• Title/Summary/Keyword: Microwave synthesis

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Synthesis of White Diamond Thin Film by Microwave Plasma Enhanced Chemical Vapor Deposition Method

  • Kim, S.H.;Y.S.ppark;Lee, J-W.;Song, S.A.
    • Proceedings of the Korean Vacuum Society Conference
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    • 1994.02a
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    • pp.98-101
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    • 1994
  • white diamond thin film, which should be compposed of almost ppure diamond, could be successfully obtained under high ppressure conditions(above 150 Torr) by means of MppECVD(microwave pplasma enhanced chemical vappor depposition, ASTeX 1.5 kW). Characteristics of the films with varing expperimental pparameters have been examined. From the expperimental results, we will discuss the surface morpphology and the growth mechanism of the films.

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Microwave Synthesis of Alpha Alumina Platelets Using Flux Method (Flux법에 의한 알파 알루미나 판상체의 마이크로파 합성)

  • Park, Seong-Soo;Kim, Jun-Ho;Kim, Sung-Wan;Lee, Sung-Hwan;Park, Jae-Hyun;Park, Hee-Chan
    • Journal of the Korean Ceramic Society
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    • v.39 no.5
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    • pp.473-478
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    • 2002
  • ${\alpha}-Al_2O_3$ platelets were synthesized by microwave heating the two different powder mixtures of $Al_2(SO_4)_3+2Na_2SO_4$ and ${\gamma}-Al_2O_3+2Na_2SO_4$ using flux method. DTA-TG, XRD and SEM were used to investigate the effect of microwave on the formation of ${\alpha}-Al_2O_3$ platelets. In the case of the mixture of $Al_2(SO_4)_3+2Na_2SO_4$, the microwave heated sample was ${\alpha}-Al_2O_3$ platelets composed of aggregates with smaller particle size compared to the conventionally heated sample. In the case of the mixture of ${\gamma}-Al_2O_3+2Na_2SO_4$, the temperature to form ${\alpha}-Al_2O_3$ platelets by the microwave heating was lower than that by the conventional heating and the morphology of the microwave heated sample was similar to that of the conventionally heated sample except that the microwave heated sample had smaller particle size compared to the conventionally heated sample.

Direct Microwave Sintering of Poorly Coupled Ceramics in Electrochemical Devices

  • Amiri, Taghi;Etsell, Thomas H.;Sarkar, Partha
    • Journal of Electrochemical Science and Technology
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    • v.13 no.3
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    • pp.390-397
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    • 2022
  • The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

A Green Chemical Approach towards the 'One-Pot' Synthesis, Spectral Characterization and in Vitro Antibacterial and Antifungal Activities of Morpholino Pyrimidines (친환경적 One Pot 합성, In Vitro에서 Morpholino Pyrimidines의 분광학적 특성과 항균성 및 항진균성)

  • Kanagarajan, V.;Thanusu, J.;Gopalakrishnan, M.
    • Journal of the Korean Chemical Society
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    • v.53 no.6
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    • pp.731-741
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    • 2009
  • ‘One-pot’ reaction procedure for the synthesis of novel morpholino pyrimidines (10-18) under microwave irradiation in ‘dry media’ in the presence of heterogeneous $NaHSO_4.SiO_2$ catalyst was developed. All the synthesized compounds were screened for their in vitro antibacterial activities against clinically isolated bacterial strains namely Bacillus subtilis, Bacillus cerues, Micrococcus luteus and Salmonella typhii and antifungal activities against fungal strains namely Aspergillus niger, Candida 6 and Candida 51. Structure activity relationship of the synthesized compounds against microbiological results was discussed.

Synthesis of Calcium Phosphate Minerals from Biowaste Clam Shells Using Microwave Heating

  • Bramhe, Sachin;Ryu, Jae-Kyung;Chu, Min Cheol;Balakrishnan, Avinash;Kim, Taik Nam
    • Korean Journal of Materials Research
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    • v.24 no.12
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    • pp.700-703
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    • 2014
  • Calcium phosphate minerals are biologically important because of their application in the fields of orthopaedics and dentistry. Herein we have tried to synthesize calcium phosphate minerals from biowaste clam shells. A simple microwave method was used to synthesize a mixture of calcium phosphate minerals such as hydroxyapatite, tri-calcium phosphate, and monetite. The microwave induces vibration of the dipole ions in the reagent. The heating and rearrangement of ions and atoms occurs during the process. The phases obtained in the final powder were ascertained by X-ray diffraction; the morphology of each sample was checked using a scanning electron microscope. We were able to obtain a mixture of calcium phosphate minerals using the microwave method; the calcined powder showed a brick like morphology, which is different from the rod shape morphology of the hydroxyapatite obtained using the hydrothermal process.