自制纳米氧化铈对硅橡胶热老化性能的影响

研究了氧化铈对硅橡胶热老化性能的影响.结果表明,这种自制的纳米级氧化铈可有效提高甲基乙烯基硅橡胶的耐热空气老化性能,DTA-TG试验证明这种氧化铈的加入可明显提高硅橡胶的热反应温度,对颜色有要求的耐高温硅橡胶有实用价值.     

氢氧化铝对复合绝缘子用硅橡胶的性能影响研究

研究了氢氧化铝的粒径及填充量对复合绝缘子用热硫化硅橡胶的力学性能、电学性能、阻燃性、憎水性能的影响。实验结果表明：当氢氧化铝粒径为2.4μm时,硅橡胶的力学性能及阻燃性能达到最佳,憎水性及电学性能适中;氢氧化铝填充量为115～125份之间时,硅橡胶综合性能最佳,漏电起痕达到1A4.5,阻燃性能满足FV-0。     

CeO2 and CeO2:Pr nanocrystalline powders prepared by the polymeric precursor method: Yellow and red pigments with tunable color

The development of stable and reproducible inorganic pigments is noteworthy for industrial applications mainly considering more intense shades and low toxicity. Among the various candidates to substitute non-hazardous red and yellow pigments, CeO₂ and CeO₂:Pr have been attracting attention because of their opacity and high-temperature stability besides being environmental-friendly and health-friendly. In this study, nanostructured CeO₂ and CeO₂:Pr samples were synthesized using the polymeric precursor method and structural and optical characterizations were performed. Scanning electron microscopy reveals the morphology of CeO₂ nanoparticles in which the particle size ranges from 22 to 28 nm as a function of the annealing temperature. Pr-doping does not show influence on the particle size. XRD results show that CeO₂ and CeO₂:Pr samples crystallize in the cubic fluorite lattice with Fm3m space group. Raman spectra show the fluorite F_2g mode, confirming the XRD results. With Pr-doping and the annealing of the samples, two bands are observed between 550 and 600 cm⁻¹, which are related to the defects in the fluorite structure associated with oxygen vacancies. XPS spectra reveal an increase in the ratio of Ce³⁺ ions depending on the annealing temperature and Pr-doping. This increase is associated with the carbon removal from the lattice by annealing. This behavior causes a change in the hue of the powders as the annealing temperature increases. According to diffuse reflectance and colorimetric measurements, CeO₂ shows a light-yellow color due to the O 2p­Ce 4f transitions whose b* parameter mainly decreases with annealing, becoming almost white. The CeO₂:Pr sample exhibits a red-orange color because of the electronic transitions between 4f² → 5d¹ states of Pr³⁺. Upon annealing, L* and b* parameters decrease, resulting in a red-brown shade. The charge compensation or charge transfer is responsible for the modification of the hue of these pigments.     

纳米氧化铈催化作用研究探讨

总结了氧化铈在催化中的作用,指出了纳米粒子的表面效应及氧化铈自身特性对其催化性能的影响,分别从CeO2 作为催化剂、助剂、载体等方面对CeO2 在催化中的应用加以综述,介绍了制备纳米CeO2 超细粉体的常见方法,并结合有关研究结果提出了今后的研究方向。     

甲基乙烯基硅橡胶/凹凸棒土复合材料的紫外老化性能

以硅烷偶联剂KH 570改性凹凸棒土(AT),制备了甲基乙烯基硅橡胶(MVQ)/AT复合材料,考察了紫外辐射对MVQ/AT复合材料物理机械性能及热性能的影响,并通过扫描电子显微镜表征了复合材料的微观形貌。结果表明,随着辐照时间的延长,MVQ/AT复合材料的邵尔A硬度和拉伸强度先增大后减小,扯断伸长率先减小后增加,热稳定性先提高后下降;MVQ/AT复合材料经紫外辐照后,表面颜色加深并出现裂纹,随着辐照时间的延长,裂纹数量逐渐增加,表面变得粗糙,并且有部分填料暴露在材料表面。     

合成绝缘子组装用室温硫化硅橡胶

研究了一种用于合成绝缘子组装的单组分室温硫化硅橡胶（RTV-1）。重点考查107胶、增塑剂、填料及偶联剂对RTV-1的流平性及其粘接性能的影响。结果发现,该RTV-1粘接绝缘子材料效果优异,自流平性好,可用于合成绝缘子粘接组装。     

氧化铈对硅橡胶耐热性和耐油性的影响

研究了氧化铈用量对硅橡胶耐热性、耐油性的影响.结果表明,随氧化铈用量的增加,硅橡胶的力学性变化较小,但耐热性和高温下的耐油性明显提高;氧化铈的较佳用量为5份.通过热失重分析可知,与未加氧化铈的硅橡胶相比,加入10份氧化铈的硅橡胶在氮气环境下的热分解温度的峰值提高了13℃,在898.7℃时的固体残余质量分数提高11个百分点;在空气中第一阶段热分解温度的峰值提高了25.8℃,第二阶段提高了9.1℃,同时在898.7℃时的固体残余质量分数提高近3个百分点.说明加入氧化铈可提高硅橡胶的热稳定性.     

