Fabrication and properties of Si3N4 based ceramics using combustion synthesized powders

Silicon nitride (Si₃N₄) based ceramics were fabricated with β-SiAlON and Si₃N₄ powders synthesized by combustion synthesis method via power injection molding (PIM). In the PIM process, the solids loading for each material was first determined from the results of the torque rheometer experiment. The mixing process was repeated to produce the homogeneous feedstock, and homogeneity of feedstocks was evaluated by observing the shear viscosity with time at a constant shear rate. The rheological behavior of feedstocks was investigated using capillary rheometer. It found that both feedstocks have no problem in injection molding. The binder decomposition behavior was also investigated, and a wax-polymer binder system was nearly removed by the optimized solvent and thermal debinding processes. Thereafter, the debound samples were sintered at 1750 and 1800 °C for 4 h in nitrogen atmosphere. Regardless of sintering temperature, the relative density of higher than about 96% was achieved. When comparing mechanical properties including bending strength, Vickers hardness and fracture toughness, Si₃N₄ with 2 wt% Y₂O₃ and 5 wt% Al₂O₃ (Si₃N₄+2Y5A) had higher values than β-SiAlON with 4 wt% Y₂O₃ (β-SiAlON+4Y) regardless of sintering temperature. It was supported by observing the microstructures of the plasma-etched samples.     

废弃液晶面板中液晶材料的热解特性

作为废弃液晶面板的重要组成部分,液晶材料中含有芳环、氰基、氟、氯、溴等基团,若随意丢弃或采用不当的处置方式将严重污染环境。本研究拟利用热解处理技术实现对液晶材料的无害化处理,探究了废旧薄膜晶体管液晶显示器中液晶材料的热解特性。液晶材料的热重分析结果表明,液晶材料的主要热解温度为300～500?C;热解实验表明,热解温度对液晶材料热解产物的影响较大,其中300?C和500?C条件下主要生成了双环己烷类、联苯类等化合物,而在800?C条件下主要生成多环芳烃;此外,考察了热解温度、氮气流量及固相停留时间对液晶去除率的影响,在优化条件下液晶的去除率可达94.2%。本研究为废旧液晶面板中液晶材料的无害化处理提供了技术参数和理论参考。     

Polymer derived ZrO2 reinforced SiC-ZrB2 polycrystalline fiber

Most polycrystalline SiC-based fibers were prepared at a sintering temperature higher than 1600 °C. In this work, a ZrO₂ reinforced SiC-ZrB₂ polycrystalline fiber was prepared at 1400 °C via the polymer-derived ceramic method from a new Zr- and B-containing polycarbosilane. The morphology and microstructure of the polycrystalline nanocomposite fiber were studied using XRD, XPS, EDS, SEM, and TEM. The results showed that t-ZrO₂ was formed at relatively lower temperature (<1000 °C). The most interesting result is that the polycrystalline nanocomposite SiC-ZrB₂ was generated after heat-treatment at 1400 °C, producing an excellent ZrO₂ reinforced SiC-ZrB₂ polycrystalline fiber. The present study provides a novel strategy for the fabrication of SiC-based polycrystalline fiber at a relatively low temperature.     

Curing performance and print accuracy of oxidized SiC ceramic via vat photopolymerization

To improve the print quality of SiC ceramic, an amorphous SiO₂ layer is prepared on the surface of SiC by oxidation (SiC@SiO₂). The changes in curing depth and width direction of SiC@SiO₂ curing sheets with different degrees of oxidation were investigated. The results showed that curing depth increased while curing width decreased with an increasing degree of oxidation. The edge morphologies of SiC@SiO₂ curing sheets changed from serration to flat shape with increasing degree of oxidation, and uneven overcuring regions appear in the width direction. Additionally, 12% SiC@SiO₂ ceramic was fabricated via vat photopolymerization combined with reaction sintering. The dimensional deviation ratio of printed green bodies increased with decreasing printed line width and pore diameter. The minimum printed line width of 329 μm and pore diameter of 483 μm with good print quality were obtained. Furthermore, the flexural strength of 225.4 MPa and bulk density of 2.77 g cm⁻³ for sintered 12% SiC@SiO₂ parts were obtained.     

