The main purpose of this study was to analyzed and examined the cocoa butter samples from Sabah. This work presence the crystal phases present in cocoa butter sample thus proved the existence of polymorphs obtained from differential scanning calorimeter (DSC) analysis and confirmed by X-ray diffraction (XRD). The cocoa butter samples were extracted using a conventional method by Soxhlet Extraction method. Crystals were formed under controlled static and tempered conditions. Cocoa butter polymorphism demonstrates that it is the actual crystallization temperature, not the cooling rate that determines the polymorph that crystallizes.
Currently, research in composite materials is being directed at using natural fibers instead of synthetics fibers. The use of natural fibers, derived from annually renewable resources, as reinforcing fibers in matrix provides positives environmental benefits with respect to ultimate disposability and raw material utilization. Natural fiber offers an alternative to the technical reinforcing fibers because of their low density, good mechanical performance, ultimate availability and disposability. Modifying the fiber surface by using chemical treatment can enhance bond strength between fiber and matrix. Chemical treatment also an effective way to clean the fiber surface, chemically modify the surface and increase the surface roughness. Surface analyses on fiber for before and after treatment were investigated using scanning electron microscopy (SEM).
One-dimensional nanostructure materials are very attractive because of their electronic and optical properties depending on their size. It is well known that properties of material can be tuned by reducing size to nanoscale because at the small sizes, that they behave differently with its bulk materials and the band gap will control by the size. The tunability of the band gap makes nanostructured materials useful for many applications. As one of the wide band gaps semiconductor compounds, zinc selenide (ZnSe) nanostructures (nanoparticles, nanowires, nanorods) have received much attention for the application in optoelectronic devices, such as blue laser diode, light emitting diodes, solar cells and IR optical windows. In this study, ZnSe nanostructures have been synthesized by reduction process of zinc selenate using hydrazine hydrate (N2H4.2H2O). The reductive agent of hydrazine hydrate was added to the starting materials of zinc selenate were heat treated at 500 o C for 1 hour under argon flow to form onedimensional nanostructures. The SEM and TEM images show the formation of nanocompositelike structures, which some small nanobars and nanopellets stick to the rod. The x-ray diffraction and elemental composition analysis confirm the formation of mixture zinc oxide and zinc selenide phases.
Unaffected, affected and heavily affected teeth enamel were studied by using FT-Raman spectroscopy. The 14 permanent teeth’s enamel surface were measured randomly, resulting in total n=43 FT-Raman spectra. The results obtained from FT-Raman spectra of heavily affected, affected and unaffected tooth’s enamel surfaces did not show any significant difference. In this study, Kruskal-Wallis and Wilcoxon rank sum tests were used to compare the intensity between the categories of enamel as well as the surfaces of teeth samples.
In this paper, densification of in-situ copper-niobium carbide composite using cold pressing technique was addressed. Mixtures of Cu-20vol%NbC powder were prepared by two methods.
In first method, a mixture of Cu-15.79wt%Nb-2.04wt%C powder was milled at 400 rpm for 35 hours in a planetary mill. In second method, Cu and commercial NbC powder was mixed at 100 rpm for 2 hours in a jar mill. Then, both powders were pressed at different pressure (i.e. 350 MPa, 450 MPa, 550 MPa and 650 MPa) and sintered at 900 o C for 1 hour. Sample of in-situ and ex-situ Cu-20vol%NbC composite were characterized for density, hardness, phase formation by x-ray diffraction analysis and microstructure by scanning electron microscope. Xray diffraction analysis showed that NbC phase was formed in the in-situ processed sample. Hardness of in-situ processed copper composite was higher than that of the ex-situ processed copper composite due to good interface between coper matrix and niobium carbide reinforcement particle as well as distribution of finer niobium carbide particles in copper matrix. Sintered density of in-situ composite is lower than density of ex-situ composite beacuse of work hardening of the Cu-Nb-C mixture powder during powder to ball collision. Density and hardness of the in-situ and ex-situ Cu-20vol%NbC composites increase with the increase in compaction pressure as porosity is eliminated at higher compaction pressure.
