•FC-TC4 and AC-TC4 alloys with more content of α phase were obtained by heat treatment.•Nano twins of TiV and TiAl3 were formed separately in FC-TC4 and AC-TC4 alloys.•Refined recrystallized grain ...and more high-angle grain boundaries of AC-TC4 alloy enhanced its mechanical properties.•The passivating ability of AC-TC4 alloy was best among three samples because of its microstructure.•The cavitation erosion resistance of Ti6Al4V alloys in artificial seawater was closely related to their mechanical properties and passivating ability.
The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application. On the basis of as-received Ti6Al4V(TC4) alloy, FC-TC4 and AC-TC4 alloys were prepared by heat treatment with the cooling method of a furnace and atmospheric environment, respectively. Then the microstructure evolutions of three samples were scrutinized and the effect of microstructure on their cavitation erosion and corrosion resistance was explored. The results showed that more recrystallized grains formed as well as its content of α grains and high-angle grain boundaries increased in AC-TC4 alloy. To FC-TC4 alloy, there was obvious grain growth apart from recrystallization. Moreover, many nanotwins of TiV and TiAl3 were formed separately in FC-TC4 and AC-TC4 alloys due to the dislocation migration during heat treatment. The microstructure evolution led the hardness and elastic modulus of AC-TC4 alloy were the best, followed by FC-TC4 alloy, that of TC4 were the worst. Similarly, passivating ability of AC-TC4 alloy was the best among three samples because of its microstructure. Although cracks extended along the grain boundaries under the action of continual cavitation erosion, the passivation film formed by TiO2 and Al2O3 would enhance their resistance to further corrosion and cavitation erosion in artificial seawater.
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Carbon dots (CDs), as the most important type of carbon-based material, have been widely used in many fields because of their excellent properties. In particular, multicolor fluorescent CDs with high ...photoluminescence quantum yield are the focus of active research. Herein, red, green and blue CDs (RGB CDs) were successfully synthesized by a solvothermal method from
-phenylenediamine under different reaction conditions. The RGB-CDs have stable optical properties and significant photoluminescence characteristics. Structural and elemental analyses propose a conjugated structure and the surface state of the CDs as the main causes for the different color emission of RGB-CDs. In addition, a white fluorescent CD solution was prepared by mixing these multicolor fluorescent CDs in appropriate proportions.
Fe-based amorphous coatings were deposited on 1Cr18Ni9Ti stainless steel substrates by high velocity oxy-fuel spraying (HVOF) at different spraying parameters. It has been found that the amorphous ...phase content of the as-sprayed coatings rises initially and declines later with the increase of spraying power, which is due to the competition between melting and oxidation degree of the feedstock powder and the thermal radiation effect of the flame. Besides, the microhardness and wear resistance of the as-sprayed coatings increase with increasing spraying power, which is attributed to the enhancement of splat-to-splat binding force at elevated spraying power. Moreover, the three kinds of Fe-based amorphous coatings obtained under different spraying parameters all exhibit better corrosion resistance than 316L stainless steel. Particularly, the Fe-based amorphous coating deposited at an intermediate spraying power exhibits dense structure as well as the highest amorphous phase content, the best corrosion resistance, and very good wear resistance, showing promising potential as a candidate for surface protective and anticorrosion coatings for the stainless steel.
•Revealing the correlation among parameters and microstructure of Fe-based coatings•The amorphous phase content of the Fe-based coatings varies with varying spray power.•The wear resistance of Fe-based coatings increases with increasing spraying power.•Fe-based coatings exhibit better corrosion resistance than 316L stainless steel.
