Effect of nano-ZnO addition on the silicone-modified alkyd-based waterborne coatings on its mechanical and heat-resistance properties

A silicone-modified alkyd-based waterborne coating was developed using hexamethylmethoxymelamine (HMMM) as crosslinking agent and para-toluene sulphonic acid (p-TSA) as catalyst. The crosslinking ratio for resin and HMMM was fixed to 70:30, based on FTIR and DSC studies. Nano-ZnO particles were added to this system in different concentrations. The coatings with nano-ZnO particles were characterized using FTIR and DSC. The nano-composite coatings were applied on mild steel panels and were cured at 130 °C for 30 min. The coatings were evaluated for their mechanical and heat-resistance properties. They were exposed to 350 °C for 10 min followed by water quenching. The process was repeated for 10 cycles. Heat-resistance property of the coatings was examined by TGA. Also, surface morphological changes were assessed using SEM and optical microscopy. It was found that the heat-resistance and mechanical properties of the coatings improved significantly as a function of nano-ZnO addition.     

新型无VOC可再生成膜助剂

特殊的高纯度脂肪酸酯及其混合物可用于制备较低气味,无VOC,可再生的成膜助剂.这种成膜助剂可以提高极低VOC涂料中乳液的效果.实验证明:与非再生成膜助剂相比,该新产品不仅能降低配方的综合成本,还能明显提高性能.     

Copper remediation by Eichhornia spp. and sulphate-reducing bacteria

Eichhornia spp. biomass was collected from Chandola Lake, Ahmedabad, Gujarat, India. Point of zero charge of the biomass was pH 7.3. Flask study showed pH 5 and 2–3 h contact time as optimum conditions for copper sorption with 67.25% copper removal. At the end of 24 h of contact time, copper removal reached to 85.0%, from 100 ppm copper containing solution. Copper loading capacity of the biomass ranged between 9.9 and 28.5 mg g^?1 of biomass. To understand the interaction among pH, temperature, presence of nickel and zinc in the system, 2⁴ factorial experiment was performed. Under the experimental conditions pH and interactions between pH–nickel, temperature–pH and temperature–pH–nickel–zinc were found to be significant with 60–74.7% copper removal. Langmuir isotherm was better fit as compared to Freundlich isotherm and pseudo-second order equation gave R² of 0.999 for biosorption kinetic of Eichhornia biomass. Reactor study showed 90% overall copper removal from 24 L of copper containing waste studied and sulphate-reducing bacteria played a significant role. SEMquant element analysis showed increase from 41.66% to 53.93%, 1.02–19.73% and 0.0–12.39% of chloride, aluminium and copper respectively in the loaded biomass as compare to unexposed biomass.     

Oxidative cyanide-free cyanation on arylboronic acid derivatives using aryl/heteroaryl thiocyanate using novel IL-PdCl4 catalyst under mild condition

An efficient and simple method is reported for the cyanation on arylboronic acid using various simple/indole thiocyanates using a new IL-PdCl₄ catalyst. The cascade process involves a coupling reaction without any additive to give a wide range of cyanide derivatives. Cyanation on various arylboronic acids underwent smoothly affording the corresponding arylnitriles in good to high yields.     

Case study of a dust storm over Hyderabad area, India: its impact on solar radiation using satellite data and ground measurements

According to the Earth Observatory dust outbreaks are considered as natural hazards, which affect the ecosystems and human life. The main objective of this study is to assess and monitor the movement of aerosols and pollutants from local or other sources, both natural and anthropogenic, using a combination of ground-based monitoring and satellite data. The turbid and polluted atmosphere in the densely-populated area of Hyderabad, India is further degradated from dust outbreaks originated from Thar desert. A dust event occurred during 10th to 11th April 2006 in the northwest region of India; its plume substantially spreaded across the downwind direction affecting the study region. Using both irradiance measurements and satellite data this dust event is investigated. The analysis shows a significant change in Aerosol Optical Depth (AOD), Aerosol Index (AI) and aerosol-particle size during the dust event. The Aerosol Optical Depth in the dusty day is about 0.2 higher than the previous non-dusty days, while the Angstr?m exponent rapidly decreases when the dust plume affected the study area. The surface PM concentrations show enhanced values during the dusty day directly influenced by the dust deposition. There is also a remarkable decrease in ground-reaching global radiation, UV erythemal (UV(ery)) and other irradiance components. The analysis suggested that the use of the diffuse-to-direct-beam ratio is the most appropriate parameter for the dust monitoring since its values at the longer wavelengths are not affected by the solar zenith angle.     

