Spray-Deposition of an Organic/Inorganic Blend for Fabrication of a Superhydrophobic Surface: Effect of Admixing with Silica Aerogel and Modified Silica Nanoparticles

Superhydrophobic and self-cleaning glass slides were fabricated using a facile and low-cost method through spray-coating of four types of blends consisting of stearic acid, the mixture of stearic acid and SiO₂ nanoparticles, the mixture of stearic acid and SiO₂ nanoparticles modified with oleic acid, and the mixture of stearic acid and SiO₂ aerogel onto the surface. The nanocoated surfaces were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and water contact angle (WCA) measurements. The results have shown that the mixture of stearic acid and SiO₂ nanoparticles modified with oleic acid coating possessed the highest contact angle of about 158.6° and a low sliding angle while the mixture of stearic acid and SiO₂ aerogel had an almost similar WCA but with a more satisfactory durability. In contrast, the stearic acid coating alone had a hydrophobic property and the mixture of stearic acid and unmodified SiO₂ nanoparticles showed superhydrophobic properties without any self-cleaning and durability features.

     

Laser-induced enhancement of the surface hardness of nanoparticulate TiO2 self-cleaning layer

We here report that the abrasion resistance of nanoparticulate TiO₂ self-cleaning layers can be highly enhanced without a considerable loss of photocatalytic capability. TiO₂ coating layers solution-deposited onto the glass substrate were irradiated by a pulsed ultraviolet (UV) laser at 355 nm, which modified the surface morphologies via laser-induced local melting of TiO₂ nanoparticles. The surface hardness, measured by pencil scratch test, improved with increasing laser power (P). While an unmodified TiO₂ layer revealed a hardness of 6B, it increased to 2H after the surface was irradiated at P = 0.3 W. Almost all of the stearic acid deposited on an unmodified sample disappeared after UV exposure for 12 h. The photocatalytic decomposition was slowed down on laser-irradiated TiO₂ surfaces and this is attributed to the reduction of specific surface areas as a result of the morphological modifications. However, a TiO₂ layer hardened to 2H still exhibited fairly good photocatalytic activity, decomposing more than 75% of the stearic acid after exposure for the same duration.     

Electrolytic plasma processing for cleaning and metal-coating of steel surfaces

Electrolytic plasma processing (EPP) involves electrolysis and electrical discharge phenomena and it is an emerging, environmentally friendly surface engineering technology. Electrolytic-plasma/material surface interactions during processing can be used for cleaning of metal surfaces, formation of diffusion layers and/or deposition of metal, ceramic and composite coatings. The present work was concerned with cleaning and deposition of metal coatings on steel surfaces for corrosion protection. The effects of processing parameters on (i) cleaning steel surfaces (oxides and contamination); and (ii) Zn and Zn–Al coating deposition were investigated. Surface roughness and oxygen content prior to and after cleaning were evaluated by profilometry and energy dispersive X-ray analysis (EDAX), respectively. The structure of the EPP cleaned outer surface layer as it evolves after the electrolytic–plasma interaction was studied by high resolution TEM. Morphology, microstructure, composition, adhesion and density of EPP-deposited Zn and Zn–Al coatings on cleaned surfaces were studied as a function of processing parameters. Corrosion properties of the cleaned and coated steels were evaluated by corrosion potential and potentiodynamic polarization measurements. The results show that EPP can effectively produce clean surfaces and also metal and alloy coatings at high deposition rates, and it has a great potential as a new plasma surface engineering technique.     

The effect of an atmospheric pressure plasma treated MgO layer on the discharge performance of an AC plasma display panel

The effect of an atmospheric pressure plasma treated MgO layer on the discharge performance of an alternating current plasma display panel (AC PDP) was investigated by measuring the contact angle, the surface roughness, the composition, the breakdown and sustaining voltages. The plasma cleaning was performed using the He/O₂/Ar gas mixture. Higher contact angle (35°) of water droplet on the MgO surface and the MgO surface roughness (90 nm, R_max) after one day duration in the air was significantly reduced to 4° and 54 nm (R_max) after the plasma cleaning. After the plasma treatment, the adsorbed CO₂, CO, H₂O impurities on the MgO surface are effectively removed. The breakdown and sustaining voltages were reduced probably due to the increase of secondary electron emission coefficient of MgO, implying that the plasma cleaning process of the MgO layer is beneficial for the improvement of the discharge performance of the AC PDPs.     

PAS consolidating behavior of mechanically alloyed nanocrystalline NiAl intermetallic compound

In this study, nanocrystalline NiAl intermetallic compound was obtained by mechanical alloying and PAS (plasma activated sintering method). Nanocrystalline NiAl powder was fabricated after 30 hr of milling with 2 wt.% stearic acid added as a PCA (process control agent) to the Ni-50at%Al composition. The grain size of the nanocrystalline NiAl powder was about 10 nm. Nanocrystalline NiAl powder was consolidated at 1000°C, 1100°C, 1200°C and 1300°C for 2 min with 30 MPa compressive force. The surface morphology of the NiAl consolidated at 1300°C was very regular and dense, above 96% of theoretical density (5.9 g/cm³). Al₄C₃ was observed in the NiAl consolidated at 1300°C by TEM analysis. It is thought that the carbons came from the stearic acid during the MA process and the graphite mold during the PAS process. The grain size of the NiAl consolidated at 1300°C did not increase but the grain shape became flat due to compressive force.     

Surface pretreatment of austenitic stainless steel and copper by chemical, plasma electrolytic or CO2 cryoblasting techniques for sol-gel coating

The surface pretreatments of the austenitic stainless steel and copper surfaces for the sol-gel coating were carried out by chemical, plasma electrolytic or CO₂ cryoblasting techniques. With the austenitic stainless steel the smoothest surfaces were obtained with plasma electrolytic cleaning, after which the measured contact angles of water were clearly decreased revealing improved hydrophilicity. As well with the copper samples the smooth surface and improved hydrophilicity was obtained with the plasma electrolytic cleaning, but oxide layer formed to the copper surface immediately after the treatment. CO₂ cryoblasting provided rough surface with wetting properties close to the original surface both for austenitic stainless steel and copper surfaces. CO₂ cryoblasting provided best appearance for the copper surface because no oxidation happened with that treatment. XPS and SIMS studies showed that with the plasma electrolytic treatment the surface layer of the austenitic stainless steel enriched of chromium and the oxide layer formed on the surface was less than 10 nm thick. With the chemical cleaning and CO₂ cryoblasting, the chromium enrichment to the stainless steel surface was less. However XPS and SIMS studies showed that chemical treatment provided thinner oxide layer to copper surface than plasma electrolytic treatment.     

Preparation of nano- and microstructured gold surfaces by application of a square wave potential regime

Gold nanometallic structures have been prepared by application of square wave potential regime to a platinum electrode in a 1.0 × 10^?3 M HAuCl₄ + 0.5 M H₂SO₄ solution. Formation of gold particles onto the platinum surface has been followed by cyclic voltammetry, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The results indicate that the size, shape, uniformity of distribution of the particles are affected by the selected parameters of the applied square wave potential regime. Parameters of the square wave include the frequency, the lower and the upper limits of the square wave and the time of application of the square wave potential regime. The concentration of HAuCl₄ in the solution is another important factor. The results of the present work indicated that the 100 Hz frequency is the optimal frequency for obtaining gold nanoparticles on platinum surface. Deposition time has been also found to play a critical role in affecting the size, shape and homogeneity of gold nanostructures at the surface. The surface coverage with nanoparticles as calculated from the decrease in the charge of hydrogen adsorption/desorption peaks is found to be directly proportional to the time of application of the square wave. Testing the nanostructured gold/Pt electrode for oxidation of formic acid shows its higher catalytic activity than that of platinum and gold plain electrodes.     

铝合金表面有机污染物等离子体清洗机理及验证

针对惯性约束核聚变装置中铝合金零件表面的有机污染去除问题,提出大气常压等离子清洗方式。 通过有限元方法研究等离子清洗机理,并通过铝合金零件的清洗试验进行验证,从而实现聚变装置中机械零件的超洁净制造。 研究结果表明:通过建立等离子表面清洗的热力学耦合方程,仿真分析得到清洗应力随清洗距离的减小而增大, 随清洗速度和基体厚度的增大而减小。 通过试验验证了铝合金零件在等离子清洗后表面自由能增大,极性分量与色散分量都有所增加,并且在等离子清洗过程中清洗的距离比清洗速度对清洗效果影响更大,清洗距离为 5 mm 时最好。     

Influence of ceramic thickness on residual stress and bonding strength for plasma sprayed duplex thermal barrier coating on aluminum alloy

NiCoCrAlY/8wt.%Y₂O₃–ZrO₂ coating was plasma sprayed on aluminum alloy to evaluate the effect of ceramic thickness on residual stress and bonding strength. A new stress calculation method based on Stoney equation and substrate-removal technique was proposed. Stress in both bond coat and ceramic was studied. With the increase of ceramic thickness, the residual stress in both layers was firstly compressive then turned tensile. The large thermal expansion coefficient of the substrate played an important role in residual stress formation when the ceramic was thin. However, the intrinsic deposition stress took a dominant position when the ceramic coating turned thicker. The bonding strength decreased and the location of the fractured surface moved toward the ceramic surface. The moving of the surface was mainly resulted from the variation of stress gradient and the weakness of high porosity zone near the bond coat–ceramic interface.     

Conversion coating growth on 2024-T3 Al alloy. The effect of pre-treatments

The cleaning pre-treatments, generally based on alkaline etching and acid pickling, provide a surface standard condition before the application of conversion coatings. In this work, the effect of cleaning pre-treatments on the surface morphology and activity of 2024-T3 Al alloy and on chromium-free Ce-based conversion coatings formation has been studied. Variations in the open circuit potential of the alloy of ~ 1.5 V were registered during the cleaning pre-treatment, accounting for the complex electrochemical phenomena involved. Even though, the presence and concentration of additives such as H₂O₂ was found to be essential to a fast kinetics coating formation, effective cleaning pre-treatments are demonstrated to be associated to the production of grained well structured coatings, allowing necessary redox reactions for conversion coating formation. The effect of copper-rich areas and its effect on the conversion coating growth rate and morphology were also studied using benzotriazole additions at different stages in the cleaning pre-treatments.     

硬脂酸微波反应制备焊条抗吸潮保护膜

碱性焊条容易因吸潮而引起焊缝扩散氢增加,采用在焊条表面进行微波反应的方法制备了抗吸潮保护膜.将烘干的焊条放入溶有一定量硬脂酸和Fe3O4粉末的石油醚溶液中,取出后进行微波反应,使焊条表面具有抗吸潮性能.用红外光谱仪和扫描电镜对焊条保护膜的成分和形貌进行了分析,并进行了熔敷金属扩散氢测试.结果表明,Fe3O4能融化硬脂酸...     

镀铝衍射光栅表面有机污染物的等离子体清洗技术

高能量激光装置中衍射光栅吸附的有机污染物是导致衍射光栅损伤的关键因素之一,采用等离子体清洗技术可以实现衍射光栅表面污染物的在线去除。通过有限元方法分析等离子体清洗范围,获得等离子体清洗半径随着清洗距离下降而增加的规律。研究等离子体清洗工艺参数与表面有机污染物去除效果间关系,结果表明随着清洗距离以及工艺气体中氧气含量的上升,镀铝衍射光栅表面自由能的极性部分和色散部分都会增加,其中极性部分的增加起主导作用。等离子体清洗后的镀铝衍射光栅表面呈现洁净状态的周期性锯齿形结构,并且C1s(285.0eV)峰值由6.65×10⁴降低至2.86×10⁴。研究等离子体清洗镀铝衍射光栅后表面自由能变化情况,结果表明镀铝衍射光栅表面的极性基团会吸附空气中的碳氢化合物,出现表面自由能下降的陈化现象。研究结果可为镀铝衍射光栅表面有机物污染物的等离子体在线去除提供新的途径。     

Superhydrophobic Surface of AZ31 Alloy Fabricated by Chemical Treatment in the NiSO<Subscript>4</Subscript> Solution

In the present study, the formation of superhydrophobic (SHP) structure on the surface of Mg alloy was investigated by immersion in the CuCl₂ and NiSO₄ solutions following by soaking in the stearic acid (SA) solution. The results revealed the presence of some stearic acid bonds on the surface of Mg alloy. The contact angle of the surface after the process measured about 151.5°, which could be due to the presence of flake-like morphology and the adsorption of hydrophobic substances of SA. X-ray diffraction pattern showed the presence of NiO as the resistant phase against the diffusion of species. Besides, the values of noise and corrosion resistance regarding SHP Mg were at least three orders of magnitude higher than that of bare Mg alloy due to the formation of SHP structure.     

Morphology and electrical contact properties of electrical connection materials in corrosive atmosphere

The impact mechanism of environmental factors, such as corrosive atmosphere, on connector materials was investigated, and the porosity of gold plating was tested. Series of inspections and analytical research methods were introduced in this article. The surface morphology of specimens after corrosion was observed by stereoscopic microscope and scanning electron microscope. Chemical constitution was examined by X-ray energy spectrum. The contact resistances were measured by four-point method. The experiment results show that after exposure to certain environment, the corrosion products, such as Cu2O, Cu(NO3)2·3H2O, and NiO, are observed on the surface of the specimens without gold coatings, whereas the corrosion products appear to have circle-shaped spots on gold-plating surface after corrosion test, which indicate that the gold plating has good corrosion protection. The porosity is increased with the increase of corrosion time for every kind of specimens gold plated, and the corrosion degree of goldplating specimens is decreased with the increase of the thickness of gold coatings. The static contact resistances of circle-shaped spots appear higher contact resistance than normal value, which can reach to 2,000 mX nearly. It is found that the high and unstable contact resistance of the pore and products is more likely to cause contact failure.     

The role of recombination in formation of charge composition of ions in a laser plasma upon mass spectrometric analysis of solids

A numerical experiment is used to study expansion of a plasma cloud with complex composition into a vacuum. Under the assumption that the density and temperature of the laser plasma are homogeneous throughout the cloud, the system of differential equations describing the plasma cloud expansion with allowance for inelastic processes is reduced to a system of ordinary differential equations for ions of five elements (Fe, Mn, Cr, Ni, Mo) with the charges z = 1, 2, 3, 4. The velocity of the plasma cloud boundary and its temperature as functions of the expansion time are determined. It is demonstrated that, after recombination stops, thermodynamically nonequilibrium plasma is created as a result of “quenching,” and in this plasma the residual degree of ionization and ion charge distribution depend on the initial plasma parameters T₀, N₀, and R₀. In the course of recombination, the dependence of ion charge distribution on ionization potential weakens.     

Application of heterogeneous gold catalysis with increased durability: Oxidation of CO and hydrocarbons at low temperature

2% Au/Al₂O₃ catalysts were prepared by a novel method involving Direct Anionic Exchange (DAE). The method produces strong bonding of the gold complex (HAuCl₄) to the alumina support with no loss of gold during the subsequent steps of preparation. The complete removal of chloride from the catalyst was achieved by washing with concentrated ammonia. This procedure ensures a better activity and prevents sintering during calcination as shown by TEM. The catalysts were tested for the oxidation of CO and of saturated and unsaturated hydrocarbons (C₁ to C₃). The catalysts showed high activities over a range of concentrations and temperatures relevant to applications in automotive exhaust cleaning. Furthermore, a remarkable resistance to thermal ageing at 600°C in the absence or presence of water was observed, due to the presence of the strongly anchored nanosized gold particles obtained during the preparation step.     

