磷酸盐结合法制备Al2O3多孔陶瓷及性能

以煅烧α-Al2O3粉为骨料、磷酸二氢铝为高温烧成粘结剂、石蜡为成型助剂,通过模压成型、干燥、烧结等工序制备了氧化铝多孔陶瓷,研究了烧成温度和磷酸二氢铝含量对氧化铝多孔陶瓷微观形貌、物相组成、线收缩率、孔隙率和弯曲强度的影响,探讨了磷酸盐结合法烧结机理.结果表明:氧化铝多孔陶瓷物相由α-Al2 O3和AlPO4构成,在较低温度下,氧化铝颗粒仅依靠AlPO4的粘结作用而形成多孔陶瓷,氧化铝多孔陶瓷线收缩率和弯曲强度随磷酸二氢铝含量的增加而缓慢增大,孔隙率则缓慢降低;随着烧结温度的提高,AlPO4的存在促进了氧化铝颗粒间的液相烧结,线收缩率和弯曲强度随烧结温度的升高而显著增大,孔隙率也明显降低.     

Er3+离子在多孔模板内的发光特性

利用两次阳极氧化的方法制备多孔氧化铝模板,然后采用溶胶-凝胶法将铒的乙酰丙酮配合物掺人多孔氧化铝的模板内,制得了Er3 离子的SiO2凝胶。用扫描电镜(SEM)观察了多孔氧化铝模板的形貌,并测试了乙酰丙酮合铒的红外吸收谱以及Er3 离子在多孔模板内的室温荧光谱。初步结果显示纳米孔洞导致了荧光峰变窄。     

陶瓷微珠直接堆烧制备多孔莫来石陶瓷及性能研究

以高纯石英粉、氧化铝粉以及玻璃粉作为主要原料,首先通过颗粒稳定泡沫法结合离心雾化干燥装置制备得到SiO2-Al2O3陶瓷微珠,然后将其紧密堆积于坩埚中,随后经1500 ℃下直接堆积烧结1 h,利用空心微珠高温下自发泡,成功制备孔分布均匀的多孔莫来石陶瓷.研究了SiO2-Al2O3陶瓷微珠中高纯石英粉、氧化铝粉和玻璃粉组成对多孔莫来石陶瓷性能的影响.该方法简便易行,可控性强.通过该方法可制得气孔率高达85.4;,抗压强度为(3.69±0.86) MPa,低介电常数为1.70的多孔莫来石陶瓷,有望应用于透波材料领域.     

硅树脂对多孔氧化铝基陶瓷的制备及强化效应的影响

以氧化铝粉为基体,热固性硅树脂为粘结剂,利用热压注方法制备出多孔氧化铝基陶瓷试样,接着又用液态硅树脂对该试样进行强化处理.结果表明:以硅树脂为粘结剂,制备的氧化铝基陶瓷在1500℃烧结后,具有46.99;的显气孔率,22.15 MPa的抗弯强度,0.23;的收缩率,但其1600℃高温抗弯强度仅为2.04 MPa.在液态硅树脂强化后,其室温强度达到了37.67 MPa,高温强度也相继增加,在1600℃下,其强度增加到10.18 MPa.     

多孔氧化铝模板电沉积法制备ZnO纳米结构阵列的研究

利用直流电化学沉积技术,在多孔氧化铝模板内,通过先沉积Zn(OH)2/ZnCO3,然后在300℃下进行热分解,制得了ZnO纳米点阵结构.扫描电镜结果表明多孔氧化铝模板孔道呈六角形分布,孔径约为55 nm,孔间距约为100 nm,且孔道上下贯通平行排列.X射线衍射表明多孔氧化铝模板为非晶结构,孔内组装的ZnO具有多晶纤锌矿结构.光致发光谱表明ZnO/PAM复合体系同空氧化铝模板相比在420 nm处具有较强的蓝光发射.     

同轴静电纺丝制备仿生多孔氧化铝纤维研究

以无水氯化铝为原料,聚乙烯吡咯烷酮(PVP)为助纺剂,无水乙醇为溶剂,采用同轴静电纺丝法制备出氧化铝凝胶/PVP前驱体纤维,经1200℃煅烧后得到仿生多孔氧化铝纤维.系统研究了内外液流速以及PVP用量对多孔氧化铝纤维物相和孔结构的影响.结果表明,适当加大内液流速纤维逐渐出现仿生多孔结构,内液流速过大则会导致纤维多孔结构破裂消失.随着外液流速增加,纤维中的孔结构数量和孔径逐渐减小.增加PVP用量纤维直径增大,孔结构数量及孔径也会减小.当内液流速为0.1 mL/h,外液流速为1.0 mL/h,PVP用量为0.5g时,纤维为高纯α-Al203相,纤维表面光滑、连续,具有明显的仿生多孔结构.     

