Pusat Pengajian Kejuruteraan Bahan dan Sumber Mineral - Tesis

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A Study Of Corrosion Of Steels In Carbon Dioxide And Sulphide Solutions
(1993-08)
Abualmaali M. Y. Taher
The present investigation has been successful in resolving the controversy about CO2 corrosion of mild steel and 13% Cr martensitic stainless steel in brine solution with and without sulphur content. It has been observed that the corrosion behaviour of mild steel and 13% Cr stainless steel depends on the combination of CO2 pressure and sulphur content. The corrosion rate may increase or decrease depending upon a particular combination.
Assessment of electric arc furnace slag as soil stabilizer and fertilizer for mangrove seedling
(2022-02-01)
Kong, Ern Hun
Slag from Electric Arc Furnace (EAF) is generated from steelmaking processes, and it is the most in term of volume among the by-products. Production practices and processes, and the skill of operator are among the factors that will cause significant variation in chemical and mineralogical properties. Successful recycling of the slags depends on understanding the differences and how the properties can be exploited. This project aims to evaluate each of the slags and explore their potential use in agriculture as soil modifier and nutrients source. Three slag samples of NL (normal production CaO saturated slag), HM (MgO saturated slag) and HF (high Fe slag), which were taken from different points in production and practices were characterized. The experimental works were carried out purely on the raw slag from production. It was crushed, ground, and sieved into three sizes of 0.15 – 0.25 mm, 0.25 – 0.50 mm and 0.5 – 1.0 mm. The slags were characterized by chemical, mineralogical and leaching study, and then evaluated for their effects to the growth rate of mangrove seedlings in field study. Preliminary study of leaching test and consideration of environment in field study were carried out to set the parameters for field works. Leaching test was carried out to confirm the leached elements meeting the environmental regulation standard and nutrient required by mangrove seedlings. Parameters for leaching test are different pH values (distilled water 6.8, rainwater 5.78 and seawater 8.37), stirring speed (350 and 700 rpm), and duration up to 16 weeks. Meanwhile, the field study was carried out with soil from mangrove forest and nursery center, treated with the three types of EAF C slag. The result of leaching test has confirmed the maximum level of 15.8 µg/L Cr (VI) is still far below the control limit of 50 µg/L in DOE requirement in Standard B Limit as per Malaysia Environmental Quality (Industrial Effluents) Regulations 2009 and WHO advisory Cr (VI) control limit for drinking water. Meanwhile, maximum 49.7 mg/L of Si, 45.7 mg/L of Ca, 0.581 mg/L of Fe, and 19.9 mg/L of Mg obtained from elemental leaching test has confirmed the availability of elements as nutrients for mangrove seedlings. As disturbed muddy soil in mangrove forest from natural disaster or human activities would lead to formation of sulphate, creating acidic condition soil which will affect the mangrove growth, alkaline slag could be used to neutralize the soil and improve growth. Slag NL with highest alkalinity of pH value 11, capable to increase the pH value of acidic soil from 3.65 to 8.5, which provides suitable condition for nutrients uptake for seedlings. The field study showed that not all the nutrients uptake by seedlings can be correlated with chemical content in slags, but seedlings treated with slags did achieve higher growth rate compared with seedlings without treatment, especially the stem height and seedling leaf area. Magnesium saturated slag with > 8% MgO and oxidized slag with > 35 % FeO is suitable for acidic muddy soil as they would enhance the leaf growth of seedlings. The highest leaf generation rate of 195.3 mm2/day, was achieved by seedling in soil MF treated with slag HF which contain 39.9 % of FeO compared with 164 mm2/day of leaf area generation in seedlings without slag treatment. The highest stalk growth rate of 3.73 mm/day was achieved by seedlings in soil NC treated with slag HM which contain 11.4 % MgO compared with 2.77 mm/day in seedlings without slag treatment. Based on this study, EAF C slag has great potential as soil modifier and nutrients source for mangrove seedlings in nursery center, and this re-use of slags is safe and would not leach out harmful elements into the environment.
