scholarly journals Blīva augsttemperatūras mullīta-ZrO2 keramika

2018 ◽  
Vol 35 ◽  
pp. 112-133
Author(s):  
Gaida Sedmale ◽  
Uldis Sedmalis ◽  
Ingunda Šperberga ◽  
Māris Rundāns
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Sintering Process ◽  
Ceramic Samples ◽  
Shock Resistance ◽  
Composition Structure ◽  
Plasma Dispersion ◽  
Sintering Processes

Parādīta piedevu (mālu minerāla – illīta, Si3N4, SiAlON), kā arī izejas pulveru izstrādes veida ietekme uz mullīta-ZrO2 keramikas saķepināšanas procesu (pielietojot tradicionālo saķepināšanas procesu un plazmas izlādes saķepināšanas procesu jeb SPS), fāžu sastāvu, struktūru, mehāniskajām un keramiskajām īpašībām.Mālu piedeva sekmē pulvera  daļiņu  izmēru  samazināšanos,  veicina  keramikas paraugu sablīvēšanos tradicionālā saķepināšanas procesā, bet dod pretēju efektu, pielietojot SPS procesu. Silīcija  nitrīda un  SiAlON nanopulveru  piedevas ir efektīvas SPS procesā, sasniegta paraugu spiedes izturība ap 600 MPa Si3N4 piedevas gadījumā, termiskā trieciena izturību un elastības moduļa  vērtības 180 – 220 GPa, kuras termiskā trieciena 1000/20 °C rezultātā samazinās pieļaujamās robežās. Šīs vērtības ir par aptuveni 20–25 % zemākas, pielietojot SiAlON piedevu.Keramikas paraugu, kas saķepināti tradicionāli un pielietojot SPS procesu, mikrostruktūrā ir mullīta vai pseidomullīta kristāliski veidojumi ar ieslēgtiem ZrO2 graudiem, kas pārsvarā ir kubiskā modifikācijā. Galvenā atšķirība starp abos saķepināšanas procesos iegūtajiem paraugiem ir tā, ka tradicionāli saķepināto paraugu mikrostruktūrā ir novērojama ‘tukšumu’ veidošanās, kuri aizpildās ar mullīta kristāliem, it sevišķi palielinoties Si3N4 piedevai. Mikrostruktūra keramikas paraugiem, kas saķepināti ar SPS tehnoloģiju ir blīvāka – mullīta kristāli ir blīvi izvietojušies, un tiem nav mullītam raksturīgās prizmatiskās formas.Dense high-temperature mullite-ZrO2 ceramicsThe influence of some additives (clay mineral illite, Si3N4, SiAlON) and the processing of the initial powders on sintering of mullite-ZrO2 ceramics (using traditional or plasma dispersion sintering processes), composition, structure, mechanical and ceramic properties of phases is shown.The clay additive contributes to the reduction of the particle size of the powder, facilitates the densification of the ceramic samples in the traditional sintering process, but vice versa if SPS is used. Silicon nitride and SiAlON nanopowder additives are effective in the SPS process; samples reach a compressive strength of approximately 600 MPa in the case of Si3N4 additive; thermal shock resistance and elastic modulus are in the range of 180–220 GPa, which under a thermal shock of 1000/20 °C will reduce within the permissible limits. These values are about 20–25 % lower if SiAlON additive is used.The microstructure of the ceramic samples traditionally sintered or sintered using a SPS process is formed by crystalline mullite or pseudomulite crystals with enclosed ZrO2 grains that mostly are in the cubic modification. The main difference between the samples obtained in both sintering processes is that formation of voids filled with mullite crystals can be observed in the microstructure of traditionally sintered samples, especially if the amount of Si3N4 additive is increased. The microstructure of the ceramic samples sintered with SPS technology is denser – the mullite crystals are densely distributed and do not have the prismatic shape that is characteristic to mullite.

Study of Thermal Shock Resistance of Sagger Plate Used in Floppy Magnets Sintering

2007 ◽  
Vol 280-283 ◽  
pp. 1667-1670 ◽  
Author(s):  
Feng Cao ◽  
Xing Rong Wu ◽  
Rainer Telle
Keyword(s):  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Rapid Development ◽  
Particle Surface ◽  
Sem Analysis ◽  
Sintering Process ◽  
Kiln Furniture ◽  
Dense Structure ◽  
Zircon Powder ◽  
Shock Resistance

The rapid development of magnetic materials has witnessed a sustained consumption increase in corundum-mullite kiln furniture application, yet a comparatively short duration of them. In this view, the thermal shock resistance of sagger plate in floppy magnets sintering turns out a factor of critical importance. This paper makes a study concerning the influence of factors including the size of critical electro-melted mullite particles, the electro-melted corundum or mullite as medium particles and the addition of upon the thermal shock resistance. The result shows that, with critical particles of 2 mm, the sheet of about 10mm thickness is characterized by better performance in modulus of rapture and thermal shock resistance. The latter proves to be more outstanding in samples rather than mullite. When zircon powder is added in a two-hour sintering process at the temperature of 1550°C, a remarkable improvement is made by the sample in terms of its thermal shock resistance. SEM analysis shows the existence of micropores in the section of samples with corundum as medium particles, whereas the glasses phase in that of mullite sample, resulting in a dense structure. Finally, zircon powder added makes for the improvement of thermal shock resistance due to the formation of baddeleyite on the particle surface of the corundum.

