Effect of surface microstructure of aluminum coating on corrosion properties of magnetic refrigerant gadolinium

AI coatings with different microstructures were prepared on the surface of Gd using the magnetron sputtering technique to improve its corrosion resistance. The corrosion behaviors for the pure Gd and Gd with Al coating in distilled water were studied using the mass loss and electrochemical performance. As a result, pure Gd without coating shows a certain amount of surface cracks under water flow conditions, whereas the polygonal Al coating decreases the path of the corrosive medium to body due to the existence of eroding pits structure. Compared with the polygonal structure Al coating and pure Gd, the lamellar structure of Al coating exhibits a higher electrochemical protection performance （e.g., a lower corrosion current and higher self-corrosion potential） and no occurrence of pitting corrosion. Due to an effective physical shield, the formation of the lamellar structure protected the inner Gd part from being corroded, and prolonged the duration of cathodic protection.

Efficiency of Aluminium and Copper Coated Aluminium Electrode in Hydrogen Fuel Generation from Rain Water

Water electrolysis is considered as the most capable and old technology for hydrogen fuel preparation. Electrolysis needs external electrical energy through electrodes to split water into hydrogen and oxygen. An efficient electrolysis requires suitable electrodes to minimize potential drop. In this study Aluminium and Copper Coated Aluminium were used as different combination of Anodes and Cathodes to find out more efficient electrodes combination. NaCl solution in rain water was taken as electrolyte. Rain water was taken to avoid ionic impedance of tap water and expenses of distilled water. In this study, the most efficient electrode combination was Copper Coated Aluminium (anode)-Aluminium (cathode) and gave the highest efficiency of hydrogen production to about 11% at normal temperature for very low concentration of NaCl (0.051 M) which increased with temperature, up to 29% upon rising of temp to 60°C. It was showed that higher concentration of electrolyte would surge the efficiency significantly. If the supplied heat could be provided from any waste heat sources then this study would be more efficient. However, current research evaluated the technical feasibility of this electrode combination for producing hydrogen with electrolysis of rain water utilizing electricity and modified electrodes.

Electrodeposition of aluminum and aluminum-magnesium alloys at room temperature

Electrodeposition of aluminum from benzene-tetrahydrofuran-Al Cl3-Li Al H4 was studied at room temperature. Galvanostatic electrolysis was used to investigate the effect of various parameters on deposit morphology and crystal size, including current density, temperature, molar ratio of benzene/tetrahydrofuran and stirring speed. The deposit microstructure was adjusted by changing the parameters, and the optimum operating conditions were determined. Dense, bright and adherent aluminum coatings were obtained over a wide range of current densities(10-25 m A/cm2), molar ratio of benzene and tetrahydrofuran(4:1 to 7:8) and stirring speeds(200-500 r/min). Smaller grain sizes and well-adhered deposits were obtained at lower temperatures. Aluminum-magnesium alloys could potentially be used as hydrogen storage materials. A novel method for Al-Mg deposition was proposed by using pure Mg anodes in the organic solvents system benzene-tetrahydrofuran-Al Cl3-Li Al H4. XRD shows that the aluminum-magnesium alloys are mainly Al3Mg2 and Al12Mg17.

Double-layer Modifi cation of Water-based Aluminum with SiO2 and Polyacrylic Acid by Solgel Process and in situ Polymerization

A double-layer aluminum consisting of an aluminum core and a shellof SiO2 and polyacrylic acid was synthesized.This modified aluminum was used to improve the corrosion resistance and dispersive property of aluminum in waterborne media.TEM,FTIR,XPS,and EDX determination showed that PAA and SiO2 were coated on the surface of aluminum.Evolved hydrogen detection showed that the corrosion resistance of composite particle had been markedly improved.Maximum corrosion inhibition efficiency of SiO2 coated aluminum（SiO2@Al）was 95.1% while that of double-layer coated aluminum（PAA/SiO2@Al）was 98.8%.Meanwhile,polyacrylic acid layer improved the agglomeration of aluminum significantly.According to the dispersibility test,the particle size of 50% volume fraction [d（0.5）] of aluminum,SiO2@Aland PAA/SiO2@Alwere 42,53,and 34 μm,respectively.

Abrasive wear behaviors of high velocity arc sprayed iron aluminum composite coatings

The High Velocity Arc Spraying （HVAS） technology was used to prepare Fe-Al composite coatings by the adding of different elements into cored wires to obtain different Fe-Al coatings. The added compounds do great effect on the properties of the composite coatings. The microstructures and abrasive wear performances of the coatings were assessed by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, and THT07-135 high temperature wear equipment. It was found that the adding of Cr3C2 can greatly increase the room temperature wear behavior, and Fe-Al/WC coatings have adapting periods at the beginning of wear experiment. With the rise of temperature, the wear resistance of Fe-AI/Cr3C2 coatings becomes bad from room temperature to 250℃, and then stable from 250℃ to 550℃; the wear resistance of Fe-Al/WC becomes well with the rise of temperature. The adding of Cr and Ni can also improve wear performances of Fe-Al composite coatings.

