Corrosion inhibition efficiency and adsorption behavior of azomethine compounds at mild steel/hydrochloric acid interface

The adsorption and inhibition effect of azomethine compounds: PhN = NAC (COCH₃) = NC₆H₄Y {Y = OCH₃ (SB₁), CH₃ (SB₂), H (SB₃), Br (SB₄) and Y = Cl (SB₅)} on mild steel in 1 M HCl at 25 °C were studied using gravimetric measurements, cyclic voltammetry, UV–visible Spectrophotométrique and scanning electron microscope (SEM) methods. Inhibition efficiency was found to increase with the increase in azomethine SB₁-SB₅ concentration. The adsorption of each inhibitor on mild steel surface obeys Langmuir adsorption isotherm. The results of cyclic voltammetry showed that the presence of azomethine compound decreases the charge density in the transpassive region. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a (SB₁-SB₅)-Fe complex. SEM and EDX observations confirmed the existence of protective inhibitor film on a metal surface.     

Shear bond strengths of two newly marketed self-adhesive resin cements to different substrates: A light and scanning electron microscopy evaluation

The purpose of this in vitro study was to compare the shear bond strengths (SBSs) of two newly marketed self-adhesive resin cements (RCs) to enamel, dentin, and lithium disilicate (LiSi) glass ceramic block. Forty-eight enamel and 48 dentin substrates were obtained from sound human molars. Additionally, 6 × 7 × 5 -mm- sized 24 specimens were produced from LiSi glass ceramic blocks. The tooth specimens were randomly assigned into four groups (n = 12) according to the surface treatments: (1) G-CEM ONE (GCO), (2) G-CEM ONE Adhesive Enhancing Primer (GCO-AEP) + GCO, (3) RelyX Universal (RXU), and (4) Scotchbond Universal Plus (SUP) + RXU. LiSi specimens were randomly divided into two groups (n = 12): (1) G-MultiPrimer (GMP) + GCO and (2) SUP + RXU. Following the RC applications, all specimens were kept in 100% humidity at 37°C for 24 hr and then submitted for SBS testing in a universal testing machine (1 mm/min). Data were analyzed by Welch's, one-way analysis of variance and two independent samples t tests. The nature of failures was examined under a light microscope, and scanning electron microscopy analyses were also performed for interfaces. GCO and RXU showed similar SBS to enamel (p > .05), and the use of adhesives resulted in improved SBS (p < .05). No difference was detected between GCO-AEP + GCO and SUP + RXU. The GCO-AEP + GCO exhibited the highest SBS to dentin (p < .05), followed by GCO ≥ SUP + RXU > RXU (p < .05). There was no significant difference between SBSs of two RCs to LiSi blocks (p > .05). No cohesive failure was determined for the tested groups by light microscope. The use of adhesives prior to the application of self-adhesive RCs improved their bonding to tooth tissues. GCO demonstrated superior SBS to dentin, whereas both self-adhesive RCs generated similar SBS to enamel and LiSi glass ceramic surfaces.     

How does antiseptic mouthwashes against SARS-COV-2 affect the bond strength of universal adhesive to enamel?

This study compares the effect of different mouthwashes that have been recommended during the Coronavirus disease 2019 (COVID-19) pandemic on shear bond strength (SBS) of universal adhesive to enamel in regards to self-etch (SE) and etch-and-rinse (ER) modes. Flat enamel surfaces were obtained from 100 sound human maxillary central incisors. They were randomly allocated to five groups according to the different mouthwashes (no mouthwash/control [Ctrl], 0.2% chlorhexidine 1.5% hydrogen peroxide [H₂O₂], 0.2% povidone-iodine [PVP-I], Listerine [L]), and adhesive application modes (ER and SE) (n = 10). After the application of a universal adhesive (single bond universal), composite resin (Filtek Z250) was bonded by a cylinder-shaped mold (height: 2 mm, diameter: 2.4 mm). They were subjected to SBS test using a universal testing machine (AGS-X, Shimadzu Corp.) (crosshead speed: 1 mm/min). The resin–enamel interfaces were observed with a scanning electron microscope (SEM). The semiquantitative chemical microanalyses were performed with energy-dispersive spectroscopy (EDS). The data were statistically analyzed by two-way analysis of variance and Bonferroni test (p < .05). In SE mode, Group Ctrl revealed significantly higher SBS than all mouthwash groups (p < .05). In ER mode, Group Ctrl showed significantly higher SBS than H₂O₂ and PVP-I groups (p < .05). ER mode caused significantly higher SBS than SE mode in all mouthwash groups (p < .05). The SEM observations highlighted that Group Ctrl had a regular and intact hybrid layer with resin tag formation while the H₂O₂ and PVP-I groups exhibited a thin hybrid layer in both modes. EDS analysis indicated that in SE mode, all mouthwash groups presented increased O content compared to Group Ctrl. H₂O₂ and PVP-I that were suggested for preprocedural use during the COVID-19 pandemic, reduced the enamel bond strength of the universal adhesive in ER mode.     

