Displaying publications 1 - 20 of 34 in total

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  1. Photocatalytic remediation of organic waste over Keggin-based polyoxometalate materials: A review
    Lai SY, Ng KH, Cheng CK, Nur H, Nurhadi M, Arumugam M
    Chemosphere, 2021 Jan;263:128244.
    PMID: 33297191 DOI: 10.1016/j.chemosphere.2020.128244
    Photocatalytic remediation of industrial water pollution has courted intense attention lately due to its touted green approach. In this respect, Keggin-based polyoxometalates (POMs) as green solid acids in photocatalytic reaction possess superior qualities, viz. unique photoinduced charge-transfer properties, strong photooxidative-photoreductive ability, high chemical and thermal stability, and so forth. Unfortunately, it suffers from a large bandgap energy, low specific surface area, low recoverability, and scarce utilization in narrow absorption range. Therefore, the pollutant degradation performance is not satisfactory. Consequently, multifarious research to enhance the photocatalytic performance of Keggin-based POMs were reported, viz. via novel modifications and functionalizations through a variety of materials, inclusive of, inter alia, metal oxides, transition metals, noble metals, and others. In order to advocate this emerging technology, current review work provides a systematic overview on recent advancement, initiated from the strategized synthetic methods, followed by hierarchical enhancement and intensification process, at the same time emphasizes on the fundamental working principles of Keggin-based POM nanocomposites. By reviewing and summarizing the efforts adopted global-wide, this review is ended with providing useful outlooks for future studies. It is also anticipated to shed light on producing Keggin-based POM nanocomposites with breakthrough visible- and solar-light-driven photocatalytic performance against recalcitrant organic waste.
    Matched MeSH terms: Tungsten Compounds*
  2. Fulltext Perbandingan dos glandular purata payudara berdasarkan kombinasi anod/penuras tungsten/rhodium dan tungsten/argentum pada mamografi digital
    Chelliah, Kanaga Kumari, Lumin, Felecia
    Jurnal Sains Kesihatan Malaysia, 2012;10(1):53-56.
    MyJurnal
    Mamografi adalah cara paling efektif untuk mengesan keabnormalan payudara di kalangan wanita. Namun, mamografi dipercayai boleh menyebabkan karsinogenesis aruhan sinaran. Justeru pengukuran dos adalah penting untuk menganggar risiko dan mengawal kualiti imej. Kajian ini dijalankan untuk membandingkan dos glandular purata (AGD) yang diperolehi fantom payudara berdasarkan dua kombinasi anod/penuras yang berbeza iaitu tungsten/rhodium (W/Rh) dan tungsten/argentum (W/Ag). Fantom payudara CIRS 012A didedahkan pada projeksi kraniokaudal (CC) menggunakan sistem mamografi digital Hologic Selenia. Kerma udara kemasukan permukaan (ESAK) diukur menggunakan dosimeter pendar cahaya terma (TLD). AGD diperolehi daripada pengiraan asas ESAK dengan faktor penukaran berdasarkan formula Euref. Ujian t tak bersandar menunjukkan perbezaan bererti dalam purata AGD yang diperolehi. Purata AGD W/Rh adalah lebih tinggi berbanding purata AGD W/Ag (p = 0.002, 95% CI: 0.22, 0.53). Kesimpulannya, penggunaan W/Ag menyumbang kepada pengurangan dos semasa pemeriksaan mamografi.
    Matched MeSH terms: Tungsten
  3. Nanostructured tungsten trioxide thin films synthesized for photoelectrocatalytic water oxidation: a review
    Zhu T, Chong MN, Chan ES
    ChemSusChem, 2014 Nov;7(11):2974-97.
