INVESTIGATION OF SURFACE MORPHOLOGY, STRUCTURE AND ELECTROCATALYTIC PROPERTIES FOR O_2 EVOLUTION OF TITANIUM BASED IrO_2+Ta_2O_5 COATINGS

Titanium based IrO2 +Ta2O5 oxide anodes with different compositions and pyrolysis temperatures were prepared by termodecompoisition method. By using X-ray diffraction (XRD), the structure and texture coefficient of the coatings, TC(hkl), of IrO2 rutile crystal have been tested. It showed that, the crystallization processes of IrO2 and Ta2O5 in xIrO2 +(100-x) Ta2 O5 (x is in mol%) films affected and confined each other.In the mixed system, IrO2 rutile phase existed as a solid solution with Ta, and attained the maximum solubility when x=70mol%, i.e. for the coating of 70% IrO2 +Ta2O5.For the coatings of low iridium content or at low preparing tem pemture, (110) and (101) pwtered orientations were dominant. However, preferred growth of IrO2 weakened with increasing either iridium content or temperature. Three typical surface morphologies were observed by using scanning electron tnicroscopy(SEM). The crystallite size of the mixed oxide coatings were finest for the the film of 70%IrO2 +30%Ta2O5,and decreased with the pyrolysis tempemture. As the results of the finest crystallite segregating on sudece and the maxitnum solid solubility of Ir and Ta component in deposits, the coatings with the composition of 70%IrO2 +Ta2O5 prepared at 450℃ presented the mdrimutn electrocatalgtic activitg for O2 evolution in 0. 5M H2SO4 solution.UP to 550℃, Ti base suffered to oxidation resulting in decreasing anode conductivity,therefore, coatings performed a low activity.

Molybdenum based amorphous and nanocrystalline coatings prepared by high velocity oxy-fuel spraying

The high velocity oxy-fuel(HVOF) based thermal spray process has developed as a potential advantageous approach for fabricating various kinds of functional coatings.In this article,the coatings of Mo-based alloy were synthesized using the HVOF process.The microstructure and the mechanical properties of the HVOF-processed coatings were investigated using SEM,TEM,XRD,and hardness and wear tests.Annealing treatment was applied to the as-sprayed coatings to develop the microstructure and its effect on the microstructure and mechanical properties of the coatings was examined.It is found that the HVOF-processed Mo-based alloy coatings are comprised of an amorphous splat matrix embedded with nano-sized crystalline particles.Annealing at temperatures over 950 ℃ results into crystallization of the amorphous matrix.The mechanical properties of the as-sprayed coatings are enhanced with annealing temperature up to 750 ℃ and from 950 to 1050 ℃,keeps constant between 750 and 950 ℃,and reduce over 1050 ℃.The change of the mechanical property with the microstructure was illustrated in the study.

Improving Wear Resistance of the Ni-base Thermal Spray-Welding Coating Using Rare Earths

By adding rare earth alloy and cerium oxide, the effect of rare earths on tribological properties of nickel base alloy layer was studied to approach the possibility of applying rare earths to Ni base thermal spray welding coating. Wear test results showed that the wear rates of the nickel base coating without rare earths were quite high, and the load bearing capacity of coating was low, in contrast, the wear rates of the coating with rare earths were low and the coating had higher load bearing capacity. The results show that rare earths can refine the structure of nickel base alloy, improve the interface of the coating and substrate.

STUDIES OF LOW-CONCENTRATION CHROMATE PASSIVE FILM FOR ZINC-BASED ALLOY COATED STEEL WIRES

The corrosion resistance of a low concentration chromate passive film for zinc based alloy coated steel wires was assessed by salt spray and electrochemical corrosion tests. XPS and AES analyses showed that the composition of such chromate passive film was S 5 5, Na 3 4, C 11 8, Ti 7 9, O 41 6, Cr 13 7, Zn 16 0.

SYNTHESIS OF DIARYL ETHERS THROUGH PHASE TRANSFER CATALYSIS WITH POTASSIUN FLUORIDE COATED ALUMINA AS A STRONG BASE

Seven diaryl ethers were synthesized with potassium fluoride coated alumina as a strong base and the addition of catalytic amount of PTC. The yield of diaryl ethers with addition of PTC was much higher than that without PTC.A discussion of the catalysis mechanism was given in this paper.

