Purification of 89Sr from FBTR irradiated Yttria target by extraction chromatography using HDEHP impregnated XAD-7 resin

89Sr is used in bone pain palliative care of cancer patients and the same is being produced presently via the 89Y(n, p)89Sr reaction by irradiating yttria target in Fast Breeder Test Reactor (FBTR). An efficient separation method was standardized for the removal of bulk yttrium target by extraction chromatography using di(2-ethylhexyl) phosphoric acid (HDEHP) impregnated on XAD-7 resin. In the present paper, the extraction behavior of Sr(II) and Y(III) was studied as a function of the concentration of nitric acid in the aqueous phase and concentration of HDEHP in the resin phase. The separation of Sr(II) and Y(III) was standardized using the above resins and the method was subsequently applied satisfactorily for the removal of yttrium from the dissolver solution of FBTR irradiated yttria pellet towards the purification of 89Sr. A baseline separation of 89Sr and Y was achieved. Leaching and breakthrough capacity studies were evaluated for the resins and it was established that the stability and capacity of the resins were satisfactory. The breakthrough capacity was found to be 12 mg Y(III) per gram of the HDHEP resin whereas the leaching studies established that the resins are stable for multiple cycle of operations.

Nanogel-Based Filler-Matrix Interphase for Polymerization Stress Reduction

A novel filler-resin matrix interphase structure was developed and evaluated for dental composite restoratives. Nanogel additives were chemically attached to the filler surface to use this created interphase as a potential source of compliance to minimize stress development during polymerization. In addition, we evaluated the effects of free nanogel dispersion into the resin matrix, combined or not with nanogel-modified fillers. Nanogels with varied characteristics were synthesized (i.e., size, 5 and 11 nm; glass transition temperature, 28 °C to 65 °C). Glass fillers were treated with trimethoxyvinylsilane and further reacted with thiol-functionalized nanogels via a free radical thiol-ene reaction. γ-Methacryloxypropyltrimethoxysilane-surface treated fillers were used as a control. Composites were formulated with BisGMA/TEGDMA resin blend with 60 wt% fillers with nanogel-modified fillers and/or free nanogel additives at 15 wt% in the resin phase. Polymerization kinetics, polymerization stress, volumetric shrinkage, and rheological and mechanical properties were evaluated to provide comprehensive characterization. Nanogel-modified fillers significantly reduced the polymerization stress from 2.2 MPa to 1.7 to 1.4 MPa, resulting in 20% stress reduction. A significantly greater nanogel content was required to generate the same magnitude stress reduction when the nanogels were dispersed only in the resin phase. When the nanogel-modified filler surface treatment and resin-dispersed nanogel strategies were combined, there was a stress reduction of 50% (values of 1.2 to 1.1 MPa). Polymerization rate and volumetric shrinkage were significantly reduced for systems with nanogel additives into the resin. Notably, the flexural modulus of the materials was not compromised, although a slight reduction in flexural strength associated with the nanogel-modified interphase was observed. Overall, modest amounts of free nanogel additives in the resin phase can be effectively combined with a limited nanogel content filler-resin interphase to lower volumetric shrinkage and dramatically reduce overall polymerization stress of composites.

Real time monitoring of the curing degree and the manufacturing process of fiber reinforced composites with a carbon nanotube buckypaper sensor

A flexible and highly sensitive carbon nanotube buckypaper (BP) as a sensing layer was embedded within composite for cure monitoring applications. BP sensor can monitor the resin phase transition and resin cure degree during composite manufacturing.

Highly-filled hybrid composites prepared using centrifugal deposition

Natural composites of high filler content, such as nacre, a composite comprised of 95–99% w/w aragonite layers, have been of interest due to their hardness, strength and toughness. High filler content composites have been prepared synthetically, although due to viscosity and processing requirements, the filler content was limited compared with natural systems. In this paper we describe hybrid high filler content composites prepared to be biomimetic of nacre. Development of processing conditions increased the filler content from 50% w/w using a laboratory stirrer to obtain hybrid composites with 77–86% w/w filler content, prepared by centrifugal deposition and hot compression molding techniques. Both methods were very different from natural formation from layer-by-layer (LBL) construction, however, the composites formed were of high filler content approaching the level in nature. The composites exhibited high modulus and strength, although deformation at break was low, consistent with highly filled materials. Glass transition of the resin phase was increased slightly, while damping was decreased by filler content. Surface morphology of the fractured composite showed a layered structure of well dispersed fillers with minute voids scattered evenly, indicating that the composite was effectively compacted.

Speciation of Selenium in Environmental Samples by Solid-Phase Spectrophotometry Using 2,3-Dichloro-6-(2,7-dihydroxy-naphthylazo)quinoxaline

Solid-phase spectrophotometry was applied to determination of trace amounts of selenium (Se) in water, soil, plant materials, human hair, and a cosmetic preparation (lipstick). Se(IV) was sorbed in a dextran type lipophilic gel as a complex with 2,3-dichloro-6-(2,7-dihydroxy-naphthylazo)quinoxaline (DCDHNAQ), whereas Se(VI) was determined after boiling in HCl for 10 min to convert Se(VI) to Se(IV). Resin phase absorbances at 588 and 800 nm were measured directly, which allowed the determination of Se in the range of 0.2–3.3 μg/L with an RSD of 1.22%. The influences of analytical parameters including pH of the aqueous solution, amounts of DCDHNAQ, and sample volume were investigated. The molar absorptivities were found to be 1.09 × 106, 4.60 × 106, and 1.23 × 107 L/mol cm for 100, 500, and 1000 mL, respectively. The LOD and LOQ of the 500 mL sample method were 110 and 360 ng/L, respectively, when using 50 mg dextran type lipophilic gel. For a 1000 mL sample, the LOD and LOQ were 60 and 200 ng/L, respectively, using 50 mg of the exchanger. Increasing the sample volume enhanced the sensitivity. No considerable interferences were observed from other investigated anions and cations on the Se determination.

A Novel Approach Based on Polymerization-Induced Phase Separation to Prepare Carbon Monolith with Oriented Flat Porous Structure

A novel approach has been developed to fabricate an oriented flat porous carbon (OFPC) by combining the polymerizationinduced phase separation and pyrolysis (PIPSP) and the directional compressive deformation (DCD). At first, an elastic body in the shape of cylinder is obtained by controlling the polymerization degree of resin, and then the application of symmetrical axial pressures results in the directional deformation of two interconnected phases (of a polymerized resin phase and a poreforming agent phase) in the elastic body. Then the elastic deformed body is transformed to the rigid deformed body by precuring and further to the cured body by curing. At last, the cured body is pyrolyzed to form an OFPC. The pressures are removed after precuring. The pores in the OFPC are survived as the discs in the radial direction. Both flat pores and carbon skeletons in the OFPC are oriented toward a radial direction. The OFPC has comparable pore volume with a normal porous carbon, which is fabricated by the PIPSP with same process except for the application of the DCD.