Simple Surface Treatment Method Research Articles

A Simple Surface Treatment for Mg to Gain Enhanced Resistance to Corrosion and Corrosive Wear by Hammering Al Powder‐Covered Mg Substrate

AbstractMg is abundant in the earth crust and very attractive as a base metal of lightweight alloys for the transportation industry due to its high strength‐to‐weight ratio. However, Mg is prone to corrosion, which largely limits its widespread applications. Here, a very simple surface treatment method is demonstrated for enhanced resistance to corrosion and corrosive wear by hammering Al powder‐covered surface of Mg with subsequent recovery treatment. Such treated surface is examined with X‐ray diffraction technique for information on phases, nanocrystallization, thickness, and coverage of the Al layer. Structure of the Al layer and lattice imperfections are analyzed with transmission electron microscopy. Electrochemical behavior, corrosion, and corrosive wear of the treated surface are evaluated. It is shown that the treated surface is nanocrystalline with significantly increased resistance to corrosion and corrosive wear. The effect of recovery heat treatment on microstructure of the Al layer is particularly characterized and demonstrated to be essential for achieving high degrees of nanocrystallization and structure integrity through eliminating lattice defects generated during the hammering process, leading to a desired nanocrystalline structure with high stability and superior properties. Molecular dynamics simulation is also performed to gain an insight into the underlying mechanism.

Improved Performance of Acetone Gas Sensing through Oxygen Vacancy Formation of ZnO Nanoparticles

Introduction Recently, interest in gas sensors have been increasing in different fields of not only industry and medical applications but also development of smart city and detection of indoor air pollutants. In particular, acetone is a volatile organic compound (VOC) used as a biomarker to indicate various diseases in human exhalation, or has been importantly measured as one of the indicator gases for indoor pollution measurement [1]. Unlike industrial sensors that need to detect relatively high concentration gas, the detection of acetone for biomarkers requires highly sensitive sensing materials which can react with the gas quickly.Metal oxide semiconductor (MOS) have been widely used as gas sensors because of their thermal and chemical stability and natural abundance. A lot of researches for detecting acetone gas using metal oxide semiconductor, for instance, WO3, SnO2 and ZnO through diverse method and morphology control, have been studied in recent [2]. Among them, ZnO is in the spotlight for various reasons due to their facile size and structure control, gas reactive surface and appropriate band gap. Many papers associated gas sensing of ZnO were published in multiple ways as metal doping and quantum dot control [3, 4]. In this study, oxygen vacancy was produced by simple H2O2 surface treatment of commercial ZnO, and the amount of oxygen vacancy by the degree of surface treatment was quantified. In addition, through evaluating acetone sensing performance according to the amount of oxygen vacancy, optimal vacancy amount showing significantly superior sensitivity was found. Chemical calculation described the reason of the outstanding response [5-8]. Further information will be discussed in detail. Method Surface oxygen vacancy is generated by a variety of H2O2 treatment with 400 ˚C annealing. ZnO controlled oxygen vacancy was reacted with 10 ppm acetone at 300 – 500 ˚C, and confirm response of the material. Response of varied temperature was confirmed through three or more repeated sensor measurements, and the measurement was performed at various concentration ranging from 0.01 ppm to 10 ppm under optimized temperature conditions. And the performance was identified under various humidity conditions and long-term stability. Results and Conclusions When H2O2 was treated on commercial ZnO, ZnO2 was produced. ZnO with oxygen vacancy was formed after 400 ˚C annealing on the obtained ZnO2. Treatment with high concentrated H2O2 results in more defects, breaking crystallinity and reducing the XRD peak sharpness. Therefore, we found optimal concentration conditions that create oxygen vacancy around the surface. The deficient oxygen and lattice oxygen peaks were deconvoluted from the O 1s peaks of the XPS spectrum and the vacancy to lattice ratio was obtained. Also, the formation of oxygen vacancy could be confirmed by the peak shift of Zn 2p3/2. The oxygen vacanced ZnO had a high sensitivity of 1692.1 (Fig. 1). This results showed the world’s best sensitivity compared with previous reported outcomes such as commercial ZnO (S=107), SnO2 nanorod arrays (S=511) and In-doped ZnO quantum dots (S=424). This study shows the possibility of commercialization through a simple surface treatment method that can be widely applied to a wide range of metal oxides, and it is widely applicable to systems of diverse fields where low concentrations of acetone have to be fairly sensitive.

