Cross-sections of hydrous and composite aluminum oxide films

Sections of oxide films on aluminum, about 100 nm thick, were examined by transmission electron microscopy. The films were produced by reaction with boiling water and by subsequent anodic oxidation of these surfaces. Both types of films have multi-layer structures. Direct evidence was obtained for the incorporation of pseudoboehmite into the barrier oxide during anodization, and the high field strength of this barrier oxide was confirmed.     

Ellipsometric measurements of the barrier layer in composite aluminum oxide films

The composite oxide film (hydrous + anodic) formed on aluminum foil was chemically stripped to remove only the outer hydrous layer. Ellipsometry of the remaining barrier film showed it to be thinner and have a higher refractive index than conventional anodic barrier films grown to the same voltage. Reanodization to improve film stability gave a further increase in refractive index which indicated that the barrier film had contained some voids. The barrier film is almost entirely crystalline γ-Al₂O₃ and the higher field strength compared with conventional amorphous anodic films on aluminum is believed to be a characteristic of the denser oxide.     

Effect of hafnium oxide on continuous aluminum oxide-mullite-hafnium oxide composite ceramic fibers

The Al₂O₃-mullite-HfO₂ (AMH) ceramic fiber with a 20 wt% of HfO₂ has demonstrated good tensile strength and good high-temperature stability due to the tiny diameter and small grains even at high temperatures. To investigate the effect of HfO₂ on crystal behavior and high-temperature performance, continuous AMH ceramic fibers with different HfO₂ contents (0 wt%, 10 wt%, and 50 wt%) were prepared by melt-spinning of polymer precursors. The effect of HfO₂ on the crystal form transition process, mechanical properties, and high-temperature resistance of AMH fibers was studied by in-situ XRD and STEM. The AMH fibers with 50 wt% HfO₂ had the highest strength retention rate of 78.33% after heat treatment at 1200 °C for 0.5 h. After 0.5 h of heat treatment at 1500 °C, the grain size of the AMH fibers with 50 wt% HfO₂ was still less than 200 nm.     

Lead germanium oxide sinter-assisted PZT composite thick films

Thick films of niobium doped lead zirconate titanate (PNZT) were prepared from a sol-gel/PZT powder composite slurry. The effects of adding different amounts of sol-gel derived lead germanium oxide (PGO) as sintering aid were examined. Four layers of composite, with intermediate sol infiltrations, were deposited by spinning onto Pt/Ti/SiO₂/Si substrates followed by drying and annealing. Addition of PGO enhanced the densification process at a temperature as low as 770 °C. It resulted in an increase in the film properties that depended upon the level of PGO addition. Film properties were assessed by measuring the capacitance and dielectric loss. d_33,f and e_31,f piezoelectric coefficient measurements were carried out after poling at 10 V/μm for 5 min at 130 °C. A maximum relative permittivity of 500 was observed between 5 and 8 wt.% PGO addition. The maximum in d_33,f was found to be about 40 pC/N. Additions between 7 and 10 wt.% PGO led to the maximum e_31,f piezoelectric coefficient of about −1.5 C/m².     

铝/铅-碳化钨-氧化铈复合电极的耐腐蚀性能

以1060铝为基体,在由Pb(CH3COO)2 220 g/L,HBF4170 g/L,H3BO314g/L,明胶2g/L,十六烷基三甲基溴化铵0.5～1.0 g/L组成的基础镀液中,电沉积制得Pb-WC-CeO2复合镀层.通过测定其作阳极电解锌时的塔菲尔曲线,研究了WC和CeO2颗粒的质量浓度、电流密度、温度及搅拌速...     

Electrical properties of polyimide composite films containing TiO2 nanotubes

A study on the dielectric behavior of polyimide composite films containing different amounts of TiO₂ nanotubes (TNs) was performed. The films were prepared by casting solutions resulting from direct mixing of a poly(amic acid) and TNs onto glass plates, followed by thermal imidization. The influence of TNs content on the properties of polyimide composites was investigated. AFM and SEM analyses showed good compatibility between the filler and polymer matrix. Dynamic mechanical analysis and broadband dielectric spectroscopy were used to evidence relaxation processes into the films. The electrical properties were evaluated on the basis of dielectric constant and dielectric loss, and their variation with frequency and temperature. At moderate temperature a secondary β relaxation was observed while incorporation of TNs decreased the activation energy and facilitated the appearance of an additional β ₁ process. An α relaxation and a conductivity process were evidenced at higher temperatures. The values of dielectric constant and dissipation factor increased with TNs amount, and the maximum of σ relaxation peak shifted to higher temperatures. POLYM. COMPOS., 38:2584–2593, 2017. © 2015 Society of Plastics Engineers     

