Proton Conductivity and FTIR Studies of Methanesulfonic Acid (MSA) Incorporated Polyacrylamide based Composite Solid Polymer Electrolyte.

A new class of Composite Solid Polymer Electrolyte Membrane (CSPE) of Polyacrylamide (PAAm) with Methanesulfonic acid (MSA) was synthesized. The composite membranes were thoroughly characterized by FTIR and proton conducting performance. The highest proton conductivity of 1.17 x 10-6Scm-1 was observed at room temperature with the loading of 5M of MSA into the polymer matrix. FTIR spectroscopy was used to study the mechanism involved in the protons transfer in the membranes by referring the characteristic shifts of the absorbance bands of C=O and N-H2. Thermal parameters such as the glass transition temperature (Tg) and the melting point (Tm) of the polymer membrane with the highest proton conductivity were measured by TGA and DSC. The morphology of the PAAm-5M MSA was observed by FESEM. The valued merits on the proton conductivity, thermal stability and easy synthesis promise the new membranes to be good alternative as CSPE for electrochemical devices

Thermo-mechanical properties prediction of Ni-reinforced Al2_2O3_3 composites using micro-mechanics based representative volume elements

For effective cutting tool inserts that absorb thermal shock at varying temperature gradients, improved thermal conductivity and toughness are required. In addition, parameters such as the coefficient of thermal expansion must be kept within a reasonable range. This work presents a novel material design framework based on a multi-scale modeling approach that proposes nickel (Ni)-reinforced alumina (Al$_2$O$_3$) composites to tailor the mechanical and thermal properties required for ceramic cutting tools by considering numerous composite parameters. The representative volume elements (RVEs) are generated using the DREAM.3D software program and the output is imported into a commercial finite element software ABAQUS. The RVEs which contain multiple Ni particles with varying porosity and volume fractions are used to predict the effective thermal and mechanical properties using the computational homogenization methods under appropriate boundary conditions (BCs). The RVE framework is validated by the sintering of Al$_2$O$_3$-Ni composites in various compositions. The predicted numerical results agree well with the measured thermal and structural properties. The properties predicted by the numerical model are comparable with those obtained using the rules of mixtures and SwiftComp, as well as the Fast Fourier Transform (FFT) based computational homogenization method. The results show that the ABAQUS, SwiftComp and FFT results are fairly close to each other. The effects of porosity and Ni volume fraction on the mechanical and thermal properties are also investigated. It is observed that the mechanical properties and thermal conductivities decrease with the porosity, while the thermal expansion remains unaffected. The proposed integrated modeling and empirical approach could facilitate the development of unique Al$_2$O$_3$-metal composites with the desired thermal and mechanical properties for ceramic cutting inserts

Surface modification of mixed-phase hydrogenated TiO2 and corresponding photocatalytic response

Preparation of highly photo-activated TiO2 is achievable by hydrogenation at constant temperature and pressure, with controlled hydrogenation duration. The formation of surface disorders and Ti3+ is responsible for the color change from white unhydrogenated TiO2 to bluish-gray hydrogenated TiO2. This color change, together with increased oxygen vacancies and Ti3+ enhanced the solar light absorption from UV to infra-red region. Interestingly, no band gap narrowing is observed. The photocatalytic activity in the UV and visible region is controlled by Ti3+ and oxygen vacancies respectively. Both Ti3+ and oxygen vacancies increases the electron density on the catalyst surface thus facilitates •OH radicals formation. The lifespan of surface photo-excited electrons and holes are also sustained thus prevents charge carrier recombination. However, excessive amount of oxygen vacancies deteriorates the photocatalytic activity as it serves as charge traps. Hydrogenation of TiO2 also promotes the growth of active {0 0 1} facets and facilitates the photocatalytic activity by higher concentration of surface OH radicals. However, the growth of {0 0 1} facets is small and insignificant toward the overall photo-kinetics. This work also shows that larger role is played by Ti3+ and oxygen vacancies rather than the surface disorders created during the hydrogenation process. It also demonstrates the ability of hydrogenated TiO2 to absorb wider range of photons even though at a similar band gap as unhydrogenated TiO2. In addition, the photocatalytic activity is shown to be decreased for extended hydrogenation duration due to excessive catalyst growth and loss in the total surface area. Thus, a balance in the physico-chemical properties of hydrogenated TiO2 is crucial to enhance the photocatalytic activity by simply controlling the hydrogenation duration

