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Due to the weak moderating capability of carbon dioxide itself, supercritical carbon dioxide cooled reactor typically has a hard energy spectrum and is susceptible to safety issues introduced by positive reactivity feedback in the event of LOCA (loss of coolant accident). In this paper, based on the energy spectrum characteristics of supercritical carbon dioxide reactor, a three-factor formula was proposed to describe the neutron circulation process. Based on the analysis of the threefactor formula, the effective fission neutron number and neutron utilization factor were refered as spectral terms in this study, while the probability of no leakage was referred as the leakage term. When studying the effect of moderator, fuel burnup, etc. on the void reactivity, the energy spectrum factor was mainly considered. When studying the effect of radial reflector material, high radial ratio, etc. on the void reactivity, the leakage factor was mainly considered, providing guidance for the core design of supercritical carbon dioxide reactors based on this theoretical basis. Using Monte Carlo simulation method, modeling, verification, and analysis were carried out for the supercritical carbon dioxide cooled reactor design proposed by MIT. The fuel assemblies of this reactor adopt a hexagonal annular fuel design, with the center of the assembly being the SCO2 coolant channel, which is separated from the MOX fuel by a cladding. A total of 265 fuel rod assemblies arranged in a hexagonal pattern make up a fuel component, and 562 fuel components (divided into three zones) and 21 control rod components arranged in a hexagonal pattern make up the reactor core active zone. Axial and radial reflector layers are set outside the active zone, and the outermost layer is a B4C absorber. The height of the active zone is 1.54 m, and the effective diameter is 4.81 m, with a height-to-diameter ratio of H/D=0.32 and a thermal power output of 2 400 MW. The results show that the design of supercritical carbon dioxide reactor needs to focus on the softening of energy spectrum and reasonable core geometry design. Using supercritical carbon dioxide as the radial reflector layer, in the event of LOCA, the carbon dioxide as the reflector and the carbon dioxide inside the core will leak simultaneously, and the increase in core leakage rate will lead to a decrease in void reactivity. Compared with other materials such as BeO, PbO, and SiO2, using a carbon dioxide reflector layer can better ensure the criticality of the core and improve neutron economy. However, due to the generally low neutron reflection ability of supercritical carbon dioxide itself, if the core has a large radial leakage due to a high core-to-diameter ratio, a thicker radial reflector layer is required, which may bring additional engineering difficulties and costs, requiring balance in the design. Setting moderators by partition can flatten the neutron flux, soften the energy spectrum, and reduce the reactivity introduced by LOCA.

To study the magnetic change mechanism of weakly caking coal during the heating process, the mass magnetic susceptibility of coal samples during the heating process was measured in this paper. Compared with the burnt coal sample after heat treatment at the same temperature, the magnetic change process of coal during heating was divided into four stages. The experiments of programmed temperature rise, industrial analysis and X-ray diffraction of coal were conducted at different stages to explore the key factors that lead to changes in its magnetic properties in different heating stages. The experimental results show that the magnetic susceptibility of the coal sample changes from negative to positive and then slowly rises at room temperature to 200 ℃. The effect on the magnetic properties of the coal at this stage is due to the decrease of the diamagnetic carbon-containing compounds in the coal due to oxidative consumption. At 200 ℃ to 350 ℃, the magnetic susceptibility of the coal sample rises sharply, and the average growth rate is 10 times higher than that of the previous stage. This is because the trace minerals in the coal sample chemically react to produce more magnetic substances. When the temperature exceeds 350 ℃, the magnetic susceptibility begins to decrease rapidly, and the magnetic susceptibility stabilizes near 0 after the temperature is 500 ℃. The possible reason is that with the increase of temperature, the movement of particles inside the mineral intensifies and affects the orderly arrangement of the magnetic domain and magnetic moment. When the temperature rises to the Curie temperature, this influence reaches its limit and the change tends to be stable.

During the past few decades, pyroelectric sensors have attracted extensive attention due to their prominent features. However, their effectiveness is hindered by low electric output. In this study, the laser processed lithium niobate (LPLN) wafers are fabricated to improve the temperature–voltage response. These processed wafers are utilized to construct pyroelectric sensors as well as human–machine interfaces. The laser induces escape of oxygen and the formation of oxygen vacancies, which enhance the charge transport capability on the surface of lithium niobate (LN). Therefore, the electrodes gather an increased quantity of charges, increasing the pyroelectric voltage on the LPLN wafers to a 1.3 times higher voltage than that of LN wafers. For the human–machine interfaces, tactile information in various modes can be recognized by a sensor array and the temperature warning system operates well. Therefore, the laser modification approach is promising to enhance the performance of pyroelectric devices for applications in human–machine interfaces. [ABSTRACT FROM AUTHOR]

The SnO2 electron transport layer (ETL) serves a critical role in perovskite solar cells. However, the oxygen vacancy defects and excess hydroxyl (–OH) groups in SnO2 always lead to degradation of device performance. Herein, we introduce iminodiacetic acid (IDA) to modify the SnO2 ETL, yielding three key advantages: (1) IDA can neutralize excess –OH groups and passivate the defects in SnO2, diminishing the decomposition of perovskite layer; (2) the IDA-modified SnO2 exhibits superior electron conductivity and film quality, while providing improved energy level alignment with the perovskite layer; and (3) the IDA-modified SnO2 owns superior surface wetting properties that facilitates a more effective perovskite crystallization. Ultimately, the devices based on IDA-modified SnO2 obtain a champion efficiency of 24.02% and enhanced stability. [ABSTRACT FROM AUTHOR]

In the two-step preparation of perovskite solar cells, the ambient temperature is the main factor affecting the performance of the cells and controlling the crystallization of perovskite films. In this paper, we demonstrate the importance of resting temperature in the preparation of perovskite solar cells based on the morphology of PbI2 film and perovskite film. The ambient temperature around the PbI2 film directly influences its morphology after resting, and then affects the morphology of the annealed perovskite film. The experimental results show that the optimum ambient temperature for resting PbI2 is 28 °C at which solar cell conversion efficiency is improved to 22.2%. This study is of great significance to the preparation of high-performance PVSCs. [ABSTRACT FROM AUTHOR]