Enhanced epoxy adhesion between steel plates by surface treatment and CNT/short-fibre reinforcement

The wettability of grit blasted steel substrates is improved by a simple surface treatment method proposed in this study. The shear strength of epoxy adhesive joints has been improved by over 50% after optimizing this “resin pre-coating” surface treatment method. The shear strength is further enhanced by incorporating multi-walled carbon nanotubes (MWCNTs) and short Kevlar fibres into the adhesive joints, with over 70% improvement for the combined surface-treated and MWCNTs toughened adhesive joints. The reinforcing mechanisms along the “interfacial zone” defined by the surface topography and the toughening mechanisms within the “composite adhesive joints” because of MWCNTs and short Kevlar fibres are discussed together with detailed Scanning Electron Microscopy (SEM) observations and experimental results.

A Surface Tailoring Method of Ultrathin Polymer Gate Dielectrics for Organic Transistors: Improved Device Performance and the Thermal Stability Thereof

Tailoring the surface of the dielectric layer is of critical importance to form a good interface with the following channel layer for organic thin film transistors (OTFTs). Here, a simple surface treatment method is applied onto an ultrathin (<15 nm) organosilicon‐based dielectric layer via the initiated chemical vapor deposition (iCVD) to make it compatible with organic semiconductors without degrading its insulating property. A molecular‐thin oxide capping layer is formed on a 15 nm thick poly(1,3,5‐trimetyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) by a brief oxygen plasma treatment. The capping layer greatly enhances the thermal stability of the dielectrics, without degrading the original mechanical flexibility and insulating performance of the dielectrics. Moreover, the surface silanol functionalities formed by the plasma treatment can also be utilized for the surface modification with silane compounds. The surface‐modified dielectrics are applied to fabricate low‐voltage operating (<5 V) pentacene‐based OTFTs. The highest field‐effect mobility of the device with the surface‐treated 15 nm thick pV3D3 is 0.59 cm2 V−1 s−1, which is improved up to two times compared to the TFT with the pristine pV3D3. It is believed that the simple surface treatment method can widely extend the applicability of the highly robust, ultrathin, and flexible pV3D3 gate dielectrics to design the surface of the dielectrics to match well various kinds of organic semiconductors.

Effect of UV/ozone treatment on polystyrene dielectric and its application on organic field-effect transistors

The influence of UV/ozone treatment on the property of polystyrene (PS) dielectric surface was investigated, and pentacene organic field-effect transistors (OFETs) based on the treated dielectric was fabricated. The dielectric and pentacene active layers were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that, at short UVO exposure time (<10 s), the chemical composition of PS dielectric surface remained the same. While at long UVO exposure time (>60 s), new chemical groups, including alcohol/ether, carbonyl, and carboxyl/ester groups, were formed. By adjusting the UVO exposure time to 5 s, the hole mobility of the OFETs increased to 0.52 cm2/Vs, and the threshold voltage was positively shifted to -12 V. While the time of UVO treatment exceeded 30 s, the mobility started to shrink, and the off-current was enlarged. These results indicate that, as a simple surface treatment method, UVO treatment could quantitatively modulate the property of PS dielectric surface by controlling the exposure time, and thus, pioneered a new way to modulate the characteristics of organic electronic devices.

