Doty Dewi Risanti

Iron-aluminium-base alloys with strengthening Laves phase for structural applications at high temperatures

Fe-Al-Ta alloys with the ternary Laves phase Ta(Fe0.5+x, Al0.5-x)2 are studied experimentally with the objective of clarifying the effect of Laves phase precipitation and atomic ordering on the deformation characteristics of such Fe-Al-base alloys. The present study concentrates on the hardening effect of the Laves phase in ordered and disordered Fe-Al-Ta alloys with Al contents between 16 and 45 at.% showing the A2 disorder or the DO3 or B2 order. Ta has a low solubility in Fe-Al alloys which is beneficial for slowing down precipitate coarsening. Small amounts of Laves phase together with atomic ordering increase the yield stress and affect ductility in a complex way. The alloys with 1% Ta exhibit a high oxidation resistance. The continuing work aims at adjusting the Al and Ta content for an optimum relation of high-temperature strength and low-temperature ductility with maintaining a sufficient oxidation resistance.

Photoelectrochemical performance of DSSC with monodisperse and polydisperse ZnO SPs

Zinc oxide, ZnO, is one of oxide semiconductors being used in DSSC. ZnO is promising material for having fairly higher energy band gap and much higher bulk electron mobility than that of anatase TiO2, the most widely used semiconductor for DSSC photoelectrode. This study introduces the synthesis of ZnO by precipitation method. The synthesis involves ZnAc dihydrate and diethylene glycol (DEG) for the chemicals. Various size of ZnO spherical particles (SPs) are obtained in polydisperse and monodisperse particles. Monolayer and bilayer DSSCs are fabricated in sandwich structure and sensitized with N719 dye for 3 and 5 hours. Monolayer DSSC using monodisperse particles (422 nm) is able to generate highest conversion efficiency of 0.569% (Voc = 541.3 mV, Jsc = 1.92 mA/cm2, and fill factor of 54.78%). Bilayer DSSC, i.e. combined 422 - 185 nm ZnO layer, can optimize the photocurrent action spectra in UV regime leading to high conversion efficiency of 0.568 (Voc = 568.2 mV, Jsc = 2.22 mA/cm2, and fill factor of 4...

Modeling and experiment of dye-sensitized solar cell with vertically aligned ZnO nanorods through chemical bath deposition

A theoretical model based on electron diffusion differential equation and Schottky barrier model was developed to determine the current–voltage characteristics of DSSC. To verify the model DSSC with ZnO nanorods photoelectrode which was chemically bath deposited onto the TCO was fabricated. According to modeling results, increasing of recombination current density J at these interfaces results in a decrease in Schottky barrier height φb and therefore improves the photovoltage under the open-circuit condition. It is found that the open-circuit voltage remains constant when the TCO/ZnO Schottky barrier height was varied in the range of 0.45 – 0.6 eV. This theoretical model consistents with the experimental result in which the fabricated DSSCs can produce conversion efficiency in the range of 0.98 – 1.16%. The trend in photovoltage calculated in the theoretical model basically agrees with the experimental result, although the calculated photocurrent is somewhat over estimated compared to the experimental results. The model presents that the ideality factor for ZnO nanorods, which also contributes to the enhancement of photovoltage, increases in the range of 2.75 – 3.0 as the annealing temperature is increased in the experiment.

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.

Physical properties characterization of Porong Sidoarjo mud and its potentials as CO gas adsorbent materials

Sidoarjo mudflow is a disaster that causes huge loss for more than six years. In order to find its application earlier study showed that after calcined at various temperatures and leached in HCl and NaOH solution, the mud can be used as adsorbent materials. The results reveal that only samples activated in acid condition have potential for being used as adsorbent. The BET isotherm curve obtained are categorized as type IV indicating the mud can be classified as mesoporous materials with pore diameter of 2 nm and surface area between 32 and 116.953 m2/g depending on the calcination temperatures. These are in line with fly ash being used as CO adsorbent, whose BET isotherm curve and surface area are similar to Porong Sidoarjo mud. It is known that fly ash can be used as adsorbent for reducing carbon monoxides (CO) emissions of vehicles with maximum absorption efficiency 19.78%.

