Microwave-Assisted Sol-Gel Synthesis of Silica Nanoparticles Using Rice Husk as a Precursor for Corrosion Protection Application

Silicon - Silica nanoparticles are received significant interest for novel applications owing to inherent characteristics such as porous, resistance to most corrosive conditions, non-toxicity, and...     

Production of NiO,NiO/Ag,NiO/Au,and NiO/Pt hollow spheres by using block copolymer stabilized microspheres as a template

Hollow spheres of nickel oxide (NiO) and silver, gold, and platinum nanoparticle loaded NiO composites were successfully produced by using polystyrene (PS) latexes as hard template. Due to the presence of tertiary amine based diblock copolymer stabilizer on the surface of PS, the tertiary amine functional groups provided homogene deposition of nickel hydroxide, and then the precursor NiO salt production on the surface of PS latexes with a controlled precipitation technique. Then, NiO and NiO/metal NP hollow spheres were produced by calcination at 600 °C. Thermogravimetric analysis indicated that the amounts of NiO and NiO-composite after calcination were in the range of 21.1–29.7 wt%. The diameters of metal oxide spheres were in the range of 2.0–2.7 μm and the shell thickness were in the range of 250–350 nm. These structures had very low densities due to their porous and hollow structures and had outer layers with highly rough surfaces due to formation of nanosheets, which may offer important advantages for catalysis studies.     

Synthesis and characterization of polyaniline/NiO nanocomposite

Spherical nickel oxide (NiO) nanoparticles were prepared by using nickel chloride as precursor in the ethylene glycol as solvent and urea as precipitant. The X‐ray diffraction study showed that NiO has single‐phase cubic structure with average crystallite size of 35 nm. The prepared NiO nanoparticles were incorporated into polyaniline (PANI) matrix during in situ chemical oxidative polymerization of aniline with different molar ratios of aniline: NiO (12 : 1, 6 : 1, and 3 : 1) at 5°C using (NH₄)₂S₂O₈ as oxidant in aqueous solution of sodium dodecylbenzene sulfonic acid, as surfactant and dopant under N₂ atmosphere. The synthesized composites have been characterized by means of X‐ray diffraction (XRD), thermogravimetric analysis, Fourier transform infrared (FTIR), scanning electron microscopy, TEM, and vibrating sample magnetometer for its structural, thermal, morphological, and magnetic investigation. The XRD and FTIR studies show that the NiO particles are in the composite. The room temperature conductivities of the synthesized PANI, PANI/NiO (12 : 1), (6 : 1), and (3 : 1) composites were found to be 3.26 × 10^?4, 1.88 × 10^?4, 1.5 × 10^?4, and 4.61 × 10^?4 S/cm, respectively. The coercivity (H_c) and remnant magnetization (M_r) of NiO, PANI/NiO NCs (12 : 1), (6 : 1), and (3 : 1) at 5 K was found to be 8.22 × 10^?2, 6.31 × 10^?2, 6.42 × 10^?2, 6.27 × 10^?2 T, and 6.64 × 10^?3, 1.83 × 10^?4, 3.07 × 10^?4, and 3.98 × 10^?4 emu/g, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

非水解溶胶-凝胶过程制备锡/硅复合氧化物

以无水四氯化锡和正硅酸乙酯为前驱物、环己烷为溶剂,在无氧无水条件下采用非水解溶胶-凝胶过程制备了锡/硅复合氧化物,并对其进行了表征分析。结果表明,在原料Sn/Si摩尔比为1∶2、反应温度为30℃、焙烧温度为500℃时,所得复合氧化物的产率为31.3%,Sn/Si摩尔比为7.4∶1,粒径10nm左右,比表面积22.58cm2.g-1,平均孔径14.3nm,比孔容0.047cm3.g-1,主要为颗粒堆积孔;复合氧化物的主要组成为无定形氧化硅和氧化锡晶体,在焙烧温度达到500～600℃时仍有Sn-O-Si杂键存在。     

Ru/MgO Sol-Gel Prepared Catalysts for Ammonia Synthesis

A new method of preparation of alkali-promoted Ru/MgO catalysts, based on a sol-gel procedure, starting from magnesium ethoxide, Ru₃(CO)₁₂ and a cesium compound has been designed. The gels were subjected to an activation/reduction procedure to substantially obtain Ru-CsOH/MgO. The activated catalysts were tested in ammonia synthesis at atmospheric pressure. It was clear that the sol-gel prepared Cs-promoted Ru/MgO catalysts are much more active, under the same reaction conditions, than the analogous catalysts prepared by impregnation procedures.     

