Nanowear Tests Research Articles

Tribological and mechanical behavior of nanostructured Al/Ti multilayers

Al/Ti nanostructured metallic multilayers (NMMs) with individual layer thicknesses of 2.5 and 30nm were sputter-deposited on Si substrate. The mechanical and tribological properties of the Al/Ti NMMs were studied by nanoidentation and nanowear tests. Microstructures of the NMMs were characterized using X-ray diffraction, scanning electron microscopy, electron backscattered orientation mapping, and transmission electron microscopy before and after the tests. Decreasing the layer thickness from 30 to 2.5nm led to an increase of hardness from 3.13 to 4.94GPa. For both NMMs, the wear rate increased with applied load and decreased with hardness. Nanoindentation tests on the worn surface revealed significant work hardening of the subsurface material. The deformation mechanisms of NMMs were found to strongly depend on layer thickness and interface structure.

Plasma Enhanced-Chemical Vapour Deposition of Scuff-Resistant Hydrogenated Amorphous Carbon Coatings on C100 Steel

Hydrogenated amorphous carbon coatings, deposited by low pressure plasma to minimize the wear of C100 steel components, were optimized and characterized. In order to ensure good adhesion of the films to the steel surface, a thin Ti interlayer was deposited, by magnetron sputtering, before the plasma deposition. The chemical characterization of the deposits was performed by means of RAMAN, XPS, RBS and ERDA analysis, while nanoindentation, nanoscratch and nanowear tests allowed to estimating the tribomechanical properties of the deposits, with the aim of evaluating their scuff-resistance. It was found that the optimized plasma deposited hydrogenated amorphous carbon coatings were well adherent to C100 steel and increased more than 70% its surface hardness.

Effects of grain size and orientation on mechanical and tribological characterizations of nanocrystalline nickel films

The mechanical and tribological properties of nanocrystalline nickel films affected by the grain size and preferred orientation are studied. Nickel films were produced by the supercritical electroplating process. The preferred orientations and the grain sizes of nickel films were determined by substrates (brass or phosphonic copper), reaction time and chamber pressure. The (111), (111)+(200) and (200) preferred orientation of nickel films were made. The XRD, SEM, AFM, and TEM tests were applied to confirm the preferred orientation and the grain size of a nickel film. The nanoindentation, nano-scratch and nano-wear test were used to obtain the informations regarding the hardness, friction coefficient and wear depth, respectively. The mechanical and tribological properties of nickel films are improved by reducing the grain size. Nevertheless, under smaller grain size conditions (i.e. <30nm), due to the reverse Hall–Petch relation induced by internal stress, the improvements might be terminated or even decay. In the meantime, one can found that (111) nickel film possesses better mechanical and tribological properties. It is because that, in (111) crystal plane, the nickel atoms accumulate in the most compact form, and a stronger binding energy exists between the atoms. Therefore, if the grain size is in the nanoscale regime, the mechanical and tribological properties are under the influence of the anisotropy of a nickel film.

Is 2 nm DLC coating enough to resist the nanowear of silicon

The ultrathin DLC coatings with thickness of 2nm and 5nm were deposited onto Si(100) substrate by the filtered cathodic arc technique. The nanowear tests were performed on DLC coatings and Si(100) substrate by diamond tip and SiO2 microspheric tips. The results indicated that the coatings could support an indentation with a peak contact pressure of 7GPa. During scratch tests, the critical load corresponding to the generation of grooves on silicon substrate could be raised by 75%/125% after the deposition of DLC coating of 2nm/5nm in thickness. When the nanowear tests were conducted by a diamond tip, DLC coatings could effectively resist the mechanical wear and prevent the formation of hillock on silicon substrate. Moreover, since two DLC coatings present a close coverage on silicon substrate, they can largely resist the tribochemical wear of silicon substrate by SiO2 tip in humid air. Under a contact pressure of 1.3GPa, the wear depth on 2nm/5nm DLC coating was only 0.42nm/0.28nm, which was less than 5% of that on silicon substrate. Finally, either in humid air or in vacuum, 2nm DLC coating presented the excellent durability to protect the silicon substrate from wear damage. Therefore, although thicker DLC coating to some extent reveals better wear resistance, 2nm DLC coating is enough to protect its substrate against nanowear.

