Special Issue "Microwave Energy Applications"

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A special issue of Technologies (ISSN 2227-7080).

Deadline for manuscript submissions: closed (31 December 2014)

Special Issue Editor

Guest Editor
Dr. Manoj Gupta

Materials Group, Department of Mechanical Engineering, NUS, 9 Engineering Drive 1, 117576 Singapore
Website | E-Mail
Interests: microwave processing; solidification processing; powder processing; light weight materials (aluminum and magnesium); composites/nanocomposites

Special Issue Information

Dear Colleagues,

Microwave technology is an energy saving futuristic technology applicable to many diverse fields and a variety of materials. It has emerged predominantly in several fields of Materials Science and Technology due to its manifold characteristic advantages (fast reaction rates and reduced processing temperatures) over conventional techniques. The heating of a sample being volumetric and fast, the MW processing modifies the structure and microstructure (e.g. size of nanoparticles) and can thus tailor the materials to obtain desired properties. Accordingly, this Special Issue aims to publish papers in the area of microwave energy applications related to techniques (such as single mode, multimode); materials (metals, polymers, ceramics, dielectric, magnetic, bioceramics, composites, bulk and thin films); and applications (such as metal production, sintering, waste processing, etc.).

Dr. Manoj Gupta
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Keywords

  • microwaves
  • H-field
  • E-field
  • hybrid processing
  • sintering
  • melting
  • waste processing
  • metals
  • ceramics
  • polymers
  • nanoparticles
  • composites
  • minerals
  • waste processing

Published Papers (6 papers)