Bioactive glass-cordierite ceramics for biomaterials application
(2022-06-01)
Mohd Mokhtar, Ahmad Kamil Fakhruddin
Bioactive glass (BG) is one of the biomaterials that are widely used in various biomedical applications such as dental implant, due to its excellent ability to bind with tissue through a bonding formation with apatite layer. However, BG demonstrated low mechanical strength to withstand external force. In this study, bioactive glass-cordierite ceramic (BG-cord) composite was developed to overcome this issue. BG and cordierite were synthesized using glass melting method prior to BG-cord fabrication in pellet shape. In the fabrication process, the milling time of cordierite (0.5 to 5 h), the composition of BG and cordierite, and the sintering temperature of BG-cord (600 – 1000 ºC) were studied. An improvement in the mechanical properties of BG was observed with the addition of cordierite, proven by the superior diametral tensile strength (DTS) of BG-cord to BG. The DTS of BG increased from 6.29 MPa to 14.01 MPa upon milling with 30% cordierite for 3 hours. A further increase in DTS value from 14.01 MPa to 30.54 MPa was recorded when the BG-cord was sintered from 600 °C to 925 °C. The optimum BG-cord exhibited physical characteristics of 2.33 g/cm3 bulk density, 8.92% porosity, 30.54 MPa DTS, 93.75 MPa compressive strength, and 153.93 Hv hardness. A positive response of bioactivity performance was observed in the BG-cord with apatite formation as detailed in the in-vitro analysis using scanning electron microscope (SEM). X-ray diffraction (XRD) analysis revealed apatite peaks proved the formation of apatite. The increase of intensity of P-O and C-O spectra from Fourier transform infrared (FTIR) analysis after bioactivity test also proved the apatite formation. As a conclusion, the BG-cord produced from the current study has potential application as a dental implant material.
Biodegradation of natural rubber latex films filled metroxylon sagu pith waste by immobilised bacillus cereus
(2020-09-01)
Adzami, Nuraiffa Syazwi
The accumulation of NR gloves for biodegradation is occurred continuously at the disposal site due to the slow biodegradation process. The incorporation of treated sago pith waste (TSPW) in natural rubber (NR) latex films were prepared to enhance the biodegradability of the films. Bleaching treatment and ball milling were carried out to treat the TSPW as filler for NR latex films. The rubber-degrading bacteria is identified to monitor the biodegradation of films. Two types of system with freely suspended bacteria and immobilised bacteria through batch study were studied and the culture conditions were optimised. It was found that TSPW filled NR latex films showed optimum mechanical properties and good colloidal stability of the NR compound. Tensile strength and tear strength were recorded as 23.83 MPa and 63.87 N/mm. Bacillus cereus ATCC 14579 (B. cereus) is identified to utilize these films as the sole carbon and energy sources. Granular activated carbon (GAC) is used as adsorbent to adsorb B. cereus. This system called B. cereus-GAC system followed Freundlich isotherm and Pseudo-second-order kinetic model. In 14 days of biodegradation, both systems show significant weight loss and mechanical properties reduction of TSPW filled NR latex films as compared to unfilled NR latex films. Thus, TSPW filled NR latex films and B. cereus have the potency to provide a biotechnological solution to the waste NR gloves disposal problem.
Cdse and tio2 photoanode by electrophoretic deposition for quantum dot sensitized solar cell
(2020-07-01)
Hay, Mar Aung Kyaw
CdSe nanoparticles was used as a photon sensitizer in quantum dot sensitized solar cell (QDSSC). Mesoporous structure is desired for TiO2 wide band gap semiconductors to provide large surface area for absorption of more QDs in harvesting visible light efficiency. Common method to make QDSSC is to complete the CdSe with TiO2 for charge transfer. But, the problem with this system is that photoexcited electron need to travel a long pathway (the thickness of TiO2) before its reach to the conductive substrate, where the photoexcited electron is susceptible to recombination with the sub-band gap state of TiO2. Mixed CdSe-TiO2 photoanodes will create efficient electron injection from CdSe conduction band to the TiO2 electrode effectively in order to reduce the recombination and improve the efficiency. In this research, CdSe nanoparticles were synthesized by hot injection method and using different amount of TOPO ligand. CdSe nanoparticles were dispersed in chloroform after purification process. 8 g TOPO amount of CdSe were used for deposition process. CdSe was deposited on fluorine doped tin oxide (FTO) substrate by using electrophoretic deposition method (EPD) with various EPD parameter. CdSe was deposited on TiO2 film and mixing CdSe-TiO2 were deposited on FTO substrate. TiO2 nanoparticles were successfully prepared by modification using both propionic acid and n-hexylamine and TiO2 nanoparticles dissolved in chloroform. TiO2 was deposited on fluorine doped tin oxide (FTO) substrate by using electrophoretic deposition method (EPD) with various EPD parameter. For CdSe/TiO2 film, TiO2 was deposited on FTO first then this film was heated 450 °C for 3 hours. Then, CdSe was deposited on heated TiO2 film. For mixed CdSe-TiO2 films, CdSe and TiO2 was mixed together and deposited on FTO substrate. CdSe/TiO2 film and mixed CdSe-TiO2 film were prepared by EPD method as photoanode. For QDSSC, CdSe/TiO2 film and mixed CdSe-TiO2 film was used as photoanode, copper (II) sulfide (Cu2S) as counter electrode and was used polysulfide electrolyte. These photoanode, counter electrode and electrolyte were assembled for I-V and EIS measurements. The highest efficiency of CdSe/TiO2 film was 2.1% and 0.04% for the mixed CdSe-TiO2 films. From the result of EIS measurement, the Rct value of CdSe/TiO2 films and mixed CdSe-TiO2 films were 51 Ω and 75 Ω. Thus, the CdSe/TiO2 films produced higher efficiency than mixed CdSe-TiO2 films in QDSSC application.
