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981.
Shekhar?KumarEmail author Pranay?Kumar?Sinha U.?Kamachi Mudali R.?Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):545-549
Formation and thermal decomposition of red-oil during unit operations of nuclear fuel cycle process flowsheets is a severe
risk. In the literature, red-oil formation has been investigated thoroughly in general and in detail after Tomsk-7 incident
on 6th April 1993. However there is no information on the thermal decomposition of formed red-oil. In this work, results of
unique experiments on adiabatic thermal decomposition of red-oil, red-oil equilibrated with excess of 4N nitric acid and 100%
TBP equilibrated with excess of 4N nitric acid have been discussed. 相似文献
982.
M.?Balamurugan Shekhar?KumarEmail author U.?Kamachi Mudali R.?Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):507-510
The cross sections for the 118Sn (n, α)115Cd, 120Sn (n, α)117gCd and 120Sn (n, α)117mCd reactions have been measured in the neutron energy range of 13.5–14.6 MeV using the activation technique and a coaxial
HPGe γ-ray detector. The fast neutrons were produced by the T (d, n) 4He reaction. The neutron energies in the measurements were determined by cross section ratios for 93Nb(n,2n)92mNb and 90Zr(n, 2n)89m+gZr reactions. The results of present work were discussed and compared with theoretical calculation data, measurement results
found in the literature and with the comprehensive evaluation data in ENDF/B-VII.0, CENDL-3.1, JENDL-4.0 libraries. 相似文献
983.
Neelam?Kumari D.?R.?Prabhu P.?N.?PathakEmail author A.?S.?Kanekar V.?K.?Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):835-843
Extraction behavior of 1 × 10−2–0.1 M U(VI) from aqueous phases containing 0.86 M Th(IV) at 4 M HNO3 in 1.1 M tributyl phosphate (TBP) and 1.1 M N,N-dihexyl octanamide (DHOA) solutions in different diluents viz. n-dodecane, 10% 1-octanol + n-dodecane, and decahydronaphthalene (decalin) was studied. Third-phase formation was observed in both the extractants using
n-dodecane as diluent. There was a gradual decrease in Th(IV) concentration in the third-phase (heavy organic phase, HOP) with
increased aqueous U(VI) concentration [0.71 M (no U(VI))–0.61 M (0.1 M U(VI)) for TBP; 0.27 M (no U(VI))–0.22 M (0.1 M U(VI))
for DHOA]. The HOP volume in case of DHOA was ~2.2 times of that of TBP. Uranium concentration in HOP increased with its initial
concentration in the aqueous phase [from 1.8 × 10−2 M (0.01 M U(VI))–0.162 M (0.1 M U(VI)) for TBP; from 1.4 × 10−2 M (0.01 M U(VI))–0.14 M (0.1 M U(VI)) for DHOA] suggesting that Th(IV) was being replaced by U(VI). An empirical correlation
was developed for predicting the concentrations of uranium and thorium in HOP for both the extractants. No third-phase appeared
during the extraction of uranium and thorium from the aqueous phases employing 10% 1-octanol + n-dodecane, or decalin as diluents, and therefore, were better choices as diluent for alleviating the third-phase formation
during the reprocessing of spent thorium based fuels, and for the recovery of thorium from high-level waste solutions. 相似文献
984.
