MyMedR

Displaying all 11 publications

Abstract:

Sort:

Fulltext A review: electrochemical performance of LSCF composite cathodes – influence of Ceria Electrolyte and metal elements

Bakar, M. S. A., Ahmad, S., Muchtar, A., Rahman, H. A .

Journal of Advanced Review on Scientific Research, 2014;1(1):1-9.
MyJurnal

Solid oxide fuel cells (SOFC) are efficient and clean power generation devices. Lowtemperature
SOFC (LTSOFC) has been developed since high-temperature SOFC (HTSOFC) is not
feasible to be commercialized due to cost. Lowering the operation temperature reduces its substantial
performance resulting from cathode polarization resistance and overpotential of cathode. The
development of composite cathodes regarding mixed ionic-electronic conductor (MIEC) and ceriabased
materials for LTSOFC minimizes the problems significantly and leads to an increase in
electrocatalytic activity for the occurrence of oxygen reduction reaction (ORR). Lanthanum-based
materials such as lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ) have been discovered
recently, which offer great compatibility with ceria-based electrolyte to be applied as composite
cathode materials for LTSOFC. Cell performance at lower operating temperature can be maintained
and further improved by enhancing the ORR. This paper reviews recent development of various ceriabased
composite cathodes especially related to the ceria-carbonate composite electrolytes for
LTSOFC. The influence of the addition of metallic elements such as silver (Ag), platinum (Pt) and
palladium (Pd) towards the electrochemical properties and performance of LSCF composite cathodes
are also discussed.
Fulltext Structural, Morphological, and Electron Transport Studies of Annealing Dependent In2O3 Dye-Sensitized Solar Cell

Mahalingam S, Abdullah H, Shaari S, Muchtar A, Asshari I

ScientificWorldJournal, 2015;2015:403848.
PMID: 26146652 DOI: 10.1155/2015/403848

Indium oxide (In2O3) thin films annealed at various annealing temperatures were prepared by using spin-coating method for dye-sensitized solar cells (DSSCs). The objective of this research is to enhance the photovoltaic conversion efficiency in In2O3 thin films by finding the optimum annealing temperature and also to study the reason for high and low performance in the annealed In2O3 thin films. The structural and morphological characteristics of In2O3 thin films were studied via XRD patterns, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM), EDX sampling, and transmission electron microscopy (TEM). The annealing treatment modified the nanostructures of the In2O3 thin films viewed through FESEM images. The In2O3-450 °C-based DSSC exhibited better photovoltaic performance than the other annealed thin films of 1.54%. The electron properties were studied by electrochemical impedance spectroscopy (EIS) unit. The In2O3-450 °C thin films provide larger diffusion rate, low recombination effect, and longer electron lifetime, thus enhancing the performance of DSSC.
Studies on the effects of titanate and silane coupling agents on the performance of poly (methyl methacrylate)/barium titanate denture base nanocomposites

Elshereksi NW, Ghazali MJ, Muchtar A, Azhari CH

J Dent, 2017 Jan;56:121-132.
PMID: 27916635 DOI: 10.1016/j.jdent.2016.11.012

OBJECTIVES: This study aimed to fabricate and characterise silanated and titanated nanobarium titanate (NBT) filled poly(methyl methacrylate) (PMMA) denture base composites and to evaluate the behaviour of a titanate coupling agent (TCA) as an alternative coupling agent to silane. The effect of filler surface modification on fracture toughness was also studied.
METHODS: Silanated, titanated and pure NBT at 5% were incorporated in PMMA matrix. Neat PMMA matrix served as a control. NBT was sonicated in MMA prior to mixing with the PMMA. Curing was carried out using a water bath at 75°C for 1.5h and then at 100°C for 30min. NBT was characterised via Fourier transform-infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis before and after surface modification. The porosity and fracture toughness of the PMMA nanocomposites (n=6, for each formulation and test) were also evaluated.
RESULTS: NBT was successfully functionalised by the coupling agents. The TCA exhibited the lowest percentage of porosity (0.09%), whereas silane revealed 0.53% porosity. Statistically significant differences in fracture toughness were observed among the fracture toughness values of the tested samples (p<0.05). While the fracture toughness of untreated samples was reduced by 8%, an enhancement of 25% was achieved after titanation. In addition, the fracture toughness of the titanated samples was higher than the silanated ones by 10%.
CONCLUSION: Formation of a monolayer on the surface of TCA enhanced the NBT dispersion, however agglomeration of silanated NBT was observed due to insufficient coverage of NBT surface. Such behaviour led to reducing the porosity level and improving fracture toughness of titanated NBT/PMMA composites. Thus, TCA seemed to be more effective than silane.
CLINICAL SIGNIFICANCE: Minimising the porosity level could have the potential to reduce fungus growth on denture base resin to be hygienically accepTable Such enhancements obtained with Ti-NBT could lead to promotion of the composites' longevity.
Fulltext Review of titanate coupling agents and their application for dental composite fabrication

