Photoexcitation dynamics in polythiophene/fullerene blends for photovoltaic applications

We used the transient and steady state photomodulation spectroscopies for studying the photoexcitations dynamics in blends of regio-regular poly(3-hexylthiophene) (RR-P3HT) and fullerene in a broad spectral range from 0.13 to 2.25 eV. We found that both localized polarons and singlet excitons are instantaneously photogenerated in the blends. However the photogeneration process of delocalized polarons which contribute to the photocurrent proceeds in two steps: first, within a couple of ps the excitons generated in the polymer domains populate the charge transfer complex states at the RR-P3HT/fullerene interfaces; this is followed by the charge transfer ionization into delocalized charge polarons in the polymer and fullerene constituents within ～20 ps. In contrast, the localized polaron dynamics are unrelated with the excitons and delocalized polarons dynamics. We also report on the occurrence of ultrafast quantum interference anti-resonances between photoinduced infrared-active vibrations and the delocalized polaron band in the blends, which shows the delocalization character of the photogenerated charges that contribute to the photocurrent.     

Modeling of noise for p-channel DG-FinFETs

The noise performance of p-channel Double Gate FinFETs has been studied with varying structural parameters. The effects of mobility degradation due to velocity saturation, carrier heating and channel length modulation have been taken into consideration for an accurate modeling of noise. The dependence of mobility fluctuations on the inversion carrier density has been incorporated. This has been validated by the experimental results. The noise behavior of p-channel device has been compared to that of a corresponding n-channel device. It has been observed that noise in p-channel device is comparatively higher due to higher number of oxide-trap density in it. Further, it has been noted that with the same trap density in both p-channel and n-channel device, the flicker noise in the p-channel device is lower than that of the corresponding n-channel device.     

Review on Mixing Characteristics in Solid‐Liquid and Solid‐Liquid‐Gas Reactor Vessels

Mechanically agitated reactors with single and multiple impeller systems are used in the industry for the various three‐phase mixing processes such as crystallization, fermentation, and hydrogenation, etc. The paper reviews the experimental work reported in the literature along with different techniques used for the measurement of the specific quantities such as minimum or critical impeller speed for solid suspension. The work critically surveys the literature and makes specific recommendations for the use of appropriate correlations and conditions to be used for the success of such equipment. This assessment will put all the relevant literature on a common footing and will help to validate work reported earlier.     

Performance of an anion exchange membrane in association with cathodic parameters in a dual chamber microbial fuel cell

Performance of two-chambered microbial fuel cells (MFCs) using anion exchange membrane (AEM) was evaluated under batch mode with Shewanella putrefaciens in Luria broth. Maximum voltage and power density using Nafion and Ralex AEM were 0.676 V and 0.729 V and 39.2 ± 7.39 mW/m² and 57.8 ± 5.509 mW/m² respectively. Cathodic half cell potential was monitored along with cathodic pH and the results revealed that low power density was achieved in case of Nafion as compared to Ralex AEM mainly due to pH imbalance associated voltage losses using small external resistance of the same. Metabolite loss in AEM was found at higher current density which limits the Coulombic efficiency and power generation. A three parameters optimization showed that surface area of cathode had significant effect on the power generation. Effect of anode surface area, dissolve oxygen (DO) in catholyte and electrode spacing on power production were evaluated using AEM membrane.     

Compounding of glass fiber-reinforced polypropylene and investigation of its mechanical properties under simple and complex loading

Polypropylene is one of the important thermoplastics that has been reinforced with glass fibers to give a reasonably good engineering plastic. Because of its inert nature, it does not easily adhere to the glass surface and hence some improvement in mechanical properties. In the present study a vinyltriethoxysilane coupling agent in polymeric form has been tried and seen to improve the properties. Tests have been carried out at (a) constant strain rate (in the Instron testing machine), and (b)constant stress rate (water loading on a biaxial testing machine). Under constant strain rate only tensile properties have been studied while under constant stress rate, the tensile, torsional and combined tensile-torsional tests have been carried out. In each of the above cases, a considerable improvement in elastic modulus has been observed. The Tensile strength is improved to the extent of about 25 percent. There is only a slight improvement in torsional strength. Different fiber volume contents were used and their effect studied on modulus and strength. The mechanical data for reinforced-polypropylene samples have been discussed in terms of the fiber-length distribution in the composite. Detailed analysis of tensile data suggests that at low strains, when the critical length is relatively low, the fibers contribute to a high modulus. With increasing strain the critical length increases and the load carrying capacity of the fibers is reduced. Consequently the gain in strength is relatively less. The effect of fiber length distribution in torsion and combined tension-torsion tests would be expected to be similar and the results seem to confirm this.     

Molding and torsional testing of tubular specimens of glass fiber-reinforced polypropylene

This paper describes a torsion pendulum based on the free vibration method and designed for studies on tubular samples. The design and fabrication of the injection mold used for molding the tubular specimens is also described. Tubular specimens were injection molded form polypropylene and glass fiber-reinforced polypropylene having different glass fiber contents. The sample, which is enclosed in an insulated chamber, can be cooled with the help of liquid nitrogen and heated electrically. The damped oscillations were recorded on a moving chart paper using a lamp and a photodyne between −40 to 100°C. The results indicate that both storage modulus and the logarithmic decrement are affected by the glass fiber and its content. The reinforcing effect of glass fiber and the suppression of viscoelastic effects are briefly discussed.