Microwave Sintering Furnace Research Articles

Preparation of BN@SiO2 nanofiber ceramic aerogel with ultralight, wave-transparent and heat-insulating for microwave sintering furnace

Thermal insulation devices play an extremely important role in enhancing microwave heating efficiency. However, existing wave-transparent insulation materials often exhibit high heat storage, low microwave transmittance at high temperatures, and poor oxidation and thermal shock resistance, hindering high-temperature applications for microwave sintering. To address this issue, we developed an ultralight and wave-transparent BN@SiO2 aerogel, which was fabricated through the in situ growth of SiO2 on the surfaces of BN fibers. The resulting composite aerogel demonstrated excellent high-temperature oxidation resistance and an impressively low density of 0.07 g/cm3. Furthermore, the dielectric constant of the BN@SiO2 aerogel ranged from 2.58 to 2.80, and its dielectric loss tangent was as low as 5.13 × 10−3–7.98 × 10−3 within the 2–10 GHz frequency range. The successful synthesis of BN@SiO2 aerogel provides new progress and research ideas for the development of wave transparent and thermal insulation materials.

Rapid fabrication of mechanical-improved hydroxyapatite scaffolds from the microwave sintering with homogenous incorporated nanosilver particles

In this study, the optimization of the dual-frequency microwave sintering furnace in the replica method was investigated for the rapid synthesis of Porous hydroxyapatite scaffolds (PHS). It was found that by controlling the microwave sintering condition, it is possible to produce PHS with promising abilities for bone tissue engineering applications.

Optimized manufacturing process of homogeneous microwave-sintered blocks of KLS-1 lunar regolith simulant

The use of materials from the Moon's surface based on In-Situ Resource Utilization (ISRU) is gaining considerable attention as a means of constructing infrastructure to sustain a human presence there. In particular, the sintering of lunar regolith appears a promising way to fabricate infrastructure on the lunar surface. This study presents a method to manufacture homogeneous blocks using a lunar regolith simulant. The tested simulant, KLS-1, was sintered under diverse conditions in a multi-mode microwave sintering furnace. Successful sintering requires the sample to be heated throughout, without generating a temperature gradient. This was achieved by testing various heating rates and sample sizes. X-ray computed tomography was used to assess the pore structure of sintered samples. While the optimized sintering conditions resulted in the formation of internal cracks by outgassing, preheating the KLS-1 in a vacuum oven at 250 °C effectively prevented the formation of internal cracks. The homogeneity of the blocks was confirmed by coring and measurements of true density, bulk density, porosity, and unconfined compressive strength. The robust reproducibility and similarity in physical and mechanical properties validate the viability of microwave sintering in manufacturing large and uniform blocks suitable for application as construction materials on the Moon.

Effect of impurities of Fe2O3 and TiO2 in bauxite on oxidation kinetics of β-SiAlON powders

The oxidation kinetics of β-SiAlON with and without impurities synthesized using α-Al2O3, Si, Al, Fe2O3 or TiO2 powders at 1573 K in microwave sintering furnace, were investigated. The initial oxidation temperature of β-SiAlON with impurities was lower than that sample without impurities. In the initial oxidation stage at 1373–1473 K, the lattice deformation accelerated oxidation rate of β-SiAlON with impurities. However, in the final oxidation stage, the oxidation rate of β-SiAlON with impurities was much lower than that of reference sample, because impurities promote glass film formation on surface of β-SiAlON particles, reducing the chance of β-SiAlON reacting with O2.

