Statistical analysis of compressive strength data of ceramic Raschig rings fabricated by an extrusion process using a Weibull distribution

M. Salehi,A. Salem 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.2

The influence of sintering conditions on the reliability of a special ceramic packing namely a Raschig ring, was investigated. The special kaolin used in the industrial ceramic Raschig rings manufacturing process was shaped by an extrusion method and sintered at 1200 and 1250oC using different soaking times, ranging from 30 to 180 minutes. The physico-chemical properties of specimens such as shrinkage, water absorption, bulk density, porosity, microstructure and mineralogical composition, were studied. According to the obtained results, the best sintering conditions were determined. The diametrical compressive strength of fired samples was measured on suitable specimens. The differences found in the strength data were evaluated using Weibull theory. The statistical results show that the maximum Weibull modulus is obtained when ceramic Raschig rings are fired at a lower sintering temperature and longer soaking time to reach the minimum total porosity. However, the soaking time needs to be optimized to realize the maximum strength and reliability during the fabricating process at a given temperature. The influence of sintering conditions on the reliability of a special ceramic packing namely a Raschig ring, was investigated. The special kaolin used in the industrial ceramic Raschig rings manufacturing process was shaped by an extrusion method and sintered at 1200 and 1250oC using different soaking times, ranging from 30 to 180 minutes. The physico-chemical properties of specimens such as shrinkage, water absorption, bulk density, porosity, microstructure and mineralogical composition, were studied. According to the obtained results, the best sintering conditions were determined. The diametrical compressive strength of fired samples was measured on suitable specimens. The differences found in the strength data were evaluated using Weibull theory. The statistical results show that the maximum Weibull modulus is obtained when ceramic Raschig rings are fired at a lower sintering temperature and longer soaking time to reach the minimum total porosity. However, the soaking time needs to be optimized to realize the maximum strength and reliability during the fabricating process at a given temperature.

Physical, morphological and mineralogical properties of ceramic brick incorporated with Malaysia’s Rice Hush Ash (RHA) agricultural waste

Aneis Maasyirah Hamzah,Siti Koriah Zakaria,Siti Zuliana Salleh,Abdul Hafidz Yusoff,Arlina Ali,Mardawani Mohamad,Mohamad Najmi Masri,Sharizal Ahmad Sobri,Mustaffa Ali Azhar Taib,Faisal Budiman,Pao Ter 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.2

In this work, the effect of various weight percentage of rice husk ash (RHA) in ceramic brick production was investigated interms of mineralogical, physical, chemical and morphological properties. The evaluation of the use of RHA as a raw materialfor ceramic products is tested to determine the linear shrinkage, volumetric shrinkage, water absorption, apparent density andbulk density. These physical results suggested that the addition of RHA can improve the physical properties of ceramic brick. Scanning electron microscopy images confirmed the increased of ceramic strength with the addition of RHA and firingtemperature. In addition, quantitative and qualitative chemical analysis supported the results obtained. Overall, the resultsdemonstrated the high potential of RHA in green technology for ceramic production.

Thermal Shock Behaviors of AlN/BN Laminated Ceramic Composites

Tao Zhang,Ji-feng Zhao,Zhi-hao Jin,Hai-yun Jin 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.2

AlN/BN laminated ceramic composites were fabricated by a flow casting method. The thermal shock behavior of both block AlN ceramics and AlN/BN laminated ceramic composites were carried out for comparison. To understanding the different of thermal shock resistance for the two materials, the microstructures were observed and the mechanical properties were tested. The results showed that, the thermal shock resistance of AlN/BN laminated ceramic composites was larger than that of block AlN ceramics. During the tests of residual strength after quenching from different temperatures, for the block AlN ceramics, the residual strength would decrease rapidly when the critical temperature difference ΔTc was larger than 450℃, on the other hand, for the AlN/BN laminated ceramic composites, the residual strength would decrease slowly and there was no obvious ΔTc. AlN/BN laminated ceramic composites were fabricated by a flow casting method. The thermal shock behavior of both block AlN ceramics and AlN/BN laminated ceramic composites were carried out for comparison. To understanding the different of thermal shock resistance for the two materials, the microstructures were observed and the mechanical properties were tested. The results showed that, the thermal shock resistance of AlN/BN laminated ceramic composites was larger than that of block AlN ceramics. During the tests of residual strength after quenching from different temperatures, for the block AlN ceramics, the residual strength would decrease rapidly when the critical temperature difference ΔTc was larger than 450℃, on the other hand, for the AlN/BN laminated ceramic composites, the residual strength would decrease slowly and there was no obvious ΔTc.

