Special Issue "Inorganic Syntheses Assisted by Microwave Heating"

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A special issue of Inorganics (ISSN 2304-6740).

Deadline for manuscript submissions: closed (30 May 2014)

Special Issue Editors

Guest Editor
Prof. Dr. Cristina Leonelli (Website)

Dipartimento di Ingegneria "Enzo Ferrari", Universita' degli Studi di Modena e Reggio Emilia, Via P. Vivarelli, 10, 41125 Modena, Italy
Phone: +390592056247
Interests: microwave assisted synthesis; hydrothermal synthesis; combustion synthesis; nanoparticles preparations; electrophoretic deposition; materials chemistry; geopolymers and glasses from inorganic wastes
Guest Editor
Prof. Dr. Sridhar Komarneni (Website)

College of Agricultural Sciences,The Pennsylvania State University, PA 16802, USA
Interests: Crystal chemistry of clays and zeolites; chemistry of hydrous metal oxides in relation to cation separations and purification; water sorption and desorption, nuclear and hazardous waste disposal; kinetics and thermodynamics of cation exchange processes in minerals; Low temperature nanophase and nanocomposite materials; sol-gel chemistry of high-performance ceramics; hydrothermal and microwave-hydrothermal processing; new materials preparation and characterization

Special Issue Information

Dear Colleagues,

Microwave irradiation has been used for many years to accelerate chemical reactions. Nevertheless, over the years a more complex view has emerged because of detailed work by many researchers, primarily in the field of organic chemistry. Inorganic chemists have exploited the advantages of microwave heating not only for its accelerated temperature ramp up, but also for shortening reaction times which could lead to metastable phases or high purity products. The most investigated preparation procedure is, undoubtedly, the solvothermal and hydrothermal synthesis of powders where a drastic reduction of treatment time, from hours to minutes, have been clearly shown. The effects of microwave irradiation on the different crystal morphologies and sizes and crystallinity have been thoroughly investigated but challenges still remain, for example, in the preparation of mixed oxides, hydrated minerals, and many others. The second most investigated area is in the field of nanoparticle preparation, where homogeneous growth rate may occur. In this regard, we should also consider the selective heating of microemulsions where microwaves have played a unique role. Again speaking of nanoparticles, some of the most known preparation techniques are based on ignition by plasma torches ignited and sustained by microwaves. This particular synthetic approach has not yet been applied to all classes of compounds. Of great importance are also all the solid state reactions which are favoured by microwaves especially when low thermal conductive pellets are used. In these cases, diffusion studies are still at their beginning. Also sol–gel preparation of novel compounds can be greatly improved by the volumetric heating which is typical of microwave irradiation. At the end of the list, but not in terms of their importance, are the combustion syntheses which could take advantage of the microwave electromagnetic energy even though they are amongst the most exothermic reactions. The prolongation of a combustion until the consumption of the reactant is possible only under microwaves where combustion temperatures could be prolonged with significant effects on the final morphology of the products.

Microwave apparatuses and reactors with temperature and pressure monitoring devices have been under development in recent years, although several commercial outfits are actively supplying such equipment. The combination of different techniques being the most advanced trends: the combination of microwave irradiation with UV light or ultrasound stimulation, and pressure and laser excitations are just a few of the possibilities. These combinations represent a unique possibility to realize extreme environments with non- expensive devices which are not yet well known to the general synthesis community. Furthermore, the new developments in flow reactors with the advent of microreactors make microwaves even more interesting as a clean and sustainable heating source.

This special issue would deal with the state of the art in inorganic syntheses under microwave irradiation, and welcomes comprehensive reviews and research articles to bring out the widest information available to date, in all of the above areas and beyond; the primary requisite being a basic understanding of the heating mechanism and a complete monitoring of the reaction parameters.

Prof. Dr. Cristina Leonelli
Prof. Dr. Sridhar Komarneni
Guest Editors

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.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Inorganics is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 300 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

Keywords

  • microwave
  • dielectric heating
  • microwave reactors
  • microwave ignition
  • microwave plasma
  • microwave-hydrothermal syntheses
  • microwave-ultrasonic combined syntheses

Published Papers (7 papers)

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Editorial

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Open AccessEditorial Inorganic Syntheses Assisted by Microwave Heating
Inorganics 2015, 3(4), 388-391; doi:10.3390/inorganics3040388
Received: 28 August 2015 / Accepted: 13 October 2015 / Published: 16 October 2015
PDF Full-text (634 KB) | HTML Full-text | XML Full-text
Abstract This Special Issue on “Inorganic Syntheses Assisted by Microwave Heating” represents one of the few fully dedicated issues on inorganic microwave synthesis published by any international scientific journal and it features five papers and one review article. [...] Full article
(This article belongs to the Special Issue Inorganic Syntheses Assisted by Microwave Heating)