In-situ TEM investigations on the microstructural evolution of SiC fibers under ion irradiation: Amorphization and grain growth

SiC/SiC composites are attractive candidates for many nuclear systems. As reinforcements, SiC fibers are critical to the in-service performance of composites. In this work, the temperature effects on the irradiation-induced microstructural evolution of Cansas-III SiC fibers were investigated using in-situ transmission electron microscopy (TEM). With in-situ 800 keV Kr ion irradiation, at room temperature (RT) the SiC fiber experienced heterogeneous amorphization and became completely amorphous at ～2.6 dpa. Above the critical temperature of crystalline-to-amorphous (T_c), SiC fibers underwent a simultaneous process of carbon packet disappearance and nano-grain growth at 300 °C and 800 °C. Possible mechanisms were discussed.     

某有机化工企业危废仓库挥发性有机物的治理案例

来源广、浓度低、成分复杂的挥发性有机物(volatile organic compounds, VOCs)一直是大气污染防治的难点。以某化工企业危废仓库有机废气治理项目为例,设计采用"水洗+气雾分离+活性炭吸附"的组合工艺对危废仓库内的VOCs进行处理并达标排放。该工艺具有运行稳定,维护成本低等优点,可以为易产生低浓度、成分复杂的VOCs的化工企业原料仓库、危废仓库、污水处理站等提供切实可行、高效治理的参考依据。     

Highly Dispersed NiO Clusters Induced Electron Delocalization of Ni?N?C Catalysts for Enhanced CO2 Electroreduction

Oxygen-regulated Ni-based single-atom catalysts (SACs) show great potential in accelerating the kinetics of electrocatalytic CO₂ reduction reaction (CO₂RR). However, it remains a challenge to precisely control the coordination environment of Ni O moieties and achieve high activity at high overpotentials. Herein, a facile carbonization coupled oxidation strategy is developed to mass produce NiO clusters-decorated Ni N C SACs that exhibit a high Faradaic efficiency of CO (maximum of 96.5%) over a wide potential range (−0.9 to −1.3 V versus reversible hydrogen electrode) and a high turnover frequency for CO production of 10 120 h⁻¹ even at the high overpotential of 1.19 V. Density functional theory calculations reveal that the highly dispersed NiO clusters induce electron delocalization of active sites and reduce the energy barriers for *COOH intermediates formation from CO₂, leading to an enhanced reaction kinetics for CO production. This study opens a new universal pathway for the construction of oxygen-regulated metal-based SACs for various catalytic applications.     

废锂离子电池中锂提取技术研究进展

作为一种关键原材料,锂是生产新能源汽车锂离子电池必需的战略金属。随着新能源汽车产业的快速发展,对锂的需求量持续骤增。然而,我国锂矿石等一次资源储量低,对外依存度目前已高达70%,难以满足快速增长的市场需求,供需矛盾日渐突出。因此,高效清洁提取废锂离子电池中的锂必将成为锂资源的重要补充,对有效避免废锂离子电池对生态环境和人体健康的二次污染风险、保障战略金属锂的安全供给和新能源汽车行业的可持续发展意义重大。鉴于湿法冶金具有回收率高、回收产物纯度高、能耗低等优点,本研究综述了近年来以湿法冶金为主提取废锂离子电池中锂的研究进展,重点分析了废锂离子电池预处理、浸出、锂分离与提取的主要方法及其优缺点,并提出了进一步强化选择性提取锂相关技术研发及废锂离子电池全组分清洁利用的建议,同时对废锂离子电池回收工艺的发展趋势及前景进行了展望。     

Six- and four-coordinated zinc(II) complexes exhibit strong blue fluorescent properties

A new ligand, 4-(p-chlorophenyl)-1,2,4-triazole (^pCltrz), and its complexes, [Zn(^pCltrz)₆]₂(ClO₄)₂ · H₂O (1) and [Zn(^pCltrz)₂Cl₂] (2), were synthesized. The structure of 1 exhibits the first case that zinc(II) ion coordinated with six triazole ligands to form octahedral environment. Both 1 and 2 display very strong blue photoluminescence as the result of the fluorescence from the intraligand emission excited state.