A type of CoMoCrSi coatings were fabricated by using HVOF technique, and the microstructures, mechanical properties and tribological behaviors at room temperature (RT) of the coatings annealed at ...800 °C for different time were investigated in detail. Annealed CoMoCrSi coatings exhibited better crystallization and more compact microstructures compared to as-sprayed coatings. The porosity of the annealed coatings reduced to 0.32–0.2%, and adhesive strength increased to 63.8–68.5 MPa, both of that were all reached at an equivalent level with the variation of the annealed time. The surface microhardness could be enhanced from 902.8 HV
0.3
for the as-sprayed coating to 1237.6 HV
0.3
for the coating annealed for 10 h, which could be attribute to more compact microstructures and hard nano-sized Cr
2
O
3
layer, that resisted indentation effectively. With the increasing of sliding distance at room temperature, the friction coefficients of the annealed coatings reached at 0.39–0.4, and the wear rates decreased to 0.88–1.59 × 10
–6
mm
3
N
−1
m
−1
, demonstrating enhanced tribological performance of the CoMoCrSi coating after heat treatment. Numerous metallic oxides, i.e., Cr
2
O
3
played a critical role in sustaining and anti-wear, and oxides, i.e., Co
3
O
4
, MoO
3
, and CoMoO
4
transferred to the Al
2
O
3
pair surface and formed a continuous transfer film during the friction test at RT, which directly reduced friction and leading to a low friction coefficient and wear rate.
Adaptive NiCrAlY–Ag–Mo composite coating was deposited by atmospheric plasma spraying and its tribological properties from 20°C to 800°C under unlubricated conditions were evaluated using CSM high ...temperature tribometer. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the coating and the corresponding wear tracks to determine the lubrication mechanisms. The results showed that NiCrAlY–Ag–Mo composite coating exhibited low friction coefficients around 0.3 in the entire temperature range and its wear rates were at the order of 10−5mm3/Nm at all test temperatures. Characterization of NiCrAlY–Ag–Mo coating revealed that silver provided lubrication at temperatures below 400°C. Silver molybdate and molybdenum oxide, which were formed as the temperature raised, act as lubricants at higher temperature (above 400°C). Meanwhile, the formation mechanism of silver molybdate and molybdenum oxide was also briefly discussed.
•Adaptive NiCrAlY–Ag–Mo composite coating was firstly produced by atmospheric plasma spraying technology.•The composite coating exhibited show good cohesive strength and low porosity.•The composite coating shows stable and low friction coefficients around 0.3 from 20°C to 800°C.
Carbon dots (CDs) are widely used nanomaterials that not only exhibit good biocompatibility and photostability, but also benefit from a simple preparation process and easy functionalization, making ...them promising for broad applications in the fields of heavy metal ion detection and optoelectronic devices. Based on the excellent optical properties of CDs and the current situation of increasing energy shortages, this paper selects the natural polyphenolic compound tannic acid (TA) found in biomass materials as the carbon source and innovatively adopts a simple and convenient solvent-free pyrolysis method without auxiliary reagents or solvents. The CDs with good water solubility and certain fluorescence properties were directly prepared under the condition of high temperature, and the obtained CDs exhibited blue fluorescence, and a high QY of 35.4% was obtained at 300 °C. The analysis and results demonstrate the selectivity of these CDs for the detection of various metal ion solutions. In particular, these CDs are sensitive to Ni2+ and can be used as fluorescent sensors for the efficient and sustainable detection of Ni2+, whereas previous sensors were often specific to Fe3+ and Hg2+. Thus, a new sensing technique has been developed for the detection of Ni2+ to achieve more sensitive and rapid detection.
Iron-based metallic glass coatings (denoted as FeWCrNiMoBSiC) were prepared on 1Cr18Ni9Ti stainless steel cylinders by atmospheric plasma spraying at different parameters. The morphology, ...microstructure, and crystalline structure of as-prepared Fe-based metallic glass coatings were analyzed by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. A Pycnometer and a Vickers hardness tester were adopted to measure the porosity and microhardness of iron-based metallic glass coatings. Moreover, differential scanning calorimetry analysis was conducted to investigate the crystallization behavior of various iron-based metallic glass coatings, and a ball-on-disk tribometer was performed to evaluate the tribological properties of the coatings coupled with silicon nitride ceramic balls under unlubricated conditions. It has been found that the microhardness of iron-based metallic glass coatings increases with increasing plasma arc power, which is related to the degree of melting of feedstock powders and the compactness of as-prepared coatings. Besides, the phase compositions of as-sprayed coatings consist of amorphous structure and limited crystalline structure, and the contents of the amorphous structure and crystalline structure vary with plasma arc power. Moreover, iron-based metallic glass coatings deposited at different plasma arc powers show similar steady-state friction coefficients (0.8–0.9), but their wear rate varies with varying plasma arc power. Particularly, iron-based metallic glass coating with next to the highest hardness exhibits the best anti-wear ability, which is the outcome of the compromise between the hardness and brittle fracture as well as abrasive wear of the coatings during sliding process.