Wettability and Nanotribological Response of Silicon Surfaces Functionalized by Ion Implantation

Aiming to improve the nanotribological response of Si-based materials we implanted silicon wafers with different fluences of iron ions (up to 2x1017 cm-2). Implantation was followed by annealing treatments at temperatures from 550°C to 1000°C. The implanted surfaces were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and wettability tests. Then, samples were submitted to AFM-based nanowear tests. We observe an increase of both hidrophobicity and and wear resistance of the implanted silicon, indicating that ion implantation of Si can be a route to be deeper explored in what concerns tribomechanical improvement of Si.

Improvement of the mechanical properties of single-walled carbon nanotube networks by carbon plasma coatings

Carbon vacuum arc was used to deposit 5–25nm thick carbon coatings on single-walled carbon nanotube (SWCNT) networks. The SWCNT bundles thus embedded in conformal coatings maintained their optical transparency and electrical conductivity. Sheet resistances of the networks were measured during the vacuum arc deposition, revealing initially a 100-fold increase, followed by significant recovery after exposing the samples to an ambient atmosphere. Nanoindentation measurements revealed improved elasticity of the network after applying the carbon coating. Pristine SWCNT networks were easily deformed permanently, but a 20nm carbon coating strengthened the nanostructure, resulting in a fully elastic recovery from a 20μN load applied with a Berkovich tip. In nano-wear tests on selected areas, the coated SWCNT maintained its networking integrity after two passes raster scan at loads up to 25μN. On the other hand, the pristine networks were badly damaged under a 10μN scan load and completely displaced under 25μN. Raman and electron energy loss spectroscopies indicated the carbon coating on bundles to be mainly sp2 bonded. Finite element modeling suggests that the low content of sp3 bonds may be due to heating by the intense ion flux during the plasma pulse.

Effect of feed gas composition effects on the nanotribological properties of diamond-like carbon films

A series of experimental nanoindentation, nanowear and nanoscratch tests was conducted to investigate the relationship between the nanotribological characteristics of diamond-like carbon (DLC) and feed gas composition used for the deposition. The DLC films were deposited on silicon substrates in radio-frequency plasma enhanced chemical vapor deposition system with a mixture of hydrogen and methane gases. Raman spectroscopy results show that the integrated intensity ratios (ID/IG) of each profile correlate with sp2/sp3 ratios. The result also indicates that the hydrogen content in the source gas has a significant influence upon the sp2/sp3 ratio and hydrogen-to-carbon ratio in DLC films. It is demonstrated that the sp2/sp3 ratio decreases with increasing hydrogen content in the DLC film. Our result also reveals that a significant relationship between the hydrogen content and the nanotribological characterizations of the DLC films, namely lower hydrogen-to-carbon ratio leads to higher hardness, elastic modulus, friction coefficient, and lower wear depth. The surface reinforcement can be attributed to the fact that variation of surface energy arises from the different carbon hybridized states (sp2/sp3 ratio), which improve the surface properties via the hydrogen content in the source gas and associated nanotribological characteristics.

Nanoscratch and nanowear testing of TiN coatings on M42 steel

Constant load, progressive load and multipass nanoscratch (nanowear) tests were carried out on 500 and 1500 nm TiN coatings on M42 steel chosen as model systems. The influences of film thickness, coating roughness, scratch direction relative to the grinding grooves on the critical load in the progressive load test and number of cycles to failure in the wear test have been determined. Progress towards the development of a suitable methodology for determining the scratch hardness from nanoscratch tests is discussed.

