Composite materials based on rice straw and natural rubber for thermal insulation applications

Thermal properties of composites fabricated with coalescence of two low thermal conducting materials, rice straw and natural latex were investigated. Composites constituting various weight content of oven-dried blended rice straw mixed with a constant volume of natural latex were fabricated with a surface area of 31 cm2 and their thermal properties were compared by pressurizing under a force of 5 tons. Hot Disk Thermal Constants Analyzer Transient Plane Source (TPS) 500S was used to measure the thermal properties such as thermal conductivity, volumetric specific heat capacity, and thermal diffusivity of the aforementioned composites. The lowest thermal conductivity was achieved for both the unpressurized and pressurized composites with 25% of the rice straw’s weight content, which was recorded as 0.0636 and 0.1526 Wm-1K-1 respectively. High Specific heat capacity and less thermal diffusivity were also seen in the pressurized samples with 25% of rice straw, whereas this behaviour was the opposite in the unpressurized sample. The effect of the applied pressure on the thermal properties of the composite is also studied and it was observed that the thermal conductivity increases up to 8 tons on 31 cm2 in the composite with increasing pressure and then decreases while it continues to increase in the sample made of rice straw alone. Since high specific heat and low thermal diffusivity are the desired features of a thermally insulating material other than the low thermal conductivity, this economical and eco-friendly composite pressurized up to a certain limit could be used by further processing with preservatives toward efficient energy management as a good material for thermal insulation of building applications

Synthesis of Triphenylamine Trisazo Dye and Study of its Uses in Dye Sensitized Solar Cells

A new triazo dye was synthesized from tri(p-aminophenyl)amine and 2 hydroxy-3-napthoic acid and explored the possibilities of its uses in dye sensitized solar cells for the first time. The photocells were able to generate reasonably high photocurrent in the presence of the electron donating ionic liquids in the electrolyte composed of redox couple I3- /I-. Cells fabricated by sensitizing TiO2 generated a short-circuit photocurrent of ~ 3.5 mA cm-2, an open-circuit photovoltage of ~ 500 mV with a total power conversion efficiency of ~ 1 % under simulated full sunlight of 100 mW cm-2 (Air Mass 1.5). 1

Polymethylmethacrylate (PMMA) based quasi-solid electrolyte with binary iodide salt for efficiency enhancement in TiO2 based dye sensitized solar cells

Enhancement of efficiency by using iodide mixture (Pr4NI and I(1), instead of a single iodide salt, in N719 dye-sensitized solar cells with a polymethylmethacrylate (PMMA) based gel electrolyte is investigated. The salt ratio is varied to optimize efficiency. With 100 wt.% KI and 100 wt.% (Pr4NI) efficiencies under AM 1.5 illumination are 3.39% and 3.21%, while 22.2:77.8 wt.% ratio KI:Pr4NI shows the highest efficiency of 3.99%. This is an efficiency enhancement of 18%. Variation of efficiency with salt composition appears to correspond to the change in short circuit photocurrent density (J(sc)) and the iodide ion conductivity

Efficiency enhancement in dye sensitized solar cells based on PAN gel electrolyte with Pr4NI + MgI2 binary iodide salt mixture

The effect of using a binary iodide salt mixture in N719 dye-sensitized TiO2 solar cells (DSSCs) is investigated. The cells use tetrapropylammonium iodide (Pr4NI) and magnesium iodide (MgI2) in a plasticized polyacrylonitrile gel in glass/FTO/nano-porous TiO2/gel, I-2/Pt/FTO/glass solar cell structure. The salt composition in the gel electrolyte is varied to optimize the efficiency of DSSCs. The DSSCs with MgI2 or Pr4NI as the only iodide salt showed the efficiencies 2.56 and 4.16 %, respectively, under AM 1.5 (100 mW cm(-2)) illumination while the DSSC with mixed cations with 18.4:81.6 MgI2:Pr4NI molar ratio shows the highest efficiency of 5.18 %. Thus the efficiency enhancement, relative to the high efficiency end member is about 25 %. DC polarization measurements establish the predominantly ionic behavior of the electrolytes, and show that the variation of efficiency with salt composition correlates with the change in short circuit photocurrent density (J (sc)), which appears to be governed by the iodide ion conductivity. It is also found that J (sc) correlates with the iodide ion transference number estimated from DC polarization data taken with non-blocking iodine electrodes. This study suggests that binary iodide mixtures may be used to obtain efficiency enhancement in different types of DSSCs based on polymeric, gel, or solvent electrolytes

Efficiency enhancement by mixed cation effect in dye-sensitized solar cells with PAN based gel polymer electrolyte

