scholarly journals Microwave Sintering of Boron Carbide

1988 ◽  
Vol 124 ◽  
Author(s):  
J. D. Katz ◽  
R. D. Blake ◽  
J. J. Petrovic ◽  
H. Sheinberg
Keyword(s):  
Grain Size ◽  
Boron Carbide ◽  
Microwave Radiation ◽  
Hot Pressing ◽  
Microwave Sintering ◽  
Theoretical Density ◽  
Energy Usage ◽  
Average Grain Size

ABSTRACTBoron carbide has been sintered to 95% of theoretical density in less than 12 minutes without the use of sintering aides by heating to 2000°C with 2.45 GHz microwave radiation. An average grain size of about 20 μm resulted. Twins and microcracking were present in the microstructure. Energy usage for microwave sintering was found to be 18% less than for inductive hot-pressing.

Nanostructure Evolution of ZnO in Ultra-fast Microwave Sintering

2011 ◽  
Vol 691 ◽  
pp. 65-71 ◽  
Author(s):  
Rodolfo F. K. Gunnewiek ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Grain Size ◽  
Zinc Oxide ◽  
Grain Growth ◽  
Microwave Sintering ◽  
High Heating Rate ◽  
Heating Rates ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Holding Temperature

Grain growth is inevitable in the sintering of pure nanopowder zinc oxide. Sintering depend on diffusion kinetics, thus this growth could be controlled by ultra-fast sintering techniques, as microwave sintering. The purpose of this work was to investigate the nanostructural evolution of zinc oxide nanopowder compacts (average grain size of 80 nm) subjected to ultra-rapid microwave sintering at a constant holding temperature of 900°C, applying different heating rates and temperature holding times. Fine dense microstructures were obtained, with controlled grain growth (grain size from 200 to 450nm at high heating rate) when compared to those obtained by conventional sintering (grain size around 1.13µm), which leads to excessively large average final grain sizes.

High density BaCeO3 ceramics sintered using microwave irradiation

2005 ◽  
Vol 906 ◽  
Author(s):  
Alexander Sergeevitch Vanetsev ◽  
Andrei Vladimirovitch Orlov ◽  
Yurii Dmitrievitch Tretyakov
Keyword(s):  
Grain Size ◽  
High Power ◽  
Microwave Field ◽  
Microwave Sintering ◽  
Barium Cerate ◽  
High Power Microwave ◽  
High Power Microwaves ◽  
Thermal Fields ◽  
Average Grain Size ◽  
Power Microwave

AbstractThe goal of this work was to investigate the capabilities of high-power microwaves in manufacture of small-grained barium cerate ceramics. Having compared the samples sintered in the microwave and the thermal fields, we inferred that the microwave sintering occurs at far higher rates. It is also noteworthy that microwave sintering provides a record-breaking low temperature of barium cerate sintering (900°C). Having studied the effect of a microwave field on the microstructure of sintering products, we found that high-power microwave processing significantly reduces the average grain size of barium cerate ceramics.

Colloidal processing and mechanical properties of silicon carbide with alumina

1997 ◽  
Vol 12 (11) ◽  
pp. 3146-3157 ◽  
Author(s):  
Yoshihiro Hirata ◽  
Kouji Hidaka ◽  
Hiroaki Matsumura ◽  
Yasuo Fukushige ◽  
Soichiro Sameshima
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Room Temperature ◽  
Size Dependence ◽  
Theoretical Density ◽  
Aspect Ratios ◽  
Median Size ◽  
Average Grain Size ◽  
Sintering Mechanisms ◽  
Ph Range

Submicrometer-sized SiC coated with SiO2 of 0.4–1.8 wt.% and α–Al2O3 powder of median size 0.2 μm were mixed in aqueous solutions in the pH range 3.0–10.0. The SiC/Al2O3 (4.3–6.9 wt. %) powders were consolidated by filtration through gypsum molds and hot-pressed at 1600°–2040 °C under a pressure of 39 MPa. These compacts were densified to near the theoretical density at 1700°–1800 °C. The sintering mechanisms are discussed based on the analysis of shrinkage curves of SiC/Al2O3 compacts during hot-pressing. The equiaxed SiC grains grew with low aspect ratios below 1800 °C and changed to plate-like grains at 1900 °C. The fracture toughness of SiC as a function of average grain size reached a maximum of 5 Mpa · m0.5 at 2.5 μm grains of low aspect ratios of 1–2. The flexural strengths at room temperature were 230–430 MPa in the SiC above 98% of the theoretical density and showed a similar grain size dependence.

