钛合金熔模精密铸造用氮化硼基复合型壳的探索试验

研究了六方氮化硼作为钛合金熔模精密铸造中面层造型材料的可行性.以高温高压下预处理的氮化硼作为型壳面层中的主要耐火材料,钇溶胶作为黏结剂并适当加入少量氧化钇,制备氮化硼基复合型壳.研究了氮化硼涂料的密度、黏度等性质,通过热重分析探讨了氮化硼基复合型壳的烧结工艺.研究表明:面层涂料具有剪切稀释性,涂料的表观黏度随剪切速率的升高而降低.当型壳焙烧温度高于800℃时应采用N2保护加热.TiNi合金与型壳的反应较小,在TiNi合金铸件中没有出现夹杂氧化钇颗粒.     

氟硼酸铅镀液中电沉积钛基二氧化铅

以电沉积法从氟硼酸铅镀液中制备Ti基PbO2阳极(FB/PbO2)及其掺杂氟离子的FB/F - PbO2阳极.应用计时电位法研究了所制备阳极的电沉积成核速率,发现氟硼酸铅镀液在钛基表面电沉积二氧化铅的结晶速度比硝酸铅镀液更快.采用XRD和SEM技术对这两种电极进行了表征,并与传统的硝酸镀液制备的钛基二氧化铅对比,发现电...     

中国专利

一种具有核壳结构导热填料填充的聚丙烯复合材料本发明公开了一种具有核壳结构导热填料填充的聚丙烯复合材料。该聚丙烯复合材料中核壳结构导热填料的含量为35%~40%(w),导热系数为0.48~0.56 W/(m·K)。本发明将两种导热填料——氨基改性氮化硼和环氧基改性三氧化二铝通过化学键连接在一起,形成核壳结构的导热填料;导热系数较大的片状氨基改性氮化硼由于包覆在体积较大的球形环氧基改性三氧化二铝的表面,也更容易让具有较高导热系数的导热填料相互接触,从而形成导热网络,使核壳结构导热填料的导热系数提升0.1~0.2 W/(m·K)。该聚丙烯复合材料的制备中还添加了DMP?30型催化剂,有效地降低了化学反应的活化能,增加了核壳结构导热填料的数量,并且易于制备。     

电泳粒子的研究进展及其在电子纸中的应用

电泳粒子在电泳显示型电子纸中是一种重要的显示元素。综述了颜料型、核壳复合型、胶囊型和聚合物型电泳粒子研究现状,并介绍了电泳粒子在微胶囊电泳显示和微杯电泳显示2种类型电子纸中的应用。     

铱钛氧化物中间层对钛基氧化铱电极组织及析氧行为的影响

以纳米TiN粉体和氯铱酸的混合液为涂液,采用浸渍一热分解法制备了含IrOx-TiO2中间层的钛基氧化铱电极.研究了IrOx-TiO2中间层对钛基氧化铱电极的显微结构及析氧寿命的影响.结果表明,TiN作为前驱体氧化生成金红石相的二氧化钛与氧化铱形成固溶体,并与钛基体形成了共格界面,从而构成了铱钛复合氧化物中间层,中间层的加入没有改变传统钛基氧化铱电极的基本形貌特征和组成,因而具有相同的电催化响应特性;由于中间层中二氧化钛的固溶和与钛基体的共格结合起到机械和化学的双重作用,电极的析氧寿命明显延长,从而通过实验手段证明了氧化铱电极失效的主要机制是由于钛基界面的劣化引起的.     

加成型导热电子灌封胶的研制

以端乙烯基硅油为基胶、含氢硅油为交联剂、α-Al2O3和氮化硼(BN)为导热填料制得加成型导热灌封胶。研究了导热填料的种类、用量和配比对灌封胶导热性能的影响。结果表明:α-Al2O3的导热系数最大;随着BN用量的增加,灌封胶的导热系数和拉伸强度提高,断裂伸长率先增后降,但粘度上升明显。不同粒径的α-Al2O3和氮化硼(BN)并用可以提高灌封胶的导热系数,且对粘度和力学性能影响较小。     

高钛型高炉渣耐热混凝土试验研究

利用高钛型高炉渣作为混凝土的粗、细骨料配置C30耐热500℃混凝土.测试了等量粉煤灰取代水泥、改变水泥用量对混凝土耐热性能的影响.结果表明,高钛型高炉渣耐热混凝土的强度等级、烘干强度大于强度设计等级,混凝土试体煅烧500℃后的相对抗压强度为67.3％～83.4％,线变化率在±1.5％内,且表面无裂纹,满足耐热要求,说明利用高钛型高炉渣作为粗、细骨料配制耐热500℃混凝土是可行的.适量粉煤灰取代水泥,不但能降低水泥的用量,而且还能提高混凝土的耐热性能.     