Effect of sol-gel preparation method on particle morphology in pure and nanocomposite PZT thin films
Double-scale composite lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (PZT) thin films of 360 nm thickness were prepared by a modified composite sol-gel method. PZT films were deposited from
both the pure sol and the composite suspension on Pt/Al2O3 substrates by the spin-coating method and were sintered at 650°C. The composite suspension formed after ultrasonic mixing
of the PZT nanopowder and PZT sol at the powder/sol mass concentration 0.5 g mL−1. PZT nanopowder (≈ 40–70 nm) was prepared using the conventional sol-gel method and calcination at 500°C. Pure PZT sol was
prepared by a modified sol-gel method using a propan-1-ol/propane-1,2-diol mixture as a stabilizing solution. X-ray diffraction
(XRD) analysis indicated that the thin films possess a single perovskite phase after their sintering at 650°C. The results
of scanning electron microscope (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and transmission electron
microscopy (TEM) analyses confirmed that the roughness of double-scale composite PZT films (≈ 17 nm) was significantly lower
than that of PZT films prepared from pure sol (≈ 40 nm). The composite film consisted of nanosized PZT powder uniformly dispersed
in the PZT matrix. In the surface micrograph of the film derived from sol, large round perovskite particles (≈ 100 nm) composed
of small spherical individual nanoparticles (≈ 60 nm) were observed. The composite PZT film had a higher crystallinity degree
and smoother surface morphology with necklace clusters of nanopowder particles in the sol-gel matrix compared to the pure
PZT film. Microstructure of the composite PZT film can be characterized by a bimodal particle size distribution containing
spherical perovskite particles from added PZT nanopowder and round perovskite particles from the sol-matrix, (≈ 30–50 nm and
≈ 100–120 nm), respectively. Effect of the PZT film preparation method on the morphology of pure and composite PZT thin films
deposited on Pt/Al2O3 substrates was evaluated. 相似文献
985.
Steady state analysis of a combined hybrid process consisting of a reactive distillation column, pervaporation unit, and a
distillation column is presented. This process configuration was first presented by Steinigeweg and Gmehling (2004) for the
transesterification of methyl acetate and butanol to butyl acetate and methanol. This system is characteristic for its low
reaction rate and complex phase equilibrium. Steinigeweg and Gmehling (2004) have shown that the combination of reactive distillation
and pervaporation is favourable since conversions close to 100 % can be reached with a reasonable size of the reactive section
in the reactive distillation column. The aim of this paper is to show that although high conversion can be achieved, very
complicated steady state behaviour must be expected. The presented analysis is based on mathematical modelling of a process
unit, where the steady-state analysis, including continuation and bifurcation analyses, was used. Multiple steady states were
predicted for the studied system; three steady states with conversions higher than 98 %. However, not all predicted steady
states met the maximal allowed temperature condition in the reactive section (catalyst maximal operation temperature of 393
K). The presence of multiple steady states reduces the operability and controllability of the reactive distillation column
during its start-up and during the occurrence of any variation of operating parameters because the system can be shifted from
one steady state to another one (concurrent exceeding the maximal allowed temperature) with unwanted consequences, e.g. production
loss. Therefore, design and subsequent operation of such a complicated system is an ambitious task requiring knowledge of
any possible system behaviour. 相似文献
986.
The paper deals with continuous-time nonlinear adaptive control of a continuous stirred tank reactor (CSTR). Control strategy
is based on the application of a controller consisting of a linear and a nonlinear part. The static nonlinear part is derived
as an inversion and exponential approximation of measured or simulated input-output data. Design of the dynamic linear part
is based on an approximation of nonlinear elements in the control loop by a continuous-time external linear model with directly
estimated parameters. In the control design procedure, polynomial approach with the pole assignment method was used. The nonlinear
adaptive control was tested by simulations on a nonlinear model of a CSTR with a consecutive exothermic reaction. 相似文献
987.
Gurinov AA Rozhkova YA Zukal A Čejka J Shenderovich IG 《Langmuir : the ACS journal of surfaces and colloids》2011,27(19):12115-12123
(1)H and variable-temperature (15)N NMR techniques have been used to study the effect of the gradual alumination of SBA-15 on the structure and adsorption properties of this mesoporous material. The interpretation of experimental spectra suggests that aluminum chlorhydrol most effectively reacts with silica surfaces in the confinement of the cavities of rough mesopore walls, instead of forming a homogeneous aluminum film. This first leads to a gradual filling of the cavities and finally results in aluminum islands on the inner surfaces of mesopores. In the sample with a Si/Al atomic ratio of 4.1, up to half of the inner surface area of the mesopores is covered with aluminum. The alumination produces Br?nsted acid sites attributed to silanol groups interacting with aluminum but does not affect the proton-donating ability of isolated silanol groups. At high Si/Al ratios, the surface contains only one type of Lewis site attributed to tetracoordinated aluminum. At lower Si/Al ratios, Lewis acid sites with a lower electron-accepting ability appear, as attributed to pentacoordinated aluminum. The numerical values of the surface densities of all chemically active sites have been estimated after annealing at 420 and 700 K. We were surprised to observe that gaseous nitrogen can occupy Lewis acid sites and hinder the interaction of the aluminum with any other electron donor. As a result, aluminated surfaces saturated with nitrogen do not exhibit any Br?nsted or Lewis acidity. At room temperature, it takes days before pyridine replaces nitrogen at the Lewis acid sites. 相似文献
988.