Effective role of trifluoroacetic acid (TFA) to enhance the photocatalytic activity of F-doped TiO2 prepared by modified sol-gel method

Highly photoactive mesoporous F-doped TiO2 with improved physico-chemical characteristics is achieved using modified sol-gel method. The usage of trifluoroacetic as fluorine precursor significantly modifies the morphology, size, pore shape, crystal phase, crystal structure, surface chemical state and to a lesser extent, {1 0 1} and {0 0 1} facets. The accessibility of fluoride ions on Tisingle bondOsingle bondTi polymer chains during crystal growth during the sol-gel process remarkably influences the properties of catalyst. To the best of our knowledge, preparation of F-doped TiO2 using modified sol-gel and trifluoroacetic acid are limited, and still not enough. Thus this work provides additional insight by using an approach which is less hazardous, less costly and practical for large scale agile development in the photocatalysis industry

Conductivity studies of grafted natural rubber and ionic liquid electrolyte systems

Ionic liquids containing the 1 -butyl- 1-methylpyrrolidinium ([C 4mPyrr]+) cation and bis(trifluoromethanesulfonyl)imide ([NTf 2]") anion have been synthesized and incorporated in 49% PMMA grafted natural rubber together with lithium salts to obtain solid polymer electrolytes (SPEs). The resultant SPEs obtained, are freestanding, flexible film and translucent and show conductivity over a wide range of 10 -3-10 -5 S cm -1. Polymer electrolytes containing 80% of (MG49:LiCF 3S0 3) and 20% of [C 4mPyrr] [NTf 2] showed the highest conductivity of 2.11 x 10 -3 S cm -1 at room temperature. The examination of the ion- polymer interactions and ionic conductivity are discussed and investigated by FT-IR and Electrochemical Impedance Spectroscopy (EIS) respectively

Controlled potential electrodeposition and characterization of ZNTE thin films on indium tin oxides

Electrodeposition of ZnTe thin films by controlled potential method from aqueous solutions on ITO were done to investigate characteristics suitable as a window material in solar cells technology. The influence of bath temperature and deposition potential towards the Zn:Se ratio and the crystallinity are discussed. The electrodeposited films were investigated by using X-Ray Diffraction, Energy Dispersive Analysis of x-ray, Scanning Electron Microscopy and UV spectroscopy. Optical measurements were done on these samples and show a good agreement with reported results

Structure and optical characterization of electrodeposited zinc selenide thin films

Polycrystalline thin films of cubic zinc selenide semiconductor have been electrochemically deposited on conducting substrates of indium tin oxide, ITO glass. Initial investigation with voltammetry was done and the influence of deposition potential and of bath temperature on the films crystallinity is discussed. At room temperature, amorphous films were obtained and at elevated bath temperatures between 55 oC and 75 oC, films were crystallined. The best deposition voltage obtained was -0.95 V vs. Ag /AgCl while at lower deposition potentials, the films do not form well. Energy Dispersive Analysis and X-Ray spectrum indicate that the films deposited at 65 oC and -0.95 V vs. Ag/AgCl have nearly stoichiometric Zn: Se ratio. Energy band gap and refractive index are in agreement with reported results

Controlled nitrogen insertion in titanium dioxide for optimal photocatalytic degradation of atrazine

Introducing defects into the intrinsic TiO2 structural framework with nitrogen enhanced the photocatalytic response towards the degradation of atrazine, as compared to undoped TiO2. Both catalysts, which were prepared in an analogous manner, demonstrated high crystallinity and anatase phase dominant with well defined {101} facets, which serves as a pioneer platform for good photocatalytic activity. The introduction of nitrogen increased the stability of the crystal structure which leads to the formation of pure active anatase phase. Although the optical response was shifted towards the visible region, initiated by the formation of new absorption defects and interstate energy levels, the chemical state of nitrogen in the doped TiO2 controls the overall catalyst photoreactivity. In this study, it was found that the surface area and degree of band gap reduction played a lesser role for photocatalysis enhancement, although they partly contributed, than the concentration of surface charge traps and the type of structural framework formed during nitrogen incorporation. The enhancement in the photocatalytic degradation of atrazine clearly was influenced by the loading and nature of the nitrogen dopant, which in turn, governed the types of chemical and optical properties of the final catalyst product