高活性晶种制造金红石型颜料钛白粉

在严格掌握制备条件的情况下,用稀氨水中和工业硫醇钛溶液,制成高活性氨中和晶种。这种晶种不仅对钛液的水解阶段有活性,而且对TiO_2水合物的煅烧阶段有活性,具有将锐钛型晶体转化为金红石型晶体的金红石化特性。将此晶种加入钛液,实现了高浓度钛液的常压水解,再经恰当配方的盐处理,煅烧相变,研磨分级,包膜处理等工     

轻质刚性隔热材料的制备及性能研究

以短切石英纤维和莫来石纤维为骨架,氮化硼粉和硅溶胶为粘结剂,采用水基料浆制备了具有鸟巢结构的刚性隔热材料,研究了纤维配比及氮化硼含量对刚性隔热材料密度、显微结构、热导率及压缩强度的影响.结果 表明,通过调整氮化硼含量,材料密度在0.21 ～0.34g/cm3变化,随氮化硼含量增加,三组隔热材料的密度和压缩强度逐渐提高,隔热性能有轻微降低,当氮化硼加入量为8wt％时,材料300℃和700℃的热导率分别为0.055 W· m-1·K-1和0.078 W-m-1·K-1,压缩强度可达2.73 MPa,相比较2wt％含量样品的压缩强度(1.44 MPa)提高了90％.     

增韧导热环氧树脂/氮化硼复合材料的制备与表征

采用种子乳液聚合方法制备了聚（丙烯酸正丁酯/甲基丙烯酸甲酯-co-甲基丙烯酸缩水甘油酯）核壳增韧剂（PBMG）,并用湿法球磨与超声辅助相结合的方法对六方氮化硼（h-BN）进行改性,制备的改性氮化硼（MBN）可提高环氧树脂（EP）的热导率。最后采用机械共混方法制备了环氧树脂/增韧剂/改性氮化硼（EP/PBMG/MBN）复合材料。通过透射电子显微镜（TEM）、扫描电子显微镜（SEM）、X射线衍射（XRD）、动态激光光散射（DLS）、热导率和力学性能等测试对核壳增韧剂的粒子形成、改性氮化硼和复合材料进行了表征。结果发现：最终制备的聚丙烯酸酯乳胶粒子呈现明显的核壳结构,且粒度分布很窄。当聚丙烯酸酯增韧剂添加量为5%、改性氮化硼为8.99%时,环氧树脂/增韧剂/改性氮化硼复合材料的冲击强度和热导率比纯环氧树脂（EP）的分别提高了133%和171%。随着未来的基板材料要求有效的热耗散,这种复合材料有望用于微电子工业上。     

Effect of a Boron Nitride Interphase That Debonds between the Interphase and the Matrix in SiC/SiC Composites

Typically, the debonding and sliding interface enabling fiber pullout for SiC-fiber-reinforced SiC-matrix composites with BN-based interphases occurs between the fiber and the interphase. Recently, composites have been fabricated where interface debonding and sliding occur between the BN interphase and the matrix. This results in two major improvements in mechanical properties. First, significantly higher failure strains were attained due to the lower interfacial shear strength with no loss in ultimate strength properties of the composites. Second, significantly longer stress-rupture times at higher stresses were observed in air at 815°3C. In addition, no loss in mechanical properties was observed for composites that did not possess a thin carbon layer between the fiber and the interphase when subjected to burner-rig exposure. Two primary factors were hypothesized for the occurrence of debonding and sliding between the BN interphase and the SiC matrix: a weaker interface at the BN/matrix interface than the fiber/BN interface and a residual tensile/shear stress-state at the BN/matrix interface of melt-infiltrated composites. Also, the occurrence of outside debonding was believed to occur during composite fabrication, i.e., on cooldown after molten silicon infiltration.     