    PMID: 25274424 DOI: 10.1002/cssc.201402089
    The recent developments of nanostructured WO3 thin films synthesized through the electrochemical route of electrochemical anodization and cathodic electrodeposition for the application in photoelectrochemical (PEC) water splitting are reviewed. The key fundamental reaction mechanisms of electrochemical anodization and cathodic electrodeposition methods for synthesizing nanostructured WO3 thin films are explained. In addition, the effects of metal oxide precursors, electrode substrates, applied potentials and current densities, and annealing temperatures on size, composition, and thickness of the electrochemically synthesized nanostructured WO3 thin films are elucidated in detail. Finally, a summary is given for the general evaluation practices used to calculate the energy conversion efficiency of nanostructured WO3 thin films and a recommendation is provided to standardize the presentation of research results in the field to allow for easy comparison of reported PEC efficiencies in the near future.
    Matched MeSH terms: Tungsten/chemistry*
  4. Fulltext Selective formation of tungsten nanowires
    Bien DC, Saman RM, Badaruddin SA, Lee HW
    Nanoscale Res Lett, 2011;6(1):543.
    PMID: 21970543 DOI: 10.1186/1556-276X-6-543
    We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.
    Matched MeSH terms: Tungsten
  5. Fulltext Characterization of fusion welded joint: a review
    Nur Azida Che Lah, Aidy Ali, Napsiah Ismail
    Pertanika Journal of Science & Technology, 2009;17(2):-.
    MyJurnal
    Welding process is most widely used in joining components or structures in industry. Although welding is part of a larger category called metals joining, the weld itself still gives significant problems to engineers, researchers and manufacturers until today. Several widely used welding processes, such as the Metal Inert Gas (MIG), Tungsten Inert Gas (TIG), and Manual Metal Arc (MMA), were studied. In the present paper, the characterization of the macrostructure, microstructure, hardness and residual stress distribution are highlighted and discussed to achieve a better understanding of the welded quality which is crucial in determining the welded products.
    Matched MeSH terms: Tungsten
  6. Engineering surface oxygen defects on tungsten oxide to boost photocatalytic oxygen evolution from water splitting
    Chew YH, Tang JY, Tan LJ, Choi BWJ, Tan LL, Chai SP
    Chem Commun (Camb), 2019 May 28;55(44):6265-6268.
    PMID: 31086906 DOI: 10.1039/c9cc01449g
    The engineering of surface oxygen vacancies (OVs) in WO3 was primitively done using a facile solvothermal method. The photocatalytic activities of the as-prepared samples were studied by evaluating their performances in the photocatalytic OER. The best sample (W-3) yielded 57.6 μmol of O2 in 6 h under the illumination of simulated sunlight.
    Matched MeSH terms: Tungsten
  7. Characterisation of micro-sized and nano-sized tungsten oxide-epoxy composites for radiation shielding of diagnostic X-rays
    Azman NZ, Siddiqui SA, Low IM
    Mater Sci Eng C Mater Biol Appl, 2013 Dec 1;33(8):4952-7.
    PMID: 24094209 DOI: 10.1016/j.msec.2013.08.023
    Characteristics of X-ray transmissions were investigated for epoxy composites filled with 2-10 vol% WO3 loadings using synchrotron X-ray absorption spectroscopy (XAS) at 10-40 keV. The results obtained were used to determine the equivalent X-ray energies for the operating X-ray tube voltages of mammography and radiology machines. The results confirmed the superior attenuation ability of nano-sized WO3-epoxy composites in the energy range of 10-25 keV when compared to their micro-sized counterparts. However, at higher synchrotron radiation energies (i.e., 30-40 keV), the X-ray transmission characteristics were similar with no apparent size effect for both nano-sized and micro-sized WO3-epoxy composites. The equivalent X-ray energies for the operating X-ray tube voltages of the mammography unit (25-49 kV) were in the range of 15-25 keV. Similarly, for a radiology unit operating at 40-60 kV, the equivalent energy range was 25-40 keV, and for operating voltages greater than 60 kV (i.e., 70-100 kV), the equivalent energy was in excess of 40 keV. The mechanical properties of epoxy composites increased initially with an increase in the filler loading but a further increase in the WO3 loading resulted in deterioration of flexural strength, modulus and hardness.
