Hybrid Microwave Sintering Research Articles

Sintering behavior of alumina by microwave hybrid sintering

Microwave sintering is considered an ideal sintering process due to its rapid heating rate, low energy consumption, and uniform temperature distribution between the interior and surface. However, the difficulty of using a dilatometer and the lack of systematic research have hindered the investigation of activation energy and grain growth kinetics during microwave sintering. In this study, we examined the internal heating mechanism of microwave hybrid sintering, its sintering behavior, and its applicability to commercial processes such as tape casting. The results demonstrated that microwave hybrid sintering reduces the activation energy for both shrinkage and grain growth, confirming the presence of the "microwave effect." This study underscores the potential of microwave hybrid sintering for commercial applications, especially for large ceramic components.

Microwave Hybrid Sintering and Soldering of Cu-Cr-W Composite Material for Reactive Power Breakers.

Over 60% of reported failures for reactive power compensation systems are given for damage to electrical circuit breaker contacts. This paper presents a study on the development of microwave technology for sintering of W-Cu-Cr alloys at 1012 °C for 65 min using 623.38 W microwave power, as well as microwave joining at 231 °C of the W-Cu-Cr composite material on body contact using 475 W microwave power for 55 s. The joined components were subjected to mechanical and electrical tests in accordance with ICE standards to validate the applied technology. Tests of connection-disconnection of the electrical contacts were carried out in accordance with the maximum number of disconnections allowed by the manufacturer (2 cycles/min): 25 s rest time and 5 s operating time under load. The components of the electrical contact after 111237 switches were analyzed under a microscope revealing a reduction of the damaged area by 27% compared with the original contact.

Phase Evolution of Yttria-Stabilized Zirconia During Hybrid Microwave Sintering

Phase Evolution of Yttria-Stabilized Zirconia During Hybrid Microwave Sintering

Influence of sintering process on microstructure and mechanical properties of alumina ceramics: Spark plasma and microwave hybrid sintering

Improvement in hardness of alumina has advantages in ballistic performance and wear resistance of the material. Spark plasma sintering (SPS) and microwave hybrid sintering (MHS) were examined for improving the hardness of alumina and results are compared with conventional sintering (CS). Results show that the highest hardness is produced by SPS (20.4 GPa) followed by conventional sintering (18.6 GPa) and microwave hybrid sintering (18.5 GPa) process. Two separate Hall-Petch relations satisfy hardness variation in both SPS, and MHS/CS. The rate of densification is found to be higher for microwave hybrid sintering than the conventional sintering. Sintering of alumina at 1500 °C, the microwave hybrid sintering produced a higher density and grain size (90.6 % & 0.8 μm at 0 h; 98.8 % & 2.3 μm at 1 h) in comparison with conventional sintering (87.4 % & 0.8 μm at 0 h; 98.3 % & 2.1 μm at 1 h) for same sintering (dwell) duration.

Evaluation of susceptor-assisted microwave-sintering-produced Al-Y2O3 composite material's compression and reciprocating wear performance

The manufacturing of a composite material out of aluminium (Al) and yttrium oxide (Y2O3) was achieved via the use of the microwave hybrid sintering method, which is an energy-efficient and eco-friendly production process. Compression and dry reciprocating wear tests are conducted on the manufactured material to learn more about the function of reinforcing particles in composites. The exothermic temperature marginally shifts (1 °C) when Y2O3 reinforcement is added to the Al matrix. The average micro hardness of composites with 2 wt.% Y2O3 is 43 Hv, which is an improvement over the previous value of 36 Hv. In addition, the composite material’s compressive strength improved by 38.78% in comparison to that of Al. In a dry reciprocating wear test, the composite material with 2 wt% Y2O3 nanoparticle showed a reduction in mass loss of 20%. The even distribution of reinforcing components throughout the material and the advent of intermetallic Al3Y in composites are likely responsible for this.

