Preparation of carbon/carbon‐ultra high temperature ceramics composites with ultra high temperature ceramics coating

In order to increase the oxidation resistance of carbon/carbon (C/C) composites at long‐term high temperature, C/C‐Ultra High Temperature Ceramics composites (UHTCs) with a dual‐layer UHTCs oxidation coating was successfully designed and fabricated. The microstructure and ablation resistance were investigated and discussed. After ablation in arc‐heated wind tunnel with temperature being 2200°C for 1000s, the mass ablation rate and linear ablation rate were ?1.9 × 10^?2 mg/cm²s and 2.9 × 10^?5 mm/s, respectively. The formation of thermodynamically compatible oxide scale including ZrO₂ skeleton and SiO₂ or Zr–Si–O glass on the surface were mainly contributed to the excellent ablation resistance of the composite.     

Assessment of conversion efficiency of Cr4+ ions by aliovalent cation additives in Cr:YAG ceramic for edge cladding

0.25at.% Cr:YAG ceramics were successfully fabricated as the edge cladding of Yb:YAG transparent ceramic slabs through vacuum sintering of co‐precipitated powders, using oxide additives to introduce different cations. The effects of various cation additives (Si⁴⁺, Ca²⁺, and Si⁴⁺ + Ca²⁺) on the conversion efficiency of Cr⁴⁺ ions and optical characteristics of the Cr:YAG edge cladding were investigated. Measurements of the absorption spectra of the Cr:YAG ceramics without any additives revealed 2 absorption bands centered at 430 nm and 600 nm, which imparted the sample with a green color. The introduction of only Si⁴⁺‐bearing additive did not promote the transition of Cr ions from the 3+ to 4+ state. Theoretical analysis and experimentation revealed that the addition of CaO not only enhanced the microstructure and improved the transmittance of the Cr:YAG ceramic, but also introduced vacancies that assisted in the formation of Cr⁴⁺ ions. It was determined that CaO has the same effect on the conversion efficiency of Cr⁴⁺ ions whether it is added as a single additive or in combination with SiO₂. The underlying mechanisms by which these aliovalent cation additives influence the formation of Cr⁴⁺ ions and affect optical properties are discussed in detail. High quality composite ceramics with Yb:YAG transparent ceramic slabs and dark brown‐colored Cr⁴⁺: YAG ceramic edge cladding were achieved through the addition of 0.05 wt.% CaO to the edge cladding, with no interfacial effects between the 2 regions being observed.     

胜利油田沾3区块内源微生物室内模拟激活实验研究

在考察了国内外内源微生物采油技术研究情况的基础上,采用1^#～4^#激活剂配方对沾3区块注入水中微生物群落进行了选择性激活,对激活后总菌、有益菌、有害菌的数量及表面张力进行了检测,并进行了室内模拟驱油实验。实验结果表明,1^#～4^#激活剂配方能有效刺激有益菌的生长,同时对有害菌SRB实现了较为有效的抑制,压力和多孔介质对微生物的生长会产生一定的影响,多孔介质的影响较压力的影响要显著一些,KNO₃的激活效果及提高残余油采收率的效果要优于NH₄NO₃,硝酸盐含量从0.1 %到0.2 %的增加能增加有益菌的数目,但对采收率的提高作用并不明显。室内模拟驱油实验表明,在水驱基础上内源微生物驱可提高采收率达6%以上。     

多孔介质反应体系中的耦合扩散效应

采用不可逆过程热力学方法研究固有强吸热化学反应的多孔介质物质体系,建立了描述该体系内各不可逆过程交互耦合的数学模型,应用有限容积隐式方法数值求解,并以煅烧石灰石为例,计算分析了热扩散现象和达福尔效应对多孔介质体系内传热、传质和化学反应的影响规律。结果表明,在Peclet准数较小的情况下,不能忽略Soret效应和Dufour效应的影响,Soret效应和Dufour效应会加快反应器内产物气体和热量传出的速度,使得颗粒物料层内产物气体浓度和主气流温度都相应降低,固体转化率减小。     