La2O3对氧化铝/高岭土复合定向多孔陶瓷性能的影响

以微米级α-Al2O3、陶瓷水体分散剂为主要原料,以La2O3-水洗高岭土为烧结助剂,采用冰模板法制备了一种具有高孔隙率和较高抗压强度的氧化铝/高岭土复合定向多孔陶瓷.研究了不同添加量的La2O3对多孔陶瓷的显气孔率、体积密度、抗压强度和微观形貌的影响.结果表明:添加适量的稀土La2O3能降低多孔陶瓷烧结温度、提高体积密度和抗压强度.通过高能机械球磨法添加La2O3,在1350℃烧结制备的多孔材料样品显气孔率为82;,样品的抗压强度达到10 MPa以上.当La2O3加入量达到3;时,可使多孔陶瓷抗压强度提高到15.2 MPa,较不掺加La2O3提高了约53;.     

用热CVD法制备片状碳纳米材料的研究

采用阳极氧化法在草酸溶液中制备了孔径约为100nm的多孔氧化铝(AAO)模板。利用此模板在不负载任何催化剂的条件下,利用热CVD装置制备出片状碳纳米薄膜,并对此片状薄膜做了SEM,TEM显微观察和EDS能谱分析,对其形成条件和生长机理等方面做了探讨分析,为在氧化铝模板上生长包括管状、片状、棒状等形状的碳纳米材料提供了一定的借鉴意义。     

冷冻干燥技术制备多孔陶瓷的现状与展望

冷冻干燥技术是一种很有特色的制取多孔材料的新技术,尤其是该技术所制备的多孔陶瓷所呈现出独特的微观结构和优良的生物性能,引起了各国学者广泛关注,成为当前多孔陶瓷材料制备的一个研究热点.本篇论文将简述冷冻干燥技术的原理,并分析冷冻媒介对冷冻干燥技术制备多孔陶瓷形貌及性能的影响,为冷冻干燥技术制备多孔陶瓷材料提供理论参考.     

助熔剂法合成α-Al2O3片晶及其多孔陶瓷的制备及表征

实验首先以γ-AlOOH粉体为原料,KCl-Na2SO4复合盐为熔剂,采用助熔剂法合成了α-Al2O3片晶,通过对合成片晶成型烧成,制备具有片状晶体支撑的氧化铝多孔陶瓷材料.并对α-Al2O3片晶形成过程,多孔陶瓷显气孔率、抗折强度、微观结构以及孔径分布进行了研究.研究结果表明,在KCl与Na2SO4复合盐存在情况下,可在900℃条件下合成分散性好,颗粒大小均匀的六方形α-Al2O3片晶,片晶的直径大约在10μm,厚度为0.3～0.5 μm.合成的α-Al2O3片晶具有非常好的烧结活性,在无添加烧结助剂的情况下,1600℃保温2h得到了显气孔率为41.74;,抗折强度为115.34MPa,孔径分布范围窄的氧化铝多孔陶瓷.窄的孔径分布以及优异的机械性能使其成为一种很有前途的膜支撑体和精确过滤材料.     

Controllable synthesis of well‐aligned CuO nanotube arrays using porous alumina templates

In order to further enhance the performance of CuO in currently existing applications, well‐aligned CuO nanotube arrays with different diameters were fabricated. During the synthesis process, porous anodic alumina films were fabricated, and then the synthesis of CuO nanotube arrays was realized by using the obtained porous anodic alumina films as templates. The morphology and structure of the obtained products has been confirmed by field‐emission scanning electron microscopy, transmission electron microscopy and X‐ray diffraction measurements. Due to the large surface area of the synthesized products, the prepared CuO nanotube arrays may have potential applications in catalyzing and gas sensing area.     

Surfactant directed synthesis of mesoporous alumina and α‐alumina single crystal

Mesoporous Al₂O₃ were positively synthesized via treatment of the freshly precipitated amorphous alumina gel using aluminium sulphate as aluminium source, and sodium dodecyl sulphate (SDS) as structure‐directing agent (SDAs). The microstructures, morphologies and textural properties of the as‐prepared materials were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and thermo gravimetric analysis (TG‐DTA). The calcined product at 600 °C was highly porous in nature having a BET surface area of 42 m²/g. These porous Al₂O₃ exhibits excellent adsorption performance for Congo red and the corresponding decolourisation efficiencies reached 99% in just 15 min at 27 °C. The subsequent calcined product at 1200 °C is the alpha alumina single crystal hexagonal platelets with rhombohedral crystallization.     