Electrochromic properties of porous NiO thin film as a counter electrode for NiO/WO3 complementary electrochromic window

Highly porous nickel oxide (NiO) thin films were prepared on ITO glass by chemical bath deposition (CBD) method. SEM results show that the as-deposited NiO film is constructed by many interconnected nanoflakes with a thickness of about 20 nm. The electrochromic properties of the NiO film were investigated in a nonaqueous LiClO₄–PC electrolyte by means of optical transmittance, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The NiO film exhibits a noticeable electrochromic performance with a variation of transmittance up to 38.6% at 550 nm. The CV and EIS measurements reveal that the NiO film has high electrochemical reaction activity and reversibility due to its highly porous structure. The electrochromic (EC) window based on complementary WO₃/NiO structure shows an optical modulation of 83.7% at 550 nm, much higher than that of single WO₃ film (65.5% at 550 nm). The response time of the EC widow is found to be about 1.76 s for coloration and 1.54 s for bleaching, respectively. These advantages such as large optical modulation, fast switch speed and excellent cycle durability make it attractive for a practical application.     

Synthesis of Mesoporous Silica Materials with Hydroxyacetic Acid Derivatives as Templates via a Sol-Gel Process

A series of mesoporous silica materials were synthesized via HCl-catalyzed sol-gel process of tetraethyl orthosilicate at 60°C in the presence of nonsurfactant compounds such as hydroxyacetic acid (HA), lactic acid (LAC), 2-hydroxyisobutyric acid (HIBA) and diphenylglycolic acid (DPGA) as templates or pore-forming agents. After the removal of the nonsurfactant template compounds from the template-containing SiO₂ composite, mesoporous silica materials were obtained. Results from Brunauer–Emmett–Teller (BET), powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) experiments identified the formation of mesopores. Nitrogen adsorption-desorption isotherms showed that pore parameters increased with the template concentration except for the DPGA system. However, the pore parameters did not simply increase with the size of the template molecules. These results revealed that the molecular structure, molecular affinity, number of hydrophobic groups and steric hindrance played a significant role on the pore size of the final materials.     

Sol-Gel Synthesis of Lithium Aluminate

LiAlO₂ was prepared by two sol-gel methods using simultaneous hydrolysis of the reagents: aluminum sec -butoxide/ lithium methoxide and aluminum sec -butoxide/LiOH. The resulting ceramic powders were compared with those prepared by two conventional methods (i.e., solid-state fusion and peroxide). The sol-gel method provided powders with a very high γ-LiAlO₂ content after calcining at temperatures as low as 700°C when LiOH was used. The solids were characterized by AAS, DTA, TGA, XRD, and SEM.     

Synthesis of Nd:YVO4 Thin Films by a Sol-Gel Method

Nd: YVO₄ powders and thin films were successfuly synthesized by the sol–gel method using metal alkoxides. A homogeneous and stable solution was prepared by the reaction of Y(OEt)₃, VO(O i Pr)₃, and Nd(OEt)₃ in 2-methoxyethanol. The precursor was a mixture of vanadium and yttrium double alkoxide. Precursor films were prepared by dip coating and crystallization to single-phase YVO₄ at 500°C. Nd:YVO₄ films were crystallized with (200) preferred orientation on glass substrates, which showed the characteristic optical absorption of neodymium.     

溶胶-凝胶法制备SiO2/有机硅复合涂料

以正硅酸乙酯(tetraethoxysilane,TEOS)、甲基三乙氧基硅烷、二甲基二乙氧基硅烷和甲基丙烯酰氧基丙基三甲氧基硅烷为原料,采用溶胶–凝胶法在聚碳酸酯(polycarbonate,PC)表面上制备透明硬质的SiO2/有机硅复合涂膜。用红外光谱、紫外光谱,热重、X射线衍射、表面扫描电镜、原子力显微镜和接触角测量仪等方法对产物进行了表征。结果表明:复合膜中形成了Si—O—Si网络结构;采用浸涂工艺,经120℃热固化制备的涂膜厚度为0.84μm,表面平整,致密均质,对PC基材具有一定的增透作用(透光率提高了将近5%);复合膜对水的接触角随固化时间的延长而增大,在120℃固化3 h后接触角为93°;随着TEOS含量增加,复合膜的耐热性得到提高;当SiO2/有机硅复合树脂的n(R)/n(Si)(一个硅原子上平均连结的有机基团数目)值选择0.78,划格法测定的复合膜的铅笔硬度为2 H,附着力为0级。     

