Surface Dissolution of Hydroxyapatite Prepared by Microwave Sintering

2007 ◽  
Vol 330-332 ◽  
pp. 227-230
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Kyu Hong Hwang ◽  
Jong Kook Lee
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Heating Rate ◽  
Microwave Sintering ◽  
Starting Material ◽  
Dissolution Behavior ◽  
Distilled Water ◽  
Sintering Process ◽  
Conventional Sintering ◽  
Boundary Dissolution

The aim of this study was to prepare dense hydroxyapatite (HA) by microwave sintering and to evaluate the dissolution behavior in distilled water. Commercially-obtained HA powders having Ca/P ratio of 1.67 were used as a starting material. The as-received powder of granular type consists of nano-sized particles. Microwave sintering was operated at 1200°C for 5 min with a heating rate of 50°C/min. Microwave sintering process reduced grain size of HA, compared with the case of conventional sintering. During the immersion in distilled water for 3-14 days, grain boundary dissolution occurred and the dissolution extended into the bulk following this path. As a result, particles were separated from the structure leaving micron-scale defects.

Unconventional Methods of Sintering Inconel 718 MIM Samples

2016 ◽  
Vol 716 ◽  
pp. 830-839
Author(s):  
Olivier Dugauguez ◽  
Jose Manuel Torralba ◽  
Thierry Barrière ◽  
Jean Claude Gelin
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Heating Rate ◽  
Inconel 718 ◽  
Fine Particle ◽  
Alloy Powder ◽  
Microwave Sintering ◽  
Conventional Sintering ◽  
Unconventional Methods ◽  
Super Alloy

In this investigation, three different ways of sintering Inconel 718 MIM samples are compared. The conventional way of sintering in a furnace will be compared to FAHP and microwave sintering. The difficulty of these two methods is to be able to control the shrinkage of the sample and so its shape. These methods have yet not been investigated with a super alloy powder and so, the effects of a high sintering rate on a MIM sample. By accelerating the sintering kinetics, the thermal behavior may be modified. Hence, the behavior of the Inconel 718 sintered by field assisted and microwave sintering has been investigated. The sintered samples were all injected from a feedstock composed of a fine particle Inconel powder and a binder principally composed of CAB and PEG. They were debinded into water for 24h and put in a furnace at 500°C during 2 hours. The heating rate of the furnace was set to 5°C/min until 1290°C during 2 hours. The heating rate of the FAHP was set to 50°C/min until 1250°C during 15 minutes. The microwave samples were sintered around 1300°C during 1 hour, the temperature was increased progressively by steps of 100°C. The effects of the different process on the microstructure and the mechanical properties are then compared. There was no difference in distribution of pores between the conventional sintering and the FAHP sintering but a finer grain size showed better hardness. The microwave sintering of a MIM sample is more complex and the best properties were not obtained.

Nanostructured Hydroxyapatite by Microwave Sintering

2008 ◽  
Vol 8 (2) ◽  
pp. 944-948 ◽  
Author(s):  
Dong Seok Seo ◽  
Kyu Hong Hwang ◽  
Jong Kook Lee
Keyword(s):  
Grain Size ◽  
Microwave Sintering ◽  
Milled Powder ◽  
Xrd Analysis ◽  
Molar Ratio ◽  
Sintering Process ◽  
Dense Microstructure ◽  
Uniform Microstructure ◽  
Nanocrystalline Particles ◽  
Conventional Sintering

In this work, nanostructured HA ceramics with dense microstructure were prepared by microwave sintering process and their microstructures were compared with the case of conventional sintering. Commercially obtained HA powder with Ca/P molar ratio of 1.67 was used as a starting material. The powder of granular type consists of nanocrystalline particles of 20–30 nm in size. The as-received HA powder or the powder calcined at 800 °C, followed by ball-milling was used for the preparation of HA disks. Microwave sintering was conducted at 1200 °C for 5 min with a heating rate of 50 °C/min. HA ceramics with the sintered densities of approximately 96–97% of the theoretical were obtained. XRD analysis showed that all detectable peaks are identical to pure hydroxyapatite. The HA sintered body made of calcined and ball-milled powder showed uniform microstructure with grain size of 300–400 nm and with finer sub-grains of 30–40 nm.