Characterization of rubberized asphalt binders containing tough fix hyper used in asphalt mixture and crack sealant
(2020-08-01)
Poovaneshvaran, Sharvin
Application of conventional asphalt binder has certain limitations due to its rheological weakness. Under severe weather condition and excessively high traffic loadings, application of conventional asphalt binder in asphalt pavement can cause deformation under high temperature, premature cracking, and high temperature susceptibility. This had sparked the interest of researchers to incorporate polymers in asphalt binder in order to improve the limitations of conventional asphalt binder. The primary intention of this research is to produce rubberized asphalt binder with the incorporation of Tough Fix Hyper additive. The modified asphalt binder was evaluated for the purpose of pavement construction and road maintenance. This research is divided into three different stages based on evaluated material. The first stage will mainly focus on the assessment of rheological and physico-chemical properties of asphalt binder produced via wet process. While the second stage emphasis predominantly on the mechanical properties and qualitative assessments of asphalt mixture. Finally, the third stage focus on the performance evaluation of crack sealant material. Also, the usage of rubberized asphalt mixture towards environment was addressed via toxicity characterization leaching procedure. The results of rheological properties indicate that crumb rubber, natural rubber latex and Tough Fix Hyper has significant effect on the characteristics of asphalt binder. The addition of rubber modifiers and Tough Fix Hyper enhanced the rheological behavior of asphalt binder which is essential in producing high grade asphalt pavement. Moreover, the modified asphalt mixture’s performance test exhibited better stiffness and strength properties, good resistance to rutting, fracture and moisture damage. The sealant material performance tests indicated that the rubberized asphalt sealant material is capable of overcoming the vertical and horizontal movement by attaining good tensile strength and shear strength. The research findings also proved that there is no tendency for heavy metal to leach and pollute the environment. In conclusion, the crumb rubber and natural rubber latex modified asphalt binder with the incorporation of Tough Fix Hyper could produce high-grade asphalt binder and asphalt mixture, which are suitable to be used as pavement construction and road maintenance material.
Characterization of sn-3.0ag-0.5cu/cu solder joints by microwave hybrid heating with silicon wafer susceptor
(2022-09-01)
Said, Mardiana
Microwave hybrid heating (MHH) is a new alternative to overcome longer heating utilized by conventional method in soldering process which contributed to excessive intermetallic compound (IMC) growth. This study uses silicon wafer as a susceptor in the MHH system and focuses on MHH parameters, post aging and corrosion characterization in comparison to conventional method. Solder alloy Sn-3.0Ag-0.5Cu (SAC305) was selected and successfully formed solder/substrates joint which are SAC305/Cu and Cu/SAC305/Cu. For comparison, conventional reflow oven was set at reflow temperature of 250°C for 60 s (coded as CR). The best solderability characteristic by MHH was observed at high operating power, 40 s (coded as H40). The H40 shows a more refined Cu6Sn5 IMC structure with smaller grain size and a thinner layer (2.5 µm) compared to CR (3.7 µm). The ultimate tensile strength (UTS) of H40 (44.7 MPa) is 36.7% higher than CR (32.7 MPa) and they decreased consistently at long-term aging for both CR and H40. Pitting characteristics and corrosion products such as SnO, SnO2 and Sn3O(OH)2Cl2 were observed after one dayof immersion in 3.5 wt.% NaCl. They keep expanding until the pitting surface is fully covered with corrosion products and inhibited corrosion activity. Thus, UTS reduction can be reduce from 30-40% to less than 10% after 14 days of immersion. The Si wafer susceptor was successfully form a solder joint by MHH. The solder joint performance by MHH after aging and corrosion showed higher joint strength compared to conventional method. The findings from this research work could introduce a better soldering technique and a remarkable performance in lead free soldering industries.
