纳米氧化锌包覆SiO2和SiO2/Al2O3改性粉制备及表征

采用液相沉积法对纳米氧化锌进行表面包覆SiO2和SiO2/Al2O3改性,并用IR、XRD、TG-DSC对其表面结构进行了表征,用紫外-可见分光光度计对其紫外屏蔽性能进行了检测,采用Zeta电位测定仪、静态沉降实验等分析手段考察了改性前后纳米氧化锌在水体系中的分散稳定性。结果表明,在ZnO表面形成的包覆物是以非晶态形式存在的,通过表面包覆SiO2和SiO2/Al2O3改性后纳米氧化锌对紫外光的屏蔽性能有所下降,明显提高了氧化锌的表面羟基含量,有效改变了氧化锌的等电点,显著提高了纳米氧化锌在水中的分散稳定性。     

Synthesis of high near infrared reflection wurtzite structure green pigments using Co-doped ZnO by combustion method

A high near-infrared reflective green pigment with a low cobalt content, Zn_0.96Co_0.04O, was prepared by solution combustion synthesis. The pigment was characterized by XRD, SEM, TG-DSC, UV–vis and CIE L*a*b*C*h* colorimetric. The resulting green pigment showed that the chromaticity performance is better. The doping Co did not affect the main crystalline structure, all samples were retained ZnO wurtzite structure. The better green hue is a* = ?15.35 and achieved a near-infrared reflectivity up to 40%, when CoO content was x?=?0.04, combustion agent was glycine, calcination temperature was 1000?°C. The synthesized pigments have a better thermal stability, chemical stability and a small amount of cobalt oxide (2.8?wt%), and the preparation process is simple. Therefore, the green pigment of ZnO wurtzite structure has great potential in serving as cool pigments for building coatings.     

An in situ high pressure FT-IR study of CO2/H2 interactions with model ZnO/SiO2, Cu/SiO2 and Cu/ZnO/SiO2 methanol synthesis catalysts

In situ FT-IR spectroscopy allows the methanol synthesis reaction to be investigated under actual industrial conditions of 503 K and 10 MPa. On Cu/SiO₂ catalyst formate species were initially formed which were subsequently hydrogenated to methanol. During the reaction a steady state concentration of formate species persisted on the copper. Additionally, a small quantity of gaseous methane was produced. In contrast, the reaction of CO₂ and H₂ on ZnO/SiO₂ catalyst only resulted in the formation of zinc formate species: no methanol was detected. The interaction of CO₂ and H₂ with Cu/ZnO/SiO₂ catalyst gave formate species on both copper and zinc oxide. Methanol was again formed by the hydrogenation of copper formate species. Steady-state concentrations of copper formate existed under actual industrial reaction conditions, and copper formate is the pivotal intermediate for methanol synthesis. Collation of these results with previous data on copper-based methanol synthesis catalysts allowed the formulation of a reaction mechanism.     

Laser irradiation of ZnO:Al/Ag/ZnO:Al multilayers for electrical isolation in thin film photovoltaics

Laser irradiation of ZnO:Al/Ag/ZnO:Al transparent contacts is investigated for segmentation purposes. The quality of the irradiated areas has been experimentally evaluated by separation resistance measurements, and the results are complemented with a thermal model used for numerical simulations of the laser process. The presence of the Ag interlayer plays two key effects on the laser scribing process by increasing the maximum temperature reached in the structure and accelerating the cool down process. These evidences can promote the use of ultra-thin ZnO:Al/Ag/ZnO:Al electrode in large-area products, such as for solar modules.     

Transparent polycrystalline nanoceramics consisting of triclinic Al2SiO5 kyanite and Al2O3 corundum

Transparent polycrystalline nanoceramics consisting of triclinic Al₂SiO₅ kyanite (91.4 vol%) and Al₂O₃ corundum (8.6 vol%) were fabricated at 10 GPa and 1200‐1400°C. These materials were obtained by direct conversion from Al₂O₃‐SiO₂ glasses fabricated using the aerodynamic levitation technique. The material obtained at 10 GPa and 1200°C shows the highest optical transparency with a real in‐line transmission value of 78% at a wavelength of 645 nm and a sample‐thickness of 0.8 mm. This sample shows equigranular texture with an average grain size of 34 ± 13 nm. The optical transparency increases with decreasing mean grain size of the constituent phases. The relationship between real in‐line transmission and grain size is well explained by a grain‐boundary scattering model based on a classical theory.     

