纳米三氧化二铝在水热条件下的聚集生长模式研究

通过对产物形貌及晶粒度测试,掌握水热温度、水热时间对水热产物影响的基本规律,运用临界成核理论及颗粒成长理论解释提高水热温度、延长水热时间导致的颗粒形态逆转的原因,结合晶体成长阶段性理论,揭示了提高水热温度或延长水热时间以及增大前躯体过饱和状态条件下诱发的两类聚集生长方式,阐述了第Ⅰ类聚集和第Ⅱ类聚集生长的根本原因,其中第Ⅰ类聚集生长是因为过饱和度的增大使得部分AlOOH颗粒在水热溶液中溶解形成的Al^3＋聚集体在另一些颗粒表面的叠合,而发生第Ⅱ类聚集生长的本质是由于pH酸碱环境使得多个AlOOH颗粒通过某些结构相容晶界间的键联而形成的具有特殊生长形态的颗粒。     

烧结温度对纳米氧化铝晶体结构的影响

对前期水热法制得的多种形貌的异性纳米AlOOH进行了不同温度的烧结试验。试验结果表明,烧结温度不同,前驱体发生的转型则不同。烧结温度为700℃时,生成立方晶格的γ-Al2O3,烧结温度为1100℃时,生成六方a-Al2O3。经扫描电镜SEM及粒度检测发现,经表面修复之后的纳米AlOOH在烧结之后维持了产物基本形貌的不变性,克服了以往晶须一经烧结长度就发生断裂、片状一经烧结就发生粘连、颗粒一经烧结就发生团聚的现象,基本上都保持了良好的分散性。这对后期工业的推广应用具有重要的现实意义和经济价值。     

水热制备纳米AlOOH晶须条件控制形貌TEM分析

本论文针对水热制备纳米AlOOH晶须的条件控制做了较为全面的探索,以盐酸、铝酸钠为原材料,通过添加单组分多组分添加剂,考察了温度、时间,以及加转子磁振动等试验方式对晶须形貌的影响,探索适宜的AlOOH晶须制备奈件优化组合通过透射电镜分析检测其形貌特征,长度及直径大小,通过XRD衍射分析,总结出AlOOH定向结晶的一般习性,在综合各种样品的形貌特点的基础上,进一步探索制备形貌较好的AlOOH晶须的优化工艺方法.     

硝酸对AlOOH溶胶流变特性的影响

为控制氧化铝陶瓷膜制备中的涂膜工艺,以异丙醇铝为原料,硝酸为胶溶剂,制备了AlOOH溶胶。通过旋转流变仪、Zeta电位分析仪等表征手段,研究了硝酸用量对AlOOH溶胶流变特性的影响。结果表明,硝酸与异丙醇铝摩尔比R(n(HNO₃):n(Al(C₃H₇O₃)₃))为0.3~0.6时,AlOOH溶胶表现出假塑性流体特征。通过Herschel-Bulkley模型拟合流变测试数据得到的流动指数随着R的增大而减小,稠度系数随之增大;振幅扫描中储能模量(G′)与损耗模量(G″)均随着R增大而上升;频率扫描中G′与G″的交点随着R的增大而逐渐靠近低频。随着R的增大,AlOOH溶胶假塑性增强,稠度增大,弹性与黏性均上升,更易转变为凝胶。当R≥0.7时已经转化为凝胶,不再符合流体规律。Zeta电位的高低影响AlOOH溶胶的分散性,进而影响上述现象。     

Microcrystal Structure Analysis about Precursor AlOOH of Nano-Alumina

The nano Al₂O₃ has good application foreground in many fields as the properties of adsorption and catalytic activity. In order to disclose the mechanism and the characteristic of crystal structure of heterotypic nano alumina in a composite system, this paper utilizes leading metal embedded slicing micron-nano representation method at home and abroad, to analyze the microcrystal structure of heterotypic nano AlOOH products particularly, discloses the acting mechanism of isomorphous replacement of iron ions and intercalation of sulfate ions from the polar additive in the crystal growing process, and points out the surface restoration function of the nano AlOOH crystalline surfaces from the polar surfactant additive. The accuracy of the conclusion is validated by using X-diffraction and infrared spectrum.     