Viability of Some Kano-Nigerian Clays for Refractory Applications

2013 ◽  
Vol 315 ◽  
pp. 477-481 ◽  
Author(s):  
I.A. Rafukka ◽  
B. Onyekpe ◽  
Y. Tijjani
Keyword(s):  
Compressive Strength ◽  
Physical Properties ◽  
Bulk Density ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Linear Shrinkage ◽  
Chemical Compositions ◽  
Shock Resistance ◽  
Materials Used ◽  
Refractory Bricks

The physical properties of some materials used by local foundries were investigated with a view to assessing their suitability for use as low heat duty refractory bricks. The samples were collected from Malamai village, Gezawa Local Government, Kano state; they are Gezawa clay and Burji (Clay). The samples were crushed, ground, sieved and the chemical compositions were determined. The clay samples were treated separately as well as blended with Gezawa clay in different proportions and molded in to bricks. The bricks were dried and fired to 1100. Test for refractoriness, thermal shock resistance, linear shrinkage; bulk density, porosity and compressive strength were carried out on each of the specimen. Burji blended with 50% to 90% Gezawa clay gave improved thermal shock resistance with a refractoriness of 1300 and hence could be used for non ferrous melting cupolas.

Sic Based Ceramic Foams Reinforced by In Situ Mullite Whisker

2009 ◽  
Vol 79-82 ◽  
pp. 1983-1986 ◽  
Author(s):  
Xiao Li Ji ◽  
Fei Xu ◽  
Hai Ya Chen
Keyword(s):  
Compressive Strength ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Ceramic Foams ◽  
Sic Ceramic ◽  
Influence Of Temperature On ◽  
Shock Resistance ◽  
Mullite Whiskers ◽  
Maximum Compressive Strength

Prepared silicon carbide(SiC) ceramic foams combined with mullite whiskers which synthesized by in-situ reaction. Studied on the influence of temperature on the synthesis of mullite whisker, and the influence of mullite content on the compressive strength, thermal shock resistance of SiC ceramic foams. The results indicate that the performance of mullite whiskers synthesized at 1400°Cwere best, when mullite content was 25%, SiC ceramic foams could reach the maximum compressive strength for 1.75MP, the most thermal shock resistance for14 times.

Preparation and Performance of β-Sialon Bonded ZrO2 Composites

2011 ◽  
Vol 415-417 ◽  
pp. 138-141
Author(s):  
Rui Sheng Wang ◽  
Jun Hong Zhao ◽  
Ying Na Wei ◽  
Fu Hua Peng ◽  
Heng Yong Wei
Keyword(s):  
Thermal Expansion ◽  
Flexural Strength ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Reaction Sintering ◽  
Sintering Process ◽  
Carbon Addition ◽  
Shock Resistance ◽  
And Performance ◽  
Sialon Powder

β-Sialon bonded ZrO2 composites were prepared by reaction sintering process using β-Sialon and CaO stabilized ZrO2 powders as raw materials.The effect of β-Sialon powder additions on the properties of the composites was investigated. The results show that the samples with 10 wt% of β-Sialon addition had the lowest apparent porosity (29.80%) and the highest of flexural strength (68.70MPa). The thermal shock resistance in carbon addition of the composites could be improved by addtion of 5wt% β-Sialon. It may be relative with that the sample had the lowest thermal expansion coefficient in vacuum.

The Influence of Particles Size and Composition Variation of NiCr-CrC(20NiCr) Metal Matrix Composites Coatings Properties on Boiler Tubes Application

2017 ◽  
Vol 889 ◽  
pp. 30-35 ◽  
Author(s):  
Erie Martides ◽  
Budi Prawara ◽  
Husaini Ardy ◽  
Endro Junianto ◽  
Budi Priyono
Keyword(s):  
Particle Size ◽  
Thermal Shock ◽  
Metal Matrix ◽  
Thermal Shock Resistance ◽  
Resistance Testing ◽  
Matrix Composites ◽  
Spray Method ◽  
Hvof Thermal Spray ◽  
Boiler Tubes ◽  
Shock Resistance