Experimental investigation for cutting performance of cemented carbide cutting insert developed through microwave sintering

In this paper cemented carbide cutting insert with the variation of cobalt alloy has been developed through sintering via microwave radiation processing technique. The Compact samples of uniform mixed WC-2Co and WC-4Co alloy powder has been placed in a microwave sintering furnace cavity and heated at an equal heating rate i.e. 40°C/min upto 1450°C. The sintered sample has been characterized for properties like densities, Vickers hardness, and fracture toughness. The relative densities of the sample are found to be 90–95% of the theoretical density. The highest Vickers hardness and toughness are found to be 1830 HV and 12.28 MPa. (m)-1/2 for WC-2Co and WC-4Co samples. The hardness and toughness properties are found to increase with an increase in the temperature. With an increase in the percentage of binder, i.e. Co in the alloys the toughness characteristic of sintered sample is found to increase whereas hardness decreases. The sintered specimen has been modified for cutting edges accordingly to act as a cutting insert. The machining of duplex stainless steel has been performed by using sintered samples. The machining performance for the prepared tool has been compared with the standard tool. The maximum cutting force required during the machining is approximately 650 N and it is 10–12% higher than the standard tool. Surface roughness during the machining has been found to be 2.83 μm during the machining. Thus, a comparable cutting insert with high-quality mechanical properties has been developed using microwave sintering.

Microwave heat treatment on kyanite for mullite formation and the preparation of zirconia toughened mullite

This article deals with the investigations on mullite ceramics formation from Kyanite sample- an alumino-silicate mineral with microwave heating. In the present investigation kyanite was heated in microwave sintering furnace with calcined alumina, silicon carbide, zirconium dioxide and binder for mullite formation as well as for the preparation of zirconia toughened mullite product. The results of these studies reveal that how a small amount of zirconium dioxide helps in toughening the mullite formation for refractory and ceramics applications. The results shows that microwave heating method is one of the most novel and eco-friendly process for such toughened mullite formation, well within very short period of time. The observations with mullite formation and zirconia toughened mullite formation were observed with the structural data using X-ray diffraction data, field effect scanning electron microscope and energy dispersive spectroscopy. Future studies are still in process.

Damping characteristics of pure aluminum: A comparison of microwave and conventional sintering

The current research focuses on how heating mode in powder metallurgy affects the damping properties of pure aluminum. The aluminum powder was compacted in a hydraulic press measuring 40 x 12 x 1.5mm3 and heated in a muffle furnace (conventional) and a microwave sintering furnace. The damping measurements were conducted on the samples using a dynamic mechanical analyzer under dual cantilever mode at various vibrating frequencies of 0.1, 1 and 10Hz from room temperature (RT) to 150°C at constant strain. Results demonstrated that the microwave sintered samples exhibit high storage modulus and high damping capacities compared to conventional sintered samples. The mechanisms that support this behavior are investigated and presented.

Effect of 2 wt.% Addition of Fe on the Compressive Properties and Corrosion Behavior of Zn-HAp-Fe Material

The present work deals in developing new zinc-based composite material for bone repair using a powder metallurgy process. Zinc (Zn), hydroxyapatite (HAp), and iron (Fe) powders were mechanically mixed with ball milling. Subsequently, the powder mixture was compacted to form the green compact. After that, the green compacts were sintered using a microwave sintering furnace. The mechanical and electrochemical behaviors of the prepared Zn-based samples were tested as per the standards. X-ray diffraction and energy-dispersive spectroscopic examinations revealed the existence of HAp and Fe in the Zn matrix. The compressive yield strength and compressive strength of the developed Zn-5HAp-2Fe material were found to be 117.91 ± 7.42 and 170.87 ± 7.41 MPa, respectively. In vitro electrochemical corrosion analysis of the developed Zn-5HAp-2Fe sample in simulated body fluid solution unveiled the corrosion rate as 0.116 ± 0.021 mm·year–1. The mechanical and degradation behaviors of Zn-5HAp-2Fe material showed the potential to be used as a bone fixation material.