Electrochemical formation of Ir oxide/polyaniline composite films

The primary goal of this work has been to electrochemically form and then characterize a composite polyaniline (PANI)/hydrous Ir oxide (IrOx) film. Efforts to electrochemically form IrOx and PANI simultaneously in acidic aniline-containing solutions failed, likely as aniline adsorption on Ir prevents IrOx formation. Successful composite films were therefore made by first forming an anodic IrOx film on bulk Ir and then depositing PANI into its pores. Based on the characteristics of the PANI redox peaks, it is seen that all of the PANI film that is electrochemically active is in direct electrical contact with the Ir surface at the base of the IrOx film pores. This is consistent with the cross-sectional SEM and EDX analyses, showing the formation of films of uniform thickness and composition. Thin films of Ir nanoparticles, subsequently converted to IrOx, were also used as a template for PANI formation within the porous structure. These hybrid films exhibit an enhanced internal porosity, ease of multiple coating formation (up to 20 μm in thickness), high charge densities, unusual electrochromic behavior, and very rapid charge transfer kinetics. The formation of composite IrOx/PANI films also resulted in a widening (by 0.3-0.4 V) of the potential window over which a pseudocapacitive and electrochromic response is seen.     

三氧化二铝/硅橡胶复合材料热导率的预测

应用最小热阻力法则和比等效热导率法则,建立颗粒填充聚合物基复合材料的导热模型并推导出等效热导率公式,并对三氧化二铝/硅橡胶复合材料热导率进行预测.结果表明,复合材料热导率预测值与实测值接近;三氧化二铝粒径较小时,预测值与实测值更为接近;三氧化二铝体积分数相同时,大粒子填充硅橡胶复合材料热导率更高.     

Characterization of aluminum gallium oxide films grown by pulsed laser deposition

Aluminum gallium oxide (AGO) films were prepared on conventional c-plane sapphire by pulsed laser deposition (PLD). In the current PLD-AGO studies, target composition or growth temperature is usually the main deposition variable, and the other growth conditions are fixed. This would make it difficult to fully understand the theory and characterization of AGO films. In this study, several growth parameters such as target composition, gas atmosphere, laser repetition frequency, growth pressure, and substrate temperature (T_s) were all modulated to realize and optimize the AGO growth. When the (Al_xGa_1-x)₂O₃ target with the Al content larger than 20?at% was used, a serious target poisoning phenomenon occurred, leading to the extremely unstable growth rate. In comparison to the AGO film grown with argon atmosphere, the higher transparency was reached in the film prepared with oxygen atmosphere due to the relative abundance of oxygen. Because of the homogeneous oxygen reduction, the AGO film with the higher crystal quality was obtained at a higher laser repetition frequency. With an increment of growth pressure, the Al content of AGO film was increased. The growth of AGO film at the higher T_s would cause the higher bandgap value, smoother surface, and growth rate degradation. Additionally, the crystal quality of AGO film can be also improved both by increasing the growth pressure and T_s. The better characterization can be reached in the AGO film grown using the (Al_0.05Ga_0.95)₂O₃ target with oxygen atmosphere at the working pressure of 2?×?10^?1 Torr, the laser repetition frequency of 10?Hz, and the T_s of 800?°C. When the metal-semiconductor-metal photodetector fabricated with this AGO active layer, the best performance including the photocurrent of 7.56?×?10^?8 A, dark current of 1.59?×?10^–12 A, and photo/dark current ratio of 4.76?×?10⁴ (@5?V and 240?nm) were achieved.     

Photoluminescence emission of nanoporous anodic aluminum oxide films prepared in phosphoric acid

The photoluminescence emission of nanoporous anodic aluminum oxide films formed in phosphoric acid is studied in order to explore their defect-based subband electronic structure. Different excitation wavelengths are used to identify most of the details of the subband states. The films are produced under different anodizing conditions to optimize their emission in the visible range. Scanning electron microscopy investigations confirm pore formation in the produced layers. Gaussian analysis of the emission data indicates that subband states change with anodizing parameters, and various point defects can be formed both in the bulk and on the surface of these nanoporous layers during anodizing.     

