Microwave Synthesis of Lead-Barium Titanate

ABSTRACTSince the volatilization of lead oxides is inevitable at high temperatures, the problems of maintaining stoichiometry and air pollution are of great concern in conventional synthesis of lead-barium titanate. We have demonstrated that the reaction between PbO, BaO and TiO2 could be greatly accelerated by using microwave energy. The synthesis of (PbxBa1-x)TiO3 can be completed in 10 minutes at about 750°C by microwave heating, while it takes at least 2 hours at 850°C in a conventional heating. The weight loss of PbO during microwave synthesis was much less than that in conventional synthesis. Thus the microwave synthesis technique may find wide applications for the preparation of various lead-containing materials in the production of electronic ceramics.

Download Full-text

Manufacture of Glass Foam by Predominantly Direct Microwave Heating of Recycled Glass Waste

Transactions on Networks and Communications ◽

10.14738/tnc.74.7214 ◽

2019 ◽

Vol 7 (4) ◽

pp. 37-45

Author(s):

Sorin Mircea AXINTE ◽

Lucian Paunescu ◽

Marius Florin Dragoescu ◽

Ana Casandra Sebe

Keyword(s):

Microwave Heating ◽

Foam Glass ◽

Weight Ratio ◽

Original Method ◽

Microwave Energy ◽

Waste Glass ◽

Conventional Heating ◽

Thin Wall ◽

Glass Waste ◽

Materials Used

The paper presents authors’ contribution to the improvement of the manufacturing technique of foam glass using the microwave energy. Due to the physical and mechanical characteristics, this material, obtained by the sintering process of waste glass at high temperature, constitutes a viable replacer of existing similar materials, used especially in construction. Unlike the conventional heating methods used worldwide, the company Daily Sourcing & Research SRL Bucharest tested lately microwave heating techniques in the manufacturing process of foam glass. In the paper it is presented an original method based on the feature of the powder mixture composed by waste glass (over 97 wt.%) and the foaming agent (calcium carbonate) to absorb the microwave energy and convert it to heat since the ambient temperature, using a silicon carbide and silicon nitride (80/ 20 weight ratio) crucible with thin wall (2.5 mm), which allows both a preponderantly direct heating and partially an indirect heating of the material. The main parameters of the process (specific consumption of energy, heating speed, process temperature and duration) were significant improved compared to the previous experiments.

Download Full-text

Microwave heating behavior and microwave absorption properties of barium titanate at high temperatures

AIP Advances ◽

10.1063/1.4953325 ◽

2016 ◽

Vol 6 (6) ◽

pp. 065001 ◽

Cited By ~ 2

Author(s):

K. Kashimura ◽

H. Sugawara ◽

M. Hayashi ◽

T. Mitani ◽

N. Shinohara

Keyword(s):

Barium Titanate ◽

Microwave Heating ◽

Microwave Absorption ◽

High Temperatures ◽

Absorption Properties ◽

Microwave Absorption Properties ◽

Heating Behavior

Download Full-text

The Analysis of Parametric Sensitivity Based on Designing and Optimization of a New Microwave Heating System

High Temperature Materials and Processes ◽

10.1515/htmp-2016-0034 ◽

2017 ◽

Vol 36 (8) ◽

pp. 847-853 ◽

Cited By ~ 1

Author(s):

Hua Chen ◽

Jin Zhang ◽

Zebin Fan ◽

Jinhui Peng ◽

Shaohua Ju

Keyword(s):

Microwave Heating ◽

Heating System ◽

Absorption Efficiency ◽

Microwave Energy ◽

Utilization Efficiency ◽

Conventional Heating ◽

Important Index ◽

Energy Absorption Efficiency ◽

Matching Performance ◽

Heating Technology

AbstractMicrowave-assisted heating technology has become a popular alternative to conventional heating technologies because of its many advantages. However, the matching performance of microwave heating system is of particular concern because it provides an important index of the utilization efficiency of microwave energy. In this work, a new microwave heating system is designed by the theory of optical resonator in first. Then the comprehensive analysis of the mutual coupling of high sensitive geometrical and material parameters were investigated based on this new microwave heating system at 2.45 GHz. It is demonstrated that the thickness of materials dramatically influences microwave energy absorption efficiency and should be carefully considered and perhaps given priority. Moreover, it is shown that matching performance is the best when the titanium concentrates thickness at about 0.075 m.

