Properties of PVC-titania hybrid materials prepared by the sol-gel process

Hybrid materials from Polyvinyl chloride (PVC) and titania were prepared using sol-gel technique. In-situ generation of titania network in the PVC matrix was carried out by introducing required amounts of tetrapropylorthotitanate (TPOT) followed by hydrolysis/condensation of TPOT in the matrix. Homogeneous and semi-transparent films were obtained by casting and solvent evaporation. Mechanical properties of these films up to 15 wt. % titania contents were studied. The results showed an increase in the Young's modulus, length at rupture and toughness of the unplasticised PVC. However, the tensile strength and stress at break point decreased with the addition of titania contents. Thermal stability of the material was studied using dehydrochlorination (DHCl) technique and thermogravimetric analysis. The PVC samples with small amount of titania were found to be more stable as compared with the pure PVC. Received: 13 October 1997/Revised version: 22 January 1998/Accepted: 2 February 1998     

Effect of Catalysts on Effluents During Air Blowing of Asphalt

Air blowing of asphalt was performed in presence of catalysts. The effluents (distillate) obtained during air blowing were analyzed to see the effect of catalysts on them. This study investigates the effluents in detail, using physical and chemical methods. Catalysts used were metallic chlorides in varying quantities and also in combination with manganese dioxide. The aim of using different catalysts was to develop a suitable catalyst, which can perform hardening of asphalt at par with other available catalyst, at the same time keeping the effluents relatively low and free of acidic gases. These acidic gases decrease the life of the plant and cause environmental problems. During a 15 h air oxidation period, it was observed that for feed I asphalt the physical (specific gravity & viscosity) and chemical (acidity & composition) properties of the effluent oils, were effected by the catalysts. Amount of effluents were different for different catalysts. Saturate contents of the effluent were increased due to catalyst, while naphthalene and polar aromatic decreased. Effluents were free of asphaltene. The variation in the properties of effluents obtained during feed asphalts II and III air blowing, were not so distinct than with feed I. It indicates that the extent of changes in the properties of effluents depends on the composition of feedstock. Effluent oils were investigated by instrumental analytical techniques such as GLC, UV. Some of the properties of blown asphalt are also reported.     

Quality Assessment of Furnace Oil with Special Reference to Trace Metals

Furnace oil is the residual product of petroleum. All the impurities and metal content of petroleum are concentrated in it. Fluctuation in properties and contaminations, either deliberately or accidentally, are very frequent in this product. Physical and chemical test methods are used to access the quality of the furnace oil alongwith instrumental analytical methods. Various instrumental techniques such as atomic absorption spectroscopic, emission spectroscopic, and flame photometric methods have been used for determination of trace metals. A comparison of the results of trace metals has been drawn. Salt content of the furnace oil has been related to the total metal content. Sixteen imported furnace oils have been studied and compared against standard specification.     

The protein quality of some enteral products is inferior to that of casein as assessed by rat growth methods and digestibility-corrected amino acid scores

Protein digestibility and quality of six enteral nutrition products sold in Canada were studied by rat balance and growth methods. Casein+L-methionine, 0.2 g/100 g diet (control) and six enteral products (freeze-dried) were fed as the sole source of protein in diets containing 8.61-9.12 g/100 g protein (N x 6.25) to weanling and 18-mo-old rats for a period of 2 and 1 wk, respectively. A protein-free diet was also included in the feeding studies to permit calculations of true protein digestibility and net protein ratio values. Values for true digestibility of protein as determined in old rats for the control diet and the test products were 95 and 89-93%, respectively. Compared with old rats, protein digestibility values were 5-7 percentage units higher in young rats. The 2-wk relative protein efficiency ratio values (42-56%) or the relative net protein ratio values (61-74%) of the enteral products were considerably lower compared to those of the control (100). Supplementation of an enteral product with cysteine, cysteine + tryptophan, cysteine + threonine or cysteine + tryptophan + threonine caused significant improvement in protein quality; suggesting that the product was limiting in these three amino acids. The protein digestibility-corrected amino acid scores for the enteral products were 43-46, 69-75 and 86-93% by using whole egg, casein and the FAO-WHO (1991) pattern as reference proteins, respectively. The results indicate that these enteral products are inferior to casein in protein quality.     

High-performance supercapacitors based on Ni2P@CNT nanocomposites prepared using an ultrafast microwave approach

We present a one-step route for the preparation of nickel phosphide/carbon nanotube (Ni₂P@CNT) nanocomposites for supercapacitor applications using a facile, ultrafast (90 s) microwave-based approach. Ni₂P nanoparticles could grow uniformly on the surface of CNTs under the optimized reaction conditions, namely, a feeding ratio of 30:50:25 for CNT, Ni(NO₃)₂·6H₂O, and red phosphorus and a microwave power of 1000 W for 90 s. Our study demonstrated that the single-step microwave synthesis process for creating metal phosphide nanoparticles was faster and simpler than all the other existing methods. Electrochemical results showed that the specific capacitance of the optimal Ni₂P@CNT-nanocomposite electrode displayed a high specific capacitance of 854 F·g⁻¹ at 1 A·g⁻¹ and a superior capacitance retention of 84% after 5000 cycles at 10 A·g⁻¹. Finally, an asymmetric supercapacitor was assembled using the nanocomposite with activated carbon as one electrode (Ni₂P@CNT//AC), which showed a remarkable energy density of 33.5 W·h·kg⁻¹ and a power density of 387.5 W·kg⁻¹. This work will pave the way for the microwave synthesis of other transition metal phosphide materials for use in energy storage systems.     

Rainfall Extremes: a Novel Modeling Approach for Regionalization

The rainfall events of extreme magnitude over the past few decades have caused destructive damages to lives and properties, especially in the subcontinent (e.g. Pakistan, India, Bangladesh etc). Rainfall hazard maps for these areas can be of great practical and theoretical interests. In our work, we used extreme value analysis and spatial interpolation techniques to provide such maps through a combination of the Tropical Rainfall Measuring Mission Precipitation (TRMM) 3B42 product and raingauge data. This mixed approach takes advantage of both the long time series available at a limited number of stations, and the large spatial coverage of the satellite data which, instead, has a poor temporal extent. The methodology is implemented by (1) creating a unique growth curve for the homogeneous region by utilizing in-situ rainfall data and (2) mapping the parameters of intensity-duration functions for the entire length of the study area by using TRMM 3B42 product. The regional results obtained by using mixed approach and TRMM 3B42 are compared with the estimates obtained by using in-situ data. The comparison showed that the overall output of mixed approach is more consistent with what transpired by in-situ data for a pre-defined return period.