Chitosan coated on treated poly(lactic acid)beta-tricalcium phosphate scaffolds incorporated with dexamethasone loaded poly(lactic acid) microsphere
(2020-10-01)
Isa, Rosaniza Md
Poly(lactic acid) (PLA) is extensively used for tissue regeneration owing to its excellent biocompatibility, biodegradability, durability and cost effectiveness. However, PLA scaffold based biomaterials have some shortcomings such as their inherent brittleness, slow degradation rate and lack of bioactivity, which restricts their application in hard tissue engineering. Hence, PLA based composites scaffold are getting acceptance for this applications. The main objective of the study is to produce PLA/β-TCP scaffolds. Chitosan layer was coated on the scaffold to reduce the brittleness and Dexamethasone (Dexa) as antibiotic was loaded in the PLA microsphere to avoid the infection during surgeries process. PLA/β-TCP scaffolds were fabricated by using a combined solvent casting and salt leaching method. Dexa loaded in PLA microspheres were fabricated by double emulsion and solvent evaporation method. Surface modification of the scaffold was carried out to improve the surface wettability and bioactivity of PLA/β-TCP scaffolds. Results showed that the addition of β-TCP offers a 39.3% improvement in compressive strength and hydrophilicity to the scaffolds. Surface treatment using silane indicates significant improvement compared to that of NaOH treatment. The compressive strength of the treated PLA/β-TCP scaffold with 2 v/v% silane improved by 50%, with 34% reduction of water contact angle value compared to untreated scaffolds. It is found that an increase in compressive strength of PLA/β-TCP scaffold was achieved at 1.5 w/v% of chitosan coating solution. Significantly, the chitosan was able to penetrate some micropores and small cracks in the struts which resulted in an increase of about 64% of compressive strength of the scaffold. For drug delivery, results showed that chitosan coating on treated scaffolds with Dexa loaded PLA microsphere played significant role in combating infection by prolonged time of drug release and increased the protein adsorption. In short, chitosan coated on treated scaffolds with Dexa loaded PLA microsphere holds great potential to provide mechanical support for tissue regeneration with similar chemical composition to human bone and controlled drug delivery function for bone tissue engineering.
Comparative Study On The Sintering Of Calcium Phosphate Ceramic By Conventional And Microwave Sintering
(2014-12)
Mangkonsu, Chuthathip
Sintering of calcium phosphate bioceramic were performed using microwave and conventional furnaces. The calcium phosphate precursor was used as raw material powder. Sintering of biphasic calcium phosphate (B'Cl") was successful using both sintering methods. The precursor powder was characterized by XRO, TG/ ose and particle size analysis. Sintering was done at different temperatures (1200 oe, 1250 oe, 1300 oe, 1350 oe, and 1400 Oe) using conventional and microwave furnaces. For the microwave sintering, the firing process was stopped, when the temperature reached at 1350 oe because the specimens cracked and the surfaces were damaged especially on the edge of specimens. Then the Bep specimens were characterized by XRO and FESEM while physical properties measured include density, porosity and linear shrinkage. The mechanical properties of bulk Bep were determined by using Micro Vickers hardness and diametrai tensile strength (OTS). The comparison on properties was carried out on specimens sintered at the same temperature using both methods. The XRO results showed that the f3-TCf' to (l-TCf' transformation phase occurs above 1250 oe in both sintering furnaces.
Development of biodegradable polybutylene adipate terephthalate/ polybutylene succinate polymer composite incorporated with modified rice husk and starch
(2021-12-01)
Yap, Saw Yin
The present work deals with the fabrication and characterization of biodegradable polymer with 30%-40% rice husk waste filler and a 70%-60% of Polybutylene succinate (PBS) and Poly butylenes/ adipate terephthalate (PBAT) to achieve a balance within the mechanical properties, biodegradation percentage and costing. The rice husk was successfully modified with different amounts of glycerol to ease the composite fabrication process. The results reveal that the rice husk: glycerol ratio at 100: 10 obtained the optimum mechanical properties (tensile strength: 16.35MPa, Young’s modulus: 279.61MPa, elongation: 41.2%, water absorption capacity (3.98%) and water contact angle (113.9°). PBAT composites exhibited comparable tensile strength, lower Young’s modulus but higher elongation at break as compared to PBS composites due to intrinsic properties of the polymer. FTIR analysis revealed no significant difference between modified rice husk (MRH) composites and modified starch (MS) composites because rice husk and starch are organic-based fillers having similar functional groups. The use of 40% high filler content for PBAT composite fabrication with and without compatibilizer was investigated. The tensile properties of compatibilized composites showed significant improvement due to good fibers-matrix adhesion. Optimization of the ratio PBAT: PBS to 36:24 expedited the biodegradation rate of the samples. PBAT: PBS blends with a 36:24 ratio showed 97.06% mass loss for MS and 92% for MRH, evidencing itself as a biodegradable material. A comparable amount of PBAT and PBS allowed the formation of co-continuously phases to improve the mechanical properties. The bio-composite Mg-36PBAT/24PBS/MRH10-40F possessed good mechanical properties such as tensile strength (14.27MPa), Young’s modulus (200.43MPa) and elongation at break (12.99%), which is adequate for the manufacturing of molded products such as a tray, lunch box, and straw.
