Pu Solution Research Articles

Effect of processing methods on the electrical conductivity properties of silver-polyurethane composite films (Experimental and numerical studies)

This research investigates the electrical properties of micro silver polyurethane (Ag-PU) composite films with different degrees of agglomeration. Ag-PU composite films were prepared by adding micro silver particles (<3.5 μm) into the thermoplastic PU matrix using a solution mixing method, followed by spin-coating or casting techniques. For some composite preparation, the silver solution was shear-mixed in an ultrasonic bath before being added to the PU solution to obtain higher filler dispersion within the polymer matrix. This method produced several composite films with variable degrees of silver aggregation with concentrations from 0 to 14 vol%. All composites showed only electrical conductivity through thickness when compressed under pressure in a range from 0.5 to 20 kPa. Generally, the percolation threshold and conductivity values of the composite film prepared by spin-coating were lower than those of the casting composite. The maximum conductivity value found in these composites was about 2.45 S/m. All composites’ electrical performance was numerically simulated using the finite element analysis method based on the representative volume element model (FE-RVE) with Digimat software. A correlation was observed between the experiments and those simulations. A semi-analytical model was used to estimate the composite electrical parameters.

Is octavalent plutonium really formed during oxidation in alkaline aqueous solutions?

Abstract The solution, containing 2 M NaOH and 4.8 mM Pu(VI) mainly in ionic-dispersed phase, becomes dark blue during 2–3 min under ozonation. The absorption spectrum of the solution in the visible range coincides with the well-known absorption spectrum of Pu(VII). The addition in Pu(VII) solution of the aliquot of Pu(VI) solution reduces the absorbance of the solution at any wave length in proportion to dilution. Consequently there is no the influence of Pu(VI) on the absorption spectrum of Pu(VII). Thus, it is become obvious no Pu(VIII) formed in the course of ozonolysis of Pu(VII) alkaline solution. Additionally, crystalline Pu(VII) and Np(VII) compounds were synthesized, their electron absorption spectra were measured and compared with the ones of alkaline solutions. A similar structure of the spectra also indicates a heptavalent oxidation state of neptunium and plutonium in the synthesized crystalline compounds. Thus, the experimental results of this work, along with an analysis of the experimental results of other authors, presented in this work, make it possible to definitely conclude that at present time the highest of the known oxidation states of plutonium oxidation in aqueous solutions is the heptavalent state and all statements about the production of octavalent plutonium in aqueous solutions should be considered as unreasonable.

Multifunctional fireproof electromagnetic shielding polyurethane films with thermal management performance

A multifunctional polyurethane film (PU) with superior electromagnetic shielding performance, joule heating performance, thermal conductivity and flame retardancy has been carefully designed. The ammonium polyphosphate (APP) wrapped with conductive MXene (MAPP) is prepared by microencapsulation technology and added in PU solution for enhancing the electric conductivity of PU/graphite fiber (GF) film. The three-dimensional (3D) conductive network composed of GF and MAPP promotes electron transmission efficiency and electromagnetic (EM) wave dissipation through multiple absorbtion and reflection. Compared with the PU/GF film, the electric conductivity and thermal conductivity of PU/GF/MAPP film enhanced by 57.7% and 59.3%, respectively. What’s more, the PU composite film shows excellent mechanical properties, joule heating performance and high fire safety performance. Therefore, the prepared multifunctional PU film demonstrates excellent performance, and has broad application prospects in EMI shielding and thermal management of advanced microelectronic systems.

Adsorption of Plutonium onto Several Natural Sediments.