Synthesis of highly conductive PPy/graphene nanosheets/NiO composite using ultrasonic technique

Highly conductive polypyrrole/graphene nanosheets/NiO (PPy/GNS/NiO) composites are fabricated via ultrasound technique using p‐toluenesulfonic acid as a dopant and FeCl₃ as an oxidant. The effects of the GNS and NiO loading on the electrical conductivity are investigated. The maximum conductivity of PPy/GNS/NiO composites about 24.39 S/cm found with 3 wt% GNS and 48.7 wt% NiO at room temperature. The results showed that the high‐aspect‐ratio structure of GNS played an important role in forming a conducting network in PPy matrix. The microstructures of PPy/GNS/NiO are evidenced by the scanning electron microscope and transmission electron microscope examinations. The cyclic voltammetry curves can be seen that the PPy/GNS/NiO composites also have good electrochemical performance, and it can be used as a supercapacitor electrode material. POLYM. COMPOS., 34:997–1002, 2013. © 2013 Society of Plastics Engineers     

The Properties and Preparation of Chitosan/Silica Hybrids Using Sol-Gel Process

Chitosan/silica hybrids (Chitosan/SiO₂) using a sol-gel process were prepared at a wide range of in situ silica content from 0% to 100%. This work was undertaken to investigate the thermal properties, optical, adsorption, and biodegradability properties of this type of hybrid. Fourier transform infrared (FTIR) spectra were recorded to depict the interfacial interaction. Thermogravimetric analysis was used to determine the actual silica content forming in the hybrids and to evaluate the enhanced heat resistance of hybrids resulting from silica. Crystallography was illustrated using an X-ray diffractometer. Fracture surface was revealed through a scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) to probe the dispersion degree of SiO₂, which in turn confirmed the results of optical property on the formation of nanocomposites. To prevent the dissolution of chitosan and silica in the acid and alkaline solution, respectively, all prepared hybrids are capable of chelating Cu (II) as well as Fe (III) in a large degree. In addition, the hybrids are biodegradable based on the lysozyme treatment. Thus, chitosan/silica hybrids are of benefit as suitable environmental biomaterials and adsorbents under a wide range of conditions.     

Synthesis of La-doped NiO nanofibers and their electrochemical properties as electrode for supercapacitors

La-doped NiO nanofibers were synthesized by the electrospinning method. The X-ray diffraction (XRD) pattern showed that La doping does not change the crystal structure up to the doping ratio of La/Ni=1.5%. Electrochemical properties of La-doped NiO nanofibers were investigated using cyclic voltammetry and galvanostatic charge/discharge. The results showed that the La doping can enhance the charge/discharge specific capacitance and electrochemical stability of the NiO nanofibers. Especially, the sample with doping ratio of La/Ni=1.5% could reach a discharge specific capacitance of 94.85 F g⁻¹ at a constant current density of 5 mA cm⁻².     

Synthesis and Characterization of NiO Nano‐Spheres by Templating on Chitosan as a Green Precursor

In this study, nickel oxide was prepared through the calcination of extrusion dripped chitosan/nickel nitrate beads. The morphology and structural properties of the products were studied using various characterization techniques. Uniformly distributed nickel oxide was formed as observed from the studies of surface morphology where the processing parameters play a huge role on the resulting morphology. TEM results have shown that nickel oxide with crystallite sizes of 10–30 nm was obtained. The Fourier‐transform infrared spectra studies show an intense peak at 525 cm^?1, which is attributed to the vibration of Ni–O bond. Furthermore, the XRD results show NiO diffraction peaks correspond to (111), (200), (220), (311), and (222) which indicates that a bunsenite structure with a face‐centered cubic phase was produced in this study. The usage of 500°C as the lower limit in this study is justified due to the complete removal of the templating material as seen in the thermalgravimetric analysis studies. Furthermore, it was obtained that the largest surface area of nickel oxide synthesized using this technique is 48.024 m²/g with pore sizes of 19.843 nm. The usage of chitosan as a green template for the synthesis of nanoparticles has shown promising results which allows a more economical and sustainable approach for the fabrication of nanomaterials.     

