聚丙烯酰倍半硅氧烷(MPMS-SSO)有机/无机杂化气凝胶中的N_2等温吸脱附特性分析

采用自制的甲基丙烯酰多羟基倍半硅氧烷(MPMS-SSO)制备了UV固化的有机/无机杂化湿凝胶。N2等温吸脱附实验表明,气凝胶样品具有典型低压吸附滞后现象。将POSS分子中的笼形结构抽象为不同形状的极微孔模型,并对其进行了相关的数据计算,表明低压区吸附滞后现象可能与笼形结构对N2分子的强吸附有关。场发射扫描电子显微镜(FESEM)、高分辨透射电镜(HRTEM)分析表明构成气凝胶三维珍珠链结构的骨架的颗粒尺寸为20～30nm,骨架上具有约5～10nm的孔洞结构,珍珠链之间的孔洞结构尺寸约20nm,HRTEM表明气凝胶骨架的基本颗粒有机、无机组分分布均一,没有明显的相界面,初级颗粒约为几个纳米大小,由不同数目的倍半硅氧烷分子聚合而成。     

SiO_2-ZrO_2气凝胶的制备及其对铈的吸附性能研究

采用分相法制备了不同ZrO_2含量的SiO_2-ZrO_2(5%和10%,质量分数)复合气凝胶。借助于SEM、XRD、FT-IR等手段对SiO_2-ZrO_2复合气凝胶的表面形貌、相结构和原子配位状态进行表征,并测试了其对铈的吸附性能。结果表明:SiO_2-ZrO_2复合气凝胶具有连续的多孔网络结构,且晶型呈非晶态;气凝胶中含有大量的Si-O-Zr键,各成分在原子尺度上均匀分布;SiO_2-ZrO_2复合气凝胶对Ce拥有优异的吸附性能,吸附216h后对Ce的最大吸附量为211.56mg/g。     

溶胶-凝胶法制备的Al2O3涂层及其对γ-TiAl合金的高温氧化防护

以异丙醇铝(Al(OC3H7)3)为原料,采用溶胶-凝胶法在γ-TiAl基合金表面制备Al2O3涂层.以空白样品做对照,研究涂层的作用机制以及涂层对γ-TiAl基合金1 000 ℃高温氧化行为的影响.结果表明:采用浸涂工艺制备的涂层表面均匀、无裂纹,主要由γ- Al2O3相组成,厚度约为0.8 μm;等温氧化110 h后,空白试样和Al2O3涂层试样的氧化抛物线速率常数分别为4.85×10-12 和 3.31×10-13 g2/(cm4-s),涂层明显提高合金的抗氧化能力及抗循环氧化能力;空白样品上形成的氧化膜出现分层现象,而在涂层样品的Al2O3涂层中存在金红石型TiO2和α-Al2O3混合物.     

Sn(OBun)4溶胶-凝胶法制备SnO2气凝胶

以锡酸正丁酯(Sn(OBun)4)为前驱体,利用溶胶-凝胶工艺和CO2超临界干燥技术制备了透明和半透明的单块SnO2气凝胶.这些二氧化锡气凝胶密度小,孔隙分布宽,比表面积高.SEM分析表明,这种气凝胶由尺寸不一的如棉花团一样的团块堆积而成,团块之间为大尺寸孔隙(＞50 nm),棉花团块内还具有细小的微孔(＜2 nm)和介孔(＜50 nm).TEM分析表明,在不同的放大倍数下,二氧化锡气凝胶具有相似的结构.     

高分子纤维增韧SiO_2气凝胶复合材料的制备

以正硅酸乙酯为硅源,乙醇和水为溶剂,芳纶纤维为增强相,通过溶胶凝胶及常压干燥等步骤,实现了芳纶增韧SiO_2气凝胶复合材料的非超临界制备.采用扫描电镜、吸附-脱附等分析手段及热导率测试对所得气凝胶样品进行结构分析和性质表征.结果表明,调节反应体系的各反应参数可以获得具有不同外形、密度及热导率的复合材料;所得气凝胶平均孔径约为10～20 nm,比表面积可达1000 m~2/g,可望在隔热材料等领域得到应用.     

