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ABSTRACT The matrix lightweight porous reticulated materials (matrix LPRMs) were fabricated with fly ash, alumina and andalusite by the polymer sponge replica technique. Further, the matrix LPRMs were immersed in [...]

In this study, a series of aluminum borate ceramics (ABCs) with needle-like whiskers were obtained using a low-cost, solid-state, pressureless sintering ceramic route, without any additives during the preparation process. The effects of different alumina/boric acid molar ratios and sintering temperatures on the phase composition, microstructure, mechanical properties, specific surface area, pore size distribution, and sub-cadmium neutron shielding properties of ABCs were studied using orthogonal experiments. It was observed that pure phase aluminum borate (Al18B4O33) ceramics could be obtained at 1100 ℃, forming a mass of needle-like whiskers. The whiskers’ aspect ratio, fracture work, specific surface area, and pore size distribution of ABCs are maximized when ABCs are sintered at 1100 ℃ with 9:6 alumina/boric acid molar ratio. In this condition, ABCs (0.5 cm) can shield 70% of sub-cadmium neutrons (E<0.4 eV). These findings demonstrate the great potential of aluminum borate ceramics for neutron shielding applications.

Time-encoded imagers (TEI) are important class of instruments to search for potential radioactive sources to prevent illicit transportation and trafficking of nuclear materials and other radioactive sources. The energy of the radiation cannot be known in advance due to the type and shielding of source is unknown in practice. However, the response function of the time-encoded imagers is related to the energy of neutrons or gamma-rays. An improved image reconstruction method based on MLEM was proposed to correct for the energy induced response difference. In this method, the count vector versus time was first smoothed. Then, the preset response function was adaptively corrected according to the measured counts. Finally, the smoothed count vector and corrected response were used in MLEM to reconstruct the source distribution. A one-dimensional dual-particle time-encode imager was developed and used to verify the improved method through imaging an Am–Be neutron source. The improvement of this method was demonstrated by the image reconstruction results. For gamma-ray and neutron images, the angular resolution improved by 17.2% and 7.0%; the contrast-to-noise ratio improved by 58.7% and 14.9%; the signal-to-noise ratio improved by 36.3% and 11.7%, respectively.

The grade analysis of lead-zinc ore is the basis for the optimal development and utilization of deposits. In this study, a method combining Prompt Gamma Neutron Activation Analysis (PGNAA) technology and machine learning is proposed for lead-zinc mine borehole logging, which can identify lead-zinc ores of different grades and gangue in the formation, providing real-time grade information qualitatively and semi-quantitatively. Firstly, Monte Carlo simulation is used to obtain a gamma-ray spectrum data set for training and testing machine learning classification algorithms. These spectra are broadened, normalized and separated into inelastic scattering and capture spectra, and then used to fit different classifier models. When the comprehensive grade boundary of high- and low-grade ores is set to 5%, the evaluation metrics calculated by the 5-fold cross-validation show that the SVM (Support Vector Machine), KNN (K-Nearest Neighbor), GNB (Gaussian Naive Bayes) and RF (Random Forest) models can effectively distinguish lead-zinc ore from gangue. At the same time, the GNB model has achieved the optimal accuracy of 91.45% when identifying high- and low-grade ores, and the F1score for both types of ores is greater than 0.9.

Multifunctional radiation shielding materials are important for the development of miniaturised nuclear reactors. Bi6B10+2xO24+3x(x=  − 2, − 1,0,1,2) compounds were economically and conveniently synthesised by using a solid-state sintering reaction of bismuth oxide and boric acid. The effects of liquid phase boron oxide migration due to sintering temperature and boric acid content on the microscopic morphology, crystalline phase composition and macroscopic properties of the samples were systematically investigated. And the studies highlight that when the content of boric acid particles increases, the nucleation and growth of bismuth borate is accelerated, which promotes the sintering of the ceramic and have a positive effect on improving the physical properties of materials. The ceramic with x= 1 exhibited the highest cold elastic modulus (28.41 GPa), cold flexural strength (18.55 MPa) and room temperature thermal conductivity (0.3420 W/(m·K)). Radiation shielding tests showed neutron and gamma shielding of 63.7% and 39% for the ceramic with x= 1 when the sample thickness was 1.5 cm. Thus, based on the information gathered from our research, Bi6B10+2xO24+3x(x=  − 2, − 1,0,1,2) ceramics were expected to be designed as an integrated nuclear reactor shielding/insulation material.

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for real-time online coal analysis. The lens-to-sample distance (LTSD) significantly affects the obtained signal intensity as well as the accuracy of the element quantitative analysis by LIBS. In this study, a new method is proposed to correct the effect of the change in LTSD on the signal intensity. A correction formula that fits the relationship between the obtained signal intensity and the deviation (d) between the LTSD and the focal length is constructed through a series of experiments based on 18 standard coal samples and validated with three types of unknown coal samples. The results show that compared with the original signal intensity in the experiments, the relative errors between the corrected signal intensity and the signal intensity when the LTSD is equal to the focal length decreased by a factor of more than ten for almost all the elements of C, H, O, and N in the three samples. In particular, when dtakes −4 to 2 mm, the mean relative errors after correction are all below 10%. This indicates that the proposed method can be used to correct the signal intensity of the elements C, H, O, and N when dis −4 to 2 mm in real-time online coal analysis.