•The compactness of iron-based coatings is ameliorated at elevated spraying power.•The phase compositions of iron-based coatings include amorphous and crystalline structures.•Iron-based coatings deposited at different spraying powers show similar steady-state friction coefficients.•The wear rate of iron-based coatings varies with varying spraying power.
Carbon dots (CDs), as a new type of photoluminescent nanomaterial, have attracted extensive attention in various fields because of their unique luminescence properties. However, CDs will exhibit ...fluorescence quenching in the solid state or aggregate state, which limits their application. In this paper, a unique strategy is proposed to regulate solutions to achieve multicolour fluorescence of CDs in the solid state. We report the successful preparation of orange, green and blue solid fluorescent CDs using citric acid, urea and phenylethylamine as precursors and methanol, ethanol and water as solvents, respectively. The solid-state fluorescence of CDs may be caused by the linkage of the phenylethyl structure to the surface of CDs during formation, which effectively disperses the CDs and prevents π–π interactions between graphitized nuclei. Meanwhile, multicolour solid fluorescent CDs are realized by adjusting the solvent in the preparation process. Based on the excellent fluorescence properties of CDs, orange, green and blue light-emitting diodes (LEDs) are prepared. A white LED (WLED) can be obtained by mixing the three colours of solid fluorescent CDs, which shows the application potential of CDs in display lighting equipment.
Adding nano particles can significantly improve the mechanical properties and wear resistance of thermal sprayed Al2O3 coating. However, it still remains a challenge to uniformly incorporate nano ...particles into traditional coatings due to their bad dispersibility. In the present work, nanometer Al2O3 (n-Al2O3) powders modified by KH-560 silane coupling agent were introduced into micrometer Al2O3 (m-Al2O3) powders by ultrasonic dispersion to afford nano/micro composite feedstock, and then four resultant coatings (weight fraction of n-Al2O3: 0%, 3%, 5% and 10%) were fabricated by atmospheric plasma spraying. The features and constitutes of feedstock and as-sprayed coatings, as well as their porosity, bonding strength, microhardness and frictional behaviors were investigated in detail. Results show that the nano/micro composite feedstock with uniform microstructure can be better melted in the spraying process, thereby obtaining coatings with denser microstructure, higher hardness and bonding strength. Added n-Al2O3 has no obvious effect on the friction coefficient of composite coatings, whereas can improve their wear-resistant and reduce the worn degree of counterpart. The wear mechanism of traditional coating is brittle fracture and lamellar peeling, while that of composite coating with weight fraction of n-Al2O3 of 10% is adhesive wear.
Cavitation damage is a concern for stainless steel and other metals in seawater environments, and new coatings are needed to resist such surface damage in that kind of environment. Consequently, a ...NiCr alloy coating, a WC–17Co/NiCr composite coating, a Fe-based metallic glass coating, a WC–(W,Cr)2C–Ni cermet coating, and a WC–17Co cermet coating were prepared on metal alloy substrates using high velocity oxy-fuel spraying (HVOF). The microstructure and phase composition of as-sprayed coatings and substrates were analyzed using optical microscopy and X-ray diffraction. Vicker's microindentation hardness was measured as well. The cavitation erosion behavior of the five kinds of HVOF-sprayed coatings and three kinds of alloys (316 stainless steel, TC4 titanium alloy and ZL101 aluminum alloy) in both deionized water and artificial seawater was evaluated according to ASTM standard method G 32-10. The corrosion behavior of the alloys and HVOF-sprayed coatings in artificial seawater was evaluated by potentiodynamic polarization tests to reveal the correlation between corrosion and cavitation behavior. Based on the test results, an analysis of the microstructural damage processes, and the cavitation–corrosion synergism of the coatings, the WC–17Co cermet coating was found to be the most promising coating to prevent metallic substrates from cavitation damage in seawater.
•Metallographic structure has an important effect on cavitation erosion behavior of alloys.•Porosity and hardness affect cavitation erosion behavior of HVOF-sprayed coatings to some extent.•Fe-based metallic glass coating shows good cavitation erosion behavior in deionized water.•Chemical action of artificial seawater affects cavitation erosion behavior of various materials.•WC–17Co cermet coating has the best cavitation erosion resistance in artificial seawater.
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