Three-dimensionally nanostructured alumina film on glass substrate: Anodization of glass surface

We report fabrication of a three-dimensionally nanostructured porous alumina film on a glass substrate exhibiting an angle-insensitive optical transmission property using a robust anodization with ‘fictive critical anodizing-voltage’ estimation technique. The fictive critical anodizing-voltage is estimated from a resistance profile curvature; it offers a limit of a maximum cell size of an anodization system. Using this technique, we have obtained an extra-large cell (over 1 μm) and thick (～2.5 μm) alumina film. Observation of a fine structure on the current density profile at the initial anodizing stage is also presented with resistance profiling, cross-sectional scanning and transmission electron microscopies.     

Structural control and magnetic properties of electrodeposited Co nanowires

Co nanowires with a preferred orientation were fabricated by direct current electrodeposition into the pores of porous anodic alumina membrane, and the structure of Co nanowires was studied by X-ray diffraction and high-resolution transmission electron microscopy with selected-area electron diffraction. It is found that the crystal structure of Co nanowires lies on the deposition potential. When electrodeposition is performed far from equilibrium conditions, i.e., at a high potential, face-centered cubic Co nanowires are deposited, while hexagonal close packing Co nanowires are formed at the low potential. The experimental results indicate that the orientation of the nanowires has effects on the coercivity for both hexagonal close packing (hcp) and face-centered cubic (fcc) Co.     

Synthesis of silica aerogel blanket by ambient drying method using water glass based precursor and glass wool modified by alumina sol

Silica aerogel blankets have been synthesized by ambient drying technique using cheap water glass as the silica source and glass wool modified by alumina sol. One step solvent exchange and surface modification were simultaneously conducted by immersing the wet hydrogel blanket in EtOH/TMCS/hexane solution. The synthesized silica aerogel blanket was light with the density of 0.143-0.104 g/cm³ and 89.4-95% porosity. The microstructure of silica aerogel blanket exhibits a porous structure consisting of glass fibers of diameter ∼2.5 μm interconnected with solid silica clusters (5-20 μm).     

Preparation and properties of alumina-organic compound aerogels

A wet alumina gel was obtained by cross-linking alumina sol particles from a hydrolyzed aluminum alkoxide with hexamethylene diisocyanate. The alumina gel cross-linked with hexamethylene was supercritically dried in a CO₂ extractor. The bulk density of the dried alumina-hexamethylene was one-third that of an alumina aerogel. Boehmite phase was observed in the dried alumina-hexamethylene aerogel. Needle-like texture was observed in the alumina-hexamethylene fired at a temperature of 1200°C for 5 h. The specific surface area of the dried alumina-hexamethylene aerogel was found to be less than that of the alumina aerogel, while its pore sizes were larger. The aerogel had a larger specific surface area after firing at 1200°C for 5 h. This larger surface area was attributed to a θ-phase in the alumina-hexamethylene aerogel, while the alumina aerogel had an -phase at that temperature. It is concluded that the temperature of the a phase transformation in the alumina-hexamethylene aerogel was higher than in the alumina aerogel. This difference was attributed to the lower packing density resulting from the addition of an organic compound, the existence of boehmite crystallites and the needle-like texture.     

Al2O3对低品位菱镁矿与天然硅石合成制备镁橄榄石的影响

以低品位菱镁矿与天然硅石为原料,以Al2O3为添加剂,通过反应烧结制备镁橄榄石。研究讨论Al2O3对镁橄榄石材料相组成、晶胞参数、微观结构及常温性能的影响。用XRD和SEM对烧后试样的相组成和显微结构进行表征。利用X’pert plus软件对试样中镁橄榄石相的晶胞参数进行计算。结果表明:以低品位菱镁矿轻烧氧化镁和天然硅石为原料,经1500℃煅烧合成制备的镁橄榄石中,由于Al2O3的加入,促进了系统中顽火辉石相的形成。Al2O3的加入导致镁橄榄石相的晶胞参数和晶胞体积的增大。随着Al2O3加入量增加,镁橄榄石的相对密度和常温耐压强度逐渐增加,说明了Al2O3对镁橄榄石的促烧结作用。