Microstructure and Electrical Properties of BaTiO3-Based PTC Ceramics Prepared from Nanopowders

2008 ◽  
Vol 368-372 ◽  
pp. 456-458
Author(s):  
Huan Liu ◽  
Shu Ping Gong ◽  
Dong Xiang Zhou ◽  
Chun Fang Cheng ◽  
Zhi Ping Zheng ◽  
...  
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Curie Temperature ◽  
Hydrothermal Method ◽  
Hydrothermal Treatment ◽  
Theoretical Density ◽  
Ceramic Samples ◽  
Average Grain Size ◽  
Donor Dopant ◽  
Cubic Structure

Dense PTC ceramics were prepared with BaTiO3 nanopowders synthesized by hydrothermal method. BaCO3 and Ti(OC4H9)4 were used as barium and titanium sources, and Y(NO)3·6H2O as the donor dopant respectively. The average grain size of the powders obtained after hydrothermal treatment at 160°C for 9h was about 30nm with cubic structure. Mn(NO3)2 was introduced to the as-prepared nanopowders in order to improve the PTC effect. After sintered at 1280°C, the PTC ceramic samples exhibited sufficient resistance jump ratio(1.086×103) around Curie temperature, the density of which was 5.81g/cm3(96.5% of the theoretical density).

scholarly journals Crystal Diffraction Techniques Were Used to Investigate the Structural Properties of Some Aluminum Alloys.

2022 ◽  
Vol 961 (1) ◽  
pp. 012018
Author(s):  
Sukaina Iskandar Yusuf ◽  
Mohammed Muhana Meteab ◽  
Abdulkader Ahmed Annaz
Keyword(s):  
Grain Size ◽  
Aluminum Alloys ◽  
Structural Properties ◽  
Spherical Shape ◽  
Sem Analysis ◽  
Theoretical Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Grain Size ◽  
Radiation Shields

Abstract Due to the importance of these alloys in the manufacture of aircraft, coatings, radiation shields, and electronic circuits, the study’s objectives include investigating previously unstudied structural properties of some aluminum alloys, alloy A (Al-Zn-Mg-Ti) and alloy B (Al-Zn-Mg-Mn) were prepared using the casting method, and their structural properties were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques (granular size and theoretical density). The results of analyzing the X-ray diffraction data and determining the phases formed on the two alloys after matching them with the international standard cards (JCPDS) revealed that it is polycrystalline, with structures (cubic and hexagonal) on alloy A and structures (cube, hexagonal, and anorthic) on alloy B. The results revealed that the average grain size estimated by the Debye-Scherer method is less than that estimated by the Williamson-Hall method, and that the grain size of alloy A is less than that of alloy B due to the presence of titanium in alloy A’s composition, which works to reduce particle size. The theoretical density of Alloy A and B that was used in X-ray diffraction was calculated. SEM analysis of the spherical shape of the grains on the surfaces of alloys A and B revealed that the average grain size on the surface of alloy A is smaller than on the surface of alloy B, which is consistent with the results of XRD analyses.

scholarly journals Microwave sintering of nano size powder β-TCP bioceramics

2014 ◽  
Vol 46 (2) ◽  
pp. 185-193 ◽  
Author(s):  
B. Mirhadi
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tricalcium Phosphate ◽  
Microwave Sintering ◽  
Calcium Nitrate ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
Precipitation Process ◽  
Average Grain Size ◽  
Nano Size

A nano sized beta tricalcium phosphate (?-TCP) powder was conventional sintered (CS) and microwave sintered (MW), in order to obtain dense ?-TCP ceramics. In this work the effect of microwave sintering conditions on the microstructure, phase composition and mechanical properties of materials based on tricalcium phosphate (TCP) was investigated by SEM (scanning electron microscopy)and XRD(X-ray diffraction) and then compared with conventional sintered samples. Nano-size ?-TCP powders with average grain size of 80 nm were prepared by the wet chemical precipitation method with calcium nitrate and diammonium hydrogen phosphate as calcium and phosphorus precursors, respectively. The precipitation process employed was also found to be suitable for the production of submicrometre ?-TCP powder in situ. The ?-TCP samples microwave (MW) sintered for 15 min at 1100?C, with average grain size of 3?m, showed better densification, higher density and certainly higher hardness than samples conventionally sintered for 2 h at the same temperature. By comparing sintered and MW sintered ?-TCP samples, it was concluded that MW sintered ?-TCP samples have superior mechanical properties.

scholarly journals Microstructure and Properties of Ultrafine Cemented Carbides Prepared by Microwave Sintering of Nanocomposites

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 507
Author(s):  
Yanju Qian ◽  
Zhiwei Zhao
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Vickers Hardness ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Raw Material ◽  
Cemented Carbides ◽  
Microstructure And Mechanical Properties ◽  
Average Grain Size

Ultrafine cemented carbides were prepared by microwave sintering, using WC-V8C7-Cr3C2-Co nanocomposites as a raw material. The effects of sintering temperature and holding time on the microstructure and mechanical properties of cemented carbides were studied. The results show that the ultrafine cemented carbides prepared at 1300 °C for 60 min have good mechanical properties and a good microstructure. The relative density, Vickers hardness, and fracture toughness of the specimen reach the maximum values of 99.79%, 1842 kg/mm2 and 12.6 MPa·m1/2, respectively. Tungsten carbide (WC) grains are fine and uniformly distributed, with an average grain size of 300–500 nm. The combination of nanocomposites, secondary pressing, and microwave sintering can significantly reduce the sintering temperature and inhibit the growth of WC grains, thus producing superfine cemented carbides with good microstructure and mechanical properties.

