Surface modification of ZrO_2 nanoparticles with styrene coupling agent and its effect on the corrosion behaviour of epoxy coating

The surface of ZrO2 nanoparticles was modified by styrene coupling grafting method to improve the dispersion and interaction of the nanoparticles with the epoxy coating in which the modified ZrO2 nanoparticles were used as an additive. The grafting performance and microstructure of the nano- ZrO2/epoxy coating were analyzed by Fourier transformation infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The corrosion behavior of the nano-ZrO2/epoxy coating on mild steel was evaluated in neutral 3.5 wt% NaC1 solution using electrochemical impedance spectroscopy （EIS）. Both the coating capacitance and coating resistance fitted by the equivalent circuit from EIS were used to evaluate the protective performance of the coating towards the mild steel. The results show a superior stability and efficient corrosion protection by the modified ZrO2 nanoparticles. The epoxy coating containing 2 wt% modified ZrO2 nanoparticles exhibited the best corrosion performance among all the coating specimens. This research may provide an insight into the protection of mild steel using modified epoxy coatings.

Surface modification with SiO_2 coating on biomedical TiNi shape memory alloy by sol-gel method

The effect of heat treatment on the transformation temperature of Ti?52.2%Ni (mole fraction) alloy was studied using differential scanning calorimetry (DSC). The transformation temperatures of the alloy can be adjusted effectively by heat treatment. Dense and stable SiO2 coatings were deposited on the surface of the pre-oxidized TiNi alloy by sol?gel method. The bonding strength of films and matrix was (65.9±1.5) N. The electrochemical corrosion test shows that the TiNi alloy with SiO2 coating has excellent corrosion resistance in the Hank’s simulated body fluid. The release behaviors of Ni ion of the alloy with and without SiO2 coating implanted in the acoustic vesicle of guinea pig were studied by EDS testing, which was inhibited effectively by the dense and stable SiO2 coating on the alloy.

Graft modification of ZnO nanoparticles with silane coupling agent KH570 in mixed solvent

The reaction of ZnO nanoparticles grafted with KH570 silane coupling agent was carried out in water-alcohol mixed solvent. Several characterization methods were applied to analyzing the results of surface modification such as Soxhlet extraction, Fourier transform infrared spectroscopy （FT-IR）, transmission electron microscopy （TEM）, thermogravimetry （TG）, differential scanning calorimetry （DSC） and zeta potential （ζ）. The results of FT-IR and TG-DSC show that the desired reaction chains have been covalently bonded on the surface of ZnO nanoparticles. Zetasizer results reveal that the maximal absolute value of ζ of the modified ZnO particles in acetone medium was 67.0 mV, which was much higher than that of the unmodified ZnO particles. So the surface of nanosized ZnO changed from hydrophilicity to hydrophobicity and the dispersity of ZnO nanoparticles were improved simultaneously. Finally, the mechanism of graft modification was discussed.

Crystalline texture evolution, control of the tribocorrosion behavior, and significant enhancement of the abrasion properties of a Ni-P nanocomposite coating enhanced by zirconia nanoparticles

This paper describes an investigation of the effect of ZrO2 nanoparticles on the abrasive properties,crystalline texture developments,and tribocorrosion behavior of Ni-P nanostructured coatings.In the investigation,Ni-P and Ni-P-ZrO2 nanostructured coatings are deposited on St52 steel via the electroless method.Transmission electron microscopy(TEM),field emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),cyclic-static polarization tests in 3.5wt%NaCl solution,the tribocorrosion test(by back-and-forth wear in electrochemical cell),and the microhardness test using the Vickers method were performed to characterize and analyze the deposited coatings.The results of this study showed that the addition of ZrO2 nanoparticles to the Ni-P electroless bath produced the following:a sharp increase in wear and hardness resistance,the change of the wear mechanism from sheet to adhesive mode,the reduction of pitting corrosion resistance,significant reduction in the tribocorrosion protective properties,change in the preferred orientation of the crystalline texture coating from(111)to(200),increase in the sedimentation rate during the deposit process,and a sharp increase in the thickness of the Ni-P nanostructured coatings.

Surface organic modification of Fe_3O_4 nanoparticles by silane-coupling agents

Fe3O4 nanoparticles were prepared by chemistry co-precipitation and the mean crystal size was 17.9 nm measured by XRD. After it had been treated by silane-coupling agents KH570, magnetic micro-spheres dispersed in organic medium glycol were gained and the mean size of Fe3O4 nanopowders was 33.7 nm. So it can be concluded that magnetic micro-sphere is made of a few Fe3O4 crystals. Many factors of modification were researched, such as the time of ball milling, the content of Fe3O4 and the content of KH570. The modification of Fe3O4 is relative to the time of ball milling, but the dominant function is affected by the content of Fe3O4 and KH570. When the content of Fe3O4 is known, there is a suitable content of KH570. Different content of Fe3O4 will make the different suitable content of KH570, but the range of latter is less than former, which is relative to the distribution of KH570 on Fe3O4 surface or in the solution.

