Characteristics and properties of surface coated nano-TiO_2

1Introduction Nano-TiO2,as a new inorganic material,has many excellent properties,such as nontoxic,stable in chemistry and high efficient photocatalytic effect[1,2].As fine particles,it is easy to agglomerate in practical use,especially difficult to dispe…     

溶胶-凝胶旋转涂布法制备的多孔纳米二氧化钛膜的结构和光学性能(英文)

采用溶胶凝胶旋转涂布技术在石英基质上沉积三种不同厚度的TiO2薄膜,其厚度分别为174、195和229nm。沉积得到的薄膜是由尺寸为19~46nm的纳米微晶组成的,并具有较高的多孔结构。测定了薄膜的光学常数,得到了迄今为止报道的最低折射率1.66,并对所得结果进行了讨论。     

MoSi_2含量对MoSi_2/Al_2O_3复合涂层介电与力学性能的影响(英文)

通过喷雾干燥法制备MoSi2包覆Al2O3的壳核结构混合粉,利用该混合粉以等离子喷涂技术制备MoSi2/Al2O3复合涂层材料。研究MoSi2/Al2O3质量比涂层材料的力学和介电性能的影响。结果表明:随着MoSi2含量从0增加到45%,复合材料的抗弯强度和断裂韧性分别从198MPa和3.05MPa·m1/2增加到324MPa和4.82MPa·m1/2,随后又降到310MPa和4.67MPa·m1/2。在8.2-12.4GHz微波频率波段内,随着MoSi2含量的增加,复合材料的介电损耗增加,而介电常数的实部却呈减小趋势。这主要是由于MoSi2颗粒熔化后的凝聚及导电网络结构的形成导致电导率的增加引起的。     

Electrochemical performance of SrF2-coated LiMn2O4 cathode material for Li-ion batteries

SrF2-coated LiMn2O4 powders with excellent electrochemical performance were synthesized. The electrochemical performance of SrF2-coated LiMn2O4 electrodes was studied as function of the level of SrF2 coating. With increasing the amount of the coated-SrF2 to 2.0% （molar fraction）, the discharge capacity of LiMn2O4 decreases slightly, but the cycleability of LiMn2O4 at elevated temperature is improved obviously. In view of discharge capacity and cycleability, the 2.0% （molar fraction） coated sample shows optimum cathodic behaviors. When being cycled at 55 ℃, as-repared LiMn2O4 remains only 79% of its initial capacity after 20 cycles, whereas the 2.0% （molar fraction） coated sample shows initial discharge capacity of 108 mA-h/g, and 97% initial capacity retention.     

Co-electrodeposition and properties evaluation of functionally gradient nickel coated ZrO2 composite coating

For the first time, functionally electroless nickel plated ZrO₂ (NCZ) graded Ni-NCZ composite coating has been successfully co-electrodeposited from a bath with gradually increasing of stirring rate. Studies showed that co-electrodeposition in a bath with stirring rate of 250 r/min results in the maximum co-electrodeposited particle content and the best particle distribution. To produce NCZ graded Ni-NCZ composite coating, the stirring rate was continuously increased from 0 to 250 r/min. The electroplated coating had a continuous gradient increasing of co-electrodeposited NCZ content from substrate towards the surface. The results showed that with increasing the co-electrodeposited NCZ particles content in Ni matrix, microhardness increases from interface towards the surface of the coating. Little crystallite size of Ni matrix and higher co-electrodeposited hard particles content were recognized as the reasons of microhardness increasing. Bend test revealed that the functionally graded composite coating shows more excellent adhesion to the substrate compared with the ordinary distributed Ni-NCZ on the same substrate. This result is attributed to lower mechanical mismatch between coating and substrate in the functionally graded composite coating with respect to the uniformly distributed one. The results of wear resistance measurements reveal that wear resistance of functionally graded Ni-NCZ is higher than that of ordinary distributed composite coating.     