Effects of Microwave Hybrid Sintering Methods and Nano-HfC Content on Mechanical Properties and Microstructure of TiB2-Based Cermets

Effects of Microwave Hybrid Sintering Methods and Nano-HfC Content on Mechanical Properties and Microstructure of TiB2-Based Cermets

Microwave hybrid and conventional sintering of Al2O3 and Al2O3/ZrO2 multilayers fabricated by aqueous tape casting

AbstractIn this study, microwave hybrid sintering and conventional sintering of Al2O3‐ and Al2O3/ZrO2‐laminated structures fabricated via aqueous tape casting were investigated. A combination of process temperature control rings and thermocouples was used to measure the sample surface temperatures more accurately. Microwave hybrid sintering caused higher densification and resulted in higher hardness in Al2O3 and Al2O3/ZrO2 than in their conventionally sintered counterparts. The flexural strength of microwave‐hybrid‐sintered Al2O3/ZrO2 was 70.9% higher than that of the conventionally sintered composite, despite a lower sintering temperature. The fracture toughness of the microwave‐hybrid‐sintered Al2O3 increased remarkably by 107.8% despite a decrease in the relative density when only 3 wt.% t‐ZrO2 was added. The fracture toughness of the microwave‐hybrid‐sintered Al2O3/ZrO2 was significantly higher (247.7%) than that of the conventionally sintered composite. A higher particle coordination and voids elimination due to the tape casting and the lamination processes, the microwave effect, the stress‐induced martensitic phase transformation, and the grain refinement phenomenon are regarded as the main reasons for the mentioned outcomes.

Strategic Design and Analysis of Energy Storage and ME Applications of Low Temperature Hybrid Microwave Sintered Electroceramic Composites

The magnetoelectric particulate (0–3) composites (x) (PbZr0.52Ti0.48O3)-(1 – x) (Y3Fe5O12) (where, x = 0.25, 0.5, 0.75) are synthesized by the solid-state hybrid microwave sintering technique. Multiferroic bulk ceramic capacitors have attracted immense interest in energy storage devices for pulsed power systems because of their superior temperature resistance and environment-friendliness. Even though significant attempts have been made to create massive magneto electric (ME) bulk ceramics for various applications, it still needs to be practical or scientifically recommended for investigating novel material systems with multiple applications. In this work, coexistence of optimized composition of ferroelectric and ferromagnetic continents is proposed to achieve multiple applications like energy storage and energy conversion (magnetoelectric). Ceramics made of PZT and YIG are chosen to demonstrate multiple applications that are both possible and practical. Encouragingly, a moderate energy storage efficiency of (33%) and good ME of (1.9 mv) are achieved in PZT0.75–YIG0.25 and PZT0.5–YIG0.5 bulk ceramics. Most importantly, the present work provides essential information for designing a series of ME compositions for next-generation energy storage and magnetoelectric applications.

Hybrid microwave sintering of Zirconia Toughened Alumina in a multimode cavity – Influence of the content of 3 mol% yttria stabilized zirconia and sintering configurations

MW sintering is a sintering process in which samples directly heat by absorption of the electromagnetic field, leading to a fast volume heating. Thus, the materials are heated due to their own dielectric properties. Zirconia Toughened Alumina (ZTA) is of particular interest for MW sintering because of the difference of dielectric properties between alumina and zirconia. In this study, ZTA pellets with different volume fractions of zirconia were sintered in a MW multimode cavity with different sintering cells, i.e., with or without susceptor. These experiments show that all the samples were densified whatever the configuration. But the evolution of power and temperature vs time during the sintering cycle shows a better heating capability when the volume fraction of zirconia increases. The influence of the material to heat is more visible when sintering without susceptor. This was confirmed by other experiments, where the samples were heated by a constant incident power in a single-mode cavity.