Elshereksi NW, Ghazali M, Muchtar A, Azhari CH

Dent Mater J, 2017 Sep 26;36(5):539-552.
PMID: 28652551 DOI: 10.4012/dmj.2016-014

Silane is a dominant coupler that is widely used in dentistry to promote adhesion among the components of dental composites. Silica-based fillers can be easily silanized because of their similarly ordered structure. However, silane is hydrolytically degraded in the aqueous oral environment and inefficiently bonds to non-silica fillers. Thus, the development of hydrolytically stable dental composites is an important objective in the research on dental materials. Titanate coupling agents (TCAs) exhibit satisfactory interfacial bonding, enhanced homogeneous filler dispersion, and improved mechanical properties of the composites. Titanates also provide superior hydrolytic stability in wet environments, which should be considered in fabricating dental composites. The addition of a small amount of titanates can improve the resistance of the composites to moisture. This paper reviews the effects of the instability of silanes in moisture on the performance of dental composites and presents TCAs as alternative couplers to silanes for fabricating dental composites.
Fulltext Expression of Interleukin-1β and Histological Changes of the Three-Dimensional Oral Mucosal Model in Response to Yttria-Stabilized Nanozirconia

Nasarudin NA, Razali M, Goh V, Chai WL, Muchtar A

Materials (Basel), 2023 Mar 01;16(5).
PMID: 36903142 DOI: 10.3390/ma16052027

Over the years, advancement in ceramic-based dental restorative materials has led to the development of monolithic zirconia with increased translucency. The monolithic zirconia fabricated from nano-sized zirconia powders is shown to be superior in physical properties and more translucent for anterior dental restorations. Most in vitro studies on monolithic zirconia have focused mainly on the effect of surface treatment or the wear of the material, while the nanotoxicity of this material is yet to be explored. Hence, this research aimed to assess the biocompatibility of yttria-stabilized nanozirconia (3-YZP) on the three-dimensional oral mucosal models (3D-OMM). The 3D-OMMs were constructed using human gingival fibroblast (HGF) and immortalized human oral keratinocyte cell line (OKF6/TERT-2), co-cultured on an acellular dermal matrix. On day 12, the tissue models were exposed to 3-YZP (test) and inCoris TZI (IC) (reference material). The growth media were collected at 24 and 48 h of exposure to materials and assessed for IL-1β released. The 3D-OMMs were fixed with 10% formalin for the histopathological assessments. The concentration of the IL-1β was not statistically different between the two materials for 24 and 48 h of exposure (p = 0.892). Histologically, stratification of epithelial cells was formed without evidence of cytotoxic damage and the epithelial thickness measured was the same for all model tissues. The excellent biocompatibility of nanozirconia, as evidenced by the multiple endpoint analyses of the 3D-OMM, may indicate the potential of its clinical application as a restorative material.
Influence of alloying elements on cellular response and in-vitro corrosion behavior of titanium-molybdenum-chromium alloys for implant materials

Mat-Baharin NH, Razali M, Mohd-Said S, Syarif J, Muchtar A

J Prosthodont Res, 2020 Oct;64(4):490-497.
PMID: 32063537 DOI: 10.1016/j.jpor.2020.01.004