Nanoleakage evaluation of resin luting systems to dental enamel and leucite-reinforced ceramic

Purpose: The aim of this study was to evaluate the nanoleakage patterns between dental enamel and reinforced leucite ceramic, bonded with resin luting systems and a flowable composite resin. Materials and Methods: Twelve crowns of bovine incisors were randomly divided into four groups (n = 3) according to the luting procedure: Excite/Variolink II, Clearfil SE Bond/Panavia F, Scotchbond Multi‐Purpose Plus/RelyX ARC, and Single Bond 2/Filtek Z350 Flow. To evaluate the nanoleakage patterns, IPS Empress Esthetic disks (5 mm Ø and 1.2‐mm thick) were bonded to enamel, and, after 24 h, the specimens were immersed in a 50% (w/v) solution of silver nitrate (24 h), fixed, dehydrated, and processed scanning electron microscopy (SEM). Results: None nanoleakage on interface of the groups that Single Bond 2 followed by the flowable composite were used. The highest percentage of nanoleakage was shown by the Excite/Variolink II protocol. Also, in all conditions tested, none silver nitrate uptake was observed between the leucite‐reinforced ceramic and the resin luting cement. Conclusions: The use of a two‐step etch‐and‐rinse adhesive with flowable composite was able to promote an adequate seal of the bond interface at the enamel. Moreover, the conventional dual‐cured resin cements associated with simplified and dual‐cured adhesives tested are also indicated to bond thin ceramics to enamel, since all presented low silver nitrate uptake. Microsc. Res. Tech., 2012. © 2011 Wiley Periodicals, Inc.     

Ultrastructural and physicochemical characterization of pH receptive chlorhexidine-loaded poly-L-glycolic acid-modified orthodontic adhesive

This study aims to evaluate the feasibility of chlorhexidine (CHX)-loaded poly-L-glycolic acid (PLGA) nanoparticles as a modifier of a commercial orthodontic adhesive via the assessment of physicochemical, biological, and mechanical properties at tooth-bracket interface. CHX-loaded PLGA nanoparticles were synthesized using double emulsion-solvent evaporation method and characterized using transmission electron microscopy and Raman analysis. CHX-loaded PLGA nanoparticles in Transbond XT orthodontic adhesive were prepared using two different concentrations of the CHX (25 and 50%) and characterized for degree of conversion (DC), antimicrobial, and cytotoxicity testing. Bonded specimens were tested for shear bond strength (SBS) and adhesive remnant index (ARI) at tooth-bracket interface. The synthesized PLGA nanoparticles averaged between 60 and 80 nm in size. After loading CHX inside PLGA nanoparticles, the morphology of the PLGA nanoparticles was considerably changed. Orthodontic bracket bonded with 25% CHX-loaded PLGA-modified adhesive demonstrated DC scores similar to control group. Both 25 and 50% CHX-loaded PLGA-modified adhesive specimens showed higher antibacterial activity against S. mutans compared to control group. The least mean SBS values were exhibited by 50% CHX-loaded PLGA-modified adhesive samples, while a statistically significant difference was observed in the mean ARI values among all study groups at all-time points (p = .018). This study indicates that the addition of CHX-loaded PLGA nanoparticles in Transbond XT achieved stable bonds with enhanced antimicrobial and mechanical properties.     

Multi-response optimization of machining process parameters for powder mixed electro-discharge machining of H-11 die steel using grey relational analysis and topsis

Electro-discharge machining (EDM) is an enormously used nonconventional process for removing material in die making, aerospace, and automobile industries. It consists of limitations like poor volumetric material removal rate (MRR) and reduced surface quality. Powder mixed EDM (PMEDM) is a new development in EDM to enhance its machining capabilities. The present work investigates the effect of powder concentration (C_p), peak current (I_p), pulse on time (T_on), duty cycle (DC) and gap voltage (V_g) on MRR, tool wear rate (TWR), electrode wear ratio (EWR), and surface roughness (SR) simultaneously for H-11 die steel using SiC powder. Taguchi's L₂₇ orthogonal array has been used to conduct the experiments. Multiobjective optimization using grey relational analysis (GRA) and technique for order of preference by similarity to ideal solution (TOPSIS) has been used to maximize the MRR and minimize the TWR, EWR, and SR and determine the optimal set of process parameters. Analysis of variance (ANOVA) has been performed to understand the significance of each process parameter. Results were verified by conducting confirmatory tests. GRA and TOPSIS exhibit an improvement of 0.1843 and 0.14308 in the preference values, respectively. Microstructure analysis has been done using scanning electron microscope (SEM) for the optimum set of parameters.     