    Matched MeSH terms: Tungsten/chemistry*
  8. Synthesis, structure and theoretical investigation into a homoleptic tris(dithiolene) tungsten
    Arifin K, Minggu LJ, Daud WR, Yamin BM, Daik R, Kassim MB
    Spectrochim Acta A Mol Biomol Spectrosc, 2014;120:208-15.
    PMID: 24184623 DOI: 10.1016/j.saa.2013.09.069
    A new homoleptic dithiolene tungsten complex, tris-{1,2-bis(3,5-dimethoxyphenyl)-1,2-ethylenodithiolene-S,S'}tungsten, was successfully synthesized via a reaction of the thiophosphate ester and sodium tungstate. The thiophosphate ester was prepared from 3,5-dimethoxybenzaldehyde via benzoin condensation to produce the intermediate 1,2-bis-(3,5-dimethoxyphenyl)-2-hydroxy-ethanone compound, followed by a reaction of the intermediate with phosphorus pentasulfide. FTIR, UV-Vis spectroscopy, 1H NMR and 13C NMR and elemental analysis confirmed the product as tris{1,2-bis-(3,5-dimethoxyphenyl)-1,2-ethylenodithiolene-S,S'}tungsten with the molecular formula of C54H54O12S6W. Crystals of the product adopted a monoclinic system with space group of P2(1)/n, where a=12.756(2) Å, b=21.560(3) Å, c=24.980(4) Å and β=103.998(3)°. Three thioester ligands were attached to the tungsten as bidentate chelates to form a distorted octahedral geometry. Density functional theory calculations were performed to investigate the molecular properties in a generalized-gradient approximation framework system using Perdew-Burke-Ernzerhof functions and a double numeric plus polarization basis set. The HOMO was concentrated on the phenyl ligands, while the LUMO was found along the W(S2C2)3 rings. The theoretical optical properties showed a slight blue shift in several low dielectric solvents. The solvatochromism effect was insignificant for high polar solvents.
    Matched MeSH terms: Tungsten/chemistry*
  9. A Novel Optical Complex between an Organic Substrate and a Polyoxometalate. Crystal and Molecular Structure of alpha-H(4)SiW(12)O(40).4HMPA.2H(2)O (HMPA = Hexamethylphosphoramide)
    Niu Jy Jy, You Xz Xz, Duan Cy Cy, Fun Hk Hk, Zhou Zy Zy
    Inorg Chem, 1996 Jul 03;35(14):4211-4217.
    PMID: 11666630
    A solvated complex of alpha-H(4)SiW(12)O(40).4HMPA.2H(2)O composed the heteropolytungstate alpha-H(4)SiW(12)O(40) and the organic substrate hexamethylphosphoramide (HMPA) has been synthesised, purified, and characterized. The electronic spectra (lambda = 220-500 nm) as well as the (1)H NMR spectra for the title compound dissolved in CD(3)CN establish that this complex dissociates into free SiW(12)O(40)(4)(-) and HMPA moieties in solution unless the organic substrate HMPA is present in very high concentrations. The solid reflectance electronic spectra and IR spectra indicate that there is interaction between the alpha-H(4)SiW(12)O(40) and the organic substrate. The complex has no photosensitivity under irradiation of sunlight, but under the near-UV light result in a charge transfer by oxidation of the HMPA and the reduction of the polyoxometalate. Light yellow polyhedrons of the title compound crystallize from the aqueous solvent of acetonitrile and aqueous solution as the formula of alpha-H(4)SiW(12)O(40).4HMPA.2H(2)O in the monoclinic, space group P2(1). The unit cell has a = 12.791(3) Å, b = 22.103(6) Å, c = 15.532(4) Å, beta = 102.860(10) degrees, and Z = 2. From the bond-valence parameters, it was found that the four hydrogen atoms of the polyoxometalate were combined with the N atoms of the four HMPA respectively. The title compound shows a certain second-order and third-order nonlinear optical response of I(2)(omega) = 0.7I(2)(omega)(KDP) and chi((3)) = 2.63 x 10(-)(11) esu, respectively.