Development of composite seals derived from ceramic precursors for SOFC systems

Sung Jin Hong 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.2

Novel ceramic-metal composite seals derived from ceramic precursor polymers were developed in this study. The formation, microstructure and properties of composite seals were evaluated. Polymethylsiloxane was chosen as a ceramic precursor. In addition, metal and ceramic filler were mixed and pyrolyzed at 750 o C to fabricate composites. The specimen mixed with ZrO2 and Ni as filler showed a thermal expansion coefficient of 10.5 × 10-6/ o C and sealing efficient of > 98%. The microstructure of seals was observed by using Scanning Electron Microscopy (SEM). And the mechanical properties of composite seals were measured and discussed.

Preparation and characterization of zirconia ceramics with oxides addition

A. Rittidech,S. Wantrong,S. Chommi 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.2

This research investigated the relationship between the quantitative phase crystal structure and mechanical properties of ZrO2ceramic addition of Y2O3, MgO and BaCO3 at 0.0, 2.0, 4.0 and 6.0 mol%. Ceramic samples were prepared using mixed oxidemethod under normal sintering at 1,600 oC with dwell time for 120 min . ZrO2-Y2O3 and ZrO2-MgO ceramics were obtainedwith bulk densities values between 5.324-5.722 g/cm3 while ZrO2-BaCO3 ceramic showed densification values about 4.412-4.827 g/cm3. It was found that ZrO2-Y2O3 and ZrO2-MgO ceramic showed higher fracture toughness values than ZrO2-BaCO3ceramics. Refinement of lattice parameter using Rietveld analysis in ceramic samples revealed the percentage of fraction phaseratios of m-ZrO2, t-ZrO2 and c-ZrO2. The refinement parameters result in sample ceramic which are Y2O3 addition between4-6 mol% obtained a high ratio of t-ZrO2 phase and the result supported optimal mechanical properties. ZrO2-Y2O3 ceramicshowed a higher lattice stain value compared with the additions of other ZrO2 oxides and it was found that lattice strainincrease with high ratio of t-ZrO2 phase. Sample ceramics had crystallite size values between 56.65-82.30 nm. SEMmicrographs revealed morphology and average grain sizes. All samples grains were spherical in shape combined with irregularshape and were gray in color and were obtained with an average grain size between 0.63 -2.18 μm. It was found that the ZrO2-Y2O3 ceramic showed small crystallize size and size of grains. The optimal condition for addition of oxide were found inceramics of ZrO2-Y2O3 and ZrO2-MgO and confirmed that good mechanical properties were obtained from a high ratio of t-ZrO2 phase and fine grain size.

Surface modified ceramic fiber separators for thermal batteries

Hae-Won Cheong 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.S1

A wide range of possible hazards existing in thermal batteries are mainly caused by thermal runaway, which results in overheating or explosion in extreme case. Battery separators ensure the separation between two electrodes and the retention of ion-conductive electrolytes. Thermal runaways in thermal batteries can be significantly reduced by the adoption of these separators. The high operating temperature and the violent reactivity in thermal batteries, however, have limited the introduction of conventional separators. As a substitute for separators, MgO powders have been mostly used as a binder to hold molten salt electrolyte. During recent decades the fabrication technology of ceramic fiber, which has excellent mechanical strength and chemical stability, has undergone significant improvement. In this study we adopted wet-laid nonwoven paper making method instead of the electrospinning method which is costly and troublesome to produce in volume. Polymeric precursor can readily be coated on the surface of wet-laid ceramic paper, and be formed into ceramic film after heat treatment. The mechanical strength and the thermo-chemical stability as well as the wetting behaviors of ceramic separators with various molten salts were investigated to be applicable to thermal batteries. Due to their excellent chemical, mechanical, and electrical properties, wet-laid nonwoven separators made from ceramic fibers have revealed positive possibility as new separators for thermal batteries which operate at high temperature with no conspicuous sign of a short circuit and corrosion.

Mechanical and thermal behaviors of silica-based porous ceramics by addition of silicon carbide

여정구,김영환,박정수,최성철 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.8

The mechanical and thermal behaviors of porous silica-based ceramic cores for preformation of internal cooling passages ingas turbine blades were studied. The silica-based ceramic cores are composed of fused silica and zircon powders, and siliconcarbide powder (SiC) was added to improve the mechanical and thermal properties of the silica-based ceramic cores. Cristobalite, which was formed by crystallization of amorphous silica on SiC surface, improved the flexural strength, bulkdensity and thermal conductivity of silica-based ceramic cores up to an addition of 10 wt% SiC. The SiC on the silica-basedceramic cores enhanced the thermal conductivity, because SiC has higher thermal conductivity compared with matrixmaterials of ceramic cores (fused silica and zircon). However, in case of 20 wt% SiC on ceramic core, the crystallization offused silica was accelerated due to SiC addition which acts as a seed of crystallization, therefore, many microcracks weregenerated by phase transformation (β→α) of cristobalite. As a result, the flexural strength, relative density and thermalconductivity of the ceramic core with 20 wt% SiC were reduced.

