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.
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 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 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.
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 different type of coagulants and serum ph on the properties of natural rubber compounds and vulcanizates
(2023-07-01)
Ng Jing Wei
Natural rubber (NR) is the main component used in tyre industry that is extracted naturally from Hevea Brasiliensis in latex form and further transformed into dried rubbersheet. In the first experiment, the latex was coagulated with different types of coagulant, which are formic acid, sulfuric acid, CaCl2, methanol and spontaneously without addition of coagulant. After processing, the raw rubbers produced from the respective coagulants were subjected to different testing from the perspective of coagulation process, raw rubber, masterbatch, final mix compound and finally vulcanizate in tyre tread formulation. Being the most efficient coagulant, sulfuric acid displayed poorer properties in raw rubber with oxidized rubber sheets and higher amount of short rubber chains as indicated in AE content and Mw. In contrast, natural coagulation was demonstrated to be least efficient, but the raw rubber was tested to have highest molecular weight and macrogel content. The Mw of raw rubber and macrogel content were shown to be well correlated to the VR and P0. Besides, the selection of coagulant type was found to have impact also on the N and metal ions content of raw rubber. However, the impact of coagulant type on the BdR of masterbatch, Payne effect and VR of final mix compound was indirect depending on the Mw and VR of raw rubber. Accelerating effect of natural proteins and retarding effect of sulfuric acid were also observed in curing properties. The physical mechanical properties of vulcanizate were mainly influenced by the crosslink density of vulcanizate. The type of coagulants used displayed no significant influence on the wet grip and rolling resistance properties of vulcanizate. In the second experiment, the latex was coagulated with formic acid and sulfuric acid respectively, in serum pH 4 and pH 2. The most notable impact of serum pH was the efficiency of coagulation process, VR and P0 of raw rubber. It was shown that the impact of acid type on the raw rubber properties was less important if the serum pH was controlled on same level except PRI. However, the impact of serum pH on other properties of raw rubber were not significantly observed. After addition of compounding ingredients, the properties of masterbatch, final mix compound and vulcanizate displayed no significant differences between different serum pH suggesting the compounding ingredients play more important role to decide the properties of vulcanizate.
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.

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