scholarly journals Micro structural control of stabilized Zirconia ceramics (8YSZ) through modified conventional sintering methodologies

2010 ◽  
Vol 42 (1) ◽  
pp. 91-97 ◽  
Author(s):  
K. Rajeswari ◽  
Rajasekhar Reddy ◽  
U.S. Hareesh ◽  
B.P. Saha ◽  
R. Johnson
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Structural Control ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Stabilized Zirconia ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Slip Cast ◽  
Rate Controlled

Slip cast Y2O3 stabilized Zirconia (8YSZ) ceramics was subjected to Conventional Ramp and Hold (CRH), Rate Controlled (RCS) and Two Stage Sintering (2SS) methodologies. Sintered samples were characterized for their densities and grain size analysis by Scanning Electron Microscopy. The slip cast samples sintered by CRH and 2SS have achieved 98 - 99 % of theoretical densities while RCS samples have exhibited a low density of 97 %. The samples exhibited an average grain size of 2.64 ?m by 2SS sintering in comparison to 8.83 ?m in case of CRH and 3.45 ?m in case of RCS. Controlled pore growth associated with RCS, when compared to CRH methodology is mainly responsible for the relatively smaller grain size observed with RCS. A four fold decrease in grain size i.e. 2.64 ?m observed with the two step sintering can be attributed to the fact that the first heating step to high temperature of 1550?C for a shorter duration closes the porosity without significant grain growth. The second step at 1375?C for a longer period of time imparts densification with limited grain growth.

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.

Effect of rate controlled sintering on microstructure and electrical properties of ZnO doped with bismuth and antimony oxides

1997 ◽  
Vol 12 (9) ◽  
pp. 2447-2454 ◽  
Author(s):  
Gaurav Agarwal ◽  
Robert F. Speyer
Keyword(s):  
Grain Size ◽  
Liquid Phase ◽  
Grain Growth ◽  
Elevated Temperatures ◽  
Antimony Oxide ◽  
Second Phase ◽  
Dopant Content ◽  
Average Grain Size ◽  
Rate Controlled ◽  
Grain Boundary Pinning

Various rate controlled sintering (RCS) schedules were used on isostatically pressed particulate compacts of ZnO with Bi2O3 and Sb2O3 additives. For low additive content, smaller average grain sizes with more rapid RCS schedules were attributable to thermal schedules which minimized the time at elevated temperatures where grain growth could occur. β–Bi2O3, Zn7Sb2O12, and Zn2Sb3Bi3O14 phases formed during/after sintering. Elevated heat-treatment temperatures favored the formation of Zn7Sb2O12 and additional β–Bi2O3, while Zn2Sb3Bi3O14 was dominant in sintered samples where the RCS schedule did not result in temperatures in excess of 1100 °C. Zn2Sb3Bi3O14 precipitated during sintering, functioning as grain boundary pinning sites which impeded ZnO grain growth. Bismuth and antimony oxide-based liquid facilitated sintering at lower temperatures, which in turn resulted in decreased average grain size. Rapid RCS schedules for samples with low dopant content resulted in lower sintering temperatures, since time was not allowed for Zn2Sb3Bi3O14 precipitation to deplete the liquid phase. For higher dopant contents, liquid phase was adequately plentiful, wherein longer RCS schedules resulted in lower sintering temperatures. Increasing concentration of second phase generally fostered decreased grain size and attenuated the effect of thermal schedule on the microstructure. Electrical resistance and breakdown voltage increased consistent with decreasing ZnO average grain size.

scholarly journals A Conversion for Average Grain Size Based on Gamma Ray Well Log: Application in the Second Member of Xujiahe Formation of Anyue Area, Sichuan Basin

2021 ◽  
Vol 9 ◽  
Author(s):  
Liang Chen ◽  
Hancheng Ji ◽  
Nansheng Qiu ◽  
Liang Zhang
Keyword(s):  
Grain Size ◽  
Sichuan Basin ◽  
Gamma Ray ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Sediment Grain Size ◽  
Xujiahe Formation ◽  
Average Grain Size ◽  
Logarithmic Relationship ◽  
Clastic Reservoirs

The grain sizes of clastic rock sediments serve as important depositional indicators that are significant in sedimentology and petroleum geology studies. Generally, gamma ray, spontaneous-potential and resistivity well logs are utilized to qualitatively characterize variations in sediment grain size and determine the lithology in clastic reservoirs. However, grain size analysis of modern sedimentary samples collected from active rivers and deltas indicates that the percentage of fine depositional component has a logarithmic relationship with the average grain size in delta and river systems. Using the linear relationship to process the lithology interpretation, siltstones or mudstone is likely to be interpreted as sandstone. Therefore, a logarithmic conversion formula was built up between the gamma ray logs and measured grain size for the second member of the Xujiahe Formation of Anyue Area in the Sichuan Basin. Using the formula, the average grain size and lithology of the exploration wells were determined for the interest intervals. Furthermore, the calculated grain size gives a better understanding of the controlling factors of hydrocarbon-bearing reservoirs in the study area.

scholarly journals On the digitalization of the parameters of native gold particles in the study of placers and concentrate and mineralogical studies

2021 ◽  
pp. 60-72
Author(s):  
BARANNIKOV Aleksandr Grigor’evich ◽  
Keyword(s):  
Grain Size ◽  
Native Gold ◽  
Digital Data ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Important Indicator ◽  
Gold Particles ◽  
Rigorous Approach ◽  
Average Grain Size ◽  
Average Size

