Effect of laser‐induced nanocrystallisation on the properties of electroless Ni‐P/Ni‐W‐P duplex coatings

This paper presents a comparative study of nanocrystallisation and the wear resistance of electroless plated Ni‐P/Ni‐W‐P duplex coatings with a single Ni‐W‐P coating before and after high‐ power diode laser treatment. Effects of the laser operating parameters on microstructures, in terms of crystallisation, porosity formation, phase transformation and grain growth, were investigated using scanning electron microscopy (SEM) with energy dispersive X‐ray spectroscopy (EDX) and quantitatively X‐ray Diffraction (XRD). Microhardness and wear behaviour of the coatings before and after laser treatment were evaluated by measurement of coating surface and cross‐section hardness as well as un‐lubricated friction and wear tests. The results revealed that in the case of laser treatment, the Ni‐P/Ni‐W‐P duplex coatings offered better wear resistance than the single Ni‐W‐P coating, while the as‐plated, single Ni‐W‐P coating showed better wear resistance than the Ni‐P/Ni‐W‐P duplex coatings. Adhesive wear mechanism prevails in the laser‐treated coatings when subjected to wear test against hardened steel material. The effects of microstructural characteristics in the coatings, in particularly the grain size of Ni₃P phase and the degree of crystallisation, on the adhesive wear behaviour have been investigated and found to be dominant besides the effect of hardness.     

Organic–inorganic hybrid coatings for corrosion protection

The corrosion resistance of sol–gel derived, organic–inorganic, silica-based hybrid coatings with various amounts of organic content was studied. Hybrid sols were prepared by copolymerizing tetraethylorthosilicate (TEOS) and 3-methacryloxypropyltrimethoxysilane (MPS) with a two-step acid-catalyst process. Hybrid coatings were dip-coated on 304 stainless steel substrates and annealed at 300 °C for 30 min. Such prepared hybrid coatings were found to be relatively dense, uniform and defect free. The adhesion and flexibility of the coatings were characterized. The influences of the amount of organic component incorporated into the coatings and the aging of sols on corrosion protection were studied. Electrochemical analyses showed that the relatively dense hybrid coatings provided excellent corrosion protection by forming a physical barrier, which effectively separated the anode from the cathode. Some preliminary biocompatibility tests were also conducted on the hybrid coatings.     

Synthesis of ZnO nanorods by the thermal reduction process of a mixture of ZnO and Al powder

Single‐crystalline Zinc oxide (ZnO) nanorods were firstly synthesized on gold‐coated Si substrate via a simple thermal reduction method from the mixture of ZnO and Al powder. The growth process was carried out in a quartz tube at different temperature (550‐700 °C) and at different oxygen partial pressure. Their structure properties were investigated by X‐ray diffraction (XRD), scanning electron microscope (SEM), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The length of the as‐prepared ZnO nanorods was up to several micrometers and their diameters were about 130 nm. The X‐ray diffraction patterns, transmission electron microscopic images, and selective area electron diffraction patterns indicate that the one‐dimensional ZnO nanorods are a pure Single‐crystal and preferentially oriented in the [0001] direction. The reaction mechanism of ZnO nanorods was proposed on the basis of experimental data. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fe_3Al金属间化合物的机械合金化制备

采用钢球为研磨球,以单质Fe、Al为原料,对不同配比的Fe-Al混合粉体在无保护气氛和非真空条件下进行机械球磨,获得了Fe(Al)超饱和固溶体,对其进行真空退火制备了Fe3Al金属间化合物。XRD和DSC分析表明:在球磨大约10 h以后,粉体中单质Al的数量开始减少,且随着球磨时间的延长,这种趋势更加明显;球磨80 h后,粉体中单质Al已全部固溶于Fe中,形成了Fe(Al)超饱和固溶体。这说明在无保护气氛和非真空条件下机械合金化法可以制得较纯的Fe3Al金属间化合物。     

Effect of substrate temperature on structural and materials properties of zirconium nitride films on D9 steel substrates

Thin zirconium nitride (ZrN) films were prepared by using reactive direct current (DC) magnetron sputtering onto D9 steel substrates. XRD technique was employed to study the coatings, observing variations of crystallite size, crystallite texture and lattice constant, as a function of substrate temperature. Chemical states of the ZrN thin films were determined by X‐ray photoelectron microscopy (XPS). AFM picture showed the presence of spherical shaped grains on the top of homogeneous granular surface. The hardness and elastic modulus values were measured by nanoindendation and their values are 18.5 and 343 GPa respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic properties and X‐ray photoelectron spectroscopy of nanocrystalline Ho3Al5O12

Nanocrystalline holmium aluminium garnet (Ho₃Al₅O₁₂) has been prepared for the first time by modified Pechini's reaction after sintering the precursor gel at 1223 K. The nanomaterial has been characterized by X‐ray diffraction (XRD), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The XRD pattern confirms the formation of single‐phase Ho₃Al₅O₁₂; the average size of the nanoparticles has also been determined. X‐ray photoelectron spectroscopy (XPS) has been used to study the chemical composition and bonding in the as‐prepared samples. The binding energies of core‐level electrons in Ho, Al and O in the title material have been found slightly shifted compared to the values of the respective elements. DC magnetic susceptibility has been measured in the temperature range 2 – 260 K. Low effective magnetic moment of Ho³⁺, μ_eff = 1.35 µ_B and Weiss constant have been derived from the inverse magnetic susceptibility–temperature linear plot. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microstructural and optoelectrical properties of transparent conducting ZnO:Al thin films for organic solar cells

The Al‐doped zinc oxide (ZnO:Al) thin films were grown on glass substrates by the magnetron sputtering technique. The films were characterized with X‐ray diffractometer, four‐point probe and optical transmission spectroscopy, respectively. The dependence of microstructural, electrical and optical properties on deposition temperature was investigated. The results show that all the films have hexagonal wurtzite structure with highly c‐axis orientation. And the microstrural and optoelectrical properties of the films are observed to be subjected to the deposition temperature. The ZnO:Al film prepared at the deposition temperature of 650 K possesses the best optoelectrical properties, with the lowest electrical resistivity (6.1×10⁻⁴ Ω·cm), the highest average visible transmittance (85.3%) and the maximum figure of merit (0.41 Ω⁻¹). The optical energy gap of the films was estimated from Tauc's law and observed to be an increasing tendency with the increment of the deposition temperature. Furthermore, the refractive index of the films was determined by the optical characterization methods and the dispersion behavior was studied by the single electronic oscillator model.     

The effect of alloying elements on the crystallization behaviour and on the properties of galvanized coatings

The influence of the alloying elements on the interface reactions of zinc coatings during the galvanization process was examined. These reactions affect the crystallization and the structure and properties of the outer layer of the coatings. Depending on the type and concentration of the alloying additions in the galvanizing bath differences were induced in the crystallization process of the Fe‐Zn phases. It was found that both the concentration and the distribution of the alloying elements played an important role in the growth of the phases. The formation of the phases and the distribution of the alloying elements in the coatings were determined using X‐Ray diffraction (XRD) and Scanning Electron Microscopy (SEM) associated with an Energy Dispersive X‐Ray Spectroscopy (EDS) analysis. Finally the behaviour of the galvanized coatings was examined under accelerated salt spray corrosion conditions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characterization of reactive DC magnetron sputtered TiAlN thin films

Thin films of about 1μm Titanium Aluminum Nitride (TiAlN) were deposited onto mild steel substrates by reactive direct current (DC) magnetron sputtering using a target consisting of equal segments of titanium and aluminum. X‐ray diffraction (XRD) analysis showed that the TiAlN phase had preferred orientations along 111 and 200 with the face‐centered cubic structure. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) analyses indicated that the films were uniform and compact. Photoluminescence (PL) spectra reveal that TiAlN thin films are of good optical quality. Laser Raman studies revealed the presence of characteristic peaks of TiAlN at 312.5, 675, and 1187.5 cm^–1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

AES and FTIR characterization of sol–gel alumina films

In this work we obtained sol–gel alumina coatings on AISI 304 stainless steel substrates. Alumina sols were prepared by using aluminum isopropoxide (AI) as precursor, acetic acid (HOAc) as catalyst, ethanol (C₂H₅OH) or isopropanol (C₃H₈O) as solvent, and water. The as-prepared solutions were deposited on stainless steel substrates by means of the dip-coating technique. The obtained composites were characterized by Fourier transform infrared spectroscopy (FTIR) and Auger electron spectroscopy (AES). We observed that the concentration of AlO type bonds in the obtained alumina coatings depends on the solvent type used, temperature and peptization state of the sol, withdrawal speed, and number of dipping cycles. AES experiments showed that the interface formed between the alumina coating and substrate surface is in general formed by several layers of different chemical compositions.     

