Advanced Materials Research Vols. 93-94

Abstract: The aim of this work was to prepare mesoporous silicas derived from rice husk ash (RHA) using three different depolymerizing agents; glycerol, 1,3 propanediol and 1,4 butanediol. The reaction of RHA with different depolymerizing agents was carried out between 200-250°C for 2 hrs. The solution was then hydrolyzed with deionized water to obtain gels. After a few washing step, gels were oven-dried and calcined at 500 °C for 24 hrs. Prepared mesoporous silicas were then characterized using Nitrogen adsorption-desorption measurement, FTIR, TGA, SEM, XRD and XRF. The percent hydrophobicity was determined based on the amount of moisture absorbed using TGA. It was shown that RHA reacted with depolymerizing agents above 200°C to form gels, which, after hydrolysis and calcination, still maintained the mesoporous characteristics. The BET and SEM results indicated that the RHA reacted with 1,3 propanediol had highest pore volume (0.95 cm3/g) and specific surface area (129.30 m2/g) compared to RHA reacted with glycerol and 1,4 butanediol. The distribution of pores computed from BJH desorption branch was also more uniform. FTIR indicated that there was no significant change in the chemical structure of RHA reacted with different depolymerizing agents. The residual C-H bands were found in FTIR spectra for all prepared mesoporous silicas. TGA thermograms confirmed the existence of organic residues (below 2 %wt), which might result from incomplete elimination even after calcination. This was found to be an important factor affecting the hydrophobic property of the reacted RHA. The hydrophobicity of RHA may be tailored by controlling depolymerizing agents and organic residues. Depolymerizing agents with longer carbon chains also favoured the hydrophobic characteristics.

Abstract: The effect of the magnetic properties of YBCO superconductors on the inductance of coil were studied in order to the dependence on temperature of effective penetration depth and the variation potential difference for damped oscillation in RLC series circuit. In this work, The samples of YBa2Cu3-xAgxO7- were prepared by solid state reaction in air at 950 ๐C for 24 hr. serves as the core of solenoids. The inductance of solenoids changes up with the increasing of temperature from boiling point of liquid nitrogen (77 K) to room temperature had been measured. Then we calculated to the effective penetration depth. We found that there were increase correspond with the increasing of temperature and the critical temperature decreased and then increased with the increase in Ag2O concentration of x = 0.1 and 0.2 , respectively. The variation potential difference for damped oscillation in RLC series circuit. We found that the decreasing of amplitude per cycle of the samples at superconducting state larger than those at normal state and phases shift in the damping oscillattion of RLC circuit at superconducting state are less than that at normal state, discussed as in inductance, the magnetic flux entering through the samples at superconducting state are less than that at normal state.

Abstract: Spray dried rice starch (SDRS ) (Era-Tab ®)was prepared by spray drying of rice starch at a suitable condition. Scanning electron microscope revealed that particle of SDRS was spherical and made up entirely agglomerates of rice starch grains. Tablet properties of SDRS were studied and compared with those of three commercially available direct compression fillers. Hardness, friability, and disintegration of the tablets were evaluated. It was found that SDRS was inferior to only one of them. Segregation tendency of direct compression formulation containing SDRS as a major component was tested. A blend of propranolol hydrochloride and SDRS was tableted on an rotary tablet press. Dissolution and drug content were evaluated. The results indicated that segregation did not occur over a two-hour period. To demonstrate the uniform distribution of low-dose drug, a mixture of SDRS and chlorpheniramine maleate were prepared at 4% of the drug. The tablets were assayed for the content uniformity and found to be excellent. Since direct compression process avoided the use of heat and moisture which were normally employed in wet granulation process, aspirin which was a heat and moisture sensitive drug was formulated with the use of SDRS. The tablets obtained were found to be satisfactory. Therefore, it was concluded that it could be employed successfully as a filler in direct compression tableting

Abstract: Pregelatinized rice starch (Era-Gel ® ) was prepared by physical modification. The degree of pregelatinization was controlled to an appropriate level. With the addition of small amount of pregelatinized rice starch , a slightly sticky, damped mass was obtained. Pregelatinized rice starch was tested for a potential use as a tablet filler or binder in wet granulation process. Two hydrochlorothiazide formulations were compared. One formulation comprised HCTZ and PRS; the powder mixture was damped with water. The other formulation contained HCTZ, lactose as filter, corn starch as binder and also as tablet disintegrant. In the later case, the powder mixture was damped with starch paste. Both granulations were compressed on an instrumented tablet press. The tablets were evaluated for their hardness, friability, disintegration, and also dissolution. The results indicated that both formulations were comparable in all aspects. It dissolution was found to exceed the USP requirement. It was demonstrated that three components, i.e. , lactose, corn starch paste, and disintegrant could be replaced with only one single material, PRS. It was also found that PRS could perform well in acetaminophen tablet formulation which was a high-dose drug and tended to cap; however, small amount of extra binder and disintegrant were needed. It could be seen that PRS had a great potential use in wet granulation process.

