γ-Al_2O_3/聚酰亚胺纳米复合薄膜的制备与表征

采用水热工艺,以异丙醇铝为原料,制备出虫孔状形貌的γ-Al2O3溶胶,采用原位生成法合成了网状结构的γ-Al2O3/聚酰亚胺(polyimide,PI)纳米复合薄膜.用透射电镜、X射线衍射仪及Fourier红外光谱仪表征了溶胶的形貌及结构.用扫描电镜表征了复合薄膜的形貌.用耐电晕测试装置测试了复合薄膜的耐电晕时间.结果表明:所制备的溶胶呈虫孔状分子筛形貌,其结构中含有氢键;当掺杂质量(下同)高于12%时,复合薄膜中的无机相明显形成连续的网状结构;随着掺量的增加,复合薄膜的耐电晕时间增加,掺杂质量为25%的复合薄膜耐电晕时间是纯PI薄膜的25.4倍.分析了溶胶的形貌、结构对复合薄膜形貌及耐电晕性能的影响.     

聚酰亚胺/纳米Al_2O_3薄膜的制备及耐老化性能研究

为提高聚酰亚胺薄膜的击穿场强和耐电晕性能,分别采用气相纳米Al_2O_3颗粒、非气相纳米Al_2O_3颗粒制备了聚酰亚胺杂化薄膜。通过热激电流(TSC)、耐电晕性能、击穿场强等测试,分别评价了薄膜的陷阱能级、陷阱密度分布趋势、耐电晕性能和击穿场强,并用扫描电子显微镜对薄膜断面进行形貌分析。结果表明:纯聚酰亚胺、非气相纳米Al_2O_3杂化聚酰亚胺薄膜、气相纳米Al_2O_3杂化聚酰亚胺薄膜电荷陷阱密度依次上升,同时陷阱能级有降低的趋势;与纯聚酰亚胺薄膜相比,气相纳米Al_2O_3的掺杂使薄膜的击穿场强由170 k V/mm提高至241 k V/mm;与非气相Al_2O_3杂化的薄膜相比,气相纳米Al_2O_3的掺杂使薄膜的耐电晕时间由24.25 h提高至43.45 h,同时气相纳米颗粒更不容易发生团聚,提高了纳米颗粒的分散性。气相纳米Al_2O_3颗粒的掺杂使聚酰亚胺引入了更多的界面态及缺陷,使其陷阱密度提高,有效提升了聚酰亚胺薄膜的耐电晕性能及击穿场强。     

聚合物/勃姆石纳米复合材料研究进展

综述国内外聚合物/勃姆石纳米复合材料研究进展.在总结勃姆石溶胶的制备及表面改性方法的基础上,分析了聚合物/勃姆石纳米复合材料的制备方法与性能,并对其工业化应用研究进行了展望.     

溶胶—凝胶法制备超滤Al2O3膜的研究：I勃姆石溶胶的制备

本文通过用异丙醇铝水解的溶胶—凝胶法制备了勃姆石溶胶。对其制备过程的主要影响因素—胶溶剂种类及其用量、水解温度及加水量、老化温度及老化时间等进行了研究,探索出了制备稳定、清澈的勃姆石溶胶（ 也称为铝溶胶） 的最佳条件,并对勃姆石溶胶的性质进行了探讨。证实勃姆石胶粒带正电荷,发现勃姆石溶胶稳定存在的ｐＨ 值为３ ．５ ～４ ．１ 。配性太强,溶胶粘度过大易胶凝;酸性太弱,得不到完全胶溶稳定的溶胶。勃姆石溶胶和凝胶之间可以相互转化并没有明显界限     

凝胶聚合法制备氮化铝纳米粉体

近年来,微电子和半导体技术的飞速发展对器件材料的散热要求越来越高.因具有热导率高等优异性能,AlN引起了广泛关注.以三聚氰胺、甲醛、勃姆石溶胶为起始原料,利用同步的溶胶凝胶转换与高分子聚合过程,使有机高分子的交联网络与无机勃姆石的凝胶网络相互作用缠结,得到碳源(三聚氰胺和甲醛单体)和铝源(勃姆石溶胶粒子)均匀混合的前驱...     