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Research

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Open AccessArticle Microwave-Assisted Preparation of High Entropy Alloys
Technologies 2015, 3(4), 182-197; doi:10.3390/technologies3040182
Received: 21 August 2015 / Revised: 24 September 2015 / Accepted: 25 September 2015 / Published: 7 October 2015
Cited by 3 | PDF Full-text (3775 KB) | HTML Full-text | XML Full-text
Abstract
Microwaves at the ISM (Industrial, Scientific and Medical, reserved internationally) frequency of 2450 or 5800 MHz have been used to prepare FeCoNiCuAl, FeCrNiTiAl and FeCoCrNiAl2.5 high entropy alloys by direct heating of pressed mixtures of metal powders. The aim of this work
[...] Read more.
Microwaves at the ISM (Industrial, Scientific and Medical, reserved internationally) frequency of 2450 or 5800 MHz have been used to prepare FeCoNiCuAl, FeCrNiTiAl and FeCoCrNiAl2.5 high entropy alloys by direct heating of pressed mixtures of metal powders. The aim of this work is to explore a new microwave-assisted near-net-shape technology, using a powder metallurgy approach for the preparation of high entropy alloys, able to overcome the limits of current melting technologies (defects formation) or solid state ones (time demanding). High entropy alloy compositions have been selected so as to comprise at least one ferromagnetic element and one highly reactive couple, like Ni-Al, Ti-Al, Co-Al or Fe-Al. Results show that direct microwave heating of the powder precursors occurs, and further heating generation is favored by the ignition of exothermal reactions in the load. Microwaves have been applied both for the ignition and sustaining of such reactions, showing that by the proposed technique, it is possible to control the cooling rate of the newly-synthesized high entropy alloys. Results showed also that microwave heating in predominant magnetic field regions of the microwave applicator is more effective at controlling the cooling rate. The herein proposed microwave-assisted powder metallurgy approach is suitable to retain the shape of the load imparted during forming by uniaxial pressing. The homogeneity of the prepared high entropy alloys in all cases was good, without the dendritic segregation typical of arc melting, even if some partially-unreacted powders were detected in the samples. Full article
(This article belongs to the Special Issue Microwave Energy Applications)
Open AccessArticle Microwave Absorption of Barium Borosilicate, Zinc Borate, Fe-Doped Alumino-Phosphate Glasses and Its Raw Materials
Technologies 2015, 3(2), 111-125; doi:10.3390/technologies3020111
Received: 24 December 2014 / Revised: 22 April 2015 / Accepted: 8 May 2015 / Published: 19 May 2015
Cited by 1 | PDF Full-text (3971 KB) | HTML Full-text | XML Full-text
Abstract
This study presents microwave absorption of raw materials used in barium borosilicate, Fe-doped alumina phosphate and zinc borate glass. Microwave absorption was investigated for the raw materials SiO2, Na2CO3, BaCO3, BPO4, Al(PO3)3,
[...] Read more.
This study presents microwave absorption of raw materials used in barium borosilicate, Fe-doped alumina phosphate and zinc borate glass. Microwave absorption was investigated for the raw materials SiO2, Na2CO3, BaCO3, BPO4, Al(PO3)3, Mg(PO3)2, Al(OH)3, TiO2. The study shows that SiO2 could be heated directly above 1000 °C within 30 min at 1.5 kW microwave output (MW) power and 0.8 kW MW power is necessary to initiate heating (from 260 °C). Microwave heating of material with low dielectric loss has been investigated by increasing MW power. Microwave absorption of above glass systems has also been investigated. Dielectric properties such as loss tangent of glass as a function of temperature are presented. Glass melting under direct microwave heating was demonstrated for the studied glass systems. Temperature-Microwave power-Time (T-P-t) profiles for the three glasses indicate maximum MW output power ~1 kW, 0.65 kW and ~1 kW for barium borosilicate, zinc borate glass and alumino-phosphate glass for 60 g glass melting. Full article
(This article belongs to the Special Issue Microwave Energy Applications)
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Open AccessArticle Evaluation of Calcium Fluoroaluminosilicate Based Glass Ionomer Luting Cements Processed Both by Conventional and Microwave Assisted Methods
Technologies 2015, 3(2), 58-73; doi:10.3390/technologies3020058
Received: 19 December 2014 / Revised: 7 March 2015 / Accepted: 9 March 2015 / Published: 25 March 2015
Cited by 2 | PDF Full-text (4051 KB) | HTML Full-text | XML Full-text
Abstract
Calcium fluoroaluminosilicate glasses (CAS) are used in the formulation of glass ionomer cements for dental applications. However, the cements obtained from CAS glasses were found to be radiolucent. In this study, the influence of substituting Zn, Sr and Mg for Ca of CAS
[...] Read more.
Calcium fluoroaluminosilicate glasses (CAS) are used in the formulation of glass ionomer cements for dental applications. However, the cements obtained from CAS glasses were found to be radiolucent. In this study, the influence of substituting Zn, Sr and Mg for Ca of CAS glasses was investigated with respect to the structure and setting characteristics, mechanical properties, and radiopacity of cements designed for luting applications. Three glass compositions based on substitution of Zn, Sr and Mg for Ca at 1:1 molar ratio was synthesized. They were coded as the G 021 (Ca: Zn), G 022 (Ca: Sr), G 023 (Ca: Mg). G 021 and G 022 glasses were processed by conventional melt quench route, whereas G 023 was processed by microwave melt–quench route. Each glass was then mixed with Fuji Type I GIC liquid in order to evaluate the properties of novel cements at different powder/liquid ratios. X-ray diffraction and Fourier Transform-Infrared spectroscopy analysis confirmed the structure of the processed glasses. The average particle size of the processed glass powders was within specification limits for luting applications (<15 μm). The substitution of Zn, Sr and Mg for Ca at 1:1 molar ratio increased the reactivity of the respective glasses. This has been reflected in their respective setting characteristics and mechanical properties. The optimal combination of setting time, strength and radiopacity for the cements examined here was shown by G 022 cements. The microwave melting can be utilized for processing ionomer glasses as it did not alter the structure and properties of G 023 cement. Full article
(This article belongs to the Special Issue Microwave Energy Applications)
Open AccessArticle Comparison of Grain Structure, Electrical and Magnetic Properties of BaTiO3 and Ni0.5Zn0.5Fe2O4 Ceramics Sintered Using Microwave and Conventional Techniques
Technologies 2015, 3(1), 47-57; doi:10.3390/technologies3010047
Received: 4 January 2015 / Revised: 9 March 2015 / Accepted: 10 March 2015 / Published: 17 March 2015
Cited by 1 | PDF Full-text (3658 KB) | HTML Full-text | XML Full-text
Abstract
BaTiO3 (BT) and Ni0.5Zn0.5Fe2O4 (NZF) ceramic disc specimens were prepared using commercial grade powders sintering by conventional (CV) and microwave (MW) sintering techniques. In both the sintering techniques the set sintering temperatures were in the
[...] Read more.
BaTiO3 (BT) and Ni0.5Zn0.5Fe2O4 (NZF) ceramic disc specimens were prepared using commercial grade powders sintering by conventional (CV) and microwave (MW) sintering techniques. In both the sintering techniques the set sintering temperatures were in the range of 850 °C to 1000 °C and time from 0.5 to 2 h. Structure, microstructure, dielectric, ferroelectric and magnetic properties have been compared for the as sintered BT and NZF ceramic specimens. Comparatively large grain size and higher density observed for the samples sintered at same temperature and shorter holding time using microwave. Magnetic properties of the NZF samples sintered using MW at a temperature of 950 °C show a higher saturation magnetization (Ms) value of 88 emu/g. Full article
(This article belongs to the Special Issue Microwave Energy Applications)
Open AccessArticle Application of Sonication and Microwave Irradiation to Boost Continuous Fabrication of the Copper(II) Oxide Sub-Micron Particles
Technologies 2015, 3(1), 37-46; doi:10.3390/technologies3010037
Received: 8 December 2014 / Revised: 15 February 2015 / Accepted: 16 February 2015 / Published: 5 March 2015
Cited by 2 | PDF Full-text (4312 KB) | HTML Full-text | XML Full-text
Abstract
Viability of the continuous-flow synthesis of rhomboidal copper(II) oxide (CuO) micro- and nanonoparticles was demonstrated. It has been shown that ultrasonic mixing of reactants, in the stage of Cu(OH)2 synthesis, followed by microwave irradiation of the resulting suspension, gives very fine particles
[...] Read more.
Viability of the continuous-flow synthesis of rhomboidal copper(II) oxide (CuO) micro- and nanonoparticles was demonstrated. It has been shown that ultrasonic mixing of reactants, in the stage of Cu(OH)2 synthesis, followed by microwave irradiation of the resulting suspension, gives very fine particles of CuO at high yield and within minutes. Near optimal parameters for the synthesis of fine particles in the continuous reactor were determined. Full article
(This article belongs to the Special Issue Microwave Energy Applications)