Abstract: Starch-colloidal silicon dioxide mixtures (Era-Tab SP® ) was prepared by co-spray drying and dry mixing methods and the flow ability and tablet properties of both methods were compared in particular with spray dried rice starch (SNR) alone. In co-spray drying, various percentages of rice starch and colloidal silicon dioxide blends were suspended in distilled water and subjected to spray dryer. The dry mixing method was obtained by blending of the colloidal silicon dioxide and spray dried rice starch at various percentages. It was found that co-spray drying of starch-colloidal silicon dioxide mixtures improved flow ability by reducing of the frictional forces between the granules greater than the dry mixing method. SEM micrographs presented the depositions of colloidal silicon dioxide on the surface of agglomerated starch granules obtained from both methods. The addition of colloidal silicon dioxide increased the tensile strength of the compressed tablet especially via the co-spray drying method by increasing the interaction of hydrogen bonding inside the tablet. Moreover, the co-spray drying method also reduced the friability and the disintegration time of the tablets better than the dry mixing method.

Abstract: Steady-shear rheological properties, including the consistency index from the power law, the yield stress and Casson plastic viscosity from the Casson’s model were employed in the study of retrogradation of native rice starch, octenyl succinate (OS) rice starch (NurtureCare® )and blends containing up to 80% OS rice starch. After cold storage at 4 oC for 24 h, presence of OS rice starch reduced retrogradation of rice starch mixtures as indicated by reduction of measured retrogradation parameters based on the three abovementioned rheological properties.

Abstract: Structural properties of hybrid nanocomposites based on TiO2 nanostructures and Copper phthalocyanine (CuPc) were investigated. The composites were prepared by mixing TiO2 nanoparticle (TNP) and nanotube (TNT) with CuPc suspension. The precipitated composites were obtained by centrifuged and dried processes. Structural properties of the composites were evaluated by mean of Raman Spectroscopy and X-ray Absorption Fine Structure (XAFS). The results implied that CuPc has interatomic distance of C atoms in the second shell are decreased when CuPc is in the hybrid composites.

Abstract: Zinc oxide powder was prepared by a chemical co-precipitation method. Zinc nitrate and ammonium hydroxide were used as the starting precursors. The white precipitated powder was formed after adding ammonium hydroxide until the pH of final solution was 7-9. The powder was filtered and dried at 100 °C for 24h. The phase of zinc oxide powder was studied by X-ray diffractometer (XRD). Hexagonal single phase of zinc oxide was obtained without calcination step. The morphology of zinc oxide powder was investigated by scanning electron microscope (SEM). The particle was irregular in shape and highly agglomerated with an average particle size of 0.1 µm. The chemical composition of zinc oxide powder was determined by energy dispersive X-ray spectrometer (EDXS). The elemental composition of zinc oxide showed the characteristic X-ray energy value as follows: zinc of Lα = 1.012 keV, Kα = 8.630 keV and Kβ = 9.570 keV and oxygen of Kα = 0.525 keV, respectively.

Abstract: Zirconia Toughened Alumina (ZTA) Nanocomposites were prepared using Nano sized Zirconia (ZrO2) powders doped with 3% mol of yttria (Y2O3) nanopowders. Diffusion of α-alumina (Al2O3) nanoparticles as well as yttria into the Zirconia lattice network drives monoclinic – tetragonal martensitic transformation. Zirconia toughened alumina (ZTA) composites containing different amount of partially stabilized Zirconia (PSZ) 5, 10, 15 and 20% mol, were prepared via wet mixing and axial pressing. After sintering at different temperatures,1450, 1550 and 1650 °C, phase change in the samples were monitored. X-ray diffraction patterns showed that at constant composition, tetragonal zirconia was increased by temperature increasing due to intensification of diffuse coefficient of alumina and yttria in the system. At constant temperature, remained monoclinic zirconia was increased with Zirconia content increasing.

Abstract: A Radio Frequency Inductively Couple Plasma Reactor (RFICP) was designed and set up for DLC deposition onto aluminum substrates using CH4-H2 admixture precursor gas. Plasma parameters of the discharge during the deposition process were measured using Langmuir probe technique. The structure and morphology of the DLC films were characterized by SEM and Raman spectroscopy. SEM images show granule morphology which yield smaller grain size with increasing of RF power. It was found that the structure and composition of DLC films are controlled by changes in the RF power. Raman spectrum of DLC films show two typpical modes of the graphite lattice labelled as ‘G’ and ‘D’ modes. The G peak position shift to higher wave number and the ratio of the peak intensity ID/IG increases with increasing RF power. DLC samples yield good ohmic characteristics with decreasing resistivity in films grown at higher RF power. Both electrical and structural characteristics indicated that the films contain more graphitic content of sp2 hybridization with increasing RF power in the plasma process.