Effect of carbon black on properties of rubber nanocomposites

Polymer based nanocomposites were prepared using brominated poly(isobutylene‐co‐paramethylstyrene) (BIMS) rubber and octadecyl amine modified montmorillonite nanoclay. The effect of nature and loading of carbon black on these nanocomposites and the control BIMS was investigated thoroughly using X‐ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), and mechanical properties. The addition of 4 parts of the modified nanoclay to 20 phr N550 carbon black filled samples increased the tensile strength by 53%. Out of the three different grades of carbon black (N330, N550, and N660), N550 showed the best effect of nanoclay. Optimum results were obtained with the 20 phr filler loading. For comparison, china clay and silica at the same loading were used. Fifty‐six and 46% improvements in tensile strength were achieved with 4 parts of nanoclay added to the silica and the china clay filled samples, respectively. N330 carbon black (20 parts) filled styrene butadiene rubber (SBR) based nanocomposite registered 20% higher tensile strength with 4 parts of the modified nanoclay. In all the above carbon black filled nanocomposites, the modulus was improved in the range of 30 to 125%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 443–451, 2005     

Interaction of metal ions with clays: I. A case study with Pb(II)

Pb(II) adsorption was studied under different conditions (pH, time, metal ion concentration, clay amount, temperature) on kaolinite, montmorillonite, and their poly(hydroxo)zirconium (ZrO–kaolinite, ZrO–montmorillonite) and tetrabutylammonium (TBA–kaolinite, TBA–montmorillonite) derivatives. All samples were calcined (ZrO-derivatives at 773 K, TBA-derivatives at 973 K) before using as adsorbents. The data were interpreted assuming first- and second-order kinetics. The rate constants including the pore diffusion rate constant are reported. The adsorption data could be fitted with Freundlich and Langmuir isotherms, and the coefficients indicated favorable adsorption of Pb(II) on the clays. Determination of the thermodynamic parameters, ΔH, ΔS, and ΔG showed the adsorption to be exothermic accompanied by decrease in entropy and Gibbs energy.     

Ethylene–octene copolymer (engage)–clay nanocomposites: Preparation and characterization

In this work, preparation and properties of nanoclay modified by organic amine (octadecyl amine, a primary amine) and Engage (ethylene–octene copolymer)–clay nanocomposites are reported. The clay and rubber nanocomposites have been characterized with the help of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The X‐ray results suggest that the intergallery spacing of pristine clay increases with the incorporation of the amine. The XRD peak observed in the range of 3–10° for the modified clay also disappears in the rubber nanocomposites at low loading. TEM photographs show exfoliation of the clays in the range of 10–30 nm in Engage. In the FTIR spectra of the nanocomposite, there are common peaks for the virgin rubber as well as those for the clay. Excellent improvement in mechanical properties, like tensile strength, elongation at break, and modulus, is observed on incorporation of the nanoclay in Engage. The storage modulus increases, tan δ peak decreases, and the glass transition temperature is shifted to higher temperature. The results could be explained with the help of morphology, dispersion of the nanofiller, and its interaction with the rubber. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 603–610, 2006     

Kaolinite, montmorillonite, and their modified derivatives as adsorbents for removal of Cu(II) from aqueous solution

Adsorption of metals by clay minerals is a complex process controlled by a number of environmental variables. The present work investigates the removal of Cu(II) ions from an aqueous solution by kaolinite, montmorillonite, and their poly(oxo zirconium) and tetrabutylammonium derivatives. The entry of ZrO and TBA into the layers of both kaolinite and montmorillonite was confirmed by XRD measurement. The specific surface areas of kaolinite, ZrO-kaolinite, TBA-kaolinite, montmorillonite, ZrO-montmorillonite, TBA-montmorillonite were 3.8, 13.4, 14.0, 19.8, 35.8 and 42.2 m²/g, respectively. The cation exchange capacity (CEC) was measured as 11.3, 10.2, 3.9, 153.0, 73.2 and 47.6 meq/100 g for kaolinite, ZrO-kaolinite, TBA-kaolinite, montmorillonite, ZrO-montmorillonite, TBA-montmorillonite, respectively. Adsorption increased with pH till Cu(II) ions became insoluble in alkaline medium. The kinetics of the interactions suggests that the interactions could be best represented by a mechanism based on second order kinetics (k₂ = 7.7 × 10⁻² to 15.4 × 10⁻² g mg⁻¹ min⁻¹). The adsorption followed Langmuir isotherm model with monolayer adsorption capacity of 3.0–28.8 mg g⁻¹. The process was endothermic with ΔH in the range 29.2–50.7 kJ mol⁻¹ accompanied by increase in entropy and decrease in Gibbs energy. The results have shown that kaolinite, montmorillonite and their poly(oxo zirconium) and tetrabutyl-ammonium derivatives could be used as adsorbents for separation of Cu(II) from aqueous solution.     

