To improve the performance and reliability of microelectromechanical system＇s devices, it is necessary to understand the effect of friction which exists in the majority of microelectromechanical systems （MEMS） with...To improve the performance and reliability of microelectromechanical system＇s devices, it is necessary to understand the effect of friction which exists in the majority of microelectromechanical systems （MEMS） with a large ratio of surface area to their volume. The model of electrostatic tangential force of the shuttle in laterally driven comb microresonator is established based on the rule of energy conservation. The effects of microscale, surface roughness, applied voltage, and micro asperities or dents or holes formed in fabrication are investigated, and the electrostatic resistance between two charged moving plates is analyzed. The analytic results are coincident well with those of ANSYS simulation. It is found that the electrostatic resistance becomes high as the increase of the ratio of the shuttle width to the gap between moving plates and the relative surface roughness or the increment of the applied voltage.展开更多
This paper demonstrates the influence of deposition parameters(temperature,power and time)and stoichiometric composition of thin aluminum nitride(AIN)coatings,the thickness of which varied from 320 to 1100 nm deposite...This paper demonstrates the influence of deposition parameters(temperature,power and time)and stoichiometric composition of thin aluminum nitride(AIN)coatings,the thickness of which varied from 320 to 1100 nm deposited by DC reactive magnetron sputtering on their microstructure,mechanical and microtribological properties.The investigation revealed that high-deposition power(150W)and temperature(200℃)lead to sputtering of coatings with high roughness,low mechanical and high microtribological properties.Such a phenomenon occurred due to the formation of a coarse-grained structure,high porosity and dendritic growth of the coating,which was observed on their cross-sections.Reducing the deposition temperature to 20℃and power to 80-100 W allowed to obtain a fine-crystalline structure demonstrating low-roughness values with crystallites evenly and compactly distributed over the surface.Such coatings showed higher mechanical and low microtribological properties.Surface resistivity was lower on coatings with a fine crystalline structure and correlated with the nitrogen content of the coating.In the course of the research,it was demonstrated that the optimal combination of microstructure,mechanical,microtribological properties and electrical resistivity for practical use in micro-and nanosensory applications may be achieved for the AIN coating with the thickness of 320 nm and 29.71 at.%N,deposited at 20℃,100 W and 20min.Such a coating possesses the highest values of mechanical properties,low roughness and specific surface resistance,as well as low coefficient of friction and specific volumetric wear compared toall coatings under study.展开更多
We report on the frictional properties of epitaxial graphene on SiC in ultra high vacuum.Measurements have been performed using a microtribometer in the load regime of 0.5 to 1 mN.We observed that a ruby sphere slidin...We report on the frictional properties of epitaxial graphene on SiC in ultra high vacuum.Measurements have been performed using a microtribometer in the load regime of 0.5 to 1 mN.We observed that a ruby sphere sliding against graphene results in very low friction coefficients ranging from 0.02 to 0.05.The friction and also the stability of the graphene layer is higher than that under similar conditions in ambient conditions.The friction shows a load dependence.Finally it was found that graphene masks the frictional anisotropy which was observed on the SiC surface.展开更多
TiB2 thin film was deposited by laser-arc deposition method on the surface of single crystalline Silicon. The morphology, composition, structure and microtribological properties of the film were studied by using XPS, ...TiB2 thin film was deposited by laser-arc deposition method on the surface of single crystalline Silicon. The morphology, composition, structure and microtribological properties of the film were studied by using XPS, XRD and atomic force/friction force microscope (AFM/FFM). The results show that TiB2 (100) preferred growth on the Si(100) substrate, TiB2(001) preferred growth on the Si(111) substrate. The TiB2 thin film was composed of TiB2 and a smali amount of TiO2. The friction coefficient of TiB2 film on substrates Si (100) and Si(111) in microtribological process were 0.087 and 0.073, respectively. TiB2 thin film displayed distinct ability of anti-scratch and wear-resistance.展开更多