Development of multi-doped carbonated hydroxyapatite (cha) porous scaffolds for bone substitutes
(2020-04-01)
Muhammad Syazwan Mohd Noor
Incorporation of dopant elements into apatite structure is a great interest for biomedical applications due to its composition closely mimic to the human bone mineral. The goal of this study was to synthesize a range of multi-doped Carbonated Hydroxyapatite (MgCoSr CHA) powders via nanoemulsion method at room temperature (RT). Magnesium (Mg), cobalt (Co) and strontium (Sr) ions were introduced into the apatite structure to enhance its physical, chemical and and biological properties at the same time imitating natural bone composition. The amount of Mg2+ was varied at three different concentrations (0.60, 0.65 and 0.70 wt%) with fix ratio of Co2+ and Sr2+ in producing MgCoSr CHA powders. It can be reported that all the synthesized powders remained as B-type CHA. Interestingly, it was also found that the increment in the percentage of CO32- for MgCoSr CHA and it promotes the formation of needle-like structure as compared to CoSr CHA and CHA powders. The interconnected CHA porous scaffold was then fabricated by polyurethane (PU) foam replication technique followed by sintering at 800°C and cooled down under wet CO2 at 250°C. The optimum scaffold was produced by using slurry composition made of as-synthesized powder, 5 wt% of kaolin, 1 ml of dispersing agent, PEG:PVA ratio (2:3) and 5 wt% of K2CO3 as sintering aid. Fabrication of multi-doped CHA porous scaffolds were then performed using the optimum condition of this slurry composition. These multi-doped sintered scaffolds showed decrease in the carbonate content as compared to CHA scaffolds, however still fall in the range of carbonate content found in human bone mineral (2-8 wt%). Despite this, the compressive strength of the multi-doped CHA porous scaffolds (E31) is higher (0.53 ± 0.12 MPa) than E21 (0.38 ± 0.04 MPa) and E11 (0.50 ± 0.05 MPa). In vitro bioactivity revealed E21 (CoSr CHA) and E31 (MgCoSr CHA) have higher bioactivity, resulting in fast apatite formation after day 14. At this stage of the study, it can be highlighted that the incorporation of multi-divalent cations as well as carbonate ions play important roles in enhancing the properties of HA-based materials.
Development Of W03-Tio2 Nanotube Arrays For Water Electrolysis
(2013-03)
Lai Chin Wei
Solar hydrogen generation from water electrolysis is a key target for the development of sustainable hydrogen economy for future energy system. The formation of self-organized Ti02 nanotubes without bundling is essential for high efficiency In photoelectrochemical (PEC) water electrolysis application. Comprehensive investigations on different parameters, such as composition of electrolyte, anodization time, anodization voltage, anodization temperature and heat treatment temperature were conducted in order to control the specific architecture of nanotubes.
Differential weathering effects on macro-micro failure characteristics of sandstone in semi-arid region
(2022-08-01)
Sultan Shah, Kausar
The significance of rock failure can be found from the fact that microfracture genesis and coalescence in the rock mass results in macroscale fractures. Rock may fail due to an increase in local stress, natural fractures, and weathering inducing micro crack genesis, coalescence and propagation. Understanding the effect of loading and weathering grade on the failure behavior of rock is critical for a wide range of engineering applications. Therefore, this research work aims to elucidate the micro and macroscale failure behaviour of sandstone under quasi-static loadings from weathering zones. The microscale failure response of various weathering grade sandstones was studied under wet and dry cycles. Each sample was tested for microstructures and microfracture characteristics using image analysis. Furthermore, the obtained micrographs were also used to create microstructure-based models, which were then simulated in ANSYS software. The findings indicate that wet and dry cycles have insignificant impact on particle shape and size. However, the variation in particle shape and size implies that this is a result of the prevailing interaction of rock and water. The microscale simulation revealed that as the density of microstructures increases, the chances of primary fracture deviation from the loading axis increases. The effect of loading rates (i.e., 0.001 kN/s, 0.01 kN/s, 0.1 kN/s, and 1 kN/s) on the mechanical behavior and fracture response of sandstones with varying weathering grades were then examined. The results revealed that the tensile strength of sandstone is equally sensitive to loading rate and weathering grade. Brazilian tensile strength (BTS) test has shown strong relationship with sandstone fracture characteristics. Additionally, the fracture characteristics of sandstone are randomly related to the loading rate and are depending on the weathering grade. The findings indicate that fracture deviation area (FDA), fracture angle (FA), and fracture maximum deviation distance (FMDD) was unclearly associated with particle shape or size. In contrast, fracture length (FL) increases with an increase in particle size. The impacts of cemented and stained natural fractures on stress-induced sandstone failure mechanisms and mechanical behaviour was performed under unconfined compressive strength (UCS) tests. ANSYS software was used for 3D fracture modelling and simulation. The numerical simulation findings demonstrated that UCS of sandstone declined with increasing fracture angles of 0°, 30°, 45°, 50° to 60°, respectively. The specimens with 0° and 30° fractures show multiple fracture patterns, while 90° fractures exhibit axial splitting. Similarly, a 50° fracture angle specimen fails in shearing.