Modulation of Ultrafast Conformational Dynamics in Allosteric Interaction of Gal Repressor Protein with Different Operator DNA Sequences

Although all forms of dynamical behaviour of a protein under allosteric interaction with effectors are predicted, little evidence of ultrafast dynamics in the interaction has been reported. Here, we demonstrate the efficacy of a combined approach involving picosecond‐resolved FRET and polarisation‐gated fluorescence for the exploration of ultrafast dynamics in the allosteric interaction of the Gal repressor (GalR) protein dimer with DNA operator sequences O_E and O_I. FRET from the single tryptophan residue to a covalently attached probe IAEDANS at a cysteine residue in the C‐terminal domain of GalR shows structural perturbation and conformational dynamics during allosteric interaction. Polarisation‐gated fluorescence spectroscopy of IAEDANS and another probe (FITC) covalently attached to the operator directly revealed the essential dynamics for cooperativity in the protein–protein interaction. The ultrafast resonance energy transfer from IAEDANS in the protein to FITC also revealed different dynamic flexibility in the allosteric interaction. An attempt was made to correlate the dynamic changes in the protein dimers with O_E and O_I with the consequent protein–protein interaction (tetramerisation) to form a DNA loop encompassing the promoter segment.     

Effect of conventional and microwave heating on the structural and physicochemical properties of silver-doped hydroxyapatite nanopowders

ABSTRACT

This paper discussed the influence of duration and modes of heating on structural and physicochemical properties of silver-doped hydroxyapatite (Ag-HAP) nanopowders (NPs). Conventional electric furnace and microwave (MW) heating modes were employed during the synthesis. MW mode of synthesis was relatively an efficient method as it prepared monolithic HAP NP in just one minute of heating. With the increase in duration of heating in both modes of heating; lattice parameters, crystal size, lattice strain, Ca/P ratio, and degree of crystallinity of HAP phase increased. The morphology of particles was rod-shaped having aspect ratio between 2 and 3. EDX confirmed the presence of Ag and corroborated the formation of apatite. The hydrodynamic diameter of Ag-HAP NPs was significantly bigger than the particle sizes calculated using XRD, FESEM, and TEM. Thus, an overall examination concluded MW as an efficient mode of synthesis, able to produce Ag-HAP NPs in a possible minimum time.     

Polarization study on doped lanthanum gallate electrolyte using impedance spectroscopy

Alternating current complex impedance spectroscopy studies were conducted on symmetrical cells of the type [gas, electrode/La_1−x Sr _x Ga_1−y Mg _y O₃ (LSGM) electrolyte/electrode, gas]. The electrode materials were slurry-coated on both sides of the LSGM electrolyte support. The electrodes selected for this investigation are candidate materials for solid oxide fuel cell (SOFC) electrodes. Cathode materials include La_1−x Sr _x MnO₃ (LSM), La_1−x Sr _x Co _y Fe_1−y O₃ (LSCF), a two-phase particulate composite consisting of LSM and doped-lanthanum gallate (LSGM), and LSCF + LSGM. Pt metal electrodes were also used for the purpose of comparison. Anode material investigated was the Ni + Ce_0.85Gd_0.15O₂ composite. The study revealed important details pertaining to the charge-transfer reactions that occur in such electrodes. The information obtained can be used to design electrodes for intermediate temperature SOFCs based on LSGM electrolytes. This paper was presented at the Fuel Cells: Materials, Processing, and Manufacturing Technologies Symposium sponsored by the Energy/Utilities Industrial Sector & Ground Transportation Industrial Sector and the Specialty Materials Critical Technologies Sector at the ASM International Materials Solutions Conference, October 13–15, 2003, in Pittsburgh, PA. The symposium was organized by P. Singh, Pacific Northwest National Laboratory, S.C. Deevi, Philip Morris USA, T. Armstrong, Oak Ridge National Laboratory, and T. Dubois, U.S. Army CECOM.     

A computer-aided system for sustainability assessment for the die-casting process planning

The sustainability assessment of a product's manufacturing using a life cycle assessment tool utilizes the average sustainability performance of the manufacturing process. Because of using an average of sustainability performance, the crucial information related to manufacturing is lost. Therefore, such an assessment cannot be used to assess and compare the sustainability of a part made using different process plans. In this paper, we propose a new systematic approach for sustainability assessment of the die-casting process planning. A computer-aided system named Sustainability Assessor for Die-casting is presented. Here, we discuss the details of the architecture and working of the proposed system. We assess sustainability using three sustainability indicators, namely, energy use, solid waste, and carbon emissions. The proposed system is verified by comparing results with the actual data measured from the shop floor. The developed system is beneficial for sustainability assessment comparing different plans alongside material properties, ultimately helping the die-casting industry to reduce the carbon emissions and material waste, besides improving energy efficiency.     

Etched multimode microfiber knot-type loop interferometer refractive index sensor

We propose a novel refractive index sensor based on multimode microfiber knot-type loop (NL) interferometer. The middle portion (~5 cm) of a 15 cm long multimode fiber is etched in 48% hydrofluoric acid to reduce its diameter to ~12 μm. A NL of diameter <1 mm is made from the etched fiber. The ends of etched fiber are spliced with single-mode fibers for launching and detecting light from the NL interferometer. The NL introduces path differences to produce interferometric spectra with free spectral range ~16 nm. The spectrum shifts as the surrounding refractive index of the loop is changed by adding chemicals. We observe the highest sensitivity of the NL interferometer ~172 nm/RIU (refractive index unit) at a refractive index value 1.370 as obtained experimentally using commonly available chemicals. The design could be used as simple, low cost, and highly sensitive biological and chemical sensor.