多面体低聚倍半硅氧烷-ZrO2复合气凝胶的制备与表征

以官能团化的多面体低聚倍半硅氧烷（POSS-［C2H4Si(OEt)3］8）和正丁醇锆为原料,以乙醇作为溶剂,通过溶胶-凝胶及二氧化碳超临界干燥成功制备了三种不同锆含量POSS-ZrO2的复合气凝胶。并用傅里叶变换红外光谱分析仪（FTIR）、扫描电镜（SEM）、X射线衍射仪（XRD）和比表面吸附仪（BET）对其进行表征。结果表明：该气凝胶中有SiOZr键,并且所得气凝胶都是无定型的,其比表面积随着锆含量的增加而变小,最高可达491 m2/g,并且其孔径分布都比较广。     

氮掺杂碳气凝胶电极材料的制备及性能

以三聚氰胺（M）、间苯二酚（R）和甲醛（F）为原料,经溶胶-凝胶法、超临界干燥和高温碳化制备了系列的氮掺杂碳气凝胶（NCAs）。X射线光电子能谱(XPS)分析表明,氮元素成功地引入到碳气凝胶中,并且可以通过调节三聚氰胺掺杂量来控制氮掺杂量;扫描电子显微镜（SEM）和N2吸附测试显示出不同氮掺杂量的碳气凝胶的微观结构差异较大,随着氮含量的增加,比表面积有先减后增的趋势;在6 mol/L KOH溶液中进行的恒流充放电和循环伏安测试表明,引入氮元素能够极大地改善碳气凝胶的电化学性能,最高比电容量达176 Fg-1,并且凝胶具有良好的电容特性和可逆性。     

辐照还原法制备Au掺杂MF气凝胶

利用辐照还原法在500 kGy辐照剂量下制备了Au掺杂MF有机气凝胶。通过X射线衍射（XRD）、能量色散光谱仪（EDX）和透射电子显微镜（TEM）测试证实了辐照法成功地制备出Au掺杂MF有机气凝胶复合物。EDX和TEM照片表明辐照处理后Au纳米颗粒均匀地分布在MF气凝胶骨架中,并且Au纳米颗粒的平均尺寸为5.8 nm。N2吸附数据分析表明掺入Au纳米颗粒后,MF气凝胶的比表面积、总孔体积、微孔体积和介孔体积都有所下降。     

辐照还原法制备Au掺杂MF气凝胶

利用辐照还原法在500 kGy辐照剂量下制备了Au掺杂MF有机气凝胶。通过X射线衍射（XRD）、能量色散光谱仪（EDX）和透射电子显微镜（TEM）测试证实了辐照法成功地制备出Au掺杂MF有机气凝胶复合物。EDX和TEM照片表明辐照处理后Au纳米颗粒均匀地分布在MF气凝胶骨架中,并且Au纳米颗粒的平均尺寸为5.8 nm。N2吸附数据分析表明掺入Au纳米颗粒后,MF气凝胶的比表面积、总孔体积、微孔体积和介孔体积都有所下降。     

低密度Cu掺杂SiO2复合气凝胶的制备及表征

分别以正硅酸甲酯、醋酸铜为硅源和铜源,通过溶胶凝胶法及CO2超临界干燥技术制备了一系列Cu掺杂SiO2复合气凝胶。采用红外谱仪（FTIR）、扫描电镜（SEM）、X射线能谱仪（EDS）、比表面积和孔隙度分析仪（BET）、动态热机械分析仪（DMA）对样品进行了表征。结果表明随着铜含量的增加,复合气凝胶密度增加,比表面积降低,平均孔径增加,实际掺杂比与理论掺杂比对应增加。该复合气凝胶具有三维网状结构,密度低（＜40 mg/cm3）,比表面积高（＞390 m2/g）,成型性较好,有望应用于惯性约束聚变（ICF）实验。     

改性SiO2气凝胶制备及其在ICF实验中的应用

以正硅酸乙酯（TEOS）为前驱体,采用酸碱两步催化法制备了SiO2醇凝胶。醇凝胶分别经过TEOS母液、甲基三乙氧基硅烷（MTEOS）处理后,以六甲基二硅胺烷（HMDSA）为疏水改性试剂,制备了改性SiO2醇凝胶,醇凝胶经溶剂交换后以CO2作为干燥介质,采用超临界干燥法制备了密度在30～100 mg/cm3的SiO2气凝胶。用傅里叶变换红外光谱仪（FTIR）对疏水性SiO2气凝胶进行了研究。研究结果表明,经过改性的气凝胶在潮湿环境中具有极好的尺寸稳定性和疏水性。采用精密车床加工得到了满足惯性约束聚变（ICF）物理试验要求的微柱。     