Effect of different body composition and firing temperature on properties of ceramic tile
(2021-05-01)
Juhari, Muhammad Syahir
Porcelain tiles have excellent mechanical strength with low porosity (almost zero water absorption), durability, chemical and stain resistance. Due to these excellent properties, porcelain tiles had successfully captured new market segments: floor and wall, adding to the strong demand in building construction. However, porcelain tile is reported to have high thermal conductivity and low solar reflectance which is reduce the thermal comfort and subsequently not suitable for building construction. Therefore, a low thermal conductivity and high solar reflectance porcelain tiles is fabricated to improve its thermal comfort by altering the composition and firing temperature of the porcelain tiles. The aim of this study is to study the effect of different body composition and firing temperature on the properties of porcelain tiles. The new body compositions of porcelain tile powder were milled and compacted at 18 MPa to obtain rectangular shape samples. The compacted samples were fired at 50°C/min up to 1200°C and soaked for 15 minutes before cooling down to room temperature. Among C1, C2 and C3 body composition, C3 show lowest fired shrinkage (7.75%), lowest bulk density (2.30g/cm3) and highest MOR (59.71 MPa) values and at the same time have the lowest thermal conductivity (1.27 W/mk) and highest solar reflectance (80% in near infrared region).Thermal conductivity and solar reflectance is govern by phase formation in which C3 composition reduced by 33% of thermal conductivity and increases of solar reflectance up to 80% (near infrared region) compared with control sample due to the formation of low thermal conductivity phase (cordierite). Since C3 sample shows the optimum properties compared with other samples, the firing temperature of the sample were altered at 1150 °C, 1175 °C and 1225 °C to observe whether it worth to improve the properties of porcelain tiles. Selection of these firing temperature were done by plotting the vitrification curve. It was observed that the thermal conductivity of C3 samples decreases after lowering the firing temperature to 1150°C. The solar reflectance also increases after lowering the firing temperature. Although C3 sample gives low thermal conductivity and higher solar reflectance values, the MOR values obtained from this firing temperature were reduced in comparison with the one fired at 1200°C firing temperature. Also, C3 sample fired at 1150 °C showed the highest water absorption value which is not appropriate for construction application. Thus, it was concluded that the porcelain tiles made using C3 composition and fired at 1200°C are a suitable candidate to fabricate porcelain tiles with good properties (high MOR, low water absorption, low thermal conductivity and high solar reflectance) for building construction.
Effect Of Mechanical Activation On The Fluxing Properties Of Gua Musang Feldspar And Granite Quarry Dust
(2013-03)
Nordala, Phoumiphon
In the present study, mechanical activation was performed on samples of Gua Musang feldspar (GMF) and granite quarry dust (GQD). At first, GMF was milled for 10, 20 and 30 minutes, at 200, 300 and 400 rpm milling speeds. The powder obtained was then formed into pellets followed by firing at 1150, 1200 and 1250°C. From the milling and firing processes, 30 minutes was found to be the optimum time for milling. Therefore, in the milling process of GQD, 30 minutes was used at different milling speeds of200, 300 and 400 rpm. It was then fired at 1150, 1200 and 1250°C. At this stage, GQD was confirmed to be a suitable fluxing material as it can form a glassy phase and lower the firing temperature. Secondly, the process was followed by forming mixtures of GMF with ball clay (BC) and silica (SC) with a weight ratio of GMF 20 wt.%, 30 wt.% and 40 wt.%. These mixtures were fired at 1100, 1150 and 1200°C. In the final part, a mixture of GQD and BC without silica (SC) were prepared due to the high amount of silica in GQD. A weight ratio of GQD 40 wt.%, 50 wt.% and 60 wt.% were chosen.
