•A synergistic effect was found in co-gasification of soda lignin and PE.•The order of gasification efficiency of various plastics: PE > PC ≈ PP > ABS.•Much alkane gases were generated from ...degradation of plastics, especially PE and PP.•The presence of soda lignin promoted the reforming of alkanes and H2 production.
In this study, the co-gasification of soda lignin produced from black liquor and various plastics in supercritical water was investigated experimentally. The effect of the mixing ratio of soda lignin/PE, temperature, reaction time, total concentration and plastic types was studied. A synergetic effect was found in co-gasification of PE and soda lignin, and the maximum influence was obtained at a mixing ratio of 50:50. Increasing the temperature and reaction time, and reducing the concentration improved the gasification efficiency and hydrogen production from co-gasification of PE/soda lignin (50:50). The H2 yield increased over 5 times to 57.0 mol/kg with temperature increasing from 500 °C to 750 °C, and the highest H2 yield of 63.3 mol/kg was obtained at 700 °C when the concentration was reduced to 5 wt%. The gasification efficiencies of different plastics were distinct and the order is: PE > PC ≈ PP > ABS, and the addition of soda lignin improved all the gasification efficiencies. The alkali salts in soda lignin also catalyzed the reforming of CH4 and C2H6 that generated from the depolymerization of plastics, especially PE and PP and improved the hydrogen production.
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•LIBS satisfactorily measured the accumulation of Sr and Cs on the surface of 316L stainless steel.•The concentration of Sr and Cs on the surface reached the maximum values at ...21 days.•Strontium had two forms on the steel surface: SrCrO4 in the oxide layer and SrCO3 in the matrix.•The contamination of Cs was more inclined to the surface than Sr.•The contamination mechanism of Sr and Cs on the surface of 316L stainless steel was analyzed.
The contamination of fission products (90Sr and 137Cs) on the metallic material (316L stainless steel) of alkaline spent fuel storage pond threatens to decommission nuclear facilities. Compared with previous studies unable to detect Cs on the surface of contaminated steel by laser-induced breakdown spectroscopy (LIBS), this study selected the emission lines of Sr II 407.74 nm and Cs I 455.77 nm as the analytical spectral lines of LIBS, and for the first time satisfactorily measured and analyzed the accumulation of Sr and Cs on the surface of 316L stainless steel for 7, 14, 21, 30 and 60 days, respectively. It was found during the accumulation, the concentration of Sr and Cs on the surface reached their maximum after 21 days, and relatively stabilized 30 days later. In addition, combined with the physicochemical characterizations, the contamination mechanism of Sr and Cs on 316L stainless steel was proposed, with the contaminants gradually diffusing from the oxide layer dissolved and damaged in the alkaline corrosive environment to the matrix. Strontium had two forms on the steel surface: SrCrO4 in the oxide layer and SrCO3 in the matrix, but the contamination of Cs was more inclined to the surface than Sr.
Single-phase tungsten diboride (WB2) was synthesized at high pressure and high temperature. The different grain sizes ranging from 300 nm to 3 µm were successfully obtained in WB2 by controlling the ...experimental conditions. The effects of grain size on hardness and resistivity properties were investigated. The Vickers hardness of WB2 was modulated with grain size. The maximum asymptotic Vickers hardness is 25.5 GPa for WB2 with a grain size of 300 nm which is a 10% increase compared to WB2 with a grain size of 3 µm. The optimal electrical resistivity of WB2 was 10−7 Ωm with the biggest grain size of 3 µm, which is ascribed to low grain boundary density. The superior properties of hardness and electrical resistivity demonstrate that WB2 should be a new functional hard material replacing WC which is widely used in industrial production.
Kaolin was utilized as a raw material for geopolymers with various Si/Al ratios, and a hydrothermal-microwave treatment was proposed to obtain Cs-containing ceramics to immobilize
137
Cs. The results ...show that with Si/Al from 1/1 to 3/1, the hydrothermal treatment will tend to produce CsAlSiO
4
, pollucite (CsAlSi
2
O
6
) and pollucite solid solutions, respectively. Following the hydrothermal reaction, a rapid microwave process (30 min) enhances the loose microstructure of hydrothermal products, and higher microwave temperatures promote pollucite crystallization. Cs-containing ceramics with high Cs content (31%) and low leaching rate (9.7 × 10
−4
g m
−2
d
−1
) are obtained at 800 °C with Si/Al ratio of 2/1.
The water corrosion of tungsten as a target material can affect the safe operation of accelerator-driven neutron source. This paper reported the corrosion behaviors of tungsten in ultrapure water and ...tap water for 7, 14, 21, 30 and 60 days. Moreover, ICP-MS, XRD, XPS, SEM-EDS and LSCM were used to analyze the components in solutions, crystalline structures, chemical compositions and surface morphologies. It was found that the dissolution of tungsten, due to corrosion, reached its maximum between 30 days and 60 days in both solutions. The cube-shape substance, CaWO
, was the main corrosion product after tungsten in tap water. The tungsten oxide was changed from WO
to WO
during the corrosion of tungsten in ultrapure water. Compared with tungsten in ultrapure water, tungsten in tap water had its surface completely destroyed, with a dense diamond shape. Therefore, based on the analysis from this study, the corrosion mechanisms of tungsten in ultrapure and tap water were revealed.