Effect of the addition of ductile phase on mechanical properties of Alumina/nano SiC ceramic composite

ABSTRACT Silicon carbide reinforcement in Alumina possess better physical and mechanical properties at elevated temperature. However, addition of second phase ceramic to matrix enhances the strength and hardness but it moderately improves the fracture toughness. The reason is due to lack of plastic deformation. Addition of ductile metallic phase helps in bridging the advancing crack in the matrix. In the present study, Alumina/nano SiC ceramic composite is toughened by the addition of copper metal particles. The influence of these metallic particles on behavior and mechanical properties of Alumina/SiC ceramic composite have been studied. The composite is processed using microwave hybrid sintering technique (2800 Watt) for one hour at 1400℃ and 1500℃. After sintering, microstructure of sample, grain size, relative densification, hardness and toughness have been examined. Highest densification of 93% and hardness of 1590 HV is achieved at 1400℃ sintering temperature while highest fracture toughness of 3.9 MPa m1/2 is achieved at temperature of 1500℃ with coarsening of alumina grains. The ductile phase in ceramic has proven to be effective for better bonding. It creates ceramic-metal bonds, which act as a tiny metal matrix between ceramic particles and contribute to ductile phase toughening in developed (Alumina/5% nano SiC/5%Cu) ceramic composite.

Hybrid microwave sintering of a lunar soil simulant: Effects of processing parameters on microstructure characteristics and mechanical properties

Hybrid microwave sintering is considered a promising method to produce densified components using in-situ resources for lunar construction. This study aimed to examine the effects of primary microwave sintering parameters on the densification, microstructure evolution, and mechanical properties of a lunar soil simulant and analyzed the processing-microstructure-properties relationship. The experimental design was based on the Taguchi method, where temperature, dwell time, and heating rate were regarded as the primary design factors. Density measurements presented the porosity of microwave-sintered specimens ranging from 8.5 % to 11.5 %. Chemical and microstructural characterization was integrated and showed three identical mineral phases appeared at different sintering conditions. Nanoindentation was used to determine nanomechanical properties of microstructural components and subsequent effective stiffness via homogenization technique. Uniaxial compressive strength of sintered specimens was also measured. The sintering design parameters in the range attempted significantly affected microstructural characteristics, while no major changes in the chemical–mechanical properties of phases occurred. Taguchi analysis implied that microstructural evolution is predominantly affected by the sintering temperature, whereas the other two factors (i.e., dwell time and heating rate) were not significant. The fundamental understanding from this study can improve the design of hybrid microwave sintering to densify lunar soils for future lunar construction.

Microwave hybrid sintering of 0.95(Mg0.95Zn0.05)TiO3-0.05CaTiO3 ceramics and its microwave dielectric properties

Microwave dielectric ceramic powder of 0.95(Mg0.95Zn0.05)TiO3-0.05CaTiO3 (MCT) has been prepared by solid-state reaction method through single-step calcination at 1150 °C. The green bodies prepared from the calcined powder have been sintered by conventional, susceptor-aided, and hybrid microwave sintering techniques followed by annealing. XRD of calcined and sintered ceramics show (Mg,Zn)TiO3 as a major phase with CaTiO3 as a minor secondary phase. Fractographs of fired ceramics obtained by SEM show similar features in conventional and hybrid microwave types of sintering. Microwave dielectric properties such as relative permittivity(εr), temperature coefficient of resonant frequency(τf), and unloaded quality factors (Qu) for conventional sintered at 1325 °C for 4 h are—εr~19.8, τf< –6 ppm/°C and Qu.f 69,600 GHz at 6 GHz. Ceramics obtained through susceptor-aided microwave sintering at 1325 °C for 4 h show poor fired density. But ceramics got by microwave-hybrid sintering (resistive + microwave) at the same temperature show εr~20.6, Qu.f~81,600 GHz at 6 GHz and τf~−6.9 ppm/°C. The effect of hybrid microwave sintering on the dielectric properties of MCT ceramics is found to be more subtle than microstructural.

Effect of Kaolin Geopolymer Ceramics Addition on the Microstructure and Shear Strength of Sn-3.0Ag-0.5Cu Solder Joints during Multiple Reflow.