镍掺杂三聚氰胺-甲醛气凝胶的浸渍-还原法制备

以PdCl2为活化敏化液,水合肼为还原剂,采用化学浸渍-还原法在常温下制得了磁性金属Ni掺杂三聚氰胺-甲醛（MF）气凝胶,为金属掺杂气凝胶的制备寻得了新的途径。利用X-射线粉末衍射仪（XRD）、扫描电镜（SEM）、透射电镜（TEM）等对Ni掺杂MF气凝胶进行表征,SEM和TEM均表明,经浸渍-还原处理后的MF气凝胶骨架中较均匀地分布着粒径约100 nm的金属Ni颗粒,其中部分颗粒生长连结形成较大团簇。N2吸-脱附实验数据显示,掺入金属Ni后,MF气凝胶的比表面积、总孔体积、微孔体积均减小,表明浸渍-还原处理后得到的金属Ni颗粒均匀分布于MF气凝胶孔隙中,其中少量大孔的出现是由形成团簇的Ni颗粒填充了部分纯MF气凝胶的孔隙撑开了孔隙结构所致。     

改性SiO2气凝胶制备及其在ICF实验中的应用

 以正硅酸乙酯（TEOS）为前驱体，采用酸碱两步催化法制备了SiO₂醇凝胶。醇凝胶分别经过TEOS母液、甲基三乙氧基硅烷（MTEOS）处理后，以六甲基二硅胺烷（HMDSA）为疏水改性试剂，制备了改性SiO₂醇凝胶，醇凝胶经溶剂交换后以CO₂作为干燥介质，采用超临界干燥法制备了密度在30～100 mg/cm³的SiO₂气凝胶。用傅里叶变换红外光谱仪（FTIR）对疏水性SiO₂气凝胶进行了研究。研究结果表明,经过改性的气凝胶在潮湿环境中具有极好的尺寸稳定性和疏水性。采用精密车床加工得到了满足惯性约束聚变（ICF）物理试验要求的微柱。     

辐射法制备Pd掺杂碳气凝胶粉末

利用辐射还原法,在100, 200, 500 kGy辐射剂量下制备了金属Pd掺杂的碳气凝胶粉末。X射线衍射（XRD）,扫描电子显微镜（SEM）和能谱测试证实了辐射法成功地制备出Pd掺杂的碳气凝胶粉末复合物。SEM照片表明,还原生成的金属Pd相对均匀地分布在所有碳气凝胶颗粒表面。N2吸附数据分析表明:掺入金属Pd后,碳气凝胶粉末比表面积、平均孔径和总孔体积都显著减小。由于被还原金属大多沉积在碳气凝胶粉末表面,不同辐射剂量下制得的掺杂碳气凝胶粉末的比表面积等多孔特征数据相差不大。     

辐射法制备Pd掺杂碳气凝胶粉末

利用辐射还原法,在100, 200, 500 kGy辐射剂量下制备了金属Pd掺杂的碳气凝胶粉末。X射线衍射（XRD）,扫描电子显微镜（SEM）和能谱测试证实了辐射法成功地制备出Pd掺杂的碳气凝胶粉末复合物。SEM照片表明,还原生成的金属Pd相对均匀地分布在所有碳气凝胶颗粒表面。N2吸附数据分析表明:掺入金属Pd后,碳气凝胶粉末比表面积、平均孔径和总孔体积都显著减小。由于被还原金属大多沉积在碳气凝胶粉末表面,不同辐射剂量下制得的掺杂碳气凝胶粉末的比表面积等多孔特征数据相差不大。     

Ultrasonic-induced synthesis of high surface area colloids CeO2–ZrO2

The nanostructures of high surface area ceria–zirconia colloids have been successfully synthesized via a sonochemical method in the presence of polyethylene glycol 600. Their structural characteristics have been investigated using powder XRD, FESEM, BET surface area, TG, and other techniques. The average size of CeO₂–ZrO₂ nanoparticles is estimated to be 3.7 nm using Debye–Scherrer’s equation. The BET analysis indicates that colloids CeO₂–ZrO₂ have a remarkably high surface area of 226 m² g⁻¹.     