The adsorption of plutonium (Pu) onto several natural sediments was studied using batch experiments to determine the different factors influencing Pu adsorption. These factors include the possible effect of different methods for adding Pu solution, the initial oxidation state of Pu, the particle size of the sediments, the pH, and the ionic strength of solution. The method used for adding Pu solution greatly influenced the species of Pu in sediment-groundwater systems and the adsorption behavior of Pu onto the sediments. Initial oxidation state of Pu, clay mineral content, particle size of sediment, pH, and ionic strength all appear to impact adsorption. The sediments preferred to adsorb Pu(IV) rather than Pu(V). The adsorption of Pu depended on the particle size and clay mineral content of the sediments; the higher the clay mineral content and the smaller the particle size, the more adsorption for Pu. The insoluble species of Pu formed in sediment-groundwater systems at pH 9.3 resulted in the decrease of adsorption capacity. The adsorption capacity increased with pH increasing at pH < 9. Ion exchange was the dominant mechanism for Pu adsorption onto the sediments at pH < 7.5. It appeared that the ionic strength had a stronger influence on adsorption capacity than pH.

Highly efficient uptake of tetravalent actinide ions from nitric acid feeds using an extraction chromatography material containing tetra-n-butyl diglycolamide and a room temperature ionic liquid

An extraction chromatography (XC) material containing N,N,N’,N’-tetra-n-butyl diglycolamide (TBDGA) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide (C4mim∙NTf2), a room temperature ionic liquid, was used for the uptake of the tetravalent actinide ions Th(IV), Np(IV), and Pu(IV) from nitric acid feed solutions. The uptake of the metal ions followed the trend: Th(IV) < Np(IV) < Pu(IV), which is the same as that of their ionic potential values. While a decrease in the Np(IV) and Pu(IV) uptake was seen with increasing HNO3 concentration at lower acidities, an opposite trend was observed at higher acidities. Th(IV) uptake was not affected with the acid concentration. In view of the very high uptake and its importance in the nuclear fuel cycle, the major part of the studies was carried out with Pu(IV) ion. The loaded Pu(IV) was back extracted from the XC material using a mixture of 0.5 M oxalic acid and 0.5 M nitric acid. The Pu(IV) uptake by the XC material was fitted into different kinetic and isotherm models. The results conformed to the pseudo-second order kinetic model and the Langmuir monolayer sorption model. Column studies were carried out using a feed having 1.6 mg/L Pu solution in 3 M HNO3. While the breakthrough was obtained after passing ca. nine bed volumes, a sharp elution peak was obtained with >99% recovery in about seven bed volumes.

Improving ballistic performance of Kevlar fabrics by resin treatment

The aims of our investigation are to increasing inter-yarn friction by using polyurethane resin for superior ballistic protection without affecting the weight. In our concentration, we have used three different resin impregnated (25 × 25 cm) (Type-A), (4.5 × 4.5 cm) (Type-B), (9 × 9 cm) (Type-C) structure to treat our Kevlar fabrics and 12% wt. PU solution as resin. Grounded on our three different resin-impregnated fabric, we have been evaluated the weight increase percentage to analyze our core objectives maintaining the less weight escalation ratio with better ballistic performance. As the resin impregnation amount increases, the yarn or fiber dimensions lead to fabric stiffness. Later on, the yarn pull-out installation was created and the yarn (single and multiple) pullout tests were performed on both plain and resin impregnated structures to find the differentiation. The result of the investigation shows high-density resin-impregnated fabric indicates a higher pull-out force contrasted with those of low-resin impregnated fabric structure. Fabric displacement at max. Force during multiple-end pull-out indicated a higher fabric displacement (mm) rate contrasted with that of the single pull-out. Optical microscopic examination is done to observe the progressions on pulled out regions. During our observation, no implication variety was found in the surface at a specified loading rate except adjacent yarn displacement grounded on the amount of yarn pulled out. Utilization of resin impregnation builds the commitment of more yarns as the slippage of yarns is limited thus leads to the higher energy required rate. Finally, by ballistic perforated impact parameters, it is affirmed that expanding inter-yarn friction can improve ballistic performance of fabrics. Ultimately, it is concluded in the way that these new ballistic resin-impregnated structures come up with higher inter yarn friction, low expense, less weight, considerable stiffness of the fabric and the reliable ballistic performance on the finished result.

