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.
Asymmetrical porous polycaprolactone/ silver nanoparticle-hydroxyapatite composite membrane for periodontal guided bone regeneration
(2023-08-01)
Bee Soo Ling
Guided bone regeneration (GBR) procedure using barrier membrane is the most common method used to treat periodontal defects in clinical practice. Nevertheless, the currently available GBR membranes are still suffer from few drawbacks, including their lack of crucial properties such as suitable surface morphology, antibacterial and bioactivity to aid periodontal regeneration. Therefore, this research aimed to fabricate a novel asymmetrical porous polycaprolactone/silver nanoparticle-hydroxyapatite barrier membrane that possess bioactivity and antibacterial properties to overcome the shortcoming of conventional GBR membrane. Briefly, hydroxyapatite (HAp) with optimum physio-chemical properties was successfully extracted from fish bone waste via calcination approach at 650 oC. Thereafter, pandan leaf extract was used to induce the in-situ synthesis of silver nanoparticle-hydroxyapatite (AgNPs-HAp) composite through a green bioreduction approach in silver nitrate solution. The influence of filler loading content and filler types on the surface morphological, mechanical, surface hydrophilicity, swelling, degradation, in vitro bioactivity, antibacterial, biocompatibility and cell barrier properties of the resulting membranes were evaluated. Scanning electron microscopy (SEM) showed that all composite membranes displayed an asymmetric “macro-micro porous” surface morphology regardless of their filler type and content added. Compared to pure PCL membrane, incorporation of HAp or AgNPs-HAp also significantly enhances the bioactivity of PCL membrane, in which the AgNPs-HAp filler have better impact for enhancing the bioactivity of membrane over HAp filler. After 56 days of degradation period, the tensile strength and Young’s modulus of all prepared composite membranes were maintained at range of 1.36−1.93 MPa and 10.4−14.9 MPa. Meanwhile, all PCL/AgNPs-HAp composite membranes showed antibacterial activity against E. coli, while only PCL/AgNPs-HAp composite membranes with AgNPs-HAp content > 5 pphr showed antibacterial property against S. aureus. The addition of AgNPs-HAp filler also improved the attachment of Saos-2 cells on the surface of membrane. Furthermore, all PCL/AgNPs-HAp composite membranes showed the ability to inhibit the penetration of fibroblast cells in a period of at least 28 days. Due to the suitable mechanical, biodegradability, bioactivity, antibacterial properties, biocompatibility and cell barrier property along with the unprecedented “macro-micro porous” membrane’s morphological structure that meet the requirement for GBR, the developed asymmetrical porous PCL/AgNPs-HAp composite membrane has the potential to be applied for periodontal GBR application.
Bio-based tableware incorporating rice husk into modified epoxidized palm oil matrix
(2025-09-01)
Sunil, Anandrao Katkar
The growing demand for sustainable materials has driven research into developing bio-based alternatives to conventional plastics, and in this context, bio-based tableware incorporating PEG-modified and unmodified rice husk into modified epoxidized oil offers a promising solution. The widespread use of synthetic-based tableware such as plastic plates and bowls poses significant environmental and health challenges due to their non biodegradability and potential leaching of harmful chemicals. Addressing this issue, the present study develops bio-based tableware as a sustainable alternative, emphasizing improved strength and moisture resistance through interface engineering. Rice husk (RH), an abundant agricultural by-product, was used as filler, while epoxidized palm oil (EPO) served as the bio-based polymeric matrix. Citric acid was incorporated as a crosslinker to enhance structural stability, and polyethylene glycol (PEG) was introduced to improve filler wetting, dispersion, and adhesion. The tableware was fabricated using sigma mixing and hot press molding, followed by post-drying for moisture stabilization. Comprehensive characterization was conducted, including tensile, flexural, and impact tests to evaluate load-bearing capacity, water absorption and dry-back analysis for wash durability, FTIR spectroscopy to confirm hydroxyl suppression and ester/ether linkage formation, and FESEM imaging to assess interfacial morphology. Results revealed that PEG-modified tableware exhibited superior mechanical strength, improved stiffness, and lower reversible moisture uptake compared to unmodified samples. FTIR confirmed effective crosslinking and bonding, while FESEM showed a denser, less hydrophilic interphase. The best balance of mechanical and moisture
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.
