An investigation of the flocculation characteristics of polyacrylamide‐grafted chitosan

To investigate the flocculation characteristics of polyacrylamide (PAM)‐grafted chitosan, a series of PAM‐grafted chitosan copolymer (Chito‐g‐PAM1 to Chito‐g‐PAM4) have been synthesized by ceric ammonium nitrate‐induced solution polymerization technique in nitrogen atmosphere. The flocculation characteristics of the polymer samples (PAM, grafted and ungrafted chitosan) were studied by settling test and jar test methods in the colloidal suspensions of kaolin, iron ore, silica, and bentonite powder. It was found that the settling performance of Chito‐g‐PAM3 is best among the polymer samples. The jar test results indicate that the ungrafted chitosan has better water clarifying performance than both the PAM and grafted chitosan. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of organic modifiers and silicate type on filler dispersion,thermal, and mechanical properties of ABS‐clay nanocomposites

Acrylonitrile–butadiene–styrene (ABS)–clay composite and intercalated nanocomposites were prepared by melt processing, using Na‐montmorillonite (MMT), several chemically different organically modified MMT (OMMT) and Na‐laponite clays. The polymer–clay hybrids were characterized by WAXD, TEM, DSC, TGA, tensile, and impact tests. Intercalated nanocomposites are formed with organoclays, a composite is obtained with unmodified MMT, and the nanocomposite based on synthetic laponite is almost exfoliated. An unintercalated nanocomposite is formed by one of the organically modified clays, with similar overall stack dispersion as compared to the intercalated nanocomposites. T_g of ABS is unaffected by incorporation of the silicate filler in its matrix upto 4 wt % loading for different aspect ratios and organic modifications. A significant improvement in the onset of thermal decomposition (40–44°C at 4 wt % organoclay) is seen. The Young's modulus shows improvement, the elongation‐at‐break shows reduction, and the tensile strength shows improvement. Notched and unnotched impact strength of the intercalated MMT nanocomposites is lower as compared to that of ABS matrix. However, laponite and overexchanged organomontmorillonite clay lead to improvement in ductility. For the MMT clays, the Young's modulus (E) correlates with the intercalation change in organoclay interlayer separation (Δd₀₀₁) as influenced by the chemistry of the modifier. Although ABS‐laponite composites are exfoliated, the intercalated OMMT‐based nanocomposites show greater improvement in modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study on microhardness,dynamic mechanical,and tribological properties of PEEK/Al2O3 composites

The wear and friction properties of poly (ether‐ether‐ketone) (PEEK) reinforced with 0–33 vol % (60 wt %) micron size Al₂O₃ composites were evaluated at a sliding speed of 1.0 m/s and nominal pressure from 0.5 to 1.25 MPa under dry sliding conditions using a pin‐on‐disk wear tester. The wear resistance of the pure PEEK is 10‐fold higher than that of mild steel under the similar test condition. It is improved to 18‐fold as compared with mild steel at 3.5 vol % Al₂O₃ content. The improvement in wear properties may be attributed to the thin, tenacious, and coherent transfer film formed between the steel countersurface and composite pin. However, the wear resistance of PEEK containing above 3.5 vol % Al₂O₃ was deteriorated, despite their higher hardness and stiffness as compared with that of composites containing lower Al₂O₃ content. This is attributed to the formation of thick and noncoherent transfer film, which does not prevent the wear of the composites from hard asperities of countersurface. Moreover, hard Al₂O₃ particles present in transfer film act as third body wear mechanism. The coefficient of friction of the composites is higher than that of pure PEEK. SEM and optical microscopy have shown that wear of pure PEEK occurs by the mechanism of adhesion mainly whereas of PEEK composites by microploughing and abrasion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Low-Temperature Sintering of La(Ca)CrO3 Powder Prepared through the Combustion Process

Ultrafine La(Ca)CrO₃ (LCC) powder was prepared through the glycine–nitrate gel combustion process. It was shown for the first time that the use of relatively inexpensive CrO₃ as a starting material for chromium has potential for the bulk preparation of sinter-active LCC powder. As-prepared powder, when calcined at 700°C, resulted in LCC along with a small amount of CaCrO₄. The calcined powder was found to be composed of soft agglomerates with a particle size of ≈70–290 nm. The cold pressing and sintering of the calcined powder at 1200°C resulted in the mono-phasic La_0.7Ca_0.3CrO₃ with density ≈98% of its theoretical value. This is the lowest sintering temperature ever reported for La_0.7Ca_0.3CrO₃. The conductivity of the sintered La_0.7Ca_0.3CrO₃ at 1000°C was found to be ≈57 S/cm in air. The sintering and electrical behavior achieved for La_0.7Ca_0.3CrO₃ may find application as an interconnect material for high-temperature solid oxide fuel cells if problems with chemical expansion and poor conductivity in fuel can be overcome.     

Corrosion inhibition behaviour of thiourea derivatives in acid media against mild steel deterioration: An overview

This paper summarizes the inhibitor activity of various reported thiourea derivatives in acid media used against the deterioration of mild steel. Acid solutions have been extensively employed in manufacturing and many industrial processes for pickling and removal of undesirable scale. Mild steel is highly susceptible to corrosion in such aggressive acid media. The additives such as inhibitors are widely employed in those cases to reduce the extent of corrosion as much as possible. The survey of literature on organic inhibitors clearly indicates the potential usage of thiourea derivatives as inhibitors of mild steel corrosion. The influence of physical-chemical properties on the inhibition activity of thiourea derivatives has been discussed. This information is highly useful for different industrial applications where good performing inhibitors are being required for protecting mild steel from aggressive acid media.     

