氧化铝/碳纳米管复合材料的制备及表征

采用聚乙烯醇对碳纳米管表面进行改性，通过化学沉淀法将Al(OH)₃均匀沉积在碳纳米管表面，然后在氮气气氛下于500 ℃煅烧2 h，制备出氧化铝/碳纳米管复合材料。采用TEM、TG、DTA、XRD、IR、氮吸附脱附(比表面积及孔结构分析)等对氧化铝/碳纳米管复合材料进行表征，结果表明:未经聚乙烯醇改性的碳纳米管，氧化铝与碳纳米管相互分离;经聚乙烯醇改性的碳纳米管，氧化铝与碳纳米管结合良好。经聚乙烯醇改性的碳纳米管表面均匀覆盖一层聚乙烯醇膜，通过聚乙烯醇的吸附作用， Al(OH)₃沉积在碳纳米管表面形成一层连续的覆盖层。     

二次纳米自组装大孔氧化铝贯穿孔道的NSA形成机理

采用纳米自组装法合成的大孔氧化铝催化材料FA-06,具有1.39 mL·g^-1的孔容、297 m²·g^-1的比表面积、32.4 nm的最可几孔径和81.85%的孔隙率,孔道集中分布于10~30 nm和30~60 nm的比例分别占35.61%和40.88%。GPC结果表明,对于形成反相超增溶胶束的高聚物RHP,可通过改变聚异丁烯马来酸酐(PIBSA)的量来控制其分散度和相对分子量,进而控制大孔氧化铝的孔道结构。TEM及SEM结果表明,纳米自组装氢氧化铝棒长600~800 nm,直径为250~300 nm,经550.0℃焙烧后,形成直径为150~300 nm,长度为400~600 nm的纳米氧化铝棒。从焙烧后的纳米自组装氢氧化铝的XRD结果证明了3种γ-Al₂O₃的前躯体完全转化为γ-Al₂O₃。结合TG的结果,表明在605.0℃时,拟薄水铝石完全转化为γ-Al₂O₃,总失重可达61.88%。基于以上实验结果,模拟了反向超增溶胶束、氢氧化铝及大孔氧化铝的分子自组装和纳米自组装的形成过程,并提出了纳米自组装大孔氧化铝贯穿孔道的NSA(Nano Self-Assembly)形成机理。     

二次纳米自组装大孔氧化铝贯穿孔道的NSA形成机理

采用纳米自组装法合成的大孔氧化铝催化材料FA-06, 具有1.39 mL·g^-1的孔容、297 m²·g^-1的比表面积、32.4 nm的最可几孔径和81.85%的孔隙率, 孔道集中分布于10~30 nm和30~60 nm的比例分别占35.61%和40.88%。GPC结果表明, 对于形成反相超增溶胶束的高聚物RHP, 可通过改变聚异丁烯马来酸酐(PIBSA)的量来控制其分散度和相对分子量, 进而控制大孔氧化铝的孔道结构。TEM及SEM结果表明, 纳米自组装氢氧化铝棒长600~800 nm, 直径为250~300 nm, 经550.0 ℃焙烧后, 形成直径为150~300 nm, 长度为400~600 nm的纳米氧化铝棒。从焙烧后的纳米自组装氢氧化铝的XRD结果证明了3种γ-Al₂O₃的前躯体完全转化为γ-Al₂O₃。结合TG的结果, 表明在605.0 ℃时, 拟薄水铝石完全转化为γ-Al₂O₃, 总失重可达61.88%。基于以上实验结果, 模拟了反向超增溶胶束、氢氧化铝及大孔氧化铝的分子自组装和纳米自组装的形成过程, 并提出了纳米自组装大孔氧化铝贯穿孔道的NSA(Nano Self-Assembly)形成机理。     

氧化铝纳米线的制备及其形成机理

采用二次铝阳极氧化技术, 制备高度有序的铝阳极氧化膜(AAO模板). 经X射线衍射(XRD)分析, 模板为无定形结构. 将模板放入腐蚀液中, 可获得大量无定形结构的氧化铝纳米线. 模板在800 ℃下退火4 h后, 变为γ-Al2O3结构, 采用类似腐蚀液溶解模板, 得到大量γ-Al₂O₃纳米线. 研究了腐蚀液种类、腐蚀时间和模板晶体结构等因素对生成氧化铝纳米线的影响, 并利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和XRD对纳米线的形貌与结构进行了表征. 结果表明, 在多种腐蚀液中, 均可获得氧化铝纳米线; 随着腐蚀时间的增加, 纳米线的长度增加, 直径变小, 长径比增大; 氧化铝纳米线的晶体结构与所采用模板的晶体结构一致. 此外, 还采用原子力显微镜(AFM)和SEM对AAO膜的表面形貌及其结构特点进行了详细的观测, 并以此为基础讨论了氧化铝纳米线的形成机理, 认为AAO模板本身存在的花状微结构是形成纳米线的内因, 花瓣间的凹陷部位首先被腐蚀断裂, 形成氧化铝纳米线.     