Biodegradable poly (hydroxybutyrate-co-hydroxyhexanoate)/poly (butylene succinate) blends and their kenaf fibre composites
(2024-09-01)
Mohd Zharif, Ahmad Thirmizir
The increasing demand for sustainable materials and concerns over environmental issues related to synthetic polymers have increased interest in biodegradable polymers for various applications. However, enhancing the mechanical properties of biodegradable polymer blends, in this case poly(hydroxybutyrate-co hydroxyhexanoate)/poly(butylene succinate) (PHBHH/PBS) blends, remains a significant challenge, especially when lignocellulosic fibres like water-retted kenaf bast fibre (WKF) are used as reinforcement. This study aims to produce a PHBHH/PBS blend with optimal strength and toughness as a matrix for biodegradable composites derived from WKF. The PHBHH/PBS blends and their WKF composites were produced via melt blending in the presence of maleated compatibilisers, dicumyl peroxide (DCP), or both. Maleated PHBHH (PHBHHgMA) and PBS (PBSgMA) compatibilisers were synthesised via melt grafting in the presence of DCP as the free radical initiator. The addition of the compatibilisers improved the tensile strengths of the 80PHBHH/20PBS and 50PHBHH/50PBS blends, with the highest increments of 14 % and 20 % achieved at maleic anhydride (MA) concentrations of 3 and 5 phr for PHBHHgMA (3PHBHHgMA) and PBSgMA (5PBSgMA), respectively. However, improvements in toughness (Kc and Gc) were not improved. To enhance the toughness, DCP (at 0.75 wt. %) was introduced, resulting in the partially crosslinked 5PBSgMA and 3PHBHHgMA compatibilised 80PHBHH/20PBS and 50PHBHH/50PBS blends exhibiting superior toughness, with increases in Kc by 9 – 23 % and in Gc by 41 – 68 %, as well as higher tensile strength (15 – 23 %) compared to their uncrosslinked counterparts. In fact, the partially crosslinked compatibilised 50PHBHH/50PBS blends demonstrated superior tensile strength and toughness (Kc and Gc) compared to their 80PHBHH/20PBS blend counterparts due to the higher proportion of flexible and tough PBS fraction. Additionally, WKF with an optimum loading of 30 wt. % was added into the neat, compatibilised, and partially crosslinked compatibilised 50PHBHH/50PBS blends to further improve their mechanical properties. The most remarkable improvements in tensile strength (⁓ 60 %), and toughness, Kc (⁓ 22 %) and Gc (⁓ 52 %) were attained by the partially crosslinked 5PBSgMA compatibilised 35PHBHH/35PBS/30WKF blend composite due to the synergistic effect of maleated PBS compatibilisation and DCP-initiated free radical crosslinking reactions. The 30-day water immersion test demonstrated that the addition of hydrophilic WKF significantly increased the water absorption (⁓ 10-fold) and exacerbated the deterioration of the 50PHBHH/50PBS blends. Similarly, the 6-month soil burial test also revealed that the presence of WKF significantly increased the biodegradation rate of the blends. However, the introduction of maleated compatibilisers and combinations of maleated compatibilisers and DCP significantly mitigated these effects in the 35PHBHH/35PBS/30WKF composites. Overall, the combined use of maleated compatibilisers, particularly 5PBSgMA and DCP crosslinking agent not only significantly improves the mechanical properties of the composites but is also effective in enhancing their durability against water deterioration and soil biodegradation, particularly in the early stages (2 – 4 months) of burial, compared to the use of maleated compatibiliser alone.
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.