Photoluminescence mechanism of annealed ZnO/Zn/Al2O3 sandwich structures deposited on glass substrates

ZnO/Zn/Al₂O₃ sandwich structures are grown on glass substrates by magnetron sputtering. The effect of Al₂O₃ layers on optical properties of ZnO/Zn/Al₂O₃ sandwich structures is investigated. Results indicated that as the deposition time of Al₂O₃ increases, violet peak centered at 402 nm gradually shifted to 412 nm and the intensity firstly decreases and then increases. We discuss the intensity change and shift of violet peak relating to V_Zn defects and the band alignment of ZnO/Zn/Al₂O₃ sandwich structures, respectively. We proposed that ZnO/Zn/Al₂O₃ sandwich structures can be approximately regarded as a quasiquantum-well-like structure. So the electron tunneling from Zn to Al₂O₃ layer is suppressed and the photogenerated carriers can be confined in the Zn Fermi level. In order to further understand the effect of posttreatment on optical properties of samples, samples are annealed in vacuum at 350 °C for 1 h. PL emissions are weakened with the increase of Al₂O₃ deposition time. Interestingly, at a same deposition condition, PL emissions are still improved after posttreatment. Combined Al₂O₃ layer modulation with annealing treatment, steady PL properties can be effectively improved.     

Transparent AlON ceramic combined with VO2 thin film for infrared and terahertz smart window

Transparent AlON ceramics are intriguing window materials with excellent mechanical strength and superb optical transparency from the near ultraviolet to the mid-infrared range. However, previous studies focused their investigations in the visible range; therefore, the application of transparent AlON ceramics to tunable windows has yet to be reported. In this work, a VO₂ thin film with a characteristic semiconductor-metal phase transition (SMT) was fabricated on a transparent AlON ceramic, which exhibited remarkable tunable switching properties in the infrared and terahertz ranges. The transparent AlON ceramic was prepared by a two-step method, which included carbothermal reduction and pressureless sintering. The resulting ceramic exhibited high transparency of over 70% in the visible-infrared range and a notable THz transmission of 64.5–73.9% at 0.1–1.5?THz. The VO₂ thin film was prepared on a transparent AlON ceramic using the sol-gel method and showed excellent optical and electric switching performance. The square resistance variance was close to four orders of magnitude, and an infrared switching ratio of over 40% was obtained. Furthermore, the combined structure showed an efficient THz switching ratio of approximately 70.9%. This study proposes a composite material combined with a transparent ceramic and a phase transition oxide and provides great insights into their application in infrared and terahertz smart windows as well as in switching devices.     

Dielectrics made of Al2O3 and SiO2 for high temperatures

Dielectrics produced from corundum with commercial alumina and from quartz ceramics by hot pressing and by the conventional method with the use of F-9 silicone resin are described. The effect of technological factors on the properties of the specimens is studied.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 12, pp. 7–12, December, 1996.     

Structural and optical properties of doped ZnO/SiO2 nanocomposite

The synthesis of ZnO/SiO₂ nanocomposite doped with Co, Cu and Mn nanoparticles were performed using sol-gel method. Rietveld refinement analysis was done for the X-ray diffraction data and results showed that all samples are single wurtzite hexagonal phase and have an average crystallite size ~14 nm. The lattice parameters, bond length, crystallite size, microstrain, dislocation density and the system volume were studied in details. Transmission electron microscopy technique showed that nanoparticles characterized by an elliptical shape. Fourier transform infrared and scanning electron microscope techniques proved the presence of SiO₂ in the system. The energy gap values of both undoped and doped samples with Co, Mn and Cu were 2.84, 2.47, 2.71 and 2.8 eV, respectively. Photoluminescence spectra for undoped and doped ZnO/SiO₂ were investigated in details.     

纳米SiO2/Al复合粒子的制备

利用在活化微米金属铝粉表面包覆纳米SiO2致密膜的方法，以对推进剂燃烧具有催化作用的纳米膜取代了铝粉表面本身的惰性氧化层。分析了纳米膜包覆的形成机理，并以此制备了纳米SiO2／A1复合粒子。通过检测分析，发现包覆前后颗粒粒度变化不明显，包覆膜的厚度在10nm左右，与铝粉本身的氧化层厚度相当；发现复合颗粒表面有Si-O-Si反对称伸缩振动峰及Si-O-Si弯曲振动吸收峰，表明包覆膜为SiO2。     

Enhancing the thermoelectric properties of super-lattice Al2O3/ZnO atomic film via interface confinement