碳包覆铜纳米颗粒的比表面积和孔结构

采用直流电弧放电等离子体技术制备碳包覆铜纳米颗粒,并对样品的形貌、晶体结构、粒度、比表面积和孔结构采用高分辨透射电子显微镜(HRTEM)、X射线衍射仪(XRD)和N_2吸-脱附等测试手段进行分析。结果表明:直流电弧等离子体技术制备的碳包覆铜纳米颗粒具有典型的核壳型结构,内核为面心立方的金属铜,外壳为石墨碳层。颗粒主要呈球形或椭球形,粒度相对比较均匀,分散性良好,粒径分布在20~100 nm范围内,平均粒径为50 nm,外壳碳层的厚度为10 nm。碳包覆铜纳米颗粒的等温吸附曲线属Ⅳ型,晶粒之间的孔隙以介孔为主,样品的BET比表面积为33 m~2/g,当量粒径为45 nm,与TEM和XRD测得的结果基本一致。BJH吸附累积总孔孔容与BJH吸附平均孔径分别为0.112 cm~3/g和13 nm。     

负载胺基氧化硅气凝胶的制备及其CO_2吸附性能研究（英文）

为了提高氧化硅气凝胶对低分压CO_2的吸附性能,以正硅酸乙酯和氨丙基三乙氧基硅烷为先驱体,通过溶胶-凝胶过程制备了比表面积较大、表面胺基丰富的负载胺基氧化硅气凝胶。负载胺基氧化硅气凝胶对低分压CO_2的吸附量随着氮含量的增加而增大。在25℃时,对CO_2含量为0.5%(总压为100kPa)、相对湿度为60%的气体的CO_2吸附量可达1.85mmol/g。由于胺基通过化学键与氧化硅气凝胶骨架相连,同第2个循环相比,负载胺基氧化硅气凝胶第10个循环的吸附量没有出现下降,这说明负载胺基氧化硅气凝胶具有良好的长期使用性能。     

阳极氧化钽酸锂薄膜在NaOH溶液中的腐蚀行为研究

通过阳极氧化法在高纯钽片表面制备了钽酸锂复合薄膜,采用浸泡失重法和电化学测试法考察了镀膜前后样品在10% (质量分数) NaOH溶液中的腐蚀行为。利用X射线衍射仪、扫描电子显微镜及能谱仪分别对薄膜的物相组成、表面及截面形貌、膜层厚度进行了测试分析。结果表明,阳极氧化后得到的复合薄膜由钽酸锂和氧化钽组成;该薄膜与基体之间结合良好,厚度约3 μm;镀膜后样品的质量腐蚀速率至少减少了6倍,腐蚀电流密度下降了2个数量级,腐蚀96 h后样品表面没有明显变化。而对比的纯钽样品却发生了严重的腐蚀反应,生成了很多长条状和多棱柱状的腐蚀产物Na₃TaO₄、Na₂Ta₂O₆和Na₈Ta₆O₁₉。     

SiO_2气凝胶/全氟磺酸树脂杂化薄膜制备及吸附性能

采用双连续孔道结构的多孔材料如:二氧化硅,二氧化钛以及他们组成的复合材料可以吸附重金属、放射性废液中的污染物。通过溶胶凝胶法结合分相法制备出具有双连续孔道和高孔容的SiO_2气凝胶,并以全氟磺酸树脂(Perfluorosulfonated Resin,简称PSR)为载体及改性剂,将无机多孔材料与全氟磺酸树脂(Nafion)溶液复合,通过流延法成膜,实现对金属离子物理吸附和离子交换的双重作用。吸附过程采用铈作为放射性核素钚元素的模拟元素,研究了SiO_2气凝胶/全氟磺酸树脂复合薄膜对铈的吸附性能。结果发现SiO_2气凝胶质量分数为15%时,复合膜性能达到最佳,吸附10h后,87.67%的核素被吸附于薄膜中,从而为高放废液的处理提供一条新的技术途径。     