Relevance of the work is due to the need to increase the efficiency of studying the particles of native gold in placers using morphometric (morphogranulometric) parameters in their documentation. Graphic materials (maps, plans, sections) based on digitalization of the collected data help to increase the reliability of the forecast, make it possible to use the selected areolas in combination with other methods when assessing ore-bearing zones and areas. Purpose of the work: development of a systematics of native gold identification on a morphometric basis. Substantiation on the basis of digital data of placer samples indicators – form of gold grains, average grain size, hydraulic particle size; study of the spatial variability of the revealed parameters of the metal within the rebuilt placers. Research methodology: diagnostics (description) of the morphology of gold grains and other typomorphic features based on the quantitative parameters of particles with the subsequent calculation of the shape coefficients (flatness, elongation); generalization and interpretation of the results of the description of native gold previously obtained during the exploration of the Ural placers. Results. The proposed systematics of native gold outwards on a morphometric basis allows a more rigorous approach to the identification of metal particles (excluding the subjectivity of describing the outward look of ore). When substantiating the average size of gold grains, significant discrepancies were noted in the results obtained by two independent methods: when measuring the parameters of gold grains on a morphogranulometric basis and using traditional sieve grain size analysis. The geological factors that determine the level of discrepancy between the compared methods are considered. It is about how the revealed discrepancies should be taken into account in the practice of forecasting and prospecting works. It is argued that the most important indicator characterizing the migratory mobility of gold particles in an aquatic environment is their hydraulic size (HS, cm/s). An approach to substantiating HS based on measurements of morphogranulometric parameters of particles (axes A, B, C) is proposed. Examples are considered based on the interpretation of the accumulated digital data in the mineralogical mapping of a number of ore-bearing areas and sites. Conclusions. Long years of studying native gold from placers using the developed systematics of particles on a digital (morphogranulometric) basis have been tested by the practice of forecasting and prospecting and research works. The described approach, based on digitalization of the accumulated information, is recommended for implementation and further improvement

Grain Size and Provenance of Bahia la Choya Sediments

1987 ◽  
Vol 2 ◽  
pp. 44-51 ◽  
Author(s):  
Lawrence T. Sumpter
Keyword(s):  
Grain Size ◽  
Tidal Flat ◽  
Volcanic Rocks ◽  
Heavy Minerals ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Rock Fragments ◽  
The North ◽  
Average Grain Size ◽  
Carbonate Shell

A grain size analysis (including the carbonate fraction) was performed on sediment samples from each of the following environments of Bahia la Choya: tidal flat, spit, beach, and estero. The sediments of the tidal flat have an average grain size of 2.88 phi, range from very well sorted to moderately well sorted, and have a carbonate shell fraction ranging from 1 to 30%. The spit sediments have an average grain size of 0.96 phi, are moderately to poorly sorted, and have a carbonate shell fraction of approximately 50%. The beach sediments have an average grain size of 1.22 phi, range from poorly sorted to moderately well sorted, and have a carbonate shell fraction of approximately 48%. The sediments of the estero average 39% sand, 40% silt, and 20% clay. The carbonate fraction in the estero is approximately 25%. The noncarbonate fraction in all the environments is made up of feldspar, quartz, biotite, heavy minerals, and igneous rock fragments.The major source for the sediment is the Pelican Point granite on the south side of the bay. Pleistocene rock in and around the bay provides a second source of sediment and volcanic rocks to the north may also contribute to the sediment.

scholarly journals Geochemical and Mineralogical Characterisation of Historic Zn–Pb Mine Waste, Plombières, East Belgium

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 28
Author(s):  
Srećko Bevandić ◽  
Rosie Blannin ◽  
Jacqueline Vander Auwera ◽  
Nicolas Delmelle ◽  
David Caterina ◽  
...  
Keyword(s):  
Grain Size ◽  
Mine Waste ◽  
Geophysical Methods ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Mine Wastes ◽  
Metallurgical Waste ◽  
High Concentration ◽  
Geochemical Properties ◽  
Potential Applications

Mine wastes and tailings derived from historical processing may contain significant contents of valuable metals due to processing being less efficient in the past. The Plombières tailings pond in eastern Belgium was selected as a case study to determine mineralogical and geochemical characteristics of the different mine waste materials found at the site. Four types of material were classified: soil, metallurgical waste, brown tailings and yellow tailings. The distribution of the mine wastes was investigated with drill holes, pit-holes and geophysical methods. Samples of the materials were assessed with grain size analysis, and mineralogical and geochemical techniques. The mine wastes dominantly consist of SiO2, Al2O3 and Fe2O3. The cover material, comprising soil and metallurgical waste is highly heterogeneous in terms of mineralogy, geochemistry and grain size. The metallurgical waste has a high concentration of metals (Zn: 0.1 to 24 wt.% and Pb: 0.1 to 10.1 wt.%). In the tailings materials, Pb and Zn vary from 10 ppm to 8.5 wt.% and from 51 ppm to 4 wt.%, respectively. The mining wastes comprises mainly quartz, amorphous phases and phyllosilicates, with minor contents of Fe-oxide and Pb- and Zn-bearing minerals. Based on the mineralogical and geochemical properties, the different potential applications of the four waste material types were determined. Additionally, the theoretical economic potential of Pb and Zn in the mine wastes was estimated.

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