Preliminary study on calcium aluminosilicate glass as a potential host matrix for radioactive 90Sr--an approach based on natural analogue study

Given the environmental-, safety- and security risks associated with sealed radioactive sources it is important to identify suitable host matrices for (90)Sr that is used for various peaceful applications. As SrO promotes phase separation within borosilicate melt, aluminosilicate bulk compositions belonging to anorthite-wollastonite-gehlenite stability field are studied in this work. Tests for their homogeneity, microstructural characteristics and resistance to phase separation narrowed the choice down to the composition CAS11 (CaO=35 wt%, Al(2)O(3)=20 wt%, SiO(2)=45 wt%). We find that up to 30 wt% SrO can be loaded in this glass without phase separation (into Ca, Sr-rich and Sr-poor, Si-rich domains). Leaching behaviour of the glasses differs depending on the content and distribution of Sr. In general, the elemental leach rates determined from conventional PCT experimental procedure yield values better than 10(-7)gcm(-2)day(-1) for both CAS11 base glass as well as SrO doped glass. It was noted that leach rates calculated on the basis of Ca(2+) and Sr(2+) were of the same order and bit higher compared to those calculated on the basis of Si(4+) and Al(3+). During accelerated leaching tests, zeolite and zeolite+epidote were found to have developed on CAS11 base glass and SrO doped glasses respectively. The Sr bulk diffusion coefficients is found to vary from ～ 10(-15) to 10(-13)cm(2)/s at temperature intervals as high as 725-850°C. Based on the experimental observations, it is suggested that CAS11 glass can be used as host matrix of (90)Sr for various applications of radioactive Sr-pencils.     

Comparative Study of Sterol Ester Synthesis using <Emphasis Type=Italic>Thermomyces Lanuginosus</Emphasis> Lipase in Stirred Tank and Packed-Bed Bioreactors

A comparative study was done on the production of different sterol esters using a stirred tank batch reactor (STBR) and packed bed reactor (PBR) using Thermomyces lanuginosus (Lipozyme TLIM) enzyme, a commercially immobilized lipase. Different oils were used as the sources of particular fatty acids, e.g., fish oil for n-3 polyunsaturated fatty acids (n-3 PUFA), linseed oil for alpha linolenic acid (ALnA) and mustard oil for erucic acid. Reaction parameters, such as substrate molar ratio, reaction temperature and enzyme concentration, were standardized in the STBR and maintained in the PBR. To provide equal time of residence between the substrate and enzyme in both the reactors for the same amount of substrates, the substrate flow rate in the PBR was maintained at 0.27 ml/min. Thin layer chromatography was used to monitor the reaction, and column chromatography was used to determine the product yields. Fatty acid compositions of the esters were determined by gas chromatography. The study showed that the packed bed bioreactor was more efficient than the batch reactor in sterol-ester synthesis with less migration of acyl groups.     

Stearic acid as coupling agent in fly ash reinforced recycled polypropylene matrix composites: Structural,mechanical, and thermal characterizations

Two industrial wastes, fly ash (FA) and recycled polypropylene (RPP) were used to prepare a value‐added, sustainable, low cost composite material. Improving the interfacial interaction between the hydrophobic RPP matrix and the hydrophilic FA particles is important to get a good combination of properties. In order to tailor the interface, stearic acid was used as the coupling agent. The FA particles were coated with a saturated fatty acid, stearic acid (SA), in different weight % like 1, 2, 3, and 5. The SA coated fly ash particles were incorporated as filler in RPP matrix composites by melt mixing in 1 : 1 weight ratio. The composites were tested for their flexural properties, impact behavior, dynamic mechanical properties, fracture surface analysis, X‐ray diffraction (XRD) study, and differential scanning calorimetry (DSC). An increase in flexural modulus and impact strength was observed in the stearic acid coated FA/RPP composites. In 1 wt % SA treated FA/RPP (RFASA1) composites, a significant increase in glass transition temperature was observed along with an increase in crystallinity. A green, renewable, inexpensive chemical like stearic acid was thus found to be an effective coupling agent in fabrication of a composite with 50 wt % filler loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1996–2004, 2013     