Preparation and properties of silanized functionalized graphene/polyurethane composites

Graphene oxide (GO) was prepared from a modified method of Hummers, then the GO was modified by γ-glycidoxypropyltrimethoxysilane (KH560) and reduced by hydrazine hydrate. The silylated reduced graphene oxide (KRGO) was obtained. The KRGO/polyurethane (PU) composites were prepared by solution mixing method using the KRGO as the filler and PU solution as the matrix. The KRGO and KRGO/PU composites were systematically characterized. The structure and morphology characterization showed that the KRGO was uniformly dispersed in PU solution by covalent bonding. The interlayer distance of the graphene increased from 0.79 to 0.95 nm after modification. The KRGO could provide a good compatibility with the PU. The thermal stabilities of the KRGO/PU composites are increased with the increasing addition of KRGO. At the KRGO content value of 1 wt.%, the thermal decomposition temperature on 10% weight loss was approximately 47 °C higher than that of the pure PU.

Controlled Potential Coulometry for the accurate determination of plutonium in the presence of uranium: The role of sulfate complexation

Controlled Potential Coulometry (CPC) is generally regarded as one of the most accurate analytical methods available for the quantification of plutonium (Pu) in acidic aqueous solutions. With a growing use of mixed oxide nuclear fuel, there has been an interest in the technique’s applicability to the analysis of Pu in the presence of uranium (U). Expanding on previous studies, the work presented herein demonstrates the highly accurate CPC analysis of Pu in mixed solutions (Pu + U) containing large quantities of U (U:Pu up to 100:1) as well as establishing the role played by sulfate anions during the analyses.By combining experimental results with speciation simulations, it is shown that the introduction of U in mixed Pu + U solutions is accompanied by increases in sulfate ions in the nitric acid medium which complex unequally with the different Pu cations in solution. The anions’ stronger affinity of for Pu(IV) rather than Pu(III) causes a decrease in the formal potential of the Pu(IV)/Pu(III) redox couple, directly affecting the degree of completion of the electrochemical reactions performed during CPC. A correction factor, f, is applied to account for the degree of completion of the analysis’ electrochemical steps and compensate for the effects of complexation. Thereby, a level of accuracy comparable to that achieved during the analysis of pure Pu solutions, is attained.Ultimately, a series of recommendations are put forward such that it becomes possible to maintain CPC’s good analytical performance for the measurement of Pu content in mixed Pu + U solutions.

Stability of plutonium oxide nanoparticles in the presence of montmorillonite and implications for colloid facilitated transport

The physical and chemical stability of PuO2 nanoparticles (intrinsic colloids) in groundwater will control their transport and may affect the performance of high-level radioactive waste repositories. We examined the chemical stability of two types of PuO2 nanoparticles at both 25 and 80 °C. The “alkaline” PuO2 nanoparticles were prepared by neutralizing an acidic Pu(IV) solution with dilute NaOH to pH ~9.5. The “acidic” PuO2 nanoparticles were precipitated from 0.1 M nitric acid by heating a Pu(IV) solution at 60–80 °C for 30 min. The chemical stability of these PuO2 nanoparticles was tested in the presence of montmorillonite, a common mineral in the environment and potentially relevant backfill material in some nuclear waste repository designs. The “alkaline” PuO2 nanoparticles were found to be unstable over a timescale of months at both 25 and 80 °C, with elevated temperature enhancing their dissolution rates and sorption to montmorillonite. PuO2 nanoparticle dissolution rates decreased with increasing Pu concentration, consistent with solution saturation. The “acidic” PuO2 nanoparticles appeared to remain stable for much longer than the “alkaline” PuO2 nanoparticles. The “alkaline” PuO2 nanoparticle dissolution rate constants were as high as 10−11.9±0.4 mol m−2 s−1 and 10−11.2±0.2 mol m−2 s−1 at 25 and 80 °C, respectively, while the “acidic” PuO2 nanoparticle dissolution rate at 80 °C was 10−13.5 mol m−2 s−1. Based on transmission electron microscopy, the “alkaline” and “acidic” PuO2 nanoparticles were of similar size (2.5–4.5 and 2–3 nm nanoparticles, respectively). However, the “acidic” PuO2 nanoparticles formed more ordered nanoparticle aggregates. Our results suggest that the specific conditions experienced during PuO2 nanoparticle formation could significantly affect the stability of PuO2 in the presence of competing sorption processes and, in turn, the relative importance of intrinsic versus pseudocolloid transport in the environment.

