Materials Science Forum Vol. 819

Abstract: Synthesis of LaYO₃ was carried out via conventional solid state reaction method. The polycrystalline samples were sintered at temperatures in the range of 1300 °C to 1500 °C with each deviation is 50 °C. X-ray diffraction (XRD) analysis indicated that the perovskite ceramic obtained its single phase at 1500 °C with ordered monoclinic perovskite structure. The pure phase sample showed 98.79 % relative density and scanning electron micrographs also proved that the porosity of the sample reduced when sample undergo sintering.

Abstract: Porous ceramics have a great potential to be utilised for adsorption purposes. In this study, the effects of fly ash addition in porous clay-fly ash composites via polymeric replica technique were investigated. The results shows that the fly ash addition from 1:1 to 1:1.5 (clay:fly ash ratio) have promoted favourable results for compressive strength (0.228-0.284 MPa), porosity (97.0-97.4 percent) and densities (2.358-2.439 g/cm³) respectively. When the fly ash ratio addition was increased up to 1:2 (clay:fly ash ratio), the compressive strength (0.18 MPa) reduced significantly. However, the density was bounced back to 2.404 g/cm³ at the same ratio. This condition was occurred due to high concentration of mineral contents when fly ash addition has increased. Based on XRD pattern, the intensities between mullite and quartz was reduced when clay:fly ash ratio increased from 1:1 to 1:1.5. As the clay:fly ash ratio was increased up to 1:2, the intensities of mullite and quartz showed an increment in XRD pattern. However, there were only 4 percent of changes in porosity when the fly ash addition was 1:2 (clay: fly ash ratio). The reticulated structures of porous clay-fly ash composites were similar although fly ash addition has increased from 1:1 to 1:2.

Abstract: Ultra-fine powder of Ba (Ce,Zr)O₃ was prepared by a sol-gel method using metal nitrate salts as pre-cursor. The powder was compacted using hydraulic press with pressure of 45 kg/m² for 5 min to produce four different pellets. They were sintered at two temperature profiles using two-step sintering (TSS) process. The first temperature profile was fixed at T₁ = 1450°C and the second temperature profile was varies from T₂ = 1300°C, 1350°C and 1400°C, respectively. For a comparison, the pellet was also sintered using conventional step sintering (CSS) with temperature of T = 1450°C. Scanning electron microscope (SEM) images for the fracture surface showed that the grain growth for the pellet sintered at T₂ = 1350°C was suppressed compared to others. Majority of it grain size was in the range of 100 to 390 nm. For densification study, all the pellets sintered using TSS profile exhibited lower density than CSS method. Even though TSS method can retard the grain growth but in terms of densification, CSS method is better than TSS.

Abstract: RHA has become an important competitive material for preparation of silicon compounds due to high surface area, high grade of amorphous form silica and fine particle sizes. The effect of mould pressure (MP) and substitution of quartz by RHA on bulk density and compressive strength of porcelain body is investigated. RHA is used as a substitute for quartz with different replacement levels (0 wt% - 25 wt%). The samples are pressed into pellets at a mould pressure of 31 MPa, 61 MPa, 91 MPa and 121 MPa. All the pellets are sintered at the temperature of 1200 °C for 2 hours soaking time and at a heating rate of 5 °C per minute. The bulk density and compressive strength are measured at the highest value of 2.42 g/cm³ and 39 MPa for the sample pressed at 91 MPa with the substitution of 20 wt% RHA. The improvement in the properties could be attributed to the sharp changes in the microstructural features as a result of an increase in mullite and glassy phase simultaneously.

Abstract: BaCe_0.54Zr_0.36Y_0.1O_2.95 (BCZY10) ceramic powder was synthesized by a modified sol-gel method using metal nitrate salt as pre-cursors. The sample was prepared using three different types of surfactants namely polyethylene glycol (PEG) 6000, sodium dodecyl sulphate (SDS) and cetyltrimetylammonium bromide (CTAB). Thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectrometry was used to analyze the thermal decomposition of the dried (T=325 °C) and calcined (T=1100 °C) powder. Standard sample prepared without surfactant is denoted as A1 while the sample that prepared using PEG, SDS and CTAB as surfactant was denoted as A2, A3, and A4 respectively. TGA results indicate that all the samples were almost completely decomposed at ~800 °C except for A2. It showed the lowest thermal decomposition temperature T_td=739 °C. The highest total weight loss ~94.7% is shown by sample A4 than others. The sample with the presence of surfactant exhibits faster reaction rate for the first decomposition stage which is t = 8 min, 11 min, and 13 min for sample A2, A3, and A4 respectively compared to A1 (t = 18 min). The A2 sample shows faster reaction rate indicates that BCZY10 compound might be formed earlier faster due to the long carbon chain posses by PEG surfactant. The higher number of carbon chain present in the surfactant may accelerate the combustion process and the formation of metal oxide compounds. FTIR spectra illustrated that the carbonate residue still remained in all the samples even after calcined at 1100 oC. This result indicates that the used of surfactant does not give a significant effect on preventing the formation of BaCO₃. However, the intensity of metal-oxygen band at ~450 cm^-1 become stronger indicates that the formation of BCZY10 compound was being enhanced.