CeO2–YO1.5–NdO1.5 system: An extensive phase relation study

The sub-solidus phase relations in the CeO₂–YO_1.5–NdO_1.5 system have been studied. About 45 compositions in the series Ce_1?x(Y_0.70Nd_0.30)_xO_2?0.5x, Y_1?x(Ce_0.50Nd_0.50)_xO_1.5+0.25x and Nd_1?x(Ce_0.55Y_0.45)_xO_1.5+0.275x were prepared and characterized by powder XRD. In the Ce_1?x(Y_0.70Nd_0.30)_xO_2?0.5x series, there was a gradual transformation from the defective F-type cubic lattice to an ordered C-type phase with increasing x, whereas in the Y_1?x(Ce_0.50Nd_0.50)_xO_1.5+0.25x series, the C-type cubic lattice of yttria was retained over the entire range. In the Nd_1?x(Ce_0.55Y_0.45)_xO_1.5+0.275x system, the compositions with NdO_1.5 content greater than 95 mol% showed coexistence of hexagonal, monoclinic and cubic phases. A biphasic region of monoclinic and C-type cubic phases was observed as NdO_1.5 decreases from 90 to 70 mol%. All the compositions below 70 mol% NdO_1.5, were found to be C-type cubic solid solutions. The phase relations are distinctly characterized by an extensive range of cubic solid solutions, stable under the slow-cooled conditions. To the best of our knowledge, this is the first detailed sub-solidus study reported in CeO₂–YO_1.5–NdO_1.5 system.     

Lauric acid coated fly ash as a reinforcement in recycled polymer matrix composites

Sustainable composites were developed from fly ash (FA) and recycled polypropylene (R) with lauric acid (LA) as the coupling agent. The FA particles were surface‐coated with 1, 2, 3, and 5 wt % LA, and the coating on the FA particles was verified by transmission electron microscopy and Fourier transform infrared spectroscopy. R and LA‐coated FA particles were melt‐mixed in a 1:1 weight ratio to achieve a high‐filler‐loaded composite. The flexural, impact, nanoindentation, and fracture surface analyses were carried out to examine the properties of the composites. The flexural strength and modulus values increased in the 2 wt % LA‐coated FA/R composites by 6 and 50%, respectively, compared to the values of the uncoated FA/R composites, whereas the impact strength increased considerably by 119% in the 1 wt % LA‐coated composites. Nanoindentation tests also showed an increase in the mechanical properties in the case of the 1 and 2 wt % LA‐coated composites in comparison to the uncoated ones. Fracture surface studies done by scanning electron microscopy revealed improved interfacial interactions between the filler and matrix in the presence of the LA coupling agent. X‐ray diffraction (XRD) studies indicated reorientations of the polymer chains in the presence of different concentrations of the LA coupling agent; this resulted into different crystallinities and crystallite sizes. Differential scanning calorimetry showed a significant difference in the crystalline peaks of the composites, and this corroborated well with the XRD observations. LA, thus, significantly influenced the structural properties of the composites, and this, in turn, influenced their mechanical and thermal properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41586.     

Continuous Process for the Production of Hexafluoroisopropanol

There has been a renewed interest in the design of catalytic reactors to reduce transport limitations. Towards this goal, a novel single fluid-phase recirculating packed bed reactor concept has been developed and demonstrated for the hydrogenation of hexafluoroacetone to hexafluoroisopropanol, a precursor to Sevoflurane, used as an inhalation anesthetic, in the presence of a Ni/Al₂O₃ catalyst.

     

Continuous Process for the Production of Hexafluoroisopropanol

There has been a renewed interest in the design of catalytic reactors to reduce transport limitations. Towards this goal, a novel single fluid-phase recirculating packed bed reactor concept has been developed and demonstrated for the hydrogenation of hexafluoroacetone to hexafluoroisopropanol, a precursor to Sevoflurane, used as an inhalation anesthetic, in the presence of a Ni/Al₂O₃ catalyst.