Submicrometer-Sized Pickering Emulsions Stabilized by Silica Nanoparticles with Adsorbed Oleic Acid

Oil-water Pickering emulsions of about 200 nm were stabilized by nanosized hydrophilic silica after a simple surface treatment method. We have modified the aqueous silica nanoparticle dispersions by simple adsorption of oleic acid to their surfaces, improving the hydrophobicity of the particles while maintaining their charge and stability. The adsorption was monitored by small-angle X-ray scattering and electrophoretic measurements to estimate the interparticle interactions and surface charges. The effect of various parameters, such as nanoparticle concentration, amount of oleic acid, ionic strength, and pH, on the droplets' size and stability was investigated by dynamic light scattering. Furthermore, the ability of these modified silica nanoparticles to stabilize long-chain alkanes, liquid paraffin, and liquid-crystalline phases was examined.

Synthesis and characterization of cholesterol-poly(ethylene glycol)-poly(D,L-lactic acid) copolymers for promoting osteoblast attachment and proliferation

A novel cholesterol-poly(ethylene glycol)-poly(D,L-lactic acid) copolymer (CPEG-PLA) has been synthesized as a potential surface additive for promoting osteoblast attachment and proliferation. The gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR) results indicated the product had expected structure with low polydispersities in the range of 1.1-1.5. By blending the poly(D,L-lactic acid) (PLA) with CPEG-PLA, the surface of modified PLA membrane was investigated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle. The results revealed the enrichment of PEG chain on the surface. Osteoblast cell line (MC3T3) was chosen to test the cell behavior on modified PLA membranes. The osteoblast test about cell attachment, proliferation, cell viability and cell morphology investigation on CPEG-PLA modified PLA substrates showed the CPEG-PLA with 15 and 5 ethylene glycol units promoted osteoblast attachment and growth, while the CPEG-PLA with 30 ethylene glycol units prevent osteoblast adhesion and proliferation. This simple surface treatment method may have potentials for tissue engineering and other biomedical applications.

Surface tailoring of poly( dl-lactic acid) by ligand-tethered amphiphilic polymer for promoting chondrocyte attachment and growth

The ligand-tethered poly(ethylene oxide–propylene oxide–ethylene oxide) (PEO–PPO–PEO) triblock copolymer was explored to engineer poly( dl-lactic acid) (PDL-LA) material to promote cell attachment and growth. The PEO–PPO–PEO was activated by methyl sulfonyl chloride and the amino acid, and peptide were attached. By blending the PDL-LA with the ligand-tethered PEO–PPO–PEO derivatives, the surface of modified PDL-LA film was investigated by ATR-FTIR, XPS and contact angle. The chondrocytes test on different PDL-LA films indicated that the PEO–PPO–PEO amino acid and RGD derivatives modified PDL-LA films could promote chondrocyte attachment and growth. This simple surface treatment method may have potentials for tissue engineering and other biomedical applications.

Surface Engineering of Poly(DL-lactic acid) by Entrapment of Biomacromolecules

Alginate, chitosan and gelatin were deposited on the surface of PDL-LA films via an entrapment method. ATR-FT-IR, XPS and contact-angle analyses revealed the formation of stable thin biomacromolecule layers on the PDL-LA film, thus enhancing the hydrophilicity of the films. Confocal laser scanning microscopy showed the existence of entrapment areas of approximately 10–20 μm in depth. This simple surface-treatment method may have the potential for many biomedical applications.

Surface Treatment by Ar Plasma Irradiation in Electron Cyclotron Resonance Chemical Vapor Deposition

To reduce the surface states of GaAs and related semiconductors which originate from native oxides on a surface, we developed a simple surface treatment method in which the surface oxides could be physically sputtered by Ar plasma irradiation in an electron cyclotron resonance chemical vapor deposition (ECR-CVD) apparatus. In the experiment of Ar irradiation of a GaAs surface, we were able to determine the optimum irradiation time at which the native-oxide-related surface states were almost removed without damaging the irradiated surface. Then, we applied this method to an actual 0.98-µm semiconductor laser in which catastrophic optical damage (COD) failure occurred due to the surface states of the output facet. By irradiating Ar plasma to the output facet of the laser and removing the oxide-related surface states there, tolerance to COD was remarkably improved compared with that of a conventional non-Ar-irradiated one.