Evaluation Of Nanomechanical Properties Research Articles

Evaluation of nano mechanical properties and corrosion behavior of diffusion welded CoCrNi medium-entropy alloy (MEA) and SUS 304 stainless steel joints

The study mainly focused on examining nanomechanical properties and corrosion behavior of the weld interface formed by diffusion welding of CoCrNi MEA and SUS 304 stainless steel. Three different bonding temperatures (i.e. 950 °C, 1000 °C, and 1050 °C) were utilized in producing diffusion welded joints. The influence of bonding temperatures on nanomechanical properties of the weld interface was characterized through Nanoindentation tests under various loads (i.e. 20 mN to 100 mN). Additionally, electrochemical properties of the weld interface were also examined using a 0.5 M HCl solution. Results clinched that with the increase of bonding temperature significant suppression in carbide formation occurred along with the weld interface. This instigated a reduction in nano hardness and elastic moduli which resulted in maximum elastic recovery along with the weld interface. The indentation size effect was also evident below 40 mN load after which nano hardness became stable while elastic moduli remained impervious to the change of indentation load. Furthermore, based upon electrochemical properties (i.e. Icorr, Ep, and Rp) samples welded at 1000 °C bonding temperature offered excellent corrosion resistance under 0.5M HCl environment.

Activation of apoptosis and G0/G1 cell cycle arrest along with inhibition of melanogenesis by humic acid and fulvic acid: BAX/BCL-2 and Tyr genes expression and evaluation of nanomechanical properties in A375 human melanoma cell line.

Objective(s):Humic acid (HA) and Fulvic acid (FA) are major members of humic substances, which are extracted from organic sources including soil and peat. The pro-apoptotic and anti-melanogenic effects of HA and FA at the cellular and molecular levels in the A375 human melanoma cell line were examined in this study. Materials and Methods:The cytotoxicity effect of HA and FA were evaluated by cell viability assay. Apoptosis and cell cycle were investigated by flow cytometry. Real-time PCR was carried out to measure the expression of BAX, BCL-2, and Tyr genes. Moreover, the changes in nanomechanical properties were determined through atomic force microscopy (AFM). Results:It was found that HA and FA decrease cell viability with an IC50 value of 50 µg/ml (dose-dependent) for 14 hr, arrested cells in the G0/G1 phase, and increased the sub-G1 phase (induce apoptosis). Based on the AFM analysis, Young’s modulus and adhesion force values were increased, also ultrastructural characteristics of cells were changed. Results of Real-time PCR revealed that HA and FA lead to a decrease in the expressions of BCL-2 and Tyr genes, and increase the BAX gene expression.Conclusion:These results exhibited that HA and FA possess pro-apoptotic effects through increasing the BAX/ BCL-2 expression in A375 cells. These molecular reports were confirmed by cellular nanomechanical assessments using AFM and flow cytometry. In addition, HA and FA inhibited melanogenesis by decreasing the expression of the Tyr gene. It is worthwhile to note that, HA and FA can be regarded to design new anti-cancer and anti-melanogenesis products.

Evaluation of Nanomechanical Properties, Surface Roughness, and Color Stability of Esthetic Nickel-Titanium Orthodontic Archwires.

Objectives:The objective of the study is to evaluate the surface roughness, nanomechancial properties the color stability of three brands of coated (rhodium, epoxy, and Teflon) nickel-titanium (NiTi) esthetic archwires.Materials and Methods:Three brands of coated (rhodium, epoxy, and Teflon) esthetic NiTi archwires and three brands of uncoated (NiTi) archwires from the same manufactures were evaluated for the surface roughness, nanomechanical properties, and color stability. The specimens with 20 mm length (n = 5) were cut from the straight buccal segments of the coated and uncoated archwires. The specimens with 20 mm length (n = 10) were subjected to color measurement after immersion in a coffee staining solution. The color measurement was evaluated after 7, 14, 21, and 28 days after immersion in staining solution using color eye 7000 spectrophotometer. The experimental data were analyzed using descriptive statistics, analyses of variance, and Tukey's post hoc test.Results:Epoxy (1.517 ± 0.071) and rhodium (0.297 ± 0.015) coated archwires showed the highest and lower value of surface roughness. All the intergroup comparisons showed a significant difference (P < 0.05) in surface roughness except between rhodium and control group (P = 0.998). There were significant differences between control and the experimental groups for both nanohardness and elastic modulus was observed. All the three NiTi-coated esthetic archwires demonstrated trace” (extremely slight change) color changes as measured by the National Bureau of Standards units after 4 weeks of immersion.Conclusion:Surface roughness of rhodium-coated archwires was almost similar to that of uncoated wires. Whereas Teflon and epoxy coated archwires showed a significant difference in surface roughness compared to uncoated archwires. Uncoated archwires showed higher nanohardness values compared to the coated archwires. Teflon-coated archwires demonstrated significantly slight color change after 4 weeks of immersion in staining solution.