Sono-assisted preparation of highly-efficient peroxidase-like Fe3O4 magnetic nanoparticles for catalytic removal of organic pollutants with H2O2

Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) with much improved peroxidase-like activity were successfully prepared through an advanced reverse co-precipitation method under the assistance of ultrasound irradiation. The characterizations with XRD, BET and SEM indicated that the ultrasound irradiation in the preparation induced the production of Fe₃O₄ MNPs possessing smaller particle sizes (16.5 nm), greater BET surface area (82.5 m² g^?1) and much higher dispersibility in water. The particle sizes, BET surface area, chemical composition and then catalytic property of the Fe₃O₄ MNPs could be tailored by adjusting the initial concentration of ammonia water and the molar ratio of Fe²⁺/Fe³⁺ during the preparation process. The H₂O₂-activating ability of Fe₃O₄ MNPs was evaluated by using Rhodamine B (RhB) as a model compound of organic pollutants to be degraded. At pH 5.4 and temperature 40 °C, the sonochemically synthesized Fe₃O₄ MNPs were observed to be able to activate H₂O₂ and remove ca. 90% of RhB (0.02 mmol L^?1) in 60 min with a apparent rate constant of 0.034 min^?1 for the RhB degradation, being 12.6 folds of that (0.0027 min^?1) over the Fe₃O₄ MNPs prepared via a conventional reverse co-precipitation method. The mechanisms of the peroxidase-like catalysis with Fe₃O₄ MNPs were discussed to develop more efficient novel catalysts.     

Surface modification of silica-coated zirconia by chemical treatments

Zirconia surface modification by various chemical treatments after silica coating by sandblasting was investigated in this study. The surface of silica-coated dental zirconia was hydroxylated by treatment with different acids at room temperature for 4 h, rinsed with deionized water and air-dried. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Shifts in binding energies for Zr 3d_5/2 and Si 2p peaks were observed after treatment with acids, thereby showing a change in the chemical states of zirconium and silicon on the surface layer of silica-coated zirconia. The XPS analysis revealed that the silica-coated zirconia (SiO₂-ZrO₂) surfaces had changed to hydrous silica-coated zirconia (SiO₂-ZrO₂·nH₂O). One-way ANOVA analysis revealed there was significant difference in both surface roughness parameters of silica-coated zirconia after chemical treatments and the surface topography varied depending on the acid treatment.     

Effect of the particle size on the electrochemical performance of nano-Li2FeSiO4/C composites

Nano-Li₂FeSiO₄/C composites were prepared from three kinds of nano-SiO₂ (their particle sizes are 15?±?5, 30?±?5, and 50?±?5 nm, respectively) by a traditional solid-state reaction method. The as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elementary analyzer, Brunauer–Emmett–Teller (BET) analysis, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. XRD results reveal that nano-Li₂FeSiO₄ composites fabricated from nano-SiO₂ (smaller than 30 nm) have less impurity. SEM results indicate that the particle size of nano-Li₂FeSiO₄ composites is nearly accord with the particle size of nano-SiO₂. BET analysis indicates that the specific surface areas of LFS15, LFS30, and LFS50 are 35.10, 35.27, and 26.68 m² g, respectively, and the main pore size distribution of LFS15, LFS30, and LFS50 are 1.5, 5.5, and 10 nm, respectively. Electrochemical measurements indicate that nano-Li₂FeSiO₄ composites prepared from nano-SiO₂ of 30?±?5 nm have the best electrochemical performance among the three samples.     

Optimised NASICON ceramics for Na+ sensing

NASICON dense ceramics were obtained from solid state reaction between SiO₂, Na₃PO₄·12H₂O and two different types of zirconia: monoclinic ZrO₂ and the yttria-doped tetragonal phase (ZrO₂)_0.97(Y₂O₃)_0.03. Higher temperatures were needed to obtain dense samples of the yttrium free composition (1265 °C). The electrical conductivity, at room temperature, of the yttria-doped samples sintered at 1230 °C (0.20 S/m) is significantly higher than the value obtained with the material prepared from pure ZrO₂. The impedance spectra show that the differences in conductivity are predominantly due to the higher grain boundary resistance of the undoped ceramics, probably due to formation of monoclinic zirconia and glassy phases along the grain boundary. Further improvement of the electrical conductivity could be achieved after optimization of the grain size and density of grain boundaries. A maximum conductivity value of about 0.27 S/m at room temperature was obtained with the yttria-doped samples sintered at 1220 °C for 40 h. Yttria-doped and undoped ceramics were tested as Na⁺ potentiometric sensors. The detection limit of the yttria-doped sample (10⁻⁴ mol/l) was one order of magnitude lower than the obtained with the undoped material. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16 – 22, 2001.     

