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A. Ragulya - One of the best experts on this subject based on the ideXlab platform.
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tough ceramics by Microwave Sintering of nanocrystalline titanium diboride ceramics
Ceramics International, 2014Co-Authors: Dinesh K. Agrawal, D Demirskyi, A. RagulyaAbstract:Abstract Dense composites of TiB 2 with additions of TiN have been produced by Microwave Sintering. Microwave Sintering was conducted at 1200–1700 °C under controlled atmosphere. The effects of composition, Sintering temperature, on densification, microstructure, and mechanical properties were investigated. Microwave Sintering resulted in uniform crack-free uniform microstructure, as well as maximum relative density of 99% and bending strength of 368±15 MPa, Young's modulus of 440±11 GPa, electric resistivity of 2×10 −5 Ω cm, Vickers hardness of 26.2 ±0.4 GPa, and a fracture toughness of 6.2±0.34 MPa·m 1/2 were obtained using 36 wt% TiB 2 , and Sintering for 10 min at 1650 °C.
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densification and grain growth during Microwave Sintering of titanium diboride
Scripta Materialia, 2013Co-Authors: Jiping Cheng, Dinesh K. Agrawal, D Demirskyi, A. RagulyaAbstract:Dense TiB 2 ceramics have been produced by Microwave Sintering at 1600–1700 °C under a controlled atmosphere. The effect of Sintering conditions on the densification, microstructure and mechanical properties were investigated. Microwave Sintering resulted in a uniform crack-free uniform microstructure; a density of 98.5%, a bending strength of 410 ± 15 MPa, a Young’s modulus of 495 ± 10 GPa, an electrical resistivity of 1 × 10 −5 Ω cm, a Vickers hardness of 24.5 ± 0.5 GPa and a fracture toughness of 5.42 ± 0.20 MPa m 1/2 were obtained after Sintering for 30 min at 1700 °C.
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Low-temperature Microwave Sintering of TiN–SiC nanocomposites
Journal of Materials Science, 2012Co-Authors: Dmytro Demirskyi, A. RagulyaAbstract:Densification kinetics study during Microwave Sintering of titanium nitride-based nanocomposite has been conducted. A series of TiN–SiC compositions with 1, 3, 5 wt% of silicon carbide were Microwave sintered at relatively low Sintering temperatures (900–1,300 °C) for 0–30 min. The SiC content influenced on heating uniformity and final density and grain-size achieved. Densification process during Microwave Sintering obeyed the mechanism of grain-boundary diffusion with activation energy of 235 kJ mol−1. Microwave Sintering resulted in fine microstructure (~300 nm) and hence high values of micro hardness (~20 GPa).
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neck growth kinetics during Microwave Sintering of nickel powder
Journal of Alloys and Compounds, 2011Co-Authors: D Demirskyi, Dinesh K. Agrawal, A. RagulyaAbstract:Abstract Model experiments on initial stage of Microwave Sintering of nickel powder showed anomalous neck-growth rate during isothermal soaking, which is not the case for conventional Sintering. Neck growth was determined as a function of time. Values for the neck growth exponent in the neck growth equation, (x/a)n = Bt, of 5.2, 5.4, 5.8, and 5.9 were found for within the temperature range 700–950 °C, respectively. The evidences of formation of liquid phase during Microwave Sintering have been revealed, that may support enhancement of mass transfer during Sintering process. The activation energy of 48 kJ mol−1 was found for Microwave Sintering of nickel, according to sphere-to-sphere model. Value revealed is significantly lower then values for conventional Sintering (136 kJ mol−1), and is on same level with activation energy for diffusion of metals in liquid state. An explanation and analysis of this phenomenon has been attempted.
Dinesh K. Agrawal - One of the best experts on this subject based on the ideXlab platform.
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Tunable BST:MgO Dielectric Composite by Microwave Sintering
Ferroelectrics, 2020Co-Authors: S. Agrawal, Dinesh K. Agrawal, Amar S. BhallaAbstract:Microwave Sintering route was used for obtaining minimum chemical reactivity between the two phases (for sharp grain boundaries) and controlled microstructure in the composites of Ba1 − xSrxTiO3 (BST) and MgO. Composites of desirable compositions of ferroelectric BST and non-ferroelectric MgO were Microwave sintered at a frequency of 2.45 GHz. Low dielectric constant, controlled microstructure, high relative density, and sharp grain boundary in BST:MgO composites were achieved. The depressed dielectric constant and tangent loss, high tunability and K-factor values are measured in the sintered composites. This paper describes the detailed studies on the Microwave sintered BST:MgO composites and their tunable dielectric properties and microstructure development.