Quasi-Solid State DSSC Performance Enhancement by Bilayer Mesoporous TiO2 Structure Modification

Quasi-solid state dye-sensitized solar cells (DSSC) having bilayer structure were made by using nanocrystalline anatase-rutile TiO2 to enhance the photovoltaic performance. The bilayer structures were coated to FTO glass using doctor blade technique with total active area of 0.4 cm2. Cyanidin dye extracted from mangosteen pericarp was used as photosensitizer. Bilayer anatase-anatase was formed with surface area of 99.9 m2/g and pore volume of 0.23 cc/g while anatase-rutile structure has surface area of 103.5 m2/g and pore volume of 0.21 cc/g. Overall energy conversion efficiencies under illumination of 10 mW/cm2 of 0.461% and 0.1365% were achieved for DSSC employing anatase-anatase and anatase-rutile TiO2 structure, respectively. Both efficiencies were higher than that of monolayer anatase and rutile TiO2 structure whose efficiencies in the range of 0.02% to 0.037%. The photocurrent action spectra of bilayer structures performed high efficiency spectrum in the wavelength range of 420 480 nm owing to cyanidin effect of dye.

The Mechanical Properties of AA2024 as Function of the Interrupted Ageing Conditions

A comprehensive and systematic study using hardness, tensile test and Kahn tear test was undertaken to follow property development during the recently promoted interrupted ageing treatment. In contrast to the reported claims hardness remains lower than that of single stage heat treatment. Toughness does not improve substantially and deteriorates further as re-ageing time is prolonged. For most cases, the effect of interrupted ageing could not produce a simultaneous improvement in mechanical properties. TEM observations indicate the size and distribution co-existing S” and S phases upon re-ageing depend on interrupted condition.

Towards better light harvesting capability for DSSC (dye sensitized solar cells) through addition of Au@SiO2 core-shell nanoparticles

The Au nanoparticles as core can increase the light harvesting due to the strong near-field effect LSPR (Localized Surface Plasmon Resonance), effectively minimized the electron recombination process and also can improve the optical absorption of the dye sensitized. Au@SiO2 core-shell nanoparticles were prepared using SiO2 extracted from Sidoarjo mud volcano. In this work investigated the influence of pH solution and silica shell volume fraction in Au@SiO2 nanoparticles core-shell structure on DSSC loaded with Ru-based dye. From XRD characterization it was found that core-shell contains SiO2, Au, γAl2O3 and traces NaCl. UV-Vis absorption spectra of core–shell showed the position of the surface plasmon AuNP band in the range of 500–600 nm. The Au@SiO2 core-shell with volume fraction of 30ml silica has the highest peak absorbance. The enhanced light absorption is primarily attributed to the LSPR effect of the Au core. Our results on incident photon-to-current conversion efficiency indicates that the presence of SiO2 depending on its volume fraction tends to shift to longer wavelength.The Au nanoparticles as core can increase the light harvesting due to the strong near-field effect LSPR (Localized Surface Plasmon Resonance), effectively minimized the electron recombination process and also can improve the optical absorption of the dye sensitized. Au@SiO2 core-shell nanoparticles were prepared using SiO2 extracted from Sidoarjo mud volcano. In this work investigated the influence of pH solution and silica shell volume fraction in Au@SiO2 nanoparticles core-shell structure on DSSC loaded with Ru-based dye. From XRD characterization it was found that core-shell contains SiO2, Au, γAl2O3 and traces NaCl. UV-Vis absorption spectra of core–shell showed the position of the surface plasmon AuNP band in the range of 500–600 nm. The Au@SiO2 core-shell with volume fraction of 30ml silica has the highest peak absorbance. The enhanced light absorption is primarily attributed to the LSPR effect of the Au core. Our results on incident photon-to-current conversion efficiency indicates that the presenc...

Gold Nanoparticles and Silicate Microsheet Modified Photoanode for Dye Sensitized Solar Cells

Gold nanoparticles and silicate microsheet modified TiO2 photoanode with various decoration amount of gold solution have been successfully synthesized. The gold nanoparticles were prepared using Turkevich method and silicate microsheet was using silica gel. The sample were characterized by XRD, SEM, and FTIR. The DSSC performance were evaluated by photocurrent-voltage measurement. The results show the increasing decoration amount of gold nanoparticles, increase the intensity of diffraction peaks. The gold nanoparticles size is 20-35 nm. Comparing with pristine TiO2 photoanode, the efficiency of DSSC using modified photoanode increase up to 31%.

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.