COATED CARBIDE TOOL'S CUTTING PERFORMANCE AND ITS DATA BASE

The development and application of coated cemented carbide made in China are pres-ented. Three aspects of the coated carbide tool's performance: cutting forces, surface finish and toollife are studied. Furthermore speed-correcting coefficients of the tool are given. On the basis of thework, a data base for coated carbide tools has been built on a microcomputer. It consists of fivemodules. essential data base, tools' comparison and inquiry, recommending cutting regimes, exper.imental curve base and an expert system for tool selection.

Improvement of thermal stability of ZrSiON based solar selective absorbing coating

Solar selective absorbing coatings(SSACs)are required to have not only excellent optical property but also outstanding thermal stability for high temperature applications.The optical properties of Mo/ZrSiN/ZrSiON/SiO_(2) SSAC had been optimized successfully before.Herein,we are focusing on the evaluation and mechanism of thermal stability of this multilayer coating for its potential applications in concentrated solar power(CSP)systems.Fortunately,the coating exhibits excellent thermal stability after aging at 400℃ for 1500 h in vacuum.At aging temperature of 500℃ for 1000 h or 600℃ for 300 h in vacuum,the slight inter-diffusion between Mo layer and stainless steel(SS)substrate occurs.At higher aging temperature of 700℃ for 100 h in vacuum,the serious inter-diffusion between Mo layer and SS substrate leads to invalidation of the coating,which has been evidenced by Rutherford backscattering spectrometry(RBS)and X-ray diffraction(XRD)technologies.Additionally,this coating also has an outstanding thermal stability after aging at 400℃for 300 h in air.A heating-cooling cycling(HCC)treatment evidences the good thermal stability of this coating working in cold environment(60℃).The results reveal that this coating can be a promising candidate not only for CSP system in high temperatures but also for usage in cold environment.

Anticorrosion behavior of conversion coatings obtained from unbuffered cerium salts solutions on AA6061-T6

The anticorrosive properties of cerium based conversion coatings deposited on AA6061-T6 alloy by immersion in tmbuffercd cerium chloride and cerium nitrate solutions in the presence of hydrogen peroxide were investigated and characterized by potentiodynamic po- larization （PDP） and electrochemical impedance spectroscopy （EIS） in 0.5 mol/L NaCl aqueous solution. The microstructure and chemical composition of the protective films were examined by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDS）. It was found that the best corrosion protection was afforded by the samples treated during 600 s in cerium chloride solution at pH values ~5.5-4, showing higher amounts of cerium and polarization resistance values greater than 10 f~ m2. Moreover, an ennoblement of the corro- sion potential and decreasing of the cathodic and anodic currents were obtained compared with the cerium nitrate solutions application. This behavior was attributed to the influence of the deposition parameters such as type of the salt anion, i.e., chelating effect and chaotropic characteristics, pH fluctuations in the conversion solution and deposition time.

Humidity and temperature sensor based on GOQDs-PVA coated tapered no-core fiber combined with FBG

A simple structure optical fiber sensor for relative humidity(RH) and temperature measurement is proposed and verified in this paper, which is based on graphene oxide quantum dots and polyvinyl alcohol(GOQDs-PVA) composite coated tapered no-core fiber(NCF) combined with a fiber Bragg grating(FBG). FBG is insensitive to humidity and sensitive to temperature, which is used to compensate temperature of the sensor. Experimental results show this sensor has humidity sensitivity of 143.27 pm/%RH ranging from 30%RH to 80%RH and the temperature sensitivity of 9.21 pm/℃. The proposed sensor has advantages of simple structure, good repeatability, and good stability, which is expected to be used in both RH and temperature measurement in biological and chemical fields.

A localized surface plasmon resonance DNA biosensor based on gold nanospheres coated on the tip of the fiber

A localized surface plasmon resonance(LSPR) biosensor was prepared with gold nanospheres(Au NSs) coated on the tip face of the optical silica fiber. Au NSs with the sizes of 20 nm and 80 nm were used. The sensitivities of Au NS_(20 nm) and Au NS_(80 nm) modified sensors to bulk refractive index(RI) variation are 82.86 nm/RIU and 218.98 nm/RIU, respectively. The Au NS_(80 nm) modified sensor was used for the detection of 40 bases DNA hybridization and the limit of detection is 50 nmol/L, where the 40-bases DNA probe was covalently linked with Au NS_(80 nm). The complementary DNA sequence in tris-acetate-EDTA(TAE) buffer solution was detected as the target DNA. This fiber sensor has the advantages of small sample consumption, easy fabrication and high sensitivity.