Characteristics of cross-linked polyethylene and polyethylene blends nanocomposites for high voltage electrical insulation
(2024-11-01)
Muhammad Safwan, Hamzah
In this study, nanofillers composed of aluminium oxide (Al2O3), zinc dioxide (ZnO) and organoclay were separately embedded in cross-linked polyethylene (XLPE) and linear low density polyethylene (LLDPE) / styrene/ethylene-butylene/styrene copolymer grafted with Maleic Anhydride (SEBS-g-MA) polymer blend. Using an internal mixer and compression molding, several filler loadings (0.5, 1.0, 1.5, and 2.0 wt. %) of XLPE nanocomposites were prepared. Findings show that the addition of nanofillers enhances the tensile strength, flammability, hydrophobicity and flowability of the XLPE nanocomposites. Organoclay filled XLPE nanocomposite is selected as comparison with LLDPE/SEBS-g-MA nanocomposites. The effect of different polymer matrix and filler loadings (0.5, 1.0, 1.5, and 2.0 wt. %) on tensile properties, flammability, hydrophobicity and flowability properties were determined in the second part of the study. LLDPE/SEBS-g-MA nanocomposites improve the tensile properties up to 20%, flame resistance up to 8% and hydrophobicity up to 40% compared to organoclay filled XLPE nanocomposites. In the third part, studies on dielectric properties and dielectric breakdown strength properties using different filler loading on XPLE nanocomposites and LLDPE/SEBS-g-MA nanocomposites were conducted. It is found that organoclay filled nanocomposites system exhibits the highest improvement of dielectric breakdown up to 9% compared to its respective unfilled system. In the fourth part, studies on electrical treeing on Al2O3 and organoclay filled XLPE nanocomposites found that 0.5 wt. % filled organoclay nanocomposite systems exhibits the highest improvement of 7% in tree inception voltage (TIV). In conclusion, 0.5 wt. % organoclay filled LLDPE/SEBS-g-MA nanocomposites is the best formulation to be used as high voltage electrical insulator.
Characterization and properties of electrospun polycaprolactone polyethylene oxide/bioglass scaffold for guided bone regeneration
(2024-08-01)
Mohamed Ali, Ehmoda Ali
Guided Tissue/Bone Regeneration (GTR/GBR) is an established dental technique that promotes damaged bone and tissue regrowth. This method utilizes guide materials that are biodegradable over time, allowing for the integration of new tissue. GTR/GBR scaffolds must satisfy several criteria for optimal efficacy, including biocompatibility, appropriate mechanical properties such as rigidity and elasticity, porosity, and clinical practicality. In pursuit of these requirements, this study explores the synthesis of scaffolds by blending polycaprolactone (PCL) with polyethylene oxide (PEO) and bioactive glass (BG) through electrospinning. Initially, PCL was dissolved in a solvent mixture comprising acetic and formic acids at a 3:7 volume ratio. The research then focused on evaluating the influence of electrospinning parameters and PCL concentrations on fiber morphology. It was observed that scaffolds with a 20% PCL concentration demonstrated enhanced properties relative to other concentrations. Furthermore, the addition of PEO and BG was explored. The introduction of PEO at various blend ratios markedly affected the scaffold's mechanical properties, with the PCL/PEO (90/10) blend showing improved mechanical strength. The incorporation of BG was shown to enhance surface roughness and hydrophilicity. Moreover, in vitro assessments indicated that scaffolds containing BG facilitated hydroxyapatite formation. However, increasing BG content slightly reduced mechanical properties compared to the PCL/PEO (90/10) scaffolds. The optimal composition was PCL/PEO -BG7%, which exhibited a balanced performance in the GBR requirements. The in vitro cell study also showed that the scaffolds with BG enhanced the proliferation of SaOS-2 cells. The study suggests that PCL/PEO/BG electrospun scaffolds have potential applications in GBR.