硅铝纳米杂化聚酰亚胺薄膜的制备及性能分析

以聚酰胺酸(PAA)为基体,通过正硅酸乙酯(TEOS)和异丙醇铝的水解缩合反应制得硅氧铝溶胶;然后采用加热聚合法将硅氧铝溶胶和PAA聚合,制备出纳米杂化PI(聚酰亚胺)薄膜。着重探讨了无机纳米粒子中n(Al)∶n(Si)比例对不同纳米杂化PI薄膜的结构、微观形貌、热稳定性、电击穿性能和耐电晕性能等影响。研究结果表明:当w(总纳米粒子)=12%(相对于PI质量而言)、n(Al)∶n(Si)=1∶4时,纳米杂化PI薄膜的综合性能相对较好,此时其热稳定性和电绝缘性能优异。     

无机纳米聚酰亚胺复合膜的结构与性能

聚酰亚胺(PI)作为一种功能材料,已广泛用于航空航天和微电子领域。然而聚酰亚胺的耐电晕性差限制其在高温和精密状态下的应用。有机-无机纳米复合和超声辐射可提高材料的耐电晕性。笔者利用超声辐射制备无机纳米二氧化硅/聚酰亚胺复合膜。升温8h,温度至573.15K,得到平均厚度为20~30靘的膜。通过高压实验仪器检测聚酰亚胺复合膜的耐电晕性;通过红外光谱测定聚酰胺酸(PAA)转化为聚酰亚胺的亚胺化程度;通过原子力显微镜表征纳米微粒的特征,包括微粒尺寸、分布、形状和分散性。实验表明,比普通的搅拌方式,超声辐射可使聚酰亚胺膜中的纳米微粒得到更有效的分散,经过纳米二氧化硅杂化的聚酰亚胺复合膜比普通聚酰亚胺膜具有更高的耐电晕性。     

利用原子力显微镜研究聚酰亚胺／纳米SiO2复合材料

通过均苯四甲酸二酐与4，4’-二氨基二苯基醚缩聚反应制备了聚酰胺酸（PAA）。采用溶胶-凝胶法和超声波机械共混法制备了不同纳米SiO2含量的PAA／纳米SiO2共混胶液，经高温亚胺化得到聚酰亚胺（PI）／纳米SiO2复合材料。利用原子力显微镜（AFM）对PI／纳米SiO2复合材料与杜邦公司的KAPTON耐电晕复合材料及其电晕试验后的复合材料进行了表面形貌、结构和性能比较。结果表明，溶胶-凝胶法和超声波机械共混法制备的PI薄膜中的无机相是无定形的，而KAPTON薄膜中的无机相是缨束状的，具有取向的微观结构。超声波机械共混法具有很好的分散作用，而其有机相与无机相之间结合力较溶胶-凝胶法弱。     

片状纳米勃姆石对水泥力学及微观性能的影响

掺加纳米颗粒会影响到材料的力学性能,本文采用水热法在碱性环境下合成了片状纳米勃姆石,并将其加入到水泥中,研究了片状纳米勃姆石对水泥浆体力学性能的影响规律,并结合水化热、X射线衍射分析、热分析、氮吸附分析、扫描电子显微镜分析等测试手段对片状纳米勃姆石在水泥中的作用机理进行研究。结果表明:片状纳米勃姆石的加入可以明显提高水泥浆体的早期力学性能,与空白组相比,当勃姆石掺量为0.5%(质量分数)时,水泥浆体的抗压强度最大可以提高42.8%;勃姆石的加入不仅可以提高水泥水化反应速率,促进水泥的早期水化,还可以减少有害毛细孔含量,优化孔结构,提高水泥浆体的致密程度,从而促进水泥早期强度的发展。该研究结果为改善水泥的力学性能提供了新的方法。     

以无机盐为前驱体制备超滤膜的研究

以无机盐Al(NO3)和氨水为原料，采用sol-gel法制备出稳定透明的勃姆石溶胶，采用浸渍法工艺将勃姆石溶胶均匀地涂覆在Al2O3载体上，通过对膜与载体的复合工艺条件的研究，制备出孔径均匀的无缺陷的Al2O3超滤膜。     