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tough ceramics by Microwave Sintering of nanocrystalline titanium diboride ceramics
Ceramics International, 2014Co-Authors: Dinesh K. Agrawal, D Demirskyi, A. RagulyaAbstract:Abstract Dense composites of TiB 2 with additions of TiN have been produced by Microwave Sintering. Microwave Sintering was conducted at 1200–1700 °C under controlled atmosphere. The effects of composition, Sintering temperature, on densification, microstructure, and mechanical properties were investigated. Microwave Sintering resulted in uniform crack-free uniform microstructure, as well as maximum relative density of 99% and bending strength of 368±15 MPa, Young's modulus of 440±11 GPa, electric resistivity of 2×10 −5 Ω cm, Vickers hardness of 26.2 ±0.4 GPa, and a fracture toughness of 6.2±0.34 MPa·m 1/2 were obtained using 36 wt% TiB 2 , and Sintering for 10 min at 1650 °C.
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densification and grain growth during Microwave Sintering of titanium diboride
Scripta Materialia, 2013Co-Authors: Jiping Cheng, Dinesh K. Agrawal, D Demirskyi, A. RagulyaAbstract:Dense TiB 2 ceramics have been produced by Microwave Sintering at 1600–1700 °C under a controlled atmosphere. The effect of Sintering conditions on the densification, microstructure and mechanical properties were investigated. Microwave Sintering resulted in a uniform crack-free uniform microstructure; a density of 98.5%, a bending strength of 410 ± 15 MPa, a Young’s modulus of 495 ± 10 GPa, an electrical resistivity of 1 × 10 −5 Ω cm, a Vickers hardness of 24.5 ± 0.5 GPa and a fracture toughness of 5.42 ± 0.20 MPa m 1/2 were obtained after Sintering for 30 min at 1700 °C.
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Microwave Sintering of hydroxyapatite ceramics
Journal of Materials Research, 2011Co-Authors: Yi Fang, Dinesh K. Agrawal, Della M. RoyAbstract:Hydroxyapatite ceramics have been fabricated by Microwave Sintering in a 500 W Microwave oven. Circular-plate specimens of various green densities were sintered in the oven at 1200 and 1300 °C, for 5, 10, and 20 min, respectively. Ceramics with density up to 97% of the theoretical were obtained. Density, grain size, microstructure, and strength of the ceramics sintered by Microwave and by conventional methods were compared. The results show that Microwave Sintering of hydroxyapatite is not only highly efficient in saving time and energy, but can also improve the microstructure and thus enhance mechanical strength of the ceramics.
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Continuous Microwave Sintering of Ceramics
MRS Proceedings, 2011Co-Authors: Jiping Cheng, Yi Fang, Dinesh K. Agrawal, Lei Chen, Yunjin Zhang, Jian Zhou, Xuebing DongAbstract:The Microwave Sintering technology is still at the developmental stage due to the limitation of the volume (or size) and batch of the ceramic products that can be fabricated by Microwave processing. The present paper introduces a new Microwave processing technique, i.e. a continuous Microwave Sintering, which makes it possible to sinter ceramic products with an infinite length in a Microwave field. By this technique, alumina-mullite ceramic rollers of 40 mm in diameter and 2400 mm in length have been successfully Microwave sintered. The exploratory results show this new technique could offer some new opportunities to scale up Microwave Sintering for industrial applications.
D Demirskyi - One of the best experts on this subject based on the ideXlab platform.
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tough ceramics by Microwave Sintering of nanocrystalline titanium diboride ceramics
Ceramics International, 2014Co-Authors: Dinesh K. Agrawal, D Demirskyi, A. RagulyaAbstract:Abstract Dense composites of TiB 2 with additions of TiN have been produced by Microwave Sintering. Microwave Sintering was conducted at 1200–1700 °C under controlled atmosphere. The effects of composition, Sintering temperature, on densification, microstructure, and mechanical properties were investigated. Microwave Sintering resulted in uniform crack-free uniform microstructure, as well as maximum relative density of 99% and bending strength of 368±15 MPa, Young's modulus of 440±11 GPa, electric resistivity of 2×10 −5 Ω cm, Vickers hardness of 26.2 ±0.4 GPa, and a fracture toughness of 6.2±0.34 MPa·m 1/2 were obtained using 36 wt% TiB 2 , and Sintering for 10 min at 1650 °C.
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densification and grain growth during Microwave Sintering of titanium diboride
Scripta Materialia, 2013Co-Authors: Jiping Cheng, Dinesh K. Agrawal, D Demirskyi, A. RagulyaAbstract:Dense TiB 2 ceramics have been produced by Microwave Sintering at 1600–1700 °C under a controlled atmosphere. The effect of Sintering conditions on the densification, microstructure and mechanical properties were investigated. Microwave Sintering resulted in a uniform crack-free uniform microstructure; a density of 98.5%, a bending strength of 410 ± 15 MPa, a Young’s modulus of 495 ± 10 GPa, an electrical resistivity of 1 × 10 −5 Ω cm, a Vickers hardness of 24.5 ± 0.5 GPa and a fracture toughness of 5.42 ± 0.20 MPa m 1/2 were obtained after Sintering for 30 min at 1700 °C.