Aluminum oxide (Al₂O₃)/zinc oxide (ZnO) thin films deposited via atomic layer deposition (ALD) are demonstrated to enhance their thermoelectric properties by manipulating them with a nano-thick Al₂O₃ interface. The overall superlattice structure is tuned by varying the ZnO ALD sequence and the Al₂O₃ ALD sequence while maintaining the same composition. An aluminum-doped zinc oxide (AZO) thin film is deposited at 250 °C, and the Al₂O₃ thickness in the superlattice is gradually increased from 0.13 nm to 1.23 nm. The total film composition is fixed at 2% AZO. We observe that an efficient superlattice structure is made with a specific Al₂O₃ thickness. The thermal conductivity is significantly decreased from 0.57 W/mK to 0.26 W/mK as the thickness of the Al₂O₃ layer is increased. Additionally, the absolute Seebeck coefficient is increased from 14 μV/K to 65 μV/K. This may be caused by the interface confinement effect and interface scattering between the ZnO layer and the Al₂O₃ layer. The figure of merit ZT value is 0.14 for the most efficient structure.     

UV固化SiO_2/超支化聚氨酯丙烯酸酯透明涂层制备与性能

以TEOS和MAPTMS改性硅溶胶为无机组分,以超支化聚氨酯丙烯酸酯(HBPUA)为有机组分,制备了可UV固化HBPUA/(MAPTMS-SiO2)杂化涂层材料,nSiO2∶nMAPTMS=1∶2,改性硅溶胶用量为30ω/%,HBPUA/(MAPTMS-SiO2)杂化涂层材料的凝胶时间大于180 d,透光率为92.8%,硬度为4 H,附着力为0级,柔韧性为3 mm,冲击强度为46 kg·cm,磨耗量为17.5 mg,涂层性能较佳。     

纳米SiO2/丙烯酸UV屏蔽透明涂料的制备及性能研究

通过在丙烯酸树脂中添加不同含量的纳米SiO2，采用共混法制备了纳米SiO2／丙烯酸UV屏蔽透明涂料。研究了纳米SiO2不同添加量时涂料的UV屏蔽性、透明性、粘度及硬度，并对纳米SiO2添加量为3％的涂料样品进行了TEM分析和基本性能测定。     

PE基聚硅氧烷/改性SiO2超疏水薄膜的构筑

使用十八烷基三甲氧基硅烷(OTMS)对纳米SiO2进行表面疏水改性,将得到的改性纳米SiO2(OTMS-SiO2)添加到有机硅树脂(SI)中,然后采用两步法在聚乙烯(PE)薄膜表面固化制备了复合涂层SI/OTMS-SiO2.通过FTIR、1HNMR、29SiNMR、TGA对OTMS-SiO2及复合涂层进行了表征,采用接触角测量仪、SEM、AFM对复合涂层疏水特性和形貌进行了测试和观察,最后对复合涂层的耐磨性和附着力进行了分析.结果表明,SiO2表面成功引入了OTMS,且OTMS-SiO2均匀附着在硅树脂涂层上,增加了表面粗糙度,得到了PE基固化超疏水复合涂层.当OTMS-SiO2添加量为正己烷质量的8％时,制得的复合涂层的水接触角为154°,滚动角为7°,并具有良好的耐磨性,其附着力可达4A等级.     

TiO2/SiO2复合薄膜的制备及其自清洁性能

利用热陈化法得到的纳米TiO2粒子及SiO2聚合物胶粒通过浸渍-提拉技术制备了具有自清洁功能的TiO2/SiO2复合薄膜。考察了SiO2的复合比例对薄膜的表面形貌、透光率、光致亲水及自清洁性能的影响。随着SiO2复合体积分数的增大,薄膜的表面粗糙度、可见光透过率、光致亲水及自清洁性能显示了相似的变化规律。即在V(SiO2)=25%左右时,薄膜的各项特性或性能达到最大值或最小值。该薄膜在室外放置28天后,仍能显示超亲水性能。     

（急）PDMS/ZrO2/SiO2超疏水辐射制冷薄膜的制备及性能

被动日间辐射制冷（PDRC）技术由于不需要外部能源、绿色清洁无污染而受到广泛关注。该文通过将聚二甲基硅氧烷（PDMS）和二氧化锆（ZrO2）颗粒进行复合形成分散液，将其浇铸成膜后得到PDMS/ZrO2辐射制冷薄膜材料，然后通过喷涂PDMS/SiO2分散液对其进行疏水化处理制备了一种超疏水辐射制冷薄膜材料。通过优化ZrO2粒径和喷涂液中SiO2用量，薄膜表面接触角可达156.6 ° ± 2 °，滚动角为0.3 ° ± 0.1 °，呈现优异的自清洁性能。其太阳光反射率高达95.3%，红外发射率大于90%。在太阳光直射下，薄膜可实现平均9.99 ℃的降温效果。薄膜的自清洁性能使其表面不受泥土污染从而具有稳定持久的辐射降温功能。除此之外，薄膜具有优异的机械性能、耐摩擦性能以及耐酸/碱溶液和紫外光照稳定性。     