炭干凝胶的溶胶-凝胶法制备参数的正交优化与多孔结构分析（英文）

以间苯二酚(R)和糠醛(F)为反应物,以四氮六甲胺(H)为催化剂,在异丙醇(I)溶剂中采用溶胶-凝胶方法制备出RF有机气凝胶,通过常压干燥和氮气保护烧结碳化后,制得炭干凝胶(CXs)。采用三水平三因素正交优化法实现制备工艺参数的正交优化。采用SEM、XRD、FR-IR和N_2吸附法对CXs进行表征和分析。正交优化结果表明,R/F(摩尔比)=0.7、R/H(摩尔比)=25、P/I(体积比)=0.07为最优工艺参数。制得的CXs最低密度仅为0.083g/cm~3。FR-IR表明:-CH_2和CH_2-O-CH2是RF有机气凝胶纳米结构产生的主要基团。XRD分析表明:CXs的碳结构呈现微小晶体的非晶态。CXs是典型的介孔材料,其比表面积在550~800 m~2/g之间,平均孔径为2~9 nm。     

钽氧纳米片的机械化学法制备及表征

利用固相化学法在800℃合成了前躯体钽酸钾,新型剪切力机械剥离法对其研磨剥离得到了较大面积的钽氧纳米片。主要讨论了机械剥离过程中不同的研磨剂、研磨频率对钽酸钾剥离的影响,不同的超声时间对合成分散性好、均一稳定的钽氧纳米片溶胶浓度的影响。运用X-射线衍射技术,紫外可见分光光度计,透射电子显微镜以及Zeta电位分析仪等对前躯体化合物钽酸钾及钽氧纳米片结构进行分析和表征,证实了在不同条件下钽氧纳米片二维结构的存在。     

Effect of dehydration on porous structure of monolithic aerogels based on fibrous aluminum oxyhydroxide

Aluminum oxide monolithic aerogels (PMAOs) with specific surfaces of up to 400 m²/g and densities of up to 0.004 g/cm³ were obtained by the direct oxidation of metallic aluminum by water vapors. Studies of the obtained aerogels using the methods of scanning and transmission electron microscopy showed that a freshly prepared aerogel represents the amorphous structure from alumina fibrous with a diameter of about 5 nm. Parameters of a porous aerogel structure were determined from the isotherms of adsorption of nitrogen vapors at 77 K. It is shown that the specific surface area decreases by 50% upon the dehydration of aerogel by temperature pretreatment at 900°C until the phase transition temperature is reached. At the same time, heat treatment at temperatures above 1200°C results in a phase transition at which significant contraction of structure occurs and the specific surface area decreases to 20 m²/g. The number of primary adsorption centers was obtained from comparative plots of water vapor adsorption. It was found that preliminary dehydration only slightly affects the number of primary centers of water adsorption.     

An investigation of the effect of thermal cycling on plasma‐sprayed zirconia/NiCoCrAlY thermal barrier coating

The microstructural change, crack initiation and spallation of a vacuum plasma sprayed (VPS) thermal barrier coating on an INCONEL‐738 superalloy substrate were investigated after successive 300 h thermal cycles at 1050°C. The coating was characterised using Raman spectroscopy, scanning electron microscopy (SEM) energy dispersive X‐ray analysis (EDX) and Auger electron spectroscopy (AES). Localised micro‐cracks at the yttrium (III) oxide stabilised zirconium (IV) oxide (YSZ) ceramic coating/thermally grown oxide (TGO) interface were observed after 8 cycles. Spallation of the YSZ coating occurred after approximately 21 cycles. Significant amounts of the elements titanium, tantalum and chromium were found within the TGO together with the formation of nickel, cobalt and chromium‐rich oxides at this TGO/YSZ interface.     

