High porosity and high brittleness are the main reasons that limit the long-term service life of the alumina-titanium oxide composite coating.Herein,a metastable nanostructured aluminatitanium oxide composite coating ...High porosity and high brittleness are the main reasons that limit the long-term service life of the alumina-titanium oxide composite coating.Herein,a metastable nanostructured aluminatitanium oxide composite coating with high density and high properties was synthesized by plasma spraying of TiO_(2)-Al composite powder.The main phases of the metastable nanostructured alumina-titanium oxide wereγ-Al_(2)O_(3),TiO and AlTiO_(2).The coating,as prepared,contains various metastable microstructures,such as fine-grained,intra-/inter-granular,and"self-locking"microstructures.These metastable microstruc-tures are important for the improvement of hardness and toughness of the coating.Compared with other alumina-based composite coatings,the metastable nanostructured aluminatitanium oxide composite coating showed the most impressive overall performance.The reinforcing and toughening mechanism of the metastable alumina-titanium oxide composite coating included fine grain strengthening and self-toughening of the metastable microstructure.展开更多
Nanostructured Al_(2)O_(3)-10wt.%TiO_(2)-nCeO_(2)ceramic coatings(where n is 0 wt.%,0.2 wt.%,0.5 wt.%,and 0.8 wt.%)were prepared on a 304 stainless steel substrate using atmospheric plasma spraying.The phase compositi...Nanostructured Al_(2)O_(3)-10wt.%TiO_(2)-nCeO_(2)ceramic coatings(where n is 0 wt.%,0.2 wt.%,0.5 wt.%,and 0.8 wt.%)were prepared on a 304 stainless steel substrate using atmospheric plasma spraying.The phase composition and microstructure of the coatings were characterized using an X-ray diffractometer and a scanning electron microscope.The corrosion resistance of the coatings was as-sessed through electrochemical experiments and chloride ion corrosion tests.The results indicated that the coatings comprised both partially and fully melted regions,with spherical particles and pores present on the coating surfaces.The incorporation of CeO_(2)en-hanced the melting of the sprayed powder during the spraying process.When the CeO_(2)content was 0.2 wt.%,the melting of the sprayed powder was optimal.The porosity of the coating was minimized to 2.45%.CeO_(2)also positively influenced the grain refine-ment of the coating;at 0.2 wt.%CeO_(2),the grain size was at its minimum.The grain size of this coating was calculated to be 21.135 nm using the Scherrer formula.This coating demonstrated the best corrosion resistance,with a corrosion potential of-596.31 mV and a corrosion current density of 1.65×10^(-6)A/cm^(2),resulting in a weight loss of 0.0170 g due to chloride ion corrosion.展开更多
Tribological properties of two new DLC--monocrystalline and amorphous nanostructural coating--are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect. The friction tests were ca...Tribological properties of two new DLC--monocrystalline and amorphous nanostructural coating--are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect. The friction tests were carried out by using two test configurations： ＂ball-on-disc＂ and ＂ring-to-ring＂. Friction surfaces were coated by carbon of two types： monocrystalline and amorphous ones. As lubricants some model and commercial oils were used. It is found that the friction coefficient and its temperature dependence differ significantly for carbon films under study. The obtained results were attributed to different orientating effect of these coatings on structural ordering in boundary layers, which structure is considered as a mesophase of liquid crystals. The findings suggest that the carbon coatings with orientating effect on boundary layers are advantageous for improving antifriction characteristics and for governing processes of boundary lubrication.展开更多
The microstructure and wear performance of M203-13% TiO2 coatings prepared by plasma spraying of agglom- erated nanoparticle powders were investigated. SEM analysis showed that the as-sprayed Al2O3-TiO2 coatings compr...The microstructure and wear performance of M203-13% TiO2 coatings prepared by plasma spraying of agglom- erated nanoparticle powders were investigated. SEM analysis showed that the as-sprayed Al2O3-TiO2 coatings comprise of two kinds of typical region： fully melted region and unmelted/partially melted nanostructured region, which is different than the conventional coating with lamellar structure. It is shown that the microhardness of the nanostructured coatings was about 15%-30% higher than that of the conventional coating and the wear resistance is significantly improved, especially under a high wear load. The nanostructured coating sprayed at a lower power shows a lower wear resistance than the coatings produced at a higher power, because of the presence of pores and microstructural defects which are detrimental to the fracture toughness of the coatings.展开更多