SiC复相陶瓷内加热器套管的制备及性能

用SiC粉作内加热器套管基本原料,采用反应烧结及常压烧结工艺制备具有复层结构的SiC复相陶瓷套管。套管内层为高致密SiC/Si复合材料,外层为SiC/C/SiC复相陶瓷。通过实验模拟内加热器服役环境,将套管内置热源在750℃熔融铝液中加热360 h测试其使用性能,研究外部复杂熔液腐蚀环境及内部强氧化气氛对SiC复相陶瓷套管的密度、抗弯强度、物相组成及显微形貌的影响。结果表明：复层结构SiC套管在模拟实验中展现出良好的抗热震及抗熔液浸蚀能力;内层材料由于高致密性具有良好的抗氧化性能;外层材料浸入熔体部分强度损伤小于10%,液面以上部分残余强度达到48MPa。SiC复相陶瓷套管在有色金属熔炼行业展现出良好的应用前景。     

Protective coatings for carbon bonded carbon fibre composites

Carbon bonded carbon fibre composites (CBCF) were modified by direct reaction with molten silicon in order to obtain a silicon carbide layer on the composite surface. Subsequently, the Si-infiltrated CBCF material was coated with a silica-based glass containing yttria and alumina by means of a slurry-dipping technique. On heat treatment the glass yielded a glass-ceramic layer thus giving a multi-layered oxidation and erosion protection system. The microstructural characterisation of the coating was conducted by standard microscopy techniques and by X-ray diffraction. The controlled crystallization of the glass-produced cristobalite, yttrium silicate (Y₂Si₂O₇, keiviite, β-form) and mullite as main crystalline phases. These are excellent ceramic materials for oxidation and erosion protection of SiC-coated carbon-based composites since their coefficients of thermal expansion (CTE) closely match that of SiC. The possibility of healing (closure) of micro cracks by a thermal treatment at 1375 °C, thus exploiting the viscous flow of the residual glass in the glass-ceramic, was explored in order to extend the service life of the protection system.     

Interfacial microstructure and strengthening mechanism of BN-doped metal brazed Ti/SiO2-BN joints

Ag–Cu–Ti + BN composite filler was developed to braze SiO₂-BN ceramic and titanium. The effects of BN particles content on the microstructure and mechanical properties of the joints were investigated. The fine TiB whiskers and TiN particles were synthesized in the brazing seam by introducing BN particles. TiN–TiB₂ reaction layer formed adjacent to SiO₂-BN ceramic while Ti–Cu compound layer formed at Ti substrate. With the increase of BN content, more fine-grains formed in the joint and the reaction layer nearby the base materials became thinner. The hardness and modulus of the reaction phases were characterized by nanoindentations to reveal the plastic deformability of the brazing seam. The improvement of the joint strength was 340% with 3 wt.% BN addition. The joint strength was determined by the thermal expansion mismatch between the joined materials, plastic deformation in the brazing seam, and interfacial structure of the joint.     

Thermal shock resistance of the porous boron nitride/silicon oxynitride ceramic composites

The thermal shock resistance of the porous boron nitride/silicon oxynitride (BN/Si₂N₂O) ceramic composites were tested by the quenching‐strength method with temperature differences of 600‐1400°C. The residual flexural strength of the composites decreased with increasing temperature difference from 600°C to 900°C. This weakening in flexural strength was attributed to the formation of microcracks in the matrix caused by thermal stress damage. Afterward, as the formation of a dense oxidized layer sealed the surface and hindered further oxidation, the residual flexural strength increased with the further increase of temperature difference from 900°C to 1100°C. Finally, when the temperature differences were above 1100°C, the residual flexural strength gradually decreased with increasing temperature difference, which was attributed to the further oxidation and large thermal stress damage. And the thermal shock resistance of the porous BN/Si₂N₂O ceramic can be improved by the introduction of high contents of sintering aids and h‐BN.     