Strontium zirconium phosphate (SrZr
4
(PO
4
)
6
) ceramics has high density and chemical inertness, which can safely and effectively immobilize the divalent fission product Sr in the ceramic matrix. ...In this study, a novel SrZr
4
(PO
4
)
6
ceramic was synthesized using microwave sintering of uranium tailings. This method features shorter sintering times and efficient energy use. Sr replaces Na in sodium zirconium phosphate (NaZr
2
(PO
4
)
3
) due to similar ionic radii, transforming it into SrZr
4
(PO
4
)
6
ceramics. The results showed that the sintered samples prepared by holding at 1200 °C for 50 min, which the density of the solidified body reached up to 3.2 g/cm
3
.The ceramics showcase outstanding leach resistance, with Sr leaching rates far below the nuclear industry standard (1 × 10
−2
g m
−2
d
−1
). Similarly, the leaching rates for Na, Zr, P, and Si (10
–4
–10
–6
, 10
–6
–10
–8
, 10
–3
–10
–4
, and 10
–2
–10
−3
g m
−2
d
−1
) are significantly lower than industry standards.
Lithium (Li) is one of the commonly used target materials for compact accelerator-based neutron source (CANS) to generate neutrons by
Li(p, n)7 Be reaction. To avoid neutron yield decline caused by ...lithium target reacting with the air, a titanium (Ti) coating was deposited on the lithium target by magnetron sputtering technology. The color change processes of coated and bare lithium samples in the air were observed and compared to infer the chemical state of lithium qualitatively. The surface topography, thickness, and element distribution of the coating were characterized by SEM, EDS and XPS. The compositions of samples were inferred by their XRD patterns. It was found that a Ti coating with a thickness of about 200 nanometers could effectively isolate lithium from air and stabilize its chemical state in the atmosphere for at least nine hours. The Monte Carlo simulations were performed to estimate the effects of the Ti coating on the incident protons and the neutron yield. It turned out that these effects could be ignored. This research indicates that depositing a thin, titanium coating on the lithium target is feasible and effective to keep it from compounds' formation when it is exposed to the air in a short period. Such a target can be installed and replaced on an accelerator beam line in the air directly.
Short silicon nitride fibers were fabricated by direct nitridation of ferrosilicon in N₂ atmosphere, and their structure and possible growth mechanism were characterized and investigated. The ...rod-like fibers which were α-Si₃N₄ with a low degree of crystallization and a high aspect ratio had a diameter of about 4 μm and a length close to a few millimeters. Belt-like fibers with a width about 5 μm and a thickness about 1 μm were also found in the nitrides. Scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM), and selected area electron diffraction (SAED) investigations indicated that the fibers were single-crystalline α-Si₃N₄ with few amorphous distributed in the edge region, and the fibers grew by vapor⁻liquid⁻solid (VLS) mechanism.
Secondary electron emission (SEE) inhibition and vacuum instability are two important issues in accelerators that may induce multiple effects in accelerators, such as power loss and beam lifetime ...reduction. In order to mitigate SEE and maintain high vacuum simultaneously, open-cell copper metal foam (OCMF) substrates with Ti-Zr-V-Hf non-evaporable getter (NEG) coatings are first proposed, and the properties of surface morphology, surface chemistry and secondary electron yield (SEY) were analyzed for the first time. According to the experimental results tested at 25 °C, the maximum SEY (δmax) of OCMF before and after Ti-Zr-V-Hf NEG film deposition were 1.25 and 1.22, respectively. The XPS spectra indicated chemical state changes of the metal elements (Ti, Zr, V and Hf) of the Ti-Zr-V-Hf NEG films after heating, suggesting that the NEG films can be activated after heating and used as getter pumps.
In this work, coal fly ash, hereinafter CFA is proposed to work as raw material for immobilization of Sr-contaminated soil by microwave sintering in the path towards resource utilization of solid ...waste. The immobilization mechanism and performance was systemically investigated through phase evolution, microstructure, elemental distribution, and physical properties. The results shown that the Sr could be incorporated into feldspar strontian (SrAl2Si2O8) at 1300 °C for 30 min. Moreover, the maximum solid solubility of SrSO4 was more than 30 wt.%. The Sr was homogeneously distributed in the sintered matrices without substantial enrichment. The sintered matrix exhibited high density (2.53 g/cm3). Thus, microwave heating coupled with CFA could provide a new method for immobilization of Sr-contaminated soil in case of the spent nuclear reprocessing cycle in nuclear power plants or a nuclear accident emergency.
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