The effect of nanoporous silica aerogel on corrosion protection properties of epoxy coatings on carbon steel

In this paper, due to special properties of aerogels such as ultra-low density and hydrophobic nature of aerogels, this nanomaterial was used as anticorrosive pigments. Silica aerogel was dispersed in epoxy resin by using sonication method. The dispersion of nanoparticles were characterized by transmission electron microscopy. The anticorrosive properties of these coatings were investigated by salt-spray and electrochemical impedance spectroscopy methods in a 3.5 wt % NaCl solution. Impedance parameters showed a decrease in coating resistance over immersion time. Results indicated that epoxy coatings containing nano silica aerogel could significantly increase the corrosion resistance of composite coatings compared to those of pure epoxy and the highest value was obtained for 0.5% aerogel nanocomposite coatings after 160 days immersion. Pull off adhesion test showed the highest value of adhesion was related to coating containing 0.5% aerogel. According to salt-spray methods, it was found that the best results were obtained with coatings containing 0.5 and 1 wt % of silica aerogel.     

Characterization of air-formed surface oxide film on Ti-29Nb-13Ta-4.6Zr alloy surface using XPS and AES

The surface oxide film on a Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) was precisely characterized using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to understand the composition and chemical state of the surface oxide film of TNTZ. For comparison, the component metals, titanium, niobium, tantalum, and zirconium, were also characterized to consider the effect of those on the formation of the surface oxide film on their alloy. The characterization of the surface oxide films on TNTZ and its component revealed the following issues. The surface oxide film on TNTZ consists of a composite oxide that contains titanium, niobium, tantalum, and zirconium but forms continuous layer and is very thin, ca. 3.7 nm. The oxide film is not completely oxidized because it contains various valences of cations. In particular, the oxidation of tantalum is inhibited in the oxide. Tantalum is enriched in the substrate in TNTZ just under the surface oxide because of this inhibition in the oxidation. The formation of the surface oxide film in TNTZ is predominantly governed by titanium. The preferential oxidation of an element is not always dependent on the initial oxidation potential of that element, the relationship between the oxidation energy from a smaller valence to a larger valence, and the dehydration process. In other words, a complicated competition governs the resultant composition of surface oxide.     

Modified aging process for silica aerogel

To increase the porosity and monolithic performance of silica aerogel, two methods were used to age the silica gels derived from tetraethoxysilane (TEOS) by two-step sol–gel process: aging in 100 °C-autoclave with TEOS/ethanol mixed solution and in pure ethanol at room temperature. The structural characteristics and physical properties of the resultant two kinds of aerogels after supercritical CO₂ drying were investigated and compared with the help of infrared spectra (IR), N₂ absorption, differential scanning calorimetry (DSC)/thermogravimetry (TG) and high-resolution ²⁹Si nuclear magnetic resonance (NMR) techniques. Aging in 100 °C-autoclave yields silica aerogel with high pore size and pore volume, twice of that aged in ethanol at room temperature. High aging temperature and pressure can promote the dissolution and reprecipitation process of silica and the esterification process of silanols, which will enhance the backbone strength of silica gel, and hence produce silica aerogel with low bulk density, good monolithic performance and hydrophobic features. While the latter aging method produces silica aerogel with high bulk density and cracking appearance.     

Phase evolution of tantalum nitride and tantalum carbide films with PBII parameters

Tantalum nitride and tantalum carbide films were fabricated using magnetron sputtering of tantalum followed by nitrogen and carbon plasma-based ion implantation (N-PBII and C-PBII). The phase evolution and morphology of the films were studied using glancing angle X-ray diffraction (GXRD) and transmission electron microscopy (TEM). It was found that the main phase in the tantalum nitride films was crystalline TaN_0.1 whose grain size increases with increasing implantation voltage and phase content increases with increasing implantation dose. In the tantalum carbide film, the main phase was Ta₂C. TaC phase also appeared as the implantation dose increased. XRD results from various glancing angles show that the phases with high nitrogen or carbon content, Ta₄N₅ and TaC, are present in the surface of the films. X-ray photoelectron spectra (XPS) from the tantalum carbide film reveal that the surface carbon content is higher than that of the inner film.     

