Development of Elastomeric Hybrid Composite Based on Synthesised Manosilica and Short Nylon Fiber

Nanoscale silica was synthesized by precipitation method using sodium silicate and dilute hydrochloric acid under controlled conditions. The synthesized silica was characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), BET adsorption and X-Ray Diffraction (XRD). The particle size of silica was calculated to be 13 nm from the XRD results and the surface area was found to be 295 m2/g by BET method. The performance of this synthesized nanosilica as a reinforcing filler in natural rubber (NR) compound was investigated. The commercial silica was used as the reference material. Nanosilica was found to be effective reinforcing filler in natural rubber compound. Filler-matrix interaction was better for nanosilica than the commercial silica. The synthesized nanosilica was used in place of conventional silica in HRH (hexamethylene tetramine, resorcinol and silica) bonding system for natural rubber and styrene butadiene rubber / Nylon 6 short fiber composites. The efficiency of HRH bonding system based on nanosilica was better. Nanosilica was also used as reinforcing filler in rubber / Nylon 6 short fiber hybrid composite. The cure, mechanical, ageing, thermal and dynamic mechanical properties of nanosilica / Nylon 6 short fiber / elastomeric hybrid composites were studied in detail. The matrices used were natural rubber (NR), nitrile rubber (NBR), styrene butadiene rubber (SBR) and chloroprene rubber (CR). Fiber loading was varied from 0 to 30 parts per hundred rubber (phr) and silica loading was varied from 0 to 9 phr. Hexa:Resorcinol:Silica (HRH) ratio was maintained as 2:2:1. HRH loading was adjusted to 16% of the fiber loading. Minimum torque, maximum torque and cure time increased with silica loading. Cure rate increased with fiber loading and decreased with silica content. The hybrid composites showed improved mechanical properties in the presence of nanosilica. Tensile strength showed a dip at 10 phr fiber loading in the case of NR and CR while it continuously increased with fiber loading in the case of NBR and SBR. The nanosilica improved the tensile strength, modulus and tear strength better than the conventional silica. Abrasion resistance and hardness were also better for the nanosilica composites. Resilience and compression set were adversely affected. Hybrid composites showed anisotropy in mechanical properties. Retention in ageing improved with fiber loading and was better for nanosilica-filled hybrid composites. The nanosilica also improved the thermal stability of the hybrid composite better than the commercial silica. All the composites underwent two-step thermal degradation. Kinetic studies showed that the degradation of all the elastomeric composites followed a first-order reaction. Dynamic mechanical analysis revealed that storage modulus (E’) and loss modulus (E”) increased with nanosiica content, fiber loading and frequency for all the composites, independent of the matrix. The highest rate of increase was registered for NBR rubber.

Anisotropy in elastic properties of lithium sodium sulphate hexahydrate single crystal—An ultrasonic study

The double sulfate family (ABSO4), where A and B are alkali metal cations, is the object of great interest owing to the complexity and richness of its sequence of phase transition induced by temperature variation. A new sulfate salt characterized by the presence of water molecule in the unit cell with the chemical formula, Li2Na3(SO4)2⋅6H2O (LSSW), was obtained. The ultrasonic velocity measurement was done with pulse echo overlap technique [PEO]. All the six second order elastic stiffness constants, C11 = C22, C33, C44 = C55, C12, C14 and C13 = C23 are reported for the first time. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the polar plots of phase velocity, slowness, Young’s modulus and linear compressibility in a–b and a–c planes.

Elastic constant measurements of super ionic LiKSO4:Na single crystals

Elastic properties of sodium doped Lithium potassium sulphate, LiK0.9Na0.1SO4, crystal has been studied by ultrasonic Pulse Echo Overlap [PEO] technique and are reported for the first time. The controversy regarding the type of crystal found while growth is performed at 35 °C with equimolar fraction of Li2SO4H2O, K2SO4 and Na2SO4 has been resolved by studying the elastic properties. The importance of this crystal is that it exhibits pyroelectric, ferroelectric and electro optic properties. It is simultaneously ferroelastic and superionic. The elastic properties of LiK0.9Na0.1SO4 crystal are well studied by measuring ultrasonic velocity in the crystal in certain specified crystallographic directions and evaluating the elastic stiffness constants, compliance constants and Poisson’s ratios. The anisotropy in the elastic properties of the crystal are well explained by the pictorial representation of the surface plots of phase velocity, slowness and linear compressibility in a-b and a-c planes.

Laser induced surface damage, thermal transport and microhardness studies on certain organic and semiorganic nonlinear optical crystals

N-alkyl-2,6-dimethyl-4(1H)-pyridinones, salts of 4-dimethylaminopyridine and 2-amino-5-nitropyridine are considered to be potential candidates for nonlinear optical (NLO) applications, in particular for the generation of blue-green laser radiation. Single crystals were grown following the slow evaporation technique at constant temperature. Single-shot laserinduced surface damage thresholds in the range 3–10 GW/cm2 were measured using a 18 ns Q-switched Nd:YAG laser. The surface morphologies of the damaged crystals were examined under an optical microscope and the nature of damage identified. The Vicker’s microhardness was determined at a load of 98.07 mN. The thermal transport properties, thermal diffusivity (α), thermal effusivity (e), thermal conductivity (K) and heat capacity (Cp), of the grown crystals were measured by an improved photopyroelectric technique at room temperature. All the results are presented and discussed.