Dye-sensitized solar cells based on nano-porous TiO2 photo-anode and quasi-solid polymer (or gel) electrolytes are emerging as low cost alternatives to conventional inorganic photovoltaic devices. Although many attempts have been made in order to improve the relatively low power conversion efficiencies of these solar cells, to our knowledge there are very few reports aimed at using a binary system of two different iodide salts toward efficiency enhancement in these cells. In this paper we report for the first time in detail, the effect of using a binary iodide salt mixture with different size cations on the efficiency enhancement in dye sensitized solar cells with polyacrylonitrile (PAN) based gel polymer electrolyte and suggest a possible mechanism for this enhancement, based on short circuit photocurrent which is directly related to the iodide ion concentration [I-]. The gel electrolyte was made of PAN, ethelene carbonate (EC), Propylene carbonate (PC), salt mixture and I-2. The binary iodide salt mixture consists of potassium iodide (KI) and Tetra propyl ammonium iodide (Pr4NI). Although the gel electrolyte with 100% (w/w) KI exhibited the highest overall ionic conductivity at room temperature, it showed the lowest iodide ion (I-) contribution to conductivity. On the other hand, the electrolyte with 100% (w/w) Pr4NI exhibited the lowest overall ionic conductivity but had the highest iodide ion(I-) contribution. The dye-sensitized solar cells of configuration Glass/FTO/TiO2/N-719 Dye/electrolyte/Pt/FTO/glass were fabricated using the gel electrolytes of different salt ratios and with nanoporous TiO2 electrode sensitized with Ruthenium dye (N719). With identical electrolyte compositions, the solar cell with 100% (w/w) KI showed an efficiency of 4.98% and the cell with 100% (w/w) Pr4NI showed an efficiency of 4.47%. However, the cell with the mixed iodide system, 16.6% (w/w) KI + 83.4%(w/w) Pr4NI showed the highest efficiency of 5.36% with maximum short circuit current density (J(SC)) of 13.79 mA cm(-2), open circuit voltage (V-OC) of 679.10 mV and a fill factor of 57.25%. The variation of efficiency (eta) with iodide ion concentration [I-] follows the same trend as the J(SC) which appears to be governed by the iodide ion conductivity of the gel electrolyte. The dependence of the short circuit photocurrent and the open circuit photovoltage on the cation type generally agrees with reported data for related systems. However, the occurrence of a maximum in the solar cell efficiency and short circuit photocurrent at 16.6% (w/w)10 + 83.4% (w/w) Pr4NI salt composition is an important finding. The efficiency enhancement of about 8% achieved by employing the binary iodide mixture in the gel electrolyte instead of a single iodide salt, could be utilized for achieving efficiency enhancement in many dye sensitized solar cell systems based on polymeric, gel or solvent electrolytes

A novel multilayered photoelectrode with nitrogen doped TiO2 for efficiency enhancement in dye sensitized solar cells

Nitrogen doped TiO2 powder samples were synthesized by a modified wet chemical method using aqueous ammonia and nitrogen gas purged on titanium tetra isopropoxide (TTIP). Photolectrodes with different combinations of layers of nitrogen ? doped TiO2, undoped TiO2 and Degussa P25 TiO2 powders were used in dye sensitized solar cells (DSSCs). The highest conversion efficiency of 8.00% was achieved by the cells fabricated with compact layer/P25/N-doped TiO2 multilayer photoelectrode. This is an impressive enhancement in efficiency close to 89% with respect to a similar multilayer electrode made with undoped TiO2 which showed a conversion efficiency of 4.22%. The enhancement in the efficiency appears to be due to the increased photocurrent density of the DSSCs resulting mainly from energy band gap narrowing due to N-doping with some contribution from increased dye uptake by the novel multilayer electrode. These results have been substantiated by the reduced charge transfer resistance obtained from Electrochemical Impedance Spectra and the enhanced IPCE spectra of the DSSCs with N-doped TiO2 based multilayer electrode

Effect of alumina filler on spherulite growth and ionic conductivity of PEO9(LiClO4) solid polymer electrolyte

The effect of incorporation of alumina on conductivity and in situ growth of spherulites in (PEO)(9)LiClO4 solid polymer electrolyte was studied using polarized microscopy, impedance and infrared spectroscopy. Fourfold enhancement in ionic conductivity correlated with increase in the amorphous nature of the polymer electrolyte was observed with the addition of 15 wt% of alumina having 5.5 nm pore size. The addition of 5 wt% of alumina with pore size <10 mu m, increased the ionic conductivity by nearly 3%. Filler particles may act as nuclei for the spherulites, while preventing the recrystallization tendency of the polymer and hence increase its conductivity

Innovative approaches to teaching engineering drawing at tertiary institutions

This paper arises from our concern for the level of teaching of engineering drawing at tertiary institutions in Australia. Little attention is paid to teaching hand drawing and tolerancing. Teaching of engineering drawing is usually limited to computer-aided design (CAD) using AutoCAD or one of the solid-modelling packages. As a result, many engineering graduates have diffi culties in understanding how views are produced in different projection angles, are unable to produce engineering drawings of professional quality, or read engineering drawings, and unable to select fits and limits or surface roughness. In the Faculty of Built Environment and Engineering at the Queensland University of Technology new approaches to teaching engineering drawing have been introduced. In this paper the results of these innovative approaches are examined through surveys and other research methods