Ceramics Technology Group

Shah Alam, Malaysia

Ceramics Technology Group

Shah Alam, Malaysia
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Ramesh S.,University of Tenaga Nasional | Tolouei R.,University of Tenaga Nasional | Tan C.Y.,University of Tenaga Nasional | Aw K.L.,University of Tenaga Nasional | And 3 more authors.
Advanced Materials Research | Year: 2011

In the present work, densification of synthesised hydroxyapatite (HA) bioceramic prepared via chemical precipitation method was investigated. HA samples was prepared by compaction at 200 MPa and sintered at temperatures ranging from 800°C to 1400°C. The results revealed that the HA phase was stable for up to sintering temperature of 1250°C. However, decomposition of HA was observed in samples sintered at 1300°C with the formation of tetra-calcium phosphate (TTCP) and CaO. Samples sintered above 1400°C were found to melt into glassy phases. The bulk density increases with increasing temperature and attained a maximum value of 3.14 gcm-3 at 1150°C whereas maximum hardness value of 6.64 GPa was measured in HA sintered at 1050°C. These results are discussed in terms of the role of grain size. © (2011) Trans Tech Publications, Switzerland.


Ramesh S.,University of Tenaga Nasional | Ramesh S.,University of Malaya | Tan C.Y.,University of Tenaga Nasional | Yeo W.H.,University of Tenaga Nasional | And 4 more authors.
Ceramics International | Year: 2011

The sinterability of Bi2O3-doped hydroxyapatite (HA) has been studied and compared with the undoped HA. Varying amounts of Bi 2O3 ranging from 0.05 wt% to 1.0 wt% were mixed with the HA. The study revealed that most sintered samples composed of the HA phase except for compacts containing 0.3, 0.5 and 1.0 wt% Bi2O3 and when sintered above 1100 °C, 1000 °C and 950 °C, respectively. In general, the addition of 0.5 wt% Bi2O3 was identified as the optimum amount to promote densification as well as to improve the mechanical properties of sintered HA at low temperature of 1000 °C. Throughout the sintering regime, the highest value of relative bulk density of 98.7% was obtained for 0.5 wt% Bi2O3-doped HA when sintered at 1000 °C. A maximum Young's modulus of 119.2 GPa was measured for 0.1 wt% Bi2O3-doped HA when sintered at 1150 °C. Additionally, the ceramic was able to achieve highest hardness of 6.08 GPa and fracture toughness of 1.21 MPa m1/2 at sintering temperature of 1000 °C. © 2010 Elsevier Ltd and Techna Group S.r.l.


Ramesh S.,University of Malaya | Tan C.Y.,University of Tenaga Nasional | Tolouei R.,University of Tenaga Nasional | Amiriyan M.,University of Tenaga Nasional | And 3 more authors.
Materials and Design | Year: 2012

The sintering behavior of three different types of hydroxyapatite (HA) i.e. a commercial powder, HA(C), a synthesized powder by wet chemical precipitation method, HA(W) and a synthesized powder by mechanochemical method, HA(M) were investigated over the temperature range of 1000-1350°C. It has been revealed that the sinterability and mechanical properties of the synthesized HA(W) was significantly higher than that of the HA(C) and HA(M). The optimum sintering temperature for the HA(W) samples was 1100°C with the following properties being recorded: 99.8% relative density, Vickers hardness of 7.04GPa and fracture toughness of 1.22MPam1/2. In contrast, the optimum sintering temperature for the HA(C) and HA(M) samples was 1300°C with relative density of 98% and 95.5%, Vickers hardness of 5.47 GPa and 4.73GPa, fracture toughness of 0.75MPam1/2 and 0.82MPam1/2 being measured. The present research showed that the wet chemical precipitation reaction was beneficial in producing a highly crystalline, high purity and single phase stoichiometric HA powder that is sinteractive particularly at low temperatures below 1100°C. © 2011 Elsevier Ltd.