The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted...The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted nanostructured particles. Through the adjustment of constituent and nanostructure, hardness/strength and toughness/ductility are balanced and overall properties of the structure composite are achieved.展开更多
Nanostructured and conventional Al2O3-13wt.%TiO2 ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the c...Nanostructured and conventional Al2O3-13wt.%TiO2 ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the coatings were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and microhardness measurement. Meanwhile, the friction and wear behaviors were analyzed and compared using a ball-on-disk tribometer. The results show that the conventional coating has lamellar stacking characteristic and has some pores. However, the nanostructured coating shows a bimodal microstructure, which is composed of both fully melted regions and partially melted regions. According to the microstructural difference, the partially melted regions can be divided into liquid-phase sintered regions （a three-dimensional net or skeleton-like structure： Al2O3-rich submicron particles embedded in the TiO2-rich matrix） and solid-phase sintered regions （remained nanoparticles）. The microstructural characteristics of the liquid-phase sintered region are formed due to the selective melting of TiO2 nanoparticles during plasma spraying. On the other hand, the TiO2 and Al2O3 nanoparticles of the solid-phase sintered regions are all unmelted during plasma spraying. Due to the existence of nanostructured microstructures, the nanostructured coating has a higher microhardness, a lower friction coefficient, and a better wear resistance than the conventional coating.展开更多
Thermal stability of nanostructured NiCrC coating prepared by high velocity air-fuel （HVAF） spraying of cryomilled feedstock powders was investigated. Transmission electron microscopy （TEM）, differential scanning ...Thermal stability of nanostructured NiCrC coating prepared by high velocity air-fuel （HVAF） spraying of cryomilled feedstock powders was investigated. Transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, and X-ray diffraction （XRD） were utilized for characteristic analysis. Recrystallization and normal grain growth occur when isothermal treatment is performed at 923 K （0.55 TM） for up to 100 h, and the average grain size increases from initial 41 nm for as-deposited state to around 100 nm for nearly equilibrium state. Isochronal treatment at 823 K and 1023 K was also conducted for comparison. Accordingly, for 0.49 to 0.61 T/TM, the time exponent n deduced from D^1/n - D0^1/n = kt increases from 0.15 to 0.30. The observed high thermal stability is attributed primarily to a Zener pinning mechanism arising from the fine Cr2O3 dispersions and the solute drag effect as well.展开更多
A new nanostructured ZrB_(2)-ZrC composite coating with ZrB_(2)-ZrC nanoscale eutectic and ZrB2+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B4 C-Al composite powder.The thermal analysis,quen...A new nanostructured ZrB_(2)-ZrC composite coating with ZrB_(2)-ZrC nanoscale eutectic and ZrB2+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B4 C-Al composite powder.The thermal analysis,quenching experiments and microstructure characterization were investigated and the formation mechanism of the bimodal in-situ microstructure was revealed.Al contributed to the liquid phase separation of molten droplets,which is the key to forming ZrB2+Amorphous microstructure.The formation of coating followed reaction-melting-liquid separation-deposition and solidification mechanism.The nanostructured ZrB_(2)-ZrC composite coating with Al-O intergranular amorphous phase has excellent mechanical properties.The uniform nano-grains improved the hardness and the toughness of the ZrB_(2)-ZrC eutectic.The ZrB_(2)+Al-O amorphous microstructure obtained high toughness and the toughening mechanism was the crack deflection and crack branching caused by intergranular Al-O amorphous phase.展开更多