Synthesis and characterization of NiO and Ni nanoparticles using nanocrystalline cellulose (NCC) as a template

In this study, nanosized nickel oxide (NiO) and nickel (Ni) powders were synthesised via glycine-nitrate (GN) combustion process, assisted by nanocrystalline cellulose (NCC) as a template. Despite the unique morphology of NCC, it has yet to be applied as a sacrificial bio-template for GN combustion process. In addition, NiO and Ni nanoparticles were obtained at relatively low temperatures in this study, whereby the calcination temperatures were varied from 400 °C to 600 °C, with calcination durations of 2, 4, and 6 h. The morphological analysis of the resulting products were conducted using FESEM, which showed uniformly dispersed NiO and Ni particles with average crystallite size of 25 nm and 27 nm, respectively. These results were confirmed using X-ray diffraction (XRD) technique. The Raman and Fourier transform infrared (FTIR) spectra revealed that the molecular fingerprints of the samples were in agreement with each other. Further analyses revealed that samples calcined at 600 °C for 4 h showed the lowest particle size for pure NiO, whereas the lowest particle size for pure Ni was obtained at 400 °C for 4 h. The TGA results were also consistent with the XRD analysis, whereby pure Ni was initially formed and upon heating, had gradually converted into NiO.     

Sol-Gel Synthesis of a New Oxide-Ion Conductor Sr- and Mg-Doped LaGaO3 Perovskite

Sr- and Mg-doped LaGaO₃ powders were prepared from a salt acetate solution. The stable solution was peptized by reacting ammonium hydroxide with the precursor solution. Thermal analysis (DTA/TGA) was used to characterize first the dehydration and then the thermal decomposition of the organic ligands of the dried gel. The transformation from amorphous powders into a crystallized, homogeneous oxide phase corresponds to two endothermic peaks in the DTA curve; the first one at 150°C is related to the removal of water and is followed by a shoulder at 250°C. The second peak at 300°C corresponds to a superposition of two decomposition reactions: acetate salt into its oxycarbonate and this oxycarbonate into its oxide. Two subsequent exothermic peaks correspond to oxidation of evolved gases such as methane, hydrogen, and carbon monoxide. TEM observations show an average 10 nm particle size of the LaGaO₃powder after annealing at 600°C. X-ray diffraction patterns indicate a pure primitive-cubic phase is formed by 1300°C without formation of any SrLaGaO₃ impurity. The impedance spectroscopy on a 93%-dense sample exhibits no grain-boundary contribution and an ac conductivity σ= 0.11 Ω⁻¹·cm⁻¹ at 800°C.     

Synthesis of Nd/Si Codoped YAG Powders via a Solvothermal Method

We report the synthesis of single-phased Nd/Si-doped yttrium aluminum garnet powder via a solvothermal method by using ethanol as the solvent. The obtained powder exhibits a spherical shape, no agglomeration, and an average particle size of ∼300 nm, suitable for conventional powder processing. The effect of heat treatment on the lattice parameter and optical properties of the powder is also studied. The results are discussed in terms of Nd/Si solubility.     

非水解溶胶-凝胶过程制备锡硅复合氧化物

以无水四氯化锡为锡源、正硅酸乙酯(TEOS)为硅源和氧供体、二氯甲烷为溶剂、无水三氯化铁为催化剂,通过非水解溶胶-凝胶过程制备锡硅复合氧化物材料;采用N2物理吸附、X-射线粉末衍射、傅立叶变换红外光谱等手段对锡硅复合氧化物材料进行表征。结果表明:与以环己烷为溶剂制备的锡硅复合氧化物材料相比,以二氯甲烷为溶剂制备的锡硅复合氧化物材料的比表面积和孔容明显增大,平均孔径明显减小,产率从31%提高到60%左右;催化剂无水三氯化铁的引入促进了Sn-O-Si键的形成,有利于产物的过饱和析出,制备的材料具有较大的比表面积(305.7m2·g-1),氧化锡以四方金红石结构分散在无定型态的氧化硅中。     

石墨烯/硅负极材料的制备及其电化学性能的研究

通过将亚微米硅与石墨烯进行原位还原复合(SG1)和机械混合(SG2)这2种方式制备了不同的石墨烯/硅复合锂离子电池负极材料。SEM结果显示,2种复合物中硅颗粒都被石墨烯片层所包夹,且分散均匀;充放电测试表明,这2种复合方式均使复合电极的首次容量损失大大减小,循环稳定性得到很大提高,其首次放电比容量分别为2 070.5mAh/g和1 534.2mAh/g,循环12次后均保持在1 000mAh/g以上;通过EIS阻抗谱对硅复合电极的导电性以及电极结构的初步研究,发现复合电极本身导电性以及材料的电接触性远优于纯硅,电极结构也相对稳定。     

氧化锡催化合成尼泊金戊酯

以对羟基苯甲酸和戊醇为原料,氧化锡为催化剂,甲苯为带水剂,合成了尼泊金戊酯,探讨了最佳反应条件,酯收率可达到90％,具有一定的应用价值。