Abstract: Porous cordierite is an advanced ceramic which is popular for its interesting properties such as excellent thermal stability, high refractoriness and low dielectric constant. In this study, samples have been prepared by the mixture of aluminium nitrate nonahydrate, magnesium nitrate hexahydrate, tetraethylorthosilicate (TEOS), ethanol and nitric acid through sol-gel route. Corn and potato starch were used as pore forming agent. The amount of pore forming agent added was varied according to their weight percent (5wt%, 10wt%, 15wt% and 20wt%). The solution was then dried in oven at 90°C before sintered at 1350°C. Particle size analyzer was used to characterize the properties of pore forming agents. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were done on the produced samples. XRD results proved that all the samples produced were pure α-cordierite without the presence of other impurity or pore forming agent. From SEM results, samples using potato starch as the pore forming agent have pore size larger than corn starch due to the larger particle size of potato starch. Majority of the samples show interconnectivity among pores. The pore shape produced by potato starch is in prolate shape whereas for corn starch is in polyhedral shape.

Abstract: The interlayer mixing of layered rock salt cathode materials LiNi_0.7Mn_0.1Co_0.2O₂ that prepared by mixed hydroxide method at various temperatures (750-950°C) has been studied. X-ray Diffraction (XRD) was used to determine a suitable temperature range to obtain the fully reacted sample. Phase of pure sample was obtained at high temperature above 850°C. The results of XRD show that the LiNi_0.7Mn_0.1Co_0.2O₂ samples are iso-structural with α-NaFeO₂ with space group of R-3m.The sample that heated at 900°C exhibits a well-ordered and lower cation mixed layered structure than others. Rietveld refinement using XRD data was used to determine the amount of interlayer mixing vary as a function of temperature. Refinements data showed that the interlayer mixing varies depend upon the synthesis temperature and the optimum temperature to prepare LiNi_0.7Mn_0.1Co_0.2O₂ with the lowest amount of interlayer mixing was 900°C.

Abstract: The effect of Si particulate addition on the commercial Sn-Cu-Ni solder system (SN100C) solder alloy has been investigated. The SN100C/Si composite solder was fabricated via powder metallurgy (PM) technique. In this study five different Si composition chosen were (0 wt. %, 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, and 1.0 wt. %). The results indicated that adding a small amount of Si particulate can slightly improve the physical properties of the composite solder compared to monolithic solder alloy. Microstructural analysis revealed the reinforcement seen well distributed between the grains boundaries with additions of 1.0 wt. % resulted with highest hardness value.

Abstract: This research has investigated the properties of low-silver Sn-1.0Ag-0.7Cu (SAC107) alloy. Different weight percentages (0, 0.25, 0.5, 0.75 and 1 wt. %) of silicon nitride (Si₃N₄) were used as reinforcement particles. The SAC107 - Si₃N₄ composite solder was fabricated via powder metallurgy (PM) technique. The results showed that homogeneous distribution of Si₃N₄ particles along the grain boundaries has increased the hardness of the SAC107 - Si₃N₄ composite solders compared to monolithic SAC107 solder alloy. The melting temperature is maintained at the SAC107 level, indicating that the novel composite solder is suitable for existing soldering process.

Abstract: Lanthanum doped barium titanate (BaTiO₃) were studied for high-K dielectric and exhibit a relaxor ferroelectric properties and it can be prepared by using various method. Relaxor ferroelectric offers a wide temperature and frequency range of application for materials with high dielectric constant for microelectronic application. This paper reviews the preparation methods, the important features, advantages and limitation for the lanthanum doped barium titanate. Thus, the phase purity and mixture selected also been review on the second part of the article. The article concludes with a brief discussion of the methods with good dielectric behavior. The objectives of this paper are to determine the selection of suitable preparation methods and the properties of the high-K dielectric based on pure barium titanate and lanthanum doped barium titanate.