scholarly journals Hydroxyapatite Nanopowder Synthesis with a Programmed Resorption Rate

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Dariusz Smoleń ◽  
Tadeusz Chudoba ◽  
Stanisław Gierlotka ◽  
Aleksandra Kedzierska ◽  
Witold Łojkowski ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Chemical Composition ◽  
Specific Surface ◽  
Surface Area ◽  
Microwave Radiation ◽  
Specific Surface Area ◽  
Resorption Rate ◽  
Average Grain Size ◽  
Degradation Test

A microwave, solvothermal synthesis of hydroxyapatite (HAp) nanopowder with a programmed material resorption rate was developed. The aqueous reaction solution was heated by a microwave radiation field with high energy density. The measurements included powder X-ray diffraction (PXRD) and the density, specific surface area (SSA), and chemical composition as specified by the inductively coupled plasma optical emission spectrometry technique (ICP-OES). The morphology and structure were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A degradation test in accordance with norm ISO 10993-4 was conducted. The developed method enables control of the average grain size and chemical composition of the obtained HAp nanoparticles by regulating the microwave radiation time. As a consequence, it allows programming of the material degradation rate and makes possible an adjustment of the material activity in a human body to meet individual resorption rate needs. The authors synthesized a pure, fully crystalline hexagonal hydroxyapatite nanopowder with a specific surface area from 60 to almost 240 m2/g, a Ca/P molar ratio in the range of 1.57–1.67, and an average grain size from 6 nm to over 30 nm. A 28-day degradation test indicated that the material solubility ranged from 4 to 20 mg/dm3.

Synthesis of Nano Amorphous In2O3 by Microwave Method and its Photocatalysis

2011 ◽  
Vol 299-300 ◽  
pp. 542-545 ◽  
Author(s):  
Wei Si ◽  
Jing Yuan Yu ◽  
Qiang Li
Keyword(s):  
Grain Size ◽  
Microwave Radiation ◽  
Ultrasonic Method ◽  
Microwave Method ◽  
Average Grain Size

Precursor In(OH)3 was synthesized by ultrasonic method with carbamide and indium salt, and was performed microwave radiation, then nano amorphous In2O3 was obtained. The structural and morphology of precursor and In2O3 were characterized by TG-DTA, XRD, TEM, etc. The results show that the In2O3 is nano amorphous with average grain size 12nm by microwave method. This paper discovered that nano amorphous In2O3 has good photocatalysis when we used it to degrade acidic black dye.

Effect of Sonochemical, Regenerative Sol Gel and Microwave Assisted Synthesis Techniques on the Formation of Dense Electrolytes and Porus Electrodes for All Perovskite IT-SOFCs

2006 ◽  
Author(s):  
Hrudananda Jena ◽  
B. Rambabu
Keyword(s):  
Grain Size ◽  
Electrical Transport ◽  
Microwave Sintering ◽  
Sol Gel ◽  
Microwave Assisted Synthesis ◽  
Electrical Transport Properties ◽  
Chemical Methods ◽  
Nano Crystalline ◽  
Average Grain Size ◽  
Wet Chemical

The influence of preparation techniques on the microstructure, grain-size and consequently on the electrical transport properties of the ABO3 structured materials used as electrode and electrolytes in all perovskite IT-SOFC were investigated. Nano-crystalline powders of La1-xMxGa1-yNyO3±δ (M = Sr,; x = −0.10 to 0.15; N = Mg; y = −0.10 to 0.15) (LSGM) as electrolyte, porous La0.8Sr0.2Co0.8Fe0.2O3±δ (LSCF) or LaNi1-xFexO3±δ (x = 0–0.5) (LNF) as cathode, La0.8Sr0.2Cr0.7Mn0.3O3±δ (LSCM) as anode and LaCrO3 or substituted LaCrO 3 as interconnect were synthesized by various wet chemical methods. The wet chemical methods like metal-carboxylate gel decomposition, hydroxide co-precipitation, sonochemical and regenerative sol-gel process followed by microwave sintering of the powders have been used. Microwave sintering parameters were optimized by varying sintering time, and temperature to achieve higher density of LSGM pellets. The phase pure systems were obtained at sintering duration of 30 min at 1200 °C. The XRD, HR-TEM, and SEM measurements revealed the average grain size of these perovskites was ∼ 22 nm range. The electrical conductivities of the compositions were measured by ac (5Hz–13MHz) and dc techniques. The conductivity of the sintered pellets was found to be ∼0.01–0.21 S/cm at 550–1000°C range for electrolyte and 1.5–100 S/cm at 25–1000°C for electrodes respectively. The effect of sonochemical, and regenerative sol-gel methods in processing large quantities of nano-crystalline perovskites with multi-element substitutions at A- and B-sites to achieve physico-chemical compatibility for fabricating zero emission all perovskite IT-SOFCs are reported in this paper.

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