Fiber Dispersed Porous Alumina Sintered under Direct High Gas Pressure for High Thermal Shock Resistant Application

1991 ◽  
Vol 251 ◽  
Author(s):  
Toyokazu Kurushima ◽  
K. Ishizaki ◽  
S. Osaki

ABSTRACTFiber dispersed porous alumina ceramics were produced by a direct high gas pressure sintering method. The produced materials exhibited relative densities of 75–85%, high bending strength and good thermal shock resistance. The alumina ceramics were characterized by lower closed porosity and higher open porosity. These characters strengthen the thermal shock resistance of porous ceramics. This high gas pressure sintering by the direct high gas pressure sintering method densifies only bridge parts of alumina ceramics which support pores. This process is concluded to be effective to produce materials with higher strength, better thermal shock resistance and higher open porosity.

2020 ◽  
Vol 94 (2) ◽  
pp. 414-453
Author(s):  
Małgorzata Daszkiewicz ◽  
Piotr Łuczkiewicz ◽  
Jörg Kleemann ◽  
Aneta Kuzioła

AbstractThe necropolis at Malbork-Wielbark was excavated from 1927 to 1936 and 2008 to 2019. This burial ground is the eponymous site of the Wielbark culture. To date, over 2000 burials, both inhumation and cremation (pit and urn graves), have been recorded at this site, attesting to its continuous use from the Early Pre-Roman Iron Age (phase A1) to the early Migration Period (phase D1), with particular emphasis on the Roman Period. The cemetery site partially overlies and damages an earlier Iron Age settlement of the Pomeranian culture.Laboratory analyses were carried out on 113 pottery sherds. The series of samples chosen for analysis reflected, as far as was possible, all relative chronological phases and vessel shapes. The pottery was analysed using a step by step strategy built on the results of MGR-analysis (i. e. the classification of samples based on their matrix type) and on a macroscopic assessment of clastic material. In addition, an estimation of chemical composition by portable energy-dispersive X-ray fluorescence (pXRF) was available for each sample. After they had been classified, samples were selected for chemical analysis by wavelength-dispersive X-ray fluorescence (WD-XRF), estimation of physical ceramic properties (open porosity, water absorption and apparent density), Kilb-Hennike analysis (K-H analysis), thin-section studies using a polarising microscope, a study of surface phenomena by RTI (Reflectance Transformation Imaging), thermal analysis (TG-DTG-DTA), X-ray diffraction analysis and functional properties analysis (water permeability and thermal shock resistance), as well as experimental estimation of magnetic properties.The results of MGR-analysis carried out on ceramic samples taken from 113 potsherds revealed that all of the pottery was made from various non-calcareous clays with fine-grained iron compounds homogeneously distributed in the matrix. It was decided not to carry on determining/using MGR-groups, as nearly every sherd represents a different MGR-group. This means that these vessels were made during different production cycles. The differences in thermal behaviour between samples were attributed only to matrix-type groups. It can be concluded that 85 % of the total sherds were made from plastic raw materials of the same provenance, and that the same matrix-type groups occurred in all chronological phases. The percentage of vessels made of particular raw materials indicates a significant difference in the preferences of Pomeranian Culture potters and those of Pre-Roman Iron Age, Early Roman Period and those of the Late Roman Period, when one type of raw material disappears from use. This last period is also characterized by an increase in the number of vessels fired in a reducing atmosphere. Standardization is also evident in vessel-wall thickness, which falls within a narrow range of values, on the other hand combined with a large variety in grain sizes up to very large ones and with a wide range of open porosity values, which in turn points to a lack of care in the preparation of the ceramic body. Vessels that may have been non-local origin are noted in all chronological phases. Analysis of functional properties (water permeability and thermal shock resistance) revealed that the pottery deposited in graves included fully functional wares, such as cooking pots, as well as vessels intended solely as grave goods.More than a few samples evidence the use of a slow-rotating potter’s wheel, and it is also possible that a template was used for forming vessel rims. However, there are very few examples of truly technologically advanced vessels. The technology is generally tailored to the desired type or form of vessel.


TANSO ◽  
1985 ◽  
Vol 1985 (120) ◽  
pp. 21-27 ◽  
Author(s):  
Kenji Miyazaki ◽  
Hisayoshi Yoshida ◽  
Kazuo Kobayashi

2007 ◽  
Vol 544-545 ◽  
pp. 379-382
Author(s):  
Kyung Hun Jang ◽  
Bum Rae Cho

The effect of CaO, MgO and SiO2 as a flux on the sinterability of zirconia toughened alumina(ZTA) used for plasma reactors was investigated and the effect of zircon addition on thermal shock resistance of ZTA with 15wt.% of ZrO2 was also investigated. The resultant data revealed that ZTA shows the best sinterability at the composition of 2wt.% of CaO, 4wt.% of MgO and 2wt.% of SiO2 and at the sintering temperature of 1350°C. Thermal shock resistance of ZTA containing zircon was improved significantly. It is shown that ZTA containing 10wt.% of zircon shows better thermal shock resistance than others. This fact can be explained due to the low thermal expansion coefficient of zircon. It was concluded that zircon is an effective material to improve thermal shock resistance of alumina ceramics.


