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The freeze-drying or supercritical CO2 drying methods are usually used to remove the solvent to keep the shape of material in traditional methods for preparing graphene foam. Porous frozen tofu is a kind of traditional Chinese food and prepared through a process of freezing casting and thawing. Inspired by it, a green and economic approach for graphene foam (GF) synthesis using one-step reduction and air-drying is reported in this article. By controlling the reduction time and precursor concentration, monolithic GF with a little or without volume shrinkage can be obtained after a simple pre-freezing, thawing, and air-drying step of the graphene hydrogel. The obtained GF shows low density (17.5 mg/cm3), superelastic, high recyclability, and excellent oil absorption ability. During the whole preparation process, the conditions were mild, and no special equipment such as freezer dryer was used, which is beneficial to large-scale production of porous GF with high oil adsorption and recyclability.

In spent fuel reprocessing, the phase entrainment in the solvent extraction process would result in solvent loss, low efficiency and other adverse effects. As a superhydrophobic material with low density and large specific surface area, graphene aerogel may have potential applications in spent fuel reprocessing for the removal of entrained organic phase from raffinate. In this paper, the phase entrainment in the solvent extraction process was investigated by using centrifugal extractor as the extraction equipment. It was found the operation conditions, such as rotor speed, flow rates and phase ratio, have a significant effect on the phase entrainment. Afterwards, a kind of graphene-based superhydrophobic composite was synthesized and used to treat the entrained organic phase in raffinate by a simple adsorption process. The results showed that the proposed method can quickly reduce the content of the organic phase in raffinate to less than 0.1%, showing potential applications in spent fuel reprocessing.

Owing to the unique layer structures and efficient water transport, graphene oxide membranes (GOMs) have shown great promise in molecular and ion separation. In the above application fields, the stability of GOMs in aqueous solutions is the most essential requirement. In this paper, vortex shaking experiments and XRD characterization were carried out to test and illustrate the stability of GOMs in different solutions. Normally, when dry GOMs were immersed in aqueous solutions, the water molecules could rapidly enter layer space and enlarge the interlayer spacings (d-spacings), thus reducing the stability of GOMs in aqueous solutions. However, it was also found that the ions in aqueous solutions could play a positive role in restraining the d-spacings and stabilizing the GOMs. For monovalent cations (for example, H+ and Na+), high concentrations were required to guarantee the good stability of GOMs, which could be explained by the theory of electrostatic double layer. In contrast, low concentrations of divalent or trivalent cations (for example, Sr2+, UO22+ and Eu3+) could also efficiently crosslink the graphene oxide sheets, thus enhancing the stability of GOMs. Based on these results, to ensure the stability in practical application, a method of modifying original GOMs by 1 mM Eu3+ was proposed and verified by sucrose and metal ions permeation experiments. The results indicated that the modified GOMs could keep stable and be qualified to achieve selective separation.

“Red oil” explosion is an important safety issue in spent fuel reprocessing and the most fundamental measure to prevent “red oil” explosion is the capture of organic solvents in water phase requiring further treatment. In this paper, superhydrophobic graphene/polyvinylidene fluoride composite aerogel (GA–PVDF) was synthesized by using HI as reductant under mild condition. The characterizations of SEM, FTIR, XRD, contact angle, mechanical property and oil/water absorption ability were performed to optimize the preparation conditions of GA–PVDF. It is found under optimal condition, the composite shows excellent water resistance, oil–water separation and mechanical properties. Furthermore, the recyclability and possible operation model of obtained GA–PVDF were also investigated. The result demonstrates that the composite material can be simply and efficiently used to capture the organic solvents without water uptake, which is attractive in the application of spent fuel reprocessing. Moreover, the recyclability of material also ensures the reduction of secondary waste. All of these indicate that GA–PVDF has great application potential for oil–water separation and “red oil” explosion prevention in spent fuel reprocessing.

The decontamination of some extractable fission products, such as Zr and Ru, is an important issue in the Thorex process. Acetohydroxamic acid (AHA) is an organic ligand composed of only C, H, N and O atoms. It can be used as complexing and reducing agent to inhibit the extraction of Zr and Ru. In this paper, the effect of AHA and preheating on the extraction of Th, U, Zr and Ru was studied. It is found the extraction of Zr and Ru would be inhibited in the presence of AHA and preheating, meanwhile there was no obvious effect on the extraction of Th and U. Afterwards, the countercurrent extraction using centrifugal extractors was performed to further test and verify the effect of AHA in a typical Thorex process. The results indicate that the decontamination of Zr and Ru could be enhanced evidently due to the effect of AHA, and the corresponding decontamination factor would be improved from 27.0 to 3.3 × 103 and 111.0 to 1.5 × 103, respectively. Thus, the use of AHA would be an efficient means for enhancing the decontamination of Zr and Ru in Thorex process.