SiO2添加剂对8%Y2O3稳定的ZrO2涂层热震前后表面形貌的影响

在8％Y2O3稳定的ZrO2陶瓷涂层中添加SiO2，使陶瓷涂层的抗热震性能得到提高，这主要是SiO2的加入使涂层抗热震前后的表面形貌发生了很大的变化。由于ZrO2与SiO2热膨胀系数不同，使涂层利于产生细微的网状裂纹，增加了微裂纹密度和孔隙，从而降低了涂层的弹性模量，释放了涂层中的应力，使涂层的抗热震失效能力得到提高。其中，SiO2加入量为3％(质量分数)效果最佳，过量的加入，会使孔洞加大，促进裂纹的扩展、断裂，不利于提高涂层的抗热震性能。     

钛粉制备多级纳米结构TiO_2微球及其光催化特性

在NaOH溶液中采用水热法处理钛粉制备TiO2纳米针/带微球。利用场发射扫描电子显微镜（FESEM）、透射电子显微镜（TEM）、选区衍射（SAED）、紫外-可见吸收光谱（UV-vis）和X射线衍射仪（XRD）对样品结构进行表征。结果显示,水热温度和溶液浓度共同决定晶体的生长方向,纳米针/带微球的直径（40~50μm）与钛粉直径相当。纳米针/带微球经450°C热处理1h后转变锐钛矿。以甲基橙为目标考察样品的光催化活性。在相同条件下,样品的光催化活性为：TiO2纳米针微球〉TiO2纳米带微球〉P25。     

CeO2掺杂对ZrO2-Y2O3纳米涂层性能的影响

在45钢基体表面等离子弧喷涂制备了掺杂不同含量CeO2纳米ZrO2涂层,运用XRD,SEM对涂层的组织结构进行了分析,测试了涂层的结合强度和显微硬度,考察了涂层与铝青铜对磨时的摩擦磨损性能．结果表明,CeO2增加了ZrO2涂层的致密性、结合强度和显微硬度．纳米ZrO2涂层中加入CeO2后,增加了ZrO2涂层／铝青铜摩擦副的摩擦系数,增强了纳米ZrO2涂层,耐磨能力．涂层与铝青铜对磨时,随着CeO2含量的增加,ZrO2涂层粘着磨损形式增强,而涂层脆性断裂脱落的趋势减轻．     

镁合金表面TiO2薄膜制备技术研究进展

综述了目前镁合金表面TiO2薄膜制备技术的研究情况,重点介绍了溶胶-凝胶法、化学镀、液相沉积法、物理气相沉积法、电沉积法、喷雾热解沉积法、原子层沉积技术、激光熔覆、热喷涂等工艺的原理和制备技术.     

Magnetic properties of CeAg2Ge2

A.c. susceptibility and magnetization measurements of CAg₂Ge₂ are reported. Two phase transitions at T = 7 and 11 K are detected. The magnetization curve at T = 4.2 K has a two-step character.     

纳米颗粒增强TiO_2涂层的制备及其防污性能

为提高二氧化钛涂层的防污性能,采用KH-550硅烷改性锐钛矿型TiO_2颗粒,并充分分散于二氧化钛凝胶涂层中。通过降解亚甲基蓝溶液、细菌贴附试验、藻类贴附试验,分别评价了涂层的光催化性能、抗菌性能及抗藻类附着性能,并利用激光共聚焦显微镜及扫描电子显微镜对藻类在涂层表面的附着情况进行分析。结果表明,添加TiO_2纳米颗粒涂层的防污性能较未添加TiO_2纳米颗粒涂层有较大程度的提高。添加粒径为5~10 nm TiO_2颗粒的二氧化钛涂层对小球藻、三角褐指藻及小新月菱形藻的附着降低率分别达到了92.1%、71.5%和62.1%,相较于纯二氧化钛涂层对3种藻类的附着降低率分别提高了29.7%、68.4%和43.5%。TiO_2颗粒的加入可以有效地提高涂层的光催化性能,光催化使得涂层具有亲水、抗菌及自清洁的性能进而有利于提高涂层的防污性能。     

The preparation and characteristics of a rare earth/nano-TiO2 composite coating on aluminum alloy by brush plating