Nowadays it is accepted that the friction force is a combined effect arising from various phenomena:adhesive forces,capillary forces,contact elasticity,topography,surface chemistry,and generation of a third body,etc.A...Nowadays it is accepted that the friction force is a combined effect arising from various phenomena:adhesive forces,capillary forces,contact elasticity,topography,surface chemistry,and generation of a third body,etc.Any of them can dominate depending on the experimental force and length scales of the study.Typical forces in macro-tribology are in the Newtons,while are reduced to milli-/micro-Newtons,and nano-Newtons in micro-and nano-tribology,respectively.In this paper,experimental friction results from fullerene like CNx films and single-crystal Si at the three scales will be discussed.The complex and broad variety of processes and phenomena connected with the dry friction coefficient at the macro-,micro-,and nano-scale point of view will be highlighted.展开更多
In this study,the protective effects of two food hydrocolloids,Xanthan gum and Arabic gum,on dental erosion are investigated from the perspective of the nanomechanical properties and microtribological behavior of acid...In this study,the protective effects of two food hydrocolloids,Xanthan gum and Arabic gum,on dental erosion are investigated from the perspective of the nanomechanical properties and microtribological behavior of acid-eroded enamel.Enamel specimens prepared from extracted human teeth were immersed in citric acid solution(CAS),CAS with 0.03%w/v Xanthan gum and CAS with 0.03%w/v Arabic gum,respectively,for 10 min to obtain three groups of eroded specimens.The nanomechanical properties and microtribological behavior of enamel were examined using nano-indentation/scratch techniques.The results show that compared with Arabic gum,Xanthan gum inhibits enamel surface demineralization and acid permeation more effectively because of a more uniform and denser adsorption on the surface of the enamel.The impairment of the nanomechanical and microtribological properties of the enamel surface by acid erosion is mitigated more significantly by adding trace amounts of Xanthan gum than Arabic gum.In summary,adding trace food hydrocolloids reduces enamel surface demineralization and inhibits acid permeation to mitigate the influence of erosion on the mechanical and tribological properties of enamel.The adsorption state of food hydrocolloids is the determining factor in the permeability of acid agents into the enamel and plays a significant role in preventing dental erosion.展开更多
基金National Natural Science Foundation of China(No.50135040)Science Foundation of Shanghai Municipality Education Commission through the Key Discipline Program(No.970104).
文摘To improve the performance and reliability of microelectromechanical system＇s devices, it is necessary to understand the effect of friction which exists in the majority of microelectromechanical systems （MEMS） with a large ratio of surface area to their volume. The model of electrostatic tangential force of the shuttle in laterally driven comb microresonator is established based on the rule of energy conservation. The effects of microscale, surface roughness, applied voltage, and micro asperities or dents or holes formed in fabrication are investigated, and the electrostatic resistance between two charged moving plates is analyzed. The analytic results are coincident well with those of ANSYS simulation. It is found that the electrostatic resistance becomes high as the increase of the ratio of the shuttle width to the gap between moving plates and the relative surface roughness or the increment of the applied voltage.
基金support of the Belarus Republican Foundation for Fundamental Research(Grant Nos.T23RNF-132 and T17KIG-009)Nikolaev A.acknowledges the support of the Russian Science Foundation(Grant No.23-49-10062,https://rscf.ru/project/23-49-10062/).
文摘This paper demonstrates the influence of deposition parameters(temperature,power and time)and stoichiometric composition of thin aluminum nitride(AIN)coatings,the thickness of which varied from 320 to 1100 nm deposited by DC reactive magnetron sputtering on their microstructure,mechanical and microtribological properties.The investigation revealed that high-deposition power(150W)and temperature(200℃)lead to sputtering of coatings with high roughness,low mechanical and high microtribological properties.Such a phenomenon occurred due to the formation of a coarse-grained structure,high porosity and dendritic growth of the coating,which was observed on their cross-sections.Reducing the deposition temperature to 20℃and power to 80-100 W allowed to obtain a fine-crystalline structure demonstrating low-roughness values with crystallites evenly and compactly distributed over the surface.Such coatings showed higher mechanical and low microtribological properties.Surface resistivity was lower on coatings with a fine crystalline structure and correlated with the nitrogen content of the coating.In the course of the research,it was demonstrated that the optimal combination of microstructure,mechanical,microtribological properties and electrical resistivity for practical use in micro-and nanosensory applications may be achieved for the AIN coating with the thickness of 320 nm and 29.71 at.%N,deposited at 20℃,100 W and 20min.Such a coating possesses the highest values of mechanical properties,low roughness and specific surface resistance,as well as low coefficient of friction and specific volumetric wear compared toall coatings under study.