A multi-functional micro-arc plasma spraying system was developed according to aerodynamics and plasma spray theory. The soft switch IGBT （Insulated Gate Bipolar Transistor） invert technique, micro-computer control ...A multi-functional micro-arc plasma spraying system was developed according to aerodynamics and plasma spray theory. The soft switch IGBT （Insulated Gate Bipolar Transistor） invert technique, micro-computer control technique, convergent-divergent nozzle structure and axial powder feeding techniques have been adopted in the design of the micro-arc plasma spraying system. It is not only characterized by a small volume, a light weight, highly accurate control, high deposition efficiency and high reliability, but also has multi-functions in plasma spraying, welding and quenching. The experimental results showed that the system can produce a supersonic flame at a low power, spray Al2O3 particles at an average speed up to 430 m/s, and make nanostructured AT13 coatings with an average bonding strength of 42.7 MPa. Compared to conventional 9M plasma spraying with a higher power, the coatings with almost the same properties as those by conventional plasma spray can be deposited by multi-functional micro-arc plasma spraying with a lower power plasma arc due to an improved power supply design, spray gun structure and powder feeding method. Moreover, this system is suitable for working with thin parts and undertaking on site repairs, and as a result, the application of plasma spraying will be greatly extended.展开更多
Orthopedic infections pose severe societal and economic burden and interfere with the capability of the implanted devices to integrate in the host bone,thus significantly increasing implants failure rate.To address in...Orthopedic infections pose severe societal and economic burden and interfere with the capability of the implanted devices to integrate in the host bone,thus significantly increasing implants failure rate.To address infection and promote integration,here nanostructured antibacterial and bioactive thin films are proposed,obtained,for the first time,by Ionized Jet Deposition(IJD)of silver-substituted tricalcium phosphate(Ag-TCP)targets on titanium.Coatings morphology,composition and mechanical properties are characterized and proof-of-concept of biocompatibility is shown.Antimicrobial efficacy is investigated against four Gram positive and Gram negative bacterial strains and against C.albicans fungus,by investigating the modifications in planktonic bacterial growth in the absence and presence of silver.Then,for all bacterial strains,the capability of the film to inhibit bacterial adhesion is also tested.Results indicate that IJD permits a fine control over films composition and morphology and deposition of films with suitable mechanical properties.Biological studies show a good efficacy against Escherichia coli,Staphylococcus aureus,Pseudomonas aeruginosa,Enterococcus faecalis and against fungus Candida albicans,with evidences of efficacy against planktonic growth and significant reduction of bacterial cell adhesion.No cytotoxic effects are evidenced for equine adipose tissue derived mesenchymal stem cells(ADMSCs),as no reductions are caused to cells viability and no interference is assessed in cells differentiation towards osteogenic lineage,in the presence of silver.Instead,thanks to nanostructuration and biomimetic composition,tricalcium phosphate(TCP)coatings favor cells viability,also when silver-substituted.These findings show that silver-substituted nanostructured coatings are promising for orthopedic implant applications.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52371063 and 52072110)the Natural Science Foundation of Hebei Province(No.E2018202034)+1 种基金the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.236Z7610G)the Graduate Innovation Project of Hebei Province(No.CXZZBS2022035).
文摘High porosity and high brittleness are the main reasons that limit the long-term service life of the alumina-titanium oxide composite coating.Herein,a metastable nanostructured aluminatitanium oxide composite coating with high density and high properties was synthesized by plasma spraying of TiO_(2)-Al composite powder.The main phases of the metastable nanostructured alumina-titanium oxide wereγ-Al_(2)O_(3),TiO and AlTiO_(2).The coating,as prepared,contains various metastable microstructures,such as fine-grained,intra-/inter-granular,and"self-locking"microstructures.These metastable microstruc-tures are important for the improvement of hardness and toughness of the coating.Compared with other alumina-based composite coatings,the metastable nanostructured aluminatitanium oxide composite coating showed the most impressive overall performance.The reinforcing and toughening mechanism of the metastable alumina-titanium oxide composite coating included fine grain strengthening and self-toughening of the metastable microstructure.
基金supported by the National Natural Science Foundation of China(Grant No.52375387).
