Abstract: The continued growth of the world construction sectors has resulted in high demand for concrete materials. The innovation of using filler as a replacement for cement is becoming a trend in order to reduce the cement consumption and provide benefit in various ways. Hence forth, 10% of cement was replaced by the calcium carbonate (CaCO3) in this study. CaCO3 is a natural material, which has a finer particles size as compared to the cement particles. This improves particle packing of concrete and give spacer effect. The concrete with CaCO3 replacement possess a higher slump, which increased the workability. The specimens were prepared in 150mm x 150mm x 150mm mould. At 28 days, the water absorbed by hardened concrete was lower for CaCO3 as microscopy analysis indicates very low porosity in CaCO3 concrete. Mechanical properties tests were conducted in 3, 7 and 28 days. The CaCO3 helps to increase the early strength, due to the accelerator effect and high rate of hydration which hardens the concrete quicker. At matured age, the concrete with the CaCO3 addition exhibits lower strength as compared with concrete without CaCO3, but still within the target strength.
Abstract: There has been an increased interest in improving the properties of alumina ceramic to be used in nuclear applications. This paper focuses on the effect of electron beam irradiation on the morphology of alumina ceramic. Alumina ceramic pellet was prepared by compacting of fine alumina powder then subjected for sintering process at 1500oC for 2 hours using electrical heating furnace. Then, the pellets were irradiated with electron beam of total dose 200 kGy with vary of electron beam speed of 100kGy/pass and 25kGy/pass. Scanning Electron Microscope and Atomic Force Microscope were used to observe the morphology of the sample. The results show that the irradiation changes the grain of the alumina ceramic due to bonding of particles caused by energy from electron beam especially at high speed. Furthermore, the surface roughness decreases after irradiation and become lower at low speed. Finer grain is obtained on the surface after irradiated at lower speed. The high energy of electron beam destroyed the particles during long contact period to the surface when low speed of electron beam is applied.
Abstract: Conventional concrete does not have durability and higher strength as produced by high performance concrete (HPC). It is known that the HPC possess the following three properties which are high workability, high strength, and durability. The introduction of polycarboxylate ether (PCE) superplasticizer was proved to enhance the workability of concrete even though at a lower water to cement ratio. The study was conducted to find the optimum dosage of PCE and to compare its compressive strength, physical characteristics and morphology of the HPC. The result of the test shows that the high performance concrete (HPC) with addition of 0.5% polycarboxylate ether (PCE) superplasticizer of the cement mass have the highest compressive strength and excellent physical properties.
Abstract: Fast depleting natural resources, huge consumption of energy, and environmental hazards involved in the production of cement has inspired researchers to find partial replacement of cement using other or similar materials. Rice husk ash (RHA), an agricultural waste, is classified as “a highly active pozzolan” because it contains a very high amount of amorphous silica and a large surface area. Rice husk is natural fiber that has the advantages of low density, low cost and biodegradable. In Malaysia paddy is grown locally especially in northern states of Peninsular Malaysia. Rice husk is a by-product of paddy being process into rice. These make it a natural candidate for cement replacement agent especially in Paddy producing countries. In this paper, RHA was introduced as the micro filler in concrete mixtures. The replacement of RHA which is lighter as compared to the Ordinary Portland Cement results in decreasing density of cement fiber composite and less permeable concrete.
Abstract: Varistor with TiO2 as the base and SiO2, WO3 and Bi2O3 as dopants were investigated to create a low voltage varistor. The physical, mechanical, microstructural and electrical properties were studied where the concentration of SiO2 was varied but the concentration of WO3 and Bi2O3 was fixed. Physical and mechanical characterization consisted of green and fired density, axial and radial shrinkage and Vickers Hardness. Electrical evaluation on the other hand consisted of non-linear coefficient, breakdown voltage, power loss and clamping ratio. Non-linear coefficient of 2.16, very low breakdown voltage of 5.538V/cm and minimal power loss of 0.0124mW was achieved. It was found that optimum results were achieved with 98.3% TiO2, 0.7% SiO2, 0.5%Bi2O3 and 0.5%WO3.