Nanowear in a nanocomposite reinforced polymer

a b s t r a c t We investigated the reinforcement of blends made from poly(ethyl methacrylate) (PEMA) and PEMA- grafted nanoparticles at a nanometer length scale. The reinforcement was probed by nanowear experiments based on scanning force microscopy (SFM). In addition to imaging, the SFM is applied to wear the surface of samples at the length scale of nanoparticles. Blends with different miscibility of nanoparticles were prepared by varying the molecular weights of polymer grafted from the nanoparti- cles (N) and polymer forming the matrix (P). We were able to associate a critical force for the onset of nanowear by analyzing the nanowear patterns resulting from different normal loads during the nanowear experiment. The definition of this critical force allows quantitative comparison of nanoparticle-polymer systems of different composition. Nanowear tests indicated that only mixtures where N/P > 1 reinforced the composite material compared to the pure homopolymer. Under these conditions the grafted polymers were swollen and the nanoparticles acted as additional anchor sites. As reference experiments we used a blend made from PEMA homopolymer and unmodified particles. Non-grafted nanoparticles clearly did not account for any reinforcement.

Nano-wear, nano-hardness and corrosion-resistance of electroplated nickel surfaces after co-implantation of Cr+ and N2+ ions

In this work, a successful sequential co-implantation treatment of Cr+ and N2+ ions into electrodeposited nickel plates is presented. The goal of this treatment is the simultaneous enhancement of the wear resistance, mechanical stability and corrosion-protection properties of the Ni surfaces. The ion-implanted surfaces have been characterized by glow-discharge optical-emission spectroscopy, X-ray diffraction, nano-hardness, roughness, nano-wear and potentio-dynamic corrosion tests. It has been observed that the implantation of Cr+ or N2+ alone is not sufficient to achieve simultaneously the enhancement of both the wear-resistance and the corrosion-protection properties. Conversely, the sequential implantation of Cr+ and N2+ at 140keV and fluencies of 3×1017 and 1.5×1017ions/cm2 respectively, permits the formation of a functional surface capable of reducing both the corrosion rate and the wear rates, with respect to those exhibited by the un-implanted Ni surfaces.This treatment can be used to protect the surfaces of micro-embossing/stamping dies based on electroformed Nickel, as an alternative to other coating strategies. Furthermore, the ion implantation assures the non-modification of the net-shape and surface finish of these types of dies, which is of crucial importance when they are used for high-precision micro-texturing/imprinting applications.

Nanowear of Hafnium Diboride Thin Films

Chemical Vapor Deposition-grown HfB2 films were subjected to nanowear testing at normal loads of 50–500 μN. The material response was investigated by measuring residual wear depths and wear scar roughness and by calculating wear rates and specific energies. Films annealed for 1 h at 800°C showed significant reduction in wear rate and required a higher critical energy for wear, compared to as-deposited HfB2 films. Analysis of roughness of the worn scars revealed that plowing effect dominates at higher loads (200–500 μN), whereas at lower loads, asperity flattening dominates. The excellent response of annealed HfB2 films to nanotribological testing demonstrates the potential of these films for applications requiring high wear resistance at the nanoscale.

Lateral Force Calibration Method Used for Calibration of Atomic Force Microscope

Modern heterogeneous micro- and nanostructures usually integrate modules fabricated using various materials and technologies. Moreover, it has to be emphasized that the macro and micro nanoscale material parameters are not the same. For this reason it has become crucial to identify the nanomechanical properties of the materials commonly used in micro- and nanostructure technology. One of such tests is a nanowear test performed using the atomic force microscope (AFM). However, to obtain quantitative measurement results a precision calibration step is necessary. In this paper a novel approach to calibration of lateral force acting on the tip of an AFM cantilever is discussed. Presented method is based on application of known lateral force directly on the tip using a special test structure. Such an approach allows for measurements of nanowear parameters (force, displacement) with the uncertainty better than ±3%. The calibration structure designed specifically for this calibration method is also presented.

New approach to estimate nanowear test results through nanoindentation test

High development of MEMS/NEMS structures has caused the need to know material properties in micro- and nano-scale. Unfortunately well-known macro-scale material properties could not be used in micro- and nano-scale. Therefore, there was a need to perform experiments in micro- and nano-scale. For that purpose, the most often nanoindentation and nanowear tests were used. The first one was time consuming, complicated and it gave tribological parameters of the material under investigation. The second one was a simple, quick test that gave information about mechanical properties of the material. In order to shorten time required for estimation of material properties authors have invented a simulation program that could estimate nanowear test results through nanoindentation test results. In this program both tests were simulated in such a way that elastic and plastic material deformations were taken into account. A set of nanoindentation test were used for setting simulation parameters as well as for verification of results achieved through simulation of nanoindentation process. A set of nanowear tests were used for verification of simulation test results. In addition, a comparison of mentioned above tests from the energy approach was made.