Characterization and properties of sepiolite/organo-modified sepiolites filled natural rubber-styrene butadiene rubber and natural rubber-epoxidised natural rubber blends
(2023-12-01)
Diana Adnanda Nasution
This research work investigated the effect of sepiolite as nanofillers on curing, mechanical, thermal, and morphological properties of natural rubber-styrene butadiene rubber (NR/SBR) and natural rubber-epoxidized natural rubber (NR/ENR-25) blends. The effect of sepiolite loading on properties of sepiolitefilled NR/SBR and NR/ENR-25 was analysed and compared. Subsequently, a comparative investigation on water uptake on properties of NR/SBR and NR/ENR- 25 blends containing sepiolite was carried out to assess the efficiency of sepiolite as reinforcing filler in the blend. The effect of surface modification on sepiolite particles in a concentrated solution of cetyltrimethylammonium bromide (CTAB) to produce organo-modified sepiolite was carried out to investigate further enhancement of properties for NR/SBR blends. It was observed that sepiolite-filled NR-SBR blends at optimal loadings (3phr) has optimal mechanical properties even under prolonged water exposure. The nanosize sepiolites, containing hydrous silicates and metal groups, act as accelerators for vulcanization. While sepiolite serves as a reinforcement at low loadings, agglomeration effects become dominant at higher loadings, in which reducing filler-rubber interaction. Moreover, in thermal analysis, it was found that, sepiolite accelerates char formation, acting as a flame retardant during combustion. In NR/ENR25 blends, sepiolite functions as an accelerator for vulcanization, exhibiting similar as NR/SBR blends. It was also found that sepiolite reinforced NR-ENR25 blends and acted as thermal stabilizer with higher water uptake ability compared to NR/SBR blends. The findings emphasize the potential applications of sepiolites in optimizing rubber blend properties, offering insights into their roles as reinforcement, thermal stabilizer, and flame retardant in various industrial applications. Keywords: sepiolite fillers, CTAB-sepiolites, natural rubber blends, epoxidized natural rubber, styrene-butadiene rubber, water uptake, blending properties
Characterization of a superhydrophobic epoxidized natural rubber coating modified with stearic acid and calcium carbonate nanoparticles
(2024-09-01)
Farrah Amiera, Mohd Khairuddin
Waterproofing coatings have consistently garnered the attention of the global market to protect concrete surfaces against corrosion. This study compares the potential of epoxidized natural rubber 25 (ENR 25) and epoxidized natural rubber 50 (ENR 50) latexes with modified nanoparticles of calcium carbonate and stearic acid (CaCO3-SA) to develop a superhydrophobic (SH) latex coating. The optimal hydrophobically CaCO3-SA exhibited a maximum water contact angle (WCA) of 143.68 ± 13.6 ° by incorporating 7 wt.% of CaCO3 nanoparticles and 4 wt. % of SA through Layer-by-Layer (LbL) method. The non-blending ENR 25(CaCO3-SA)* latex coating revealed an excellent WCA value of 172.54 ° and the lowest roll-off angle (RA) of 6.9 ° at a curing temperature of 80 °C via the LbL immersion technique. With optimum curing in the non-blending of LbL, the ENR 25(CaCO3-SA)* surface coated created a hierarchical rough micro-nanostructure, compared to Room Temperature (RT). Greater water repellency of surface coated was determined at lower latex total solid content (TSC), 10 %. It also attained significant SH and superoleophilic properties through oil/water separation efficiency. The lower epoxy content found in ENR 25(CaCO3-SA)* compared to the non-blending modification of ENR 50 which was determined from the FTIR spectrum. The optimum modified nanoparticles and ENR latex were mixed and carried out with different coating techniques (immersion and spray). The SH properties were impeccably improved with a WCA of 156.48 ± 2.90 ° and water easily rolled off on the air-assisted airless spray concrete-coated cured at RT in the pre-vulcanization blending system. Hence, the facile technique of SH latex coating was achieved.