A simple microanalytical method for trace elemental determination in plutonium samples using energy dispersive X-ray fluorescence

A simple microanalytical method for trace elemental determinations in plutonium (Pu) solution samples was developed using Energy Dispersive X- Ray Fluorescence (EDXRF) spectrometry. A very small sample volume (200 μL) of Pu solution was taken for analysis and the major matrix Pu was separated using the extractant, Tri n-Butyl Phosphate (TBP), in 4 M HNO3 medium. Aliquot of 5 μL of the aqueous phase containing only the trace elements were deposited on a thin transparent mylar film inside the PVC (Poly Vinyl Chloride) EDXRF sample container and dried in ambient atmosphere inside a radioactive fume hood. After drying, the container was sealed with PVC lids. Two pure Pu solutions spiked with different trace elements having concentration of 6.25 and 23.25 μg/mL, were analyzed with RSD (Relative Standard Deviation) of 6.6 and 4.2% (1 σ, n = 3), and the average deviation from the expected values calculated on the basis of sample preparation were 8.9 and 6.6%, respectively. The developed methodology requires small amount of sample, extractant, and therefore generates less radioanalytical waste. Moreover, due to the requirement of small amount of sample, sealed inside a PVC container, the measurements could be carried out in ambient atmosphere without putting the instrument inside glove box. Further, the simple instrumentation of EDXRF, made this methodology very much ideal for the routine analysis of plutonium based samples.

Functionalized Polymer Thin Films for Plutonium Capture and Isotopic Screening from Aqueous Sources.

The rapid screening of plutonium from aqueous sources remains a critical challenge for nuclear nonproliferation efforts. The determination of trace-level Pu isotopes in water requires offsite sample preparation and analysis; therefore, new methods that combine plutonium purification, concentration, and isotopic screening in a fieldable detection system will provide an invaluable tool for nuclear safeguards. This contribution describes the development and characterization of thin polymer-ligand films for the isolation and concentration of waterborne Pu for direct spectroscopic analyses. Submicron thin films were prepared through spin coating onto Si wafers and consisted of combinations of polystyrene (PS) with dibenzoylmethane, thenoyltrifluoroacetone, and di(2-ethylhexyl)phosphoric acid (HDEHP). Pu uptake studies from solutions at pH from 2.3 to 6.3 indicated that only films containing HDEHP exhibited significant recovery of Pu. High alpha spectroscopy peak energy resolutions were achieved for PS-HDEHP films over a range of film thicknesses from 30 to 250 nm. A separate study was performed to evaluate uptake from a primarily Pu(V) solution where it was observed that doubling the HDEHP loading in the film increased uptake of Pu by an order of magnitude. X-ray photoelectron spectroscopy (XPS) analysis revealed that HDEHP was highly concentrated within the first few nanometers of the film at the higher loading. XPS analysis also revealed that, in the presence of water, HDEHP was stripped from the surface layer of the film at circumneutral pH. While significant losses of ligand were seen in all samples, higher loadings of HDEHP resulted in measurable amounts of ligand retained after a 12-h soak in water. Findings of this study are being used to guide the development of thin-film composite membrane-based detection methods for the rapid, fieldable analysis of Pu in water.