CeO2掺杂TiO2催化超声降解酸性大红的研究

选取酸性大红染料为降解目标物,研究了用实验室合成的氧化铈掺杂二氧化钛为催化剂存在下的超声反应。研究结果表明,CeO2掺杂TiO2催化超声降解酸性大红的效果优于非掺杂的锐钛矿型TiO2的情况。在溶液pH1.0～3.0、酸性大红质量浓度为20mg/L、溶液用量50mL、催化剂用量0.5～1.0g/L的条件下,用输出功率5.0W/cm2和频率25kHz的超声波照射80min,酸性大红降解率可达97.3%。     

溶液共混法笼状硅氧烷低聚物/硅橡胶复合材料的分散性

通过溶液共混法制备了笼状硅氧烷低聚物（POSS）／硅橡胶复合材料,用X射线衍射仪和透射电子显微镜研究了该材料的分散状况,考察了POSS质量分数以及烘干温度、溶剂含量对POSS在硅橡胶中分散状况的影响。结果表明,POSS质量分数越低,烘干温度越高,越有利于抑制POSS的结晶．进而有利于制备POSS精细分散的P0ss／硅橡胶复合材料;而溶剂含量越少时,更多的POSS以晶体形式从溶剂中析出,从而使得POSS的结晶程度更显著。     

溶胶-凝胶法制备氧化铝系复合膜的研究进展

介绍了采用溶胶-凝胶法制备Al2O3系复合膜的研究发展现状以及掺入不同外加组分后Al2O3膜的结构特点及其影响机理,同时指出了用溶胶-凝胶法制备氧化铝系复合膜过程存在的问题及发展趋势。     

自然老化对导电硅橡胶电阻特性的影响

分析了异电硅橡胶的电阻性特自然老化条件下的变化规律,发现自然老化对导电硅橡胶电阻行性的影响与导电粒子的质量分数有关,并确定了最佳的导电粒子质量分数。     

两种制备方法下锌铈复合纳米材料的性能比较

以四水硫酸高铈和七水硫酸锌为原料,碳酸铵为沉淀剂,分别采用直接沉淀法和异相沉淀法合成纳米氧化锌/二氧化铈复合材料。采用XRD,FT-IR和UV-Vis对产物进行表征分析。XRD分析表明,在相同的原料配比下,异相沉淀法合成的复合纳米材料中,铈的含量大于直接沉淀法合成的材料;FT-IR分析表明,异相沉淀法中,由于氧化锌对二氧化铈的表面包覆,样品分散性增加;UV-Vis分析表明,两种方法合成的样品都具有优异的紫外吸收性能,只是波段不同：异相沉淀法合成的产品的紫外吸收侧重于UVA波段,而直接沉淀法合成的产品的紫外吸收侧重于UVC波段。另外水中分散性实验还表明,采用异相沉淀法合成的纳米材料分散性优于前者。     

Characterization study of CeO2 supported Pd catalyst for low-temperature carbon monoxide oxidation

Catalysts consisting of palladium supported on cerium dioxide (Pd/CeO₂) were prepared and used for carbon monoxide oxidation in a stoichiometric mixture of carbon monoxide and oxygen. Pd/CeO₂ exhibits high catalytic activity for the oxidation of CO, showing markedly enhanced catalytic activities due to the combined effect of palladium and cerium dioxide. The Pd/CeO₂ catalyst is superior to Pd/ZrO₂, Pd/Al₂O₃, Pd/TiO₂, Pd/ZSM-5 and Pd/SiO₂ catalysts with regard to the activity under the conditions examined. The catalysts were characterized by means of XRD and TPR. The position of the H₂-TPR peak shifts to lower temperature with increasing Pd loading from 0.25 to 2.0%. CeO₂ inhibits the hydrogen reduction of PdO. CO-TPR measurements have shown the existence of three peaks. The low-temperature peak (α) is due to the Pd hydroxide species. The β peak has been attributed to finely dispersed PdO. The high-temperature peak (γ) has been attributed to crystal phase PdO. Crystal phase PdO is more difficult to reduce by CO than finely dispersed PdO. On the basis of the catalytic activity and CO-TPR results, we conclude α species (Pd hydroxide) mainly contribute to the catalytic activity for low-temperature CO oxidation. This revised version was published online in July 2006 with corrections to the Cover Date.     

