In-situ synthesis of 15R-Sialon from Al-Si3N4-Al2O3 composite at 1500°C via liquid-phase sintering

In this study, alumina-based composite with 12 wt% Al and 16 wt% Si₃N₄ was designed to achieve the synthesis of 15R-Sialon reinforced alumina composite. To investigate the reaction mechanism, two-step sintered Al-Si₃N₄-Al₂O₃ samples at different temperatures ranging from 600°C to 1500°C were prepared and characterized via X-ray diffraction and scanning electron microscope (SEM). The results revealed that 15R-Sialon was synthesized at 1500°C through a novel liquid Si phase sintering and Si₃N₄ played as a precursor and a reactant. First, Si₃N₄ precursor reacted with Al to form intermediate phases AlN and Si, which were not further transformed below 1400°C. When the sintering temperature was 1500°C, the formed Si presented as a liquid phase, under the influence of which plate-like15R-Sialon was generated from Al₂O₃, residual Si₃N₄, and derived AlN. The obtained Si was also involved in the synthesis of 15R-Sialon and completely transformed. In addition to the AlN from Si₃N₄, the AlN deriving from the nitridation of Al may not react with liquid Si. Compared to 15R-Sialon from liquid Si, plate-like 15R-Sialon with smaller size was generated from AlN, SiO, and O₂.     

An overview of reactive hydride composite (RHC) for solid-state hydrogen storage materials

Hydrogen storage using the metal hydrides and complex hydrides is the most convenient method because it is safe, enables high hydrogen capacity and requires optimum operating condition. Metal hydrides and complex hydrides offer high gravimetric capacity that allows storage of large amounts of hydrogen. However, the high operating temperature and low reversibility hindered the practical implementation of the metal hydrides and complex hydrides. An approach of combining two or more hydrides, which are called reactive hydride composites (RHCs), was introduced to improve the performance of the metal hydrides and complex hydrides. The RHC system approach has significantly enhanced the hydrogen storage performance of the metal hydrides and complex hydrides by modifying the thermodynamics of the composite system through the metathesis reaction that occurred between the hydrides, hence enhancing the kinetic and reversibility performance of the composite system. In this paper, the overview of the RHC system was presented in detail. The challenges and perspectives of the RHC system are also discussed. This is the first review report on the RHC system for solid-state hydrogen storage.     

Practical in-storage interventions to control foodborne pathogens on fresh produce

Although tremendous efforts have been made to ensure fresh produce safety, various foodborne outbreaks and recalls occur annually. Most of the current intervention strategies are evaluated within a short timeframe (less than 1 h), leaving the behavior of the remaining pathogens unknown during subsequent storages. This review summarized outbreak and recall surveillance data from 2009 to 2018 obtained from government agencies in the United States to identify major safety concerns associated with fresh produce, discussed the postharvest handling of fresh produce and the limitations of current antimicrobial interventions, and reviewed the intervention strategies that have the potential to be applied in each storage stage at the commercial scale. One long-term (up to 12 months) prepacking storage (apples, pears, citrus among others) and three short-term (up to 3 months) postpacking storages were identified. During the prepacking storage, continuous application of gaseous ozone at low doses (≤1 ppm) is a feasible option. Proper concentration, adequate circulation, as well as excess gas destruction and ventilation systems are essential to commercial application. At the postpacking storage stages, continuous inhibition can be achieved through controlled release of gaseous chlorine dioxide in packaging, antimicrobial edible coatings, and biocontrol agents. During commercialization, factors that need to be taken into consideration include physicochemical properties of antimicrobials, impacts on fresh produce quality and sensory attributes, recontamination and cross-contamination, cost, and feasibility of large-scale production. To improve fresh produce safety and quality during storage, the collaboration between researchers and the fresh produce industry needs to be improved.     

Mild hydrogen production from the hydrolysis of Al–Bi–Zn composite powder

The development of mild hydrogen-generating materials is of great significance to improve the working life of hydrogen–oxygen fuel cells. In this study, Al–Bi–Zn composite powders were designed by phase diagram calculation and then prepared via the gas atomization method. The results indicated that the conversion yield of Al–12Bi–7Zn (wt.%) powder reached 98% with stable hydrogen production within 280 min at 50 °C. When composite powder reacted with NaCl solution to produce hydrogen, the dormant period of the reaction process was significantly shortened, but the conversion rate was slightly reduced. Additionally, the evolution of powder morphology during the reaction was investigated. The results showed that the continuous cracking of the powder led to the continuous exposure of fresh Al to react.     