Effect Of Secondary Plastic Deformation On The Microstructures And Mechanical Properties Of Cast Ai-7Si-Mg Alloy
(2014-12)
Thuong, Nguyen Van
The purpose ofthis research is to study microstructure and hardness of AI-7SiMg alloy under different cooling slope casting conditions and equal channel angular pressing (ECAP). The effect of cooling slope casting method with varying variables, such as pouring temperature (625°C - 640°C - 660°C - 680°C), cooling slope length (150 mm - 250 mru- 350 mm) and cooling slope temperature (room temperature - 200°C - 400°C) and conventional casting method are investigated. The as-cast alloys and as-ECAPed alloys were analyzed based on Differential Scanning Calorimetry, Xray fluorescence, microstructures, hardness, X-ray Diffraction pattern, wear resistance, Secondary Electron Microscope and Energy Dispersive X-ray. Microstructure of conventional cast alloy cast at pouring temperature of 640°C was coarse and almost dendrite the structure. However, uniform, fine and globular microstructure could be obtained from cooling slope casting with pouring temperature range of 625°C - 660°C, cooling slope length range of 150 mm - 350 mm and slope temperature ranging from room temperature to 200°C_ This is due to copious nucleation occurred on slope surface and these nuclei were then detached due to the force convection during pouring process.
Effects of silane- and wax-based surfactants on behavior of latex modified asphalt binders and mixtures
(2020-08-01)
Sani, Ashiru
Modification of hot mix asphalt (HMA) with natural rubber latex (NRL) is a technology that provides significant improvements in the rutting and fatigue resistance of the conventional asphalt mixtures. It is a cost effective and environmental friendly technology that can mitigate the vulnerability of an asphalt mixture to early deterioration, as well as increasing its stiffness. However, an NRL modified HMA is prone to low workability and wettability due to its high viscosity property. Low wettability may induce reduction in the adhesion rate between an asphalt binder and the aggregate interface. Therefore, 0.1% Zycotherm (silane-based) and 0.3% Gripper (wax-based) additives were used as surfactants to enhance the 3%, 6% and 9% NRL modified asphalt binder adhesion with aggregate. In this research, the overall laboratory results demonstrated that the incorporation of surfactant posed significant influence on the rheology of the NRL modified asphalt binders. A novel approach was adopted using a micro-scale mechanism to quantify the surface morphology, chemical changes, wettability, and work of adhesion of the test specimens at different aging conditions. The influence of short-term aging conditioning and the addition of surfactants had enhanced the homogeneity and interconnectivity of the asphalt binders owing to the enhanced absorption and assimilation processes. The chemical changes evaluation showed that an increase in the bond indices (C-H and O-H) of latex-modified asphalt binders causes a simultaneous increase in its viscosity, which makes it stiffer to withstand the effect of degradation at high temperature. However, excessive stiffness and viscosity should be avoided to maintain its workability. The presence of both Zycotherm and Gripper surfactants help to adequately lower the C-H and O-H bonds within the binder to balance the adhesion force that may affect the energy required during mixing, with the Gripper providing the best results at both aging conditions. Analytical measurements based on the surface free energy (SFE) results showed that the surfactants had improved the spreadability of asphalt binder over the limestone aggregate surface. Likewise, the adhesion characteristics was improved with the addition of a surfactant. Compatibility ratio has also been used as an indicator of moisture resistance. The result indicated that limestone aggregate is less resistant to moisture damage compared to granite. The adhesive bonding results revealed that the specimens subjected to combined long-term aging and accelerated moisture conditioning are more susceptible to degradation. Specimens with granite aggregates showed a higher affinity towards binder as demonstrated by a higher tensile strength than the limestone specimen. The mixture performance tests showed that the performance of NRL modified HMA in terms of resilient modulus, dynamic creep, accumulated micro-strains, indirect tensile strength and Leutner shear is highly dependent on the presence of surfactant and NRL content. Overall, finding explained the interaction between the asphaltic materials, rubber modifier, and surfactant at micro and macro levels to enhance the durability of asphalt pavement. The presence of Gripper as surfactant in NRL modified HMA has better improved the mechanical properties of asphalt mixtures than that without surfactant.
Evaluation And Processing Of Gold At Pulai Mining, Gua Musang, Kelantan
(2014-11)
Eang, Khy Eam
Gold mining is the important activities that create economic growth and development of the country. Effective method in gold processing is the key part in gold mining. At Pulai Mining Sdn Bhd, gold recovery is poor and it is believed that some percentage of gold lost into the tailing. This study involves characterization of samples from the area and suggests the suitable processing method to recover gold and iron with mining impacts to the environment. In this research, tailing and palong samples are studied and the following methodology is applied: laboratory sampling, mineral characterization and alluvial gold processing and then found the recovery of gold after the results of analysis and processing. Result shows that the tailing sample composed of 0.020 % of AU20 in flaky shape presented in fraction size <2.36 mm. No gold was found in palong sample (taken from middle of palong) due to its good design. Based on XRD result, tailing sample consists of hematite (FC203) 44.20 %, quartz low (Si02) 32.90 %, pyrrhotite high (FeO.lJ8SS) 13 %, pyrite (FeS2) 9 % and magnetite (Alo.IFe2.46Mgo.4204Tio.03) 0.90 %, whereas palong sample consists of quartz low (Si02) 74.60 %, hematite (Fe203) 21. 70 %, magnesium aluminum sulfide (AhMgS4) 3.20 % and pyrite (FeS2) 0.60 %.
