纳米TiO2对D16T铝合金微弧氧化膜耐磨性的影响及机理

目的 提高D16T铝合金的耐磨损性能。方法 通过向硅酸盐和磷酸盐混合电解液体系中添加2 g/L纳米TiO2添加剂,利用微弧氧化技术在其表面制备微弧氧化陶瓷膜。采用X射线衍射仪（XRD）、扫描电镜（SEM）、能谱分析仪（EDS）、显微硬度计、厚度测试仪、摩擦磨损试验机等,研究了纳米TiO2添加剂对D16T铝合金微弧氧化膜的结构和耐磨损性能的影响及机理。结果 纳米TiO2的添加使得微弧氧化膜层的表面变得更加平整、致密,具有更少的微孔和裂纹,大大改善了膜层结构。相比于未添加纳米TiO2的电解液中制得的微弧氧化膜,在含纳米TiO2的电解液中所制得的微弧氧化膜中有新相TiO2生成,并且促使更多的α-Al2O3相和γ-Al2O3相生成,使膜层厚度得到明显增加,膜厚达31.2 μm,显微硬度也得到显著提高,达510HV。纳米TiO2的添加,降低了D16T微弧氧化膜层试样的摩擦系数,平均摩擦系数为0.45,明显低于不含纳米TiO2的D16T微弧氧化膜层试样的摩擦系数（0.75）。结论 加入到电解液中的纳米TiO2在微弧氧化反应过程中已进入到所形成的氧化膜层,并且填充了膜层中的微孔和裂纹,改善了膜层结构,增加了膜层厚度,显著提高了微弧氧化膜层的显微硬度和耐磨损性能。     

Microbial fuel cell-based sensor for Enterobacter sp. KBH6958 activity monitoring during hydrogen production: the effects of pH and glucose concentration

Journal of Applied Electrochemistry - A microbial fuel cell (MFC) is an electricity-generating device utilising electrochemically active microorganisms as biocatalysts. Using MFC as a biosensor to...     

Synthesis of polyamidoxime chelating ligand from polymer‐grafted corn‐cob cellulose for metal extraction

A conventional free‐radical initiating process was used to prepare graft copolymers from acrylonitrile (AN) with corn‐cob cellulose with ceric ammonium nitrate (CAN) as an initiator. The optimum grafting was achieved with corn‐cob cellulose (anhydroglucose unit, AGU), mineral acid (H₂SO₄), CAN, and AN at concentrations of 0.133, 0.081, 0.0145, and 1.056 mol/L, respectively. Furthermore, the nitrile functional groups of the grafted copolymers were converted to amidoxime ligands with hydroxylamine under basic conditions of pH 11 with 4 h of stirring at 70°C. The purified acrylic polymer‐grafted cellulose and polyamidoxime ligand were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy analysis. The ligand showed an excellent copper binding capacity (4.14 mmol/g) with a faster rate of adsorption (average exchange rate = 7 min), and it showed a good adsorption capacity for other metal ions as well. The metal‐ion adsorption capacities of the ligand were pH‐dependent in the following order: Cu²⁺ > Co²⁺ > Mn²⁺ > Cr³⁺ > Fe³⁺ > Zn²⁺ > Ni²⁺. The metal‐ion removal efficiency was very high; up to 99% was removed from the aqueous media at a low concentration. These new polymeric chelating ligands could be used to remove aforementioned toxic metal ions from industrial wastewater. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40833.     

Microwave irradiated and thermally heated olive stone activated carbon for nickel adsorption from synthetic wastewater: A comparative study

In attempt to compare the removal efficiency and yield of the activated carbon prepared using the conventional and microwave‐assisted heating is the focus of this work. Toward this olive stone (a biomass precursor) is activated using the popular activating agent potassium hydroxide. The process optimization exercise is carried out by using the standard full factorial statistical design of experiments (response surface methodology). The activated carbons prepared under the optimized conditions are compared based on the adsorption capacity and yield. The adsorption capacity was found higher using microwave heating as compared with conventional heating. The microwave heating requires significantly lesser holding time as compared to conventional heating method to produce activated carbon of comparable quality, with higher yield. The BET surface area of carbon using microwave heating is significantly higher than the conventional heating. Although the mesopore surface area of carbon is not vary significantly, the activation time, power, and nitrogen gas consumption are significantly lower than the conventional heating rendering that the activation process via microwave is more economical than that via conventional heating. The adsorption isotherm data fitted the Langmuir isotherm well and the monolayer adsorption capacity was found to be 12.0 and 8.42 mg/g for microwave and thermally heated activated carbon, respectively. Regeneration studies showed that microwave‐irradiated and thermally heated olive stone could be used several times by desorption with an HCl reagent. Both carbons can be used for the efficient removal of Ni²⁺ (>99%) from contaminated wastewater. © 2013 American Institute of Chemical Engineers AIChE J, 60: 237–250, 2014     

Structural development and magnetic phenomenon in Zn–Cr–Fe multi oxide nano-crystals