Structural and Mechanical Properties of Al-SiC-ZrO2 Nanocomposites Fabricated by Microwave Sintering Technique

In the present study, Al-SiC-ZrO2 nanocomposites were developed and characterized. Towards this direction, the aluminum (Al) matrix was reinforced with nano-sized silicon carbide (SiC) and zirconium dioxide (ZrO2), and the mixture was blended using ball milling technique. The blended powder was compacted and sintered in a microwave sintering furnace at 550 °C with a heating rate of 10 °C/min and a dwell time of 30 min. The amount of SiC reinforcement was fixed to 5 wt.%, while the concentration of ZrO2 was varied from 3 to 9 wt.% to elucidate its effect on the microstructural and mechanical properties of the developed nanocomposites. Microstructural analysis revealed the presence and uniform distribution of reinforcements into the Al matrix without any significant agglomeration. The mechanical properties of Al-SiC-ZrO2 nanocomposites (microhardness and compressive strength) were observed to increase with the increase in the concentration of ZrO2 nanoparticles into the matrix. Al-SiC-ZrO2 nanocomposites containing 9 wt.% of ZrO2 nanoparticles demonstrated superior hardness (67 ± 4 Hv), yield strength (103 ± 5 MPa), and compressive strength (355 ± 5 MPa) when compared to pure Al and other compositions of the synthesized composites. Al-SiC-ZrO2 nanocomposites exhibited the shear mode of fracture under compression loadings, and the degree of deformation was restricted due to the work hardening effect. The appealing properties of Al-SiC-ZrO2 nanocomposites make them attractive for industrial applications.

Effect of sintering parameters on the microstructure and compressive mechanical properties of porous Fe scaffold fabricated using 3D printing and pressure less microwave sintering

The demand for the porous scaffold has been increasing globally in the biomedical field due to numerous advantages over dense structures like high damping capacity, high specific strength, and improved cell integration growth. In the present study, porous iron scaffolds were fabricated using micro-extrusion-based three-dimensional printing and pressureless microwave sintering. For the preparation of samples, metal-based polymeric ink was developed. Thereafter, cylindrical samples were printed and then sintered in a microwave sintering furnace. The experimental investigations were performed to estimate the effect of sintering parameters such as sintering temperature, heating rate and soaking time on the compressive and microstructural property of the fabricated samples. Microstructural characterization was done using the electron backscatter diffraction technique. The experimental observations deduced that the compressive yield strength and apparent density of the sintered sample increased with the increase in sintering temperature and decreased with a further rise in temperature. Moreover, the electron backscatter diffraction analysis unveiled that the high heating rate resulted in the reduction of compressive yield strength due to rapid grain growth. Additionally, the significant effect of soaking time on the compressive mechanical properties was also noticed due to the increase in the grain size diameter. From the X-ray diffraction plot, it was found that there was no contamination present in the fabricated scaffold. In order to evaluate the process capability, a case study was performed wherein the topologically ordered porous structure of iron was fabricated at optimum sintering parameters.

Fabrication and properties of Si2N2O ceramics for microwave sintering furnace

The Si2N2O ceramics with low dielectric constant, low thermal diffusivity and high thermal shock resistance were successfully prepared by vacuum sintering. The amorphous Si3N4 was used as raw material with Li2CO3 as sintering additive. The phase, microstructure, oxidized resistance, mechanical and dielectric properties of the Si2N2O ceramics were investigated. XRD analysis showed that the suitable content of Li2CO3 could promote the generation of Si2N2O ceramics. However, the excess or insufficient amount of Li2CO3 additive would cause decomposition of Si2N2O phase. The Li2O volatilized at high temperature leaving highly pure (99.63%) porous Si2N2O ceramics. The flexural strength of the porous Si2N2O ceramics (with ?49.19%of open porosity) was about 30MPa, the residual strength ratio was more than 70% after 1300?C quenching in air. The SiO2 layer formed by oxidization could prevent Si2N2O ceramics from further oxidizing. Therefore, these Si2N2O ceramics will be excellent thermal insulation and wave-transparent materials for high temperature microwave sintering furnace.

Microwave sintering of tungsten heavy alloys

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.