Nano-TiO₂ modified rare earth composite coatings are prepared on 2024 aluminum alloy by brush plating. The composite coating is composed of mainly Ce(OH)₃, Ce(OH)₄, CeO₂ and TiO₂, with less cracks and lower porosity. The addition of nano-TiO₂ enhances the adhesive strength of the rare earth coating to Al substrate, results in refined coating grains and increases the micro-hardness of the coating. The nano-TiO₂ modification obviously improves the corrosion resistance of the rare earth coating. For the composite coating containing 2% TiO₂, both the corrosion current density and the impedance are reduced by more than one order of magnitude in contrast to the values for the pure rare earth coating. The higher barrier ability and increased Ce³⁺ content in the Ce oxides may explain the increase of the corrosion resistance.     

Early stages of oxidation of uncoated and PVD SiO2 coated FeCrAl foils

The high temperature oxidation characteristics of uncoated and SiO₂ PVD-coated FeCrAl foils have been investigated when exposed to laboratory air at 1000 °C during 1, 2, 4, 8, 16, 32 and 60 min. The oxidized samples were characterized using SEM, EDS, AES and SIMS. The results show that the presence of a 100 nm thin SiO₂ PVD coating significantly reduces the oxidation rate of the FeCrAl foil during early stages of oxidation. The decreased oxidation rate displayed by the SiO₂ coated FeCrAl foil is the result of the SiO₂ coating acting as an initial diffusion barrier promoting the formation of a predominantly inward growing Al₂O₃ layer during oxidation. Additionally, by using EDS analysis together with AES and SIMS depth profiling it was shown that the total concentration of Si in the grown oxide scale decreased during oxidation.     

Self-propagating High-temperature Synthesis of Al2O3-TiB2 Coatings by Aluminothermic Reactions

The Al2O3-TiB2 coatings were fabricated on Q235 steel by self-propagating high-temperature synthesis(SHS)process using aluminothermic reactions with aluminum,titania,boron oxide and ferric oxide powders.The effect of the content of excessive aluminum in the reactants on Al2O3-TiB2 coatings was studied when only Al-TiO2-B2O3 system was used for preparation of the coatings.The results indicate that the combustion reaction cannot occur when excessive aluminum is over 40wt%and the coating has good quality when excessive aluminum is 20wt%.In order to improve the bonding of the coating and substrate and optimize the ratio of Al2O3/TiB2,composite reaction systems Al-TiO2-B2O3 and Al-Fe2O3 were used for the preparation of Al2O3-TiB2 coatings.The XRD result shows that the coatings contain FeAl intermetallic compound which can improve efficiently the interface bonding of the coating and substrate.The percentage of Al-Fe2O3 system in reactants has only a small effect on the hardness of Al2O3-TiB2 coating,which is about 22000 MPa(Hv),but has an obvious effect on the morphology and interface bonding of the coatings.     

CuCrZr合金表面等离子喷涂Cr3C2-NiCr及NiAl/Cr3C2-NiCr涂层的结合性能

在CuCrZr合金表面等离子喷涂Cr3C2-NiCr涂层、NiAl/Cr3C2-NiCr复合涂层.测试涂层与基体间的结合强度及涂层的热震性能,结合SEM,EDS和XRD等分析涂层物相变化,探讨涂层的结合机理.结果表明,涂层的结合强度均较高;Ni-Al发生放热反应,生成Al4Ni3,Al3Ni2,AlNi3,剩余的铝与铜反应生成Cu3Al2,CuAl2,CuAl,局部区域形成微冶金结合;二种涂层均以机械锚合为主,在参数适合且基体相同的情况下,涂层结合强度取决于涂层材料的力学性能;相同试验条件下,NiAl/Cr3C2-NiCr复合涂层的热震性能优于Cr3C2-NiCr涂层.     

氢气流量对大气等离子喷涂TiO2涂层导电性的影响

采用大气等离子喷涂方法制备TiO2涂层,研究氢气流量的变化对TiO2涂层的显微结构、相结构以及导电性的影响.随着氢气流量的增加,TiO2涂层的孔隙率减少,缺氧相增加,涂层的电阻率随之减小.同时在通电升温条件下涂层的电导率随温度的升高而增加.结果表明,大气等离子喷涂TiO2涂层主要由金红石相、锐钛矿相和缺氧相Magneli(TinO2n-1,n=4～10)组成,各相的含量与等离子气中氢气的流量有关.     