Vukomanović M Skapin SD Poljanšek I Zagar E Kralj B Ignjatović N Uskoković D 《Colloids and surfaces. B, Biointerfaces》2011,82(2):414-421
The novel concept of a simultaneous, controlled release of a drug and a prodrug with different physico-chemical properties was applied in order to prolong the release period of antibiotics and estimate their high local concentrations, which are the necessary preconditions for the treatment of some chronic infection diseases. For this purpose poly(D,L-lactide-co-glycolide)/hydroxyapatite (PLGA/HAp) core-shell nanostructures were used as the carrier of clindamycin-base, as a drug, and clindamycin-2-phosphate, as a prodrug model. As a result, a two-step release was observed: the controlled release of the more soluble phosphate form and the sustained release of the less-soluble base form of clindamycin, resulting in a high overall concentration of the released drug during the period of 30 days in vitro. The HAp phase within the PLGA core-shells, applied as a drug carrier, delayed the process of the degradation of the polymer; however, the presence of the drug affected the process of degradation and this influence was the dominant factor in the control over the degradation of the polymer phase of PLGA/HAp and the consequent kinetics of the drug release. 相似文献
989.
Vukomanović M Zavašnik-Bergant T Bračko I Skapin SD Ignjatović N Radmilović V Uskoković D 《Colloids and surfaces. B, Biointerfaces》2011,87(2):226-235
A step-by-step analysis of the formation and the drug loading of the poly(D,L-lactide-co-glycolide)/hydroxyapatite (PLGA/HAp) composite was carried out in a perspective of the following parameters: the structure, the morphology and the adsorption/desorption properties of the composite's bioceramic part. The authors demonstrated the importance of the material's capacity to form a fine dispersion of solid HAp particles, as an initial step, for the further loading of the drug and for the formation of the core-shell structures. The nanometer-sized rods of HAp have the capacity of ensuring a rapid adsorption and a controlled desorption of the drug from their surface, and they can act as a nucleating site for the formation of polymeric cores. Each component of this material was labeled with fluorescence dye, which enabled an insight into the distribution of the components in the core-shells that were obtained as the final outcome. Such an analysis showed a high level of uniformity among the cores enclosed within polymeric shells. From a practical perspective, the labeling of each component of the composite can be regarded as an additional functionality of the material: labeling can enable us to monitor its action during the healing process. This ability to be easily detected is expected to enhance the procedure for the controlled delivery of antibiotics after their local implantation of carriers loaded with the antibiotic and to provide more careful control over this process. 相似文献
990.
R.?Venkata Krishnan K.?NagarajanEmail author S.?Clement Ravichandar T.?V.?Prabhu G.?Ravisankar K.?V.?Kasiviswanathan 《Journal of Sol-Gel Science and Technology》2011,59(3):394-403
Sol–gel based fuel fabrication processes have the potential to be the nuclear fuel fabrication processes in the future. Hence
development of sol–gel technology for nuclear fuel fabrication is being the pursued in the Department of Atomic Energy in
India. As a part of the efforts, a laboratory scale facility for fabrication of test fuel pins for irradiation in the Fast
Breeder Reactor (FBTR), Kalpakkam has been set up at the Indira Gandhi Centre for Atomic Research, Kalpakkam, India. These
fuel pins will be vibropacked with sol–gel derived microspheres or stacked with pellets obtained by compaction of sol–gel
derived microspheres. The facility is aimed at demonstration of the remote operation of the fuel pin fabrication process through
the sol–gel route. A capsule containing three test pins from this facility will be irradiated in FBTR. The design features
of the facility and the test fuel pins are described in this paper. 相似文献