Evaluation of nanomechanical and tribological properties of laser surface alloyed boride-nitride-carbide ceramic matrix composite coatings

Interesting mechanical and tribological properties, favorable for both ambient and high temperature applications, can be gathered by composites consisting of multiple reinforcing phases. The present study focuses on the characterization of ceramic matrix composite coatings with in-situ reinforcements, developed through combination of laser triggered chemical reaction and subsequent laser treatment. A preplaced precursor mixture of TiO2, SiO2, hBN and graphite powders in stoichiometric proportions is used for the chemical reaction activated by a high power laser beam to produce coatings containing TiB2, TiN, SiC and hBN. Minor modifications in the constituents of the preplaced precursor mixture helped in developing coatings different in terms of the amount of hBN and SiC present in it. This compositional variation brought significant changes in mechanical and tribological properties of the coatings. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) are used to confirm the presence of all the reaction products in the CMC coatings developed. Evaluation of nanomechanical properties and studies on the tribological properties of these coatings are performed thoroughly. Reduced modulus (Er) and nanohardness (H) of the composite coatings deposited on AISI 1025 steel have been measured from load–displacement curves. The stress-strain curves of composite coatings help in characterizing its damage tolerance and determining design stresses to find suitability to any application. Presence of hBN in composite coating causes reduction in coefficient of friction. Coatings formed with SiC in precursor helps in improving the specific wear rate. Top surface morphology and tribological properties of these coatings, after they are exposed to high temperature, are also explored.

Evaluation of nano-mechanical properties and morphology of filled polypropylene modified by irradiation

This paper describes the effect of electron beam irradiation on the surface properties (nano-indentation test) of glass fiber filled polypropylene (30%). These nano-mechanical properties were measured by the DSI (Depth Sensing Indentation) method on samples which were non-irradiated and irradiated by different doses of the β – radiation (33, 66 and 99 kGy). The purpose of the article is to consider to what extent the irradiation process influences the resulting nano-mechanical properties measured by the DSI method. The polypropylene tested showed significant changes of indentation hardness and modulus. The best results were achieved by irradiation at doses of 99 kGy (increase about 35%) by which the highest nano-mechanical properties of filled polypropylene were achieved. These changes were examined and confirmed by X-ray diffraction and Gel content.

ECMに刺激されたインテグリン-アクチン構造体の成熟過程におけるナノ力学特性評価

ECMに刺激されたインテグリン-アクチン構造体の成熟過程におけるナノ力学特性評価

Influence of the mathematical model on the evaluation of nanomechanical properties of ultrathin polymer layers studied by AFM

Abstract The major research topic presented in this study concerns nanoindentation experiments of thin soft films, showing high adhesion forces. The aim of this research was to evaluate the nanomechanical properties of a 200 nm thick thermoplastic polymer layer mr-I 7000E devoted to nanoimprint lithography. The experiments were carried out using an atomic force microscopy instrument equipped with a modified 14 N m− 1 silicon cantilever tip (5 μm in diameter). The forces exerted during film indentation varied from 0 up to 2.5 μN. The Hertz and Johnson – Kendall – Roberts (JKR) models were used for analysis of the force – distance curves in order to extract the Young's modulus value. Contrary to the Hertz model, in the JKR model the adhesion force between tip and sample was considered as an additional load during the nanoindentation. The final results of these estimations were 0.20 and 0.25 GPa for the Hertz and JKR models, respectively. It shows that neglect of the adhesion force may cause an error of 20 %.

Nanomechanical Analysis of Polymer Surfaces

Approaches and basic principles of the detailed analysis of force-distance data collected with scanning probe microscopy (SPM) are presented. We discuss nanomechanical probing routines for a single surface location and selected areas of polymer surfaces. Various approximations adapted for calculations of the surface elastic response and the adhesive forces are elaborated. Examples of SPM data analysis are discussed for compliant and hard polymer surfaces. The program package developed for the reliable processing of SPM data and the evaluation of nanomechanical properties is briefly described.