Characterization of nanocomposite sn/ag coating for bus duct conductor
(2024-03-01)
Kong, Chee Xian
With the advent of contemporary buildings and large-scale workshops that require a lot of electricity, the busduct system has been chosen as the power distribution unit. Tin-plated busbars have relatively low bulk resistivity, causing higher contact resistance as high current passes by. The power loss is released as heat, increasing the joint temperature and eventually reducing current-carrying capacity. Incorporation of silver nanoparticles (AgNPs) in the Sn matrix could potentially improve the contact resistance of busduct conductors. The coating morphology, phase structure, surface roughness, and contact resistance of the Sn/AgNPs composite with magnetic stirring electroplating (MSE) and ultrasonic-assisted electroplating (USE) were compared. Also, the size and concentration of AgNPs in Sn/AgNPs via USE were studied as well. Finally, plating parameters were optimised for lab scale, and prototype samples were fabricated. The USE facilitated the co-deposition of AgNPs and formed a smooth and compact silvery-grey coating compared to that of MSE. Sn (U) has a thicker coating with less plating time than Sn (M). The average coating thickness was increased until agglomeration of white clusters was observed: Sn/10Ag3 (U) for 10 nm AgNPs addition and Sn/100Ag2 (U) for 100 nm AgNPs addition, respectively. Increasing the concentration of AgNPs, the wt% of Ag increased up to 1.77 % and 1.59 % for both types of AgNPs. The crystallise size was refined to 30.48 nm for Sn/10Ag2 (U) and 27.38 nm for Sn/100Ag2 (U). The refinement could be a combined effect of USE and AgNPs addition. Sn/10Ag2 (U) has the lowest Ra value of 1.15 nm and lowest contact resistance of 6 μΩ compared to Sn coating with 8.67 μΩ, i.e., 31 % reduction.
Characterization of polypropylene-coated chitosan/silver nanoparticles (agnp) for antimicrobial application
(2023-09-01)
Nazihah Binti Nasri
In fighting against microbial contamination, the fabrication of chitosan/AgNP coating on polypropylene (PP) surface could be an advantage because of the intrinsic antimicrobial and biocompatibility behavior of AgNP and chitosan. This research project aims to fabricate an antimicrobial chitosan/AgNP coating onto plasma-treated PP film via dip coating. The first stage of this study involved of green synthesis of AgNP from turmeric extract via an ultrasonic-assisted method, which AgNO3 and turmeric extract concentration were varied from 1 mM to 10 mM and 5 mL to 25 mL respectively. After 30 minutes, an optimized concentration of AgNO3 (7mM) and turmeric extract (25 mL) were obtained to produce the smallest size of AgNP (9.62 ± 6.72 nm) with biggest inhibition zone on E. coli and S. aureus growth. The presence of organic molecules from turmeric extract on AgNP surface was confirmed via High Resolution-Transmission Electron Microscopy (HR-TEM) and Fourier-Transform Infrared Spectroscopy (FTIR) analysis. Meanwhile, the best plasma current supply (8 mA and 10 mA) and plasma treatment time (15s, 30s, 45s, 60s) during oxygen plasma surface treatment was evaluated on PP surface. The continuous etching action and new functional groups formation had produced PP surface with high average surface roughness (12.46 nm) and low water contact angle (17.95o ± 2.36) after 45 seconds of treatment under 10 mA of current. Subsequently, the immobilization of chitosan/AgNP coating on plasma treated PP was done via dip coating method. In this stage, different chitosan molecular weight (high, medium, and low molecular weights) and chitosan concentration (0.5%, 1.0%, 1.5%, and 2.0% (w/v)) were immobilized onto plasma-treated PP film and evaluated based on FTIR, water contact angle, and Atomic Force Microscopy (AFM) analysis. It was found that 1.5% (w/v) of high molecular weight chitosan produced surface properties with 54% reduction of water contact angle and 29% increment of average surface roughness that is suitable properties for antimicrobial purpose with good coating stability. In the last stage involves of the study on the effect of dipping cycle on antimicrobial activity and adhesion strength of chitosan/AgNP coating. An increasing of dipping cycle did increase the coating thickness and AgNP content but no noticeable differences were observed on antimicrobial activity behavior
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.