Ramesh S.,University of Malaya | Aw K.L.,Ceramics Technology Laboratory | Tolouei R.,Ceramics Technology Laboratory | Amiriyan M.,Laval University | And 5 more authors.
Ceramics International | Year: 2013

In the present work, the sintering behaviour of HA particles prepared via the wet precipitation method (HAp) and wet mechanochemical technique (HAwm) was investigated. The sintering behaviour of a commercial HA powder (HAc) was also studied for comparison purpose. All the three powders were characterised in terms of particle size, Ca/P ratio and crystal size. Green samples were prepared and sintered in air at temperatures ranging from 1000 °C to 1400 °C. The sintered bodies were studied in terms of the phase stability, relative density, Young's modulus, Vickers hardness, fracture toughness and grain size. The results indicated that HAwm samples suffered phase decomposition while the HAp and HAc sintered samples showed no phase disruption throughout the temperature range employed. The HAp samples exhibited the overall best densification and properties when compared to the HAc and HAwm samples. Furthermore, the results showed that mechanical properties of sintered samples were governed by both the bulk density and the grain size. © 2012 Elsevier Ltd and Techna Group S.r.l.


Chew W.J.K.,University of Malaya | Ramesh S.,University of Malaya | Tan C.Y.,University of Malaya | Amiriyan M.,Laval University | And 2 more authors.
Applied Mechanics and Materials | Year: 2013

The effect of ZrB2 content ranging from 10 to 30 wt% on the mechanical properties and electrical resistivity of sintered Y-TZP/ZrB2 composite was investigated. While ZrB2 content showed marginal improvement in elastic modulus, the presence of up to 20 wt% ZrB2 was beneficial in densification and hardness of the composite when sintered at lower sintering temperatures. Significantly higher fracture toughness of all composites compared to monolithic Y-TZP implied that other toughening mechanisms are at work. In spite of the poor mechanical properties, Y-TZP/30 wt% ZrB2 showed the lowest electrical resistivity at room temperature. © (2013) Trans Tech Publications, Switzerland.


Sankar U.,University of Tenaga Nasional | Satgunam M.,University of Tenaga Nasional | Amiriyan M.,University of Tenaga Nasional | Singh R.,University of Tenaga Nasional | Teng W.D.,Ceramics Technology Group
Applied Mechanics and Materials | Year: 2011

The effect on densification and mechanical properties of 3 mol% Y-TZP ceramics doped with zinc oxide (0.1 wt.% to 1 wt.%), has been investigated in this study. Green samples were compacted by uniaxial pressing and cold isostatically pressed at 200 MPa. All samples have been sintered over the temperature range of 1250°C to 1500°C with a ramp rate of 10°C/ minute and 2 hours of holding time. In addition to that, the tetragonal phase stability of the samples was also studied in superheated steam at 180°C/10 bar for up to 50 h. The sintered bodies were examined to determine the phase content, bulk density, Young's modulus, Vickers hardness and fracture toughness. The results showed that the addition of 1 wt.% ZnO was effective in aiding densification (∼99% theoretical density). It also improved the matrix stiffness (∼208 GPa) and Vickers hardness (∼13 GPa), when the samples were sintered below 1300°C comparing to the undoped Y-TZP sintered at the same temperature. In contrast, ZnO addition to the Y-TZP matrix displayed a tendency to change hydrothermal ageing behavior as it was noticed that the monoclinic content increased with increasing content of dopant. The undoped samples showed a better hydrothermal ageing behavior at 1300°C compared to the doped samples. © (2011) Trans Tech Publications, Switzerland.