Solder interconnection in three-dimensional (3D) electronic packaging is required to undergo multiple reflow cycles of the soldering process. This paper elucidates the effects of multiple reflow cycles on the solder joints of Sn-3.0Ag-0.5Cu (SAC305) lead (Pb)-free solder with the addition of 1.0 wt.% kaolin geopolymer ceramics (KGC). The samples were fabricated using powder metallurgy with the hybrid microwave sintering method. Apart from using conventional cross-sectioned microstructure imaging, advanced synchrotron real-time in situ imaging was used to observe primary IMC formation in SAC305-KGC solder joints subjected to multiple reflow soldering. The addition of KGC particles in SAC305 suppressed the Cu6Sn5 IMC’s growth as primary and interfacial layers, improving the shear strength after multiple reflow soldering. The growth rate constant for the interfacial Cu6Sn5 IMC was also calculated in this study. The average growth rate of the primary Cu6Sn5 IMCs decreased from 49 µm/s in SAC305 to 38 µm/s with the addition of KGC particles. As a result, the average solidified length in the SAC305-KGC is shorter than SAC305 for multiple reflow soldering. It was also observed that with KGC additions, the growth direction of the primary Cu6Sn5 IMC in SAC305 changed from one growth to two growth directions. The observed results can be attributed to the presence of KGC particles both at grains of interfacial Cu6Sn5 IMCs and at the surface of primary Cu6Sn5 IMC.

Zone-specific temperature distribution, densification trajectory and grain-growth kinetics of microwave-hybrid-sintered and conventionally sintered Al2O3 slip casts

ABSTRACT A comparative study on the microwave hybrid sintering and conventional sintering of Al2O3 slip casts is reported to observe temperature distribution, grain-growth kinetics and densification in different regions of samples. It was found that the microwave hybrid sintering resulted in a significantly lower temperature difference between the surface and the center as compared to that in conventional sintering. Remarkably, in the microwave-hybrid-sintered samples, the estimated activation energy for grain growth at the center was approximately 27% lower than that at the surface in the conventionally sintered samples. The grain-growth rate in microwave hybrid sintering was more than three times higher at the sample center ((62.07 ± 0.06) × 10–21 m3/s) than at the sample surface in the conventional sintering ((18.75 ± 0.11) × 10–21 m3/s). The volume diffusion for grain growth was found to be the most effective mechanism in all samples, irrespective of the sintering technique and point of observation. It is suggested that the heat-flux, as well as the microwave effect and influence of surface charge due to the electric field of the field-assisted process were the reasons for these outcomes.

Interfacial characterization and its influence on the corrosion behavior of Mg-SiO2 nanocomposites

In this work, the corrosion behavior of Mg-SiO2 nanocomposites, fabricated by powder metallurgy coupled with hybrid microwave sintering and subsequent hot extrusion, was investigated using electrochemical, hydrogen evolution and weight loss measurements. Localized intergranular corrosion behavior was analyzed based on microstructural characteristics, which were characterized by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and high-resolution transmission electron microscopy (HRTEM). In particular, copious numbers of Mg/MgO misfit dislocations were identified at the interface between the matrix Mg and SiO2 nanoparticles; indeed, first principles calculations revealed that the MgO/Mg interfaces were relatively weakly bonded as compared to the close-packed interfacial Mg(0001)//MgO(111) structure. Using geometrical phase analysis of the HRTEM images to determine the lattice strains in the Mg/MgO interfacial area, we conclude that the highly strained and weakly bonded Mg/MgO interfaces act to promote significant localized dissolution and thus play a dominant role in intensifying intergranular corrosion in these nanocomposites.

Zinc oxide nanorods effect in micro structural and mechanical characteristics of aluminium composite material

In the present study, aluminium zinc oxide (Al-ZnO) nanorods composites with 3.5 and 5 wt% ZnO in Al were manufactured using powder metallurgy and microwave hybrid sintering. A fairly uniform reinforcement distribution and clear interface was perceived in the micro structural and energy dispersive spectroscopy analysis of composite material. It was observed from XRD analysis that no secondary (intermetallic) phase of Al and ZnO were present in the composite material. The simultaneous thermal analysis of the composites was done to understand the variation in the exothermic peak temperature and weight change percentage of composite material. The developed composite material with 5 wt% ZnO exhibited promising results in terms of micro-hardness (∼2 times), nano hardness (∼3.5 times) and elastic modulus (∼1.9 times) greater value compared to Al. The increased addition of ZnO nanorods in aluminium shows enrichment in properties rendering the material suitable for different engineering applications.

