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Articles by R. Yunus
Total Records ( 5 ) for R. Yunus
  G.H. Chong , R. Yunus , N. Abdullah , T.S.Y. Choong and S. Spotar
  Problem statement: Literature on the production of nanoparticles using supercritical fluids is substantial, but comparatively much less for nanoencapsulation.
Approach:In this study, a modified Supercritical Anti Solvent (SAS) apparatus was fabricated for use in the production of nanoparticles using carbon dioxide as the supercritical fluid (SCF). SAS technique involves precipitation of solids from liquid solution under supercritical antisolvent-induced condition. Production of nanoparticles using SAS was investigated using 2 types of model solutes: Fume silica and acetaminophen which represent a model of water insoluble (inorganic) material and water soluble material respectively. The morphology and characteristics of nanoparticles produced were assessed.
Results:The fume silica had been coated and 50 nm diameter of nanoencapsulated acetaminophen had been produced.
The results had revealed that both water insoluble and soluble substrates can be coated and encapsulated successfully in polymer by the SAS coating process.
  R. Muniandy , H. Jafariahangari , R. Yunus and S. Hassim
  Due to the high oil prices the price of asphalt binder has increased tremendously. This scenario has warranted demand for higher viscosity cheaper asphalt for pavement construction. A study was conducted to take advantage of the Empty Fruit Bunch (EFB) of Date and Oil Palm trees (which are considered as waste) to produce cellulose fiber to be used as additives in the asphalt binder. If these EFB’s could be beneficially utilized in any application, it would reduce the load on the nation’s landfills and at the same time reducing the cost of road construction. A total of 11 blends were prepared that consisted of 5 blends with date palm fiber, 5 blends with oil palm fiber and one control sample that contained no fibers. The samples were evaluated using Dynamic Shear Rheometer (DSR) equipment in accordance with the superpave Strategic Highway Research Program (SHRP) requirements. The neat asphalt binders (Unaged), Rolling Thin Film Oven (RTFO) aged and Pressure Ageing Vessel (PAV) samples were then measured for phase angle, shear strain and complex shear modulus and then evaluated in accordance with SHRP requirements. The results indicated that the fibers enhanced the rheological performance of Bio Mastic Asphalt (BMA) blends. The control sample which was categorized as PG58 was enhanced to PG76 with 0.375% date palm fiber. The oil palm has also improved the blend up to PG70 with 0.3% oil palm fiber.
  R. Muniandy , Eltaher Aburkaba , R. Yunus , H. Hamid and H. Salihudin
  The performance of fillers in Stone Mastic Asphalt (SMA) pavements is unclear due to the various interaction effects of filler with asphalt binders, depending on the filler percentage, type and particle size. In this study, a laboratory investigation was conducted on the properties of asphalt binder and filler as a function of type and particle size. One asphalt binder and four filler types with different mineralogy were selected to assess the filler particle size and type effect. The selected fraction of mineral filler was blended with the asphalt binder in three different size proportions of 100/0, 50/50 and 0/100 passing the 75/20 micron sieve. To investigate the influence of filler particle size and type on mastics rheological and performance properties, Dynamic Shear Rheometer (DSR) was used over a broad range of temperatures and aging. The data obtained from this study led to the evaluation of the effects of filler type and the particle size on mastic performance. The analysis of data at the given filler/asphalt ratio showed that medium to coarse particle size filler improves the rutting and the coarse to medium particle size improves the fatigue cracking resistance of the tested mastics. Furthermore, the results from this study indicated that the fine particle size mastics seemed to lead a lower viscosity, higher penetration and lower softening point. The ceramic filler regardless the particle size was found to be more effective on producing mastics that are more elastic and less susceptible to rutting and cracking than the control mastic.
  A.M. Syam , R. Yunus , T.I.M. Ghazi and T.C.S. Yaw
  An improved method in biodiesel production using jatropha curcas oil is discussed in this study. There are two steps process involved namely esterification and transesterification. The first step serves as a pre-treatment process to reduce the free fatty acid content in the feedstock and the second step converts the oil into biodiesel. The reaction time, molar ratio, reaction temperature and percentage of catalyst loading are the operating parameters being optimized in the study. After the pre-treatment step, the free fatty acid content of jatropha oil has been reduced to less than 1%. The treated oil was transesterified using potassium hydroxide catalyst. The optimum conditions are 65°C, molar ratio of methanol to oil at 6:1, percentage of catalyst loading at 1% and reaction time of 60 min.
  G.H. Chong , S.Y. Spotar and R. Yunus
  A numerical procedure of mathematical model for mass transfer between a droplet of organic solvent and a compressed antisolvent is presented for conditions such that the two phases are fully miscible. The model is applicable to the supercritical antisolvent (SAS) method of particle formation. In this process, solute particles precipitate from an organic solution when sprayed into a compressed antisolvent continuum. Effects of operating temperature and pressure on droplet behavior were examined. The CO2 critical locus and the conditions for which the densities of solvent and carbon dioxide are equal are identified. Calculations were performed using Peng-Robinson equation of state. The model equations were put into the form that allowed the application of the Matlab standard solver pdepe. Calculations with toluene, ethanol, acetone (solvents) and carbon dioxide (antisolvent) demonstrated that droplets swell upon interdiffusion when the solvent is denser than the antisolvent and shrink when the antisolvent is denser. Diffusion modeling results might be used for data interpretation or experiments planning of the more complex real SAS process.
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