Crystallisation and performance characteristics of high‐temperature annealed electroless Ni‐W‐P coatings

Electroless deposition of Ni–P based alloys is a well‐known commercial process that has numerous applications because of their excellent anticorrosive and wear properties. However, for some special occasions, like the components for gas making furnaces in chemical fertiliser industry, the coatings must be reinforced to withstand short‐term high temperatures between 600 °C and 700 °C as well as light erosive wear. Therefore, co‐deposition of high melting point metallic element, W, has been considered as a preferred choice. In the present study, two Ni–W–P alloy coatings were deposited on mild steel panels from different alkaline baths. The microstructures of the annealed coatings were characterised by quantitative XRD, XPS and SEM/EDS analysis techniques and their microhardness, friction and wear behaviour, corrosion mechanism as well as microstrain and residual stress are discussed in comparison with the as‐plated state. The results indicate that the hardness mainly depends on the volume fraction and crystallite size of Ni₃P phase; the uniform corrosion in sulfuric acid solution is closely related to the ratio of I_Ni/I_Ni3P as well as grain size. The wear mechanism of the high‐temperature annealed coating is dominated by abrasive wear, but the wear in the early stages started from mild adhesive wear caused by adhesion between the friction couples. Electroless deposited Ni‐W‐P alloys with high phosphorus present relatively good properties, including hardness, wear and corrosion resistance when 700 °C is applied for annealing process.     

Effect of substrate temperature on the properties of reactively sputtered TiN/NbN multilayers

TiN/NbN multilayer coatings were deposited with various substrate temperatures by DC reactive magnetron sputtering method onto Si (111) and glass substrates. The effect of substrate temperature on the structural and optical properties of TiN/NbN multilayers was investigated by X‐ray diffraction, X‐ray photoelectron spectroscopy, Field emission scanning electron microscopy and Photoluminescence measurements. The composition was analyzed by X‐ray photoelectron spectroscopy. X‐ray diffraction results showed that the layers crystallized in cubic structure for TiN and hexagonal structure for NbN. It was found that grain size increased with increase in substrate temperature. The surface morphology of the TiN/NbN thin films showed a dense and smooth surface with substrate temperature upto 200 °C but after 300 °C, the grains became larger and coarse surface was observed. The TiN/NbN multilayer coatings exhibited the characteristic peaks centered at 180, 210 and 560 cm^‐1. Red band emission peaks were observed in the wavelength range of 700‐710 nm. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Properties of Co‐doped ZnO films prepared by electrochemical deposition

We prepared Co‐doped ZnO films by the electrochemical deposition. X‐ray diffraction (XRD), high resolution transmission microscopy (HRTEM), x‐ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), x‐ray absorption near‐edge structure (XANES), vibrating sample magnetometer (VSM), optical absorption, and photoluminescence (PL) measurements were carried out on the samples. The results showed Co atoms substituted Zn atoms in the ZnO lattice without the formation of the impurity phase. VSM measurements showed the ferromagnetic properties for the Co‐doped ZnO samples. When the Co doping concentration increased, the band gaps were widened and the PL peak positions shifted towards the short wavelength direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Formation of boride layers on steel substrates

Boronizing coatings were prepared by means of pack cementation technique. It was found that using the appropriate substrate and controlling parameters of the boribing process such as boron activity of the mixture, temperature and time of treatment, it is possible to obtain a structure predominantly consisting of the Fe₂B phase. In the present study low alloy ferritic steels were chosen as substrates. Changing the boron carbide concentration in the mixture and the temperature and time of boronizing process the conditions of the boronizing were altered. As a result the formation of the Fe₂B phase is enhanced. Characterization of the as‐borided steels is discussed based on X‐ray diffraction and Curie temperature measurements. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Properties of InAs co‐doped ZnO thin films prepared by pulsed laser deposition

