Dyah Sawitri

Utilization of Coal Fly Ash as CO Gas Adsorbent

The radionuclide of uranium (U) is major radionuclide contained in the long life of high level radioactive liquid waste (HLLW) generated from reprocessing of spent nuclear fuel. The radioactive waste have to be treated to ready for long term disposal. Separation of the U at high efficiencies greatly lowers the volume of the long life alpha radioactive waste to be disposed and decreases the hazard level of the waste. The technology assessment of selective separation of U was carriedout as alternative and strategy for HLLW management in the future. The selective separation technology of U from fission products at very high efficiencies was developed by the extraction process using TBP-kerosene solvent and increasing the separation by exposure of nitrogen (N2) laser radiation at wavelength 337.1 nm. In the extraction process for simulation waste containing U and Zr in 5 M HNO3 (Zr as one of fission product which difficult to be separated from U) using 30 % TBP-kerosene solvent and by exposure of nitrogen laser radiation shows that increasing of distribution coefficient of U (Kd U) can obtains 135 % and increasing of separation factor of U and Zr (SF(U/Zr)) is 189 %. The increasing of Kd U using N2 laser higher than using CO2 laser (at the wave-number 944 cm-1 ) which increase of Kd U only 100 %. In Indonesia, assessment for adaptation of the separation technology by extraction for separation of U process using 30 % TBP-kerosene solvent should be carried-out as alternative for treatment the HLLW generated from 99Mo radioisotope production and from post irradiation examination of nuclear fuel.

The Effect of Paste Preparation and Annealing Temperature of ZnO Photoelectrode to Dye-Sensitized Solar Cells (DSSC) Performance

Dye-sensitized Solar Cells (DSSCs) have been successfully fabricated by using ZnO nanoparticles (NPs). The ZnO photoelectrode was prepared by using pastes solved in water-based and ethanol-based solvent. The ZnO NPs was synthesized by copresipitation method, prepared by reaction from Zinc Acetate with diethylene glycol (DEG). The obtained ZnO NPs has 13.93 nm particle diameter. Scanning Electron Microscopy (SEM) showed that ZnO NPs from monodisperse spherical aggregate with particle diameter of approximately 300nm. The band gap was found of 3.29eV. Variations of annealing temperature were carried out in photo-electrode fabrication. This work employs extracts from mangosteen pericarp as natural dye for fabrication of DSSCs. DSSCs were fabricated in sandwich structure with redox couple electrolyte I3-/I- and Pt-catalyst counter electrode. The best efficiency of 0.11% (Voc = 232.4 mV, Jsc = 111.6 µA/cm2, FF = 61.41 %) was obtained for DSSCs using ZnO photo-electrode prepared by ethanol-based paste and 200°C of annealing temperature.

The Effective Mixture of Anatase–Rutile Nanoparticles as Dye-Sensitized Solar Cell (DSSC) Using Natural Dye of Garcinia mangostana and Rhoeo spathacea Extract

A synergistic effect between anatase and rutile TiO2 is known to be able to improve light harvesting and the overall solar conversion efficiency. Dye-sensitized solar cell (DSSC) was fabricated using the mixture of anatase–rutile phase of TiO2 nanoparticles prepared through co-precipitation method with TiCl3 precursors. The particle’s sizes were 30 nm for anatase and 44.9 nm for rutile as characterized by using XRD (X-ray diffraction). The natural dyes employed were Garcinia mangostana pericarp extract and Rhoeo spathacea extract. The two selected dyes were used because of their abundant availability and good performance for being used as photosensitizer as indicated by their absorbance wavelength of 392.5 nm for G. mangostana extract and 432 and 658 nm for R. spathacea. Both dyes contain anthocyanin pigment, which is a known visible-light trapper that undergoes charge excitation, and upon complexation with a metal oxide semiconductor like TiO2, a charge-transfer process occurs. Our results show that the best performance of DSSC having anatase/rutile ratio of 90:10 (η = 0.076%) and (η = 0.063%) was obtained for samples sensitized with G. mangostana extract and R. spathacea extract, respectively. This ratio has the largest surface area and smallest particle size. The synergistic effect of the two phases is due to the ease of electron migration from rutile to anatase conduction band and larger surface area allowing more dye being able to be absorbed.

Co-Sensitized Natural Dyes Potentially Used to Enhance Light Harvesting Capability

We present the photoelectrochemical properties of dye-sensitized solar cells using natural pigments containing anthocyanins, betalains, and caroteins. The dyes were adsorbed by a photoanode that was fabricated from nanocrystalline TiO2 on transparent conductive glass. TiO2 comprises of 100% anatase and 90:10 anatase:rutile fraction. The dyes extracted from mangosteen pericarp, Musa aromatica pericarp, Celosia cristata flower and red beet root were characterized through UV-vis and IPCE. The effectiveness of the dyes was explained through photocurrent as a function of incident light power. It was found that the cocktail and multilayered dyes comprised of anthocyanins and caroteins is beneficial to obtain high photocurrent, whereas betalains is not recommended to be applied on untreated TiO2. Due to the bandgap properties of rutile and anatase, the presence of 10% rutile in TiO2 is favourable to further enhance the electron transport.

Effects of nano anatase-rutile TiO2 volume fraction with natural dye containing anthocyanin on the dye sensitized solar cell performance

Since its first development, efforts to improve efficiency of Dye Sensitized Solar Cell (DSSC) are continuously carried out, either through selection of dye materials, the type of semiconductor, counter electrode design or the sandwiched structure. It is widely known that anatase and rutile are phases of TiO2 that often being used for fabrication of DSSC. Rutile is thermodynamically more stable phase having band-gap suitable for absorption of sunlight spectrum. On the other hand, anatase has higher electrical conductivity, capability to adsorp dye as well as higher electron diffusion coefficient than those of rutile. Present research uses mangosteen pericarp and Rhoeo spathacea extracted in ethanol as natural dye containing anthocyanin. These dyes were characterized by using UV-Vis and FTIR, showing that the absorption maxima peaks obtained at 389 nm and 413 nm, for mangosteen and Rhoeo spathacea, respectively. The nano TiO2 was prepared by means of co-precipitation method. The particle size were 9-11 nm ...

The rule of carrier gas flow rate to Li + diffusivity of LiFePo 4 particles as lithium battery application

The effect carrier gas flow rate to particles characteristic was studied experimentally and numerically. Experimental investigation was carried out using flame spray pyrolysis method. LPG and free air were used as fuel and oxidizer, respectively. LiOH, (NH₄)₂HPO₄ and FePO₄.7H₂O were used as anorganic precursor. Numerical method was studied using ANSYS FLUENT 14.5 with finite volume technique. Annealing process was followed to increase the particles crystallinity. The results indicated that increasing the carrier gas flow rate caused decreasing the flame temperature. The crystallinity of particles increased proportional to flame temperature rising. Scanning Electrostatic Microscopy (SEM) revealed that the particles have sphere morphology. The particle size was decreased by increasing carrier gas flow rate. Fourier Transform Infrared (FTIR) showed the PO₄ functional group. Increasing carrier gas flow rate tend to enhance the transmittance intensity. The diffusivity coefficient obtained for carrier gas flow rate 1, 2 and 3 liter/min were 2.56 × 10^-9, 1.11 × 10^-9 and 9.26 × 10^-11cm²s^-1 respectively.