    Matched MeSH terms: Tungsten Compounds
  10. Fulltext Investigation of Surface Plasmon Resonance (SPR) in MoS2- and WS2-Protected Titanium Side-Polished Optical Fiber as a Humidity Sensor
    Zakaria R, Zainuddin NAM, Leong TC, Rosli R, Rusdi MF, Harun SW, et al.
    Micromachines (Basel), 2019 Jul 11;10(7).
    PMID: 31336745 DOI: 10.3390/mi10070465
    In this paper, we report the effects of a side-polished fiber (SPF) coated with titanium (Ti) films in different thicknesses, namely 5 nm, 13 nm, and 36 nm, protected by a thin layer of transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), which provide ultra-sensitive sensor-based surface plasmon resonance (SPR) covering from the visible to mid-infrared region. The SPF deposited with Ti exhibits strong evanescent field interaction with the MoS2 and WS2, and good optical absorption, hence resulting in high-sensitivity performance. Incremental increases in the thickness of the Ti layer contribute to the enhancement of the intensity of transmission with redshift and broad spectra. The findings show that the optimum thickness of Ti with 36 nm combined with MoS2 causes weak redshifts of the longitudinal localized surface plasmon resonance (LSPR) mode, while the same thickness of Ti with WS2 causes large blueshifts. The redshifts are possibly due to a reduced plasmon-coupling effect with the excitonic region of MoS2. The observed blueshifts of the LSPR peak position are possibly due to surface modification between WS2 and Ti. Changing the relative humidity from 58% to 88% only elicited a response in Ti/MoS2. Thus, MoS2 shows more sensitivity on 36-nm thickness of Ti compared with WS2. Therefore, the proposed fiber-optic sensor with integration of 2D materials is capable of measuring humidity in any environment.
    Matched MeSH terms: Tungsten
  11. Fulltext Tungsten-based material as promising new lead-free gamma radiation shielding material in nuclear medicine
    Jamal AbuAlRoos N, Azman MN, Baharul Amin NA, Zainon R
    Phys Med, 2020 Oct;78:48-57.
    PMID: 32942196 DOI: 10.1016/j.ejmp.2020.08.017
    PURPOSE: The main objective of this study was to evaluate the efficacy of tungsten carbide as new lead-free radiation shielding material in nuclear medicine by evaluating the attenuation properties.

    MATERIALS AND METHODS: The elemental composition of tungsten carbide was analysed using Field-Emission Scanning Electron Microscopy (FESEM) with energy dispersive X-ray (EDX). The purity of tungsten carbide was 99.9%, APS: 40-50 µm. Three discs of tungsten carbide was fabricated with thickness of 0.1 cm, 0.5 cm and 1.0 cm. Three lead discs with similar thickness were used to compare the attenuation properties with tungsten carbide discs. Energy calibration of gamma spectroscopy was performed by using 123I, 133Ba, 152Eu, and 137Cs. Gamma radiation from these sources were irradiated on both materials at energies ranging from 0.160 MeV to 0.779 MeV. The experimental attenuation coefficients of lead and tungsten carbide were compared with theoretical attenuation coefficients of both materials from NIST database. The half value layer and mean free path of both materials were also evaluated in this study.

    RESULTS: This study found that the peaks obtained from gamma spectroscopy have linear relationship with all energies used in this study. The relative differences between the measured and theoretical mass attenuation coefficients are within 0.19-5.11% for both materials. Tungsten carbide has low half value layer and mean free path compared to lead for all thickness at different energies.

    CONCLUSION: This study shows that tungsten carbide has high potential to replace lead as new lead-free radiation shielding material in nuclear medicine.

    Matched MeSH terms: Tungsten
  12. Fulltext Use of an Industrial Tungsten Carbide Drill in the Treatment of a Complex Fracture in a Patient with Severe Osteopetrosis: A Case Report
    Kunnasegaran R, Chan YH
    Malays Orthop J, 2017 Mar;11(1):64-67.