Phenolic resin-silica nanocomposites samples in pellet shape have been successfully prepared by intercalation of polymer solution through the hot pressing method. The phenolic resin is modified with organic elastomers of silica nanoparticles, which is about 20 nanometer in diameter. The change of density and porosity was studied based on the addition of silica content in the phenolic resin composites. The densities of composites increased with the addition of the silica content from 10 wt.% to 40 wt.%. On the other hand, the porosity percentage was decreased with increasing of silica contents. The mechanical properties (Young’s modulus, energy to break and time to failure) of the nanocomposites samples were identified using the Universal Testing Material Machine (UTM). The results of Young’s modulus, energy to break and time to failure of the phenolic resin composites were found to be slightly increased with silica content from 10 wt.% to 30 wt.%. The X-Ray Microtomogaphy (XRM) topographies have shown that the porosity exists on fracture structure for each nanocomposite. The nanocomposites surface structure has been analyzed using Scanning Electron Microscope (SEM). The observation shows that the fracture surface of the pure phenolic resin is relatively smooth and glassy, which is typical for a brittle material, but the phenolic resin- silica composites fracture surface is not smooth at all. The observations indicate the pure phenolic resin is brittle than phenolic resin-silica nanocomposites. Consequently, the physical properties of the phenolic resin-silica nanocomposites were improved with the addition of 10 wt.% to 30 wt.% silica contents, as compared to that of the pure phenolic resin.
Chitosan was chemically modified with bulky structure, cis-5-norbornene-2, 3-dicarboxylic anhydride and the characteristic of this modified chitosan was studied. The resulting material was analyzed by FTIR, TGA, DSC, XRD and SEM to study the effect of N-acylation to the polysaccharide structure. FTIR results show that the anhydride monomer was successfully bound to amine group of chitosan. Thermal analysis of the modified structure provides the chitosan fibers with thermal stability while XRD and SEM show the lost of crystallinity of modified chitosan. XRD of modified chitosan shows broader peak pattern and a considerable increase in a dimension while SEM of chitosan presented the single particle morphology while norbornene-chitosan shows aggromolarate behaviour due to the hydrophobic nature of norbornene pendant group which induced aggromolaration of the particles in modified structure.
Indialite or α-cordierite was synthesized by glass crystallization method using mainly talc and kaolin and with small amount of MgO, Al2O3, SiO2 to compensate the chemical formulation of non-stoihiometric compositions of cordierite. (3MgO.1.5Al2O3.5SiO2). B2O3, P2O5 and CaO was also added to decrease the melting and sintering temperature of cordierite. The glasses were pelletized and sintered from 850 o C up to 1050 o C. Phase compositions of both heat treated glass was quantified by X-ray powder diffraction data by the Rietveld method using TOPAS Ver 3 software. Result shows that about 60wt% of α cordierite has successfully crystallized at 850 o C. Beside secondary phases (forsterite) which come from initial raw materials, phases from grinding media were also presents in the sample. The contamination was considered high since it has reacted with existence phases to form a new phase at higher temperature. Without any contamination from grinding it was expected to obtain more than 90wt% α cordierite using the same composition.
Silicon nanowires were synthesized on Si substrates (111) via thermal evaporation using AuPd thin layer catalyst. Pre cleaned of Si wafer was used as a substrate to assemble the nanostructure products. In this work, the effect of growth temperature that ranging from 800 to 1000°C on the formation of silicon nanowires studied extensively. X-ray diffraction and field emission scanning electron microscope were employed to characterize the structures and morphology of nanowires. Vertical aligned silicon nanowires have been successfully grown on Si substrates at 900 and 1000°C. At 1100°C, the high aspect ratio of silicon nanowires can be produced but the formation density is low. The presence of AuPd catalyst on the tip of nanowires, it is expected that VLS is the most suitable to explain the growth mechanism of obtained SiNWs. The crystalline structure of SiNWs was proved by XRD data.