文摘Nanostructured Al_(2)O_(3)-10wt.%TiO_(2)-nCeO_(2)ceramic coatings(where n is 0 wt.%,0.2 wt.%,0.5 wt.%,and 0.8 wt.%)were prepared on a 304 stainless steel substrate using atmospheric plasma spraying.The phase composition and microstructure of the coatings were characterized using an X-ray diffractometer and a scanning electron microscope.The corrosion resistance of the coatings was as-sessed through electrochemical experiments and chloride ion corrosion tests.The results indicated that the coatings comprised both partially and fully melted regions,with spherical particles and pores present on the coating surfaces.The incorporation of CeO_(2)en-hanced the melting of the sprayed powder during the spraying process.When the CeO_(2)content was 0.2 wt.%,the melting of the sprayed powder was optimal.The porosity of the coating was minimized to 2.45%.CeO_(2)also positively influenced the grain refine-ment of the coating;at 0.2 wt.%CeO_(2),the grain size was at its minimum.The grain size of this coating was calculated to be 21.135 nm using the Scherrer formula.This coating demonstrated the best corrosion resistance,with a corrosion potential of-596.31 mV and a corrosion current density of 1.65×10^(-6)A/cm^(2),resulting in a weight loss of 0.0170 g due to chloride ion corrosion.
文摘Tribological properties of two new DLC--monocrystalline and amorphous nanostructural coating--are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect. The friction tests were carried out by using two test configurations： ＂ball-on-disc＂ and ＂ring-to-ring＂. Friction surfaces were coated by carbon of two types： monocrystalline and amorphous ones. As lubricants some model and commercial oils were used. It is found that the friction coefficient and its temperature dependence differ significantly for carbon films under study. The obtained results were attributed to different orientating effect of these coatings on structural ordering in boundary layers, which structure is considered as a mesophase of liquid crystals. The findings suggest that the carbon coatings with orientating effect on boundary layers are advantageous for improving antifriction characteristics and for governing processes of boundary lubrication.
文摘The microstructure and wear performance of M203-13% TiO2 coatings prepared by plasma spraying of agglom- erated nanoparticle powders were investigated. SEM analysis showed that the as-sprayed Al2O3-TiO2 coatings comprise of two kinds of typical region： fully melted region and unmelted/partially melted nanostructured region, which is different than the conventional coating with lamellar structure. It is shown that the microhardness of the nanostructured coatings was about 15%-30% higher than that of the conventional coating and the wear resistance is significantly improved, especially under a high wear load. The nanostructured coating sprayed at a lower power shows a lower wear resistance than the coatings produced at a higher power, because of the presence of pores and microstructural defects which are detrimental to the fracture toughness of the coatings.
文摘The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted nanostructured particles. Through the adjustment of constituent and nanostructure, hardness/strength and toughness/ductility are balanced and overall properties of the structure composite are achieved.
基金supported by the National Natural Science Foundation of China (Nos. 59975046 and 50305010)the Key Natural Science Foundation of Ji-angsu Province, China (No. BK2004005)
文摘Nanostructured and conventional Al2O3-13wt.%TiO2 ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the coatings were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and microhardness measurement. Meanwhile, the friction and wear behaviors were analyzed and compared using a ball-on-disk tribometer. The results show that the conventional coating has lamellar stacking characteristic and has some pores. However, the nanostructured coating shows a bimodal microstructure, which is composed of both fully melted regions and partially melted regions. According to the microstructural difference, the partially melted regions can be divided into liquid-phase sintered regions （a three-dimensional net or skeleton-like structure： Al2O3-rich submicron particles embedded in the TiO2-rich matrix） and solid-phase sintered regions （remained nanoparticles）. The microstructural characteristics of the liquid-phase sintered region are formed due to the selective melting of TiO2 nanoparticles during plasma spraying. On the other hand, the TiO2 and Al2O3 nanoparticles of the solid-phase sintered regions are all unmelted during plasma spraying. Due to the existence of nanostructured microstructures, the nanostructured coating has a higher microhardness, a lower friction coefficient, and a better wear resistance than the conventional coating.
基金the National High Technology Research and Development Program of China (No.2002AA331080)
文摘Thermal stability of nanostructured NiCrC coating prepared by high velocity air-fuel （HVAF） spraying of cryomilled feedstock powders was investigated. Transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, and X-ray diffraction （XRD） were utilized for characteristic analysis. Recrystallization and normal grain growth occur when isothermal treatment is performed at 923 K （0.55 TM） for up to 100 h, and the average grain size increases from initial 41 nm for as-deposited state to around 100 nm for nearly equilibrium state. Isochronal treatment at 823 K and 1023 K was also conducted for comparison. Accordingly, for 0.49 to 0.61 T/TM, the time exponent n deduced from D^1/n - D0^1/n = kt increases from 0.15 to 0.30. The observed high thermal stability is attributed primarily to a Zener pinning mechanism arising from the fine Cr2O3 dispersions and the solute drag effect as well.