InAs co‐doped ZnO films were grown on sapphire substrates by pulsed laser deposition. The grown films have been characterized using X‐ray diffraction (XRD), Hall effect measurements, Atomic force microscope (AFM) and Field emission scanning electron microscope (FESEM) in order to investigate the structural, electrical, morphological and elemental properties of the films respectively. XRD analysis showed that all the films were highly orientated along the c‐axis. It was observed from Hall effect measurements that InAs co‐doped ZnO films were of n‐type conductivity. In addition, the presence of In and As has been confirmed by Energy dispersive X‐ray analysis. AFM images revealed that the surface roughness of the films was decreased upon the co‐doping. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature dependence of growth orientation and surface morphology of Li‐doped ZnO thin films on SiO2/Si substrates

ZnO thin films doped with Li (ZnO:Li) were deposited onto SiO₂/Si (100) substrates by direct‐current sputtering technique in the temperature range from room temperature to 500 °C. The crystalline structure, surface morphology and composition, and optical reflectivity of the deposited films were studied by X‐ray diffraction (XRD), Scanning Electron Microscopy (SEM), X‐ray Photoelectron Spectroscopy (XPS) and optical reflection measurements. Rough surface p‐type ZnO thin film deposition was confirmed. The results indicated that the ZnO:Li films growed at low temperatures show c‐axis orientation, while a‐axis growth direction is preferable at high temperatures. Moreover, the optical reflectivity from the surface of the films matched very well with the obtained results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

稀土强化Al2O3/Ti(C,N)陶瓷材料的组分设计及其使用性能研究

以稀土强化Al2O3/Ti(C,N)陶瓷材料为基础,进行了基于抗冲击性能、抗热震性能和耐磨性能的组分设计.结果发现,与最佳的抗冲击性能、抗热震性能和耐磨性能相对应,弥散相Ti(C,N)的最优体积含量分别为27.7;、26.5;和30.7;,其最优性能分别比纯Al2O3陶瓷提高约71.4;、40.4;和28.9;.在此基础上,实验研究了稀土强化Al2O3/Ti(C,N)陶瓷材料用于刀具时的切削特性.表明该材料具有良好的耐磨性能,可以作为刀具材料使用.     

Structural and morphological studies on Mn substituted ZnO nanometer‐sized crystals

Mn substituted ZnO nanocrystals synthesized by a co‐precipitation method. X‐ray diffraction (XRD) studies confirms the presence of wurtzite (hexagonal) crystal structure similar to un doped ZnO, suggesting that doped Mn ions go at the regular Zn sites. The lattice parameters a and c are increasing with increasing Mn content. The unit cell volume increases with increasing Mn concentration, indicating the homogeneous substitution of Mn²⁺ for the Zn²⁺. The lattice distortion parameter (ε_v) is evaluated from XRD data and found that it enhances as Mn content increases. Transmission electron microscopy photographs show that the size of the ZnO crystals is in the range of 20‐50 nm. The SAED pattern confirms the hexagonal and crystalline nature of the samples which are in agreement with X‐ray analysis. The chemical groups of the samples have been identified by FTIR studies (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mott‐hopping processes in neodymium oxide thin films prepared on Si(100) substrates

Thin Nd oxide films were prepared on Si (P) substrates to form MOS structure. The oxide films were annealed at different conditions and their crystal structures were determined by X‐ray diffraction (XRD). The dc electrical transport properties of the devices with amorphous and crystalline Nd oxide were investigated. The current‐temperature J(T) characteristics suggest that the carrier transport through the insulator follows Mott's variable‐range hopping (VRH) mechanism and its results were compared with the results obtained from X‐ray diffraction. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

镁合金表面制备Al2O3/Ni复合涂层抗腐蚀性的研究

为了改善镁合金的抗腐蚀性,用电泳沉积法在AZ91D镁合金表面沉积两种不同比例的Al2O3/Ni复合涂层.在干燥器皿中放置12h后,放入真空烧结炉中,在300℃下保温4h.通过X射线衍射,扫描电子显微镜和能谱仪对涂层的形貌,物相和微观结构进行分析;将试样浸泡在3.5wt;的NaCl溶液中,通过电化学极化曲线和阻抗谱对涂层的抗腐蚀性进行测试.结果显示,与纯Al2O3涂层相比,Al2O3/Ni复合涂层由于添加了Ni,涂层孔隙率降低,同时降低了涂层与基底热膨胀系数的不匹配程度,提高了结合强度.在四种不同比例的涂层中,Al2O3与Ni质量比为1:3的复合涂层,表面结构更加均匀致密化,涂层的抗腐蚀性能最好.