The term microfibril angle, MFA in wood science refers to the angle between the direction of the helical windings of cellulose microfibrils in the secondary cell wall, S2 layer of fibres and tracheids and the long axis of the cell. In this study, the mean MFA of the cell walls were determined for thin samples of thickness 200.0 µm from pith and outwards, for eight ages of Acacia mangium wood. The determination of MFA was based on a diffraction pattern arising from cellulose crystal planes of the type 002 generated by x-ray diffraction and recorded using an electronic detector. The results show an inversely relationship between MFA and age of tree in Acacia mangium wood. MFA decreased from 26.13° at age 3 year-old to 0.20° at tree of age 15 year-old for the pith region. The most significant drop occurred from 16.14° at age 7 yearold to 11.30° at age 9 year-old. An inversely relationship between MFA and storage modulus E’ was evidence in Acacia mangium at age 10-year-old. The results showed that about 76.22% variation of loss modulus E” was attributed to the MFA, while about 66.4% of the variation of glass transition Tg was explained by MFA under the same experimental conditions.
This research was conducted to study the effect of reinforcement particles on iron-cobalt (FeCo) composites. The composition of silicon carbide (SiC) was varied from 0 to 20 wt%. The composite was fabricated via powder metallurgy (PM) method, which consists of mixing, compaction and sintering processes. The powder was mixed for 2 hours to obtain uniformity between SiC and Fe-Co matrix and compacted to a cylindrical shape at 250 MPa. Samples were sintered for 2 hours at 900 o C with 10 o C/minute heating rate in argon atmosphere. The influences of reinforcement particle on the sintered samples were characterized in terms of microstructure and hardness testing. The Fe-Co/20wt%SiC composites show highest hardness value.
Herein, we report on the optimum condition for TiO2, titania nanotubes formation and the effect of annealing on the formation of anatase and rutile titania. Anodic oxidation was carried out in two electrodes bath consisting of 5wt% NH4F ions. The anode was a 0.1mm thick Ti foil and the cathode was Pt electrode. Anodisation was conducted at 20V. The anodised foils were subjected to morphological and structural characterizations. As-anodised foil was found to be amorphous or weakly crystalline. When the oxide was heat treated, x-ray diffraction analysis revealed the presence of (101) anatase at annealing temperature from 400-500°C. This indicates that the transformation occurs at this range of temperatures. Raman spectroscopy analysis showed the diminishing of anatase peaks for samples annealed at 500°C. At above 600°C, x-ray diffraction pattern shows a peak belonging to the rutile peak. Transformation from anatase to rutile is thought to occur at about 500°C with a more complete transformation at higher temperature. Annealing at higher than 600°C induces thickening of the nanotubes wall and at above 700°C, the nanotubes structure has completely disappeared.
A process to produce calcium phosphate biomaterial was done using an organic based diethylhexyl phosphoric acid (DEHPA) as its starting material. The gel obtained from this reaction was used to study calcium phosphate transformation using in-situ XRD with temperature ranges from room temperature to 1300 o C. The results obtained from this analysis show the following phase transformation sequence gel > β-Ca2P2O7 > β-TCP + HA > α-TCP + HA. β-Ca2P2O7 was formed at 400 o C and the sample when heated up to 1000 o C, peaks of β- TCP and HA appeared showing the transformation of the β-Ca2P2O7 phase. When the sample was heated up further to 1200 o C, β-TCP transformed into α-TCP.
MeSH terms: Biocompatible Materials; Calcium Phosphates; Phosphoric Acids; Temperature
A co-deposition of nickel-phosphorus-alumina (NiPA) composite coatings were obtained from an ordinary sulphate-based plating bath consisting of 5 g/l alumina (Al2O3) particles. The particles were dispersed by using mechanical agitation at 125 rpm. The presence of Ni3P and Al2O3 phases in the coatings was confirmed by XRD analysis. SEM/EDX results indicated that a smooth Ni3P coating was obtained and Al2O3 particles were embedded into the coating. Microscopic observation showed that the bonding between the Ni3P metal matrix and the Al2O3 ceramic particles was compact.