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neck growth kinetics during Microwave Sintering of nickel powder
Journal of Alloys and Compounds, 2011Co-Authors: D Demirskyi, Dinesh K. Agrawal, A. RagulyaAbstract:Abstract Model experiments on initial stage of Microwave Sintering of nickel powder showed anomalous neck-growth rate during isothermal soaking, which is not the case for conventional Sintering. Neck growth was determined as a function of time. Values for the neck growth exponent in the neck growth equation, (x/a)n = Bt, of 5.2, 5.4, 5.8, and 5.9 were found for within the temperature range 700–950 °C, respectively. The evidences of formation of liquid phase during Microwave Sintering have been revealed, that may support enhancement of mass transfer during Sintering process. The activation energy of 48 kJ mol−1 was found for Microwave Sintering of nickel, according to sphere-to-sphere model. Value revealed is significantly lower then values for conventional Sintering (136 kJ mol−1), and is on same level with activation energy for diffusion of metals in liquid state. An explanation and analysis of this phenomenon has been attempted.
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neck growth kinetics during Microwave Sintering of copper
Scripta Materialia, 2010Co-Authors: D Demirskyi, Dinesh K. Agrawal, Andrey RagulyaAbstract:This paper presents results of an investigation of the neck growth kinetics during Microwave Sintering of free-packed copper powder. Application of the classical sphere-to-sphere approach showed similarities between Microwave and conventional Sintering processes for long soaking times. Anomalous neck growth during the initial stage of Microwave Sintering was also revealed, which might be caused by a non-conventional diffusion mechanism.
Monika Willertporada - One of the best experts on this subject based on the ideXlab platform.
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effect of particle size and heating rate in Microwave Sintering of 316l stainless steel
Powder Technology, 2014Co-Authors: O Ertugrul, Hoseon Park, Kazim Onel, Monika WillertporadaAbstract:Abstract The work evaluates the effect of heating rate in Microwave Sintering, and the effect of particle size of 316L powders in Microwave and conventional Sintering processes. The powders of 316L stainless steel were compacted by uniaxial press at 700 MPa, and sintered at 1250 °C for 1 h by means of conventional Sintering and Microwave Sintering. The Sintering atmospheres were Ar/H2 95/5% for conventional Sintering and Ar/H2 90/10% for Microwave Sintering. Mechanical properties were evaluated using tensile tests. The samples were characterized by optical microscopy and SEM. The porosity levels were determined using image analysis software. Microwave Sintering yields fully recrystallized microstructure different from conventional Sintering, however no difference in distribution and shape of pores was noticed. Heating rate in Microwave Sintering affects densification, tensile strength and elongation. Moreover, the use of fine powders improves physical and mechanical properties of the samples sintered by both methods.
G Prabhu - One of the best experts on this subject based on the ideXlab platform.
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Microwave Sintering of tungsten heavy alloys
Journal of Applied Research and Technology, 2018Co-Authors: G Prabhu, M. Sankaranarayana, T.k. NandyAbstract:To understand Microwave Sintering of heavy alloys with high tungsten content, 93W-4.9Ni-2.1Fe alloy was sintered using a 6 kW, 2.45 GHz Microwave Sintering furnace at 1783 K (1510˚oC) and 1793 K (1520˚oC). The alloy sintered at 1793 K (1520˚oC) achieved full densification and had improved microstructural features, superior mechanical properties compared to 99.4% densification and relatively inferior properties obtained in the alloy sintered at 1783 K (1510˚oC). This study also includes a comparison between Microwave sintered and conventionally sintered 93W-4.9Ni-2.1Fe alloy (sintered at 1793K (1520oC)). Contrary to the full densification and superior mechanical properties obtained in Microwave Sintering, conventional Sintering at 1793K (1520oC) resulted in only 99.6% densification and substantially inferior properties. Analyses of microstructure and fracture surface revealed that key microstructural parameters such as tungsten grain size, tungsten-tungsten contiguity, matrix volume fraction and also the fracture mode were significantly different between the alloys processed by the two routes. Possible reasons behind dissimilar densification, significantly different microstructures and mechanical properties obtained between these two modes of Sintering, are also discussed in this study.
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Microwave Sintering of tungsten
International Journal of Refractory Metals & Hard Materials, 2009Co-Authors: G Prabhu, Amitava Chakraborty, Bijoy SarmaAbstract:This study aims at Microwave Sintering of pure tungsten powder of as-received grade and tungsten powder activated by high-energy milling (HEM). Both the powder compacts are sintered under identical conditions and their sinterability is compared and analyzed for process optimization. Activated powder responds to Microwaves and shows significant densification in a relatively shorter duration. The scope of the present work is to understand the effects of high-energy milling on the sinterability of tungsten in Microwave and to make a comparative assessment between as-received (coarser) and activated (finer) tungsten powder in terms of their response to Microwave Sintering, densification and microstructure.