Deposition of NiCr-CrC(20NiCr) metal matrix composite (MMCs) coating have been applied on the substrate of boiler tubes material with High Velocity Oxygen Fuel (HVOF) thermal spray method and constant parameter. Variation of particle size and composition on MMCs was conducted to determined the optimum conditions for boiler applications. Microvickers hardness, metallography and thermal shock resistance testing were investigated. The best performance for boiler tubes application is MMC NiCr-CrC(20NiCr) with 270 mesh of NiCr particles size and 60:40 of composition as evidence by the highest of hardness value (410 Hv) and slightly of discoloration after thermal shock resistance with two variation cooling medium. While at MMC NiCr-CrC(20NiCr) with 70:30 variation composition, coating hardness value will decrease in line with the smaller of particle size of NiCr.

scholarly journals Optimization of Properties for Alumina-Spinel Refractory Castables by CMA (CaO-MgO-Al2O3) Aggregates

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3050
Author(s):  
Hai Tang ◽  
Chunxue Li ◽  
Jianying Gao ◽  
Bruno Touzo ◽  
Chunfeng Liu ◽  
...  
Keyword(s):  
Particle Size ◽  
Bulk Density ◽  
Thermal Shock ◽  
Fatigue Resistance ◽  
Thermal Fatigue ◽  
Thermal Shock Resistance ◽  
Thermal Fatigue Resistance ◽  
Spinel Refractory ◽  
Refractory Castables ◽  
Shock Resistance

Aiming at optimizing properties of alumina-spinel refractory castables, coarse corundum particles were replaced partially with the particles of a novel porous multi-component CMA (CaO-MgO-Al2O3) aggregate in the same size. Properties including the bulk density, apparent porosity, strength, slag corrosion resistance, thermal shock resistance and thermal fatigue resistance of alumina-spinel refractory castables containing CMA aggregates were evaluated contrastively. The results demonstrated that the incorporation of CMA aggregates can significantly improve thermal shock resistance and thermal fatigue resistance of castables, although companying with slight decrease in the bulk density and strength. Moreover, slag penetration resistance of castables can also be enhanced by CMA aggregates with appropriate particle size. The influence of CMA aggregates on properties of alumina-spinel refractory castables depended strongly on their particle size.

scholarly journals Effect of Hollow Corundum Microspheres Additive on Physical and Mechanical Properties and Thermal Shock Resistance Behavior of Bauxite Based Refractory Castable

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4736
Author(s):  
Rimvydas Stonys ◽  
Jurgita Malaiškienė ◽  
Jelena Škamat ◽  
Valentin Antonovič
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Thermal Shock ◽  
Modulus Of Elasticity ◽  
Thermal Shock Resistance ◽  
Visual Analysis ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Shock Resistance

This paper analyses the effect of hollow corundum microspheres (HCM) on both physical-mechanical properties (density, ultrasonic pulse velocity, modulus of elasticity, and compressive strength) and thermal shock resistance behavior of refractory medium cement castable with bauxite aggregate. Moreover, the scanning electron microscopy (SEM) results of HCM and refractory castable samples are presented in the paper. It was found that the replacement of bauxite of 0–0.1 mm fraction by HCM (2.5%, 5%, and 10% by weight of dry mix) had no significant effect on the density and compressive strength of castable, while the modulus of elasticity decreased by 15%. Ultrasonic pulse velocity (Vup) values and the visual analysis of the samples after thermal cycling showed that a small amount of HCM in composition of refractory castable could reduce the formation and propagation of cracks and thus increase its thermal shock resistance.

scholarly journals Crucial effect of SiC particles on in situ synthesized mullite whisker reinforced Al2O3-SiC composite during microwave sintering

2017 ◽  
Vol 11 (2) ◽  
pp. 106-112 ◽  
Author(s):  
Xudan Dang ◽  
Meng Wei ◽  
Rui Zhang ◽  
Keke Guan ◽  
Bingbing Fan ◽  
...  
Keyword(s):  
Particle Size ◽  
Flexural Strength ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Hot Spot ◽  
Microwave Sintering ◽  
Sic Particles ◽  
Shock Resistance ◽  
Sic Particle

Mullite whisker reinforced Al2O3-SiC composites were in situ synthesized by microwave sintering at 1500?C for 30min. The influence of SiC particle size on heating process and properties of Al2O3-SiC composite were investigated. The XRD and SEM techniques were carried out to characterize the samples. The thermal shock resistance and flexural strength of the samples were examined through water quenching and three-point bending methods, respectively. It was found that the bridging of mullite whisker appeared between Al2O3 and SiC particles which enhanced the thermal shock resistance. A so-called local hot spot effect was proposed dependent on the coupling of SiC particles with microwave, which was the unique feature of microwave sintering. The maximal thermal shock resistance and flexural strength were obtained for the samples with SiC particle size of ~5?m.

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