短纤维对三元乙丙橡胶复合材料性能的影响

研究不同种类短纤维（长度）对三元乙丙橡胶（EPDM）复合材性能的影响。结果表明：芳纶短纤维（简称AF）（9 mm）/玄武岩短纤维（简称BSF）（9 mm）并用比为1/1的复合材料的门尼粘度较小,DIN磨耗量最小（113.51 mm³）,耐烧蚀性能最佳;沉淀法白炭黑与气相法白炭黑的复合材料的基本性能和热稳定性相当;BSF的长度越大,复合材料的耐磨性能和耐烧蚀性能越佳;随着BSF长度的增大,复合材料的Payne效应呈减小趋势,与BSF（3 mm）的复合材料相比,BSF（9 mm）的复合材料的Payne效应最小,BSF（9 mm）分散性最好;在热重分析中,700 ℃时复合材料的质量保持率由大到小依次为BSF（9 mm）/AF（9 mm）并用的复合材料、BSF（3 mm）的复合材料、AF（9 mm）的复合材料、AF（6 mm）的复合材料、AF（3 mm）的复合材料。     

Fatigue resistance and damage mechanisms of 2D woven SiC/SiC composites at high temperatures

Fatigue resistance and damage mechanisms of 2D woven SiC/SiC composites at high temperatures were investigated in this research. Fatigue behavior tests were performed at 1200℃ and 1000°C at 10 Hz and stress ratio of 0.1 for maximum stresses ranging from 80 to 120 MPa, and the fatigue run-out could be defined as 10⁶ cycles. Evolution of the cumulative displacement and normalized modulus with cycles was analyzed for each fatigue condition. Fatigue run-out was achieved at 80 MPa and 1000°C. It could be found that the cycle lifetimes of the composites decreased sharply with the increasing maximum stress and temperature conditions significantly affected the fatigue performance under matrix cracking stress. The cumulative displacement showed no noticeable increase before 1000 cycles and the modulus of the failed specimens decreased before fracture. The retained properties of composites that achieved fatigue run-out, as well as the microstructures, were characterized in order to understand the fatigue behavior and failure mechanisms. The composites exhibited similar fracture morphology with matrix crack extension and glass phase oxidation formation under different conditions. In general, the high-temperature fatigue damage and failure of composites could be affected by combination of stress damage and oxidative embrittlement.     

Integrating Sub-Nano Catalysts into Metal-Organic Framework toward Pore-Confined Polysulfides Conversion in Lithium-Sulfur Batteries

Shuttle effect and sluggish redox kinetics of sulfur species still hinder the practical application of lithium-sulfur batteries (LSBs). Herein, a strategy of integrating sub-nano catalysts into metal-organic framework (MOF) is proposed for developing efficient sulfur host to tackle these issues. The designed MOF host (MOF-TOC) endowed with sub-nano Ti O clusters (TOCs) in the mesopores of MOF can act as an efficient reaction chamber in LSBs. Systematic electrochemical measurements and calculations demonstrate that MOF-TOC can trap and confine lithium polysulfides (LiPSs) via strong chemical interaction. Moreover, the highly active TOCs isolated in different nanopores can accelerate the bidirectional redox reaction of sulfur species through the d-p orbital hybridization with sulfur species. Benefiting from these merits, MOF-TOC delivers LSBs with remarkably improved areal capacity and cycling stability at high sulfur loadings and lean electrolytes. This work gives insight into the rational design of catalyst-containing MOF hosts and will shed light on the development of advanced catalytic hosts for high-performance LSBs.     

