Double resonance Raman study of disorder in CVD-grown single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) with varying degrees of disorder were investigated using multiple-excitation Raman spectroscopy. The lattice disorder was imparted into the nanotubes by the addition of varying amounts of sulfur to the iron catalyst in a thermal chemical vapor deposition process. Changes in the intensities of peaks occurring due to a double resonance Raman process were studied. The intensity of the disorder-induced D band increased with a decrease in the sulfur content. Upon post-synthesis heat treatment, the double resonance process got quenched due to defect healing. The second order G′ band and iTOLA bands exhibited a two-peak structure, of which one of the peaks is relatively more sensitive to defects and decreased in intensity with heat treatment.     

Studies on the static and dynamic properties of different types of polyester industrial yarns

Four major types of polyester industrial yarns, viz. high tenacity (HT), high modulus low shrinkage (HMLS), low shrinkage (LS) and super low shrinkage (SLS) polyester yarns, were studied for their static and dynamic properties. An attempt has been made to establish a linkage between static and dynamic properties of these yarns with its structure and with its end applications. HMLS and HT polyester yarns have lower tan δ and work loss, which are the desired characteristics required for its end applications which include tire and conveyer belt. Higher overall orientation and higher fraction of tie molecules helped to achieve these properties in HT and HMLS polyester yarns. LS and SLS polyester yarns are mostly used for static applications. Low thermal shrinkage is the key requirement for the downstream processes of these yarns. Lower amorphous orientation in these two yarns is primarily responsible for achieving very low thermal shrinkage. A good co-relation has been established between the peak temperature of work loss (in slow speed hysteresis test) and the peak temperature of tan δ (in high-speed dynamic test).     

Effect of treatment of Bis(3‐triethoxysilyl propyl)tetrasulfane on physical property of in situ sodium activated and organomodified bentonite clay – SBR rubber nanocomposite

This study describes the effect of treatment of Bis(3‐triethoxysilyl propyl)tetrasulfane (silane coupling agent, Si69, TESPT) on in situ sodium activated, organo modified bentonite clay – styrene butadiene rubber (SBR) nanocomposite. transmission electron microscopy and Wide angle X‐ray diffraction indicated the intercalation as well as partial exfoliation in both the organoclay and silane treated organoclay compound. It was found that about 5% of silane with respect to clay was the optimum dose for the treatment. Around 15% improvement in tensile and tear strength was observed due to silane treatment. Silane treated organoclay exhibited substantial improvement of the fatigue life, compression set, and rebound property. A detailed study of physical property was carried out. A comparison with low and high structure carbon black filled compound was also carried out. It revealed that the silane treatment helped organoclay to achieve comparable property of the compound having equivalent carbon black loading. Probable mechanism of interaction of silane with clay has also been proposed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of polyaniline nanofibers and nanoparticles via simultaneous doping and electro-deposition

We present a new post-synthetic method for producing different nano-structures of Polyaniline (PANI), especially nano-fibers and nano-particles of varying doping (oxidation) states, by simultaneous doping and electro-deposition from electrolyte solutions of undoped PANI (Emeraldine bases) and p-toluenesulphonic acid using constant applied voltage and varying deposition time. High Resolution Transmission Electron Microscopy analysis reveals that during the initial doping-dominated stage continuous connected conductive PANI Emeraldine salt nano-fibers of diameter less than 50 nm are formed while in the later deposition-dominated stage, 30-50 nm sized isolated dispersed nano-particles of non conductive Leuco-Emeraldine are formed.     

SMoS: a database of structural motifs of protein superfamilies

The Structural Motifs of Superfamilies (SMoS) database providesinformation about the structural motifs of aligned protein domainsuperfamilies. Such motifs among structurally aligned multiplemembers of protein superfamilies are recognized by the conservationof amino acid preference and solvent inaccessibility and areexamined for the conservation of other features like secondarystructural content, hydrogen bonding, non-polar interactionand residue packing. These motifs, along with their sequenceand spatial orientation, represent the conserved core structureof each superfamily and also provide the minimal requirementof sequence and structural information to retain each superfamilyfold. Received April 25, 2003; revised September 9, 2003; accepted September 24, 2003.     

Multi-mode low-dimensional models for non-isothermal homogeneous and catalytic reactors

A systematic procedure based on the Liapunov-Schmidt method of bifurcation theory is used to derive low-dimensional models for different types of non-isothermal homogeneous, catalytic and coupled homogeneous-heterogeneous reactors. These low-dimensional models are described by multiple concentration and temperature modes (variables), each of which is representative of a physical scale of the system. These “multi-mode models” capture mass and thermal micromixing as exchange of material and energy, respectively, between the modes (scales). The multi-mode models retain all the parameters and most of the qualitative features of the full convection-diffusion-reaction equations. While in the limit of vanishingly small local heat and mass diffusion times, they reduce to the classical ideal pseudo-homogeneous reactor models, they are also capable of capturing the mixing or mass (and/or heat) transfer-limited asymptotes for the case of fast reactions. We illustrate the usefulness of the multi-mode models in predicting mixing and selectivity effects on reactor performance and the influence of local transport effects on reactor runaway and bifurcation behavior for the case of non-isothermal homogeneous and catalytic reactors.     

Montmorillonite clay nanocomposites based on vinyl pyridine‐styrene‐butadiene terpolymer (VPR)/acrylonitrile‐butadiene rubber (NBR) blend

This study describes a novel route to synthesize vinyl pyridine‐styrene‐butadiene terpolymer rubber (VP rubber) montmorillonite clay nanocomposites by latex blending technique. The pyridine moiety of the VP rubber was modified with methyl iodide to form the pyridinium ion during latex blending. Cation exchange reaction of the pyridinium ion of the VP rubber latex with sodium montmorillonite occurred during latex stage mixing which helped to form VP rubber‐montmorillonite clay nanocomposites. Coagulation of the latex‐clay slurry produced nanocomposites master batch. The master batch was compounded with acrylonitrile butadiene rubber (NBR). Fourier Transform Infrared Spectroscopy (FTIR) confirmed the modification of the pyridine moiety of VP rubber. Wide angle X‐ray diffraction (WAXD), scanning electron microscopy‐energy dispersive X‐ray spectrophotometry (SEM‐EDS) and transmission electron microscopy (TEM) provided the evidences of formation of nanocomposite. Remarkable improvements in the mechanical properties were found by addition of small amount of modified clay. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers