The use of XPS, FTIR, SEM/EDX, contact angle, and AFM in the characterization of coatings

Coatings are applied to surfaces for a variety of reasons: to enhance their appearance, to protect the substrate, to augment the adhesion to other layers, or to functionalize them for further reactions. To evaluate the efficacy of the coating, it is often necessary to analyze the substrate and the coating to ensure that the needed characteristics are present. To this end, the use of x-ray photoelectron spectroscopy (XPS), contact angle, and atomic force microscopy (AFM) can provide information about the surface composition, its morphology, and its ability to be wetted with various solvents. Scanning electron microscopy with energy dispersive x-ray analysis (SEM/EDX) and Fourier transform infrared spectroscopy (FTIR) can provide a clear picture of the near surface components as well as the continuity of coatings. All of these aspects are valuable in evaluating a coating and essential when problems are encountered. The application of these techniques to the analysis of coatings is discussed.     

Electrochemical impedance spectroscopy and morphological analyses of pyrrole, phenylpyrrole and methoxyphenylpyrrole on carbon fiber microelectrodes

In this study, N-pyrrole (Py), N-phenylpyrrole (PhPy), and 1[4-methoxyphenyl]-1H-pyrrole (MPhPy) homopolymers were synthesized electrochemically onto carbon fiber microelectrodes (CFMEs). The influences of the substituent effect on electrochemical impedance spectroscopy (EIS) were studied comparatively. All the monomers were electrodeposited in 0.05 M tetraethyl ammonium perchlorate (TEAP)/dichloromethane (CH₂Cl₂) solution and characterized by cyclic voltammetry (CV), Fourier transform infrared reflectance spectrophotometry (FTIR-ATR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The morphological study reveals that the polymers were deposited as a continuous and well adhered film to surface of the CFME. An equivalent electrical circuit for three different monomers on CFMEs was proposed and experimental data were simulated to obtain the numerical values of circuit components. All results support the high quality film deposition that resulted in desired electronic properties due to the electron donating behaviors of substituent group of phenyl and methoxy.     

Laser-assisted synthesis of carbon nanofibers: From arrays to thin films and coatings

Carbon nanofiber assemblies in the form of non-aligned films, arrays of vertically aligned nanofibers, aligned nanofiber mats and composite coatings were produced by laser-assisted catalytic chemical vapor deposition. A visible argon ion laser was used to thermally decompose pure ethylene over alumina supported nickel catalysts. Straight, vermicular, beaded, branched and coiled individual nanofibers were observed. The effects of the laser irradiation time on individual nanofiber characteristics, thus on overall nanofiber assembly characteristics were investigated. The arrays, nanostructured films and coatings were examined by scanning electron microscopy. The individual nanofibers were examined by transmission electron microscopy. Nanofiber texture and nanotexture were assessed by lattice fringe analysis of high resolution transmission electron microscopy images. The observed variation in the interfringe distance along the nanofiber wall suggests a pulsed growth mode. This growth mode and the nanofiber shaping mechanism are discussed. Recommendations on how to control nanofiber characteristics such as shape and internal structure are provided.     

Effect of carbon fiber surface treatment on Cu electrodeposition: The electrochemical behavior and the morphology of Cu deposits

The relationship between surface functional groups and electrochemical behaviors of polyacrylonitrile (PAN)-based carbon fibers (CFs) differentiated by oxidation treatment in air was studied. The chemical character of the CFs surface was estimated by X-ray photoelectron spectroscopy (XPS) and the electrochemical behavior of treated CFs in CuSO₄ plating solution was studied by electrochemical setup. The influence of functional groups on the morphology of copper deposits was characterized by field-emission scanning electron microscopy (FESEM). It was found that the O/C atomic ratio rose rapidly from 23.05% (as-received carbon fibers) to 42.83% as the oxidation temperature was increased to 400 °C and the content of -CO was the highest. Concentrations and types of the functional groups on CFs surface showed a close connection with the electrochemical response of CFs in CuSO₄ plating bath. It was showed that Cu electrodeposition was the interaction of applied voltage and the reduction of surface functional groups. With the functional groups increased, the quantities of the Cu nuclei increased, further the morphology of deposited Cu was affected.     

The effect of 3-methyl 1-pentyn 3-ol on the corrosion of Al-Si-Cu alloys in acid solutions by using SEM,EDX and AAS

In this study, the effect of alloying elements on the corrosion of Al-Si-Cu alloys in H₂SO₄ and HCl media content 3-methyl-1pentyn-3-ol (3mlp3ol) is investigated by using SEM, EDX, AAS. The effect of active elements and 3-methyl-1-pentyn-3-ol (inhibitor) on the corrosion of alloys is determined using SEM, EDX and AAS results. Experimental results which indicated active alloying elements are Cu, Zn, Mg for Al-Si-Cu alloys in the studied solutions. The article is published in the original.     

Sintering and microstuctural characterization of W, Nb and Ti iron-substituted BiFeO3

The sintering behaviour and the microstructural evolution of W⁶⁺, Nb⁵⁺ and Ti⁴⁺ iron-substituted BiFeO₃ ceramics have been analyzed. The obtained results show that W⁶⁺ and Nb⁵⁺ ions interact with the secondary phases usually present in these materials, thus altering the solid state formation of the BiFeO₃ phase. In contrast, Ti⁴⁺ ions incorporate into the perovskite structure, leading to an exceptionally low proportion of secondary phases. In addition to this, BiFe_0.95Ti_0.05O₃ materials present a dense microstructure with submicronic and nanostructured grains, clearly smaller than those in the undoped materials.     

Preparation and characterization of mullite whiskers from silica fume by using a low temperature molten salt method

Mullite whiskers were prepared from silica fume in molten Al₂(SO₄)₃-Na₂SO₄ mixture salts at low temperatures. The resulting mullite whiskers, as well as the nucleation and growth mechanism in the molten environment, have been investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TG-DTA) techniques. XRD studies showed that the materials obtained were orthorhombic mullite. SEM, TEM and HRTEM results revealed that the mullite whiskers were single crystal fibers with diameters ranging from 30 to 150 nm and lengths of over several microns. According to thermodynamic analysis, mullite phase might be spontaneously formed in molten salts as the temperature reached the decomposition temperature of aluminum sulfate (1023 K). Moreover, the mullite crystals grew along [1 1 1] crystal plane firstly and developed into fibrous microstructure finally.     

Effect of carbon source on the carbothermal reduction nitridation for synthesis of (Ti, W, Mo, V)(C, N) nanocrystalline powders

The effect of carbon source on the carbothermal reduction-nitridation during synthesizing (Ti, W, Mo, V)(C, N) nanocrystalline powders was investigated. For a systematic comparison, activated carbon, graphite and two kinds of carbon black powder were used as reducing agents in this study. Ultrafine (Ti, W, Mo, V)(C, N) powders with a particle size of ~ 200-500 nm have been produced at 1450 °C for 2 h by using nanosized carbon black source with small particle size. The presence of phases in the reaction products was characterized with X-ray diffraction (XRD) and the microstructure of carbon source powders and final products was studied by scanning electron microscopy (SEM). The results show that the formation of the Ti(C, N) phase is strongly dependent on the particle size of carbon source powders, and the synthesizing temperature of the Ti(C, N) phase decreases significantly from 1750 °C to 1300 °C by using nanosized carbon black, as compared with micron graphite. In addition, activated carbon with a particle size of 5-50 μm does not favor the dissolution of tungsten or molybdenum carbides into Ti(C, N) despite its large specific surface area.     

Facile synthesis and electromagnetic wave absorption properties of magnetic carbon fiber coated with Fe-Co alloy by electroplating

Magnetic carbon fiber coated with Fe-Co alloy was prepared by electroplating at 25 °C for 5 min. The obtained magnetic coatings show sheet-like morphology and the crystal structure of the uniform coating is Co₃Fe₇ with a thickness of about 0.5 μm. The saturation magnetization of the magnetic carbon fiber reaches 31.5 emu/g with a coercivity of 87.1 Oe. The complex permittivity and permeability of magnetic carbon fiber/paraffin (30 wt%) composite were measured in the 2-18 GHz frequency range. The reflection loss below −10 dB covers the whole frequency range while below −20 dB the absorption frequency bandwidth is 6.8 GHz, and the minimum value is −48.2 dB at a coating thickness of 1.7 mm. Magnetic carbon fiber exhibits excellent electromagnetic wave absorption properties.     

Microstructural and mechanical properties of Al-Mg/Al2O3 nanocomposite prepared by mechanical alloying

The effect of milling time on the microstructure and mechanical properties of Al and Al-10 wt.% Mg matrix nanocomposites reinforced with 5 wt.% Al₂O₃ during mechanical alloying was investigated. Steady-state situation was occurred in Al-10Mg/5Al₂O₃ nanocomposite after 20 h, due to solution of Mg into Al matrix, while the situation was not observed in Al/5Al₂O₃ nanocomposite at the same time. For the binary Al-Mg matrix, after 10 h, the predominant phase was an Al-Mg solid solution with an average crystallite size 34 nm. Up to 10 h, the lattice strain increased to about 0.4 and 0.66% for Al and Al-Mg matrix, respectively. The increasing of lattice parameter due to dissolution of Mg atom into Al lattice during milling was significant. By milling for 10 h the dramatic increase in microhardness (155 HV) for Al-Mg matrix nanocomposite was caused by grain refinement and solid solution formation. From 10 to 20 h, slower rate of increasing in microhardness may be attributed to the completion of alloying process, and dynamic and static recovery of powders.     

Morphology and structure of LiNb0.6Ti0.5O3 particles by molten salt synthesis

M-phase LiNb_0.6Ti_0.5O₃ (LNT) plate-like particles with large anisometric shape were firstly fabricated by molten salt synthesis (MSS) method in LiCl flux. Effects of reaction temperature, holding time and the weight ratio of LiCl salt to the original powders on the phase structure and morphology of the synthesized particles were investigated. The LiNb_0.6Ti_0.5O₃ powders generally showed a multi-layer structure, exhibiting irregular hexagonal or triangle morphology. The reaction temperature showed a strong influence on the particle growth process, and pure LNT particles are obtained at 950 °C. Further increasing the reaction temperature and holding time could increase the average size of the particles. It revealed that the thickness of the plat-like particles was increased as the contents of the chloride salts increased. The synthesis process, the relation between crystal structure and morphology of particles were also discussed.     

Electrodeposition and characterization of silane thin films from 3-(aminopropyl)triethoxysilane

3-(aminopropyl)triethoxysilane based films have been electrodeposited directly on polycrystalline gold and gold (111) electrodes in aqueous 3-(aminopropyl)triethoxysilane based electrolyte and in tetrahydrofurane based electrolyte. These films were characterized by means of IR-ATR and X-ray photoelectron spectroscopies. The film morphology was investigated by scanning tunneling microscopy while the film growth was observed by ellipsometry measurements. The vibrationnal and X-ray photoelectron analysis suggest that the chemical composition of the electrodeposited films either in liquid tetrahydrofurane or in liquid 3-(aminopropyl)triethoxysilane is identical. The resulting coating thickness is different for the same biasing time in the two liquid media. The gold surface is coated irreversibly by an amino terminated film of great interest for sensor applications which was used as the functionalized part of a surface plasmon resonance biosensor to monitor α-lactalbumin graft.     

Structural, dielectric and piezoelectric properties of aluminium doped PLZT ceramics prepared by sol–gel route

Nanosized piezoelectric ceramics for vibration sensor applications have been prepared by mixing the ferroelectric PLZT (8:60:40) with variable doping fractions of trivalent aluminium ion (Al³⁺). Samples have been prepared through a standard sol–gel route. X-ray diffraction and scanning electron microscopy (SEM) have been used to determine the phase and morphological modifications. Transmission electron microscopy (TEM) studies reveal the microstructure with nanosized well-dispersed homogeneous spherical particles. The vibrational infra-red (IR) spectroscopy record is taken to locate the position of the doping Al³⁺ ion. Using electrical impedance spectroscopy, the resonance and anti-resonance frequencies of the Al modified PLZT system have been determined and analysed. Al addition in PLZT has left a profound effect in its dielectric and piezoelectric properties. An interpretation of the role of Al addition is proposed in terms of structure modification. The sensing power of the investigated material was found useful for the vibration control of a cantilever beam.     

Preparation by gravity casting and hydrogen-storage properties of Mg–23.5 wt.%Ni–(5, 10 and 15 wt.%)La

Mg–23.5 wt.%Ni–(5, 10 and 15 wt.%)La alloys were prepared by gravity casting and their hydrogen-storage properties were examined after pulverizing. The gravity cast Mg–23.5Ni–(5, 10 and 15)La alloys consist of α-Mg, Mg₂Ni and Mg₁₇La₂ phases. The activated Mg–23.5Ni–10La alloy has the highest hydrogen-storage capacity of 4.96 wt.%H (from P–C–T curve) and the highest initial hydriding rate (hydrogen content 3.83 wt.%H at 10 min) with an initial hydrogen pressure in the channel of 11 bar H₂ at 573 K. This is attributed to its containing the largest amount of the Mg₁₇La₂ phase, which is easily dissociable during the hydriding reaction.     

Synthesis, characterization and electrical properties of CdI2 doped Al2O3 and TiO2 superionic conductors

Superionic conductors were prepared by admixing metallic oxides (alumina and titania) with cadmium iodide in different proportions using direct mixing method. The synthesized materials were characterized by various qualitative techniques such as XRD (X-ray diffraction), DSC (differential scanning calorimetry) and SEM (scanning electron microscopy). Pure CdI₂ shows the standard pattern which corresponds to β-phase stable at room temperature, however, the diffractograms of the mixtures shows two phase nature of the materials with no effect of the second phase on the peak positions of the first, i.e. CdI₂. DSC curves also confirmed the formation of composite. SEM micrographs show the presence of great number of space charge regions which are very important in creating a great number of surfaces which in turn act as additional sources of point defects. It was also found that the conductivity of CdI₂ increases with mole fractions of dopants till x = 0.5 for alumina and x = 0.3 for titania. Arrhenius equation was used to study the temperature dependence of electrical conductivity and the activation energy of pure cadmium iodide was found to be 0.792 eV.     

凝胶-燃烧法合成(Y,Gd)Al3(BO3)4:Tb3+荧光材料的结构及其发光性能

采用凝胶-燃烧法合成掺Tb3+和Gd3+的四硼酸铝钇(Y,Gd)Al3(BO3)4:Tb3+荧光粉.分别采用X射线衍射仪(XRD)、扫描电镜(SEM)、发光光谱等测试手段分析不同温度下煅烧所得粉体的物相、形貌与发光性质.XRD和SEM结果表明:(Y,Gd)Al3(BO3)4:Tb3+的最低合成温度为1000 ℃,在该反应过程中,首先形成中间相Al4B2O9、YBO3和Y3Al5O12,而最终形成单相的(Y,Gd)Al3(BO3)4:Tb3+.随煅烧温度的升高,样品结晶程度越来越好,并且颗粒尺寸随温度的升高而增大,在1100 ℃时合成的晶粒尺寸比较均匀,平均粒径在1 μm左右.发光光谱的测试结果表明:在229 nm激发下,(Y,Gd)Al3(BO3)4: Tb3+荧光粉最强发射峰位于542 nm处,属于Tb3+的5D4→7F5的跃迁.在该体系中存在Gd3+→Tb3+的能量传递,使得该荧光粉的发光强度随着Gd3+掺杂浓度的增加而增大.     

Low-temperature synthesis and characterization of (Zn,Ni)TiO3 ceramics by a modified sol–gel route

Hexagonal ilmenite-type (Zn_1−xNi_x)TiO₃ (x = 0, 0.85–1.0) ceramic powders were successfully synthesized by a sol–gel route with low temperature (800 °C) sintering, which was modified by using the two-step heat treatment so as to obtain pure products. The thermal stability of the hexagonal (Zn,Ni)TiO₃ was enhanced with the increasing amount of nickel addition. FE-SEM observations demonstrated that the average crystallite sizes of (Zn_1−xNi_x)TiO₃ remarkably decreased from more than 200 nm to less than 100 nm with the increasing solubility x. The dielectric properties of (Zn_1−xNi_x)TiO₃ were measured at different frequencies and the results showed that there existed maximum values both for the dielectric constants and the loss tangents at x = 0.85.