硅烷偶联剂在粘土胶中的抗热氧老化作用

本文主要讨论了硅烷偶联剂的抗热氧老化作用通过采用天然橡胶塑性保护率的测定方法、橡胶热空气老化试验方法、扫描电子显微镜分析等,对硅烷偶联剂对粘土胶性能的影响进行了探讨,研究结果表明硅烷偶联剂不仅可以大大提高材料的强度,而且有明显的抗热氧老化效果。     

CeO_2含量对白云鄂博西尾矿为原料制备的微晶玻璃力学性能的影响

以白云鄂博西尾矿和粉煤灰为主要原料,采用熔铸法制备了高性能的CaO-MgO-Al2O3-SiO2(CAMS)系微晶玻璃。研究了不同晶化温度下CeO2含量对CAMS系微晶玻璃析晶行为、显微结构和力学性能的影响。结果表明:Ce4+离子可以置换辉石相主晶相中Ca2+形成置换固溶体;质量分数为0.6%的CeO2可以降低微晶玻璃的晶化温度、提高辉石相结晶度、促进其形成交错咬合的枝晶结构,从而提高微晶玻璃样品的抗折强度和显微硬度;过量的CeO2富集于辉石相晶间并进而形成Ca2Ce8(SiO4)6O2第二相晶间相,阻碍辉石相的形成和长大,从而使样品的力学性能有所降低。添加0.6%CeO2的微晶玻璃样品经870℃晶化2 h后,抗折强度和显微硬度分别达到234 MPa和6.982 GPa。     

自然老化对导电硅橡胶线性特性的影响

分别对未活加白炭黑和业加白炭黑增强的线性导电硅胶进行了５个月和１２个月的自然老化试验。结果表明,２种线笥导电硅橡胶的线笥特性是随自然老人时间的延长,其线性提高。     

镀镍石墨/硅橡胶导电复合材料的性能研究

以镀镍石墨为导电填料制备镀镍石墨/甲基乙烯基硅橡胶(MVQ)导电复合材料,并对其性能进行研究.结果表明,采用密炼工艺、硫化温度为110℃、偶联剂A-151和硫化剂双24用量分别为6和8份时,所制备的镀镍石墨/MVQ复合材料的导电性能和拉伸性能较好.     

聚砜改性环氧树脂复合材料热老化性能研究

以聚砜(PSF)改性环氧树脂(EP)为基体树脂,玻璃纤维为增强材料,采用高温模压成型法制备出PSF改性EP/玻璃纤维复合材料。结果表明:PSF能有效提高EP基体的热稳定性能;经200℃热老化72 h后,PSF改性EP/玻璃纤维复合材料的热失重率<1%,其冲击强度和弯曲强度呈先升后降态势,电绝缘性能仍然较好(其体积电阻率和表面电阻率的数量级仍保持在1012左右);该复合材料在高温绝缘场合中具有良好的应用前景。     

Thermal and mechanical properties of CeO2

The thermal and mechanical properties of cerium dioxide (CeO₂) were assessed using a range of experimental techniques. The oxygen potential of CeO₂ was measured by the thermogravimetric technique, and a numerical fit for the oxygen potential of CeO₂ is derived based on defect chemistry. Mechanical properties of CeO₂ were obtained using sound velocity measurement, resonant ultrasound spectroscopy and nanoindentation. The obtained mechanical properties of CeO₂ are then used to evaluate the Debye temperature and Grüneisen constant. The heat capacity and thermal conductivity of CeO₂ were also calculated using the Debye temperature and the Grüneisen constant. Finally, the thermal conductivity was calculated based upon laser flash analysis measurements performed on pellets fabricated using a range of feedstock purities to resolve discrepancies in the existing literature.     

高低温老化对碳纤维复合材料芯棒结构性能的影响

采用拉挤工艺制备了碳纤维增强环氧树脂基复合材料芯棒,并对其进行高低温人工加速老化试验,以及对老化前后碳纤维复合材料芯棒的横截面、外观颜色和密度进行了测试和分析。结果表明,高低温老化使芯棒颜色加深,主要对芯棒的外层产生一定的影响,内部结构没有明显变化;老化后芯棒的密度比老化前减小约2.5%,并且不同老化周期对芯棒的密度基本不变。