Nanometre scale mechanical properties of extremely thin diamond-like carbon films

Extremely thin diamond-like carbon (DLC) films are deposited by the filtered cathodic vacuum arc (FCVA) and plasma chemical vapour deposition (p-CVD) methods. The target thicknesses of the extremely thin protective DLC films deposited on a Si (100) surface by FCVA and p-CVD are 0·1, 0·4, 0·8, 1·0, 2·0, 5·0 and 100·0 nm. Nanoindentation hardness and nanowear resistance are evaluated by atomic force microscopy (AFM). The nanoindentation hardnesses of 100 nm thick DLC films deposited by FCVA and p-CVD are 57 and 25 GPa respectively. The nanowear test by AFM clarifies the mechanical properties of extremely thin DLC films. The wear depths of 1 and 2 nm thick FCVA-DLC films are extremely shallow. The wear depths of the 1·0 and 2·0 nm thick p-CVD-DLC films exceed the film thicknesses after five sliding cycles. These results reveal differences in the wear resistance of extremely thin DLC films and the superior mechanical properties of FCVA-DLC thin films.

Normal Force Calibration Method Used for Calibration οf Atomic Force Microscope

Modern heterogeneous microand nanostructures usually integrate modules fabricated using various materials and technologies. Moreover, it has to be emphasized that the macro and micro nanoscale material parameters are not the same. For this reason it has become crucial to identify the nanomechanical properties of the materials commonly used in microand nanostructure technology. One of such tests is a nanowear test performed using the atomic force microscope (AFM). However, to obtain quantitative measurement results a precision calibration step is necessary. In this paper a novel approach to calibration of lateral force acting on the tip of an AFM cantilever is discussed. Presented method is based on application of known lateral force directly on the tip using a special test structure. Such an approach allows for measurements of nanowear parameters (force, displacement) with the uncertainty better than ±3%. The calibration structure designed specifically for this calibration method is also

Nanotribological characterization of tooth enamel rod affected by surface treatment

Tooth enamel is a hybrid organic–inorganic bionanocomposite comprised predominantly of enamel rods. Understanding the effects of anti-caries treatment on the biomechanical properties of these rods is essential in developing effective caries prevention strategies. Calcium fluoride-like deposits play an important role in caries prevention and their nanotribological properties have a direct effect upon their long-term effectiveness. Accordingly, this study utilizes a variety of techniques, namely nanoindentation, nanoscratch tests, nanowear tests and atomic force microscopy (AFM), to characterize the mechanical and tribological properties of single enamel rods before and after topical fluoride application. The results show that the CaF2-like deposits formed on the enamel surface following fluoride application increase the coefficient of friction of the enamel rods, but decrease their critical load and nanohardness. As a result, the nanowear depth of the treated enamel surface is around six times higher than that of the native enamel surface under an applied load of 300μN. Following the removal of the surface deposits, however, the modulus of elasticity and wear depth of the underlying enamel surface are found to be similar to those of the original enamel surface. However, a notable increase in the surface roughness is observed.

Plasma immersion ion implantation induced improvements of mechanical properties, wear resistance, and adhesion of diamond-like carbon films deposited on tool steel

Nitrogen-rich layers are formed on the surface of JIS-SKH51 tool steel substrates using the plasma immersion ion implantation (PIII) technique. An unbalanced magnetron sputtering (UBMS) system is then used to coat the steel substrates with diamond-like carbon (DLC) films of various thicknesses. The adhesive strength and wear resistance of the DLC films are then examined by performing nanoscratch and nanowear tests. Finally, the microstructures of the DLC films are analyzed using TEM and Raman spectroscopy. The nanoindentation test results show that the PIII treatment yields an effective improvement in both the hardness and the Young's modulus of the SKH51 substrates. Moreover, cross-sectional observations show that the implantation depth and microstructure of the nitrogen-rich surface layer are dependent on the nitrogen/hydrogen flow ratio used in the PIII process. The nanoscratch test results show that the PIII treatment improves the adhesion of the DLC film to the steel substrate. Furthermore, the Raman spectroscopy results indicate that the use of hydrogen in the PIII process limits the increase in the I(D)/ I(G) ratio by increasing the DLC film thickness. Finally, the nanowear test results show that the deposition of a DLC coating with a sufficient thickness yields a significant improvement in the wear resistance of the steel substrate.

