Ag-TiO2多孔薄膜及其非紫外光辐照下的超亲水特性

采用溶胶凝胶法，以钛酸丁酯为前驱体、硝酸银络合物为银源、聚乙二醇2000（PEG2000）作为结构导向剂，制备超亲水多孔Ag-TiO₂复合薄膜。用X射线衍射仪、X射线光电子能谱仪、扫描电镜、原子力显微镜表征薄膜晶相结构、化学成分以及表面形貌。根据静态水接触角、动态润湿时间、超亲水长效稳定性综合评价不同Ag含量及PEG2000添加量薄膜的超亲水性能。研究发现，掺杂Ag与PEG2000对薄膜在非紫外光下的超亲水特性具有协同作用，掺杂Ag明显提高薄膜动态润湿速度及可见光响应，表面粗糙多孔结构有利于避光条件下的长效超亲水特性。Ag含量10%、PEG2000掺杂量5%的Ag-TiO₂复合薄膜在自然光条件下已具备优良的超亲水性能；水滴0.2 s内即可在表面完全铺展到0°；避光条件下保存，超亲水时效性可达到30 d以上。在可见光活化下即可强化超亲水性能，具有良好的防雾效果。     

Thermally stable and photocatalytically active titania for ceramic surfaces

The most photocatalytically active titania modification anatase must be stabilised to achieve high photocatalytic activity in ceramic processes at temperatures above 1000 °C. Thermally stable TiO₂ powders were prepared by the addition of silica and boehmite nanoparticles and deposited on corundum substrates and lead-free glazes. The powders and coatings were fired at increasing temperatures, and stabilisation of the anatase phase was achieved up to 1200 °C. In general, thermal stability was found to be lower when coated on substrates compared to the powder alone, and the extent of reduction depended on the chemical composition of the substrate. Only a slight modification of the titania electronic structure was found, indicating only weak interactions between silica and titania. Based on these results it is possible to assume an amorphous silica and alumina shell encases the titania particles which prevents grain growth and the anatase to rutile phase transformation.     

Adhesion phenomena in (co)extrusion coating of paper and paperboard

In extrusion coating, the inadequate adhesion between the polymer coating and the fiber-based paper substrate (paper and paperboard) is both a common and a constant problem. The lack of adhesion between the printing ink, or glue, and the polymer coating is another area where adhesion improvement is needed. The common means of improving adhesion are flame, corona, and ozone treatments. A modem extrusion coating line is equipped with both a pretreatment and a post-treatment unit. From the work presented here, the following observations were made. The higher the applied corona power and the thicker the coating, the higher the surface energy and polarity of the low density polyethylene (PE-LD) surface. When a high corona power was applied to the coating, only the polar component of the surface energy was increased. The surface energy decreased sharply as a function of aging, but remained more or less constant after about 2 weeks' storage time. The contact angles of water on paper correlated well with the oxygen contents (determined by ESCA) and with the applied corona power. The polarities of both paper and paperboard increased as a function of the applied corona power. Corona pretreatment of paper and paperboard improved their adhesion to PE-LD remarkably. The adhesion of the polypropylene (PP) homopolymer is based more on mechanical interlocking than on interfacial bonding. On the other hand, the oxidizing pretreatments of the paper substrates significantly promoted the adhesion of the PP copolymer.     

The effect of argon shielding gas at plasma spray process on the structure and properties of MoSi2 coating

In this work, MoSi₂ powder was agglomerated for using it in atmospheric plasma spray (APS) process. MoSi₂ coatings were manufactured by APS and argon-shrouded plasma spray (ASPS) processes. Phase composition and structural properties of coatings were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Also, the mechanical properties of coatings (such as microhardness and adhesion strength) were evaluated. Using the ASPS method, the coatings were found to have a low porosity and highly homogeneous structure. In addition, the argon protection gas was used to prevent the oxidation of the powder. Finally, the ASPS method revealed better microhardness and bending strength results for the corresponding tests.     