    PMID: 28435578 DOI: 10.5704/MOJ.1703.007
    The treatment of fractures in osteopetrosis can be complicated and difficult. We describe the use of an industrial grade tungsten carbide drill bit in the treatment of one of these complex fractures. An industrial grade tungsten carbide drill bit was used to fashion a medullary canal in the surgical treatment of a left peri-implant fracture of the neck of femur in a patient with osteopetrosis. The patient was successfully treated with a hemiarthroplasty with good functional outcomes. A tungsten carbide drill bit serves as an effective and safe option in the treatment of osteopetrotic femoral neck fractures.
    Matched MeSH terms: Tungsten Compounds
  13. Evaluation of production cross-sections for186Re theranostic radionuclide via charged-particle induced reactions on Tungsten
    Ali SKI, Khandaker MU, Kassim HA
    Appl Radiat Isot, 2018 May;135:239-250.
    PMID: 29448240 DOI: 10.1016/j.apradiso.2018.01.035
    186
    Re (T1/2= 89.24 h, [Formula: see text] 346.7 keV, [Formula: see text] ), an intense beta-emitter shows great potential to be used as an active material in therapeutic radiopharmaceuticals due to its suitable physico-chemical properties.186Re can be produced in several ways, however charged-particle induced reactions show to be promising towards no carrier added production. In this work, production cross-sections of186Re were evaluated following the light-charged particle induced reactions on tungsten. An effective evaluation technique such as Simultaneous Evaluation on KALMAN code combined with least squares concept was used to obtain the evaluated data together with covariances. Knowledge of the underlying uncertainties in evaluated nuclear data, i.e., covariances are useful to improve the accuracy of nuclear data.
    Matched MeSH terms: Tungsten
  14. Fulltext 56 nm Wide-Band Tunable Q-Switched Erbium Doped Fiber Laser with Tungsten Ditelluride (WTe2) Saturable Absorber
    Ahmad H, Albaqawi HS, Yusoff N, Yi CW
    Sci Rep, 2020 Jun 17;10(1):9860.
    PMID: 32555280 DOI: 10.1038/s41598-020-66664-9
    A wide-band and tunable Q-switched erbium-doped fiber (EDF) laser operating at 1560.5 nm with a tungsten ditelluride (WTe2) saturable absorber (SA) is demonstrated. The semi-metallic nature of WTe2 as well as its small band gap and excellent nonlinear optical properties make it an excellent SA material. The laser cavity uses an 89.5 cm long EDF, pumped by a 980 nm laser diode as the linear gain while the WTe2 based SA generates the pulsed output. The WTe2 based SA has a modulation depth, non-saturable loss and saturation intensity of about 21.4%, 78.6%, and 0.35 kW/cm2 respectively. Stable pulses with a maximum repetition rate of 55.56 kHz, narrowest pulse width of 1.77 µs and highest pulse energy of 18.09 nJ are obtained at the maximum pump power of 244.5 mW. A 56 nm tuning range is obtained in the laser cavity, and the output is observed having a signal to noise ratio (SNR) of 48.5 dB. The demonstrated laser has potential for use in a large number of photonics applications.
    Matched MeSH terms: Tungsten
  15. Fulltext WS2: A New Window Layer Material for Solar Cell Application
    Bin Rafiq MKS, Amin N, Alharbi HF, Luqman M, Ayob A, Alharthi YS, et al.
    Sci Rep, 2020 Jan 21;10(1):771.