Download Full-text

A Review of Microwave Synthesis of Zinc Oxide Nanomaterials: Reactants, Process Parameters and Morphologies

Nanomaterials ◽

10.3390/nano10061086 ◽

2020 ◽

Vol 10 (6) ◽

pp. 1086 ◽

Cited By ~ 6

Author(s):

Jacek Wojnarowicz ◽

Tadeusz Chudoba ◽

Witold Lojkowski

Keyword(s):

Zinc Oxide ◽

Microwave Heating ◽

Microwave Synthesis ◽

Hybrid Methods ◽

Consumer Products ◽

Conventional Heating ◽

Materials Engineering ◽

Macro Scale ◽

Primary Groups ◽

New Applications

Zinc oxide (ZnO) is a multifunctional material due to its exceptional physicochemical properties and broad usefulness. The special properties resulting from the reduction of the material size from the macro scale to the nano scale has made the application of ZnO nanomaterials (ZnO NMs) more popular in numerous consumer products. In recent years, particular attention has been drawn to the development of various methods of ZnO NMs synthesis, which above all meet the requirements of the green chemistry approach. The application of the microwave heating technology when obtaining ZnO NMs enables the development of new methods of syntheses, which are characterised by, among others, the possibility to control the properties, repeatability, reproducibility, short synthesis duration, low price, purity, and fulfilment of the eco-friendly approach criterion. The dynamic development of materials engineering is the reason why it is necessary to obtain ZnO NMs with strictly defined properties. The present review aims to discuss the state of the art regarding the microwave synthesis of undoped and doped ZnO NMs. The first part of the review presents the properties of ZnO and new applications of ZnO NMs. Subsequently, the properties of microwave heating are discussed and compared with conventional heating and areas of application are presented. The final part of the paper presents reactants, parameters of processes, and the morphology of products, with a division of the microwave synthesis of ZnO NMs into three primary groups, namely hydrothermal, solvothermal, and hybrid methods.

Download Full-text

Microwaves and Heterogeneous Catalysis: A Review on Selected Catalytic Processes

Catalysts ◽

10.3390/catal10020246 ◽

2020 ◽

Vol 10 (2) ◽

pp. 246 ◽

Cited By ~ 14

Author(s):

Vincenzo Palma ◽

Daniela Barba ◽

Marta Cortese ◽

Marco Martino ◽

Simona Renda ◽

...

Keyword(s):

Heterogeneous Catalysis ◽

Energy Saving ◽

Microwave Heating ◽

Microwave Radiation ◽

Heterogeneous Catalysts ◽

Conventional Heating ◽

Specific Effects ◽

Natural Choice ◽

Future Challenges ◽

Catalyzed Reactions

Since the late 1980s, the scientific community has been attracted to microwave energy as an alternative method of heating, due to the advantages that this technology offers over conventional heating technologies. In fact, differently from these, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy embodied in the microwaves. Application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. The synthesis and sintering of materials by means of microwave radiation has been used for more than 20 years, while, future challenges will be, among others, the development of processes that achieve lower greenhouse gas (e.g., CO2) emissions and discover novel energy-saving catalyzed reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this review is to give an overview of microwave applications in the heterogeneous catalysis, including the preparation of catalysts, as well as explore some selected microwave assisted catalytic reactions. The review is divided into three principal topics: (i) introduction to microwave chemistry and microwave materials processing; (ii) description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) applications of microwaves in some selected chemical processes, including the preparation of heterogeneous catalysts.

Download Full-text

A comparative study on quality parameters of pumpkin, melon and sunflower oils during thermal treatment

OCL ◽

10.1051/ocl/2019028 ◽

2019 ◽

Vol 26 ◽

pp. 32 ◽

Cited By ~ 2

Author(s):

Zhana Petkova ◽

Ginka Antova

Keyword(s):

Fatty Acid Composition ◽

Fatty Acid ◽

Thermal Treatment ◽

Microwave Heating ◽

Acid Composition ◽

Seed Oil ◽

Conventional Heating ◽

Melon Seed ◽

Sunflower Oils ◽

Melon Seed Oil

Current paper reveals the impact of thermal treatment on the quality of two seed oils – pumpkin and melon compared to the quality of the most used oil – sunflower oil. Conventional and microwave heating were used for processing the oils. The duration of the thermal treatment was 9, 12 and 18 min for the conventional heating. The microwave heating was performed with two microwave powers of the equipment (600 W and 900 W) for 3, 6, 9 and 12 min. At every stage of the thermal processing were determined acid and peroxide value, the absorbance of the oils at 232 and 268 nm, tocopherol and fatty acid composition. It was observed that the degree of oxidation of the examined oils during microwave and conventional heating increased with the duration of the thermal process and the power of the microwaves. Also, the two methods of heating had a little impact on the processes leading to the formation of free fatty acids. Total tocopherols of the melon seed oil were more stable to thermal treatment. The amount of linoleic acid decreased in the pumpkin and sunflower oils during microwave treatment, while that of oleic and palmitic acid relatively increased. The biggest change in the fatty acid composition of both oils was found during microwave heating at 900W. The changes in fatty acid composition of thermally treated melon seed oil were insignificant. Overall, melon seed oil was observed to be more thermally stable than pumpkin and sunflower oils.