改性纳米TiO_2对纸张涂料及涂布纸性能的影响

研究了改性纳米TiO2对纸张涂料流变行为和涂布纸性能的影响。研究发现,在同一剪切速率下,随着改性纳米TiO2用量的增加,纸张涂料的表观黏度逐渐增大,且含改性纳米TiO2的纸张涂料具有较高的弹性模量和黏性模量,相位角则较低;随着改性纳米TiO2的用量在0~10%范围内增加,涂布纸的光学性能和印刷适性持续改善,且涂层表面结构的SEM和AFM观察显示,含改性纳米TiO2的纸张涂层表面具有较优的微观孔隙结构。     

Use of catalytic reactions to probe Mg-Al mixed oxide surfaces

The atmospheric hydroformylations of ethylene and propylene were investigated over SiO₂-supported Rh₄(CO)₁₂, Co₂(CO)₈, Rh₂Co₂(CO)₁₂ and RhCo₃(CO)₁₂-derived catalysts. The bimetal cluster-derived catalysts showed excellent activities for the formation of oxygenates. In situ IR study on partially dehydroxylated SiO₂-supported RhCo₃(CO)₁₂ suggested that the bimetal cluster framework may be preserved after decarbonylation under H₂ at 623 K and may be recarbonylated at room temperature. A strong physisorption of RhCo₃ (CO)₁₂ on SiO₂ is proposed, due to a nucleophilic attack of surface oxygen on the Co atoms, which promotes a metal-support interaction and thus stabilizes the bimetal cluster framework. A subcarbonyl bimetal cluster is thought to be the actual catalytic species on the surface.     

The role of alkali promoters in Fischer-Tropsch synthesis on Ru/SiO2 surfaces

Cs-promoted Ru-Na/SiO₂ catalysts were characterized via¹H NMR spectroscopy. Contrary to the results of studies using single crystals, we did not find any evidence of a ruthenium-mediated electronic interaction between the alkali promoter and adsorbed hydrogen. The site blocking effects of the Cs promoter diminished after exposure to hydrogen for extended periods of times. This effect was partly reversible after thermal evacuation of the hydrogen. In the presence of Cs, the surface of the support was also modified; the intensity of the diamagnetic resonance in the spectrum (predominantly Si-OH) decreased, and an additional resonance appeared in the spectra. There is evidence that hydrogen spillover and hydrogen mobility were also restricted in the Na-Cs-promoted system.     

Determination of the promoting effect of nano SiO2 and H3PO4@nano SiO2 in the thiocyanation of N-containing aromatic compounds under solvent-free conditions

Silica nanoparticles/ammonium thiocyanate (nano SiO₂/NH₄SCN) and H₃PO₄ embedded on nano silica (H₃PO₄@nano SiO₂) in the presence of NH₄SCN were found to be effective systems for the thiocyanation of some arylamines and indoles to afford their corresponding thiocyanated adducts at 70°C under solvent-free conditions. The recovery and reusability of nano SiO₂ as a prompting system have been investigated. A simple procedure for the synthesis of H₃PO₄@nano SiO₂ has also been represented. In addition, a plausible mechanism of thiocyanation has also been suggested.     

Enhanced photocatalytic degradation of tetramethylammonium on silica-loaded titania

