Deposition and Characterization of Multilayer DLC/BN Films

In this article, the results obtained from a study on multilayer diamond-like carbon and boron nitride (DLC/BN) films are reported. The microstructure, atomic concentration, hardness and friction coefficient of the films were characterized using transmission electron microscopy, auger electron microscopy, nano-indentation measurements and ball-on-disk friction testing. The effects of bilayer thickness and substrate bias on film growth were investigated. All multilayer films showed alternate DLC and BN layers, except the 2- and 4-nm bilayer of multilayer DLC/BN films deposited without substrate bias. Although the layers were very thin, each layer was distinguishable. This was confirmed by the use of TEM imaging and AES measurements. The hardness values of all the multilayer films were lower than those measured for the monolayer DLC and BN films. However, the hardness can be altered with a change in the bilayer thickness. Furthermore, in the case of the films deposited with substrate bias, multilayer DLC/BN films showed an improvement in wear resistance compared to monolayer DLC and BN films. Thus, the deposition of multilayer DLC/BN films can be considered to be beneficial in prolonging the service life of the surface.

Improvement of Thermal Stability and Tribological Performance of Diamond-Like Carbon Composite Thin Films

Diamond-like carbon (DLC) is a metastable amorphous film that exhibits unique properties. However, many limitations exist regarding the use of DLC, for example, its tribological characteristics at high temperature, as well as its limited thermal stability. In this study, silicon/oxygen and silicon/nitrogen co-incorporated diamond-like carbon (Si-O-DLC and Si-N-DLC) films are studied, taking into account the thermal stability and tribological performance of these films compared with pure DLC. All the films were prepared on Si wafers, WC-Co materials, and aluminum foils using a plasma-based ion implantation (PBII) technique using acetylene (C2H2), tetramethylsilane (TMS, Si(CH3)4), oxygen (O2) and nitrogen (N2) as plasma sources. The structure of the films was characterized using Raman spectroscopy. The thermal stability of the films was measured using thermogravimetric and differential thermal analysis (TG-DTA). The friction coefficient of the films was assessed using ball-on-disk friction testing. The results indicate that Si-N-DLC films present better thermal stability due to the presence of Si-O networks in the films. The Si-N-DLC (23 at.%Si, 8 at.%N) film was affected using thermal annealing in an air atmosphere with increasing temperature until 500°C. The film can also resist thermal shock by cycling 10 times between the various temperatures and air atmosphere until 500°C. Further, Si-O-DLC and Si-N-DLC films exhibit excellent tribological performance, especially the Si-N-DLC (23 at.%Si, 8 at.%N) film, which exhibits excellent tribological performance at 500°C in an air atmosphere. It is concluded that Si-O-DLC and Si-N-DLC films improve upon the thermal stability and tribological performance of DLC.

Expansion of Application Range of Component Restricting Pressure Change Caused by Oil Temperature Change

One of the advantages of an oil-hydraulic system is that the system keeps the value of oil pressure when the pressurized oil is enclosed in a container.However,when the pressurized oil is enclosed in a head or a rod end chamber of an actuator by a check valve or a shut-off valve,the value of the oil pressure deceases gradually by the leakage from the check valve or the shut-off valve.Then,it is necessary to employ non-leakage valve which is expensive or to control the pressure by using a valve or a pump control.In pressure control,energy to compensate pressure is required.From the view point of cost reducing or especially energy saving,it seems to be desirable to develop a component which prevents this pressure drop without energy consumption.Authors had developed a component restricting pressure change caused by oil temperature change.This component has simple mechanism and hardly needs energy.In this study,the possibility of the component to prevent pressure drop due to leakage is investigated experimentally.Consequently,it makes clear that the component is effective to prevent pressure drop by leakage and the enclosed pressure decreases only about 3%in 3 min and about 7%in 60 min when the target enclosed pressure is 3.5 MPa.

Heat Resistant Properties of Some Elements-Incorporated Diamond-Like Carbon Films and Their Trial Applications for Micro End Mill Coatings

In this article, the results obtained from a study carried out on the some elements-incorporated diamond-like carbon (DLC) films are reported. All the films were deposited using plasma-based ion implantation (PBII) technique. The deposited films were annealed at 400℃, 650℃ and 900℃ in an air atmosphere for 1 hour. The effects of adding hydrogen, silicon/oxygen and silicon/nitrogen into the DLC film on chemical composition, friction coefficient and corrosion resistance were investigated. The films coated micro end mills performance was also assessed. The results indicate that all the films showed almost constant atomic contents of C, Si, O and N until annealing at 400℃. However, the films were completely destroyed at 650℃ with the increased Si and O contents, while the C content decreased. The incorporation of silicon/oxygen and silicon/nitrogen into the DLC exhibited lower values of friction coefficients than the hydrogenated DLC (DLC and H-DLC) before and after annealing at 400℃, whereas all the films presented the same values of friction coefficients after annealing at 650℃ due to the completely destroy of the films. Furthermore, the incorporation of silicon/nitrogen into the DLC also exhibited better corrosion resistance and unbroken micro end mills performance on their surfaces. Thus, the incorporation of silicon/nitrogen into the DLC film can be considered beneficial in improving the micro end mills performance.

Coupling of plasmonic nanopore pairs: facing dipoles attract each other

Control of the optical properties of nano-plasmonic structures is essential for next-generation optical circuits and high-throughput biosensing platforms.Realization of such nano-optical devices requires optical couplings of various nanostructured elements and field confinement at the nanoscale.In particular,symmetric coupling modes,also referred to as dark modes,have recently received considerable attention because these modes can confine light energy to small spaces.Although the coupling behavior of plasmonic nanoparticles has been relatively well studied,couplings of inverse structures,that is,holes and pores,remain partially unexplored.Even for the most fundamental coupling system of two dipolar holes,comparison of the symmetric and antisymmetric coupling modes has not been performed.Here we present,for the first time,a systematic study of the symmetric and anti-symmetric coupling of nanopore pairs using cathodoluminescence by scanning transmission electron microscopy and electromagnetic simulation.The symmetric coupling mode,approximated as a pair of facing dipoles,is observed at a lower energy than that of the anti-symmetric coupling mode,indicating that the facing dipoles attract each other.The anti-symmetric coupling mode splits into the inner-and outer-edge localized modes as the coupling distance decreases.These coupling behaviors cannot be fully explained as inverses of coupled disks.Symmetric and anti-symmetric coupling modes are also observed in a short-range ordered pore array,where one pore supports multiple local resonance modes,depending on the distance to the neighboring pore.Accessibility to the observed symmetric modes by far field is also discussed,which is important for nanophotonic device applications.