Shin B.,Pusan National University | Shin B.,Ceramics Technology Group | Lee H.,Pusan National University
Journal of Ceramic Processing Research | Year: 2014

WO3-TiO2 catalysts were prepared by an incipient wet-impregnation method for high-temperature selective catalytic reduction (SCR) of NOx. Structure, surface acidity, and catalytic performance of SCR catalyst according to WO3 content (4, 6, 8, and 10 wt.%) were characterized by morphological and spectroscopy analyses. The 10 wt.% WO3-TiO2 catalyst had high conversion efficiency due to the improvement of specific surface area, catalytic acidity, and monolayer capacity of TiO2 support. It was found that tungsten oxide species are dispersed in the interlayer between the grain and the grain boundary of TiO2 support in transmission electron microscopy. The WO3 affected the suppressed grain growth and the improved Brønsted acid sites that could provide much surface acidity by the grain boundary reinforcement. The structural interaction between the proper WO3 content and TiO2 support led to the existence of octahedrally and tetrahedrally coordinated WO3 structures on the surface in the Raman spectra. The enhanced catalytic activity of 10 wt.% WO3-TiO2 is attributed to the increase of the surface acidity (Brønsted acid sites) by the shell formation of WO3 species. © 2004 Hanyang University. All right reserved.


Niakan A.,University of Malaya | Ramesh S.,University of Malaya | Tan C.Y.,University of Malaya | Hamdi M.,University of Malaya | Teng W.D.,Ceramics Technology Group
Applied Mechanics and Materials | Year: 2013

Sintered bone is composed predominantly of hydroxyapatite (HA), which is a phase of calcium phosphate. The properties of porous hydroxyapatite (HA) produced by heat treatment of bovine femur bone were evaluated over different temperatures between 400°C and 1200°C. The sintered body was investigated by using a number of physicochemical methods such as scanning electron microscopy (SEM), SEM in combination with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD). The XRD results indicate that the annealing process enhanced the crystalline grade of HA phase in the bone matrices particularly when sintered above 700°C. There was no secondary phase formation in bones sintered between 600°C and 1000°C. However, decomposition of HA to form of β-TCP was observed during heating at high temperature which are 1100°C and 1200°C. © (2013) Trans Tech Publications, Switzerland.


Ubenthiran S.,University of Malaya | Ramesh S.,University of Malaya | Tan C.Y.,University of Malaya | Teng W.D.,Ceramics Technology Group
Applied Mechanics and Materials | Year: 2013

In this study oxygen vacancy concentration on 3Y - TZP ceramics was compared for sintered and aged samples in air and argon gas atmosphere. The sintering study was conducted over the temperature range 1250°C - 1500°C. Photoluminescence (PL) spectrums of the sintered samples were taken by laser with excitation wavelength 325nm. Two distinctive sharp and broad peaks were observed for the wavelength ~ 615 nm and ~ 580 - 600nm. The sample sintered at 1250 °C showed higher oxygen vacancy in both atmospheres. At the same time, argon gas sintered sample showed higher oxygen vacancy than air sintered sample. The emission band blue shifted after 1 h ageing for the sample sintered in 1500 °C in both atmospheres. XRD results on 1 hour aged sample sintered in argon gas atmosphere showed higher monoclinic phase than air sintered sample. © (2013) Trans Tech Publications, Switzerland.


Ramesh S.,University of Malaya | Amiriyan M.,University of Tenaga Nasional | Meenaloshini S.,University of Tenaga Nasional | Tolouei R.,University of Tenaga Nasional | And 3 more authors.
Ceramics International | Year: 2011

The effect of employing a short sintering holding time of 12 min as compared to that of the commonly employed holding time of 120 min (2 h) on the properties of undoped and 1 wt% manganese oxide (MnO2)-doped Y-TZP ceramics were studied. Sintering studies was conducted over the temperature range of 1150-1600 °C. Bulk density, Young's modulus, Vickers hardness and fracture toughness tests were carried out on the sintered samples. The results revealed that the 12 min sintering holding time was effective in promoting densification of the 1 wt% MnO2-doped Y-TZP without sacrificing tetragonal phase stability or mechanical properties and incurring grain growth. Microstructure investigation by using the scanning electron microscope (SEM) of the fracture MnO2-doped Y-TZP samples which was subjected to rapid quenching in liquid nitrogen revealed distinct microstructural features believed to be associated with the presences of a transient liquid phase during sintering. A sintering mechanism was subsequently proposed to explain the densification behaviour of MnO2-doped Y-TZP ceramics. © 2011 Elsevier Ltd and Techna Group S.r.l.

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