Optimization of carbon and nitrogen sources and growth factors for the production of an aquaculture probiotic (Pseudomonas MCCB 103) using response surface methodology

Aim: To develop a new medium for enhanced production of biomass of an aquaculture probiotic Pseudomonas MCCB 103 and its antagonistic phenazine compound, pyocyanin. Methods and Results: Carbon and nitrogen sources and growth factors, such as amino acids and vitamins, were screened initially in a mineral medium for the biomass and antagonistic compound of Pseudomonas MCCB 103. The selected ingredients were further optimized using a full-factorial central composite design of the response surface methodology. The medium optimized as per the model for biomass contained mannitol (20 g l)1), glycerol (20 g l)1), sodium chloride (5 g l)1), urea (3Æ3 g l)1) and mineral salts solution (20 ml l)1), and the one optimized for the antagonistic compound contained mannitol (2 g l)1), glycerol (20 g l)1), sodium chloride (5Æ1 g l)1), urea (3Æ6 g l)1) and mineral salts solution (20 ml l)1). Subsequently, the model was validated experimentally with a biomass increase by 19% and fivefold increase of the antagonistic compound. Conclusion: Significant increase in the biomass and antagonistic compound production could be obtained in the new media. Significance and Impact of the Study: Media formulation and optimization are the primary steps involved in bioprocess technology, an attempt not made so far in the production of aquaculture probiotics.

Fabrication of thin films and nano columnar structures of Fe-Ni amorphous alloys and modification of its surface properties by thermal annealing and swift heavy ion irradiation for tailoring the magnetic properties

Department of Physics, Cochin University of Science and Technology

Surface acidity and catalytic activity of sulphated samaria

We have investigated the changes in surface acidity/basicity and catalytic pro~erties of samarium oxide due to surface modification by SO42- ion. The acidity/basicity of the catalysts is determined by titration method using Hammett indicators. Esterification of acetic acid by n-butanol is chosen as a test reaction. Sm203, owing to its high basicity and low acidity, does not catalyze the reaction. But sulphated Sm20J catalyzes the esterification reaction effectively. Activation temperature does not have much effect on the acidity of sulphated samaria.

Surface electron properties and catalytic activity of cerium-zirconium mixed oxides

The electron donating properties, surface acidity/ basicity and catalytic activity of cerium - zirconium mixed oxides at various compositions have been reported at an activation temperature of 500 degree C. The catalytic activity for the esterification of acetic acid with n-butanol has heen correlated with electron donating properties and surface acidity/basicity of the oxides.

Surface properties and catalytic activity of vanadia supported on rare earth oxides

An investigation on the physical and chemical characterisation of rare earth oxide supported vanadia is attempted in the present study. La2O3, Sm2O3 and DY2O3 serve the purpose of supports. Supported catalysts were prepared and characterised using various physico chemical techniques. A detailed investigation of acid base properties is also carried out. The nature of interaction of vanadia with lanthanide oxide is discussed and the effect of vanadia loading on the activity of the systems towards reactions of industrial importance is explored.

Surface properties and catalytic activity of vanadia supported on samaria

Sm2O3 - vanadia catalysts have been prepared by wet impregnation method using NH4VO3 solution. The surface properties of the prepared catalysts have been studied using FTIR. XRD. surface area and pore volume data. The acid-base properties of the system have been investigated by titrimetric method using Hammett indicators. adsorption of electron acceptors as well as decomposition of cyclohexanol. Phenol alkylation reaction by methanol has been carried out to investigate the catalytic activity. It has been observed that the selectivity of the products depends upon the composition of the supported system

Surface acidity and catalytic activity of mixed Fe-Al and Cr-Al pillared montmorillonites

The incorporation of transition metal oxide pillars such as those of iron and chromium along with Al2O3, pillars within the interlayers of a montmorillonite clay is investigated. The surface acidity of these catalysts has been evaluated for the first time employing the equilibrium adsorption of an electron donor, perylene, and the results are compared with those obtained by temperature programmed desorption of ammonia. The principle is based on the ability of a catalyst surface site to accept a single electron from an electron donor like perylene to form charge transfer complexes and the amount of adsorbed species is measured quantitatively by UV-vis spectroscopy. Fina1ly, an attempt has been made to correlate the acidity determined by the two independcnt methods and the catalytic activity of present systems in the benzoylation of toluene with benzoyl chloride. Incorporation of Fe and Cr has changed the properties of AI pitlared montmorillonite. Fe pillared systems have been found to be vcry good catalysts for benzoylation reaction

Surface acidity/basicity and catalytic activity of Zr-Sm mixed oxide systems

The surface acidity and basicity of oxides of Sm and Zr and their mixed oxides have been determined using a set of Hammett indicators. The data have been correlated with the catalytic activity of these oxides towards the liquid phase reduction of cyclo-hexanone in 2-propanol.

Surface electron properties of yttrium oxide supported on alumina

Cochin University of Science and Technology

Surface acidity/basicity of yttria and its mixed oxides with alumina catalysts

Acid/base strength distribution of Y2O3 and its mixed oxides with alumina catalysts are measured on Hammett acidity function scale and expressed in terms of H0max value. Basicity of Y2O3 increases with increase in activation temperature and for mixed oxides the basicity increases with increase in concentration of Y2O3, in the catalyst.