    PMID: 31964954 DOI: 10.1038/s41598-020-57596-5
    Radio frequency (RF) magnetron sputtering was used to deposit tungsten disulfide (WS2) thin films on top of soda lime glass substrates. The deposition power of RF magnetron sputtering varied at 50, 100, 150, 200, and 250 W to investigate the impact on film characteristics and determine the optimized conditions for suitable application in thin-film solar cells. Morphological, structural, and opto-electronic properties of as-grown films were investigated and analyzed for different deposition powers. All the WS2 films exhibited granular morphology and consisted of a rhombohedral phase with a strong preferential orientation toward the (101) crystal plane. Polycrystalline ultra-thin WS2 films with bandgap of 2.2 eV, carrier concentration of 1.01 × 1019 cm-3, and resistivity of 0.135 Ω-cm were successfully achieved at RF deposition power of 200 W. The optimized WS2 thin film was successfully incorporated as a window layer for the first time in CdTe/WS2 solar cell. Initial investigations revealed that the newly incorporated WS2 window layer in CdTe solar cell demonstrated photovoltaic conversion efficiency of 1.2% with Voc of 379 mV, Jsc of 11.5 mA/cm2, and FF of 27.1%. This study paves the way for WS2 thin film as a potential window layer to be used in thin-film solar cells.
    Matched MeSH terms: Tungsten
  16. Synthesis of tungsten oxide/ amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO3/N-CQDs) composites for methylene blue removal
    Nugraha MW, Zainal Abidin NH, Supandi, Sambudi NS
    Chemosphere, 2021 Aug;277:130300.
    PMID: 33774232 DOI: 10.1016/j.chemosphere.2021.130300
    In this present study, the tungsten oxide/amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO3/N-CQDs) composite has successfully been prepared through a simple mixing process. The WO3 was synthesized through a precipitation method, and CQDs were amino-functionalized using ethylenedinitrilotetraacetic acid (EDTA) and ethylenediamine (EDA) through one-pot hydrothermal method. It is revealed that N-CQDs incorporation into WO3 alters the bandgap energy, crystallinity, surface area, and photoluminescence (PL) properties. The produced composites exhibit higher monoclinic WO3 crystallinity, larger surface area, lower bandgap energy and quenched photoluminescence intensity. The as-prepared WO3/N-CQDs composites exhibit better adsorption and photocatalytic degradation performance of methylene blue (MB) than the pristine WO3. It shows that the combination of N-CQDs and WO3 enhanced visible light absorption, by lowering the bandgap energy of WO3 from 2.175 to 1.495 eV. The best performance composite is WO3/N-CQDs EDA 2.5% with an efficiency of 96.86%, removal rate constant of 0.02017/min, and chemical oxidation demand (COD) removal efficiency achieved 84.61%. Moreover, the WO3/N-CQDs EDA 2.5% shows a significant photocatalytic activity even at higher MB initial concentration with 92.93% removal for 50 ppm MB. Subsequently, the composite also has good stability after a sequential 3-times cycle of degradation with 86.85% removal. The increasing photocatalytic performance is affected by the quenching effect of PL and lower bandgap energy. The lower intensity of the PL indicates the reduced charge carrier recombination resulting in increased photocatalytic activity. The combination of N-CQDs and WO3 resulted in improved photodegradation, which shows its significant potential to be utilized for wastewater treatment.
    Matched MeSH terms: Tungsten
  17. Fulltext Depth of polymerization of a new nanocomposite according to different exposure times and shades
    Lui, J.L., Chan, C.L., Yap, K.T.
    Ann Dent, 2006;13(1):6-11.
    MyJurnal
    The aim of the study was to determine the depth of cure of a new nanocomposite when exposed to different curing times and also when different shades were polymerized. The nanocomposite, Filtek Supreme (3M ESPE), was packed into 96 plastic cylindrical moulds measuring 4 mm in internal diameter and 8 mm in length and then polymerized using a conventional quartz-tungsten-halogen light curing unit. The first part of the study involved curing 16 samples each of A2 shade of the nanocomposite at exposure times of 20s, 40s, 60s and 120s. For the second part, a similar number of samples of the dentinal opacity shades of A2, B3 and A4 of the nanocomposite were polymerized at a constant exposure time of 40s. The depth of polymerization of the nanocomposite in each sample was measured using a digimatic indicator. Curing depths were found to increase significantly (P < 0.05) with longer exposure time (20s < 40s < 60s < 120s) and decrease significantly with darker shades (A2 > B3 > A4).