Photocatalytic degradation (PCD) of tetramethylammonium (TMA) in water was studied using both pure TiO₂ and silica-loaded TiO₂ (Si–TiO₂). Use of Si–TiO₂ catalyst prepared from commercial TiO₂ powder by a simple method developed in this work enhanced the PCD rate of TMA considerably. The Si/Ti atomic ratio of 18% was found to be an optimum in photoactivity and the calcined sample was more efficient than the uncalcined one. Several factors were noted to be responsible for the higher photoefficiency of Si–TiO₂ catalyst. Si–TiO₂ calcined at 700 °C did not show any sign of change in the crystalline structure from that of uncalcined pure TiO₂. The increased thermal stability of Si–TiO₂ enabled the bulk defects to be removed at high temperatures without forming the inactive rutile phase, which may partly contribute to the higher photoactivity. The most outstanding characteristics of Si–TiO₂ is its surface charge modification. Loading silica on to a titania surface made the surface charge highly negative, which was confirmed by zeta potential measurements. The enhanced electrostatic attraction of cationic TMA onto the negatively charged Si–TiO₂ surface seems to be the main reason for the enhanced photoactivity of Si–TiO₂. As a result of this surface charge change, the TMA PCD rate with Si–TiO₂ exhibited a maximum around pH 7 whereas the PCD with pure TiO₂ was minimized at pH 7. The X-ray photoelectron spectroscopic analysis showed the formation of SiO_x on the TiO₂ surface but the diffuse reflectance UV spectra indicated no significant difference in the band gap transition between pure TiO₂ and Si–TiO₂. In addition, the diffuse reflectance IR spectra showed the presence of more surface OH groups on Si–TiO₂ than on pure TiO₂, which may also contribute to the higher photoactivity of Si–TiO₂ through generating more OH radicals upon UV illumination.     

Super-hydrophilic coatings based on silica nanoparticles

This work focuses on the use of silica nanoparticles for producing durable, transparent, and super-hydrophilic coatings on painted surfaces. Two methods were studied in detail: bottom-up approach using layer-by-layer (LbL) assemblies of hydroxylated SiO₂ nanoparticles, and top-down approach based on hybrid polymer/silica nanoparticles coatings. Of the two approaches studied, only the hybrid polymer/SiO₂ nanocomposite coatings containing 50–90%wt. SiO₂ exhibited durable super-hydrophilic surface properties less than 5° water contact and sliding angles. In the latter case, a unique micrometer-sized cracking pattern was developed. The LbL-assembled SiO₂ coatings showed a gradual degradation over time from the initial super-hydrophilic properties, indicated by the increase of the contact angles from less than 5^o to greater than 30^o after accelerated aging. To investigate the effect of environmental exposure on developing hydrophilicity, a variety of analytical methods were employed such as: atomic force microscopy, scanning electron microscopy, optical microscopy, and Fourier transform infrared. Experimental results and associated modeling indicated that the combination of micro- and nano-surface roughness and the surface chemical composition were the dominant factors affecting the durability of the hydrophilic attributes of the coatings containing silica nanoparticles.     

Effect of the metal oxide loading on the activity of silica supported MoO3 and V2O5 catalysts in the selective partial oxidation of methane

Precipitated silica catalysts loaded with either MoO₃ (0.2–4.0 wt%) or V₂O₅ (0.2–5.3 wt%) have been studied in the selective partial oxidation of methane to formaldehyde with molecular oxygen at 520 °C. The functionality of the SiO₂ surface towards the formation of HCHO is significantly promoted by V₂O₅, while it is depressed by the MoO₃.     

Influence of argon plasma on the deposition of Al2O3 film onto the PET surfaces by atomic layer deposition

In this paper, polyethyleneterephthalate (PET) films with and without plasma pretreatment were modified by atomic layer deposition (ALD) and plasma-assisted atomic layer deposition (PA-ALD). It demonstrates that the Al₂O₃ films are successfully deposited onto the surface of PET films. The cracks formed on the deposited Al₂O₃ films in the ALD, plasma pretreated ALD, and PA-ALD were attributed to the energetic ion bombardment in plasmas. The surface wettability in terms of water contact angle shows that the deposited Al₂O₃ layer can enhance the wetting property of modified PET surface. Further characterizations of the Al₂O₃ films suggest that the elevated density of hydroxyl -OH group improve the initial growth of ALD deposition. Chemical composition of the Al₂O₃-coated PET film was characterized by X-ray photoelectron spectroscopy, which shows that the content of C 1s reduces with the growing of O 1s in the Al₂O₃-coated PET films, and the introduction of plasma in the ALD process helps the normal growth of Al₂O₃ on PET in PA-ALD.     