The Cr³⁺ ions doped multi-oxide ZnFe_2−xCr_xO₄ ferrite nanoparticles have been synthesized by chemical co-precipitation method. Site occupancies of Zn²⁺, Cr³⁺ and Fe³⁺ ions were analyzed using X-ray diffraction data and Buerger's method. The effect of the constituent phase variation on the magnetic hysteresis behavior was examined by saturation magnetization which decreases with the increase in Cr³⁺ content in place of Fe³⁺ ions at octahedral B-site. Typical blocking temperature (T_B) around 90 K was observed by zero field cooling and field cooling magnetization study. Room temperature Mössbauer spectra show two paramagnetic doublets (tetrahedral and octahedral sites). The isomer shifts of both doublets decrease whereas quadrupole splitting and relative area of tetrahedral A-site increases with increasing Cr³⁺ substitution. The dielectric constant (measured on compositions x=0, 0.4, 0.8 and 1.0) increases when the temperature increases as in the semiconductor. This behavior is attributed to the hopping of electrons between Fe²⁺ and Fe³⁺ ions with a thermal activation.     

Performance analysis of three advanced controllers for polymerization batch reactor: An experimental investigation

The performances of three advanced non-linear controllers are analyzed for the optimal set point tracking of styrene free radical polymerization (FRP) in batch reactors. The three controllers are the artificial neural network-based MPC (NN-MPC), the artificial fuzzy logic controller (FLC) as well as the generic model controller (GMC). A recently developed hybrid model (Hosen et al., 2011a. Asia-Pac. J. Chem. Eng. 6(2), 274) is utilized in the control study to design and tune the proposed controllers. The optimal minimum temperature profiles are determined using the Hamiltonian maximum principle. Different types of disturbances are introduced and applied to examine the stability of controller performance. The experimental studies revealed that the performance of the NN-MPC is superior to that of FLC and GMC.     

The effect of di-2-ethylhexyl phthalate on the thermo-oxidative ageing of poly(vinyl chloride)/epoxidized natural rubber blends

The effect of di-2-ethylhexyl phthalate (DOP) plasticizer on the degradation behaviour of 50/50 poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend was studied by long-term exposure to ambient conditions (27–30°C) in the laboratory. While the unplasticized blend showed obvious changes in physical properties such as hardening, loss of elasticity and embrittlement, the plasticized blend retained its properties. Thermo-oxidative ageing studies were carried out by evaluating the mechanical properties before and after ageing in an air oven at 80°C for 168 h. The relatively rapid degradation of PVC/ENR blend has been attributed to the high concentration of epoxy groups and the occurrence of ring-opening reactions to form ether crosslinks. It was found that the plasticizer confers adequate stabilization upon the addition of a certain threshold amount. The optimum amount of plasticizer required to adequately stabilize the blend is 20 phr. Above this there is a tendency for plasticizer migration to occur. The use of an antioxidant in conjunction with the plasticizer further stabilizes the blend. The general trend is of decrease in mechanical and physical properties with increase in DOP concentration. In addition, ease of processing also increases as indicated by the torque maxima and minima obtained from the Brabender plastograms.     

Mechanical and thermo-oxidative properties of blends of poly(vinyl chloride) with epoxidized natural rubber and acrylonitrile butadiene rubber in the presence of an antioxidant and a base

Being polar and compatible with poly(vinyl chloride), epoxidized natural rubber (ENR) is similar in behaviour to acrylonitrile butadiene rubber (NBR). To assess the extent of this similarity, the mechanical properties of 50/50 blends of PVC with these two rubbers were compared. Their response to thermo-oxidative ageing in the presence of an antioxidant and a base was also investigated by ageing the blends at 100°C for 7 days. Studies involving mechanical properties and FTIR were used to evaluate the extent of thermal degradation. The results revealed that blends of ENR show mechanical properties which are as good as, and in some instances better than, those of the NBR blends. However, the ENR blends with PVC are very prone to oxidative ageing. This might be attributed to the susceptibility of the oxirane group to ring-opening reactions, particularly in the presence of PVC, which yields HCl as it degrades. The amine-type antioxidant 2,24-trimethyl-1,2-dihydroquinoline (TMQ) improved the oxidative stability of both blends. This was more significant in the ENR blend, which in some cases attained stability comparable with that of NBR. The addition of a base, calcium stearate [Ca(St)₂], did not show any influence in the PVC/ENR blend, even though it was expected to curb acid-catalysed degradation. Ca(St)₂, however, improved the oxidative stability of the PVC/NBR blend. The combination of optimum amounts of TMQ and Ca(St)₂ effectively improved the tensile strength of both unaged blends, without appreciable adverse effect on elongation at break. This combination also imparted stability better than that of TMQ alone.     

Distribution of Partial Digestion Products of Hydroxypropyl Derivatives of Maize (NM), Waxy Maize (WM) and High Amylose (HA) Maize Starches

Porcine pancreatic α-amylase digests of native and hydroxypropyl derivatives of maize, waxy maize and high amylose maize starches were subjected to ethanolic fractionation into oligosaccharide and polysaccharide fractions. Both fractions of the partial digests were analysed for blue values, reducing values, total carbohydrate, average degree of polymerisation and molar substitution (MS). Distribution of hydroxypropyl groups between the fractions varied depending on starch type and level of substitution with the polysaccharide fraction being higher in MS. Blue values (BV) and average degree of polymerisation (DP) tended to decrease with digestion while reducing (RV) increased.