Surface Organic Modification of Fe_3O_4 Magnetic Nanoparticles

The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied. The modified and unmodified nanoparticles were characterized by FT-IR, XPS and TEM. The spectra of FT-IR and XPS revealed that KH570 was coated onto the surface of Fe3O4 nanoparticles to get Fe-O- Si bond and an organic coating layer also was formed. Fe3O4 nanoparticles were spheres partly with mean size of 18,8 nm studied by TEM, which was consistent with the result 17.9 nm calculated by Scherrer＇s equation. KH570 was adsorbed on surface and formed chemistry bond to be steric hindrance repulsion which prevented nanoparticles from reuniting. Then glycol-based Fe3O4 magnetic liquids dispersed stably was gained.

Investigation of ZrO2 nanoparticles concentration and processing time effect on the localized PEO coatings formed on AZ91 alloy

AZ91 Mg alloy was treated through a new localized PEO(Plasma Electrolytic Oxidation)coating approach,using electrolyte solutions with varying ZrO2 nanoparticles concentration(2-8 g/L)and processing times.With increase in the ZrO2 concentration,several microstructural changes were observed including;formation of cluster-type structure,damage to the inner layers(∼30 min)and sealing of defects.Corrosion analysis of the final coatings was carried out using potentiodynamic polarization,electrochemical impedance spectroscopy and post-corrosion analysis.It was explored that highest corrosion resistance(Rp∼81.17 kΩcm^2)of the coatings was obtained for ZrO2∼2 g/L.However,higher concentration of the ZrO2 nanoparticles caused weak crystalline coating structure,due to unstable and lower intensity discharges,thus failed to offer high corrosion resistance performance.

Surface modification of magnetic nanoparticles in biomedicine

Progress in surface modification of magnetic nanoparticles（MNPs） is summarized with regard to organic molecules,macromolecules and inorganic materials. Many researchers are now devoted to synthesizing new types of multi-functional MNPs, which show great application potential in both diagnosis and treatment of disease. By employing an ever-greater variety of surface modification techniques, MNPs can satisfy more and more of the demands of medical practice in areas like magnetic resonance imaging（MRI）, fluorescent marking, cell targeting, and drug delivery.

Modification of Fe_3O_4 Magnetic Nanoparticles by L-dopa or Dopamine as an Enzyme Support

Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modified by L-dopa or dopamine using sonication method. The analysis of FTIR clearly indicated the formation of Fe-O-C bond. Direct immobilization of trypsin （EC： 3.4.21.4） on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent. No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed. The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.

Properties and strengthening mechanism of brush plated nanoparticle reinforced composite coatings

Nanoparticle reinforced nickel matrix composite coatings, such as n-Al2O3/Ni, n-SiO2/Ni, n-SiC/Ni and n-TiO2/Ni, were fabricated by brush plating technique. Hardness, wear resistance and contact-fatigue resistance of the composite coatings were determined, and strengthening mechanism of the composite coatings was discussed. Results show that the composite coatings have superior properties to the Ni metal coating. Compared with properties of brush plated Ni metal coating, the composite coatings have hardness over 1.5 times and wear resistance capability of about 2.5 times. The strengthening mechanism of the composite coatings mainly includes fine-crystal grain effect, nanoparticle dispersion effect and dislocation effect.

Modification of ZnS∶Mn Phosphors by Sb-Doped SnO2 Coating

The coating of ZnS∶Mn by Sb-doped SnO2 using an co-precipitation process was reported. ZnS∶Mn phosphor particles were prepared by solid reaction with ZnS and MnCl2·4H2O. Surface modification of the ZnS∶Mn powders was carried out by coating transparent conductive films of Sb-doped tin oxides which were formed by co-precipitation and heat treatment process. Tin tetrachloride and antimony trichloride were used as the precursor materials for the co-precipitation. The influences of coating molar ratio, Sb concentration in the coatings, annealing temperature and time on the resistivity of coated ZnS∶Mn phosphors were investigated. The optimum co-precipitation processing parameters and annealing conditions were determined. The phosphors were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence(PL) observation and conductance measurements. An improvement in phosphors conductivity was observed while the respective photoluminescence intensity is analogous to the as-prepared ZnS∶Mn phosphors.