    Matched MeSH terms: Tungsten
  18. Fulltext A survey on light intensity outputs of QTH, cabled and cordless LED light curing units
    Athirah Ab Rahman, Adam Husein, Hany Mohamed Aly Ahmed, Dasmawati Mohamad, Wan Zaripah Wan Bakar, Manal Farea, et al.
    Archives of Orofacial Sciences, 2014;9(2):85-90.
    MyJurnal
    Light intensity output is one of the determinants for adequate curing of visible light-cured materials. The aim of this survey was to evaluate the light intensity outputs (LIOs) of light curing units (LCUs) in dental clinics of Hospital Universiti Sains Malaysia (HUSM) and School of Dental Sciences, Universiti Sains Malaysia (USM). The respective LIOs of all functioning Quartz Tungsten Halogen (QTH) and Light Emitting Diode (LED) LCUs were tested using two light radiometers. For cordless LED LCUs, the testing procedure was done in situ and after being fully charged. Statistical analysis using Kruskal Wallis and Wilcoxon signed ranks tests were performed to compare the LIOs between groups and between the LIOs of in situ and post-charged cordless LED LCUs, respectively. The level of significance was set at 0.05 (p
    Matched MeSH terms: Tungsten
  19. Characterization of the feedstock properties of metal injection-molded WC-Co with palm stearin binder system
    Sri Yulis M. Amin, Norhamidi Muhamad, Khairur Rijal Jamaludin, Fayyaz A, Heng SY
    Sains Malaysiana, 2014;43:123-128.
    Feedstock preparation, as well as its characterization, is crucial in the production of highly sintered parts with minimal defect. The hard metal powder - particularly, cemented carbide (wc-co) used in this study was investigated both physically and thermally to determine its properties before the mixing and injection molding stage. Several analyses were conducted, such as scanning electron microscopy, energy dispersive X-ray diffraction, pycnometer density, critical powder volume percentage (cPvP), as well as thermal tests, such as thermogravimetric analysis and differential scanning calorimetry. On the basis of the CPVP value, the feedstock, consisting of wc-co powder, was mixed with 60% palm stearin and 40% polyethylene at an optimal powder loading, within 2 to 5% lower than the CPVP value. The CPVP spotted value was 65%. The feedstock optimal value at 61% showed good rheological properties (pseudoplastic behavior) with an n value lower than 1, considerably low activation energy and high moldability index. These preliminary properties of the feedstock serve as a benchmark in designing the schedule for the next whole steps (i.e. injection, debinding and sintering processes).
    Matched MeSH terms: Tungsten
  20. Fulltext Biodiesel synthesis catalyzed by transition metal oxides: ferric-manganese doped tungstated/molybdena nanoparticle catalyst
    Alhassan FH, Rashid U, Taufiq-Yap YH
    J Oleo Sci, 2015;64(1):91-9.
    PMID: 25492234 DOI: 10.5650/jos.ess14161
    The solid acid Ferric-manganese doped tungstated/molybdena nananoparticle catalyst was prepared via impregnation reaction followed by calcination at 600°C for 3 h. The characterization was done using X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), X-ray fluorescence (XRF), Transmission electron microscope (TEM) and Brunner-Emmett-Teller surface area measurement (BET). Moreover, dependence of biodiesel yield on the reaction variables such as the reaction temperature, catalyst loading, as well as molar ratio of methanol/oil and reusability were also appraised. The catalyst was reused six times without any loss in activity with maximum yield of 92.3% ±1.12 achieved in the optimized conditions of reaction temperature of 200°C; stirring speed of 600 rpm, 1:25 molar ratio of oil to alcohol, 6 % w/w catalyst loading as well as 8 h as time of the reaction. The fuel properties of WCOME's were evaluated, including the density, kinematic viscosity, pour point, cloud point and flash point whereas all properties were compared with the limits in the ASTM D6751 standard.
    Matched MeSH terms: Tungsten Compounds/chemistry*
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