A phase conversion technology, involving the loading of brine samples with anionic polyacrylamide (APAM) colloidal droplets, is proposed to detect metal elements rapidly and accurately in liquid samples using laser-induced breakdown spectroscopy. The experimental conditions were optimized by comparing the obtained emission intensities and the signal-to-noise ratios, including the concentration of APAM, volume ratio of APAM solution to sample, delay time, and lens-to-sample distance (LTSD). Three kinds of complex brine samples with slightly soluble salts were used to test the analytical performance of the proposed method. The results show that the discrepancies of the concentrations of Li, Sr and Ca were 0.74–3.59%, compared with those obtained using inductively coupled plasma-optical emission spectrometry. This suggests that the proposed method can successfully determine metal elements in liquid samples, featuring short sample preparation time (less than 20 min), small sample volume (10 μL), and simple operation (no adsorption).

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The traditional library least squares approach (LLS) is affected by the inconsistency of the statistical uncertainties of different channels in a gamma spectrum, which leads to large fluctuations in the analysis results. This work proposes a weighted library least squares approach (WLLS) that uses the square root of the count to weight the regression objective function and has implemented a verification experiment based on Prompt Gamma Neutron Activation Analysis (PGNAA). The results showed that, after weighing using the square root of the count, the fluctuation level of statistical uncertainty in the spectrum was reduced from 44.34 to 2.25. After the analysis of the WLLS approach, the average standard deviation of the results was reduced to at least 0.37 times that of the LLS approach.

Mullite reticulated porous ceramics (RPCs) were fabricated with fly ash, alumina, and andalusite by polymer sponge replica technique, followed by the process of vacuum infiltration with recoating slurry included. And the effect of different recoating slurry with different particle size fly ash on the properties of mullite RPCs was studied. The matrix slurry and recoating slurry were investigated and optimized. And then, the microstructure, composition of phases, and mechanical properties of mullite RPCs were examined by SEM (scanning electron micrograph), XRD (X-ray diffraction), and hydraulic universal testing machine. Moreover, the influence of particle size of fly ash on the thermal shock stability was analyzed by calculating residual stress model and grey relational model. The result indicated that the specimens that were recoated by the slurry with the smaller particle size of fly ash might have more excellent properties.

In terms of improving the alkali corrosion resistance of corundum castables, coating technology is applied to preparing the excellent properties of corundum castables with a glaze layer. The work focuses on the effect of the ratio of Al2O3/SiO2on the properties of Li2O-Al2O3-SiO2glazes. Furthermore, the influence of Li2O-Al2O3-SiO2glazes on the alkali corrosion resistance of corundum castables is investigated. The results show that at a high temperature with increasing of the ratio of SiO2/Al2O3in Li2O-Al2O3-SiO2glazes, the viscosity and amount of liquid phase in the glaze increase gradually, which has a great influence on the quality of the glaze at a high temperature. And as the ratio of Al2O3/SiO2in the glaze is between 6 and 8, the apparent porosity of corundum castables with the glaze layer decreases significantly resulting in preventing the permeation of alkali vapor into the castables, which can improve the alkali corrosion resistance and mechanical properties of corundum castables dramatically. Moreover, as the thermal expansion coefficient of the matrix is higher than the glaze layer, the compressive residual stress (tangential direction) will exist in the glaze layer, resulting in enhancing crack bifurcation, which is beneficial to improving the properties of corundum castables.

Stable and durable piezoelectric nanogenerators (PENGs) with good flexibility, high performance and superior radiation resistance under harsh environments are promising for space exploration. Here, a novel PENG based on P(VDF-TrFE)/boron nitride nanotubes (BNNTs) nanocomposite micropillar arrays with enhanced performance and excellent neutron radiation shielding is prepared by a reliable nanoimprint lithography. The PENG comprised of a microstructured P(VDF-TrFE)/0.3 wt% BNNTs nanocomposite demonstrates an outstanding output voltage of 22 V and a sensitivity of 55 V/MPa under the pressure of 0.4 MPa, which are 11-fold higher than those of pristine P(VDF-TrFE) film. This dramatic enhancement in performance is ascribed to synergistic contributions from strong piezoelectric BNNTs and a strain confinement effect of the nanocomposite microstructure. In practice, the PENG is capable of scavenging various mechanical and biomechanical energy for lighting up commercial LEDs, an LCD screen and a digital watch. More importantly, the as-obtained PENG exhibited 9% neutron radiation shielding with neutron cross section increase reaching 260% when compared to the film without BNNTs. Moreover, the high output is retained after 2 h of neutron radiation exposure. Overall, the as-prepared microstructured nanocomposites look promising for high-efficiency piezoelectric nanogenerators for the self-powered and wearable electronic devices, in particularly, under the extreme space environments.

