Synthesis of 3D nanostructured metal alloy of immiscible materials induced by megahertz-repetition femtosecond laser pulses

In this work, we have proposed a concept for the generation of three-dimensional (3D) nanostructured metal alloys of immiscible materials induced by megahertz-frequency ultrafast laser pulses. A mixture of two microparticle materials (aluminum and nickel oxide) and nickel oxide microparticles coated onto an aluminum foil have been used in this study. After laser irradiation, three different types of nanostructure composites have been observed: aluminum embedded in nickel nuclei, agglomerated chain of aluminum and nickel nanoparticles, and finally, aluminum nanoparticles grown on nickel microparticles. In comparison with current nanofabrication methods which are used only for one-dimensional nanofabrication, this technique enables us to fabricate 3D nanostructured metal alloys of two or more nanoparticle materials with varied composite concentrations under various predetermined conditions. This technique can lead to promising solutions for the fabrication of 3D nanostructured metal alloys in applications such as fuel-cell energy generation and development of custom-designed, functionally graded biomaterials and biocomposites.     

Effect of nanoclay on positive temperature coefficient to resistivity characteristics of high density polyethylene/silver‐coated glass bead composites

Positive temperature coefficient to resistivity characteristics of high density polyethylene (HDPE)/silver (Ag)‐coated glass bead (45 wt%) composites, without and with nanoclay, has been investigated with reference to HDPE/carbon black (CB) (10 wt%) composites. Plot of resistivity versus temperature of HDPE/CB (10 wt%) composites showed a sudden rise in resistivity (PTC trip) at ≈128°C, close to the melting temperature (T_m) of HDPE. However, for HDPE/Ag coated glass bead (45 wt%) composites, the PTC trip temperature (≈88°C) appeared well below the T_m of HDPE. Addition of 1 phr clay in the composites resulted in an increase in PTC trip temperature of HDPE/Ag‐coated glass bead (45 wt%) composites, whereas no significant effect of clay on PTC trip temperature was evident in HDPE/CB/clay composites. We proposed that the PTC trip temperature in HDPE/Ag‐coated glass bead composites was governed by the difference in coefficient of thermal expansion of HDPE and Ag‐coated glass beads. The room temperature resistivity and PTC trip temperature of HDPE/Ag‐coated glass bead (45 wt%) composites were found to be very stable on thermal cycling. Dynamic mechanical analyzer results showed higher storage modulus of HDPE/Ag‐coated glass bead (45 wt%) composites compared with the HDPE/CB (10 wt%) composites. Thermal stability of HDPE/Ag‐coated glass bead (45 wt%) composites was also improved compared with that of HDPE/CB (10 wt%) composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Transport and solvent sensing characteristics of styrene butadiene rubber nanocomposites containing imidazolium ionic liquid modified carbon nanotubes

Obtaining strong interfacial interaction between filler and polymer matrix is very crucial for the fabrication of polymer nanocomposites with superior performance. Present study is aimed to fabricate high performance styrene butadiene rubber (SBR) nanocomposites with imidazolium type ionic liquid modified multiwalled carbon nanotube (MWCNT). Ionic liquid facilitates the dispersion of MWCNT in rubber matrix and it is obvious from transmission electron microscopy images. Diffusion of toluene through SBR nanocomposite membranes has been investigated as a function of surface modified MWCNT (f-MWCNT) content to analyze the chain dynamics and filler-polymer interactions. O₂ gas barrier effect of nanocomposites with special reference to the filler loading is explored. The substantial improvement in the barrier effect in presence of filler interpreted on the grounds of a theoretical model describing permeability of heterogeneous systems. Finally solvent sensing characteristics of prepared nanocomposites are also analyzed and it is observed that prepared nanocomposites can be used as a flexible solvent sensor.     

Removal of Cu2+ from Water Using Liquid-Liquid Microchannel Extraction

The very good extraction selectivity of Cu²⁺ from water was demonstrated with a new microchannel equipment, by employing di-(2-ethylhexyl)phosphoric acid (D2EHPA) as an extractant and kerosene as a solvent. The effects of different experimental parameters on the extraction efficiency E, the volumetric mass transfer coefficient K_La, and the entrainment were experimentally investigated. The results showed that the extraction efficiency increased with increasing temperature, extractant concentration, phase ratio (organic/aqueous), and pH. The total flow rate, phase ratio, and pH were found to have a great effect on the mass transfer, whereas the temperature and the extractant concentration showed little effect.     

Low-Temperature Electrochemical Synthesis of ZrO2 Films on Zirconium Substrates: Deposition of Thick Amorphous Films and in situ Crystallization on Zirconium Anode

The feasibility of synthesizing crystalline ZrO₂ films at low temperatures was evaluated using an electrochemical method. Anodization of zirconium-metal substrates in tetraethyl ammonium hydroxide (TEAOH) solutions under constant applied voltage conditions at ∼25° and ∼100°C was investigated. The chemistry and microstructure of the anodic oxide films deposited on the zirconium-metal substrates under the above conditions were characterized using X-ray diffractometry and scanning electron microscopy. The results indicated that, with sufficiently high applied voltages (in the range of 300 V) at pH ∼9.5, the initial dissolution of the zirconium anode resulted in the local saturation of the electrolyte solution with Zr⁴⁺, forming Zr(OH)⁻₅, which deposited electrophoretically on the anode as a thick, gelatinous film at 25°C. Similar treatments at 100°C resulted in an in situ crystallization of Zr(OH)₄ gel to monoclinic ZrO₂.     