Graphene aerogel (GA) is a kind of superhydrophobic material with low density, high specific surface area and porosity. It can be used as modular matrix material to be impregnated with extractant due to its excellent organic solvent immobilization performance. In this paper, the modular GA based solvent impregnated adsorbents (GA-SIA) with various extractants were prepared. The adsorption performance of these adsorbents for typical fission products in high level liquid waste (HLLW) was investigated, and it is found that the adsorption performance is strongly dependent on the impregnated extractants. Based on the batch adsorption experiments, a modular process for the treatment of HLLW was proposed and tested. The results demonstrate that the modular process based GA-SIA possesses advantages of high selectivity, simple operation and low cost.

As a kind of three-dimensional graphene architecture material with superhydrophobic, low density, high specific surface area and porosity, graphene aerogel (GA) can be used to immobilize extractant to constitute the solvent impregnated adsorbent. In this paper, the N,N,N′,N′-tetraoctyldiglycolamide impregnated graphene aerogel ( GA-TODGA) was prepared to remove the thorium from aqueous solution. It is found that the adsorption of thorium on GA-TODGA is strongly dependent on the concentration of TODGA in GA and HNO3 in aqueous solution. Compared with other solvent impregnated adsorbents, the adsorption capacity of GA-TODGA is much higher due to the high immobilization capacity of GA for TODGA. Furthermore, the GA-TODGA also possesses excellent stability and reusability, ensuring the application potential of using GA-TODGA in large scale.

For the determination of μg-mg L-1 of FPs in 100 g L-1 of thorium matrix with HCl medium, a method, including anion-exchange pre-separation, evaporation and inductively coupled plasma mass spectrometry (ICP-MS) measurement, was developed. The procedure parameters, such as the matrix effect of thorium, the acidity of separation, the elution curve of thorium and FPs and the temperature of evaporation were optimized by batch equilibration, column elution and evaporation experiments. It was found that the average recovery of the FPs was in the range 80 - 110%, and the RSD values were in the range 2 - 15% utilizing prior anion exchange separation of FPs from thorium samples. Furthermore, the detection limit of the method was also investigated.

In consideration of the lack of systematic investigations on solvent extraction process and equipments for extracting 233U from irradiated thorium, an extraction process using TBP (Tri-n-butyl phosphate) as extractant was proposed, optimized and verified. First, the process parameters, including concentration of TBP and HNO3, phase ratio, are preliminary selected. Then, a multistage countercurrent extraction using batch simulation is used to further optimize the parameters. Finally, the extraction process is verified through the continuous multistage countercurrent extraction using both mixer settler and centrifugal extractor, and the process operation efficiency is estimated by equilibration time and concentration profiles of Th and U after equilibrium.

The drawbacks of current high-level liquid waste (HLLW) separation processes would bring some adverse effects on the sustainable and clean utilization of nuclear power. In this work, a novel separation method for HLLW treatment based on graphene oxide membranes (GOMs) was investigated. Effects of nitric acid concentration and membrane thickness on the permeation behaviors of typical ions through GOMs were systematically investigated. On the whole, the permeation rates were in the order: hydrogen ion, cesium ion > sodium ion > strontium ion > europium ion, uranyl ion > thorium ion, which could be well explained by size exclusion and chemical interaction. As the nitric acid concentration decreased, strong coordination cations were generally restrained from migrating through GOMs due to cations hydrolysis and deprotonation of graphene oxide sheets. Ions permeation was supposed to be a two-step process which included entrance to the membrane and intramembrane migration. Based on the favorable rejection of f-block elements, GOMs separation showed promising potential in HLLW treatment. Furthermore, a new technical route for HLLW separation was proposed which showed superiority of simplified process, low running cost, less secondary radioactive waste production.

A new approach for uranium extraction employing graphene aerogel (GA) as a skeleton loading organic solution (GA-LOS) is proposed and investigated. Firstly, the GA with super-hydrophobicity and high organic solution absorption capacity was fabricated by one-step reduction and self-assembly of graphene oxide with ethylenediamine. By adsorbing Tri-n-butyl phosphate (TBP)/n-dodecane solution to prepare GA-LOS, the extraction of U(VI) from nitric acid medium using GA-LOS was investigated and compared with conventional solvent extraction. It is found that the GA-LOS method can provide several advantages over conventional solvent extraction and adsorption due to the elimination of aqueous-organic mixing-separation procedures and easy solid-liquid separation. Furthermore, it also possesses higher extraction capacity (the saturated extraction capacity of GA loading TBP for U(VI) was 316.3mgg-1 ) and lower consumption of organic diluents, leading to less organic waste. Moreover, the stability of GA-LOS in aqueous solution and cycling test were also studied, and it shows a remarkable regeneration capability, making it an ideal candidate for metal extraction from aqueous solution.