The influence of tissue processing on quantitative histopathology in breast cancer

Objective grading of breast cancer by morphometry has been suggested for improving the precision of the prognostic prediction. However, the tissue components evaluated might be influenced by variations in the processing, reducing the clinical value. In the present study, the impact of the period of fixation, of the acidity of the fixative and of the embedding medium was investigated by allocating tissue samples from 27 surgical breast cancer specimens systematically randomly to different modes of processing. The volume-weighted mean volume of cancer cell nuclei, v?_V(nuc), was estimated using the method of point-sampled intercepts on vertical sections. In addition, estimates of the mean nuclear profile area, ā_H(nuc), the nuclear volume fraction, V_V(nuc), the nuclear profile density, ND, and the mitotic profile frequency, MF, were obtained. The quantitative histopathological estimates were stable with respect to the investigated variables of the tissue processing. No significant differences were found when comparing the estimates obtained in samples from five tumours fixed in formalin at pH 5·0, 6·0, 7·0, 7·4 and 8·0, respectively. Similarly, no significant correlations between the estimates and the period of formalin fixation (24 h, 3 days and 3 months) were found in samples from five other tumours. However, the v?_V(nuc) was 13% larger (2p = 0·004) and the mean ND 17% smaller (2p = 0·04) in hydroxyethyl-methacrylate-embedded samples from 17 tumours as compared to paraffin-embedded samples. Thus, the shrinkage observed in paraffin seems to affect nuclei less than tissue.     

Characterization of nanoscale recording mark on Ge2Sb2Te5 film

We have fabricated nanoscale recording marks on Ge₂Sb₂Te₅ (GST) films with conductive atomic force microscope (AFM). GST films were deposited on glass or polyimide film with thickness of 150–200 nm by the rf–sputtering method. Through current–voltage (I–V) spectroscopy, good cantilevers for fabrication and characterization of nanoscale marks on GST were selected. A fresh and highly conductive tip showed voltage-switching characteristic in the I–V curve, where the threshold voltage was 1.6 V. Nanoscale dot and wire arrays of crystalline phases were successfully obtained by varying sample bias voltage from −10 to 10 V. With highly conductive tips, nanowires having full-width at half-maximum of 20 nm could be fabricated, whereas nanowires could not be fabricated with bias voltage below −2 V. The width of the nanoscale mark was increased by repetition of AFM lithography even with same applied voltage and lithography speed. For a thicker nanowire, the width measured in current-image (C-image) was observed to be 2 times of that measured in topography-image (T-image). This result supports that current sensing provides an image of phase-changed GST area with higher resolution than topography sensing.     

Remineralization effects of self-assembling peptide P11-4 associated with three materials on early enamel carious lesions: An in vitro study

The aim of this study was to assess the remineralization of enamel caries lesions using the self-assembling peptide P₁₁-4 associated with different materials. Artificial early enamel lesions were prepared on 154 primary teeth. The samples were randomly divided into eight groups: (1) control, (2) P₁₁-4, (3) fluoridate toothpaste (FT), (4) P₁₁-4 + FT, (5) casein phosphopeptide–amorphous calcium phosphate (CPP–ACP), (6) P₁₁-4 + CPP–ACP, (7) fluoridate bioactive glass toothpaste (BT), and (8) P₁₁-4 + BT. The surface enamel microhardness (EMH) and energy-dispersive X-ray spectroscopy (EDS) of the teeth were then measured at the baseline, after demineralization, and after 28 days of remineralization. The enamel surfaces were assessed by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The data were analyzed with one-way analysis of variance (ANOVA) (p < .05). EMH after demineralization was significantly lower than the baseline value (p < .001). The interventions led to an enhanced percentage of EMH recovery (%REMH), which was higher in Groups 6 and 7. There was no significant difference between Groups 3 and 4. Groups 1 and 2 had the lowest %REMH. The mean calcium/phosphate weight percentage ratio of P₁₁-4 was significantly lower than the others (p < .001). The FESEM and AFM images revealed mineral deposition on the eroded enamel and reductions in surface roughness in Groups 5 and 7.     