Effects of Al coating on corrosion resistance of sintered NdFeB magnet

Pure Al coating was deposited on sintered NdFeB magnet by direct current（DC） magnetron sputtering to improve the corrosion resistance of magnet. The influences of coating thickness and sputtering power on microstructure and corrosion resistance of Al coating were investigated. The surface morphology of Al coating was characterized by scanning electron microscopy（SEM）. The corrosion properties were investigated by potentiodynamic polarization curves and neutral salt spray（NSS） test. The formation of the uniform and compact Al coating is a necessary condition to achieve excellent corrosion resistance. And the optimal corrosion resistance can be obtained in the sample with 6.69 μm thick Al coating deposited at 51-82 W.

Microstructure and hot corrosion behavior of Al-Ce-Y coatings on DZ125 nickel-based alloy prepared by pack cementation process

In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and formation mechanism of the coatings were investigated.The hot corrosion behaviors of DZ125 alloy and the coatings in molten salt environment of 25%K2SO4+75%Na2SO4(mass fraction)at 900°C were studied.Results show that the obtained Al-Ce-Y coatings were mainly composed of Al3Ni2,Al3Ni and Cr7Ni3,with a thickness of about 120μm.After hot corrosion test,DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose.Two layers of corrosion products formed on surfaces of DZ125 alloy,including the outer layer consisting of Cr2O3 and NiCr2O4,and the inner layer of Al2O3,Ni3S2 and Ni-base solid solution.After being coated with Al-Ce-Y coating,the hot corrosion resistance of DZ125 alloy is improved notably,due to the formation of a dense scale mainly consisting of Al-rich Al2O3 in the coating layer.

Microstructure of Ni–Al powder and Ni–Al composite coatings prepared by twin-wire arc spraying

Ni–Al powder and Ni–Al composite coatings were fabricated by twin-wire arc spraying（TWAS）. The microstructures of Ni-5wt%Al powder and Ni-20wt%Al powder were characterized by scanning electronic microscopy（SEM） and energy dispersive spectroscopy（EDS）. The results showed that the obtained particle size ranged from 5 to 50 μm. The morphology of the Ni–Al powder showed that molten particles were composed of Ni solid solution, NiAl, Ni_3Al, Al_2O_3, and NiO. The Ni–Al phase and a small amount of Al_2O_3 particles changed the composition of the coating. The microstructures of the twin-wire-arc-sprayed Ni–Al composite coatings were characterized by SEM, EDS, X-ray diffraction（XRD）, and transmission electron microscopy（TEM）. The results showed that the main phase of the Ni-5wt%Al coating consisted of Ni solid solution and Ni Al in addition to a small amount of Al_2O_3. The main phase of the Ni-20wt%Al coating mainly consisted of Ni solid solution, Ni Al, and Ni_3Al in addition to a small amount of Al and Al_2O_3, and Ni Al and Ni_3Al intermetallic compounds effectively further improved the final wear property of the coatings. TEM analysis indicated that fine spherical NiAl_3 precipitates and a Ni–Al–O amorphous phase formed in the matrix of the Ni solid solution in the original state.

New Methods Testing of Adhesion of the Coating to Sheet Metal by Bending

The article is deals for new experimental equipment for effective test adhesion for selected coating STEEL, applied cold on the coated metal sheet with Al (aluminum). Explanation to the word STEEL: STEEL coating has significant anti- corrosive properties and he is resistant for main oxidizing agents such as acids, alkalis, salt vapors etc. Resists tem- peratures to 600?C and create an elastic film that is resistant to abrasion, as soon as it was to complete po-lymerization. It is very simple to applied to metallic and nonmetallic surfaces. Dries quickly and is dry to the touch after 90 to 120 seconds. STEEL is the best possible solution anywhere, if needs arises powerful local protection against atmospheric and corrosive agents or to elevated temperatures. STEEL is also useful as a method for protect of welds on stainless steels instead of traditional staining procedures. Broad application is in automotive industry to modify the surfaces of block vehicle, car-body repairs, welds needing protection, in heating industry for example boilers, in air condition with heat exchanger and in shipping industry. [1-3].In experiments with a new test equipment is showed that for bending radius of interval from range R11 to R35 there is a change deposited coating STEEL from original coating Al and this coating was part of test metal sheet of thickness 1.5 mm. In the next stage of solution was developed technological process, which allowed increase of adhesion coating STEEL for bending up to or maximum 180? (shape U). Result of new technology is documented in article. Experiments was implementing with cooperation of the Masaryk University in Brno.

