Al2O3-nanodiamond composite coatings with high durability and hydrophobicity prepared by aerosol deposition

We attempted the room-temperature fabrication of Al₂O₃-based nanodiamond (ND) composite coating films on glass substrates by an aerosol deposition (AD) process to improve the anti-scratch and anti-smudge properties of the films. Submicron Al₂O₃ powder capable of fabricating transparent hard coating films was used as a base material for the starting powders, and ND treated by 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) was added to the Al₂O₃ to increase the hydrophobicity and anti-wear properties. The ND powder treated by PFOTES was mixed with the Al₂O₃ powder by ball milling to ratios of 0.01 wt.%, 0.03 wt.%, and 0.05 wt.% ND. The water contact angle (CA) of the Al₂O₃-ND composite coating films was increased as the ND ratio increased, and the maximum water CA among all the films was 110°. In contrast to the water CA, the Al₂O₃-ND composite coating films showed low transmittance values of below 50% at a wavelength of 550 nm due to the strong agglomeration of ND. To prevent the agglomeration of ND, the starting powders were mixed by attrition milling. As a result, Al₂O₃-ND composite coating films were produced that showed high transmittance values of close to 80%, even though the starting powder included 1.0 wt.% ND. In addition, the Al₂O₃-ND composite coating films had a high water CA of 109° and superior anti-wear properties compared to those of glass substrates.     

Nanocrystalline p-type-cuprous oxide thin films by room temperature chemical bath deposition method

Nanocrystalline cuprous oxide (Cu₂O) thin films were synthesized on amorphous glass substrate by using simple room temperature chemical route namely, chemical bath deposition (CBD) method. The deposition kinetics played important role to get good quality nanocrystalline films with uniform thickness. The structural, surface morphological, optical and electrical properties of the films were investigated. Crystallization and growth processes obtained micro-spherical shaped grains of Cu₂O due to agglomeration of smaller nanoparticles. An optical and electrical characterization was performed to study the optical band gap and type of electrical conductivity of the film.     

SiCf/TC17复合材料的室温拉伸性能

采用磁控溅射先驱丝法制备SiCf/TC17复合材料,结果表明:复合材料中SiCf纤维呈近六方排布,纤维与基体之间结合紧密,没有出现空洞;复合材料的室温抗拉强度为1 773 MPa,相比TC17基体提高83.3%;复合材料的拉伸断口宏观上属于脆性断裂,断口处有大量的界面分离、纤维拔出,其中界面分离最容易发生在C层与反应层间的界面处.     

Structural and dielectric properties of Bi2Zn2/3Nb4/3O7 thin films prepared by pulsed laser deposition at low temperature for embedded capacitor applications

Bi₂Zn_2/3Nb_4/3O₇ thin films were deposited on Pt/TiO₂/SiO₂/Si(1 0 0) substrates at a room temperature under the oxygen pressure of 1-10 Pa by pulsed laser deposition. Bi₂Zn_2/3Nb_4/3O₇ thin films were then post-annealed below 200 °C in a rapid thermal process furnace in air for 20 min. The dielectric and leakage current properties of Bi₂Zn_2/3Nb_4/3O₇ thin films are strongly influenced by the oxygen pressure during deposition and the post-annealing temperature. Bi₂Zn_2/3Nb_4/3O₇ thin films deposited under 1 Pa oxygen pressure and then post-annealed at a temperature of 150 °C show uniform surface morphologies. Dielectric constant and loss tangent are 57 and 0.005 at 10 kHz, respectively. The high resolution TEM image and the electron diffraction pattern show that nano crystallites exist in the amorphous thin film, which may be the origin of high dielectric constant in the Bi₂Zn_2/3Nb_4/3O₇ thin films deposited at low temperatures. Moreover, Bi₂Zn_2/3Nb_4/3O₇ thin film exhibits the excellent leakage current characteristics with a high breakdown strength and the leakage current density is approximately 1 × 10⁻⁷ A/cm² at an applied bias field of 300 kV/cm. Bi₂Zn_2/3Nb_4/3O₇ thin films are potential materials for embedded capacitor applications.     