Effect of laser preparation on adhesion of a self‐adhesive flowable composite resin to primary teeth

The aim of the study was to evaluate the adhesion of a self‐adhering flowable composite resin to primary tooth enamel and dentin after silicon carbide paper (SiC) and laser pretreatment. Adhesive properties were evaluated as shear bond strength (SBS) and scanning electron microscopic (SEM) characteristics. A total 120 primary canine teeth were randomly divided into two groups to study enamel and dentin. Each group was divided into 6 subgroups (n = 10) according to type of surface preparation (SiC or Er:YAG laser) of enamel or dentin. Three methods were used to build cylinders of restoration on tooth surface: OptiBond All‐In‐One + Premise Flowable composite, OptiBond All‐In‐One + Vertise Flow and Vertise flow. After restoration, samples were tested for SBS and failure mode. Twenty eight samples were examined by SEM. The results of the study showed SBS of Vertise Flow was lower than others in enamel and dentin samples pretreated with SiC and in dentin samples pretreated with laser (P < 0.001). Compared to SiC pretreatment, laser pretreatment led to a significantly higher SBS with Vertise Flow on enamel (P < 0.001). Vertise Flow associated with the adhesive led to a higher SBS in enamel and dentin compared to Vertise Flow alone. Adhesive and mixed failure modes were observed more frequently in Vertise Flow groups. SEM images showed that Vertise Flow led to more irregularities on enamel and more open dentinal tubules after laser ablation compared SiC pretreatment. Microsc. Res. Tech. 79:334–341, 2016. © 2016 Wiley Periodicals, Inc.     

Influence of UV irradiation in low frictional performance of CNx coatings

The influence of ultraviolet (UV) irradiation on low frictional performance of CN_x coatings with 100 nm thickness having nitrogen contents of 9%, 14% and 19% deposited on Si(100) substrate by ion beam mixing was investigated in N₂ atmosphere environment. Three UV lights of 254, 312 and 365 nm were used to irradiate the surface of CN_x / Si(100) for 60 min. The changes of N / C ratio and atomic binding energy in the coating were analysed using Auger electron spectroscopy and X‐ray photoelectron spectroscopy, respectively. The friction coefficient of Si₃N₄ ball sliding against CN_x was measured by a pin‐on‐disc tribometer, and wear tracks were analysed by the transmission electron microscope image. The results showed that UV irradiation on CN_x coating can decrease the critical frictional cycles for low friction coefficient and that the mechanism is due to the formation of graphite‐like structure in the topmost CN_x coating. Copyright © 2012 John Wiley & Sons, Ltd.     

On the Pressure Dependence of Shear Strengths in Sliding, Boundary-Layer Friction

Density functional theory, as implemented in a full-potential linearized augmented plane wave method, flair, is used to calculated the pressure-dependent shear strength S of KCl on a Fe(100) substrate and the results are compared to the experimental dependence given by S = S₀ + aP S = S_{0} + \alpha P , where P is the contact pressure and S ₀ = 65 ± 5 MPa and α = 0.14 ± 0.02. Calculations were performed for a KCl bilayer enclosed between two Fe(100) slabs, where the energy was found to vary harmonically as a function of the separation between the outermost layers. Thus, a simple analytical model was developed for the pressure-dependent shear strength of the film, which includes both linear and quadratic pressure dependence. However, the coefficient of the quadratic term was found to be much smaller than the linear term, leading to the linear shear-strength pressure dependence found experimentally. The calculated values of S ₀ 〈10〉 = 64 ± 9 and S ₀ 〈11〉 = 69 ± 8 MPa are in excellent agreement with experiment, while α 〈10〉 and α 〈11〉 equal 0.05 ± 0.01, somewhat lower than, but within the same range as the experimental values.     

High-temperature low-friction properties of vanadium-alloyed AlCrN coatings

V-alloyed AlCrN hard coatings were deposited by reactive arc-evaporation in a commercial Balzers RCS coating system. The Al/(Al + Cr + V) atomic ratio in the target was kept constant at 0.7, while the Cr was stepwise substituted by V. Alloying V into the AlCrN coatings led to the partial transformation to a hexagonal phase of the otherwise metastable cubic lattice, whereas the hexagonal phase fraction was observed to increase with the V concentration in the coating. This results in a reduction of hardness (from 28 to 19 GPa) and biaxial coating stress (from − 1700 to − 900 MPa). The performed tribological tests at high temperature revealed a significantly lower coefficient of friction down to a value of 0.2 for Al_0.67Cr_0.05V_0.28N at 700 °C. This behaviour is due to the formation and melting of the Magnéli phase oxide V₂O₅ forming a low-friction layer on the surface as indicated by Raman spectroscopy and scanning electron microscopy.     