PURPOSE: Not all elements with β-stabilizing properties in titanium alloys are suitable for biomaterial applications, because corrosion and wear processes release the alloying elements to the surrounding tissue. Chromium and molybdenum were selected as the alloying element in this work as to find balance between the strength and modulus of elasticity of β-titanium alloys. This study aimed to investigate the effect of Titanium-10Molybdenum-10Chromium (Ti-10Mo-10Cr), Titanium-10Chromium (Ti-10Cr) and Titanium-10Molybdenum (Ti-10Mo) on the elemental leachability in tissue culture environment and their effect on the viability of human gingival fibroblasts (HGFs).
METHODS: Each alloy was immersed in growth medium for 0-21 days, and the elution was analyzed to detect the released metals. The elution was further used as the treatment medium and exposed to seeded HGFs overnight. The HGFs were also cultured directly to the titanium alloy for 1, 3 and 7 days. Cell viability was then determined.
RESULTS: Six metal elements were detected in the immersion of titanium alloys. Among these elements, molybdenum released from Ti-10Mo-10Cr had the highest concentration throughout the immersion period. Significant difference in the viability of fibroblast cells treated with growth medium containing metals and with direct exposure technique was not observed. The duration of immersion did not significantly affect cell viability. Nevertheless, cell viability was significantly affected after 1 and 7 days of exposure, when the cells were grown directly onto the alloy surfaces.
CONCLUSIONS: Within the limitation of this study, the newly developed β-titanium alloys are non-cytotoxic to human gingival fibroblasts.
Micro-computed tomography evaluation of dentinal microcracks following canal preparation with thermomechanically heat-treated engine-driven files

Arumugam S, Yew HZ, Baharin SA, Qamaruz Zaman J, Muchtar A, Kanagasingam S

Aust Endod J, 2021 Dec;47(3):520-530.
PMID: 33956372 DOI: 10.1111/aej.12516

This study aimed to evaluate and compare the frequency of microcracks and its severity at different root canal dentin locations, after preparation with thermomechanically heat-treated engine-driven nickel-titanium instruments. Forty mandibular premolars were assigned to four experimental groups (n = 10): ProTaper Next, ProTaper Gold, WaveOne Gold and Reciproc Blue. After pre-instrumentation micro-computed tomography scans, the root canals were prepared to size 25. Following post-instrumentation scans, pre- and post-instrumentation scanned images were analysed for the presence and extent of dentinal defects. A total of 56 500 cross-sectional images were obtained, showing that less than 2.3% with pre-existing dentinal microcracks. No new microcracks were identified during the post-instrumentation analyses. No significant association was found between the types of dentinal defects, file motions and sequences. Thermomechanically heat-treated rotary files did not induce the formation of new microcracks. There was also no association between the kinematic motions and sequences of the rotary instruments to the types of dentinal defects.
Fulltext Microstructural and mechanical behaviours of Y-TZP prepared via slip-casting and fused deposition modelling (FDM)

Gnanasagaran CL, Ramachandran K, Jamadon NH, Kumar VH, Muchtar A, Pazhani A, et al.

Heliyon, 2023 Nov;9(11):e21705.
PMID: 37954343 DOI: 10.1016/j.heliyon.2023.e21705

This paper reports the microstructural characteristics and mechanical properties of yttria-stabilized zirconia prepared via fused deposition modelling and slip casting. X-Ray Diffraction peaks indicated that yttria-stabilized zirconia crystallized in tetragonal structure for both slip casted(SC) and fused deposition modelled(FDM) samples. Further, scanning electron microscopy of slip casted sample showcased closely packed structure with fine grains and an average grain size of ∼65 nm whilst fused deposition modelled samples showcased non-homogeneous pores with ∼20 nm grain size. Average relative density of slip casted samples was ∼99.4 % while that of fused deposition modelled sample exhibited ∼96.2 %. The Vickers Hardness of slip casted (∼15.26 ± 0.4 GPa) was ∼10 % higher than the fused deposition modelled samples (∼13.79 ± 0.3 GPa). Likewise, indentation fracture toughness of slip casted (5.78 ± 0.5 MPa m1/2) was 14 % higher than fused deposition modelled samples which could have been due to the change in grain size as well as porosity of the ceramics. Compressive strength of the fused deposition modelled samples was 32 % less than slip casted samples (∼510 ± 10 MPa) due to its non-homogenous pores which led to weakening van der Waals force of attraction.
Effect of porcelain veneering technique in bilayered zirconia on bond strength and residual stress distribution

Teng WS, Yew HZ, Jamadon NH, Qamaruz Zaman J, Meor Ahmad MI, Muchtar A

J Mech Behav Biomed Mater, 2024 Mar;151:106361.
PMID: 38176199 DOI: 10.1016/j.jmbbm.2023.106361