Er~(3+)掺杂位置对Er~(3+):BaTiO_3薄膜上转换发光的影响(英文)

采用溶胶-凝胶法在LaNiO3/Si衬底上制备Er3+掺杂BaTiO3薄膜。通过XRD、AFM和PL图谱分别研究薄膜的晶体结构、形貌以及上转换发光性能。结果表明,薄膜的微观结构和发光性能与Er3+掺杂晶格的位置有关。A位掺杂薄膜较B位掺杂薄膜具有较小的晶格常数和较好的结晶。PL光谱表明:A位掺杂的薄膜和B位掺杂的薄膜都于528nm和548nm处获得较强的绿色上转换发光以及在673nm处获得较弱的红光,分别对应Er3+离子的2H11/2→4I15/2,4S3/2→4I15/2和4F9/2→4I15/2能级跃迁。相对于B位掺杂的薄膜,A位掺杂样品有较强的绿光发射积分强度以及较弱的红光发射相对强度。这种差异可以通过薄膜的结晶状况和交叉弛豫机制来进行解释。     

SiC-Si3N4 composite coatings produced by plasma-enhanced chemical vapour deposition

Silicon carbonitride coatings have been produced by plasma-enhanced chemical vapour deposition (CVD) on AISI 440C steel in a hot-wall reactor at 250 °C from a mixture of SiH₄, N₂-NH₃ andC₂H₄, and analysed by electron probe microanalysis and Rutherford backscattering spectroscopy-elastic recoil detection. Coatings with different ratios of silicon carbide to silicon sub- and superstoichiometries have been deposited. Stoichiometric coatings show a maximum in their mechanical properties. Depending on the SiC-to-Si₃N₄ ratio, the Knoop hardness values vary between 1500 and 2800 HK_0.025. Internal stress is low at a level of 100–300 MPa. The pinhole density is less than 2 cm^-2. The fracture toughness as determined from indention tests is 4 MPa m^1/2 Linear polarization testing results show excellent protection of the substrate material against chemically aggressive media as compared with conventional CVD.     

Electric-field control of topological spin textures in BiFeO3/La0.67Sr0.33MnO3 heterostructure at room temperature

<正>Electric-field control of topological magnetic states in thinfilm heterostructures is promising for applications in nextgeneration memory or logic devices with ultrahigh density and low-power consumption.Multiferroic materials,where spin and polar degrees of freedom coexist,provide a versatile playground to manipulate magnetism (converse magnetoelectric effect).Here,we report that the topological spin textures can be controlled by electric field in rhombohedral BiFeO₃/monocli...     

Electrochemical performance of magnetron sputter deposited LiFePO4-Ag composite thin film cathodes

LiFePO₄ thin films have been sputtered from a pure LiFePO₄ target onto Ag/SS, Ag/Si₃N₄/Si and Si₃N₄/Si substrates. All of the deposited films were annealed at 973 K for 1 hr in H₂/Ar (5 %) atmosphere. Substrate induced microstructural and crystallographic evolutions have been observed by a scanning electron microscope and X-ray diffraction. Energy dispersion spectra and X-ray photoelectron spectra revealed that Ag was mixed in the LiFePO₄ films deposited on Ag under layers. Ceramic metal composite thin films were obtained. The film conductivity (1 × 10^− 3 Scm^− 1) is therefore elevated by an order of six, compared with pure LiFePO₄ (10^− 9 Scm^− 1). The electrochemical measurements of the LiFePO₄-Ag films showed a flat plateau at 3.4 V (v.s. Li/Li⁺) and a reversible capacity of 80 mAh/g. Optimization of Ag contents may further improve the discharge capacity.     

室温下介孔MnO2降解低浓度甲醛的研究

本文以KMnO₄和P123为原料采用溶胶-凝胶法在不同条件下制备了介孔MnO₂。研究了反应物比和pH对催化剂结构和催化降解性能的影响。溶胶-凝胶法制备介孔MnO₂的最佳条件为：原料配比为10：1,pH值为7。合成材料的结构和性能采用XRD、N₂吸脱附、FT-IR的测试方法表征,结果表明P123和KMnO₄合成的介孔MnO₂具有较大的比表面积和孔径,且有良好的HCHO催化降解性能。最后讨论了介孔MnO₂催化氧化HCHO的影响因素,发现在pH7 的情况下最有利于介孔MnO₂的活性稳定;在原料比为10：1情况下生成的介孔MnO₂比表面积较大,催化降解性能较强,在10h内保持在对甲醛的降解率为95%以上。     

Mechanochemical synthesis of nanocrystalline ZnWO4 at room temperature

Single nanocrystalline ZnWO₄ powders were successfully synthesized by ball milling at room temperature. A stoichiometric mixture of ZnO and WO₃ in a 1:1 molar ratio was subjected to intense mechanical treatment in air using a planetary ball mill (Fritsch - Premium line - Pulversette No. 7) for a period varying from 5 to 300 min. The influence of the four different milling conditions was investigated on the formation of ZnWO₄. The products obtained were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmer-Teller (BET) surface area, infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The synthesis of ZnWO₄ powder started after 5 min milling time and finished after 30 min milling time at a higher speed (1000 rpm). The mechanical treatment up to 300 min did not lead to phase and structure change of ZnWO₄. The product obtained contained nanoparticles with a size of about 50 nm. The photocatalytic activity of the ZnWO₄ powders obtained was investigated by degradation of a model aqueous solution of Malachite Green (MG) upon UV-light irradiation.     