On-Line Defect Detection of Aluminum Coating Using Fiber Optic Sensor

Aluminum metallization using the sprayed coating for exhaust mild steel （MS） pipes of tractors is a standard practice for avoiding rusting. Patches of thin metal coats are prone to rusting and are thus considered as defects in the surface coating. This paper reports a novel configuration of the fiber optic sensor for on-line checking the aluminum metaUization uniformity and hence for defect detection. An optimally chosen high bright 440 nm BLUE LED （light-emitting diode） launches light into a transmitting fiber inclined at the angle of 60° to the surface under inspection placed adequately. The reflected light is transported by a receiving fiber to a blue enhanced photo detector. The metallization thickness on the coated surface results in visually observable variation in the gray shades. The coated pipe is spirally inspected by a combination of linear and rotary motions. The sensor output is the signal conditioned and monitored with RISHUBH DAS. Experimental results show the good repeatability in the defect detection and coating non-uniformity measurement.

The microstructural evolution and wear properties of Ni60/high-aluminum bronze composite coatings with directional structure

The directional structure of Ni60/high-aluminum bronze composite coating was formed using induction remelting and forced cooling.The microstructural evolution and the characteristics of interface growth were studied.The results showed that the remelted coating formed metallurgical bonding with the substrate.The micros tructures changed from plane crystal to dendrite,cellular dendrite,fine cellular dendrite,and then to dendrite again with the increase in the cooling rate.The crystal grew along the heat flow direction and had(111) and(200)preferred orientations when the cooling rate was 1.886 ml-min^(-1).mm^(-2).The plane crystal,dendrite and cellular dendrite were mainly composed of compounds and solid solutions with Ni,Fe and Cu,and they were surrounded by strengthening phases composed of Cr,C and B.The grain boundary of directional structure coatings showed the characteristic of regular eutectic growth,but grain boundary of remelted coating presented characteristic of divorced eutectic growth.The wear resistance of directional structure coatings is better than that of remelted coating.

Enhanced solar-blind ultraviolet single-photon detection with a Geiger-mode silicon avalanche photodiode

Solar-blind ultraviolet detection is of great importance in astronomy and industrial and military applications. Here, we report enhanced solar-blind ultraviolet single-photon detection by a normal silicon avalanche photo- diode （Si APD） single-photon detector with a specially designed photon-collecting device. By re-focusing the reflected photon from the Si chip surface on the detection area by the aluminum-coated hemisphere, the detec- tion efficiency of the Si APD at 280 nm can be improved to 4.62%. This system has the potential for high-efficiency photon detection in the solar-blind ultraviolet regime with low noise.

Mechanical and corrosion properties of Al/Ti film on magnesium alloy AZ31B

Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coatings were deposited on magnesium alloy AZ31B using magnetron sputtering （MS）. The low temperature diffusion bonding behavior of the MglAl/Ti coating was investigated through SEM and its affiliated EDS. The phase structure and critical load of the coatings were examined by means of XRD and scratch tests, respectively, The results demonstrated that the bonding strength was significantly improved after a post heat treatment （HT） at a temperature of 210℃. The diffusion mechanism of the interfaces of MglAI and Al/Ti in the coating was discussed based on the analysis of formation energy of vacancies and diffusion rates. The Al/Ti dual layer enhanced the corrosion resistance of the alloy. And the HT process further increased the corrosion resistance of the coated alloy. This result implies that a post HTat a lower temperature after MS is an effective approach to enhance the bonding strength and corrosion resistance of the Al/Ti film on Mg alloys.

Study on high-reflective coatings of dif ferent designs at 532 nm

Conventional HfO2/SiO2 and Al2O3/HfO2/SiO2 double stack high reflective （HR） coatings at 532 nm are deposited by electron beam evaporation onto BK7 substrates. The laser-induced damage threshold （LIDT） of two kinds of HR coatings is tested, showing that the laser damage resistance of the double stack HR coatings （16 J/cm2） is better than that of the conventional HR coatings （12.8 J/cm2）. Besides, the optical properties, surface conditions, and damage morphologies of each group samples are characterized. The results show that laser damage resistance of conventional HR coatings is determined by absorptive defect, while nodular defect is responsible for the LIDT of double stack HR coatings.

Al diffusion coating on Mg alloy by a surface nanocrystallization enhanced CVD process

Surface nanocrystallization by mechanical attrition was used to enhance the chemical vapor deposition process.An aluminum(Al)diffusion coating was produced on AZ91 Mg alloy surface.This process was conducted at a relatively low temperature(400◦C)for a short time of 120 min.The results indicated that a continuous and dense Mg17Al12 intermetallic coating with a thickness of∼8µm formed on the Mg alloy substrate.Almost no corrosion was observed after the coated samples were immersed in 3 wt%NaCl solution for 6 h,reflecting a relatively good corrosion resistance.The formation mechanism of the Al diffusion coating is discussed based on the experimental results.