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纳米TiO2/SiO2复合食品抗菌材料 总被引:7,自引:1,他引:7
《精细化工》2001,18(12):703-706
以水玻璃和Ti(SO4)2为原料,制备出了多孔的纳米TiO2/SiO2复合粒子,在后处理过程中,利用无机包覆剂溶解度随温度的变化,在复合粒子表面包覆了一层无机结晶膜,经热处理除去包覆剂后,得到了以单分散纳米复合粒子组成的复合微粉.对复合微粉进行比表面和孔容测试,并运用XRD和TEM进行了表征,发现TiO2以12.6nm的纳米晶粒的形式被多孔的SiO2包覆,所形成的复合粒子则约为20nm.为了了解复合微粒的灭菌效果,运用纳米TiO2和复合粉末对4种保健食品进行对照灭菌实验,两个月以后,测得含复合微粒的样品中的菌落总数为50~120个/g,是相应保健食品企业标准许可菌落数的0.25%~0.7%,为相应空白样和纳米TiO2粉样品菌落数的0.52%~0.97%和33.3%~83.3%. 相似文献
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Removal of elemental mercury from simulated coal-combustion flue gas using a SiO2–TiO2 nanocomposite
A novel silica–titania (SiO2–TiO2) nanocomposite has been developed to effectively capture elemental mercury (Hg0) under UV irradiation. Previous studies under room conditions showed over 99% Hg0 removal efficiency using this nanocomposite. In this work, the performance of the nanocomposite on Hg0 removal was tested in simulated coal-fired power plant flue gas, where water vapor concentration is much higher and various acid gases, such as HCl, SO2, and NOx, are present. Experiments were carried out in a fix-bed reactor operated at 135 °C with a baseline gas mixture containing 4% O2, 12% CO2, and 8% H2O balanced with N2. Results of Hg speciation data at the reactor outlet demonstrated that Hg0 was photocatalytically oxidized and captured on the nanocomposite. The removal efficiency of Hg0 was found to be significantly affected by the flue gas components. Increased water vapor concentration inhibited Hg0 capture, due to the competitive adsorption of water vapor. Both HCl and SO2 promoted the oxidation of Hg0 to Hg(II), resulting in higher removal efficiencies. NO was found to have a dramatic inhibitory effect on Hg0 removal, very likely due to the scavenging of hydroxyl radicals by NO. The effect of NO2 was found to be insignificant. Hg removal in flue gases simulating low rank coal combustion products was found to be less than that from high rank coals, possibly due to the higher H2O concentration and lower HCl and SO2 concentrations of the low rank coals. It is essential, however, to minimize the adverse effect of NO to improve the overall performance of the SiO2–TiO2 nanocomposite. 相似文献
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A glass/ceramic composite using lead-free low melting glass (SiO2B2O3CaOMgO glass) with Al2O3 fillers was investigated. X-ray diffraction analysis revealed that the anorthite and cordierite phase appeared in the sintered composites. The dilatometric analysis showed that the onset of shrinkage took place at ∼624 °C for all the samples and the onset temperature was independent on the content of glass. The low melting glass significantly promoted densification of the composites and lowered the sintering temperature to ∼875 °C. The addition of 50 wt% glass sintered at 875 °C showed εr of 7.3, tan δ of 1.15×10−3, TEC of 5.41 ppm/°C, thermal conductivity of 3.56 W/m °C, and flexural strength of 184 MPa. The results showed that the SiO2B2O3CaOMgO glass/Al2O3 composites were strong potential candidates for low temperature cofired ceramic substrate applications. 相似文献
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以Na2SiO3为原料,采用非均匀成核法在纳米TiO2基体上制备了SiO2表面保护膜层,通过红外光谱、X射线光电子能谱、扫描电镜、粒径测量、BET比表面积测量分析,证实纳米TiO2颗粒表面包覆了一层均匀致密的SiO2纳米膜,而且两者是以化学键合方式结合在一起。分散性能测试表明:纳米SiO2/TiO2复合粉体的分散性能明显提高。 相似文献
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采用四硼酸锂熔融试样,电感耦合等离子体原子发射光谱法(ICP-AES法)测定矾土中Fe2 O3、TiO2和SiO2。通过对熔样方法选择、铝基体以及背景的研究,确定了分析条件。结果表明,该法具有良好的精密度和准确性,回收率在94%~108%。 相似文献
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以无机物聚合硅酸为硅源、硫酸钛为钛源,采用微乳液法制备了SiO2/TiO2复合光催化剂,考察了制备条件对SiO2/TiO2光催化活性的影响,并利用SEM、FTIR、XRD和BET等技术手段对光催化剂进行了表征。结果证明,SiO2和TiO2颗粒之间存在着强的相互作用,形成了Ti-O-Si键,从而抑制了TiO2粒径的增大,延缓了TiO2由锐钛矿相向金红石相的转变。对甲基橙等染料的光催化降解实验结果表明,SiO2/TiO2的光催化活性并非随着TiO2的含量增加而提高,当硅与钛物质的量比为1∶1并在160℃的温度下水热合成2.5 h时,SiO2/TiO2光催化剂在紫外光照15 min后对甲基橙的脱色率为85.5%,与同等条件下制备的TiO2相比具有更好的光催化活性和更大的比表面积。 相似文献