Preparation of highly stable superhydrophobic TiO2 surfaces with completely suppressed photocatalytic activity

TiO₂ nanoparticles with a mean size of 20–30 nm were covered by ultrathin polydimethylsiloxane (PDMS) film, which shows hydrophobic properties. Surfaces consisting of the PDMS-coated TiO₂ particles showed water contact angles close to 170°. In contrast to the hydrophobic films consisting of organic molecules, which can be photocatalytically decomposed on TiO₂ in the presence of UV light, PDMS-coating on TiO₂ was highly stable. The PDMS-coating completely suppressed the photocatalytic activity of TiO₂. The unique properties of PDMS-coating can be exploited for UV protection layer and self-cleaning surfaces.     

X-ray photoelectron spectroscopy of the cement clinker phases tricalcium silicate and β-dicalcium silicate

We have used X-ray photoelectron spectroscopy (XPS) to investigate both tricalcium silicate (Ca₃SiO₅, C₃S) and β-dicalcium silicate (Ca₂SiO₄, β-C₂S), the principal components of cement clinkers. In addition to showing how the two phases may be characterised and differentiated, we show how the sensitivity of these phases to atmospheric carbon dioxide and moisture may, as a result of improper sample preparation, lead to erroneous results. The observed alteration processes of the clinker minerals shed light upon the aging process of cement clinker during storage.     

A comparative study of ordinary and mineralised Portland cement clinker from two different production units Part II: Characteristics of the calcium silicates

Portland cement clinkers from two production units were investigated in order to determine the effects of mineralisation on alite and belite; Plant 1: ordinary clinker (P1) and clinker mineralised with CaF₂₊CaSO₄ (P1m); Plant 2: ordinary clinker (P2) and two clinkers mineralised with CaF₂₊CaSO₄ (P2m, P2m′).The polymorphism of alite was studied using synchrotron X-ray powder diffraction (XRD), wavelength 1.5227 Å, and electron diffraction (ED) in a transmission electron microscope. The substitutions of minor elements in alite and belite were determined using electron microprobe analysis. Clinkers P1 and P1m both contained apparent rhombohedral alite (XRD) with an incommensurately modulated structure (ED), while clinkers P2, P2m, and P2m′ all contained monoclinic alite (XRD). The addition of mineralisers in the process caused increased content of fluoride in alite and increased substitution of Si(4+) by Al(3+) and S(6+) in both calcium silicates. The latter effect was most pronounced in clinker P1m due to its high molar SO₃ to alkali oxide ratio (R=2.18).The improved hydraulic activity of P1m compared to P1 was caused by substitutions rather than a change in symmetry. The decreased hydraulic activity of P2m and P2m′ compared to P2 was explained by the high levels of fluorine, which had a retarding effect on the hydration.     

Effect of molar ratio of TiO2/SiO2 on the properties of particles synthesized by flame spray pyrolysis

Titania (TiO₂)–silica (SiO₂) nanoparticles were synthesized from sprayed droplets of a mixture of TEOS and TTIP by flame spray pyrolysis (FSP). The effect of molar ratio between TEOS and TTIP in the mixture on the particle properties such as particle morphology, average particle diameter, specific surface area, crystal structure, etc., were determined using TEM, XRD, BET, and FT-IR. A UV-spectrometer was also used to measure the absorption spectrum and the band gap energy of the product particles. As the molar ratio of TEOS/TTIP increased by increasing TEOS concentration at the fixed TTIP concentration, the average particle diameter of the mixed oxide nanoparticles increased with maintaining uniform dispersion between TiO₂ and SiO₂, and crystal structure was transformed from anatase to amorphous. The band gap energy of the TiO₂–SiO₂ nanoparticles increased with respect to the increase of the molar ratio due to the decrease of width of UV-absorption spectrum. Photocatalytic activity of TiO₂–SiO₂ composite particles decreased with the concentration of TEOS.     