Review

Jump to: Research

Open AccessReview Using Microwave Energy to Synthesize Light Weight/Energy Saving Magnesium Based Materials: A Review
Technologies 2015, 3(1), 1-18; doi:10.3390/technologies3010001
Received: 30 September 2014 / Revised: 4 December 2014 / Accepted: 7 January 2015 / Published: 20 January 2015
Cited by 3 | PDF Full-text (6367 KB) | HTML Full-text | XML Full-text
Abstract
Microwave energy can be used for the processing of a wide variety of materials. It is used most commonly for the heating of food and has been increasingly applied for processing of polymers; ceramics; metals; minerals and composites. The use of microwave energy
[...] Read more.
Microwave energy can be used for the processing of a wide variety of materials. It is used most commonly for the heating of food and has been increasingly applied for processing of polymers; ceramics; metals; minerals and composites. The use of microwave energy allows rapid and volumetric heating where heat is generated from within the material instead of via radiative heat transfer from external heating elements. This paper aims to provide a review on the use of energy efficient and environment friendly microwave energy route to synthesize magnesium based materials reinforced with various types of metallic and ceramic reinforcements. Magnesium composites are extremely attractive for weight critical applications in automotive; aerospace; electronics and transportation sectors. The magnesium composites were prepared using blend—compact—microwave sintering—extrusion methodology. Microwave sintering allowed a significant reduction of 80% in both processing time and energy consumption over conventional sintering without any detrimental effect on the properties of the synthesized magnesium composites. Physical; microstructure and mechanical properties of microwave sintered magnesium composites will also be discussed and compared with magnesium composites processed by conventional liquid and solid processing techniques. Full article
(This article belongs to the Special Issue Microwave Energy Applications)

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