以离子液体为铝源和模板合成氧化铝纳米纤维

以咪唑类氯铝酸盐离子液体(x Al Cl_3-[C_(10)mim]Cl)为模板和铝源,采用溶胶-凝胶法合成了氧化铝纳米纤维.考察了氯铝酸盐离子液体中Al Cl_3的摩尔分数以及焙烧温度对纤维状氧化铝合成的影响,通过X射线衍射仪(XRD)、场发射透射电子显微镜(TEM)和物理吸附仪对样品进行了表征.研究结果表明,氯铝酸盐离子液体可以同时作为模板剂和铝源合成具有一定形貌的氧化铝.当Al Cl_3的摩尔分数x(Al Cl_3)=0.5时,可以合成出纳米纤维状氧化铝,纳米纤维直径约为2 nm,长度约为200 nm,比表面积为238.38 m~2/g,孔容为0.54 cm~3/g,平均孔径为8.43 nm.合成的氧化铝具有高的热稳定性,在900℃下焙烧依然能够很好地保持其形貌结构和γ晶型.此外,提出了氢键共π-π键堆积机理来解释超细纤维氧化铝的合成过程.     

氧化铝胶体的添加对氧化铝γ→α相变的影响

在γ-Al2O3粉体中添加氧化铝胶体,研究其对氧化铝α相变的影响.结果表明,与α氧化铝粉体籽晶相比较,氧化铝胶体也可以起到籽晶的作用;由于其颗粒较小、在γ-Al2O3中分散均匀且能与之紧密接触,大大降低了α相变温度,改善了煅烧产物的微结构,从而得到分散均匀、平均粒径< 100 nm的α氧化铝超细粉体.根据对粉体形貌TEM的观察,初步探讨了添加氧化铝胶体的前驱体α相变的过程.     

硅烷偶联剂表面修饰纳米氧化铝

硅烷偶联剂KH570在乙醇溶剂中以酸水溶液为催化剂进行水解后对纳米氧化铝进行湿法表面修饰改性。用灼烧法测定了粉体表面偶联包覆率,以此为指标研究了KH570的水解条件及其对偶联效果的影响。结果表明,酸种类等水解条件对偶联效果有很大影响;适宜的偶联剂水解条件为:草酸作催化剂,调pH值为3~4,室温下水解1h。适宜的纳米氧化铝表面修饰条件为:偶联剂质量分数4.5%,在45℃偶联5.5h。经红外光谱(IR)分析,氧化铝的偶联修饰机理为:硅烷偶联剂与纳米氧化铝表面的羟基发生化学键合,从而实现纳米氧化铝的表面修饰改性。改性纳米氧化铝在有机相中的分散性和稳定性均得到了改善。     

微球形氧化铝的制备及其表征研究

采用油柱成型法制备了一种核壳结构磁性氧化铝球,结果表明以球状Fe3O4为磁核合成的Fe3O4/Si O2/γ-Al2O3磁性球在500°C煅烧下,表面光滑,粒径分布为100~300μm,比表面积为200m2/g,平均孔径为16.8nm,孔容为0.77cm3/g,比饱和磁化强度较高(15.1emu/g),矫顽力和剩磁较低。     

三维贯穿大孔氧化铝的孔道改性、表征及转化机制

利用相分离技术制备了非晶三维贯穿大孔氧化铝初始材料,然后通过氨水水热改性处理,使其大孔形态发生了显著改变,孔壁边缘生长有尺寸为50-300 nm的片状聚集体,大孔尺寸由430 nm下降到250 nm,但仍然保持蠕虫状三维贯穿且空间分布均匀的特性。改性后的氧化铝材料经550℃焙烧转化为高结晶度γ氧化铝,比表面积达到331 m²/g,具有8.9 nm及250 nm两种集中的孔径分布,L酸度及抗压强度均有所提高。研究表明,无定形水合羟基铝离子聚合物与氨水发生再水合反应生成薄水铝石中间物,因此,可在较低的焙烧温度下转晶为γ态;大孔孔壁边缘的AlOOH晶粒受NH₄⁺模板诱导作用从里向外重排形成片状聚集体,从而改变了大孔的形态。     