Plasma Spraying of Lanthanum Chromite Films for Solid Oxide Fuel Cell Interconnection Application

This paper discusses a novel plasma-spraying process for depositing dense LaCrO₃-based interconnection for solid oxide fuel cells (SOFCs). Calcium aluminate was mixed with LaCrO₃ in a slurry containing PVA binder and spray dried to form free-flowing agglomerates. These free-flowing agglomerates were plasma sprayed onto a porous substrate of doped LaMnO₃ and then heat-treated to form a gas-tight and electrically conducting interconnection. Samples of the plasma-sprayed interconnection were characterized for morphology, phase constituents, and coefficient of thermal expansion, as well as electrical resistivity and oxygen nonstoichiometry at 1000°C in the P O₂ range from 1 to} 1× 10^-16 atm. The calcium aluminate additive was found to facilitate densification of the interconnection, most likely through the formation of low-temperature melting phase(s) in the system Ca–Cr–Al–O. A SOFC with such a plasma-sprayed interconnection was fabricated and electrically tested. This cell exhibited good electrical performance, and the interconnection was stable under fuel cell operation conditions.     

“Effect of nano-ZnO particles on the corrosion behavior of alkyd-based waterborne coatings”

A nano-composite was formed by incorporating nano-ZnO in a specially developed alkyd-based waterborne coating to different loading levels. The nano-ZnO based composite coatings were applied on mild steel substrate by dipping. The coated panels were subjected to various test environments like salt-spray, humidity, UV and mechanical tests like scratch and abrasion. The improvement in electrochemical performance and mechanical properties of the composite coatings were evaluated using various analytical techniques. FTIR technique was used to investigate the interaction between nano-ZnO particles and the polymer functionalities. Differential scanning calorimetry (DSC) was done to study the curing behavior of nano-composite coatings. SEM and AFM were used to investigate dispersion of nano-ZnO particles and the changes in the surface behavior of the coatings before and after exposure to the test environment. The result showed that, with increase in the concentration of nano-ZnO there was an improvement in the corrosion resistance, UV resistance and mechanical properties of the coatings indicating the positive effect of addition of nano-ZnO particles in the coatings.     

Study on electrochemical behavior of Nano‐ZnO modified alkyd‐based waterborne coatings

A nano‐composite coating was formed using nano‐ZnO as pigment in different concentrations, to a specially developed alkyd‐based waterborne coating. The nano‐ZnO modified composite coatings were applied on mild steel substrate by dipping. The dispersion of nano‐ZnO particles in coating system was investigated by scanning electron microscopic and atomic force microscopic techniques. The effect of the addition of these nano‐pigments on the electrochemical behavior of the coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy. Coating modified with higher concentration of nano‐ZnO particles showed comparatively better performance as was evident from the pore resistance (R_po) and coating capacitance (C_c) values after 30 days of exposure. In general, the study showed an improvement in the corrosion resistance of the nano‐particle modified coatings as compared with the neat coating, confirming the positive effect of nano‐particle addition in coatings. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Controlled modification of Pt/Al2O3 for the preferential oxidation of CO in hydrogen: A comparative study of modifying element

The catalytic performance of a series of Pt/Al₂O₃ catalysts, modified with Cr, Mn, Fe, Co, Ni, Cu and Sn, has been tested for the preferential oxidation of CO in hydrogen. The promoters were deposited onto the surface of a 5 wt.% monometallic Pt/Al₂O₃ catalyst using a controlled surface approach, to give a nominal promoter:Pt surface atomic ratio of 1:2 (corresponding to typically 0.15–0.25 wt.% of the promoting metal). The aim of this approach was to selectively create the Pt-promoter oxide interfacial sites considered to be important for the non-competitive dual-site mechanism proposed for such promoted catalysts. In this mechanism the promoting oxide is believed to act as an active oxygen provider, providing oxygen for the oxidation of the CO on the Pt. The catalysts were characterised using TEM, EDX, ICP-AES and CO chemisorption and results suggest that the promoter was successfully deposited on to the Pt surface. Even at the low loadings of promoter used, significant enhancement was observed in the catalytic performance of the PROX reaction in a simulated reformate mixture, for the Fe- and Co-promoted catalysts in particular (and to a lesser extent the Mn, Sn, Cu- and Ni-promoted catalysts), highlighting the successful preparation of the Pt-promoting metal oxide interfacial sites. The Mn-promoted catalyst, however showed no enhancement in the absence of water suggesting that the form of the promoting metal oxide may be particularly important for promotion of Pt for the PROX reaction.