Effect of annealing temperature on the photocatalytic activity of WO3 for O2 evolution

Commercial WO₃ powder was annealed in air at four different temperatures and characterized by XRD and BET. The samples were used for the photooxidation of H₂O to O₂ under visible light irradiation (λ > 420 nm) in the presence of IO₃⁻ and the evolved gases were analyzed by gas chromatography. The results showed that the WO₃ photocatalyst of monoclinic phase, which was obtained by annealing at 750 °C for 4 h, displayed the best activity in terms of O₂ evolution among all the samples. Moreover, the activity was also found to be slightly affected by the grain size of the WO₃ samples.     

Formation and characterization of boride coatings thermochemically grown on the Fe64Ni36 alloy

Zirconium oxide (zirconia) exists in three crystalline forms of monoclinic, tetragonal and cubic structures at atmospheric pressures. The cubic form of zirconia is well known for its mechanical, electrochemical and optical applications. Fe-doped cubic zirconia (high temperature phase) compositions are synthesized by microwave combustion method. Here, we present a Mössbauer investigation of Zr_1???x Fe _x O₂ composition within a range of Fe (0.03 < x < 0.09). ⁵⁷Fe Mössbauer spectra were recorded at room temperature and at low temperature (77 K) for all samples. 3% Fe-doped ZrO₂ shows doublet and the corresponding 6% and 9% Fe-doped ZrO₂ samples show superimposed sextet and doublets. The isomer shift and quadrupole moment indicate, Iron to be in III oxidation state and to occupy different octahedral sites, associated with some amount of disorder. X-ray powder diffraction pattern of Fe-doped ZrO₂ samples appear as very well crystalline. The Miller indices refer to the cubic fluorite-type ZrO₂ structure. The magnetic behavior shows increase in moment and decrease in coercivity, with increase in Fe concentration. The M vs. H plots of the as-prepared Zr_1-x Fe _x O₂ essentially show typical hysteresis loops, indicating room temperature ferromagnetism. Thus, the introduced microwave combustion route is an effective process to achieve multifunctional Fe-doped Zirconia with coexistent magnetic properties.     

Iron oxide nanoparticle synthesis in aqueous and membrane systems for oxidative degradation of trichloroethylene from water

The potential for using hydroxyl radical (OH^?) reactions catalyzed by iron oxide nanoparticles (NPs) to remediate toxic organic compounds was investigated. Iron oxide NPs were synthesized by controlled oxidation of iron NPs prior to their use for contaminant oxidation (by H₂O₂ addition) at near-neutral pH values. Cross-linked polyacrylic acid (PAA) functionalized polyvinylidene fluoride (PVDF) microfiltration membranes were prepared by in situ polymerization of acrylic acid inside the membrane pores. Iron and iron oxide NPs (80–100 nm) were directly synthesized in the polymer matrix of PAA/PVDF membranes, which prevented the agglomeration of particles and controlled the particle size. The conversion of iron to iron oxide in aqueous solution with air oxidation was studied based on X-ray diffraction, Mössbauer spectroscopy and BET surface area test methods. Trichloroethylene (TCE) was selected as the model contaminant because of its environmental importance. Degradations of TCE and H₂O₂ by NP surface generated OH^? were investigated. Depending on the ratio of iron and H₂O₂, TCE conversions as high as 100 % (with about 91 % dechlorination) were obtained. TCE dechlorination was also achieved in real groundwater samples with the reactive membranes.     

KDP晶体固-液界面吸附行为的分子模拟研究

通过构建晶体表面-KDP分子界面吸附结构模型, 采用分子动力学和密度泛函计算方法研究KDP分子在(001)和(010)面吸附的物理化学过程, 考察了温度对物理吸附行为的影响. 研究表明: KDP晶体表面的吸附过程和生长习性主要由化学吸附主导, 化学吸附能的计算表明[K-O₈]基元在(001)界面的结合能是(010)界面结合能的2.86倍; 在饱和温度附近, [H₂PO₄]^-阴离子在KDP界面的物理结合能随温度的变化呈现振荡特征, 溶液中有较多的离子团簇形成, 溶液变得很不稳定; 当温度从323 K降低至308 K时, 水分子在界面的结合能总体呈下降趋势, 而KDP分子在界面的吸附能总体呈上升趋势, 脱水过程是水分子和[H₂PO₄]^-阴离子在固液界面边界层竞争吸附的结果. 研究结果对确足晶体生长界面动力学过程发展和完善晶体生长理论有重要意义. 关键词： 分子动力学 双层结构模型 结合能