煅烧工艺对纳米MgO粒径及活性的影响

以六水合氯化镁和碳酸钠为原料,乙二醇为介质,采用直接沉淀法制备了纳米MgO粉体。通过热重分析确定了前驱物的煅烧温度范围,采用柠檬酸值法、静态除氟测定了煅烧产物的活性,并与普通MgO的活性进行了比较,X射线衍射法计算了煅烧产物的平均粒径,探讨了煅烧温度和保温时间对纳米MgO粒径及活性的影响。结果表明:当煅烧温度为430℃和保温时间为1.5h时,得到的纳米MgO活性最高(CAA值为14.35s),粒径较小15.77nm;而当煅烧温度为450℃和保温时间为1.5h时得到的纳米MgO活性较高(CAA值为23.44 s),粒径最小11.47nm。可见,煅烧工艺对纳米MgO粒径及活性影响很大,超细MgO并不一定是高活性MgO。另外,探讨了碱式碳酸镁低温分解机理。     

Sol-gel synthesis of K3InF6 and structural characterization of K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18

K₃InF₆ is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K₂InC₁₀O₁₀H₆F₉, K₃InC₁₂O₁₄H₄F₁₈ and K₃InC₁₂O₁₂F₁₈. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K₃InF₆ by decomposition at high temperature. The crystal structure of K₃InC₁₂O₁₄H₄F₁₈ is characterized by complex anions [In(CF₃COO)₄(OH_x)₂]^(5−2x)− and isolated [CF₃COOH_2−x]^(x−1)− molecules with x=2 or 1, surrounded by K⁺ cations. The crystal structure of K₃InC₁₂O₁₂F₁₈ is only constituted by complex anions [In(CF₃COO)₆]³⁻ and K⁺ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K₂InC₁₀O₁₀H₆F₉ and K₃InC₁₂O₁₂F₁₈ were also performed at room temperature on pulverized crystals.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

Non-centrosymmetric Ba3Ti3O6(BO3)2

The compound previously reported as Ba₂Ti₂B₂O₉ has been reformulated as Ba₃Ti₃B₂O₁₂, or Ba₃Ti₃O₆(BO₃)₂, a new barium titanium oxoborate. Small single crystals have been recovered from a melt with a composition of BaTiO₃:BaTiB₂O₆ (molar ratio) cooled between 1100°C and 850°C. The crystal structure has been determined by X-ray diffraction: hexagonal system, non-centrosymmetric space group, a=8.7377(11) Å, c=3.9147(8) Å, Z=1, wR(F²)=0.039 for 504 unique reflections. Ba₃Ti₃O₆(BO₃)₂ is isostructural with K₃Ta₃O₆(BO₃)₂. Preliminary measurements of nonlinear optical properties on microcrystalline samples show that the second harmonic generation efficiency of Ba₃Ti₃O₆(BO₃)₂ is equal to 95% of that of LiNbO₃.     

Ion-beam irradiation of lanthanum compounds in the systems La2O3-Al2O3 and La2O3-TiO2

Thin crystals of La₂O₃, LaAlO₃, La_2/3TiO₃, La₂TiO₅, and La₂Ti₂O₇ have been irradiated in situ using 1 MeV Kr²⁺ ions at the Intermediate Voltage Electron Microscope-Tandem User Facility (IVEM-Tandem), Argonne National Laboratory (ANL). We observed that La₂O₃ remained crystalline to a fluence greater than 3.1×10¹⁶ ions cm⁻² at a temperature of 50 K. The four binary oxide compounds in the two systems were observed through the crystalline-amorphous transition as a function of ion fluence and temperature. Results from the ion irradiations give critical temperatures for amorphisation (T_c) of 647 K for LaAlO₃, 840 K for La₂Ti₂O₇, 865 K for La_2/3TiO₃, and 1027 K for La₂TiO₅. The T_c values observed in this study, together with previous data for Al₂O₃ and TiO₂, are discussed with reference to the melting points for the La₂O₃-Al₂O₃ and La₂O₃-TiO₂ systems and the different local environments within the four crystal structures. Results suggest that there is an observable inverse correlation between T_c and melting temperature (T_m) in the two systems. More complex relationships exist between T_c and crystal structure, with the stoichiometric perovskite LaAlO₃ being the most resistant to amorphisation.     

Magnetic diphase nanostructure of ZnFe2O4/γ-Fe2O3

Magnetic diphase nanostructures of ZnFe₂O₄/γ-Fe₂O₃ were synthesized by a solvothermal method. The formation reactions were optimized by tuning the initial molar ratios of Fe/Zn. All samples were characterized by X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and Raman spectra. It is found that when the initial molar ratio of Fe/Zn is larger than 2, a diphase magnetic nanostructure of ZnFe₂O₄/γ-Fe₂O₃ was formed, in which the presence of ZnFe₂O₄ enhanced the thermal stability of γ-Fe₂O₃. Further increasing the initial molar ratio of Fe/Zn larger than 6 destabilized the diphase nanostructure and yielded traces of secondary phase α-Fe₂O₃. The grain surfaces of diphase nanostructure exhibited a spin-glass-like structure. At room temperature, all diphase nanostructures are superparamagnetic with saturation magnetization being increased with γ-Fe₂O₃ content.     