Research

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Open AccessArticle Microwave-Assisted Routes for the Synthesis of Complex Functional Oxides
Inorganics 2015, 3(2), 101-117; doi:10.3390/inorganics3020101
Received: 26 February 2015 / Revised: 24 April 2015 / Accepted: 29 April 2015 / Published: 12 May 2015
Cited by 6 | PDF Full-text (19951 KB) | HTML Full-text | XML Full-text
Abstract
The synthesis of complex functional inorganic materials, such as oxides, can be successfully performed by using microwave irradiation as the source of heat. To achieve this, different routes and set-ups can be used: microwave-assisted synthesis may proceed in the solid state or [...] Read more.
The synthesis of complex functional inorganic materials, such as oxides, can be successfully performed by using microwave irradiation as the source of heat. To achieve this, different routes and set-ups can be used: microwave-assisted synthesis may proceed in the solid state or in solution, aqueous or not, and the set ups may be as simple and accessible as domestic oven or quite sophisticated laboratory equipment. An obvious advantage of this innovative methodology is the considerable reduction in time—minutes rather than hours or days—and, as a consequence, energy saving. No less important is the fact that the particle growth is inhibited and the broad variety of different microwave or microwave-assisted synthesis techniques opens up opportunities for the preparation of inorganic nanoparticles and nanostructures. In this work, various microwave synthesis techniques have been employed: solid-state microwaves, single-mode microwaves using a TE10p cavity and microwave-assisted hydrothermal synthesis. Relevant examples are presented and discussed. Full article
(This article belongs to the Special Issue Inorganic Syntheses Assisted by Microwave Heating)
Open AccessArticle High-Energy-Low-Temperature Technologies for the Synthesis of Nanoparticles: Microwaves and High Pressure
Inorganics 2014, 2(4), 606-619; doi:10.3390/inorganics2040606
Received: 31 May 2014 / Revised: 14 October 2014 / Accepted: 15 October 2014 / Published: 6 November 2014
Cited by 2 | PDF Full-text (20992 KB) | HTML Full-text | XML Full-text
Abstract
Microwave Solvothermal Synthesis (MSS) is a chemical technology, where apart from possible effects of microwaves on the chemical reaction paths, microwave heating allows the precise planning of a time-temperature schedule, as well as to achieve high super-saturation of the reagents uniformly in [...] Read more.
Microwave Solvothermal Synthesis (MSS) is a chemical technology, where apart from possible effects of microwaves on the chemical reaction paths, microwave heating allows the precise planning of a time-temperature schedule, as well as to achieve high super-saturation of the reagents uniformly in the reactor vessel. Thus, MSS is suitable for production of nanoparticles with small grain size distribution and a high degree of crystallinity. A further advantage of the technology is a much lower synthesis temperature than for gas phase, plasma or sol-gel technologies. New reactors have been developed to exploit these advantages of the MSS technology of nanoparticles synthesis and to scale up the production rate. Reactor design and realization has been shown to be decisive and critical for the control of the MSS technology. Examples of oxidic and phosphatic nanoparticles synthesis have been reported. Full article
(This article belongs to the Special Issue Inorganic Syntheses Assisted by Microwave Heating)
Open AccessArticle Synthesis of Ru2Br(μ-O2CC6H4R)4 (R = o-Me, m-Me, p-Me) Using Microwave Activation: Structural and Magnetic Properties
Inorganics 2014, 2(3), 524-536; doi:10.3390/inorganics2030524
Received: 4 July 2014 / Revised: 8 August 2014 / Accepted: 20 August 2014 / Published: 3 September 2014
Cited by 2 | PDF Full-text (3102 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
New bromidotetracarboxylatodiruthenium(II,III) compounds of the type [Ru2Br(μ-O2CC6H4R)4]n [R = o-Me (1), m-Me (2), p-Me (3)] have been prepared using [...] Read more.
New bromidotetracarboxylatodiruthenium(II,III) compounds of the type [Ru2Br(μ-O2CC6H4R)4]n [R = o-Me (1), m-Me (2), p-Me (3)] have been prepared using microwave-assisted methods. Syntheses by means of solvothermal and conventional activations have also been carried out to compare different preparation methods. The crystal structure determination of complexes 13 is also described. All compounds display a typical carboxylate-bridged paddlewheel-type structure with the metal atoms connected by four bridging carboxylate ligands. The axial bromide ligands connect the dimetallic units giving one-dimensional zigzag chains. The magnetic properties of all compounds have also been analyzed. Weak antiferromagnetic intermolecular interactions mediated by the bromide ligands and an appreciable zero field splitting are calculated in the fits of the magnetic data of these complexes. Full article
(This article belongs to the Special Issue Inorganic Syntheses Assisted by Microwave Heating)
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Open AccessArticle Microwave Plasma Production of Metal Nanopowders
Inorganics 2014, 2(2), 278-290; doi:10.3390/inorganics2020278
Received: 27 February 2014 / Revised: 23 May 2014 / Accepted: 5 June 2014 / Published: 12 June 2014
Cited by 2 | PDF Full-text (3849 KB) | HTML Full-text | XML Full-text
Abstract
Metal and metal alloy nanopowders were prepared by using the microwave plasma synthesis method. The microwave plasma was operated in atmospheric pressure at a frequency of 2.45 GHz. The precursor decomposed thermally in the plasma reaction region and the products were then [...] Read more.
Metal and metal alloy nanopowders were prepared by using the microwave plasma synthesis method. The microwave plasma was operated in atmospheric pressure at a frequency of 2.45 GHz. The precursor decomposed thermally in the plasma reaction region and the products were then condensed in the heat exchanger, were separated from the gas by the powder filter, and then finally collected in the powder collector. The effect of various processing parameters such as plasma gas, carrier gas, cooling gas, precursor raw materials and feeding rate were studied in this work. Cu, Mo, W, Mo-Ni and Fe-Co nanopowders were successfully prepared by using the microwave plasma synthesis method. The processing conditions can be tuned to manipulate the particle size of the nanopowders. Full article
(This article belongs to the Special Issue Inorganic Syntheses Assisted by Microwave Heating)
Open AccessArticle Microwave-Assisted Synthesis of Boron-Modified TiO2 Nanocrystals
Inorganics 2014, 2(2), 264-277; doi:10.3390/inorganics2020264
Received: 4 April 2014 / Revised: 19 May 2014 / Accepted: 21 May 2014 / Published: 6 June 2014
Cited by 2 | PDF Full-text (3868 KB) | HTML Full-text | XML Full-text
Abstract
An efficient microwave-assisted synthesis of TiO2:(B) nanorods, using titanium tetraisopropoxide (TTIP), benzyl alcohol as the solvent, together with boric acid and oleic acid as the additive reagents, has been developed. Chemical modification of TTIP by oleic acid was demonstrated as [...] Read more.
An efficient microwave-assisted synthesis of TiO2:(B) nanorods, using titanium tetraisopropoxide (TTIP), benzyl alcohol as the solvent, together with boric acid and oleic acid as the additive reagents, has been developed. Chemical modification of TTIP by oleic acid was demonstrated as a rational strategy to tune the shape of TiO2 nanocrystals toward nanorod formation. The differently-shaped TiO2:(B) nanocrystals were characterized in detail by transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and nitrogen absorption-desorption. Oleic acid coordinated on the nanocrystal surface was removed by the reduction of its carboxyl group, and the photocatalytic activity of bare TiO2 nanocrystals, under visible light irradiation, was also evaluated. The synthesized TiO2 anatase nanorods exhibited a good photoactivity and completely degraded Rhodamine B solution within three hours. Full article
(This article belongs to the Special Issue Inorganic Syntheses Assisted by Microwave Heating)
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Review