Download Full-text

Comparative study of conventional and microwave heating of polyacrylonitrile-based fibres

Journal of Polymer Engineering ◽

10.1515/polyeng-2020-0167 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Guozhen Zhao ◽

Jianhua Liu ◽

Lei Xu ◽

Shenghui Guo

Keyword(s):

Microwave Heating ◽

Surface Defects ◽

Energy Dispersive Spectrometer ◽

Xrd Analysis ◽

Economic Benefits ◽

Heating Time ◽

Oxidation Temperature ◽

Conventional Heating ◽

Heating Method ◽

Molecular Arrangement

Abstract The effects of the conventional heating method and the microwave heating method on polyacrylonitrile-based fibres in the temperature range of 180–280 °C were investigated. Fourier transform infrared spectroscopy, X-ray wide-angle scattering, Raman spectroscopy, energy-dispersive spectrometer, scanning electron microscopy and bulk density were used to characterise the properties of the samples. Results show that the microwave heating method can shorten the pre-oxidation time, reduce pre-oxidation temperature and reduce the number of surface defects. The pre-oxidised fibres obtained by the microwave heating method exhibit not only good crystallite size but also a smooth surface. Atomic morphology and molecular arrangement are orderly inside the fibre. The FT-IR spectrum shows that the oxidation reaction occurs at 220 °C, and the CI value of PAN fibers stabilised by microwave heating is the larger than the fibers stabilised by conventional heating. XRD analysis shows that fibers stabilised by microwave heating have low stack domains. The SEM and Raman spectra indicate that hydrogen peroxide can improve the surface finish of the fibers and reduce defects. Microwave heating can reduce the pre-oxidation temperature by about 20 °C and shorten the heating time. The economic benefits of using this method are significantly improved.

Download Full-text

Preparation of WC-TiC-Ni3Al-CaF2 functionally graded self-lubricating tool material by microwave sintering and its cutting performance

High Temperature Materials and Processes ◽

10.1515/htmp-2020-0004 ◽

2020 ◽

Vol 39 (1) ◽

pp. 45-53 ◽

Cited By ~ 1

Author(s):

Siwen Tang ◽

Rui Wang ◽

Pengfei Liu ◽

Qiulin Niu ◽

Guoqing Yang ◽

...

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Microwave Heating ◽

Cutting Performance ◽

Conventional Heating ◽

Hard Alloys ◽

Dry Cutting ◽

Temperature Oxidation ◽

Lubricating Material ◽

Heating Technology

AbstractWith the concern of the environment, green dry cutting technology is getting more and more attention and self-lubricating tool technology plays an important role in dry cutting. Due to the demand for high temperature performance of tools during dry cutting process, cemented carbide with Ni3Al as the binder phase has received extensive attention due to its excellent high temperature strength and high temperature oxidation resistance. In this paper, WC-TiC-Ni3Al-CaF2 graded self-lubricating material and tools were prepared by microwave heating method, and its microstructure, mechanical properties and cutting performance were studied. Results show that gradient self-lubricating material can be quickly prepared by microwave heating technology, and the strength is equivalent to that of conventional heating technology. CaF2 not only plays a role in self-lubrication, but also refines the grain of the material. A reasonable gradient design can improve the mechanical properties of the material. When the gradient distribution exponent is n1 = 2, the material has high mechanical properties. Cutting experiments show that the WC-TiC-Ni3Al-CaF2 functional gradient self-lubricating tool has better cutting performance than the homogeneous WC-TiC-Ni3Al hard alloys.

Download Full-text

Vitamin B1 and B6 Retention in Milk after Continuous-Flow Microwave and Conventional Heating at High Temperatures

Journal of Food Protection ◽

10.4315/0362-028x-64.6.890 ◽

2001 ◽

Vol 64 (6) ◽

pp. 890-894 ◽

Cited By ~ 9

Author(s):

ISABEL SIERRA ◽

CONCEPCIÓN VIDAL-VALVERDE

Keyword(s):

High Temperatures ◽

Continuous Flow ◽

Vitamin B6 ◽

Vitamin B1 ◽

Raw Milk ◽

Microwave Treatment ◽

Conventional Heating ◽

Conventional System ◽

Tubular Heat Exchanger ◽

Heating And Cooling

The effect of continuous-flow microwave treatment at high temperatures on the retention of vitamins B1 and B6 in raw milk with different fat content was evaluated. Results were compared with those obtained using a conventional system (tubular heat exchanger) with the same heating and cooling phases. Heat treatment of whole (3.4% fat) and skim (0.5% fat) milk at 90°C produced no losses of vitamin B1 or vitamin B6 (pyridoxamine and pyridoxal). However, at 110 and 120°C, while vitamin B1 content of milk remained constant, pyridoxamine increased (4 to 5% and 9 to 11%, respectively) and pyridoxal decreased (5 to 6% and 9 to 12%, respectively). Under the assayed conditions, no differences were observed between the content of these vitamins in conventionally and continuous-flow microwave-treated milk.

Download Full-text