B2O3-Bi2O3-ZnO-Al2O3玻璃助烧剂对BaTiO3陶瓷烧结条件、晶体结构和介电性能的影响

通过调节B₂O₃‐Bi₂O₃‐ZnO‐Al₂O₃(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO₃)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明：添加适量的BBZA玻璃能够有效地将BaTiO₃陶瓷烧结温度由1350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO₃的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO₃陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO₃晶粒表面。优化的BaTiO₃陶瓷制备条件如下：BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO₃陶瓷介电常数达到1364,介电损耗低至1.2%。     

B2O3-Bi2O3-ZnO-Al2O3玻璃助烧剂对BaTiO3陶瓷烧结条件、晶体结构和介电性能的影响

通过调节B₂O₃-Bi₂O₃-ZnO-Al₂O₃(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO₃)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明：添加适量的BBZA玻璃能够有效地将BaTiO₃陶瓷烧结温度由1 350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO₃的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO₃陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO₃晶粒表面。优化的BaTiO₃陶瓷制备条件如下：BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO₃陶瓷介电常数达到1 364,介电损耗低至1.2%。     

Synthesis, crystal structure, infrared and Raman spectra of Sr4Cu3(AsO4)2(AsO3OH)4·3H2O and Ba2Cu4(AsO4)2(AsO3OH)3

The two new compounds, Sr₄Cu₃(AsO₄)₂(AsO₃OH)₄·3H₂O (1) and Ba₂Cu₄(AsO₄)₂(AsO₃OH)₃(2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO-CuO-As₂O₅-H₂O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å³, Z=4 for 1; space group P4₂/n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å³, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu²⁺-(XO₄)³⁻ layers (X=P⁵⁺, As⁵⁺) linked by M cations (M=alkali, alkaline earth, Pb²⁺, or Ag⁺) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu₂O₈ centrosymmetric dimers crosslinked by As1φ₄ tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu₂O₈ centrosymmetric dimers of CuO₅ edge-sharing polyhedra, crosslinked by As1O₄ tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed.     

Crystal growth, structural characterization and magnetic properties of Ca3CuRhO6, Ca3Co1.34Rh0.66O6 and Ca3FeRhO6

Single crystals of Ca₃CuRhO₆, Ca₃Co_1.34Rh_0.66O₆ and Ca₃FeRhO₆ were synthesized by high temperature flux growth in molten K₂CO₃ and structurally characterized by single crystal X-ray diffraction. While Ca₃Co_1.34Rh_0.66O₆ and Ca₃FeRhO₆ crystallize with trigonal (rhombohedral) symmetry in the space group , Z=6: Ca₃Co_1.34Rh_0.66O₆a=9.161(1) Å, c=10.601(2) Å; Ca₃FeRhO₆a=9.1884(3) Å, c=10.7750(4) Å; Ca₃CuRhO₆ adopts a monoclinic distortion of the K₄CdCl₆ structure in the space group C2/c, Z=4: a=9.004(2) Å, b=9.218(2) Å, c=6.453(1) Å, β=91.672(5). All crystals of Ca₃CuRhO₆ examined were twinned by pseudo-merohedry. Ca₃CuRhO₆, Ca₃Co_1.34Rh_0.66O₆, and Ca₃FeRhO₆ are structurally related and contain infinite one-dimensional chains of alternating face-sharing RhO₆ octahedra and MO₆ trigonal prisms. In the monoclinic modification, the copper atoms are displaced from the center of the trigonal prism toward one of the rectangular faces adopting a pseudo-square planar configuration. The magnetic properties of Ca₃CuRhO₆, Ca₃Co_1.34Rh_0.66O₆, and Ca₃FeRhO₆ are discussed.     

LiNi0.8Co0.15Al0.05O2正极材料的FePO4包覆改性

使用液相包覆工艺对LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA)材料进行FePO_4包覆改性,利用FePO_4优异的结构稳定性与热稳定性,对NCA的长期可靠性与安全性能进行改良。重点研究FePO_4包覆对NCA材料的改性效果,以及不同包覆量造成的NCA材料电化学性能差异。表面包覆的FePO_4保护层,能够防止NCA材料与电解液直接接触发生副反应,抑制长期循环过程中过渡金属离子的溶出,保持结构的长期稳定性。当包覆量为1.0%(w/w)时,NCA材料表现出最优的综合性能,充放电循环800次后,容量保持率依然高达95%,25℃下存储100 d后,容量保持率也高于95%,达到了兼顾能量密度、使用寿命及安全性能的理想效果。