The use of all porcelain materials in dentistry has significantly increased in recent years. However, chipping has remained a common problem that affects bilayered zirconia restorations. Bonding between porcelain and the underlying zirconia framework is crucial to the success of the restoration. The bond strength may be affected by such factors as residual thermal stress and the veneering technique. This research focuses on investigating the potential and constraints of materials through an examination of the porcelain veneering technique, particularly hand-layering and heat-pressing. Forty-two cylindrical disc samples of zirconia (n = 7/group) were fabricated in the dimensions of 10 × 1.2 mm (diameter [D] × height [H]). The zirconia specimens were milled from IPS e.max® ZirCad [Z] block and Luxen Zr [L] block (n = 21/zirconia). The zirconia cores were layered with IPS e.max® Zirliner and heat-pressed with IPS e.max® ZirPress to produce a final veneer dimension of 5 × 3 mm (D × H). Conventional layering was performed for the rest of the zirconia cores using IPS e.max® Ceram and Shofu Vintage Zr. The final study groups were Luxen-Vintage (LV), Luxen-Ceram (LC), Luxen Zirpress (LP), ZirCad-Vintage (ZV), ZirCad-Ceram (ZC) and ZirCad-Zirpress (ZP). Five samples were subjected to shear bond testing (SBS) with a universal testing machine with a 5 kN load cell and 0.5 mm/min crosshead speed (n = 5/group). A sample underwent nanoindentation, and another was sectioned using Isomet machine to study the bonding interface. One-way ANOVA was used to run the statistical analyses of the SBS test. Statistical differences were found between ZV with LC and LP (p
Fulltext Effect of sintering parameters on physical and mechanical properties of powder injection moulded stainless steel-hydroxyapatite composite

Ramli MI, Sulong AB, Muhamad N, Muchtar A, Arifin A, Mohd Foudzi F, et al.

PLoS One, 2018;13(10):e0206247.
PMID: 30359433 DOI: 10.1371/journal.pone.0206247

The combination of metallic bio-inert material, stainless-steel 316L (SS316L) and a bio-active material, hydroxyapatite (HA) can produce a composite which has superior properties for orthopaedic applications. The main objective of this study is to investigate the effects of sintering temperature and holding time on the physical and mechanical properties of the sintered part. 50wt.% SS316L and 50wt.% HA were mixed with a binder system of palm stearin (PS) and polyethylene (PE) at 61 vol.% powder loading. Rheological properties show a pseudo-plastic behaviour of the feedstock, where viscosity decreases with increasing shear rate. The feedstock was injection moulded into a tensile bar shape while thermal debinding was carried out at 320°C and 500°C. The brown parts were sintered at 1000, 1100, 1200 and 1300°C, with three different sintering times of 1, 3 and 5 hours in the furnace. It was found that the highest sintered density measured was 95.61% of the theoretical density. In addition, the highest hardness and Young's modulus measured were 150.45 HV and 52.61 GPa respectively, which are higher than those of human bone. The lowest percentage of carbon content was 0.022wt.% given by the sample sintered at 1300°C for 1 hour. Therefore, SS316L/HA composite with good mechanical and physical properties was successfully produced through the PIM process.
Low-cost novel clay earthenware as separator in microbial electrochemical technology for power output improvement

Daud SM, Daud WRW, Bakar MHA, Kim BH, Somalu MR, Muchtar A, et al.

Bioprocess Biosyst Eng, 2020 Aug;43(8):1369-1379.
PMID: 32193754 DOI: 10.1007/s00449-020-02331-7

A conventional reactor in microbial electrochemical technology (MET) consists of anode and cathode compartments divided by a separator, which is usually a proton exchange membrane (PEM), such as Nafion 117. In this study, a novel porous clay earthenware (NCE) was fabricated as the separator to replace the highly cost PEM. The fabrication of NCEs is with raw clay powder and starch powder that acts as a pore-forming agent at different starch powder contents (10 vol%, 20 vol%, and 30 vol%), ball-milled before hydraulically pressed to form green ceramic pellets and sintered up to 1200 °C. The highest power density of 2250 ± 21 mW/m2 (6.0 A/m2), the internal resistance of 75 ± 24 Ω and coulombic efficiency (CE) of 44 ± 21% were produced for MFC-NCE from 30 vol% starch powder content under batch mode operation. The MFC-PEM combination produced the lowest power density, CE and the highest internal resistance up to 1350 ± 17 mW/m2 (3.0 A/m2), 23 ± 15% and 326 ± 13 Ω, respectively.

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links