Processing and Properties of Sol–Gel-Derived Alumina/Silicon Carbide Nanocomposites

Dense alumina/5 vol% SiC nanocomposites were prepared by sol–gel processing using nanosized (180 nm) precoated SiC powders and a commercial boehmite sol. The SiC powder was precoated with boehmite by a controlled heterogeneous precipitation from an aluminum nitrate solution. The coated SiC powder was then dispersed in a boehmite sol, gelled, calcined, and densified by gas pressure sintering under argon atmosphere at 7–8 MPa pressure. The dependence of the calcination conditions on densification, the effect of seeding on the microstructural development, as well as the mechanical behavior of the sintered specimens, are presented and discussed.     

支撑体生坯浸涂溶胶（一步法）制备不对称结构陶瓷超滤膜的研究

无机陶瓷膜的低成本化日益受到重视。在此以降低陶瓷膜制备成本为出发点,采用在支撑体生坯上浸涂勃姆石溶胶,经干燥烧结后制备具有不对称结构的无机陶瓷超滤膜。考察了更具成本优势的常温水解氯化铝制勃姆石溶胶和传统异丙醇铝制勃姆石溶胶两种溶胶在涂膜时缺陷控制的方法。溶胶中添加PVA可以有效降低溶胶涂层缺陷。在支撑体生坯上浸涂勃姆石溶胶,支撑体与涂层一次烧结制备的不对称结构的陶瓷膜孔隙率与未涂膜支撑体相同,对PVA1750的截留率为90.7%。相对于传统烧成支撑体涂膜的多次烧结工艺,表现出了更低成本优势。     

Effect of boehmite sol on the performance of alumina microfiltration membranes

Precursor film method was used to prepare highly permeable ceramic microfiltration membranes in this work. The performance of alumina microfiltration membranes was improved by adding boehmite sol in the membrane precursor film. With increasing the boehmite sol content, the effective average pore size of the membrane was continuously decreased and the separation efficiency of the membrane was increased. These improvements were due to that the boehmite sol not only helped the dispersion of the α-Al₂O₃ powder in the membrane forming slurry, but also formed γ-Al₂O₃ in the gaps among the existed α-Al₂O₃ particles which was beneficial for membrane sintering and pore size decreasing. For the membrane prepared with 45 wt% boehmite sol, the effective average filtration pore diameter was 178 nm and the water permeance of the membrane reached 1691 Lm⁻²h⁻¹bar⁻¹, which was much better than the values reported before. Moreover, the reusability of the membrane was confirmed using a recycling test.     

涂覆液种类对FeCrAl金属载体上氧化铝涂层性质的影响

利用浸渍提拉法（dip-coating）,分别采用铝溶胶与氧化铝浆液在FeCrAl金属载体上制备了两种γ-Al₂O₃活性涂层,考察了涂覆液种类对涂层性质的影响。利用扫描电镜、X射线衍射、氮气物理吸附和超声波振动方法考察了两种涂层的表观形貌、晶型结构、织构性质及涂层与金属载体之间的结合力。研究结果表明,当涂层负载量小于3%（质量分数,下同）时,溶胶涂层可以避免开裂,而浆液涂层无法避免开裂发生;当负载量大于8%时,溶胶涂层在干燥后会开裂翘起甚至直接脱落,而浆液涂层虽然开裂加剧但是不会直接脱落。对于涂层厚度需求较低的体系（涂层负载量小于8%）,溶胶涂层的比表面积和孔容比浆液涂层更大,更适合作为催化剂活性载体;而对于涂层厚度需求较高的体系（涂层负载量大于8%）,则应选择浆液涂层。     