Correlating rock mass quality with tbm performance in pahang-selangor raw water transfer tunnel
(2023-08-01)
Sylvanus Sebbeh-Newton
The rock mass classification system and the numerical modelling are the two main design tools widely used in tunnel stability investigations. Subjective uncertainties is a major challenge with the use of rock classification systems, thus the need for data-driven classifiers. Also, ignoring uncertainties in the post-peak rock mass strength parameters in numerical modelling may lead to underestimation of probability of failure. The purpose of this study is to account for the uncertainties in these two tunnel design tools. To address the subjectivity in the classification system specifically the JH system, four machine learning models: Support Vector Machine (SVM), K-nearest neighborhood (KNN), Random forest (RF), and extremely randomized trees (ERT) were used to develop data-driven rock mass classifiers for the Pahang-Selangor Raw Water Tunnel (PSRWT) in Malaysia. The entire database used for this research consists of 180 rock mass data and 79,813 TBM operating data points. This dataset represents 11.6 km of the tunnel from chainage 6.85 km to chainage 18.59 km. Nine (9) Tunnel Boring Machine (TBM) operating parameters; rate of penetration, cutterhead torque, cutterhead thrust force, cutterhead revolution per minute, stroke speed, boring pressure, pitching, and motor amps were used as input variables. The results indicate that ERT has the potential to correctly identify rock masses and also has a good generalization ability . To also address the uncertainties in the numerical techniques, the point estimate method (PEM) incorporated in RS2 was used to model two case scenarios. In case 1, uncertainties in both peak and post-peak rock mass strength parameters were considered whereas in case 2, only uncertainties in the peak parameters were considered. A comparison of the two cases revealed that the probability of failure was significantly underestimated when the uncertainties in the post-peak rock mass strength parameters were ignored.
Crosslinked polyacrylamide/ polyethylenimine containing nano-hydroxyapatite/cellulose hybridization for the adsorption of lead ions in aqueous solution
(2024-07-01)
Ng, Chi Loon
The increasing pollution of wastewater with heavy metals has become a significant human and environmental concern. The need for efficient adsorbents to remove these pollutants is critical. This study aims to develop an adsorbent system with the combination of a crosslink and hybrid fillers system that can effectively adsorb heavy metals from water. A polymer nanocomposite adsorbent system made from 70 wt% of polyacrylamide (PAM), 30 wt% of polyethylenimine (PEI) containing 3 phr of nanohydroxyapatite (nHA), and 15 phr of cellulose (Cel) was successfully crosslinked with N,N methylenebisacrylamide (MBA) and prepared via solution casting. The PAM/PEI/MBA and the nanocomposites were characterized via several techniques such as water absorption swelling test, thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM). The effects of the addition of different amounts of crosslinker (1 phr and 10 phr) on the adsorption capacities were explored. The adsorption capacity of PAM/PEI/Cel/nHA/MBA 10% was shown to be higher than PAM/PEI/Cel/nHA/MBA 1%. The study examined the impact of pH, initial heavy metal concentration, and contact time on adsorption. The results revealed that the optimal pH for adsorption is 5. Additionally, it was found that the adsorption capacity increases with the initial concentration of heavy metals. Furthermore, a longer contact time also enhances the adsorption capacity. The highest adsorption capacity attained was 404.5 mg/g at pH = 5, an initial concentration of 100 ppm, and 2 hours of contact time using 10 mg of absorbent. The isotherm of the crosslinked nanocomposite PAM/PEI/Cel/nHA/MBA 10% was examined with Langmuir and Freundlich isotherms while the kinetics were examined with pseudo-first-order kinetic and pseudo-second order kinetic. The result showed that it obeys the Freundlich isotherm and pseudo-second order kinetics, with R² values of 0.9991 and 0.9976, respectively, showing a multilayer chemisorption adsorption process.

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