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Sukamon Hinchiranan Yi Zhang Satoshi Nagamori Tharapong Vitidsant Noritatsu Tsubaki 《Fuel Processing Technology》2008
The addition of small amount of TiO2 to silica-supported cobalt catalysts significantly increasing the dispersion of cobalt and Co metallic surface area resulting in the remarkable enhancement of the Fisher–Tropsch synthesis (FTS) activity in the slurry-phase reaction. The addition of TiO2 adjusted the interaction between cobalt and silica support quite well to realize the favorite dispersion and reduction degree of supported cobalt, leading to high catalytic activity in FTS. The properties of various catalysts were characterized by in-situ DRIFT, XRD, TPR, N2 physisorption and H2 chemisorption. 相似文献
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An experimental strategy was developed to obtain Si–Ti–Zr transparent sols via the sol-gel process. The chelating agents isoeugenol (2-methoxy-4-propenylphenol, isoH), salicylaldehyde (2-hydroxybenzaldehyde, salH), and itaconic anhydride (2-methylenesuccinic anhydride, anhH) were employed separately to stabilize monomeric Ti and Zr precursors, in order to control their chemical reactivity, avoiding precipitation. In all cases a prehydrolyzed tetraethyl orthosilicate (TEOS) sol was the Si source. The sols were polymerized at room temperature (293 K) to obtain gels and these were dried and calcined at 873 K in air. The radial distribution functions (RDF) of the gels were obtained at room temperature. The solids were studied by scanning electron microscopy (SEM). The porosity and surface area of solids were determined by N2 adsorption. The surface area results obtained range between 83–198 m2/g. The average pore diameters are 1.44–1.61 nm. 相似文献
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Optical and photoelectrochemical (PEC) properties of a TiO2 thin film electrode doped with a new variation of ruthenium–(4,4′dimethyl-2,2′-bipyridine)–isothiocyanato–tungsten[bis-(phenyl-1,2-ethilenodithiolenic)] bimetallic complex (BM) were investigated. Physical adsorption process was used to immobilise the BM on the TiO2 thin film. Crystalline structure and surface morphology of the thin films were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) techniques. N3 commercial dye was also used as a dopant to the TiO2 films for comparison. Light absorption spectra and bandgap energy of the thin films were determined using UV–vis spectroscopy. Light absorption of the TiO2 thin film doped with BM was better than the TiO2 doped with the N3 commercial dye. Band edges of the TiO2 thin film and the BM were determined via cyclic voltammetry (CV) measurements. Top-edge of the BM valence band (VB) was more positive than the bottom edge of the conduction band (CB) of the TiO2 film (vs. NHE). PEC analysis indicated that photocurrent of TiO2 doped with the BM electrode was higher than TiO2 doped with the N3 in the beginning of illumination process, but the performance was defeated after a while. Based on the optical properties and the PEC analyses, BM has potential to be used as dye sensitisers for a PEC cell. 相似文献
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Abdelkader Nebatti Christian Pflitsch Christopher Eckert Burak Atakan 《Progress in Organic Coatings》2010