Boehmite coating on θ-Al2O3 particles via a sol–gel route

θ-Al₂O₃ powders in slurry form were coated by boehmite nanoparticles prepared from alumina sol that consists of aluminum tri-sec-butoxide (Al(OC₄H₉)₃) as a precursor. The θ-Al₂O₃ powders presented an iso-electrical point (IEP) at pH ∼ 9.2, and formed stable suspensions without notable gravity settling at acidic conditions (pH 3–4). Boehmite nanoparticles with a mean particle size ca. 68 nm were derived from the hydrolysis of Al(OC₄H₉)₃ sol. Well-dispersed boehmite/θ-Al₂O₃ aqueous mixtures consisting of 3 and 9 wt.% of boehmite were then prepared by addition of θ-Al₂O₃ powder into the Al(OC₄H₉)₃ sol followed then by vigorous agitation at 90 °C and in a pH range 3–4. IR and particle-size measurement both revealed possible coating of boehmite on the θ-Al₂O₃ particles. From TEM observation, “thickness” of the boehmite layer did not vary much with the boehmite concentration. Agglomeration of the particles became nonetheless apparent as the boehmite concentration was increased. The boehmite coating on θ-Al₂O₃ surface inhibited grain growth during the θ- to α-phase transformation upon heating. Mean grain size of the boehmite-coated alumina was substantially smaller than that of the un-coated one.     

快速升温法制备陶瓷超滤膜的研究

无机陶瓷膜的低成本化日益受到重视。以降低陶瓷膜制备成本为出发点，采用在支撑体生坯上浸涂勃姆石溶胶，经干燥快速烧结后制备了具有不对称结构的无机陶瓷超滤膜。考察了更具成本优势的常温水解氯化铝制勃姆石溶胶和传统异丙醇铝制勃姆石溶胶两种溶胶在涂膜时缺陷控制的方法。溶胶中添加PVA可以有效降低溶胶涂层缺陷。在支撑体生坯上浸涂勃姆石溶胶，支撵体与涂层一次烧结制备的不对称结构的陶瓷膜孔隙率与未涂膜支撑体相同，对PVA1750的截留率为90．7％。相对于传统烧成支撑体涂膜的多次烧结工艺，烧结成本下降75％，表现出了更低成本优势。     

Mullite Whiskers from Precursor Gel Powders

A mullite precursor sol was prepared by mixing boehmite and silica sols. On addition of 3.5 wt% F⁻ ion as a 47% solution of HF, the mullite sol was gelled. The dried gel was ball-milled and calcined at 1400°C for 1 h in an airtight container. Mullite whiskers grew on the (111) plane along the 〈001〉 direction.     

Sol–Gel Synthesis and Characterization of Alumina–Calcium Hexaaluminate Composites

Boehmite sol was prepared by hot water hydrolysis of aluminum iso-propoxide using nitric acid as the catalyst. Calcium nitrate to yield 0–20 vol% calcia was added to the boehmite sol. The boehmite with additives was calcined at 600°C for 3 h. The calcined powder was milled at 230 rpm for 6 h and particle size was measured using Laser particle size analyzer. The powder samples were calcined at 1600°C for 3 h and the formation of calcium hexaaluminate was discussed using phase diagram, transmission electron microscope, energy dispersive spectra, and X-ray diffraction spectra. The powder samples calcined at 600°C for 3 h were compacted into cylindrical pellets and sintered at temperatures ranging from 1400° to 1600°C for 6 h and the formation of hexaaluminate (platelike) grains were confirmed using Scanning electron microscope and optical microscopy.     

湿化学法制备纳米铝化合物的研究进展

介绍几种制备AlOOH、Al2O3和Al13等几种纳米铝化合物的方法进展,主要介绍了湿化学法中的水热法、溶胶-凝胶法、沉淀法、电化学法等方法,并对这几种方法的优缺点进行了比较。     

Influence of Peptization and Ethanol Washing on the Pore-Structure Evolution of Sol-Gel-Derived Alumina Catalyst Supports

Alkoxide-derived boehmite precipitates were subjected to different post-precipitation treatments to obtain a peptized sol, an unpeptized slurry, and an ethanol-washed gel precipitate. These materials were dried further to obtain the corresponding gels. Changes in the surface area, porosity, and pore size with temperature and the phase-transformation behavior from gamma-alumina to alpha-alumina were studied using X-ray diffractometry, differential scanning calorimetry, and physical adsorption/desorption measurements. Gels that were obtained from the peptized sol retained the lowest porosity, in comparison to the ethanol-washed gel and the gel that was prepared from the aqueous slurry.