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Open AccessReview Microwave Plasma Synthesis of Materials—From Physics and Chemistry to Nanoparticles: A Materials Scientist’s Viewpoint
Inorganics 2014, 2(3), 468-507; doi:10.3390/inorganics2030468
Received: 10 June 2014 / Revised: 6 August 2014 / Accepted: 11 August 2014 / Published: 18 August 2014
Cited by 7 | PDF Full-text (5180 KB) | HTML Full-text | XML Full-text
Abstract
In this review, microwave plasma gas-phase synthesis of inorganic materials and material groups is discussed from the application-oriented perspective of a materials scientist: why and how microwave plasmas are applied for the synthesis of materials? First, key players in this research field [...] Read more.
In this review, microwave plasma gas-phase synthesis of inorganic materials and material groups is discussed from the application-oriented perspective of a materials scientist: why and how microwave plasmas are applied for the synthesis of materials? First, key players in this research field will be identified, and a brief overview on publication history on this topic is given. The fundamental basics, necessary to understand the processes ongoing in particle synthesis—one of the main applications of microwave plasma processes—and the influence of the relevant experimental parameters on the resulting particles and their properties will be addressed. The benefit of using microwave plasma instead of conventional gas phase processes with respect to chemical reactivity and crystallite nucleation will be reviewed. The criteria, how to choose an appropriate precursor to synthesize a specific material with an intended application is discussed. A tabular overview on all type of materials synthesized in microwave plasmas and other plasma methods will be given, including relevant citations. Finally, property examples of three groups of nanomaterials synthesized with microwave plasma methods, bare Fe2O3 nanoparticles, different core/shell ceramic/organic shell nanoparticles, and Sn-based nanocomposites, will be described exemplarily, comprising perspectives of applications. Full article
(This article belongs to the Special Issue Inorganic Syntheses Assisted by Microwave Heating)

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