono-mode applicator, when the heat source is a microwave generator at 2,45 Ghz. A special mono-mode chamber has been designed with dimensions 140 x 140 x 70 mm and an active system for rotating the samples, in order to record the values of the temperature and to assure a uniform exposure of the samples to the high frequency electromagnetic field. The materials used in experiments were homogenous mixture of BaCO3 + Fe2O3 which have been milled in a planetary ball mill for 5 and 20 hours. The experimental procedure consists in establishing the levels of the temperatures during the microwave heating process when the thermal runaway appears. These experiments have been done for fixed levels of microwave injected power from 0 1250 W. Numerical simulation for different heating conditions (microwave power, heating time, position of the samples inside the chamber) has been performed in order to elaborate a predictable mathematical model for continuous microwave heating and avoiding the thermal runaway of the homogenous mixture.

Optical and Electrical Properties of Organic Conducting Polymers

2014 ◽  
Vol 8 (1) ◽  
pp. 1457-1463
Author(s):  
Salah Abdulla Hasoon
Keyword(s):  
Electrical Properties ◽  
Conjugated Polymer ◽  
Polymeric Materials ◽  
Quantum Mechanical ◽  
Optical And Electrical Properties ◽  
Electrically Conducting ◽  
Temperature Ranges ◽  
Lithium Tetrafluoroborate ◽  
Absorbance Peak ◽  
Polymerization Method

Novel electrically conducting polymeric materials are prepared in this work. Polythiophene (PT) and poly (3-Methelthiophene) (P3MT) films were prepared by electro-polymerization method using cyclic voltammetry in acetonitrile as a solvent and lithium tetrafluoroborate as the electrolyte on a gold electrode. Electrical properties of P3MT have been examined in different environments using UV-Vis absorption spectroscopy and quantum mechanical ab initio calculations, The observed absorption peaks at 314 and 415 nm, were attributed to the n-π* and π-π* transitions, respectively in the conjugated polymer chain, in contrast, the observed absorbance peak at 649 nm, is responsible for electric conduction. The temperature dependence of the conductivity can be fitted to the Arrhenius and the VTF equations in different temperature ranges.

Usefulness of Foundry Tooling Materials in Microwave Heating Process

2013 ◽  
Vol 58 (3) ◽  
pp. 919-922 ◽  
Author(s):  
K. Granat ◽  
B. Opyd ◽  
D. Nowak ◽  
M. Stachowicz ◽  
G. Jaworski
Keyword(s):  
Electromagnetic Field ◽  
Microwave Heating ◽  
Loss Factor ◽  
Perturbation Technique ◽  
Resonant Cavity ◽  
Precise Determination ◽  
Heating Process ◽  
Basic Criterion ◽  
Measurement Results ◽  
Heating Technology

Abstract The paper describes preliminary examinations on establishing usefulness criteria of foundry tooling materials in the microwave heating technology. Presented are measurement results of permittivity and loss tangent that determine behaviour of the materials in electromagnetic field. The measurements were carried-out in a waveguide resonant cavity that permits precise determination the above-mentioned parameters by perturbation technique. Examined were five different materials designed for use in foundry tooling. Determined was the loss factor that permits evaluating usefulness of materials in microwave heating technology. It was demonstrated that the selected plastics meet the basic criterion that is transparency for electromagnetic radiation.

Nitrogen and Sulfur Co-doped Fluorescent Carbon Dots for the Detection of Morin and Cell Imaging

2018 ◽  
Vol 15 (1) ◽  
pp. 47-55
Author(s):  
Xuebing Li ◽  
Haifen Yang ◽  
Ning Wang ◽  
Tijian Sun ◽  
Wei Bian ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Fluorescent Probe ◽  
Fluorescence Intensity ◽  
Carbon Dots ◽  
Cell Imaging ◽  
Water Soluble ◽  
Heating Process ◽  
X Ray ◽  
Doped Carbon Dots ◽  
Co Doped

Background: Morin has many pharmacological functions including antioxidant, anticancer, anti-inflammatory, and antibacterial effects. It is commonly used in the treatment of antiviral infection, gastropathy, coronary heart disease and hepatitis B in clinic. However, researches have shown that morin is likely to show prooxidative effects on the cells when the amount of treatment is at high dose, leading to the decrease of intracellular ATP levels and the increase of necrosis process. Therefore, it is necessary to determine the concentration of morin in biologic samples. Method: Novel water-soluble and green nitrogen and sulfur co-doped carbon dots (NSCDs) were prepared by a microwave heating process with citric acid and L-cysteine. The fluorescence spectra were collected at an excitation wavelength of 350 nm when solutions of NSCDs were mixed with various concentrations of morin. Results: The as-prepared NSCDs were characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The fluorescence intensity of NSCDs decreased significantly with the increase of morin concentration. The fluorescence intensity of NSCDs displayed a linear response to morin in the concentration 0.10-30 μM with a low detection limit of 56 nM. The proposed fluorescent probe was applied to analysis of morin in human body fluids with recoveries of 98.0-102%. Conclusion: NSCDs were prepared by a microwave heating process. The present analytical method is sensitive to morin. The quenching process between NSCDs and morin is attributed to the static quenching. In addition, the cellular toxicity on HeLa cells indicated that the as-prepared NSCDs fluorescent probe does not show obvious cytotoxicity in cell imaging. Our proposed method possibly opens up a rapid and nontoxic way for preparing heteroatom doped carbon dots with a broad application prospect.