Modification of nanometer calcium carbonate for water-borne architectural coatings

A kind of modifier was synthesized to modify the surface of nanometer calcium carbonate （abbreviated as nano-CaCO3）, which is used in architectural coatings. The modification technology of the nano-CaCO3 was studied through orthogonal experimental methods. The factors studied were rotation speed, modifier dosage, emulsification temperature, emulsification time and heat aging time after emulsification. Optimized conditions for modification of the surface were： rotation speed 16000 r/min; modifier dosage 3%; emulsification temperature 75 ℃; emulsification time 60 min and aging time 40 min. The modified nano-CaCO3 was also studied by size-distribution measurements, transmission electron microscopy, infrared spectroscopy and thermal analysis. The results show that the size distribution of the modified nano-CaCO3 is uniform and that there are chemi-sorption and physi-sorption between the nano-CaCO3 and the modifier. Compared to traditional architectural coatings without nano-CaCO3, the nanometer composite coatings are obviously improved in respect to dirt resistance, scrub resistance, thixotropy, water resistance, alkalinity resistance and aging resistance.

Effect of TiO_(2) nanoparticles on the photocatalytic properties of PEO coatings on Mg alloy

A comprehensive study of the properties of coatings formed on a magnesium alloy by plasma electrolytic oxidation(PEO) using the electrolytes with nanosized particles of anatase(titanium dioxide) has been carried out. Formed coatings reduce corrosion current density 2.5-fold and increase hardness by 25% compared to a coating without particles. Confocal micro-Raman spectroscopy revealed the presence of anatase and rutile phases in the composition of PEO coating due to the incorporation of TiO2nanoparticles during plasma electrolytic treatment. The presence of titanium dioxide had a positive effect on the photocatalytic properties of coatings: the constant rate of the methyl orange and methyl blue decomposition is increased in 1.6 and 1.8-fold, respectively, compared to the coating formed in electrolyte without TiO_(2) particles.

Engineering polymer nanoparticles using cell membrane coating technology and their application in cancer treatments:Opportunities and challenges

Nanotechnology has revolutionized cancer drug delivery,and recent research continues to focus on the development of“one-size-fits-all,”i.e.,“all-in-one”delivery nanovehicles.Although nanomedicines can address significant shortcomings of conventional therapy,biological barriers remain a challenge in their delivery and accumulation at diseased sites.To achieve long circulation time,immune evasion,and targeted accumulation,conventional nanocarriers need modifications,e.g.,PEGylation,peptide/aptamer attachment,etc.One such modification is a biomimetic coating using cell membrane(CM),which can offer long circulation or targeting,or both.This top-down CM coating process is facile and can provide some advantageous features over surface modification by synthetic polymers.Herein,an overview is provided on the engineering of CM camouflaged polymer nanoparticles.A short section on CM and the development of CM coating technology has been provided.Detailed description of the preparation and characterization of CM camouflaged polymer NPs and their applications in cancer treatment has been reported.A brief comparison between CM coating and PEGylation has been highlighted.Various targeting approaches to achieve tumor-specific delivery of CM coated NPs have been summarized here.Overall,this review will give the readers a nice picture of CM coated polymer NPs,along with their opportunities and challenges.

Surface modification and functionalization by electrical discharge coating:a comprehensive review

Hard coatings are extensively required in industry for protecting mechanical/structural parts that withstand extremely high temperature,stress,chemical corrosion,and other hostile environments.Electrical discharge coating(EDC)is an emerging surface modification technology to produce such hard coatings by using electrical discharges to coat a layer of material on workpiece surface to modify and enhance the surface characteristics or create new surface functions.This paper presents a comprehensive overview of EDC technologies for various materials,and summarises the types and key parameters of EDC processes as well as the characteristics of resulting coatings.It provides a systematic summary of the fundamentals and key features of the EDC processes,as well as its applications and future trends.

Surface modification of ammonium nitrate by coating with surfactant materials to reduce hygroscopicity

Ammonium nitrate(AN)is promising oxidizer in green propellants.In this work,the physical coating method was improved to modify the surface of ammonium nitrate particles with different surfactant materials to reduce hygroscopicity.Cetylalcohoi,stearic acid,stearyl alcohol,palmic acid,lauric acid,stearsmide,tetradecylamine,dodecylamine,and tetradecanol were used as coating surfactant agents.The hygroscopicity was tested for ammonium nitrate with and without coating.Fourier transform infrared(FTIR)and scanning electron microscopy(SEM)were used to characterize the surface of coated and uncoated ammonium nitrate.The mass ratio of coating layer and decline of absorption rate of ammonium nitrate coated by cetylalcohol were 1.00%,and 28.40%,respectively.The results indicate that coating with cetylalcohol surfactant have advantages over the other surfactants in term of low mass ratio of coating layer,and high decline of moisture absorption rate.Thus,cetylalcohol would be a promising coating surfactant material for ammonium nitrate.The idea and approach presented in this study have potential to made hydrophobic layer on the surface of particles to reduce hygroscopicity of AN,and also help the researcher to improving anti-hygroscopicity of ammonium salts.