Simultaneous low reflection in near-infrared range and low emission in long-wave infrared properties of Al/Bi2O3 composites

In this work, flaky aluminum was coated with bismuth oxide to obtain low reflection in near-infrared range and low emission in long-wave infrared stealth material. The composites were prepared through coprecipitation method, characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and measured by ultraviolet spectrophotometer and dual band infrared emissometer. The morphology and microstructure show that the flaky aluminum was coated by bismuth oxide nanoparticles. The optimal reaction temperature was 50 °C, and the optimized amount of Al was 20 wt%. Meanwhile, the infrared emissivity in 8–14 μm infrared waveband range was 0.462 and the reflectivity was 39.1% at wavelength of 1.064 μm. In addition, it could also achieve good thermal insulation in a thinner thickness. When the temperature of heating platform reached 100 °C, the temperature of the disk with 0.30 mm thickness was 26.9 °C which was only 2.7 °C higher than that of the disk with 0.94 mm thickness. It may shed light on a new material design orientation to obtain high performance infrared and laser compatible stealth materials.     

Preparation of a Transparent Spherical Polymer Matrix Containing TiO2/SiO2 Hybrid Materials

A transparent spherical polymer matrix containing TiO₂/SiO₂ hybrid materials is prepared from the copolymerization reaction between TiO₂/SiO₂ hybrid materials containing vinyl groups and methyl methacrylate (MMA). Transparent TiO₂/SiO₂ hybrid materials are prepared from the reaction between nucleophilic agents and tetrabutyl titanate (TBT). Three reaction mechanisms leading to the formation of nanometer TiO₂/SiO₂ hybrid materials, including the single group coordination reaction mechanism (SGCRM), double group chelation reaction mechanism (DGCRM) and bridge coordination reaction mechanism (BCRM) are discussed in detail and confirmed by FT‐IR spectroscopy. The sizes of the TiO₂/SiO₂ hybrid material nanoparticles are also characterized and calculated by TEM and range from 20–40 nm. The diameter of the particles in the transparent spherical polymer matrix is ca. 100–200 nm and their shape is a regular spherical structure from TEM observations. The transparent spherical polymer matrix containing TiO₂/SiO₂ hybrid materials could be used as holographic anti‐counterfeiting materials.     

The effect of the reduction temperature on the structure of Cu/ZnO/SiO2 catalysts for methanol synthesis

The structure of Cu/SiO₂ and Cu/ZnO/SiO₂ catalysts was studied after reduction at 450–1300 K. The influence of the ZnO promoter on the exposed Cu surface area and metal cluster size was determined by N₂O chemisorption and X-ray diffraction. After reduction at 450 K, the metal surface area amounted to 9 m²/g_cat for both catalysts. Oxygen uptake during N₂O chemisorption increased significantly up to reduction temperatures of 800–900 K. This increase was most prominent for the ZnO-promoted catalyst, although no oxygen uptake was observed for a similarly treated ZnO/SiO₂ sample. The behaviour of the promoted catalyst can be explained by formation of Zn⁰, surface alloying, and segregation of ZnO_x species on top of Cu clusters. The high thermostability of the catalysts was confirmed by in situ XRD measurements. The Cu crystallite size in both catalysts was about 4 nm, and did not increase when the reduction temperature was raised to 1100 K for 1 h.     

Synthesis of glass-ceramic glazes in the ZnO–Al2O3–SiO2–ZrO2 system

Glazes in the ZnO–Al₂O₃–SiO₂–ZrO₂ system with crystallization ability of gahnite (ZnO·Al₂O₃) and β-quartz solid solution (βqss) were synthesized. The compositions were designed based on calcium and magnesium oxide replacement (from a CaO–MgO–Al₂O₃–SiO₂ glass-ceramic glaze system) with zinc oxide and simultaneous increasing aluminum oxide. By this replacement, diopside eliminated and co-precipitation of gahnite and zirconium silicate observed. However, a little addition of Li₂O changes the crystallization path by precipitation of βq_ss and willemite (2ZnO·SiO₂) at low temperatures (800–900 °C) which dissolved into glaze by development of firing temperature. The experiments showed that while the micro-hardness of gahnite-based glass-ceramic glazes is almost equal with the diopside based one, it is more than the traditional floor tile glazes.