Antimicrobial properties of silver-doped hydroxyapatite nano-powders and thin films

Silver-doped hydroxyapatite nanopowders were prepared using a solution based sol-gel method and thoroughly characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Antibacterial tests showed silver-doped HAP powders prevented the growth and reproduction of bacteria. Silver-doped HAP powders were pressed into pellets and on these pellets a pulsed laser deposition (PLD) technique was employed to grow amorphous and crystalline thin films on sapphire substrates. Crystalline films had silver nano-particles present within the HAP matrix. Film stability tests showed crystalline films to be far more stable in prolonged solution submersion than their amorphous counterparts.     

Proton Nuclear Magnetic Resonance-Based Method for the Quantification of Epoxidized Methyl Oleate

Epoxidized methyl esters (EMO) with their high oxirane ring reactivity, acts as a raw material in the synthesis of various industrial chemicals including polymers, stabilizers, plasticizers, glycols, polyols, carbonyl compounds, biolubricants etc. EMO has been generally quantified by the gas chromatography (GC) and high-performance liquid chromatography (HPLC) techniques. Taking into the account of the limitations of these techniques, two qHNMR-based equations have been proposed for the quantification of EMO in the mixture of EMO and methylesters (MO). The validity of the proposed method was determined using standard mixtures of MO and EMO having different molar concentrations. The developed equations have been applied on the samples of EMO prepared from oleic acid in two-step process viz., esterification followed by epoxidation. The qHNMR-based EMO quantification showed acceptable agreement with the results obtained from HPLC analysis.     

Structural,Optical, and Ferroelectric Behaviors of Cu_(1-x)Li_xO(0≤x≤0.09) Nanostructures

We report structural,optical,and ferroelectric behaviors of lithium-doped copper oxide(Cu1-xLixO with x =0.0,0.05,0.07,and 0.09) nanostructures synthesized by hydrothermal method.The XRD pattern indicates the pure phase formation of CuO without any impurity,and the crystallite size is found to be increases for x =0–0.07 and decreases for x =0.09.FESEM analysis shows that the average size of Cu1-xLixO nanostructures increases with the increasing the Li-doping concentrations up to 7% and then decreases for 9% Li doping concentration.Moreover,Raman and photoluminescence spectrum also confirm the phase formation of CuO.A significant reduction in optical band gap is observed up to x =0.07,and then band gap increases for x =0.09 due to segregation of the impurities on the surface or grain boundaries,which may suppress the grain growth and results the enhancement in optical band gap.Moreover,a weak ferroelectricity is observed in CuO nanostructures for pure and 9% Li doping through polarization versus electric field(P–E).     

In situ observation of Cu segregation and phase nucleation at a solid–liquid interface in an Al alloy

This paper presents a systematic study comparing experimental in situ transmission electron microscopy observation of microstructural and compositional evolution with complementary thermodynamic calculations, to better understand the redistribution of solute elements and the nucleation behavior of different phases in a commercial Al-alloy powder (AA390). The results show that Cu segregation to the solid Si–liquid Al interface, as well as the significant undercooling achieved in the liquid under non-equilibrium conditions because the Al phase cannot nucleate homogeneously, play a important roles in nucleating Al₂Cu at the interface prior to the Mg₂Si phase in the alloy. Although Cu segregation can occur at various locations along the interface, the Al₂Cu phase appears to preferentially nucleate at a high-index Si–liquid interface as opposed to a low-index one. The Cu concentration during segregation remains essentially constant with time, indicating that the observed segregation behavior is a thermodynamic and not a kinetic phenomenon. These in situ observations and complementary thermodynamic calculations substantially enhance our understanding of potential crystal nucleation and growth processes.     

Application of an immobilized microbial consortium for the treatment of pharmaceutical wastewater: Batch-wise and continuous studies

In the present investigation, a microbial consortium consisting of four bacterial strains was selected for the treatment of pharmaceutical industry wastewater. The consortium was immobilized on a natural support matrix-Luffa and used for the treatment of real-time pharmaceutical wastewater in batch and continuous processes. The batch process was carried out to optimize the culture conditions and monitor the enzymatic activity. An array of enzymes such as alcohol dehydrogenase, aldehyde dehydrogenase, monooxygenase, catechol 2,3-dioxygenase and hydroquinol 1,2-dioxygenase were produced by the consortium. The kinetics of the degradation in the batch process was analyzed and it was noted to be a first-order reaction. For the continuous study, an aerobic fixed-film bioreactor (AFFBR) was utilized for a period of 61 days with variable hydraulic retention time (HRT) and organic loading rate (OLR). The immobilized microbes treated the wastewater by reducing the COD, phenolic contaminants and suspended solids. The OLR ranged between (0.56 ± 0.05) kg COD·m^-3 d^-1 to 3.35 kg COD·m^-3·d^-1 and the system achieved an average reduction of 96.8% of COD, 92.6% of phenolic compounds and 95.2% of suspended solids. Kinetics of the continuous process was interpreted by three different models, where the modified Stover Kincannon model and the Grau second-order model proved to be best fit for the degradation reaction with the constant for saturation value, KL being 95.12 g·L^-1·d^-1, the constant for maximum utilization of the substrate U_max being 90.01 g·L^-1 d^-1 and substrate removal constant K_Y was 1.074 d^-1 for both the models. GC-MS analysis confirmed that most of the organic contaminants were degraded into innocuous metabolites.