Studies of composite films of polyethylene oxide doped with potassium hexachloroplatinate

The permittivity and conductivity relaxation processes of polyethylene oxide (PEO) composite along with potassium hexachloroplatinate (K₂PtCl₆) electrolytes additive forming PEO/K₂PtCl₆ complex composite have been investigated. The complex composite has been used as a model for dry-polymer electrolytes (PEs) due to the fact that, the anion is large enough for mimicking the immobilized anion in real dry-polymer electrolytes. Stand-free composite films with 0%, 1%, 3%, and 5% concentrations of K₂PtCl₆ have been studied using broadband dielectric spectroscopy in the temperatures range from 150 K until 345 K. The microstructural dynamics revealed the α-, β-, and σ-relaxations and their salient spectral characteristics at various concentrations of K₂PtCl₆ in PEO. The experimental ε” master curves were fitted to HN function for one and/or two relaxation peaks with and without the electrical conductivity contribution in order to investigate the relaxation time (τ), dielectric strengths (Δε), modulus formalism (M”) and the electrical conductivitie (σ). The translational and reorientational degrees of freedom of PEO/K₂PtCl₆ complex composites are responsible for the relaxation behavior which is predicted to be correlated to the relaxation behavior of the polymer electrolyte below and above the glass transition temperature (T_g). The relaxation time (τ) deduced from β-relaxation follows Arrhenius-like behavior while that deduced from α-relaxation process follows Vogel–Tamman–Fulcher (VTF) behavior.     

The galvanoluminescence spectra of barrier oxide films on aluminum formed in organic electrolytes

In this paper, for the first time we have presented the results of the galvanoluminescence (GL) spectra measurement obtained from barrier oxide films during aluminum anodization in various barrier film forming organic electrolytes (aqueous solution of citric acid, tartaric acid, malic acid, succinic acid and ammonium tartarate). Galvanoluminescence spectral measurements were performed utilizing spectrograph system based on the Intensified Charge Coupled Device (ICCD) camera, intended for time-resolved detection of GL phenomena dynamics. The spectra were recorded for different values of electrolyte temperature and anodization current density. We have showed that there are strong GL bands in the visible region and the shape of the spectra as well as peak intensity of the GL bands depend on the anodization voltage. The results cleraly indicate the existance of more then one type of GL centra or GL mechanisms in barrier films formed in organic electrolytes.     

Novel polyimide/graphene oxide composite films with ultralow dielectric constants

Graphene is generally used for conductive material; it can also be used as a key nanofiller for the insulation material of inverter motors. In this study, a series of polyimide (PI) films were prepared successfully by a conventional two‐step polymerization method based on bis[3,5‐dimethyl‐4‐(4‐aminophenoxy)phenyl]methane as a diamine and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride as a dihydride with different weight percentage graphene oxide (GO) nanosheets as nanofillers. The dielectric constant (ε) and dielectric loss (tan δ) of these films were measured. The results show good dielectric properties, especially an ultralow ε value of 1.41 at 1 MHz with 0.19% GO. This showed that the low ε value was caused by a high free volume led by the GO nanosheets and the C? F bond. The structure and micromorphology of the PIs were characterized by X‐ray diffraction and scanning electron microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41385.     

Electrical properties of acrylic resin composite thin films with graphene/silver nanowires

Silver nanowires and graphene were used to form networks within acrylic resin to improve its toughness and conductivity through silane coupling agent. Meanwhile, acrylic resin was favorable to the adhesion of graphene to glass substrates and the connection among graphene sheets to form films. Experimental results indicate that after annealing at 400°C, sheet resistances of graphene‐silver nanowire films were lower than those graphene films without silver nanowires. The findings in this study provide helpful information on the fabrication of graphene‐based electronic devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42387.     

Improved output performance of hybrid composite films with nitrogen-doped reduced graphene oxide

In this research, graphene-based ceramic/polymer hybrid composite films for energy harvesting devices were prepared and analyzed. Nitrogen-doped reduced graphene oxide (N-rGO) conductive elements were embedded in a ceramic/polymer matrix as floating electrodes to form a micro-capacitor composite structure. The effects of nitrogen atom substitution on the rGO materials were investigated and their conducting properties improved. The employment of rGO- and N-rGO-based floating electrodes resulted in the formation of micro-capacitors and an increase in the potential energy of the composite films. The increase in the potential energy consequently increased the output energy of the energy harvesters. The highest voltage and energy density of the composite films were 8.5 V and 1.46 mJ/cm³, respectively, for the N-rGO based ceramic/polymer composite film.     