Novel plating solution for electroless deposition of gold film onto glass surface

In this paper, a simple and environmentally friendly electroless plating solution of chloroauric acid (HAuCl₄) and hydrogen peroxide (H₂O₂) for depositing gold film onto (3-aminopropyl)-trimethoxysilane (APTMS) -coated glass surface has been developed. APTMS as an adhesive reagent was used to attach the gold nanoparticles (AuNPs) onto the glass substrate. These AuNPs could be regarded as the preferential nucleation or catalytic sites for gold electroless reduction, which accelerated the reduction of Au³⁺ on the glass surface and effectively prevented the formation of gold metal in the bulk solution. During the gold plating process, H₂O₂ as the reducing agent was thermodynamically capable of reducing Au³⁺ ions from the HAuCl₄ precursor to gold atoms, which deposited onto the glass surface and finally formed the continuous gold film. The resulting gold film was characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscope (AFM), respectively.     

Organic Protective and Decorative Coatings for Metal Containers

The adhesion of paint to metal is affected by the nature and condition of the metal surface at least as much as by the nature of the paint. Paints of all types appear to adhere well to most very clean metals but the adhesion of some paints is sensitive to extremely low levels of contamination—for example, by stearic acid. Non-polar hydrocarbon contaminants do not reduce adhesion seriously unless they are present in amounts sufficient to weaken the cohesion of an interfacial layer. The surfaces of almost all commercial metal sheets are contaminated and require pretreatment before painting. The nature of the contaminants present are discussed and laboratory techniques for obtaining cleaning surfaces are reviewed.     

Stainless Steel Bipolar Plates Deposited with Multilayer Films for PEMFC Applications

A chromium nitride (CrN, Cr₂N)/chromium (Cr)/indium-tin-oxide (ITO) system and a gold (Au)/titanium (Ti) system were separately deposited using a sputtering method and an E-beam method, respectively, onto stainless steel 316 and 304 plates. The XRD patterns of the deposited stainless steel plates showed the crystalline phase of typical indium-tin oxide and of metallic phases, such as chromium, gold, and the metal substrate, as well as those of external chromium nitride films. The nitride films were composed of two metal nitride phases that consisted of CrN and Cr₂N compounds. The surface morphologies of the modified stainless steel bipolar plates were observed using atomic force microscopy and FE-SEM. The chromium nitride (CrN, Cr₂N)/chromium (Cr)/indium-tin-oxide (ITO) multilayer that was formed on the stainless steel plates had a surface microstructural morphology that consisted of fine columnar grains 10 nm in diameter and 60 nm in length. The external gold films that were formed on the stainless steel plates had a grain microstructure approximately 100 nm in diameter. The grain size of the external surface of the stainless steel plates with the gold (Au)/titanium (Ti) system increased with increasing gold film thickness. The electrical resistances and water contact angles of the stainless steel bipolar plates that were covered with the multilayer films were examined as a function of the thickness of the ITO film or of the external gold film. In the corrosion test, ICP-MS results indicated that the gold (Au)/titanium (Ti) films showed relatively excellent chemical stability after exposure to H₂SO₄ solution with pH 3 at 80 °C.     

“in situ” XPS studies of laser induced surface cleaning and nitridation of Ti

A titanium foil has been subjected to laser irradiation “in situ” in a pre-chamber of an X-ray photoemission spectrometer under different atmospheres (vacuum, Ar, O₂, air, N₂ and H₂). As a result of these treatments, a high amount of the carbon contamination layer was removed and other changes in composition were induced. Nitridation was achieved by laser irradiation under nitrogen. The most effective treatment protocol included an initial cleaning procedure induced by irradiation in vacuum, followed by a second irradiation process performed under nitrogen. Partial nitridation is also observed when irradiating under synthetic air. Lateral and depth analysis of the nitrogen concentration around the laser spot has been also carried out. It is found that the outermost layers present a similar concentration of nitrogen. In addition, the measured nitrogen profile indicates that the amount of nitrogen within the laser spot region is relatively lower than within the immediately surrounding area. Almost no nitrogen remains in the spot area after sputtering for 30 min. A model is proposed to account for the observed titanium surface nitridation processes.