Characterization of thermoelectric generators by measuring the load-dependence behavior

Solid-state thermoelectric generators (TEGs) based on the Seebeck effect to convert temperature gradients, ΔT [K], into electrical energy are being used in an increased number of stand-alone microsystems applications. These generators are composed by at least one pair of p- and n-type thermoelectric elements with high figures-of-merit, ZT, to perform such a conversion. The exact behavior knowledge of generators is mandatory in order to decide the most suitable for the target application. The focus of this paper is to present a methodology to characterize thermoelectric generators, by measuring their behavior for different types of loads. The measurements were done with the help of commercial thermoelectric generators (thermoelectric modules TEC1-12707) and a measurement setup composed by a controlled hot-plate, a controlled cooling fan (above an heat dissipator), a set of two thermistors for measuring the temperature, a personal computer with the data acquisition board model NI USB-6009 and the LabView software from National Instruments for acquiring the measures and for controlling both the hot-plate and the cooling fan. The thermoelectric modules TEC1-12707 was selected due to its compact size (e.g., 40 mm × 40 mm) and because it can withstand temperatures up to 450 K without degrading the quality of measurements. A SPICE model for thermoelectric modules TEC1-12707 was also obtained: an open-circuit voltage of V_open = 53.17 × ΔT [mV] and an internal resistance of R₀ = 3.88 Ω with a tolerance of ΔR_int = 0.13 Ω such that R_int = R₀ ± ΔR_int = 3.88 ± 0.13 Ω. The measurements done under the maximum output power delivery condition (for the maximum temperature gradient of ΔT = 51 °C) resulted in the maximum output power of P_out = 500 mW, as well as in the output current and voltage of I_out = 357 mA and V_out = 1.40 V, respectively. The load resistance of 3.92 Ω (V_out/I_out) is also in accordance with the measurements because it is located in the range [μ − σ, μ + σ] Ω, where μ = R₀ = 3.88 Ω and σ = ΔR_int = 0.13 Ω. An Agilent multimeter model 34410A with 6½ digits was used for measuring the voltages at the TEG’s output and the respective currents.     

Cleaning capacity of octenidine as root canal irrigant: A scanning electron microscopy study

The aim of this study was to assess the cleaning capacity of the octenidine hydrochloride (OCT) used as root canal irrigant by scanning electron microscopy (SEM) analysis. Sixty human unirradicular extracted teeth were randomly distributed in 6 groups (n = 10) according to irrigant solutions which were used during root canal preparation: G1, 0.1% OCT; G2, 2% chlorhexidine (CHX); G3, 2.5% sodium hypochlorite (NaOCl); G4, OCT + 17% ethylenediaminetetraacetic acid (EDTA); G5, 2.5% NaOCl + 17% EDTA and G6, distilled water. All specimens were instrumented with ProTaper system up to F4. Teeth were sectioned and prepared for SEM. The smear layer was evaluated using a 5‐score system and the data were analyzed by Kruskal–Wallis and Dunn (α = 0.05). In all root canal thirds there was no significant difference between OCT, CHX, NaOCl, and water groups (p > .05), and these groups showed higher smear layer values than NaOCl + EDTA and OCT + EDTA groups (p < .05). There was no significant difference between NaOCl + EDTA and OCT + EDTA groups (p > .05). It was concluded that OCT used as a single root canal irrigant presented poor cleaning capacity and could be used in association with a final irrigation with EDTA to obtain smear layer removal.     