Mechanical and kinetic studies on the refractory fused silica of integrally cored ceramic mold fabricated by additive manufacturing

A refractory fused silica based integrally cored ceramic mold, the ceramic core with a ceramic mold shell in a single patternless construction, is fabricated by ceramic stereolithography of additive manufacturing. Refractory ceramic molds should satisfy the following restrictions such as similar strength to that of cast metal during solidification, thermal stability for dimensional accuracy, and easy removal of core after casting. Here, we report mechanical and transformation kinetic studies on the refractory fused silica of integrally cored ceramic mold. The flexural strength of sintered silica continually increases with higher density of better densification up to 11.4 MPa at 1300 °C, while it decreases from 11.3 MPa at 1350 °C to 4.6 MPa at 1500 °C. The degradation of the flexural strength is related to the larger amount of the cristobalite and microcracks generated by the abrupt contraction induced during the transformation of beta to alpha cristobalite. Given the quantitative x-ray diffraction study on transformation kinetics, an apparent activation energy Q is 674 ± 53 kJ/mol and the average time exponent 1.85, suggesting that the transformation kinetic is controlled by 1-dimensional interfacial growth.     

Ceramic Bodies with Complex Geometries and Ceramic Shells by Freeze Casting Using Ice as Mold Material

Ceramic bodies with a complex shape and closed ceramic shells encapsulating other components like steel parts were fabricated by the freeze-casting technique using ice as a mold and as core material. The ice molds and cores were simultaneously removed with the frozen suspension liquid of the ceramic slip by subsequent freeze drying. In this way, cores can be eliminated from a closed shell by sublimation through the porosity of the shell. Moreover, the ice cores allowed to transfect other components into porous ceramic bodies. Complex dental parts such as steel rods encapsulated in porous zirconia shells achieved by this ice mold freeze casting are represented in this article.     

Functional coatings for titanium casting molds using the replica technique

The quality of titanium cast parts depends not only on the corrosion reaction of the mold in contact with the titanium alloy melt, but also on the dimensional accuracy and the surface quality of the investment casting mold. Usually, the ceramic mold is produced by dip-coating. This contribution investigated the coating properties of green calcium zirconate (CaZrO₃) coatings produced by the replica technique. Thus, the effect of different coating slurries as well as different coating technologies on important coating properties was analyzed. In all cases, centrifuging and spraying produced thinner coatings compared to dip-coating. Using an appropriate coating slip, particularly centrifuging revealed a cohesive homogeneous coating surface and is therefore a promising technology for the production of functional coatings for titanium casting molds.     

Wetting behavior and interfacial interactions of molten Cu50Ti alloy with hexagonal BN and TiB2 ceramics

Wetting behavior of molten Cu50Ti alloy on hexagonal BN (h-BN) and TiB₂ ceramics has been studied under vacuum using a modified sessile drop method. Final contact angles of 8° and 3° are obtained at 1000 °C on h-BN and TiB₂, respectively. Interaction occurs at the interface between the molten alloy and BN, leading to the formation of a reaction layer containing TiB and Ti nitrides. Interfacial interaction of Cu50Ti with TiB₂ results in the formation of densely packed TiB layer about 60–100 μm thick and the detachment of TiB₂ grains. Spreading wetting of liquid Cu50Ti on h-BN is mainly controlled by the reactions between Ti and BN at the triple line. For Cu50Ti/TiB₂ system, spreading is mainly limited by the interfacial reaction in the first stage, and is possibly influenced by both the diffusion of boron atoms and viscous friction of the liquid in the second stage. Finally, brazing of graphite to CuCrZr alloy has been realized using Cu50TiH₂ with ceramic additives (including BN and TiB₂) as composite fillers. The joints exhibit favorable interfacial bonding between the filler layer and the substrates. The ceramic reinforcements in the filler layer could contribute to the improvement of the shear strength.     

Preparation of interpenetrating alumina–copper composites

To prepare interpenetrating alumina–copper composites, alumina foams were activated with titanium coating by chemical vapor deposition and then were infiltrated with molten copper by expendable casting process. The microstructure and phase composition of the composites were analyzed, and bending strength, electrical conductivity, friction and wear properties were tested. The results showed that the bonding between ceramic and metal was fine in the composites while no reactions took place between them because of the undissolved titanium coating. With increase of ceramic fraction, the electrical conductivity of the composite decreased, whereas the bending strength increased. The composite failure occurred by ductile fracture of the metal followed by fracture of the ceramic. The wear rate of the composites decreased with increase of ceramic fraction. And the wear of the composites was featured with ceramic struts peeling compared with ploughing and adhering wear for pure copper.