Surface Modification of Amorphous SiO2 Nanoparticles by Oxygen-Plasma and Nitrogen-Plasma Treatments

In this study, amorphous silica gels were synthesized and treated by oxygen plasma and nitrogen plasma at a radio frequency power of 60 W, at heating temperature of 300°C, and a treatment period of 400 s. The silica gels were characterized by using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller, and thermal conductivity analyzers. The characterization results show that oxygen-plasma treatment has remarkably reduced the surface hydroxyl groups in silica gels, whereas nitrogen-plasma treatment has less effects. The reduction of the hydroxyl groups is a key factor contributing to reduced particle size from 30 nm to 15 nm, thus resulting in an increased specific surface area from 124 to 420 m²/g. In addition, the reduced particle size has drastically lowered the thermal conductivity of silica gels, from 0.14220 to 0.00014 W/mK. Therefore, oxygen-plasma treatment is a feasible method to enhance the thermal insulating properties of silica gels.     

Preparation and characterization of multicomponent porous materials prepared by the sol-gel process

An experimental strategy was developed to obtain transparent Si-Al-Ti-Ni-Mo and Si-Zr-Ti-Ni-Mo sols via the sol-gel process. The sol was prepared from Si(OEt)₄ (TEOS), Al(OBu^s)₃ (OBu^s: C₂H₅CH(CH₃)O), Ti(OEt)₄ (OEt: OCH₂CH₃), Zr(OPrⁿ)₄ (OPrⁿ: OCH₂CH₂CH₃). In both cases nickel nitrate hexahydrate (Ni(NO₃)₂ · 6H₂O) and ammonium heptamolybdate tetrahydrate ((NH₄)₆Mo₇O₂₄ · 4H₂O) were the Ni and Mo sources, respectively. The sols were characterized by Fourier Transform Infrared Spectroscopy (FTIR). Assignments of the simultaneous formation of the Si-O-Al, Si-O-Ti, Si-O-Ni, and Si-O-Zr bonds were done. The sols were polymerized at room temperature (293 K) to obtain gels, and these were dried at 423 K and calcined at 573, 853 and 893 K in air. The characterization techniques used were small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR). The density of the solids was measured following ASTM method D-4892 and the porosity and surface area were determined by N₂ adsorption/desorption isotherms. The corresponding average pore diameters were evaluated using the BJH, HK, and DA methods.     

The temperature-programmed desorption of hydrogen from copper surfaces

The desorption kinetics of H₂ from a Cu/ZnO/Al₂O₃ catalyst for methanol synthesis were studied under atmospheric pressure in a microreactor set-up by performing temperature-programmed desorption (TPD) experiments after various pretreatments of the catalyst. Complete saturation with adsorbed atomic hydrogen was obtained by dosing highly purified H₂ for 1 h at 240 K and at a pressure of 15 bar. The TPD spectra showed symmetric H₂ peaks centered at around 300 K caused by associative desorption of H₂ from Cu metal surface sites. H₂ TPD experiments performed with different initial coverages resulted in peak maxima shifting to higher temperatures with lower initial coverages indicating that the desorption of H₂ from Cu is of second order. The microkinetic analysis of the TPD traces obtained with different heating rates yielded an activation energy of desorption of 78 kJ mol^–1 and a corresponding frequency factor of desorption of 3×10¹¹ s^–1> in good agreement with the kinetic parameters obtained with Cu(111) under UHV conditions.     

Flow behavior of polymerizable ceramic suspensions as function of ceramic volume fraction and temperature

The effect of volume fraction and temperature on flow behavior is reported for suspensions of coarse silica powders in two non-aqueous polymerizable solutions. The concentration dependence of the viscosity at temperatures 25-75 °C can be reduced to a single Krieger-Dougherty curve for all suspensions. The temperature dependence of viscosity for suspensions with 60 vol% silica could be fit to an Arrhenius equation. The suspensions had a larger apparent activation energy than the suspension medium. This could be explained in terms of thermal dilution, where the higher thermal expansion of the liquid reduces the solids loading for very concentrated suspensions.