Comparison of total‐etch,self‐etch,and selective etching techniques on class V composite restorations prepared by Er:YAG laser and bur: a scanning electron microscopy study

The purpose of this study was to compare total‐etch, self‐etch, and selective etching techniques on the marginal microleakage of Class V composite restorations prepared by Er:YAG laser and bur. Class V cavities prepared on both buccal and lingual surfaces of 30 premolars by Er:YAG laser or bur and divided into six groups. The occlusal margins were in enamel, and the cervical margins were in cementum. Group‐1: bur preparation(bp)+Adper Single Bond 2 (ASB)+Filtek Z550 (FZ); Group‐2: laser preparation(lp)+(ASB)+(FZ); Group‐3: bp + Clearfil S3 Bond Plus (CSBP)+(FZ); Group‐4: lp+(CSBP) (FZ); Group‐5: bp + acid etching+(CSBP)+(FZ); Group‐6: lp + acid etching+(CSBP)+(FZ). All teeth were stored in distilled water at 37°C for 24 hr, and then thermocycled 1000 times (5–55°C). Five teeth from each group were chosen for the microleakage investigation, and two teeth for the scanning electron microscope evaluation. Teeth which were prepared for the microleakage test were immersed in .5% methylene blue dye for 24 hr. After immersion, the teeth were sectioned and observed under a stereomicroscope for dye penetration. Data were analyzed using Kruskal–Wallis and Mann–Whitney U tests (p < .05). More microleakage was observed in the cervical regions compared to the occlusal regions in Groups 3, 5, and 6, respectively (p < .05). There is no statistically significant difference in Groups 1, 2, and 4, in terms of cervical regions versus occlusal regions (p > .05). No significant differences were observed among any groups in terms of occlusal and cervical surfaces, separately (p > .05). Different etching techniques did not influence microleakage of Class V restorations prepared by Er:YAG laser and bur.     

Selecting distribution centre location using an improved fuzzy MCDM approach

A distribution centre (DC) is usually supplied by manufacturing factories and in turn it supplies the consumers. To reduce transportation costs and enhance operation efficiency, selecting a suitable DC location has become a very important issue for both manufacturing and distribution industries. Recently, Chen [1] proposed a fuzzy MCDM (multiple criteria decision-making) approach to selecting the location of a distribution centre. Despite its merits, two limitations were found in his works, i.e. follows: (1) the final fuzzy evaluation value P _i was treated as a triangular fuzzy number. This is not correct because it may not produce a triangular shape and (2) the difference of two final fuzzy evaluation values, i.e. P _i –P _j , was regarded as a triangular fuzzy number. This is also incorrect. Obviously, P _i –P _j may not produce triangular shape because P _i and P _j may not be triangular fuzzy numbers. To resolve the above limitations and enhance the applicability of the fuzzy MCDM to the DC location selection problem, an improved fuzzy MCDM approach is proposed. In this work, the membership functions of P _i and P _i –P _j are developed to construct an improved fuzzy preference relation, which is further employed with the Chen ranking procedure to complete the proposed method. Finally, a numerical example demonstrates the feasibility of the proposed method.     

Effect of Oxygen on the Self-formation of Carbonaceous Tribo-layer with Carbon Nitride Coatings under a Nitrogen Atmosphere

The ball-on-disk friction and wear tests of CN _X coatings (CN _X /CN _X ) were conducted under a nitrogen atmosphere with controlled relative humidity (RH) (3.4–40.0%RH) and oxygen concentration (100–21 × 10⁴ ppm) in this study. We found that the specific wear rate of CN _X coating on ball (W _b), which could give stable and low friction coefficient (<0.05), was below 3.0 × 10^?8 mm³/Nm. Average friction coefficients (µ _a) and W _b of CN _X /CN _X increased (µ _a: 0.02–0.33, W _b: 1.6 × 10^?8–2.4 × 10^?7 mm³/Nm) with increasing oxygen concentration (230–211,000 ppm) as well as RH (4.7–21.1%RH) under a nitrogen atmosphere. However, the W _b remained low value below 2.3 × 10^?8 mm³/Nm regardless of oxygen concentration (100–207,000 ppm) of a nitrogen atmosphere (3.4–3.9%RH) when CN _X -coated balls were slid against a hydrogenated CN _X (CN _X :H) coatings (CN _X /CN _X :H). Besides, the CN _X /CN _X :H achieved low and stable friction coefficient below 0.05 under a nitrogen atmosphere (10,000 ppmO₂) regardless of increasing RH up to 20%RH. Raman analysis indicated that the structure of carbon on the top surface of CN _X coating was changed from as-deposited CN _X coating in the case of low friction coefficient (<0.05). Furthermore, TOF-SIMS analysis provided the evidence that the carbon derived from CN _X -coated disk was considered to diffuse into the ball surface, and it mixed with the carbon derived from CN _X -coated ball on the wear scar, which formed the chemically bonded carbon tribo-layer. Low friction coefficient (<0.05) with CN _X coatings under a nitrogen atmosphere was achieved due to self-formation of the carbon tribo-layer.