Room-temperature ferromagnetism in nitrogen-doped BaTiO3

The nitrogen-doped BaTiO₃ with a tetragonal phase has been synthesized in the NH₃ (67%)/Ar atmosphere by the standard solid-state reaction method. A weak ferromagnetic behavior with a remanent magnetization of about 5.89 × 10⁻⁵ emu/g is observed at 300 K. The origin of the magnetism is associated with the presence of nitrogen. These results may have implications for further studies on multiferroics.     

Optical,mechanical and etch properties of amorphous carbon nitride films grown by plasma enhanced chemical vapor deposition at room temperature

Amorphous carbon nitride (a-CN) films were grown on Si(1 0 0) and SiO₂/Si(1 0 0) substrates by plasma enhanced chemical vapor deposition at room temperature using gas mixtures of CH₄ and N₂. The as-deposited films showed two bond structures of CN and CN, and with increasing the N₂ content the bond structure changed to graphite-like structure. All the samples showed low optical absorption coefficient (k < 0.15) in the wavelength range of 300–800 nm. The a-CN films exhibited a good resistance to etching (i.e. higher selectivity over SiO₂), which indicates a potential use of a-CN films as a new hard mask material.     

Kinetic Monte Carlo simulation of growth of BaTiO3 thin film via pulsed laser deposition

Considering the characteristics of perovskite structure, a kinetic Monte Carlo（KMC） model, in which Born-Mayer- Huggins（BMH） potential was introduced to calculate the interatomic interactions and the bonding ratio was defined to reflect the crystallinity, was developed to simulate the growth of BaTiO3 thin film via pulsed laser deposition（PLD）. Not only the atoms deposition and adatoms diffusion, but also the bonding of adatoms were considered distinguishing with the traditional algorithm. The effects of substrate temperature, laser pulse repetition rate and incident kinetic energy on BaTiO3 thin film growth were investigated at submonolayer regime. The results show that the island density decreases and the bonding ratio increases with the increase of substrate temperature from 700 to 850 K. With the laser pulse repetition rate increasing, the island density decreases while the bonding ratio increases. With the incident kinetic energy increasing, the island density decreases except 6.2 eV〈Ek〈9.6 eV, and the bonding ratio increases at Ek〈9.6 eV. The simulation results were discussed compared with the previous experimental results.     

Strain rate sensitivity of nanocrystalline Au films at room temperature

The effect of strain rate on the inelastic properties of nanocrystalline Au films was quantified with 0.85 and 1.76 μm free-standing microscale tension specimens tested over eight decades of strain rate, between 6 × 10^?6 and 20 s^?1. The elastic modulus was independent of the strain rate, 66 ± 4.5 GPa, but the inelastic mechanical response was clearly rate sensitive. The yield strength and the ultimate tensile strength increased with the strain rate in the ranges 575–895 MPa and 675–940 MPa, respectively, with the yield strength reaching the tensile strength at strain rates faster than 10^?1 s^?1. The activation volumes for the two film thicknesses were 4.5 and 8.1 b³, at strain rates smaller than 10^?4 s^?1 and 12.5 and 14.6 b³ at strain rates higher than 10^?4 s^?1, while the strain rate sensitivity factor and the ultimate tensile strain increased below 10^?4 s^?1. The latter trends indicated that the strain rate regime 10^?5–10^?4 s^?1 is pivotal in the mechanical response of the particular nanocrystalline Au films. The increased rate sensitivity and the reduced activation volume at slow strain rates were attributed to grain boundary processes that also led to prolonged (5–6 h) and significant primary creep with initial strain rate of the order of 10^?7 s^?1.     