Polyurethane fibrous membranes tailored by rotary jet spinning for tissue engineering applications

ABSTRACTPolymeric membranes have gained popularity as fibrous structures for tissue regeneration. This research focuses on the rotary jet spinning (RJS) process combined with a polymer as a strategy for designing membranes. To this end, RJS‐polyurethane (RJS‐PU) membranes with different microstructures were produced. Considering the effects of solution properties on fiber production, the viscosity of PU solutions was evaluated. Membrane morphology was studied based on scanning electron microscopy and 2D fast Fourier transform analysis. The chemical and thermal properties were characterized by Fourier‐transform infrared spectroscopy and thermogravimetric analysis, respectively. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide and Live/Dead cell assays were performed to determine the material cytotoxicity by assessment of the profile of proliferation and cell viability. The results indicated that the combination of PU and RJS was an effective one for the production of fibrous structures for tissue engineering applications, demonstrating good compatibility with the cultured osteoblastic cell line. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2020,137, 48455.

One-Step Synthesis of Silver Nanoparticles Embedded Polyurethane Nano-Fiber/Net Structured Membrane as an Effective Antibacterial Medium.

A new and straightforward route was proposed to incorporate silver nanoparticles (Ag NPs) into the surface of polyurethane nanofibers (PU NFs). Uniform distribution of in situ formed Ag NPs on the surface of PU NFs was achieved by adding AgNO3 and tannic acid in a PU solution prior to the electrospinning process. The synthesized nanofiber mats were characterized with state-of-the-art techniques and antibacterial performances were tested against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria. The cytocompatibility and cell behavior were studied by using fibroblast cells. Following this preparation route, Ag/PU NFs can be obtained with excellent antibacterial performance, thus making them appropriate for various applications such as water filtration, wound dressings, etc.

Design of the GAGG scintillator for High Active Liquid Waste

In a reprocessing facility, it is required to develop a detector which can monitor plutonium (Pu) amount in the Pu solution containing the Fission Product (FP) in order to strengthen the safeguards capability. In order to investigate gamma rays which is applicable for Pu monitoring for High Active Liquid Waste (HALW), Ce:GAGG (Ce:Gd3Al2Ga3O12) scintillator which can measure a wide range of energy at high radiation dose rate and has relatively high resolution was newly designed and developed in deal with aim for monitoring of Pu quantity. Gamma ray measurement was conducted to HALW in the concrete cell by the designed detector, and it was confirmed that Eu-154 was detected using GAGG scintillator in HALW. In this paper, detector design, results of gamma ray spectra measurement, applicability evaluation to Pu monitoring and the future plan are presented.

Preparation of an electrospun tubular PU/GE nanofiber membrane for high flux oil/water separation.

A simple, tubular structure polyurethane/graphene (PU/GE) nanofiber membrane for continuous oil/water separation was prepared using the following strategies: a polyester (PET) fiber braided tube was used for reinforcement, stearic acid (SA) was used to assist GE dispersion, and a PU solution containing GE was used to cover the outer layer of the PET fiber braided tube using the electrospinning method. Specifically, the PU/GE nanofiber membrane has a multi-branched structure. The tubular braid reinforced (TBR) PU/GE nanofiber membrane was characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), confocal scanning microscopy (CSM) and capillary flow porometry. The contact angle results showed that the TBR PU/GE nanofiber membrane had good hydrophobic and lipophilic properties. The obtained membranes had good oil/water selectivity for oil–water separation (with a separation efficiency up to 99%). In addition, the optimized membrane can be effectively employed to separate a surfactant-stabilized water-in-oil emulsion with a separation efficiency up to 90% and a high permeate flux (137.5 L m−2 h−1). Our TBR PU/GE nanofiber membrane is therefore a desirable material for the highly efficient separation of water-in-oil emulsions, and shows broad application prospects in the field of oil/water separation.