The land area of Tanah Putih, Gua Musang, Kelantan (Malaysia) is well-known for its wealth in industrial mineral resources, especially aluminosilicate of feldspar and mica. Natural feldspar and mica were physicochemically characterized with regard to X-ray diffraction (XRD), nitrogen sorption analysis and transmission electron microscopy (TEM) techniques for qualitative and quantitative identification of feldspar and mica. They show a good crystallinity, high surface area and uniformity of mesoporous structures. For the purpose of this experiment, the aluminosilicate of feldspar was modified either by acid treatment, or grafting the silanol groups present with various functional groups including aminopropyl-, octyl-, vinyl-, mercapto- and glycidoxy-triethoxysilanes, or activation of pre-treated support with glutaraldehyde. These support derivatives were used for further utilization in the immobilization of lipase from Candida rugosa and resulted in various interaction mechanisms between enzyme and introduced supports. It seemed that the features of the functionalized feldspar surfaces provide a preferable environmental host to enable the adsorption of lipase via interfacial adsorption method. Lipase immobilization onto feldspar support were further confirmed by scanning electron microscopy (SEM) coupled with energy dispersive X-ray microanalysis (EDX), transmission electron microscopy (TEM) and infra-red spectroscopy (FTIR) techniques. Enhancement of protein loading (up to 8.22 mg protein/g support) and immobilization yield (up to 78%) were shown by modified feldspar-lipase derivatives compared to unmodified feldspar support.
β-tricalcium phosphate (β-TCP) powders were synthesized by using various particles sizes (40 nm – 780 μm) calcium carbonate (CaCO3) and phosphoric acid (H3PO4) at room temperature (25 ˚C). The synthesized powders were characterized by using X-Ray Diffraction (XRD) method. The purity of β-TCP powders were determined from XRD pattern while the crystallite size of β-TCP powders were calculated by using Scherrer equation. Results shows that the purity of β-TCP powders were ranged from 20.33 % to 81.94 % while the crystallite size of β- TCP powders were ranged from 0.04391 μm to 0.06751 μm. From this work, particle size of CaCO3 will influenced the purity but not the mean crystallite size of synthesized β-TCP.
This study was designed to investigate the crystallite sizes of Porites species. A set of 9 Porites skeletons i.e. Porites australiensis, Porites cylindrica, Porites lutea, Porites lichen, Porites digitata, Porites nigrescens, Porites rus, Porites annae and Porites sp. were studied by using XRay Diffraction method. The values of FWHM and theta (θ) are used in Scherrer equation to determine the crystallite sizes of all Porites samples. It was found that the crystallite sizes were in the range of 1007.78 Ǻ – 1706.04 Ǻ.
The experiment aims to investigate the effect of high energy milling to the crystallite size of α-alumina. The starting material used is α-alumina powder with starting crystal size of 86nm. This powder was milled at different time ranges from 0 to 60 minutes and milling speed ranges from 400 rpm to 1100 rpm using a wet milling technique in corundum abrasive materials. The wet milling technique involved the use of water with the alumina to water ratio of 1:6.1. Samples prepared were then examined using the X-Ray Diffraction (XRD) to calculate the crystallite size and scanning electron microscope (SEM) was also used to determine changes in the morphology. Results from these analysis showed that the crystallite size will get smaller when milling speed and time of more than 600rpm and 30 minutes respectively were used. Optimum conditions to achieve the smallest crystal size of 79.7nm are 1000 rpm and 60 minutes.
Professional behavior is an area of medical education that has long been of concern to medical educator. Professional behavior is one of the domains of the professionalism and it’s a behavior reflection of professionalism. But in spite of its perceived importance, until recently it has not been actively taught or reliably assessed. The purposes of this writing are:
1) To provide appropriate definition of professional behavior.
2) To identify characteristics of professional behavior.
3) To identify valid and reliable assessment tools to assess professional behavior.
Background: Tertiary education environment has always been regarded as highly stressful to students. Medical training further adds to the already stressful environment. The stress of medical training was associated with negative consequences to the mental and physical health of medical students. We describe in this article a stress-management program known as the 'Medical Student Well-Being Workshop' in our medical school.
Methodology: The workshop was run over two half-days over a weekend. Prior to the workshop the society announced the workshop to the students and participation was voluntary. It was open to students from all years of the medical course except for first year students. A separate stress management workshop is planned for them.
Results: A total of 55 students participated in the workshop, out of which 55 (82%) were female students. The years of study were almost equally represented; 14 students (26%) from years two and three, 20 (37%) from year four and 6 (11%) from year five. All sessions were rated as highly useful; the lowest rated, the introduction session, obtained an overall usefulness rating of 3.73 out of the possible 5 (74.6%).
Conclusion: Medical Students Well-being Workshop is a promising intervention program in improving medical students' ability in managing stress. Perhaps similar approach can be considered relevant to be incorporated in other medical schools.