Laser Modification of Plasma Sprayed Alumina Coating

An alumina coating was developed on mild carbon steel by plasma spraying and then modified by laser remelting.Some characteristics of plasma sprayed ceramic coating before and after laser remelting,such as microstructure,wear resistance, heat shock resistance,hot corrosion property and bond strength,have been investigated in this paper.

Photodegradation and Aggregation Prevention of Natural Melanin Nanoparticles by Silica Coating Method

Melanin, the main photoreceptor in living organics, is largely abundant in pigmented hair tissues. Its promising properties have been widely studied in order to fully explore the corresponding applications. However, the photodegradating and aggregating natures of melanin, to some extent, restrict the development of this eco-friendly biomaterial. This study is conducted to overcome both disadvantages by a mature method that coating the original melanin nanoparticles with silica as shells. The results revealed that the aggregation of the melanin/silica nanoparticles (MSNP) was decreased obviously by a 5 h coating and appeared a uniformly mono-dispersed solution. The MSNP that coated for 20 h provided an efficient protection on the photodegradation of the melanin with a 50% maintenance of the melanin content compared with 16% of original melanin and 2% of MSNP-5 h.

Modeling and Optimization of Surface Roughness of Epoxy/Nanoparticles Composite Coating

In power plants,flue gases can cause severe corrosion damage in metallic parts such as flue ducts,heat exchangers,and boilers.Coating is an effective technique to prevent this damage.A robust fuzzy model of the surface roughness(Ra and Rz)of flue gas ducts coated by protective composite coating from epoxy and nanoparticles was constructed based on the experimental dataset.The proposed model consists of four nanoparticles(ZnO,ZrO2,SiO2,and NiO)with 2%,4%,6%,and 8%,respectively.Response surface methodology(RSM)was used to optimize the process parameters and identify the optimal conditions for minimum surface roughness of this coated duct.To prove the superiority of the proposed fuzzy model,the model results were compared with those obtained by ANOVA,with the coefficient of determination and the root-mean-square error(RMSE)used as metrics.For Ra,for the first output response,using ANOVA,the coefficient-of-determination values were 0.9137 and 0.4037,respectively,for training and prediction.Similarly,for Rz,the second output response,the coefficient-of-determination results were 0.9695 and 0.4037,respectively,for training and prediction.In the fuzzy modeling of Ra,for the first output response,the RMSE values were 0.0 and 0.1455,respectively,for training and testing.The values for the coefficient of determination were 1.00 and 0.9807,respectively,for training and testing.The results prove the superiority of fuzzy modeling.For modeling the second output response Rz,the RMSE values were 0.0 and 0.0421,respectively,for training and testing,and the coefficient-of-determination values were 1.00 and 0.9959,respectively,for training and testing.

Effects of Metal Oxide Modifications on Photoelectrochemical Properties of Mesoporous TiO2 Nanoparticles Electrodes for Dye-Sensitized Solar Cells

Mesoporous TiO2 （m-TiO2） nanoparticles were used to prepare the porous film electrodes for dye-sensitized solar cells, and a second metal oxide （MgO, ZnO, A1203, or NiO） modifi- cation was carried out by dipping the m-TiO2 electrode into their respective nitrate solution followed by annealing at 500 ℃. Experimental results indicated that the above second metal oxide modifications on m-TiO2 electrode are shown in all cases to act as barrier layer for the interracial charge transfer processes, but film electron transport and interfacial charge recombination characteristics under applied bias voltage were dependent significantly on the existing states and kinds of these second metal oxides. Those changes based on sec- ond metal oxide modifications showed good correlation with the current-voltage analyses of dye-sensitized solar cell, and all modifications were found to increase the open-circuit photo- voltage in various degrees, while the MgO, ZnO, and NiO modifications result in 23%, 13%, and 6% improvement in cell conversion efficiency, respectively. The above observations indi- cate that controlling the charge transport and recombination is very important to improve the photovoltaic performance of TiO2-based solar cell.