基金supports of the National Natural Science Foundation of China(Nos.52371063 and 52072110)the Natural Science Foundation of Hebei Province(No.E2018202034)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.236Z7610G).
文摘A new nanostructured ZrB_(2)-ZrC composite coating with ZrB_(2)-ZrC nanoscale eutectic and ZrB2+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B4 C-Al composite powder.The thermal analysis,quenching experiments and microstructure characterization were investigated and the formation mechanism of the bimodal in-situ microstructure was revealed.Al contributed to the liquid phase separation of molten droplets,which is the key to forming ZrB2+Amorphous microstructure.The formation of coating followed reaction-melting-liquid separation-deposition and solidification mechanism.The nanostructured ZrB_(2)-ZrC composite coating with Al-O intergranular amorphous phase has excellent mechanical properties.The uniform nano-grains improved the hardness and the toughness of the ZrB_(2)-ZrC eutectic.The ZrB_(2)+Al-O amorphous microstructure obtained high toughness and the toughening mechanism was the crack deflection and crack branching caused by intergranular Al-O amorphous phase.
文摘A multi-functional micro-arc plasma spraying system was developed according to aerodynamics and plasma spray theory. The soft switch IGBT （Insulated Gate Bipolar Transistor） invert technique, micro-computer control technique, convergent-divergent nozzle structure and axial powder feeding techniques have been adopted in the design of the micro-arc plasma spraying system. It is not only characterized by a small volume, a light weight, highly accurate control, high deposition efficiency and high reliability, but also has multi-functions in plasma spraying, welding and quenching. The experimental results showed that the system can produce a supersonic flame at a low power, spray Al2O3 particles at an average speed up to 430 m/s, and make nanostructured AT13 coatings with an average bonding strength of 42.7 MPa. Compared to conventional 9M plasma spraying with a higher power, the coatings with almost the same properties as those by conventional plasma spray can be deposited by multi-functional micro-arc plasma spraying with a lower power plasma arc due to an improved power supply design, spray gun structure and powder feeding method. Moreover, this system is suitable for working with thin parts and undertaking on site repairs, and as a result, the application of plasma spraying will be greatly extended.
基金Dr.Gabriela Graziani acknowledges funding from the project Starting Grant SG-2018-12367059financed by the Italian Ministry of Health(BANDO RICERCA FINALIZZATA 2018).
文摘Orthopedic infections pose severe societal and economic burden and interfere with the capability of the implanted devices to integrate in the host bone,thus significantly increasing implants failure rate.To address infection and promote integration,here nanostructured antibacterial and bioactive thin films are proposed,obtained,for the first time,by Ionized Jet Deposition(IJD)of silver-substituted tricalcium phosphate(Ag-TCP)targets on titanium.Coatings morphology,composition and mechanical properties are characterized and proof-of-concept of biocompatibility is shown.Antimicrobial efficacy is investigated against four Gram positive and Gram negative bacterial strains and against C.albicans fungus,by investigating the modifications in planktonic bacterial growth in the absence and presence of silver.Then,for all bacterial strains,the capability of the film to inhibit bacterial adhesion is also tested.Results indicate that IJD permits a fine control over films composition and morphology and deposition of films with suitable mechanical properties.Biological studies show a good efficacy against Escherichia coli,Staphylococcus aureus,Pseudomonas aeruginosa,Enterococcus faecalis and against fungus Candida albicans,with evidences of efficacy against planktonic growth and significant reduction of bacterial cell adhesion.No cytotoxic effects are evidenced for equine adipose tissue derived mesenchymal stem cells(ADMSCs),as no reductions are caused to cells viability and no interference is assessed in cells differentiation towards osteogenic lineage,in the presence of silver.Instead,thanks to nanostructuration and biomimetic composition,tricalcium phosphate(TCP)coatings favor cells viability,also when silver-substituted.These findings show that silver-substituted nanostructured coatings are promising for orthopedic implant applications.