Moisture diffusion through (hexadecyltrimethylammonium bromide ‐ Indian bentonite)/(vinylester) nanocomposites in artificial seawater and demineralized water

This paper compares the moisture diffusion properties of organomodified (Indian Bentonite nanoclay)/vinylester containing different amounts of nanoclay on exposure to demineralized water and artificial seawater at room temperature. Moisture uptake behavior of (Indian Bentonite)/vinylester was investigated and compared with that of neat vinylester. Addition of 5 wt% nanoclay decreased the diffusivity and permeability of vinylester in artificial seawater medium, but these diffusion parameters increased in demineralized water medium. Degradation in glass transition temperature and microhardness of the nanocomposites were much greater in specimens aged in demineralized water than in those in artificial seawater medium. Moisture diffusion behavior of the specimens was analyzed by Fick's law and the Langmuir model. The aged specimens were chemically analyzed by using infrared spectroscopy after aging for 146 days. A significant amount of leached organic species was detected in the demineralized water–aged specimens but the same was absent in those aged in artificial seawater. J. VINYL ADDIT. TECHNOL., 22:441–451, 2016. © 2015 Society of Plastics Engineers     

Computer simulation and comparative study on the pervaporation separation characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) to separate aqueous mixtures of 1,4‐dioxane or tetrahydrofuran

A comparative study on the pervaporation separation has been attempted for water + 1,4‐dioxane and water + tetrahydrofuran mixtures using sodium alginate and blend membranes of sodium alginate with 5, 10, and 20 mass % of poly(vinyl alcohol). Pure sodium alginate membrane has a selectivity of 111 to water at 0.35‐mol fraction of water in the feed mixture containing 1,4‐dioxane while for water + tetrahydrofuran mixture, the membrane selectivity to water was 291 at 0.31‐mol fraction of water in the feed mixture. Pervaporation results have been discussed using the solution–diffusion principles. Arrhenius activation parameters for diffusion and permeation have been computed from the temperature‐dependent pervaporation results. Furthermore, experimental results have been analyzed using the complete mixing and plug flow models to compute membrane area as well as design parameters that are useful in scale‐up operations. The plug flow model is more appropriate than the complete mixing model to analyze the pervaporation results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1827–1840, 2004     

Toughening of Polylactic Acid: An Overview of Research Progress

To overcome the limitations of polylactic acid, alterations are needed to enhance its toughness, to improve handling and for various applications. Extensive studies were reported, mainly in the area of blends with renewable resource polymer blends. Better phase dispersion between the blend materials is achieved either by reactive mixing of the two components or by incorporation of a block copolymer compatibilizer, finally showing highly enhanced property. In this article, the recent research progress of different toughening processes of PLA via blending is reviewed and a detailed understanding about toughening of PLA using biodegradable or renewable polymers has been established.     

Molecular and thermal studies of carbon fiber precursor polymers with low thermal‐oxidative stabilization characteristics

In this investigation, terpolymers, copolymers, and homopolymer of acrylonitrile with dimethylaminopropyl acrylamide (DMAPA), itaconic acid (IA) viz., poly(acrylonitrile‐ran‐3‐dimethylaminopropyl acrylamide‐ran‐itaconic acid) [P(AN‐DMAPP‐IA)], poly(acrylonitrile‐co‐3, dimethylaminopropyl acrylamide) [P(AN‐DMAPP)] were synthesized with varying amounts of comonomers using solution polymerization process. The chemical structure, composition, bonding network were determined employing infrared, 1H and, 13‐carbon nuclear magnetic resonance spectroscopic techniques. Molecular characteristics of as‐synthesized polymers such as different kinds of average molecular weights, molecular weight distribution were estimated applying solution viscometry and size exclusion chromatography. The influence of comonomers (DMPAA, IA) on the thermal stabilization characteristics of acrylonitrile terpolymers in comparison with copolymers and homopolymers of acrylonitrile were studied using differential scanning calorimetry (DSC), hyphenated thermal techniques (thermal gravimetry coupled with differential thermal analyzer).The DSC curves of P(AN‐DMAPP‐IA) exhibit a distinct broader bimodal peaks with thermal exotherm initiating at as low as 165 °C, and followed by two peaks with temperature difference of 42 °C, releasing the evolved heat at a release rate of 0.7–0.11 J g^?1s^?1over 10 min as compared to 1.2, 7.5 J g^?1s^?1 in 4.5, 2 min as observed in P(AN‐DMAPP), polyacrylonitrile, respectively. The thermal stability of P(AN‐DMAPP‐IA) and P(AN‐DMAPP), as evidenced by TGA‐DTA was found to be higher than PAN homopolymers. Specific heat capacity measurements confirmed the DSC results. Bulk densities of P(AN‐DMAPP‐IA) were in the range 0.31–0.35 g/cc. These results confirm the low‐temperature stabilization characteristics and suitability of P(AN‐DMAPP‐IA) as low cost carbon fiber precursor polymers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46381.     

Curing Studies of Ladder-Like Poly(allylsilsesquioxane) and its copolymers by Differential Scanning Calorimetry

Summary Using stepwise coupling polymerization method, three ladder-like poly(allylsilsesquioxane)s have been synthesized. The prepared ladder-like polymers contain (i) allyl, (ii) allyl and methyl and (iii) allyl and phenyl as side chain groups. They were characterized by FTIR, NMR, WAXD, DSC and TGA. Characterization indicated that they had ladder-like structure. All the polymers were cured by 2,2-dibenzoyl peroxide (1% W/W) and the kinetics for the bulk polymerization of these polysilsesquioxanes was followed by dynamic DSC. The Ozawa and Kissinger methods were used to calculate activation energies for curing of these polysilisesquioxanes. Cured samples were characterized by FTIR, DSC and TGA.