拟薄水铝石结构的演化

以理学Ｄ／ｍａｘ－３ＢＸ射线衍射仪，ＴＧ－ＤＴＡ，ＩＲ－４４０红外光谱等方法，研究了拟薄水铝石结构的演化。     

极性阳离子条件下AlOOH“复合生长基元”模型研究

结合水解特点,根据负离子配位原理,构建了添加极性阳离子条件下的AlOOH＂复合生长基元＂模型,从原子＂聚集体＂的角度,揭示了铁离子的＂同晶替代＂作用。用实验结果验证了理论推导的正确性,并用能谱检测结果证明了添加元素的存在。     

溶胶-凝胶法制备RDX/AlOOH

以氯化铝为前驱物,N,N-二甲基甲酰胺为AlCl3.6H2O和RDX的溶剂,1,2-环氧丙烷为胶凝剂,常温常压下,采用溶胶-凝胶法制备RDX/AlOOH复合炸药,产物用超临界流体干燥后得固体粉末。用扫描电镜和DSC研究了复合炸药的形貌分析和热分解特性。测试了复合炸药的撞击感度、摩擦感度。结果表明,溶胶-凝胶法与超临界流体干燥技术相结合,可以较好地保持凝胶的多孔结构;其热分解过程不同于物理掺杂的混合炸药,DSC曲线上熔化吸热峰几近消失,RDX/AlOOH复合炸药的撞击感度和摩擦感度均较低。     

Enhanced physical and mechanical properties of resin added with aluminum oxyhydroxide for dental applications

Resin has limited applications however, its composites with metal oxides exhibited improved characteristics for numerous applications such as dental restoration, dentures etc. Herein, various compositions were fabricated by substituted aluminum oxyhydroxide (AlOOH) into resin via a scalable heat cure process. For phase identification and structural study, XRD and FT-IR techniques were employed. As increasing the content of AlOOH into the PZ {Poly (methyl-methacrylate)-zirconia, (PMMA-ZrO₂)} matrix, the percentage of crystallinity and the crystallite size were also estimated and varied from 14.8 to 18.4 and 1.48 nm–1.82 nm respectively. Moreover, to reveal the surface morphology, optical and mechanical behaviour of fabricated nano-composites, the SEM, UV–Vis and Universal testing machine (UTM) were also performed. The direct, indirect band gap, urbach energy of the fabricated composites were noticed within the range of 5.14 ± 0.005–5.19 ± 0.005 eV, 5.31 ± 0.005–5.35 ± 0.005 eV, and 189 ± 3.78–69.6 ± 1.39 eV respectively. The skin depth of the nanocomposites were also studied, the cut-off energy and cutoff-wavelength are 5.66 eV and 220 nm. However, the compressive strength, flexural strength, and the lowest friction coefficient value at 1 m/s sliding speed of the best composite sample (PZA15) are 85.2 MPa, 56.7 MPa and 0.311. The highest flexural modulus (846 MPa) of the PZA15 were determined using the 3-point bending test. Further, to check the biocompatibility of these resin-based composites the MTT assay was carried out. The synthesized composite (PZA15) was found to be highly biocompatible with enhanced mechanical and tribological performances.     

High-toughness mullite ceramics fabricated by hot-press sintering of pyrophyllite and AlOOH at low temperatures

High-toughness mullite ceramics were fabricated through hot-press sintering (HPS) of pyrophyllite and AlOOH, which were wet-milled and well mixed using a planetary ball mill. The impacts of sintering temperatures and contents of AlOOH on mullite phase formation, densification, microstructure and mechanical properties in ceramic materials were investigated through XRD, SEM and mechanical properties determination. The results indicated that high-toughness mullite ceramics could be successfully prepared by HPS at temperatures higher than 1200°C for 120 min. Increasing the sintering temperature from 1000 to 1300°C significantly enhanced the flexural strength and fracture toughness of samples. The highest flexural strength of 297.97±25.32 MPa and fracture toughness of 4.64±0.11 MPa⋅m^1/2 were obtained for samples sintered at 1300°C. Further increase of temperature to 1400°C resulted in slight decrease of flexural strength and fracture toughness. Compared with the mullite ceramics prepared only using pyrophyllite as raw material, incorporation of AlOOH into raw material significantly increased the mechanical properties of final mullite ceramics. And stoichiometric AlOOH and pyrophyllite as starting material gave the best performance in fracture toughness. The high-toughness of mullite ceramics were ascribed to the high mullite phase content, fine mullite whiskers and in situ formed, intertwined three-dimensional network structure obtained through HPS at a low temperature of 1300°C.