In this study, RMS roughness values of the interface between top silicon and buried layer in SIMOX–SOI (SIMOX, separation by implantation of oxygen; SOI, silicon-on-insulator) were directly measured by AFM. The results revealed that they were self-affine fractal. Based on the variation of the RMS values with scan sizes, the fractal dimensions and horizontal cutoffs of the fractal interfaces were calculated. It was found that the cutoff values varied with the different processes suggesting that the cutoff is sensitive to process and can be used to characterize the quality of SIMOX–SOI wafer.

ZnO:Al (ZAO) films were deposited on fused silica substrates heated to 350 °C by dc magnetron reactive sputtering from a Zn target mixed with 1.5 wt% Al. Films deposited on a substrate heated to a temperature between room temperature and 300 °C were (001)-oriented crystals, but those grown at 350 °C consisted of crystallites with (001) and (101) orientations. The dependence of electrical properties such as resistivity, carrier concentration, and Hall mobility on temperature was measured. The results indicate that the carrier concentration and Hall mobility increase with increasing temperature up to 250 °C, though the Al content remains unchanged in this temperature range. The probable mechanisms are discussed. The minimum resistivity of ZAO films is 4.23 × 10−4 Ω cm, with a carrier concentration of 9.21 × 1020 cm−3 and a Hall mobility of 16.0 cm2 v−1 s−1. The films show a visible transmittance of above 80%.

High preferred (002) orientation Al-doped ZnO (ZAO) films have been prepared by de magnetron reactive sputtering of an alloy target (98.5 wt.% Zn-1.5 wt.% Al) onto polyester substrates. The structural, mechanical, electrical and optical properties were investigated. The ZAO film has a sheet resistance of as low as 47.5 Omega/square and an average visible transmittance of about 70%. An average IR reflectance of about 70% in the region of 2.5-25 mum also has been obtained. (C) 2001 Elsevier Science B.V. All rights reserved.

Highly preferred (002) orientation transparent conductive Al-doped ZnO (ZAO) films were successfully prepared by de magnetron reactive sputtering from a Zn target mixed with Al of 2.0 wt.%. The film has a resistivity of 4.80 X 10(-4) n cm and a visible transmittance of as high as 90%. XPS analysis indicates Al-enrichment on the film surface. The asymmetry of Al 2p(3/2) XPS peak is resolved into two components: one centering at 72.14 eV attributed to metallic Al and the other having a binding energy of 74.17 eV due to oxidized Al. (C) 2001 Elsevier Science B.V. All rights reserved.

High preferred (0 0 2) orientation Al-doped ZnO (ZAO) films were prepared by DC magnetron reactive sputtering from a Zn target mixed with Al of 2.0 wt%. The dependence of spatial distributions of resistivity on substrate temperature indicates that the spatial distribution of resistivity across substrate placed parallel to the target was improved by increasing substrate temperature. XPS analysis indicates Al-enrichment on the film surface.

Contributions of acoustical deformation scattering, ion impurity scattering and grain boundary potential scattering to the conductivity of TCO films have been calculated in order to deduce the intrinsic limit of conductivity of TCO films regardless of precise details of the preparation procedure. The results indicate that the effective mass of charge carriers has a strong dependence on carrier concentration. Based on the effective mass correction, as well as the carrier concentration ionized impurity centre correction, scattering due to ion impurity has been developed to explain the upper limit of mobility or the lower limit of resistivity of TCO films. Two empirical expressions are introduced to depict the dependence of the upper limit of mobility and the lower limit of resistivity of TCO films on carrier concentration. The dependence of transparency on carrier concentration is also discussed.

The chemical state of oxygen, aluminum and zinc in Al-doped ZnO (ZAO) films was investigated by X-ray photoelectron spectroscopy (XPS), as well as the transition zone of the film-to-substrate, by auger electron spectroscopy (AES). The results show that zinc remains mostly in the formal valence states of Zn2+. A distinct asymmetry in Al 2p(3/2) photoelectron peaks has been resolved into two components, one is metallic Al and the other is oxidized Al. The depth profile of the two components revealed that metallic Al mainly exists in the thin surface layer. The close inspection of Ols shows that Ols is composed of three components, centered at 530.15 +/- 0.15, 531.25 +/- 0.20 and 532.40 +/- 0.15 eV, respectively. AES reveals an abrupt transition zone between the ZAO and quartz substrate. (C) 2000 Elsevier Science B.V. All rights reserved.

An ultra low power dissipation incremental sigma-delta (ΣΔ) ADC is presented in this paper. The operational amplifier is replaced by a simple inverter, which reduces the power dissipation and save areas considerably. A second-order cascaded integrator, which is composed of a ripple counter and an accumulator is used as digital filter. Simulated results indicate that the ΣΔ can achieve 12ibt resolution with only 92.8uW power dissipation in 1.8 V and 1.2 V analog and digital power supply respectively.