Low concentration CO gas sensor constructed from MoS2 nanosheets dispersed SnO2 nanoparticles at room temperature under UV light

In consideration of the different electron structure-associated physical properties and internal sensing merits of MoS₂ and SnO₂, this work reports a nanocomposite with unique structure of MoS₂ nanosheets dispersed SnO₂ nanoparticles. The sensing performance of MoS₂/SnO₂ sensor toward low concentration CO was investigated at room temperature under the UV light illumination. It was found that MoS₂/SnO₂ sensor shows improved CO gas response (R ~ 4.97 at 40 ppm CO) compared with pure SnO₂ (R ~ 3.27 at 40 ppm CO), which is due to the unique structure and the formation of heterostructure between MoS₂ and SnO₂. Moreover, the fabricated sensor also exhibits fast response and recovery time (43 s/36 s). The sensor provides a potential platform for monitoring CO gas at room temperature.     

有机磷光体系及其研究进展

室温磷光性有机物由于三重态激子的参与和相对较慢的衰变速率，使其具有较长波长及长寿命的特性，让该类型化合物在光学器件、光催化反应、生物成像等领域中具有广泛的应用前景。目前构筑室温磷光有机体系主要是通过促进自旋轨道耦合和抑制三重态到基态的非辐射衰变来完成。对近年来室温磷光有机体系的发展进行归纳和总结，针对如何设计室温磷光有机体系提出了几种方法，并分析其原理，对未来室温磷光有机体系的发展与应用进行了展望。     

Effects of grain boundary volume fraction on the threshold dose of irradiation-induced SiC amorphization at 30 °C

SiC fiber-reinforced matrix composites (SiC_f/SiC) have limited applications because of the irradiation-induced shrinkage of SiC fibers; the fiber shrinkage mechanism is still not fully understood. In this study, we tried to clarify the effect of annealing temperature on the proportion of fiber shrinkage and swelling. SiC_f/SiC was irradiated at 30 °C to 100 dpa, and the deterioration of mechanical properties was evaluated after irradiation. The compressive displacement of > 60% of the fibers before failure increased to more than 1.5 times that of the as-received specimen. Significant swelling was observed, indicating that the proportion of swelling was higher than that of shrinkage after irradiation. This can be attributed to the amorphization of SiC, and its amorphization threshold dose increased with decreasing grain boundary volume fraction. The findings of this study provide insights into the mechanism of irradiation-induced fiber amorphization and can be useful in developing improved SiC_f/SiC.     

Microstructure,optical and magnetic properties of TiO2/CuO nanocomposites synthesized by a two-step method

TiO₂/CuO composites in different ratios were prepared via a two-step method. X-ray diffraction and transmission electron microscopy results indicated that part of Cu²⁺ substituted Ti⁴⁺ in the TiO₂ lattice in the composite, leading to Cu²⁺-substituted sites in the TiO₂ lattice as well as Cu²⁺ species located in the CuO lattice. Scanning electron microscopy revealed a morphology change in the sample from a three-dimensional structure to a two-dimensional structure while forming an interface between TiO₂ and CuO. X-ray photoelectron spectroscopy and Raman spectra showed that there are oxygen vacancies (V_O) and Ti³⁺ in the lattice. UV–vis absorption spectra exhibited a widening of the absorption range and a decrease in the bandgap with increasing amount of CuO in the TiO₂/CuO composites. Additionally, the composites exhibited room-temperature ferromagnetism (RTFM), as can be explained by the indirect double-exchange model, which is related to V_O and the exchange interaction between the 3d orbitals of Ti³⁺ and Ti⁴⁺ at the interface.     

The mechanism and sorption kinetic analysis of hydrogen storage at room temperature using acid functionalized carbon nanotubes

The present work investigates the effect of acid functionalization of multiwalled carbon nanotubes (MWCNTs) on the physisorption based mechanism of hydrogen storage at room temperature. For this purpose, a suite of functionalized CNT samples is synthesized and subjected to a comprehensive range of material characterization techniques and hydrogen storage measurements. Nitric acid (HNO₃) and the mixture of sulphuric acid and nitric acid (H₂SO₄:HNO₃) are used for the synthesis at oxidation temperatures of 80 °C and 100 °C. Electron microscopy and X-ray photoelectron spectroscopy results reveal that acid functionalization causes major alternation in the physicochemical properties of the CNTs due to the varied concentration of oxygen functional groups. Particularly, the H₂SO₄:HNO₃ functionalized sample at 100 °C is found to have the highest interlayer spacing, oxygen to carbon ratio (26.09 at. %), defect content, and specific surface area (215.3 m²/g). These features collectively contribute to substantially improved hydrogen storage properties, including a ～150% increase in the hydrogen storage capacity at 298 K and 50 bar. Furthermore, kinetic analysis shows that the desorption follows a multiple diffusion process which is sensitive to the oxygen functional groups and structural defects, hence reducing the rate of desorption; whereas the adsorption is controlled by a more rapid, three-dimensional diffusion process.     