基金We thank Thomas Seyller of the University of Erlangen-Nürnberg for samples preparation and acknowledge support from the Federal Ministry of Education and Research(BMBF No.03X0107D)。
文摘We report on the frictional properties of epitaxial graphene on SiC in ultra high vacuum.Measurements have been performed using a microtribometer in the load regime of 0.5 to 1 mN.We observed that a ruby sphere sliding against graphene results in very low friction coefficients ranging from 0.02 to 0.05.The friction and also the stability of the graphene layer is higher than that under similar conditions in ambient conditions.The friction shows a load dependence.Finally it was found that graphene masks the frictional anisotropy which was observed on the SiC surface.
基金This work was supported by the National Natural Science Foundation of China(Grant No.50135040).
文摘TiB2 thin film was deposited by laser-arc deposition method on the surface of single crystalline Silicon. The morphology, composition, structure and microtribological properties of the film were studied by using XPS, XRD and atomic force/friction force microscope (AFM/FFM). The results show that TiB2 (100) preferred growth on the Si(100) substrate, TiB2(001) preferred growth on the Si(111) substrate. The TiB2 thin film was composed of TiB2 and a smali amount of TiO2. The friction coefficient of TiB2 film on substrates Si (100) and Si(111) in microtribological process were 0.087 and 0.073, respectively. TiB2 thin film displayed distinct ability of anti-scratch and wear-resistance.
基金The support of the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University(Faculty Grant SFO-Mat-LiU#2009-00971)is highly appreciated。
文摘Nowadays it is accepted that the friction force is a combined effect arising from various phenomena:adhesive forces,capillary forces,contact elasticity,topography,surface chemistry,and generation of a third body,etc.Any of them can dominate depending on the experimental force and length scales of the study.Typical forces in macro-tribology are in the Newtons,while are reduced to milli-/micro-Newtons,and nano-Newtons in micro-and nano-tribology,respectively.In this paper,experimental friction results from fullerene like CNx films and single-crystal Si at the three scales will be discussed.The complex and broad variety of processes and phenomena connected with the dry friction coefficient at the macro-,micro-,and nano-scale point of view will be highlighted.
基金This work was supported by the National Natural Science Foundation of China(Nos.51535010 and 51305366)the Fundamental Research Funds for the Central Universities(No.2682018QY01).
文摘In this study,the protective effects of two food hydrocolloids,Xanthan gum and Arabic gum,on dental erosion are investigated from the perspective of the nanomechanical properties and microtribological behavior of acid-eroded enamel.Enamel specimens prepared from extracted human teeth were immersed in citric acid solution(CAS),CAS with 0.03%w/v Xanthan gum and CAS with 0.03%w/v Arabic gum,respectively,for 10 min to obtain three groups of eroded specimens.The nanomechanical properties and microtribological behavior of enamel were examined using nano-indentation/scratch techniques.The results show that compared with Arabic gum,Xanthan gum inhibits enamel surface demineralization and acid permeation more effectively because of a more uniform and denser adsorption on the surface of the enamel.The impairment of the nanomechanical and microtribological properties of the enamel surface by acid erosion is mitigated more significantly by adding trace amounts of Xanthan gum than Arabic gum.In summary,adding trace food hydrocolloids reduces enamel surface demineralization and inhibits acid permeation to mitigate the influence of erosion on the mechanical and tribological properties of enamel.The adsorption state of food hydrocolloids is the determining factor in the permeability of acid agents into the enamel and plays a significant role in preventing dental erosion.