Hybrid methylammonium lead tribromide (MAPbBr3) perovskite has attracted great attention in ionization radiation detection. However, the charge collection remains a challenge. Here, fast response and high-sensitivity X-ray detection based on MAPbBr3single crystals with a surface barrier Schottky diode has been achieved at room temperature. The Schottky surface barrier can overcome the large leakage current at a high electrical field, enabling us to reduce the noise and increase the charge collection efficiency. This surface barrier device has been demonstrated a 3 times improvement over the photoconductor based X-ray detector, which enables usage in nuclear medicine, especially for X-ray imaging technology.

Real-time analysis of metallic mineral grade and slurry concentration is significant for improving flotation efficiency and product quality. This study proposes an online detection method of ore slurry combining the Prompt Gamma Neutron Activation Analysis (PGNAA) technology and artificial neural network (ANN), which can provide mineral information rapidly and accurately. Firstly, a PGNAA analyzer based on a D-T neutron generator and a BGO detector was used to obtain a gamma-ray spectrum dataset of ore slurry samples, which was used to construct and optimize the ANN model for adaptive analysis. The evaluation metrics calculated by leave-one-out cross-validation indicated that, compared with the weighted library least squares (WLLS) approach, ANN obtained more precise and stable results, with mean absolute percentage errors of 4.66% and 2.80% for Fe grade and slurry concentration, respectively, and the highest average standard deviation of only 0.0119. Meanwhile, the analytical errors of the samples most affected by matrix effects was reduced to 0.61 times and 0.56 times of the WLLS method, respectively.

A prompt gamma neutron activation analysis (PGNAA) set-up was developed for the elements detection in aqueous solution, which includes a 241Am-Be neutron source and a 4-inch BGO detector. The geometry of set-up is determined by a series of simulations with the MOCA code to improve the efficiency of the elements detection. The thermal neutron flux and the gammaray self-absorption are considered during the optimization calculations. Experiments were performed to validate the set-up using samples including chlorine and mercury, respectively. The result shows that the characteristic peak count has linear relationship with the chlorine and mercury concentration changing. The minimum detectable concentrations of chlorine and mercury were found as 54 mg/L and 51.4 mg/L, respectively.

When X-ray fluorescence (XRF) technology is used to measure the sulfur concentration in coal online, the measurement accuracy is affected by the coal’s uneven surface and the particle size. In order to improve the accuracy of sulfur concentration measurement, an online measurement system, consisting of a portable X-ray fluorescence instrument and an auxiliary distance correction module, was developed in this paper. By measuring the standard coal samples of known sulfur concentration, we obtained a calibration curve that can be used to analyze the sulfur concentration. We studied the relationship between the X-ray fluorescence intensity (I) and the distance (D) from surfaces to instrument. The results showed that there was a good linear relationship between Iand Dwhen the sulfur content was certain. Based on these knowledge, the distance correction formula of X-ray fluorescence intensity was proposed. By applying the distance correction formula to experimental sulfur concentration measurement, we demonstrated that the measurement accuracy can be significantly increased.

In this research, for improving the measurement performance of Prompt Gamma-ray Neutron Activation Analysis (PGNAA) set-up, a new optimization method for set-up design was proposed and investigated. At first, the calculation method for Signal-to-Noise Ratio (SNR) was proposed. Since the SNR could be calculated and quantified accurately, the SNR was chosen as the evaluation parameter in the new optimization method. For discussing the feasibility of the SNR optimization method, two kinds of PGNAA set-ups were designed in the MCNP code, based on the SNR optimization method and the previous signal optimization method, respectively. Meanwhile, the single element spectra analysis method was proposed, and the analysis effect of single element spectra as well as element sensitivity were used for comparing the measurement performance. Since the simulation results showed the better measurement performance of set-up designed by SNR optimization method, the experimental set-ups were built for the further testing, finally demonstrating the feasibility of the SNR optimization method for PGNAA set-up design.

Multi-target X-ray tube is a new type X-ray source, and can be applied in many fields such as sensitive X-ray fluorescence analysis and medical imaging. In this work, we report an electric field modulation multi-target X-ray tube, which contains four targets (Cr, Ni, Au, Mo) coated on a Beryllium (Be) window. A four-valve electric field deflector was developed to deflect the electron beam to bombard the corresponding targets. Particle dynamics analysis software was employed to simulate the particle tracking of electron beam. The results show that the 30 keV electron beam could get a 6.7 mm displacement on the target plane by 105 V/m electric field. The focus areas are about 2 mm × 5 mm and 4 mm × 2.5 mm after deflection in two directions. Thermal behavior calculated by ANSYS shows that the designed target assembly could withstand a 10 W continuous power. The optimum target thicknesses and emission spectra were obtained by Geant4 when the thickness of Be window was 300 μm and the electron beam incident angle was 0.141 rad. The results indicate that this multi-target X-ray tube could provide different X-ray sources effectively.