Morphological Characterization Of Titania Slag Obtained From Red Sediment Placer Ilmenite Using Microwave Energy

This paper deals with the main objective to observe the effect of microwave heat treatment for the production of Titania rich slag and pig iron from placer ilmenite. The experiments carried out in the present investigation on the oxidized ilmenite sample for microwave heat treatment in microwave sintering furnace reveals that a product can be obtained containing Titania rich slag and metalized iron. The in-depth characterisation of these products using SEM–EDAX shows that around 75–85 % of titanium dioxide is formed in terms of titania rich slag by using microwave sintering furnace after reduction of oxidized ilmenite with proper stoichiometric graphitic carbon and silicon carbide (SiC) susceptor. The titania rich slag is considered to be better input material for production of pigment grade titanium dioxide. On the other hand, the pig iron obtained as by product from titania rich slag is also important for automobile and steel industries application.

The Synthesis of <i>In Situ</i> Cu-NbC-VC Nanocomposites by Mechanical Alloying

This paper presents a study on the synthesis of Niobium Carbide (NbC) and Vanadium Carbide (VC) in Copper (Cu) matrix by mechanical alloying (MA) technique. The elemental powders of Cu, Niobium (Nb), Vanadium (V) and synthetic graphite powder were mechanically alloyed for 30 hours at 400 rpm in a planetary ball mill Fritcsh “Pulverisette 6” according to the stoichiometric ratio of Cu-(10-x) vol%NbC-(0+x) vol%VC (x=1,3,5,7,9). The milling was performed under Argon atmosphere. The as-milled powder were compacted at 400 MPa and sintered using a microwave sintering furnace at 900°C with 1 hour soaking time. The phase identification was performed by using the X-ray Diffraction (XRD) analysis on the as-milled powders and sintered pellets. From the result, the NbC and VC phases were successfully formed after milling, and were precipitated after sintering. The average crystallite size and lattice strain of Cu, before and after sintering were 42.302 nm, 0.013%, and 71.294 nm, 0.004%, respectively.

Characterization of <i>In Situ</i> Cu-NbC-VC Nanocomposite by Mechanical Alloying and Microwave Sintering

This paper presents a study on the characterization of physical and electrical properties of Niobium Carbide (NbC) and Vanadium Carbide (VC) in Copper (Cu) matrix by mechanical alloying (MA) technique. The elemental powders of Cu, Niobium (Nb), Vanadium (V) and synthetic graphite powder were mechanically alloyed for 30 hours at 400 rpm in a planetary ball mill according to the stoichiometric ratio of Cu-(10-x) vol%NbC-(0+x) vol%VC (x=0,1,3,5,7,9) under Argon atmosphere. The as-milled powder were compacted at 400 MPa and sintered using microwave sintering furnace at 900°C with 1 hour soaking time. The phase identification was made by using the X-ray Diffraction (XRD) analysis. The microhardness, relative density and apparent porosity of sintered pellets were measured using Vickers microhardness and Archimedes principle, respectively. Electrical conductivity was measured using 2 point probe technique. Density of composite increase with increasing NbC content, while electrical conductivity also increase when NbC was added. Microhardness showed that single phase carbide has higher hardness value then multicarbide.

Influence of Sintering Process on the Mechanical Properties of Dental Zirconia Ceramics

Densification and mechanical properties of dental zirconia ceramics were evaluated by different sintering methods. Y-TZP zirconia block was used in this study. Sintering were performed in electric heating furnace and microwave sintering furnace, and then experimented and analyzed on a change in densification according to the sintering time, a change in densification according to thickness, flexural strength and micro-structure of zirconia specimens. Microwave sintering was very effective in considerable mechanical properties such as flexural strength and bulk density was drastically increased than conventional electric heating method. It is also shown that microwave sintering was faster and more economical than common method to be present in qualities which equal or exceed. It will be important to seek the accurate sintering condition of dental zirconia by microwave sintering method and the continuous research is necessary for the study of relationship between sintering methods and mechanical properties.

