Microwave resonant sintering of powder metals

Rybakov, K. I.; Buyanova, M.

doi:10.1016/j.scriptamat.2018.02.014

Cited by 26 publications

(8 citation statements)

References 14 publications

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“…In general, industrial microwave frequency is 2.45 GHz or 915 MHz [27,36]. However, most of the experiments regarding materials [27,28,37,38], metallurgical properties [27,30], or food [36,39] processing by microwaves are based on microwave magnetrons with 2.45 GHz frequency [28]. Therefore, the frequency of the microwave was selected as 2.45 GHz in this work.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

“…Microwave heating is the process of coupling materials with microwaves, absorbing electromagnetic energy and transforming it into heat within the material volume, in which the heat is generated from the inside to the entire volume [27][28][29]. Therefore, the microwave method can treat uniform samples due to its features of volumetric and internal heating [30,31]. Yingguang Li et al [32,33] have reported curing of CFRP by microwave energy, and CFRP can absorb microwave energy and be heated effectively.…”

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confidence: 99%

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Recycling of Carbon Fibers from CFRP Waste by Microwave Thermolysis

Deng

Zhang

et al. 2019

Processes

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With the growth of the use of carbon fiber-reinforced polymer (CFRP) in various fields, the recovery of carbon fibers from CFRP waste is becoming a significant research direction. In the present work, degrading epoxy resin and recycling carbon fibers from CFRP waste by microwave thermolysis and traditional thermolysis were studied. The carbon fibers were successfully recovered by thermolysis under an oxygen atmosphere in this study. The properties of the recovered carbon fibers were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Raman spectroscopy. The result shows that using microwave thermolysis to recover carbon fibers from CFRP waste is an attractive prospect. Compared to the traditional method, the reaction time was reduced by 56.67%, and the recovery ratio was increased by 15%. Microwave thermolysis is faster, more efficient, requires less energy, and obtains cleaner recovered carbon fibers than those recovered using traditional thermolysis.Processes 2019, 7, 207 2 of 12 including mechanical processes [14,15], chemical methods [4,[16][17][18][19][20], and thermal technology [3,[21][22][23]. However, long carbon fibers are difficult to obtain using a mechanical process, and their mechanical properties are seriously damaged with this technique [24,25]. Liu et al. [13], Yildirir et al. [19], and Hyde et al. [20] have investigated recycling carbon fibers from CFRP using different solvents under subcritical or supercritical conditions. These methods are expensive, difficult to industrialize, and produce large amounts of liquid waste and hazardous gases [1]. Yang et al. [3], López et al. [22], and Ye et al. [23] have studied thermolysis methods of recovering carbon fibers from CFRP. The pyrolysis process is not very economical, producing multiple hazardous gases and depositing char on the carbon fiber surfaces [1,19,25]. Therefore, research to develop new methods of recovering carbon fibers from CFRP has begun.Microwave heating is gradually being used more often in the area of material processing due to its advantages of rapid, uniform, and selective heating [26]. Microwave heating is the process of coupling materials with microwaves, absorbing electromagnetic energy and transforming it into heat within the material volume, in which the heat is generated from the inside to the entire volume [27][28][29]. Therefore, the microwave method can treat uniform samples due to its features of volumetric and internal heating [30,31]. Yingguang Li et al. [32,33] have reported curing of CFRP by microwave energy, and CFRP can absorb microwave energy and be heated effectively. This study provides a great reference for microwave applications in the preparation and recovery of CFRP. Long Jiang et al. [34] reported that microwave irradiation is a flexible, easy-to-control, efficient method to recover high-value carbon fibers, and recovered carbon fibers could be directly used as reinforcement in new polymers (Polypropylene and nyl...

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Section: Materials and Experimental Proceduresmentioning

confidence: 99%

mentioning

confidence: 99%

Recycling of Carbon Fibers from CFRP Waste by Microwave Thermolysis

Deng

Zhang

et al. 2019

Processes

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“…This thin oxide layer is considered a dielectric ceramic layer [ 29 ] that covers an electrically conductive metallic particle, so those particles are actually similar to a composite material structure. Several studies have investigated microwave heating of metal powders [ 26 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. Furthermore, several recent theoretical studies were performed using effective-medium approximation models, where MW heating of electrically conductive powder particles surrounded by insulating oxide layer was investigated [ 33 , 36 , 40 ].…”