Fabrication and characterization of copper-stabilized ultrathin silicon dies using ultrashort-pulse laser dicing
(2021-11-01)
Marks. Michael Raj
Ultrathin dies require a copper (Cu) stabilization layer, which is essentially a backside Cu layer, to prevent warpage and cracks during subsequent packaging assembly process. The dicing of silicon (Si) wafers with a backside Cu layer by mechanical blade dicing and plasma dicing pose various quality and cost challenges. Laser dicing is a promising method for dicing thin and ultrathin Si wafers. The feasibility of dicing ultrathin Si wafers with backside Cu layer using nanosecond pulse laser has been reported in the literature. However, there is no reported work on the application of ultrashort pulse lasers in the picosecond and femtosecond range for dicing ultrathin Si wafers with backside Cu layer. Theoretically, ultrashort pulse lasers could reduce the thermal effects during laser dicing. The main aim of this research is to systematically investigate the dicing of 20 µm ultrathin Si wafers with 10 to 30 µm backside Cu with picosecond and femtosecond pulse lasers. In order to study the effect of the ultrashort pulse lasers on the die sidewall fracture strength accurately, a novel procedure for three-point bend (3PB) test was developed. Fractography analysis was performed to determine and study the fracture initiation sites of 3PB test samples. During laser dicing of ultrathin Si wafers with backside Cu, a Si oxide layer is formed between the crystalline Si substrate and a layer of polycrystalline Cu silicide. It was observed that the Si oxide layer detaches from the crystalline Si at the backside region of the sidewall. The detachment of the Si oxide from the crystalline Si is through a microvoiding mechanism which has a significant effect on the fracture strength of the die sidewall. The die sidewall defect morphologies, microstructures, and elemental compositions after picosecond and femtosecond pulse laser dicing have been characterized in detail by transmission electron microscopy equipped with energy dispersive spectroscopy and nano beam diffraction. Picosecond laser dicing on ultrathin Si wafers with Cu backside layer up to 30 µm thickness seems to be the best laser dicing approach in terms of die sidewall quality and fracture strength. In general, without backside Cu layer, the sidewall backside strength is approximately 9 to 125% higher than the frontside strength, and with 10 to 30 µm Cu backside Cu layer, the average sidewall backside strength is approximately 66 to 71% higher than the average frontside strength.
Fabrication and characterization of natural surfactant assisted carbon nanotubes-based flexible printed strain sensor
(2022-03-01)
Kamarudin, Siti Fatimah
Printed strain sensors have been explored in real-world applications for more than two decades due to low cost and simple fabrication processes. The utilization of natural materials combined with a ‘green’ approach in developing the sensor devices are gaining popularity among researchers to reduce the environmental impact and enable advanced health monitoring applications. The main aim of this study is to develop a carbon nanotube-based strain sensor composed mainly of natural materials. In this study, water-based multi-walled carbon nanotubes (MWCNTs) conductive inks were synthesized through a surfactant-functionalization method. The dispersion efficiency of various surfactants such as gum Arabic (GA), alkali lignin (AL), polyvinylpyrrolidone (PVP) and pluronic F-127 (PL) in promoting long-term stability to the MWCNTs inks were investigated. Next, a flexible starch/polyvinyl alcohol (SP) blend film with the addition of glucose and urea as binary plasticizer was developed by solution casting method. The SP films were then used as a substrate for the inkjet printing of MWCNTs ink to fabricate flexible printed strains sensors. The dispersion analysis showed that the highest MWCNTs stability of 66.1% and 59.5% was achieved with the help of 5 and 8 mg mL-1 of GA and PVP, respectively. SP blend film with glucose: urea weight ratio of 75:25 exhibited the highest flexibility and stretchability with elongation at break of ~198%. MWCNTs inks printed on the SP film produced higher sheet resistance but with better printing quality compared to those on PVA film (control). A strain sensor made by GA/MWCNTs@SP showed a good stretchability up to 55% and high sensitivity at strain, ɛ<10%. Small hysteresis was obtained for ɛ<20% and excellent stability in the electrical response was observed when the sensor was subjected to a cyclic stretching. In addition, the sensor also exhibited a good and reproducible signals in response to the continuous bending and relaxing of finger, hand and elbow. Overall, although GA/MWCNTs@SP sensor showed lower electro mechanical performance compared with the previous works, with a proper modification in the sensor design, the sensor could become a great alternative in replacing conventional sensors.

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