Using the 90–105 keV gamma-rays for isotopic composition determination of plutonium in dilute solutions

Using the 90–105 keV gamma-rays for determining Pu isotopic composition is studied for dilute Pu solutions (0.0001–0.05 μg/mm3) as well as Pu-U mixed solutions. It is shown that for concentrations higher than 0.001 μg/mm3 Pu, results match well with those of mass spectrometric results. However, in mixed solutions, beyond 0.005 mg/mm3 U concentration, the errors on isotopic compositions of Pu increased as U content increased.

Optimization of U and Pu traces separation by chromatography for analytical purposes: influence of U/Pu mass ratio

A study related to the separations of uranium traces in a concentrated Pu solution and plutonium traces in a concentrated U solution was performed (with Pu/U or U/Pu = 102–105). Its objective was to determine the U–Pu separation performances for a low U and Pu concentration range, namely: Pu solutions of 2.5 mg L−1 to 2.5 g L−1 containing traces of U (25 µg L−1), U solutions of 10 µg L−1 to 10 mg L−1 containing traces of Pu (100 ng L−1). The developed methods proved to be efficient and its robustness was confirmed with the treatment of high-activity real samples.

Preparation of Polyurethane/Graphite Composite Films with Stable Mechanical Property and Wear Resistance Underwater.

The wear resistance and stable mechanical properties affect the service life of the underwater functional materials to a certain extent. Unfortunately, the current study of underwater functional materials is rarely related to these aspects. Herein, we successfully designed and prepared polyurethane/graphite nanosheet (PU/GN) composite materials, which exhibited excellent wear resistance and stable mechanical properties underwater. The PU/GN composite films were prepared by evaporating a mixed solution of PU and GN on concave hexagonal honeycomb silicon templates. The mechanical properties of the composite films were determined by tensile test, and the wear resistance was evaluated by comparing the surface morphology before and after grind. By adjusting the content of graphite in the composite films, we found that the composite films containing 23 wt% GN had higher tensile strength and superior wear resistance. Moreover, this composite film showed an outstanding stability when expose to water. The impressive results along with simple preparation process made PU/GN composite films had potential applications in robust underwater functional materials.

(Ce-Al)-oxide pillared bentonite: A high affinity sorbent for plutonium

The ability of bentonite and montmorillonite pillared by Al-oxide and mixed (Ln-Al)-oxides (Ln = La, Ce) to remove 239plutonium solution species from water is comparatively investigated at pH 7 and pH 4. Small-angle scattering and neutron contrast variation with H2O/D2O mixtures is used to verify the ingress of water in the calcined products after hydrophilicity was introduced by an NH3-H2O vapor treatment. The size and shape of the (La/Ce)-Al oxo-hydroxy pillaring cations (2 nm spheres) is determined by small-angle x-ray scattering from the pillaring solutions. Not all of the oxide pillars improved Pu uptake compared with sodium montmorillonite. At neutral and acidic pH only (Ce-Al)-oxide pillared clays showed the ability to remove Pu over the concentration range studied (1.35 × 10−8–8 × 10−8 mol dm−3) with distribution coefficient (KD) values >104. XPS analysis of the (Ce-Al)-oxide pillared clays indicates the presence of Ce4+ as cerium dioxide. The progressive improvement in sorption performance in the order of pillar type Al2O3 < La2O3-Al2O3 << CeO2-Al2O3 reflects the increasing access of Pu solution species to the clay mineral layers by changes to the basal spacing and specific surface area, and also to the higher stability of the (Ce-Al)-oxide pillars.

Redox-mediated formation of plutonium oxide nanoparticles.

Precipitates formed by the neutralisation of Pu(iii), Pu(iv), Pu(v), and Pu(vi) solutions were characterised by HRTEM, SAXS, and XRD in the suspensions. PuO2 nanoparticles uniform in size (typical diameter around 2.5 nm) and phase composition were observed in all cases under equilibrium conditions. For Pu(vi), the precipitation reactions proceed via an intermediate product.