Mechanical properties and grain orientation evolution of zirconium diboride-zirconium carbide ceramics

The effect of ZrC on the mechanical response of ZrB₂ ceramics has been evaluated from room temperature to 2000 °C. Zirconium diboride ceramics containing 10 vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB₂. The addition of ZrC also increased fracture toughness from $～3\text{.5}\text{MPa}\sqrt{\text{m}}$ for nominally pure ZrB₂ to $～4\text{.3}\text{MPa}\sqrt{\text{m}}$ due to residual thermal stresses. The toughness was comparable with ZrB₂ up to 1600 °C, but increased to $4\text{.6}\text{MPa}\sqrt{\text{m}}$ at 1800 °C and 2000 °C. The increased toughness above 1600 °C was attributed to plasticity in the ZrC at elevated temperatures. Electron back-scattered diffraction analysis showed strong orientation of the ZrC grains along the [001] direction in the tensile region of specimens tested at 2000 °C, a phenomenon that has not been observed previously for fast fracture (crosshead displacement rate = 4.0 mm min^?1) in four point bending. It is believed that microstructural changes and plasticity at elevated temperature were the mechanisms behind the ultrafast reorientation of ZrC.     

陶瓷抛光机磨头及其驱动部件的建模与动态特性分析

通过对陶瓷抛光机磨头及其驱动系统分别建立扭转振动模型和垂直振动模型,计算了磨头的固有振动特性,为抑制水平和垂直振动的磨头结构优化设计和振动控制器的设计提供参考。     

堇青石基微晶玻璃的制备方法及性能控制

简要叙述了堇青石基微晶玻璃的主要制备方法。并以熔融法为主，对本系统微晶玻璃的性能控制工艺，如组成设计、热处理、退火工艺等进行了综述。     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的制备工艺研究

利用XRD、SEM等分析技术 ,研究了Na0 .5Bi0 .5TiO3 -K0 .5Bi0 .5TiO3 系无铅压电陶瓷的合成温度 ,烧成工艺条件对陶瓷晶体结构、压电性能的影响。结果表明 ,合成温度提高有利于主晶相的形成 ,适当延长保温时间有利于材料的压电性能。该体系随着KBT含量的增加 ,烧结温度提高 ,烧结温度范围变窄。同时研究了极化工艺条件对材料压电性能的影响表明 ,提高极化电场和适当提高极化温度有利于压电性能的提高 ,但过高的温度由于受到材料高温下退极化的影响而导致材料压电性能变差     

Tuning the interfacial reaction between CaO–SrO–Al2O3–B2O3–SiO2 sealing glass–ceramics and Cr-containing interconnect: Crystalline structure vs. glass structure

In this paper, Al₂O₃ was added to CaO–SrO–B₂O₃–SiO₂ sealing system to tailor the structure of sealing glass–ceramics and glass–ceramics/metal interfacial reaction. The addition of alumina in glasses contributes to increasing fraction of bridging oxygen in silica tetrahedral as well as the change in boron environment from three-fold to four-fold (BO₄ → BO₃). The devitrification tendency of glasses also decreases with increasing Al₂O₃ content. The condensed glass structure and increasing residual glass content play opposite roles on the interfacial reaction, consequently resulting in a maximum fraction of Cr⁶⁺ in reaction couples between Cr₂O₃ and glass containing 6 mole% Al₂O₃ at 700 °C. In addition, the good bonding can be observed at the interface between Cr-containing interconnect (Crofer 22APU) and glass containing 4 mole% Al₂O₃, held at 700 °C for 100 h. The reported results support the suitability of the prepared glass–ceramics as sealing materials for SOFC applications.     

氧化铝陶瓷料浆流变性的研究

主要研究了氧化铝料浆的流变性能,确定了分散剂的加入量与料浆浓度的关系,测得氧化铝浓料浆为剪厚型流体,通过对浓悬浮体流变性的研究得到其稳定分散的最佳pH范围是11～12.