Sintering Process of Nd:YAG Transparent Ceramic

2013 ◽  
Vol 281 ◽  
pp. 475-479
Author(s):  
Bo Wang ◽  
Quan Xi Cao ◽  
Guang Xu ◽  
Sen Tian
Keyword(s):  
Grain Size ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Crystal Structures ◽  
Heating Rate ◽  
Optical Transmittance ◽  
Sintering Process ◽  
X Ray ◽  
Polycrystalline Ceramics ◽  
Scanning Electron

1.0at% Nd:YAG polycrystalline ceramics were sintered at 1420°C, 1500°C, 1600°C and 1730°C respectively by different heating rate (1°C/min and 5°C/min). The crystal structures were indexed by X-ray diffractometer (XRD). The microstructure and the grain size of the samples were characterized by scanning electron microscope (SEM). The optical transmittance spectra of the samples were measured using V-570 UV spectrophotometer. The sintering process of Nd:YAG ceramics and the effect of heating rate on the microstructure of samples have been investigated.

Microwave Processing of Ceramics

2006 ◽  
Vol 45 ◽  
pp. 857-862 ◽  
Author(s):  
Isabel K. Lloyd ◽  
Yuval Carmel ◽  
Otto C. Wilson Jr. ◽  
Geng Fu Xu
Keyword(s):  
Thermal Conductivity ◽  
Grain Size ◽  
Heating Rate ◽  
Thermal Gradients ◽  
Heating Rates ◽  
Volumetric Heating ◽  
Wide Range ◽  
Conventional Sintering ◽  
Atmosphere Control ◽  
Very High

Microwave (MW) processing is advantageous for processing ceramics with tailored microstructures. Its combination of volumetric heating, a wide range of controlled heating rates, atmosphere control and the ability to reach very high temperatures allows processing of 'difficult' materials like high thermal conductivity AlN and AlN composites and microstructure control in more readily sintered ceramics such as ZnO. MW sintering promotes development of thermal conductivity in AlN (225 W/mK) and its composites (up to 150W/mK inAlN-TiB2 and up to 129 W/mK in AlN-SiC when solid solution is avoided). In ZnO, heating rate controls sintered grain size. Increasing the heating rate from 5°C/min. to 4900°C decreases grain size from ~10 μm (comparable to conventional sintering of the same powder) to nearly the starting particle size (~ 1μm). Microstructural uniformity increases with sintering rate since ultra-rapid MW sintering minimizes the development of thermal gradients due to heat loss.

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.

scholarly journals Tungsten Matrix Composite Reinforced with CoCrFeMnNi High-Entropy Alloy: Impact of Processing Routes on Microstructure and Mechanical Properties

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 992 ◽  
Author(s):  
P. V. Satyanarayana ◽  
R. Sokkalingam ◽  
P. K. Jena ◽  
K. Sivaprasad ◽  
K. G. Prashanth
Keyword(s):  
Heating Rate ◽  
Microwave Sintering ◽  
Oxide Phase ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Mechanically Alloyed ◽  
High Entropy ◽  
Plasma Sintering ◽  
Conventional Sintering ◽  
Spark Plasma

Tungsten heavy alloy composite was developed by using novel CoCrFeMnNi high-entropy alloy as the binder/reinforcement phase. Elemental tungsten (W) powder and mechanically alloyed CoCrFeMnNi high-entropy alloy were mixed gently in high energy ball mill and consolidated using different sintering process with varying heating rate (in trend of conventional sintering < microwave sintering < spark plasma sintering). Mechanically alloyed CoCrFeMnNi high-entropy alloy have shown a predominant face-centered cubic (fcc) phase with minor Cr-rich σ-phase. Consolidated tungsten heavy high-entropy alloys (WHHEA) composites reveal the presence of Cr–Mn-rich oxide phase in addition to W-grains and high-entropy alloys (HEA) phase. An increase in heating rate restricts the tungsten grain growth with reduces the volume fraction of the Cr–Mn-rich phase. Finally, spark plasma sintering with a higher heating rate and shorter sintering time has revealed higher compressive strength (~2041 MPa) than the other two competitors (microwave sintering: ~1962 MPa and conventional sintering: ~1758 MPa), which may be attributed to finer W-grains and reduced fraction of Cr–Mn rich oxide phase.

Ultralow dielectric constant nickel–zinc ferrites using microwave sintering

2003 ◽  
Vol 18 (10) ◽  
pp. 2292-2295 ◽  
Author(s):  
Ramesh Peelamedu ◽  
Craig Grimes ◽  
Dinesh Agrawal ◽  
Rustum Roy ◽  
Purushotham Yadoji
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
High Frequency ◽  
Microwave Field ◽  
Domain Walls ◽  
Microwave Sintering ◽  
Starting Material ◽  
Nickel Zinc ◽  
Magnetic And Dielectric Properties

Ultralow dielectric constant values were measured on Ni–Zn ferrites prepared using Fe2O3 as a starting material and sintered in a microwave field. Significant differences in microstructure, magnetic, and dielectric properties were observed between microwave-sintered Ni–Zn ferrites prepared using Fe3O4 (T34) and those starting with Fe2O3 (T23) ingredients. Higher magnetization values observed in T23 ferrite are attributed to large grain size, possibly containing abundant domain walls and the presence of fewer Fe2+ ions. The ultralow dielectric constant values observed on T23 ferrites show that this procedure is highly suitable to prepare Ni–Zn ferrites for high-frequency switching applications.