呼吸道微生态对晚期非小细胞肺癌患者接受PD-1抑制剂单药治疗疗效影响的探索性研究

目的：探讨呼吸道微生态对晚期非小细胞肺癌（non-small cell lung cancer, NSCLC）患者接受PD-1单药治疗的疗效及预后的影响。方法：本研究设计为回顾性分析，从2018年10月到2021年10月纳入后线接受PD-1抑制剂单药治疗且符合入排标准的晚期NSCLC患者58例。PD-1抑制剂包括卡瑞利珠单抗，信迪利单抗和帕博利珠单抗。通过科室的患者病历记录及医院的电子病历系统整理分析患者的基本人口学资料，接受治疗的疗效数据，生存预后情况及接受治疗过程中的不良反应情况。另一方面，收集患者接受PD-1抑制剂治疗前的深部诱导痰标本，通过16S rRNA基因测序方法检测收集的58例样本的呼吸道菌群情况，分析呼吸道菌群α多样性的指标，并和患者的疗效及预后进行关联分析。结果：58例NSCLC患者符合研究的筛选标准并且均可以评价疗效与不良反应。疗效数据提示PD-1抑制剂治疗晚期NSCLC患者的客观缓解率（ORR）为19.0%［95%置信区间（CI）：9.9%-31.4%］，疾病控制率（DCR）为55.2%（95%CI：41.5%-68.3%）。通过后续的访视获取的预后数据表明58例NSCLC患者的中位PFS为3.2个月（95%CI: 2.29-4.11），中位OS为10.5个月（95%CI: 5.58-15.43）。呼吸道菌群分析结果根据Shannon多样性指标的高低将58例患者分为高α多样性组（H组）和低α多样性组（L组），分别为30例和28例。关联性结果提示H组和L组的ORR分别为23.3%和17.9%（P=0.380）。预后结果表明H组和L组的中位PFS分别为3.8个月和2.8个月，差异具有统计学意义（P=0.034）。结论：PD-1单药在晚期NSCLC患者后线治疗中具有初步的疗效和预后。呼吸道菌群分析中高的α多样性菌群的患者具有较好的预后，研究结论尚需要大样本前瞻性研究进一步验证。     

Low-temperature reactive hot-pressing of Ta0.2Hf0.8C–SiC ceramics at 1700°C

Temperature above 2000°C and additional pressure is generally required to achieve the full densification of Ta_xHf_1−xC-based ceramics. This work proposed a novel method to fabricate dense Ta_0.2Hf_0.8C ceramics at relatively low temperature. Using a small amount of Si as a sintering aid, Ta_0.2Hf_0.8C was densified at 1700°C by reactive hot-pressing (RHP), with SiC formed in situ. Microstructure evolution mechanisms of the ceramics during RHP were investigated. The effect of silicon content on the densification and mechanical properties of the ceramics was revealed. It is indicated that the apparent porosity of the Ta_0.2Hf_0.8C–SiC ceramics was as low as 0.5%, whereas bending strength and fracture toughness of the ceramics were as high as ∼637 MPa and 6.7 MPa m^1/2, respectively, when the silicon content was 8 wt.%. This work provides a new idea for the low-temperature densification of Ta_xHf_1−xC and other ultrahigh temperature ceramics with high performance.     

In situ synthesis of cobalt silicide particle reinforcing and coloring Si3N4 ceramics

In this paper, silicon nitride (Si₃N₄) ceramics with black color and high toughness were fabricated by gas pressure sintering and characterized by X-ray diffraction, Raman, scanning electron microscopy, EDS, and transmission electron microscopy. The in situ formed cobalt silicide was confirmed to contribute to the black color through the introduction of CoO. Due to the addition of CoO, the growth of β-Si₃N₄ grains is promoted, forming elongated grains, and eventually forms the self-reinforcing microstructure. However, with adding excessive CoO, interfacial debonding is found between cobalt silicide and Si₃N₄ matrix and a decrease in strength was resulted. The optimum composition is 1 mol% CoO in Si₃N₄, with the fracture toughness of 9.9 ± 0.3 MPa m^1/2, flexural strength of 826.1 ± 46.0 MPa, and a much darker black color. The mechanism of color formation is discussed where the black color derives mainly from the metallic silicon and additionally the porosity.     