热挤压制备BaTiO_3/Al复合材料的阻尼性能(英文)

为了开发新型高阻尼金属基复合材料,以高温烧结后的大晶粒钛酸钡(BaTiO3)陶瓷作为增强体,通过粉末冶金和热挤压方法制备钛酸钡颗粒增强铝基复合材料,并研究其阻尼特性和力学特性。动态力学分析结果表明,大晶粒钛酸钡陶瓷本身具有很好的阻尼性能,阻尼值可达0.12。但在纯铝基体中加入质量分数为10%BaTiO3制备的BaTiO3/Al复合材料的室温阻尼性能和铝基体相比并无明显改善,而450K以上的阻尼性能由于界面附近的位错运动而大幅度提高。钛酸钡增强体的本征阻尼性能未能充分发挥的原因在于钛酸钡颗粒与铝基体之间的界面结合不良,导致钛酸钡颗粒内部的能量耗散机制无法触动。复合材料的拉伸性能比相应纯铝基体的提高了42%,这意味通过改善界面结合和加入高含量的碳酸钡阻尼增强颗粒,有望获得高强度高阻尼金属基复合材料。     

Combustion chemical vapour deposition of Al2O3 films: Effect of temperature on structure, morphology and adhesion

Alumina films were synthesized on Si(100) substrates at different temperatures in the range of 600 to 900 °C using open atmosphere combustion chemical vapour deposition (C-CVD) technique. A custom made premixed-diffusion type burner with an extra coaxial oxygen inlet close to the burner mouth enabled variation of deposition temperature from 600 to 900 °C in steps of 100 (± 10) °C. The presence of γ- and θ-alumina phases were observed in films synthesized in the temperature range of 600-800 °C, whereas at 900 °C single phase θ-alumina films were obtained. Adherent coatings were obtained at temperatures ≥ 700 °C. The grain size and roughness of the films increased with deposition temperature. The films underwent two types of adhesion failures, a continuous ductile perforation and a tensile type hertzian crack due to the presence of interfacial oxide layer, during scratch test. The presence of SiO₂ interfacial layer between substrate and film was discerned from ellipsometric studies.     

用于室温相变储能材料的NaNO3-LiNO3-KNO3-H2O体系相图预测

采用Pitzer-Simonson-Clegg模型对四元体系NaNO3-LiNO3-KNO3-H2O在273~358 K的溶解度相图进行预测,模型参数拟合于二元体系NaNO3-H2O、LiNO3-H2O、KNO3-H2O和三元体系NaNO3-LiNO3-H2O、NaNO3-KNO3-H2O、LiNO3-KNO3-H2O的水活度、渗透系数及溶解度数据,发现一个四元共晶点,该点组成为5.9%NaNO3、76.2%LiNO3.3H2O和17.9%KNO3(质量分数),相变温度为295.6 K。通过吸放热行为测试及DSC检测对共晶点组成材料的储热性能进行研究。结果表明:该材料在相变温度附近具有良好的储放热性能,且热焓很大,可作为潜在的室温相变储能材料。     

HOPG上ALD沉积Al2O3介电薄膜的生长行为研究

本文采用原子层沉积(ALD)的方法,选择三甲基铝(TMA)和H₂O₂作为反应前驱体,在高定向热解石墨(HOPG)基体上沉积Al₂O₃。系统研究了反应温度和生长周次对Al₂O₃生长行为的影响。研究表明：受HOPG表面饱和成键的影响,Al₂O₃在衬底表面处形核困难,在生长初期主要表现为台阶处择优生长,其形态为线状结构。当沉积100周次Al₂O₃时,其中在沉积温度为50 °C、150 °C和200 °C时呈现为纳米线状结构,而在100 °C时呈现为非连续薄膜。随着生长周次的增加,不同温度下沉积态Al₂O₃都趋于形成连续薄膜,表明其生长行为发生了由三维岛状生长模式向二维平面生长模式的转变。分析认为,生长模式的转变是由纳米线状结构横向生长造成的;横向生长速率主要受生长温度影响。拉曼结果表明：沉积后的石墨烯层结构未受影响,可保留其原有的优越性能。     

Growth of nano crystalline near α phase tantalum thin films at room temperature using cylindrical magnetron cathode

The much desired α (bcc) Tantalum (Ta) thin films are grown at room temperature using a newly designed cylindrical magnetron cathode (with rotating magnets geometry) with pulsing power. The new design has facilitated oblique incidence of adatoms. The electron temperature of the plasma has been enhanced due to the pulsing frequency (100 kHz). These two factors: oblique incidence of adatoms and enhanced electron temperature are presumed to be responsible for the formation of α phase Ta thin films at room temperature. The volume fractions of α and β phases have been evaluated from the X-ray data. The effect of pulsing (0-100 kHz) on the structural, electrical and mechanical properties of Ta thin films has also been studied. With the pulsing frequency, the lattice spacing in the Ta thin films increases (due to the incorporated argon) resulting in an increase in the compressive stress. Up to 75 kHz of the pulsing frequency, the Ta films formed are in the β phase (tetragonal) with ~ 13 nm grain size. At 100 kHz pulsing, the change in the surface morphology also indicates the phase change in the film.