Section: Introductionmentioning

confidence: 99%

“…Several studies have investigated microwave heating of metal powders [ 26 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. Furthermore, several recent theoretical studies were performed using effective-medium approximation models, where MW heating of electrically conductive powder particles surrounded by insulating oxide layer was investigated [ 33 , 36 , 40 ]. Identifying the interaction of MW energy with a given electrically conductive metal particle with an insulated dielectric thin ceramic oxide layer is vital for a better understanding of many material processing processes and extremely needed for an accurate modeling of metal powders or metal-matrix composites.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Native Oxide Shell of Copper Metal Powder Spherical Particles

Mahmoud

2022

Materials

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The native oxide layer that forms on copper (Cu) metal spherical particle surfaces under ambient handling conditions has been shown to have a significant effect on sintering behavior during microwave heating in a previous study, where an abnormal expansion was observed and characterized during sintering of Cu compacts using reducing gases. Because microwave (MW) heating is selective and depends greatly on the dielectric properties of the materials, this thin oxide layer will absorb MW energy easily and can consequently be heated drastically starting from room temperature until the reduction process occurs. In the current study, this oxide ceramic layer was qualitatively and quantitatively characterized using the carrier gas hot extraction (CGHE) method, Auger electron spectroscopy (AES), and a dual-beam focused ion beam (FIB)/scanning electron microscope (SEM) system that combines both FIB and SEM in one single instrument. Two different commercial gas-atomized spherical Cu metal powders with different particle sizes were investigated, where the average oxygen content of the powders was found to be around 0.575 wt% using the CGHE technique. Furthermore, AES spectra along with depth profile measurements were used to qualitatively characterize this oxide layer, with only a rough quantitative thickness approximation due to method limitations and the electron beam reduction effect. For the dual-beam FIB-SEM system, a platinum (Pt) coating was first deposited on the Cu particle surfaces prior to any characterization in order to protect and to preserve the oxide layer from any possible beam-induced reduction. Subsequently, the Pt-coated Cu particles were then cross-sectioned in the middle in situ using an FIB beam, where SEM micrographs of the resulted fresh sections were characterized at a 36° angle stage tilt with four different detector modes. Quantitative thickness characterization of this native oxide layer was successfully achieved using the adapted dual-beam FIB-SEM setup with more accuracy. Overall, the native Cu oxide layer was found to be inhomogeneous over the particles, and its thickness was strongly dependent on particle size. The thickness ranged from around 22–67 nm for Cu powder with a 10 µm average particle size (APS) and around 850–1050 nm for one with less than 149 µm.

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“…Materials such as inorganic compounds have been synthetized successfully by applying different microwave heating techniques [ 10 , 11 , 12 , 13 , 14 ]. However, the sintering of piezoelectric materials by microwave of energy remains without substantial research [ 15 , 16 , 17 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Microwave-Assisted Synthesis and Sintering of Lead-Free KNL-NTS Ceramics

Lagunas-Chavarría

Navarro-Rojero²,

Salvador

et al. 2022

Materials

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Lead-free piezoelectric powders (K0.44Na0.52Li0.04)(Nb0.82Ta0.10Sb0.04)O3 were obtained by conventional and microwave-assisted reactive heating. Firstly, the synthesis of the material was carried out following the mixed oxide route and employing both traditional methods and microwave technology. Thermogravimetry, X-ray diffraction, field emission scanning electron microscopy and electrical properties analyses were evaluated. X-ray diffraction of the powders calcined by the microwave process shows the formation of perovskite structure with orthorhombic geometry, but it is possible to observe the presence of other phases. The presence of the secondary phases found can have a great influence on the heating rate during the synthesis on which the kinetics of the reaction of formation of the piezoelectric compound depend. The calcined powder was sintered at different temperatures by conventional and non-conventional processes. The microstructure of the ceramics sintered by microwave at 1050 °C for 10 min shows perovskite cubes with regular geometry, of size close to 2–5 µm. However, the observed porosity (~8%), the presence of liquid phase and secondary phases in the microstructure of the microwave sintered materials lead to a decrease of the piezoelectric constant. The highest d33 value of 146 pC/N was obtained for samples obtained by conventional at 1100 °C 2 h compared to samples sintered by microwave at 1050 °C 10 min (~15 pC/N).

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Microwave resonant sintering of powder metals

Cited by 26 publications

References 14 publications

Recycling of Carbon Fibers from CFRP Waste by Microwave Thermolysis

Recycling of Carbon Fibers from CFRP Waste by Microwave Thermolysis

Characterization of the Native Oxide Shell of Copper Metal Powder Spherical Particles

Effect of Microwave-Assisted Synthesis and Sintering of Lead-Free KNL-NTS Ceramics

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