scholarly journals Fire Resistance Behaviour of Geopolymer Concrete:An Overview

Buildings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 82
Author(s):  
Salmabanu Luhar ◽  
Demetris Nicolaides ◽  
Ismail Luhar
Keyword(s):  
Compressive Strength ◽  
Thermal Resistance ◽  
Building Materials ◽  
Elevated Temperatures ◽  
Construction Materials ◽  
Flexural Behavior ◽  
Thermal Shrinkage ◽  
Physico Chemical ◽  
The Impact ◽  
Loss Of Strength

Even though, an innovative inorganic family of geopolymer concretes are eye-catching potential building materials, it is quite essential to comprehend the fire and thermal resistance of these structural materials at a very high temperature and also when experiencing fire with a view to make certain not only the safety and security of lives and properties but also to establish them as more sustainable edifice materials for future. The experimental and field observations of degree of cracking, spalling and loss of strength within the geopolymer concretes subsequent to exposure at elevated temperature and incidences of occurrences of disastrous fires extend an indication of their resistance against such severely catastrophic conditions. The impact of heat and fire on mechanical attributes viz., mechanical-compressive strength, flexural behavior, elastic modulus; durability—thermal shrinkage; chemical stability; the impact of thermal creep on compressive strength; and microstructure properties—XRD, FTIR, NMR, SEM as well as physico-chemical modifications of geopolymer composites subsequent to their exposures at elevated temperatures is reviewed in depth. The present scientific state-of-the-art review manuscript aimed to assess the fire and thermal resistance of geopolymer concrete along with its thermo-chemistry at a towering temperature in order to introduce this novel, most modern, user and eco-benign construction materials as potentially promising, sustainable, durable, thermal and fire-resistant building materials promoting their optimal and apposite applications for construction and infrastructure industries.

scholarly journals Research on Electromagnetic Sensitivity Properties of Sodium Chloride during Microwave Heating

2020 ◽  
Vol 39 (1) ◽  
pp. 54-62
Author(s):  
Hua Chen ◽  
Junjiang Chen ◽  
Weijun Wang ◽  
Huan Lin
Keyword(s):  
Sodium Chloride ◽  
Electric Field ◽  
Water Content ◽  
Heating Rate ◽  
Microwave Heating ◽  
Resonant Cavity ◽  
Relative Dielectric Constant ◽  
Heating System ◽  
Heating Process ◽  
Heating Efficiency

AbstractThe multimode resonant cavity is the most common cavity. The material often shows on selective heating performance during the heating process due to the effect of microwave heating having a closely relationship with the electromagnetism parameters. This paper is based on finite difference time domain method (FDTD) to establish the electromagnetic-thermal model. The electromagnetic sensitivity property parameters of sodium chloride including relative dielectric constant, loss angle tangent and water content of sodium chloride is studied during the heating and drying process. The heating rate and the electric field distribution of sodium chloride, at the different water content, were simulated with the electromagnetic characteristic parameters changing. The results show that with the electromagnetic sensitivity property parameters varying, the electric field strength, heating rate and steady-state temperature of the heating material will all have a variety in the cavity. Some measures are proposed to improve the heating efficiency and ensure the stability of the microwave heating system in the industrial application.

Evaluation of a permissible roadbed thawing depth in permafrost

2021 ◽  
Vol 5 ◽  
pp. 18-22
Author(s):  
Alexandr Galkin
Keyword(s):  
Thermal Resistance ◽  
Biot Number ◽  
Seasonal Changes ◽  
Construction Materials ◽  
Thermal Conditions ◽  
Road Base ◽  
Thawing Depth ◽  
Roadway Construction ◽  
Selection Of ◽  
Purpose Of Evaluation

Roadbed thermal conditions in permafrost are subject to seasonal changes affecting roadway resilience. A roadbed thawing depth is important for road base processing, especially in permafrost. This research had the purpose of evaluation of a permissible roadbed thawing depth based on the Biot number reflecting general thermal resistance of roadbed layers. These results will contribute to understanding road bed thermal resistance and selection of roadway construction materials.

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