Synthesis of iron（Ⅲ）-doped nanostructure TiO2/SiO2 and their photocatalytic activity

Iron(Ⅲ)-doped nanostructure TiO2-coated SiO2 (TiO2/SiO2) particles were prepared using the layer-by-layer assembly technique and their photocatalytic property was studied. TiO2 colloids were synthesized employing the sol-gel method with TiCl4 as a precursor. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), SEM, EDS, XPS, and XRD. The experimental results show that TiO2 nanopowders on the surface of SiO2 particles are well distributed, the amount of TiO2 is increased with the adding of coating layers, the pure anatase-TiO2 coating layers are synthesized at 500℃, and the photocatalytic activity of Fe3 -doped TiO/SiO2 is higher than tnat of undoped TiO2/SiO2.     

纳米ZrO2激光重熔涂层组织与性能分析

采用金相试验、扫描电镜试验、热震试验和显微硬度试验对不同激光重熔工艺下的Y2O3部分稳定ZrO2纳米陶瓷涂层组织与性能进行研究.重点分析了涂层重熔宽度与深度、表面形貌、显微硬度和热震性能随激光比能量的变化规律.结果表明,ZrO2纳米陶瓷涂层的重熔深度和宽度随着激光比能量的增大而增加;涂层的表面成形与激光比能量密切相关;涂层的显微硬度随激光比能量的增大而升高;激光比能量对涂层热震性能的影响十分明显,当激光比能量为37.2 J/mm2时重熔涂层的热震性能最好.     

表面改性对纳米SiO_2增强木纤维/PP复合材料微观结构及性能的影响

为研究经表面处理的纳米SiO_2在复合材料内的分散状态及其对复合材料性能的影响,选择硅烷偶联剂KH570对纳米SiO_2进行表面改性,分别通过激光粒度仪、傅里叶红外光谱分析仪、接触角测定仪表征纳米SiO_2的改性效果,采用XRD、SEM对经表面处理后的纳米SiO_2在木纤维/PP内的分散状态进行表征,测试并分析其力学性能、吸水膨胀率和吸水率。结果表明:当KH570的质量分数为5%时,纳米SiO_2的平均粒径为62nm,KH570可以成功接枝在纳米SiO_2表面。其对木纤维/PP复合材料的力学性能提高最优,吸水膨胀率与吸水率最低,弯曲强度达到52.6 MPa,拉伸强度为30MPa,冲击强度可以达到11.8kJ/m2;相比添加未经过表面改性的纳米SiO_2,分别提高了75%,20%和47.5%。     

Crystal structures and structural relationships of KFe2(SeO2OH)(SeO3)3 and SrCo2(SeO2OH)2(SeO3)2

The new phases KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ have been synthesized under low-hydrothermal conditions and their structures were determined by single-crystal X-ray methods. Both compounds are monoclinic; KFe₂(SeO₂OH)(SeO₃)₃: space group P2, A = 9.983(4), B = 5.270(1), C = 10.614(4) Å, β = 97.42(2)°, V = 553.7 ų, Z = 2; SrCo₂(SeO₂OH)₂(SeO₃)₂: space group P2ln, A = 14.984(2), B = 5.286(1), C = 13.790(2) Å, β = 94.72(1)°, V = 1088.5 ų , Z = 4. The refinements converged to R-values of 2.9 and 3.6% respectively.

The atomic arrangement in KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ is based on isolated MO₆ octahedra (M = Fe³⁺, Co²⁺), which are corner-linked via trigonal pyramidal selenite groups to a framework structure. Interstitials are occupied by potassium or strontium atoms in ten- or eight-coordination respectively, and by the lone-pair electrons of the Se⁴⁺ atoms. Both compounds are not isotypic but are closely related and may be interpreted as different distortions of an idealized structure type in space group P2/m, which was modelled for a theoretical compound SrFe₂(SeO₃)₄ by distance least squares refinement (program ).