2011 ◽  
Vol 94 (8) ◽  
pp. 2304-2307 ◽  
Author(s):  
Wei-Li Wang ◽  
Jian-Qiang Bi ◽  
Kang-Ning Sun ◽  
Ming Du ◽  
Na-Na Long ◽  
...  

2012 ◽  
Vol 509 ◽  
pp. 240-244
Author(s):  
Li Ying Tang ◽  
Xi Cheng ◽  
Ping Lu ◽  
Fang Yue

Abstract: Cordierite–alumina ceramics were prepared with the raw materials of cordierite and α-alumina powder, and TiO2,CuO and MgO were added as composite additives. The effect of MgO/ CuO ratios on the microstructure, thermal conductivity and thermal shock resistance of cordierite–alumina ceramics were researched by X-ray diffraction, scanning electron microscopy and laser flash analyzer; the bulk density and the porosity of cordierite – alumina ceramics were measured. The results show that with increasing of MgO/CuO ratios, the bulk density and thermal conductivity increase firstly and then decrease, and have a minimum with 0.4wt% MgO and 0.667 MgO/CuO; and the porosity of ceramics decreases firstly and then increases and has a maximum with 0.4wt% MgO and 0.667 MgO/CuO;There are little changes in the size of the grain of the ceramics, and a small amount of magnesium aluminate spinel precipitate; the thermal shock resistance performance of the ceramics is developed with the increasing of MgO/CuO ratios.


2012 ◽  
Vol 538-541 ◽  
pp. 2277-2280
Author(s):  
You Fu Guo ◽  
Ming Yue Zheng ◽  
Jing Long Bu ◽  
Yue Jun Chen ◽  
Li Xue Yu ◽  
...  

Silicon carbide with diffierent granularity was used as raw material, quartz, silica fume, aluminum powder or alumina was used as additive with dosages of 1% (in mass, similarly hereinafter), 3% and 5%. Silicon carbide refractory material was prepared in oxidizing atmosphere at 1400 °C for 3 h. Performence of samples were researched by measurements of apparent porosity, bulk density, bending strength at room temperature, thermal shock resistance and thermal expansion rate, and analyzed by SEM. The results showed that samples added silica fume have low thermal expansion rate and apparent porosity, high bending strength and bulk density, good thermal shock resistance, compact texture as well. It can be deduced that 5% silica fume plays the excellent role to improve integrated performance of silicon carbide refractory material.


2014 ◽  
Vol 692 ◽  
pp. 217-223 ◽  
Author(s):  
Xiao Hong Xu ◽  
Xiao Yang Xu ◽  
Jian Feng Wu ◽  
Yang Zhou ◽  
De Zhi He

Al2O3 composite ceramics materials used for heat transmission pipeline were prepared by pressureless sintering in air. Calcined bauxite, talc and commercial alumina powder were used as the main raw materials, partially stabilized zirconia was also added to improve the thermal shock resistance of the samples. The effects of composition and sintering temperature on density, phase composition, microstructure and thermal shock behavior of samples were evaluated. It shows that the B2 sample which was sintered at 1400 °C for 2 h has optimal properties with porosity 0.4%, bulk density 3.2 g•cm-3.The bending strength increases 19.46 MPa after 30 times thermal shock cycles from 1100 °C to room temperature. The main phases of B2 are corundum and spinel, meanwhile, a small amount of monoclinic zirconia and α-quartz are also detected according to XRD pattern. Microstructure analysis reveals that spinel crystals are interlocked by prismatic corundum crystals, bright white beaded monoclinic zirconia particles are distributed uniformly, and it is beneficial to improve the thermal shock resistance of sample.


2011 ◽  
Vol 194-196 ◽  
pp. 1724-1727 ◽  
Author(s):  
Heng Yong Wei ◽  
Li Xue Yu ◽  
Zhi Fa Wang ◽  
Jing Long Bu ◽  
Shu Long Ma ◽  
...  

ZrO2-Al2TiO5 composite materials with high bending strength and good thermal shock resistance expansion were prepared using partially stabilized zirconia (Y-PSZ) powders coated with Al2TiO5 by co-precipitation method. The effects of Al2TiO5 content on the sintering properties, phase composition, microstructure and thermal shock resistance of the zirconia ceramic were investigated.The results show that the apparent porosity of the samples decreased and their bending strength increased with the content of aluminum titanate increasing from 0 to 8 wt%. The samples with 5 and 8 wt% aluminum titanate addtion have excellent thermal shock resistance. The results showed that the addtion of aluminum titanate could enhance the mechanical strength and improve the thermal shock resistance of zirconia ceramic. The XRD and SEM analysis results indicated that the propriety improvement is relative with the change of the microstructure and the increase of tetragonal ZrO2 phase in the composites.


Sign in / Sign up

Export Citation Format

Share Document