A preparation and performance study of glass-ceramic glazes derived from blast furnace slag and fly ash

Hong-xia Lu,Man He,Yuan-yuan Liu,Jing-fei Guo,Li-wei Zhang,Deliang Chen,Hai-long Wang,Hong-liang Xu,Rui Zhang 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.5

Glass-ceramic glazes have been prepared successfully via crystallization from blast-furnace slag (BFS), fly ash (FA) fluxed with potash feldspar and borax. The crystalline behavior of glass-ceramic glazes was investigated using differential thermal analysis and thermogravimetric analysis (DTA/TG), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results revealed that the major crystalline phases are anorthite (CaAl2Si2O8) and akermanite (Ca2MgSi2O7) and crystalline phases disperse well in glassy phases with a uniform size of 1 μm. Glass-ceramic glazes possess low density, low water absorption,perfect stain resistance, acid resistance and alkali resistance. The thermal expansion coefficient of glass-ceramic glazes is steady up to 800 oC with an average value of 7.2 × 10−6 /K. Final results suggest that BFS and FA have potential to be vitrified into economically and environmentally low-cost glass-ceramic glaze materials.

An investigation of the mechanical property and thermal shock behavior of machinable B₄C/BN ceramic composites

Tao Jiang,Haiyun Jin,Zhihao Jin,Jianfeng Yang,Guanjun Qiao 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.1

Machinable B₄C/BN ceramic composites were fabricated by a hot-pressing process at 1,850 ℃ for 1 h under a pressure of 30MPa. In this article, the mechanical property, thermal shock behavior and machinability of the B₄C/BN ceramic composites were investigated. The fracture strength and fracture toughness of B₄C/BN nanocomposites were significantly improved in comparison with B₄C/BN microcomposites. The Vickers hardness of B₄C/BN nanocomposites and B₄C/BN microcomposites decreased gradually with an increase in the content of h-BN, while the machinability of B₄C/BN nanocomposites and B₄C/BN microcomposites were significantly improved. The B₄C/BN ceramic composites with an h-BN content of more than 20 wt% exhibited excellent machinability. The thermal shock resistance of the B₄C/BN ceramic composites was much better than that of the B₄C monolith, and the thermal shock resistance of B₄C/BN nanocomposites was much better than that of B₄C/BN microcomposites. The thermal shock temperature difference (ΔTc) of the B₄C monolith was about 300℃, while the ΔTc of B₄C/BN microcomposites was about 500℃ and the ΔTc of B₄C/BN nanocomposites was about 600℃. Machinable B₄C/BN ceramic composites were fabricated by a hot-pressing process at 1,850 ℃ for 1 h under a pressure of 30MPa. In this article, the mechanical property, thermal shock behavior and machinability of the B₄C/BN ceramic composites were investigated. The fracture strength and fracture toughness of B₄C/BN nanocomposites were significantly improved in comparison with B₄C/BN microcomposites. The Vickers hardness of B₄C/BN nanocomposites and B₄C/BN microcomposites decreased gradually with an increase in the content of h-BN, while the machinability of B₄C/BN nanocomposites and B₄C/BN microcomposites were significantly improved. The B₄C/BN ceramic composites with an h-BN content of more than 20 wt% exhibited excellent machinability. The thermal shock resistance of the B₄C/BN ceramic composites was much better than that of the B₄C monolith, and the thermal shock resistance of B₄C/BN nanocomposites was much better than that of B₄C/BN microcomposites. The thermal shock temperature difference (ΔTc) of the B₄C monolith was about 300℃, while the ΔTc of B₄C/BN microcomposites was about 500℃ and the ΔTc of B₄C/BN nanocomposites was about 600℃.

High strength ultra-lightweight ceramic proppants prepared by double resin-coating process with fly ash

Shuiyun Li,Yongshang Tian,Xiaoliang Dong,Peng Liu,Xiang Ji,Xiongjie Hu 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.5

Ceramic proppants is crucial in hydraulic fracturing for increasing oil and gas reservoirs. In this study, the ceramic particlesand resin-impregnated ceramic particles were prepared with fly ash, and then ultra-lightweight ceramic particles (proppants)were obtained by double resin-coating process. Crystalline phase and microstructure of the ceramic particles were investigatedby X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Effects of silicon carbide and epoxy resinconcentrations on the phase, apparent density, and breakage ratio of the ceramic particles were all studied systematically. Withincreasing silicon carbide contents, the corundum phase transform to mullite phase, decreasing the apparent density andincreasing the breakage ratios. The double resin-coated ceramic proppants featured smoother surface and less pores than theresin-impregnated samples, accompanying low apparent density (1.94 g/cm-3) and high strength (breakage ratio under 52 MPa,1.69%) when silicon carbide was 3.0 wt.% and epoxy resin concentrations was 55 wt.%. The results suggest the particles bythe effective double resin-coating process possess promising candidates for fracturing proppants in practical applications.