Preparation of Rare-Earth Permanent Magnetic Strontium Ferrite by Microwave Sintering Process

2010 ◽  
Vol 177 ◽  
pp. 264-268 ◽  
Author(s):  
Han Han Jiang ◽  
Ming Lin Jin ◽  
Zhan Yong Wang ◽  
Qi Zhong Chen ◽  
Hui Chun Qian
Keyword(s):  
Rare Earth ◽  
Microwave Sintering ◽  
Magnetic Domain ◽  
Strontium Ferrite ◽  
Green Body ◽  
Sintering Process ◽  
Wet Milling ◽  
Conventional Sintering ◽  
Degree Of Orientation ◽  
Sintering Method

In this paper, the green body was prepared by pre-roasted material of strontium ferrite, adding 0.2 to 9% the rare earth additive, by wet milling and forming into pellets Φ30×10 mm under magnetic field. Then, the green body was sintered separately by microwave sintering (MS) method and conventional sintering (CS) technique. The results showed that: the strontium ferrite samples with the same magnetic properties Br and (BH) max were 420 ± 10mT and 33.0 ± 2 kJ/m 3) were synthesized by microwave sintering (MS) method against conventional sintering method, the sintering temperature and time were reduced 150~300°C and 5~6h. Therefore, microwave sintering method will significantly decrease energy consumption. Further analysis revealed that the major improvements in microwave sintering were the material microstructure, the grain size was significantly reduced, the magnetic domain short-range order was increased so that the degree of orientation was increased, and although the fusion was existed between grains, the grain boundaries did not disappear.

Comparative Study of Al-TiB2 Composite Fabricated by Different Powder Metallurgical Methods

2018 ◽  
Vol 6 (7) ◽  
pp. 178
Author(s):  
Purushottam Kumar ◽  
Shreyanshu Parhi ◽  
Somak Datta
Keyword(s):  
Powder Metallurgy ◽  
Comparative Study ◽  
Microwave Sintering ◽  
Matrix Composites ◽  
Sintering Process ◽  
Mechanical And Tribological Properties ◽  
New Class ◽  
Conventional Sintering ◽  
Machine Parts ◽  
Aluminium Metal

Aluminium Metal Matrix Composites (AMMCs) are the new class of materials substituting many industrial materials. It is due to its superior qualities compared to conventional materials.  AMMCs has found a versatile application because it has aluminium in matrix phase hence light in weight and also it can acquire different properties as per reinforcements used. Sintering is one of the prominent methods used to manufacture AMMCs. Sintering process is used in Powder Metallurgy in which small powdered particles are heated to bond together. The process enhances the strength as well as other mechanical and tribological properties. The technology enables us to shape materials difficult to machine, parts with complex geometries, materials having high melting point, parts with close dimensional tolerances, or to combine different materials which is not possible with any other process. The most important part is that the density of the product can be controlled according to the requirements and thus self-lubricating and wear-resistant parts are possible.  The present study has attempted to see if TiB2 can be used as reinforcement in AMMCs produced through powder metallurgy route and the changes in the properties of AMMCs by the different sintering methods adopted. The compacted preforms of varying compositions of reinforcement were prepared and sintered through three different methods i.e. Microwave sintering, Conventional sintering and Hot-pressing to study the changes in the properties.  A comparative study has been done between the three sintering methods to see the limitations and scope for improvement.

Microwave Sintering of ZnO Varistor Ceramics

1992 ◽  
Vol 269 ◽  
Author(s):  
Lionel M. Levinson ◽  
Holly A. Comanzo ◽  
William N. Schultz
Keyword(s):  
Grain Boundary ◽  
Microwave Sintering ◽  
Boundary Effects ◽  
Electrical Behavior ◽  
Careful Evaluation ◽  
Electronic Ceramics ◽  
Zno Varistor ◽  
Conventional Sintering ◽  
Systematic Shift ◽  
Zno Varistors

ABSTRACTZnO varistors are electronic ceramics whose electrical behavior is dominated by grain boundary effects. A careful evaluation of the effect of microwave sintering compared to conventional sintering revealed no significant differences between varistor devices processed by these two methods. A slight apparent enhancement of grain growth was observed for microwave processing, but further evaluation of this effect leads us to believe that it arises from a small systematic shift in temperature derived from the different experimental configurations.

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