超声波对铝阳极氧化工艺及膜层性能的影响

将超声波应用于铝的阳极氧化处理,研究了超声波对阳极氧化特性曲线、电解工艺参数和膜层形貌的影响。结果表明,超声波能增加氧化膜的生长速率,提高阳极氧化温度与氧化电流密度的上限值,可实现在较高温度和大电流密度下对铝进行阳极氧化。超声波作用下获得的铝氧化膜层表面孔隙率低,膜层均匀,膜的厚度与硬度都比不加超声波体系有明显提高。     

Luminescence properties of oxide films formed by anodization of aluminum in 12-tungstophosphoric acid

In this paper, we have investigated luminescence properties of oxide films formed by anodization of aluminum in 12-tungstophosphoric acid. For the first time we have measured weak luminescence during anodization of aluminum in this electrolyte (so-called galvanoluminescence GL) and showed that there are wide GL bands in the visible region of the spectrum and observed two dominant spectral peaks. The first one is at about 425 nm, and the second one shifts with anodization voltage. As the anodization voltage approaches the breakdown voltage, a large number of sparks appear superimposed on the anodic GL. Several intensive band peaks were observed under breakdown caused by electron transitions in W, P, Al, O, H atoms. Furthermore, photoluminescence (PL) of anodic oxide films and anodic-spark formed oxide coatings were performed. In both cases wide PL bands in the range from 320 nm to 600 nm were observed.     

Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices

Gallium and aluminum co-doped zinc oxide (GAZO) films were produced by magnetron sputtering. The GAZO films were post-annealed in either vacuum or hydrogen microwave plasma. Vacuum- and hydrogen microwave plasma-annealed GAZO films show different surface morphologies and lattice structures. The surface roughness and the spacing between adjacent (002) planes decrease; grain growth occurs for the GAZO films after vacuum annealing. The surface roughness increases and nanocrystals are grown for the GAZO films after hydrogen microwave plasma annealing. Both vacuum and hydrogen microwave plasma annealing can improve the electrical and optical properties of GAZO films. Hydrogen microwave plasma annealing improves more than vacuum annealing does for GAZO films. An electrical resistivity of 4.7 × 10⁻⁴ Ω-cm and average optical transmittance in the visible range from 400 to 800 nm of 95% can be obtained for the GAZO films after hydrogen microwave plasma annealing. Hybrid organic photovoltaic (OPV) devices were fabricated on the as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO-coated glass substrates. The active layer consisted of blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the OPV devices. The power conversion efficiency of the OPV devices is 1.22% for the hydrogen microwave plasma-annealed GAZO films, which is nearly two times higher compared with that for the as-deposited GAZO films.     

Poly(propylene carbonate)/aluminum flake composite films with enhanced gas barrier properties

A series of poly(propylene carbonate) (PPC)/aluminum flake (ALF) composite films with different ALF contents were prepared via a melt‐blending method. Their cross‐section morphologies, thermal properties, tensile strength (TS), and gas barrier properties were investigated as a function of ALF contents. SEM images reveal the good dispersion and orientation of ALF along with melt flow direction within PPC matrix. The oxygen permeability coefficient (OP) and water vapor permeability coefficient (WVP) of the composite films decrease continuously with ALF contents increasing up to 5 wt %, which are 32.4% and 75.2% that of pure PPC, respectively. Furthermore, the TS and thermal properties of PPC/ALF composite film are also improved by the incorporation of ALF particles. The PPC/ALF composite films have potential applications in packaging area due to its environmental‐friendly properties, superior water vapor, and oxygen barrier characteristics. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41663.     

Optical and electrical analysis of polyethylene oxide/disodium hexachloroplatinate complex composite films

The present study reports the synthesis of composite films comprising PEO/Na₂PtCl₆ complex and their deposition onto fused silica substrates via the dip-coating method. Chemical, crystallographic, and thermal characterizations are carried out to confirm the incorporation of Na₂PtCl₆ and PEO matrix into the films. The transmittance of the PEO film is initially high and decreases subsquently with an increase in Na₂PtCl₆ content. The optical band-gap energy of the composite films decreases exponentially from 4.62 to 3.79 eV with the increase in Na₂PtCl₆ content. Furthermore, in the normal dispersion region, the refractive index of the PEO film decreases from 2.00 to 1.670 as the wavelength increases from 400 to 700 nm. The refractive index values increase with an increase in the concentration of Na₂PtCl₆ in the PEO film up to 8 wt.%. The incorporation of Na₂PtCl₆ into the PEO matrix increases the electrical conductivity because of the combined enhancement of the PEO conductivity and increase i Na₂PtCl₆. These findings suggest that PEO/Na₂PtCl₆ complex composite films have potential applications in UV-shielding and optoelectronic devices.