Abstract: Concrete is a common material that widely used in construction industry. Excessive usage of this material causes exhaustibility to its components, especially fine aggregate or sand. In this regard, the use of manufactured sand is considered as a part of the solutions to fix this problem as it is readily available. In this research, the manufactured sand is used at 40%, 50% and 60% to replace natural river sand. SEM analysis reveals the rough surface texture of manufactured sand. The manufactured sand has angular shape and sieve analysis reveled that it has a considerable amount of fine particle. Slump test shows that concrete using manufactured sand pass the standard. On the other hand, compressive test shows that concrete cubes using manufactured sand do not achieved the target strength. Water absorptive test on the cubes revealed that M-Sand I has higher absorptivity property compared to river sand . SEM analysis revealed the existance of microcrack as well as porosity in in concrete cubes incorporating of manufactured sand. It can be concluded that it can be concluded that the higher the percentage of manufactured sand in the concrete mix the lower is the comprensive strength.
Abstract: Research in the area of alloyed deposition on ceramic particles is gaining widespread acceptance in tribology community to produce advanced wear-resistance surfaces by environmentally acceptable coating technologies. In this study, autocatalytic electroless deposition technique was used to incorporate hexagonal boron nitride (hBN) lubricant particles in nickel-phosphorous matrix. The substrate particles were subjected to series of pretreatment operations prior to electroless co-deposition process. Surface morphology and composition of pure hBN and treated powders were characterized by means of scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and field emission scanning electron microscopy (FESEM). The results revealed that the pretreated particles have rough and increased surface area that aided deposition process. It was also found that uniform Ni-P alloy layer was successfully synthesized on Ni-coated hBN powder. Thus, the developed electroless co-deposited hBN composite powder may be regarded as an advanced solid lubricant material coating which may either be directly applied on the sliding mating surfaces or deposited by laser-cladding, TIG torch melting or thermal spaying, etc to improve the surface properties of metallic substrates against wear and friction for high temperature applications.
Abstract: Abundance in aluminum scrap metals can cause problem such as limited space allocation and pollution. The solution to solve these problems were by recycling the aluminum scrap metal as secondary production of aluminum. Among the recycling process alternative is smelting, However, the process consumes high energy with low productivity. This study focuses on alumina production from aluminum scrap waste. Dissolution process of Al scrap with 0.5M sodium hydroxide (NaOH) yields Al (OH) 3 and hydrogen gas. Results show that the temperature gradually decreased from 40°C to 35.7°C as the reaction took place. The pH of the solution during dissolution process increased from 12.08 to 12.38. The XRD results show that after calcination of Al (OH)3 powders at 1500°C, α-Al2O3 peaks could be observed. SEM morphology shows that the calcination process changes the Al (OH)3 powders from hexagonal shape to form α-Al2O3 with rounded shape.
Abstract: Metal matrix composites are attractive light weight materials with potential attributes to substitute automotive materials without sacrifing performance. This present study aims to investigate the wear characteristics of aluminium (Al) 6061 reinforced with silicon carbide particles (SiCp) of three (3) different particle sizes. The reinforcement consist of coarse particle (80μm), intermediate (40μm) and fine particles (15μm) particle sizes with 10, 5, 5 wt% respectively. The composite was fabricated using the stir casting technique due to its simplicity and cost effectiveness. The wear test was conducted using the pin on disc tribo-system with steel disc counter surface. The outcome of this study reveals that the MPS-SiC AMC exhibit better wear and frictional characteristics for brake rotor application. The coarse particles have better contribution to wear resistance because the possibility of particle pullout from the matrix for both intermediate and fine particles is high due to small surface contact area. However, the intermediate and fine particle compensates for multiple shielding effect for the base matrix thus influences the impact energy and mechanical strength of the composite. The friction coefficient (0.32 - 0.46) of the MPS-SiC AMC falls within the acceptable deviation band for automotive brake rotor application
Abstract: In this study various compositions in the phosphate based glass (PBG) system of (50-x)P2O5-40Ca-(5+x)Na-5TiO2 and (50-x)P2O5-40Ca-(5+x)Na-5Fe2O3, where x= 5 and 10 were investigated for glass transition temperature (Tg) via thermo mechanical analyser (TMA) and differential scanning calorimetry (DSC). The amorphous nature of the glasses was confirmed via XRD. The Tg measured via DSC was consistently higher by 19°C-29°C compared to TMA and was due to the thermal history and the heating rate of the samples. The Tg increased with increasing phosphate content in both glass systems. The Tg for Ti containing PBG was found to be in the range of 453°C-500°C whilst Tg for Fe containing PBG was in the range of 449°C-494°C. Consistently higher Tg for the Ti containing glass series compared to the Fe containing glasses may be attributed to the smaller ionic radius and therefore higher field strength of Ti4+.