Multi-physics simulation study of microwave hybrid sintering of aluminium and mechanical characteristics

In the present study, a finite element model of microwave hybrid sintering along with experimental validation was developed. Multiphysics simulation at 2.45 GHz was carried out to understand the heat transfer behaviour and electric field distribution during the microwave hybrid sintering process. The proposed work presents an innovative and integrated approach for sintering aluminium utilizing microwave energy. Comparison with numerical simulation results and experimental data of temperature variation during microwave hybrid sintering was done. The maximum error predicted by the simulation model and experimental investigation for temperature variation in sintering was found to be within 10%. The X-ray diffraction analysis, relative density and microstructure analysis of the sintered aluminium was done to gain an insight into the material characteristics. The microhardness and nanoindentation tests were carried out to determine the hardness and elastic modulus. Good consolidation behaviour of aluminium with an achieved density of 0.9774, microhardness of 36Hv, nano-hardness as 0.5664 GPa and 57.301 GPa elastic modulus value has been observed. The study will develop a cogent link between the numerical model and experimental data for microwave hybrid sintering.

Aluminum Yttrium Oxide Metal Matrix Composite Synthesized by Microwave Hybrid Sintering: Processing, Microstructure and Mechanical Response

Aluminum Yttrium Oxide Metal Matrix Composite Synthesized by Microwave Hybrid Sintering: Processing, Microstructure and Mechanical Response

Dielectric behaviour of BZT-BCT nano pseudobinary system near TCP-assisted morphotopic phase boundary

The present study investigates the comparative dielectric studies in nano pseudobinary system synthesized by conventional and hybrid microwave sintering. The material was formed near Tri Critical Point (TCP)-assisted Morphotropic Phase Boundary (MPB) region from equal weight percentage of Lead Zirconate Titanate (BZT) and Barium Calcium Titanate (BCT) employing high energy ball milling. In the temperature dependent LCR study, a diffused phase transition (DPT) behaviour was identified for both conventional and hybrid microwave sintered samples. In each case, modified Currie-Weiss relation indicates an anomaly in the paraelectric state. Further, another approach using macroscopic composition-fluctuation model also exhibits the anomalous behaviour. Universal dielectric response (UDR) demonstrates that such behaviour is created by a temperature assisted relaxation phenomena by the formation of oxygen vacancies. Beyond 260 °C, microwave sintering creates more oxygen vacancies across grain boundary region as compared to the conventional sintering and in turn plays the key role for enhanced dielectric permittivity.

Effect of Variations in Microwave Processing Temperatures on Microstructural and Mechanical Properties of AA7075/SiC/Graphite Hybrid Composite Fabricated by Powder Metallurgy Techniques

Due to the demand in present industrial, aerospace, defense sectors for lightweight high-performance aluminum (Al) particle-reinforced metal matrix composites, the advancement of techniques to fabricate these composites with superior mechanical properties have gained technological interest in the modern world. In this direction, SiC and graphite reinforced AA7075 matrix composite material has been fabricated in this study, through hybrid microwave sintering techniques. The microwave sintering temperatures for the optimized volume fraction composition of AA7075/SiC/graphite hybrid composite has been varied from 400 to 550 °C with a step value of 50 °C. The obtained results showed a superior improvement in the mechanical properties for microwave sintered composites as compared to the conventionally sintered composites. Mechanical properties are found to show increasing trend with increasing microwave sintering temperatures up to 500 °C, after that, a downfall is observed in their mechanical properties, which can be attributed to the increased average grain size of the composite at 550 °C. Selection of SiC as primary reinforcement material helped in achieving high mechanical strengths, and through microwave sintering, an increment of 37.2% in tensile, 26.6% in compression, and 16.5% in hardness is achieved. From this investigation, it is also observed that the selection of materials that shows high response to microwaves helps in achieving the enhanced mechanical properties for the hybrid composites processed by microwave sintering techniques.