마이크로웨이브 소결방법에 따른 치과용 지르코니아의 물리적 특성

Purpose: Densification and mechanical properties of dental zirconia ceramics were evaluated by different sintering methods. Materials and Methods: Y-TZP zirconia block(Kavo <TEX>$Everest^{(R)}$</TEX> ZS blank, Kavo dental GmbH, Bismarckring, Germany) was used in this study. Sintering were performed in heat sintering furnace and microwave sintering furnace, and then experimented and analyzed on a change in densification according to the sintering time, a change in densification according to thickness, flexural strength and micro-structure in zirconia specimens. Results: Microwave sintering was very effective in considerable mechanical properties such as flexural strength and bulk density was drastically increased than conventional electric heating method. It is also shown that microwave sintering time was faster and more economical than common method to be present in qualities which equal or exceed. Conclusion: It will be important to seek the accurate sintering condition of dental zirconia by microwave sintering method and the continuous research is necessary for the study of relationship between sintering methods and mechanical properties.

Microwave Sintering of Barium Ferrite Nanoparticles Processed via Sol-Gel Method

Consolidated barium ferrite nanoparticles were expected to obtain better magnetic properties. Sol-gel method was used to produce the barium ferrite nanoparticles. Various calcination temperatures were set to obtain the single phase structure. XRD pattern and SEM image confirmed the nanoparticles with 48.66 nm and 70 nm, respectively. Compacted samples were sintered using microwave sintering and conventional furnace with various temperature and time. Magnetic measurement test shows that microwave sintered samples have better properties. The highest magnetic properties values for microwave sintered sample is obtained at 950°C for 60 minutes with coercivity (Hc) of 5565 Oersted, remanence (Br) of 1537 Gauss and saturation magnetization (Ms) of 37.04 emu/g.

Value Addition to Red Sediment Placer Sillimanite Using Microwave Energy and in Depth Structural and Morphological Characterization of Mullite

This paper deals with the effect of microwave energy for mullite formation from placer sillimanite. A mullite formation is seen when 60 % SiC and 5% binder are used with the composite charge material, i.e. sillimanite (60%) and Al2O3 (40%). The maximum temperature of the microwave sintering furnace achieved is 1355°C at 2450 W microwave power. Addition of 10 % binder to the same charge material with 60% SiC, the furnace temperature achieved is 1384°C at microwave power 1900 W. Mullite is formed within 25 minutes from the sillimanite, under the above experimental conditions. Whereas under the similar additive conditions, the mullite formed from sillimanite in conventional furnace heating, it took 3 hours at 1300°C. XRD data show the mullite phase for both the products obtained from microwave sintering furnace and conventional furnace. FESEM image analysis shows the mullite formations, SiC fibrous cluster and alumina needles in microwave treated sample. Thus microwave heat source is much more effective for value addition to red sediment placer sillimanite to form mullite in compare to conventional furnace.

Structural, magnetic and electrical properties of NiCuZn ferrites prepared by microwave sintering method suitable for MLCI applications

Polycrystalline NiCuZn soft ferrites with stoichiometric iron were prepared by a novel microwave sintering method. The powders were calcined, compacted and sintered at 950 °C for 30 min in a microwave sintering furnace. X-ray diffraction patterns confirm the formation of single phase cubic spinel structure. The grain size was estimated using SEM micrographs. The lattice constant is found to increase with increase in zinc concentration. The sintered ferrites have been investigated for their physical, magnetic and electrical properties such as bulk density, X-ray density, porosity, anisotropy constant, initial permeability, saturation magnetization, DC resistivity, dielectric constant and dielectric loss as a function of zinc concentration. Permeability, saturation magnetization, dielectric constant and dielectric loss were found to increase while DC resistivity was found to decrease with the replacement of Zn with Ni. The present series of ferrites are found to posses properties that are suitable for the core materials in multilayer chip inductors.