極薄ダイヤモンドライクカーボン（ＤＬＣ）膜のナノメータスケールの力学特性評価

Nanometer-scale mechanical properties of extremely thin DLC films deposited using filtered cathodic vacuum arc (FCVA) and electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) methods were evaluated. Auger electron spectroscopy (AES) revealed these DLC films' thickness and composition. Results showed that the obtained DLC films' thickness nearly corresponds to the set thickness. Nanoindentation hardness and nanowear resistance of the DLC films were investigated using atomic force microscopy (AFM). The nanoindentation hardness of 100-nm-thick DLC films deposited using FCVA and ECR-CVD were 57 GPa and 25 GPa, respectively, as evaluated at 40 μN load. The difference of nanoindentation curves of 5- and 2-nm-thick DLC films deposited using FCVA and ECR-CVD methods is only slightly detectable. It is difficult to evaluate the ultrathin DLC films' hardness using a nanoindentation test of several nanometers' thickness. In contrast, mechanical properties of the extremely thin DLC films can be clarified using nanowear testing with AFM. Wear depths of 100-, 5-, 2-nm-thick FCVA-DLC films are all less than 1 nm: extremely shallow. Especially, the wear depth of 100-nm-thick FCVA-DLC film is nearly 0.1 nm, even at 30 μN load. However, the wear depths of 100-, 5-, 2-nm-thick ECR-CVD-DLC films are greater than those of FCVA-DLC films. These results underscore the excellent wear resistance of extremely thin FCVA-DLC films.

紫外線照射処理および熱処理した磁気ディスク潤滑膜の機械特性の評価

Using atomic force microscopy (AFM), nanoindentation, nanowear, and viscoelastic testing were performed to elucidate nanomechanical properties of lubricant-coated magnetic disks. The surface deformation resistance of an ultraviolet (UV)-irradiated disk is superior to those of heat-treated or untreated disks. Evaluation of viscoelastic change using nanowear tests revealed that, for the UV-irradiated and untreated magnetic disks, tanδ does not decrease with friction. However, for the heat-treated disk, tanδ decreases with sliding. This result demonstrates the resupply capability of the UV-irradiated and untreated lubricant-coated disks during sliding. The lubricant-coated magnetic disks’ friction properties are evaluated using the ball-on disk friction test. The UV-irradiated magnetic disk exhibits stable friction coefficients, and less friction damage than the other. These superior properties of the UV-irradiated magnetic disk can be understood in terms of nanomechanical properties evaluated using AFM. The UV-irradiated disk has suitable bonding strength between the lubricant and DLC, in addition to the resupply capability of the free lubricant.

P-MNS-01 EVALUATION OF NANOMETER SCALE MECHANICAL PROPERTIES OF EXTREMELY THIN DIAMOND-LIKE CARBON (DLC) FILMS(Micro/Nanosystem Science and Technology,Technical Program of Poster Session)

Nanometer scale mechanical properties of extremely thin DLC films deposited by filtered cathodic vacuum arc (FCVA) and electron cyclotron resonance chemical vapor deposition (ECR-CVD) methods were evaluated. DLC films, whose target thicknesses are 100nm, 5nm, and 2nm were, deposited on Si (100) substrates by FCVA and ECR-CVD method. Nanoindentation hardness and nanowear resistance of these DLC films are investigated by AFM (Atomic force microscopy). Nanoindentation hardness of 100-nm-thick DLC films deposited by FCVA and ECR-CVD is 57GPa and 25GPa, respectively. The nanowear resistance of 5nm- or 2nm-thick DLC films can be evaluated by AFM at proper load conditions. Then nanowear test reveal the excellent wear resistance of the FCVA-DLC films.