EFPI-FBG复合光纤传感器高温大应变试验研究

由于缺乏航空发动机/燃气轮机服役环境下叶片温度、应变有效性检测的技术与装置，所以工作叶片的温度环境、载荷环境和应变分布等关键数据的缺失是故障检修工作中的最大困难之一。采用非本征型法布里-珀罗(Extrinsic Farby Perot Interferometric,EFPI)与光纤光栅(Fiber Bragg Grating,FBG)传感技术，研制了一种基于单模光纤的EFPI FBG复合光纤传感器及其解调设备。通过搭建高温拉伸试验平台，开展了基于DZ125材料试件的复合光纤传感器高温、大应变测量的性能测试。试验结果表明：复合光纤传感器的工作温度范围为26 ℃~1 100 ℃，温度测量精度不超过全量程的5%，分辨率为0.066 ℃；F-P传感器的应变测量范围为0~19 468 με，在1 100 ℃下的相对误差为1.96%，分辨率为0.053 με。     

Design and computational analysis of a metal hydride hydrogen storage system with hexagonal honeycomb based heat transfer enhancements-part A

In this study, design and performance analysis is carried out for a 10 kWh metal hydride based hydrogen storage system. The system is equipped with distinctive aluminium hexagonal honeycomb based heat transfer enhancements (HTE) having higher surface area to volume ratio for effective heat transfer combined with low system weight addition. The system performance was studied under different operating conditions. The optimum absorption condition was achieved at 35 bar with water at room temperature as heat transfer fluid where up to 90% absorption was completed in 7200 s. The performance of the reactor was observed to significantly improve upon the addition of the HTE network at a minimal system weight penalty.     

Li0.95Na0.05MnPO4/C nanoparticles compounded with reduced graphene oxide sheets for superior lithium ion battery cathode performance

Sodium-substituted LiMnPO₄/C/reduced graphene oxide (LNMP@rGO) was synthesized in this study via freeze drying and carbon thermal reduction method with graphene oxide as carbon source. Sodium ion doping is optimized and rGO effects are evaluated by XRD, SEM, TEM, BET, Raman, and electrochemical performance measurements. Well-distributed nanoparticles with average size of ~50?nm are evenly distributed on the surface or intercalation between rGO layers, resulting in a porous ion/electronic conductive network. Compared to 122.3?mA?h?g^?1 in unmodified LNMP, the best LNMP@rGO (20?mg rGO) exhibits an excellent initial discharge capacity of 150.4?mA?h?g^?1 at 0.05?C at 122.9% of the initial capacity. The capacity retention rate is 95.8% of the initial capacity after 100 cycles at 1?C. Capacity of 101.2?mA?h?g^?1 is preserved even at rates as high as 10?C.     

Gas‐phase removal of indoor volatile organic compounds and airborne microorganisms over mono‐ and bimetal‐modified (Pt,Cu, Ag) titanium(IV) oxide nanocomposites

The photocatalytic deactivation of volatile organic compounds and mold fungi using TiO₂ modified with mono‐ and bimetallic (Pt, Cu, Ag) particles is reported in this study. The mono‐ and bimetal‐modified (Pt, Cu, Ag) titanium(IV) oxide photocatalysts were prepared by chemical reduction method and characterized using XRD, XPS, DR/UV‐Vis, BET, and TEM analysis. The effect of incident light, type and content of mono‐ and bimetallic nanoparticles deposited on titanium(IV) oxide was studied. Photocatalytic activity of as‐prepared nanocomposites was examined in the gas phase using LEDs array. High photocatalytic activity of Ag/Pt‐TiO₂ and Cu/Pt‐TiO₂ in the reaction of toluene degradation resulted from improved efficiency of interfacial charge transfer process, which was consistent with the fluorescence quenching effect revealed by photoluminescence (PL) emission spectra. The photocatalytic deactivation of Penicillium chrysogenum, a pathogenic fungi present in the indoor environment, especially in a damp or water‐damaged building using mono‐ and bimetal‐modified (Pt, Cu, Ag) titanium(IV) oxide was evaluated for the first time. TiO₂ modified with mono‐ and bimetallic NPs of Ag/Pt, Cu, and Ag deposited on TiO₂ exhibited improved fungicidal activity under LEDs illumination than pure TiO₂.     

碳纤维复合材料薄壁圆筒的轴向导热系数测试

碳纤维复合材料薄壁圆筒为各向异性导热，其轴向导热系数是筒体温度场理论计算、成型工艺优化的重要参数。碳纤维复合材料圆筒由于较小的截面面积给筒体加热、热量有效传递带来了较大困难。本文以平板材料导热系数的稳态法测试国家标准为基础，基于傅里叶一维稳态导热原理，设计了一套用于薄壁圆筒轴向导热系数测试的装置，采用双试件对称加热、辐射换热防护及热对流环境控制等实现了热量沿筒体轴向的有效传导，利用该装置对导热系数已知的铝筒进行测试，验证了该装置设计的可行性，得到了碳纤维复合材料薄壁圆筒的轴向导热系数为（4.60±0.13） W/(m•K)。