A relatively new promising method for surface temperature measurement is the use of thermographic phosphors. For this application, the temperature-dependent luminescence properties of europium (III)-doped anatase (TiO2:Eu3+) thin films were studied. The films were prepared by the sol–gel method using dip coating. The structures and the morphology of the films were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Electron dispersive X-ray spectroscopy (EDX) was used to verify the europium concentration within the films. For using the films as temperature sensors the optical properties are the main concern. Therefore, the emission spectra of the films were measured after ultraviolet laser excitation (355 nm). They indicate that the red characteristic emission (617 nm) of TiO2:Eu3+ due to the 5D0 → 7F2 electric dipole transition is the strongest. The decay time constant of the exponential emission decay under UV excitation with a Nd:YAG laser (355 nm, f = 10 Hz) is strongly temperature dependent in the range from 200 °C up to 400 °C; making it useful for temperature evaluation. The temperature dependence was measured for the emission line at 617 nm; the results demonstrate that anatase doped europium (III) can be used as a thermographic phosphor. 相似文献
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Nasima Khatun Saurabh Tiwari Jayanti Lal Chuan-Ming Tseng Shun Wei Liu Sajal Biring Somaditya Sen 《Ceramics International》2018,44(18):22445-22455
Uncompensated Ga-V co-doped TiO2 samples have been prepared by modified sol-gel process. Inhibition of phase transition due to co-doping is confirmed by X-ray diffraction measurement. Activation of phase transition increases from 120?kJ/mol (x?=?0) to 240?kJ/mol (x?=?0.046) due to Ga-V incorporation. In anatase phase, lattice constant increases by the effect of Ga3+ interstitials. This results in inhibition of phase transition. Anatase phase becomes stable up to ~ 650?°C in co-doped sample whereas for pure TiO2 phase transition starts in between 450 and 500?°C. High-resolution transmission electron microscope image shows particle size decreases in anatase phase due to co-doping. Increasing strain due to Ga-V incorporation results in reducing crystallite size. Brunauer–Emmett–Teller analysis shows that surface increases from 4.55?m2/g (pure TiO2) to 96.53?m2/g (x?=?0.046) by Ga-V incorporation. In rutile phase, grain growth process is enhanced mainly due to the effect of Vanadium and particles show a rod-like structure with majority {110} facets. Bandgap decreases in both phases and reduced to visible light region. For charge balance in uncompensated Ga-V co-doped sample, structural distortion created in the lattice by combining effect of substitution, interstitials and oxygen vacancies, which results in stabilization of anatase phase and reducing of bandgap. 相似文献
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NiFe2O4纳米粒子做磁性载体,苯乙烯、正硅酸乙酯为原料,KH-570为交联剂,采用乳液聚合法制备了PS/SiO2/NiFe2O4磁性微球材料。以PS/SiO2/NiFe2O4磁性微球为核,十二烷基磺酸钠和聚乙烯吡咯烷酮作模板剂,钛酸丁酯做钛源,制备得到多层介孔复合微粒TiO2/SiO2/NiFe2O4。通过XRD、SEM对磁性复合微粒的结构进行了表征,结果表明,TiO2/SiO2/NiFe2O4是具有核壳结构的中空介孔微粒。采用矢量网络分析仪测试了NiFe2O4、SiO2/NiFe2O4、TiO2/NiFe2O4、TiO2/SiO2/NiFe2O4复合材料的微波电磁参数,SiO2、TiO2对磁性微粒的电磁参数有明显的改善,可较好的解决吸波涂层设计中的阻抗匹配问题。 相似文献
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通过溶胶-凝胶法在金红石型纳米二氧化钛(TiO2)表面包覆二氧化硅(SiO2)薄膜,对纳米TiO2进行表面改性。通过优化聚乙烯吡咯烷酮(PVP)用量、硅钛比、氨水的用量确定最佳制备条件为:TiO2用量为0.3 g,PVP用量为0.4 g,硅钛比为2∶1,氨水用量为5 m L,获得了粒径小,SiO2包覆层薄,单分散性好的SiO2-TiO2复合纳米粒子。应用FT-IR,XRD,SEM,TEM和UV-vis等对改性前后的粒子进行表征。结果表明:红外光谱图中出现Si-O-Ti键的振动吸收峰,改性前后的纳米TiO2均为金红石型,SEM及TEM显示改性后的粒子团聚现象减弱,其表面形成了约10 nm的SiO2薄膜。经过表面改性,SiO2成功包覆在纳米TiO2表面,复合纳米粒子的光催化活性得到有效抑制,纳米TiO2作为防晒剂的安全性大大提高。... 相似文献
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采用原位掺杂和物理吸附2种方法,成功制备了TiO2/SiO2复合载体载银抗菌粉体;系统考察了制备工艺、煅烧、掺锌等因素对复合载银抗菌粉体的影响。利用XRD、SEM等多种测试手段,对复合载银抗菌剂的白度、结构及形貌进行了表征;并以污水细菌为探针,考察了复合载体载银抗菌剂的抗菌性。结果表明:原位掺杂和物理吸附2种方法均能得到相同结构的复合载体载银抗菌剂,掺锌能有效增加载银抗菌剂样品的白度,提高抗菌剂的色泽稳定性;抗菌性能测试表明,复合载银粉体对污水细菌具有较强的抗菌效果,最小抗菌浓度为450 mg/L。 相似文献