Two-Dimensional Ultrathin Graphic Carbon Nitrides with Extended π-Conjugation as Extraordinary Efficient Hydrogen Evolution Photocatalyst

Construction of 2D graphic carbon nitrides (g-CN_x) with wide visible light adsorption range and high charge separation efficiency concurrently is of great urgent demand and still very challenging for developing highly efficient photocatalysts for hydrogen evolution. To achieve this goal, a two-step pyrolytic strategy has been applied here to create ultrathin 2D g-CN_x with extended the π-conjugation. It is experimentally proven that the extension of π-conjugation in g-CN_x is not only beneficial to narrowing the bandgap, but also improving the charge separation efficiency of the g-CN_x. As an integral result, extraordinary apparent quantum efficiencies (AQEs) of 57.3% and 7.0% at short (380 nm) and long (520 nm) wavelength, respectively, are achieved. The formation process of the extended π-conjugated structures in the ultrathin 2D g-CN_x has been investigated using XRD, FT-IR, Raman, XPS, and EPR. Additionally, it has been illustrated that the two-step pyrolytic strategy is critical for creating ultrathin g-CN_x nanosheets with extended π-conjugation by control experiments. This work shows a feasible and effective strategy to simultaneously expand the light adsorption range, enhance charge carrier mobility and depress electron-hole recombination of g-CN_x for high-efficient photocatalytic hydrogen evolution.     

Colored Si3N4 ceramics via constructing Nd3+ doped core-shell structures

Si₃N₄ ceramics have been attractive casing materials for electronics devices under the 5th generation mobile communication technology because of its outstanding comprehensive properties. However, single color cannot meet the needs of most consumers. Here, a typical strategy, involving forming core-shell structures by utilizing Nd₂O₃-MgO-YAG system, is proposed to rich color. Scanning transmission electron microscope-energy dispersive X-ray spectrometry results confirm the presence of core-shell structures in the silicon nitride matrix, and the core is pore and the shell is Nd-enriched liquid phase. The Nd-rich core-shell structure as the color center makes the silicon nitride appear cyan or blue.     

Synthesis mechanism and phase stability analysis of z-Y2Si2O7 by sol-gel process

Synthesis mechanism and phase stability analysis of square z-Y₂Si₂O₇ was studied in this research by using Y(NO₃)₃·6H₂O and tetra ethoxy orthosilicate as precursors. The concentration of the precursor directly affects the degree of hydrolysis of tetra ethoxy orthosilicate and the uniformity of the gel by Fourier transform infrared spectral analysis. The thermogravimetric analysis shows that the crystallization temperature of the precursor decreases gradually with the decrease of precursor concentration. Because the low precursor concentration is beneficial to the formation of the homogeneous molecular level of yttrium silica network gel. Finally, the crystallized z-Y₂Si₂O₇ was detected by X-ray diffraction and further verified by a transmission electron microscope after calcining at 800°C. The maximum stable temperature of z-Y₂Si₂O₇ was less than 1050°C. The microscopic morphology of z-Y₂Si₂O₇ is square nanoparticles. The grain size of z-Y₂Si₂O₇ increases with the decrease of precursor concentration.     

Encapsulating Ni Nanoparticles into Interlayers of Nitrogen-Doped Nb2CTx MXene to Boost Hydrogen Evolution Reaction in Acid

Design and development of low-cost and highly efficient non-precious metal electrocatalysts for hydrogen evolution reaction (HER) in an acidic medium are key issues to realize the commercialization of proton exchange membrane water electrolyzers. Ni is regarded as an ideal alternative to substitute Pt for HER based on the similar electronic structure and low price as well. However, low intrinsic activity and poor stability in acid restrict its practical applications. Herein, a new approach is reported to encapsulate Ni nanoparticles (NPs) into interlayer edges of N-doped Nb₂CT_x MXene (Ni NPs@N-Nb₂CT_x) by an electrochemical process. The as-prepared Ni NPs@N-Nb₂CT_x possesses Pt-like onset potentials and can reach 500 mA cm⁻² at overpotentials of only 383 mV, which is much higher than that of N-Nb₂CT_x supported Ni NPs synthesized by a wet-chemical method (w- Ni NPs/N-Nb₂CT_x). Furthermore, it shows high durability toward HER with a large current density of 300 mA cm⁻² for 24 h because of the encapsulated structure against corrosion, oxidation as well as aggregation of Ni NPs in an acidic medium. Detailed structural characterization and density functional theory calculations reveal that the stronger interaction boosts the HER.