Development of a Ru catalyst supported on HY zeolite for the oxidative decomposition of NH3 triggered at room temperature

On-site hydrogen production from the oxidative decomposition of NH₃ with a catalyst is highly required in the countryside where external heat is hardly supplied. In this study, Ru-based zeolite catalysts were prepared by impregnation and subsequent washing using RuCl₃·3H₂O and HY zeolite or H-MOR zeolite for the oxidative decomposition of NH₃. The H-MOR-supported Ru catalyst could not be self-heated by feeding 80% NH₃/20% O₂ to the catalyst bed at room temperature. By contrast, the HY-supported Ru catalyst underwent self-heating to approximately 773 K upon feeding the reactants owing to the heat released by NH₃ adsorption and oxidation, leading to excellent performance for the oxidative decomposition of NH₃ during five cycles of start-up tests. Characterization results indicated that the Cl-free Ru/HY catalyst exhibited self-heating due to the presence of small well-dispersed Ru metal particles and a large amount of surface acidic sites.     

Autonomous detection and loading of ore piles with load–haul–dump machines in Room & Pillar mines

Automation of machines in underground mines is a topic with increasing interest, both for research and industrial applications. Autonomous load–haul–dump (LHD) machines need to load material successfully before dumping it into a crusher or an ore pass. The autonomous loading method must be robust to enable reliable operation of the LHD during long periods of time. In this work, a method to perform autonomous loading in Room & Pillar mines is presented. It is based on detecting all ore piles in real-time, and then computing attack poses in each pile. Then, a positioning process is performed to get the machine in front of the selected ore pile, and an excavation algorithm is executed for loading until the bucket is filled. The proposed method is able to detect multiple ore piles, with different slopes and sizes, and to consider different possible trajectories for attacking and loading the most feasible pile. The method was tested in the Werra Potash Mine, under real operational conditions. The results show that the method can load about 80% of the material that an experienced operator can load. Also, the success rate of the autonomous loading process is very high, being able to load enough material in all trials, and performing successfully the full procedure in 88% of the cases. Thus, the proposed autonomous loading method is a suitable alternative to be used in Room & Pillar mines.     

Pt=Pd separation modified Ti3C2TX MXene for hydrogen detection at room temperature

Hydrogen sensing with a fast response at room temperature is still a challenge. In this study, a novel Pt=Pd/Ti₃C₂T_X hydrogen sensor was prepared by a straightforward hydrothermal chemical reduction method. The Pt=Pd/Ti₃C₂T_X was characterized by X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy. The experimental results showed that the response of the Pt=Pd/Ti₃C₂T_X sensor was 24.6% and the response/recovery time was 6/8 s in the case of 200 ppm hydrogen at room temperature. The Pt=Pd/Ti₃C₂T_X sensor could detect the hydrogen concentration as low as 1 ppm. Besides, the Pt=Pd/Ti₃C₂T_X sensor exhibited good linearity, long-term stability, good repeatability, and high selectivity. The Pt=Pd/Ti₃C₂T_X sensor has great potential in the field of hydrogen energy.     

SnO2 submicron porous cube derived from metal-organic framework for n-butanol sensing at room temperature

SnO₂ is a typical metal oxide semiconductor gas sensitive material, which has been studied deeply. However, pure SnO₂ sensing materials usually have good performance at high operating temperatures. In this study, we reported an n-butanol sensor with high selectivity and fast response based on SnO₂ submicron porous cube prepared by heating and decomposing the Sn-based metal-organic framework material (Sn-MOF) in air at a certain temperature. SnO₂ submicron porous cube prepared at 450 °C shows good response and selectivity for n-butanol. And it has a response (%) of 175% to 100 ppm n-butanol and a relatively fast response/recovery time of 184 s/183 s at room temperature. The (110) crystal plane with sufficient oxygen-rich vacancy can adsorb O₂ and n-butanol molecules more effectively. Therefore, its sensitivity to n-butanol gas can be significantly improved. This work provides a good idea for further research on pure metal oxide semiconductor room temperature gas sensors.