Comparison of Nb- and Ta-effectiveness for improvement of the cyclic oxidation resistance of TiAl-based intermetallics

High-temperature cyclic oxidation resistance of Ti–45.2Al–7.2Nb and Ti–44.8Al–6.6Ta (in at.%) alloys is studied. The alloys were oxidized at 800–1000 °C for up to 380 h and oxidation kinetics was expressed as a function of weight gain versus time. Both as-cast and oxidized alloys were examined by optical and scanning electron microscopy, energy- and wave-dispersion spectrometry, X-ray diffraction and X-ray fluorescence spectrometry. In contrast to previously reported studies, tantalum is found to retard oxidation more effectively than niobium, despite its lower content in the investigated alloy. It also shows a significantly better adherence of oxide scales to the substrate, i.e. a lower tendency to scale spallation, particularly at 1000 °C. Chemical and phase analysis of oxidized alloys reveals considerable differences in element and phase distribution in oxidation-affected zones: 1. Niobium is observed to increase alumina amount in scales more effectively than tantalum. 2. Concentration of tantalum in scales is lower than of niobium. 3. Tantalum causes the occurrence of nitrides both in scales and in metallic substrate, while niobium supports formation of nitrides only in metallic substrate beneath scales. Differences between the investigated alloys are discussed in relation to oxidation mechanism, stability of Ta- and Nb-containing compounds.     

SLM制备径向梯度多孔钛/钽及其表征研究

利用增材制造技术制作仿天然骨的径向梯度多孔钛/钽骨科植入物具有广阔的前景。基于三周期极小曲面（triply minimal surfaces,TPMS）建模法建立了平均孔隙率为70%的圆柱型径向梯度孔隙结构,孔隙率由中轴线（90%）向圆周面（30%）逐渐降低。利用激光选区熔化(Selected Laser Melting, SLM)工艺制作径向梯度多孔钛/钽。光学显微镜,扫描电镜,Micro-CT检测结果共同显示,SLM径向梯度多孔钛/钽的孔隙结构与设计特征一致。SLM工艺制作的径向梯度多孔钛/钽的孔隙率分别为73.18%与68.18%。力学测试结果表明,梯度多孔钛/钽的弹性模量分别为3.96±0.19GPa与3.47±0.25GPa,抗压强度分别为90.83±3.35MPa与93.27±1.24MPa。梯度多孔钛/钽的弹性模量与抗压强度分别显著高于均匀多孔钛/钽（孔隙率为70.11%的均匀多孔钛弹性模量为2.34±0.48GPa,抗压强度为67.63±1.33MPa,孔隙率为65.39%的均匀多孔钽弹性模量为1.69±0.49GPa,抗压强度为68.56±0.41MPa）。体外细胞相容性实验证明,径向梯度多孔钛/钽均具有良好的生物相容性,适合间充质干细胞与肌肉细胞的粘附生长。SLM工艺制作的径向梯度多孔钛/钽比均匀多孔钛/钽具有与天然骨组织更相近的结构与性能,是理想的骨缺损修复替代物。     

Phase formation,structure, and state of stress of nanostructured tantalum boride films

Nanostructured tantalum boride films have been synthesized using the method of nonreactive radio-frequency sputtering of TaB₂ target. The effect of sputtering regimes on the phase formation, structure, and the state of stress of the samples produced has been studied. The thickness of films was determined by multibeam interferometry and X-ray diffraction methods; the structure and phase composition of films were studied by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy; and the chemical composition was determined by the secondary ion mass spectrometry. The change in the sputtering regimes affected the phase formation and the structure of the synthesized films and led to changes in their substructural parameters, namely, subgrain sizes, microdeformations of the crystal lattice, and the degree of texture and the level of macrostresses. Both textured stressed and nontextured stressless nanostructured films of tantalum borides have been obtained.