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I Sabirov - One of the best experts on this subject based on the ideXlab platform.
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the sensitivity of the microstructure and properties to the peak temperature in an ultrafast heat treated low carbon steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020Co-Authors: M A Valdestabernero, Ankit Kumar, Roumen Petrov, M A Monclus, J M Molinaaldareguia, I SabirovAbstract:Abstract In this work, we investigate the sensitivity of the microstructure and mechanical properties of an ultrafast heat treated low carbon-steel to the peak temperature. In all studied cases, the steel was heated within the intercritical temperature range (i.e. between the AC1 and AC3 temperatures). Both the peak temperature and soaking time were varied, and their effect on the size, the fraction of individual microstructural constituents and their tensile mechanical response were investigated. It is shown that the increasing peak temperature and soaking time promote austenite formation and recrystallization processes in the ferritic matrix. The highest Nanohardness is shown by martensitic grains, while recovered ferrite demonstrated slightly higher Nanohardness compared to recrystallized ferrite. The applied heat treatment parameters have a strong effect on the Nanohardness of martensite, whereas the Nanohardness of ferrite microconstituents is not sensitive to variations of peak temperature and soaking time. The non-recrystallized ferrite is harder than its recrystallized counterpart due to the higher dislocation density of the former. Increasing peak temperatures promote strengthening in the material at the expense of its ductility mainly due to increased martensite fraction. The steel demonstrates enhanced strain hardening ability independently of the peak temperature. Analysis of the experimental results showed that the industrial processing window of ±10 °C may lead to some heterogeneity of the local microstructure in the ultrafast heat treated sheets. However, the latter should not have any negative effect on the overall mechanical behavior of the ultrafast heat treated steel sheets on the macro-scale.
Manuel Toledano - One of the best experts on this subject based on the ideXlab platform.
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A zinc-doped endodontic cement facilitates functional mineralization and stress dissipation at the dentin surface.
Medicina oral patologia oral y cirugia bucal, 2018Co-Authors: Manuel Toledano, M-c Pérez-Álvarez, C-d Lynch, Estrella Osorio, R. Osorio, Manuel Toledano-osorioAbstract:The purpose of this study was to evaluate Nanohardness and viscoelastic behavior of dentin surfaces treated with two canal sealer cements for dentin remineralization. Dentin surfaces were subjected to: i) 37% phosphoric acid (PA) or ii) 0.5 M ethylenediaminetetraacetic acid (EDTA) conditioning prior to the application of two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite), respectively. Samples were stored in simulated body fluid during 24 h or 21 d. The intertubular and peritubular dentin were evaluated using a nanoindenter to assess Nanohardness (Hi). The load/displacement responses were used for the nano-dynamic mechanical analysis to estimate complex modulus (E*) and tan delta (δ). The modulus mapping was obtained by imposing a quasistatic force setpoint to which a sinusoidal force was superimposed. AFM imaging and FESEM analysis were performed. After 21 d of storage, dentin surfaces treated with EDTA+calcypatite, PA+calcypatite and EDTA+oxipatite showed viscoelastic discrepancies between peritubular and intertubular dentin, meaning a risk for cracking and breakdown of the surface. At both 24 h and 21 d, tan δ values at intertubular dentin treated with the four treatments performed similar. At 21 d time point, intertubular dentin treated with PA+oxipatite achieved the highest complex modulus and Nanohardness, i.e., highest resistance to deformation and functional mineralization, among groups. Intertubular and peritubular dentin treated with PA+oxipatite showed similar values of tan δ after 21 d of storage. This produced a favorable dissipation of energy with minimal energy concentration, preserving the structural integrity at the dentin surface.
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zinc induces apatite and scholzite formation during dentin remineralization
Caries Research, 2014Co-Authors: Raquel Osorio, E Osorio, Inmaculada Cabello, Manuel ToledanoAbstract:The aim of this study was to ascertain whether zinc may improve the repair ability of demineralized dentin. Dentin disks were demineralized by phosphoric acid during 15 s and immersed in artificial saliva, remineralizing solution, a zinc chloride solution and a zinc oxide solution. Dentin specimens were analyzed after 24 h and 1 month of storage. Surface morphology was assessed by atomic force and scanning electron microscopy, mechanical properties were analyzed by Nanohardness testing in a TriboIndenter, and chemical changes at the surfaces were determined by X-ray diffraction, Raman and energy-dispersive elemental analyses. After phosphoric acid application, dentin was only partially demineralized. Demineralized dentin was remineralized after 24 h of storage in any of the tested solutions (Nanohardness increased and hydroxylapatite formation was detected by Raman). Remineralization was maintained up to 1 month in dentin stored in remineralizing solution, zinc chloride and zinc oxide. Zinc and phosphate were important for hydroxylapatite homeostasis. Scholzite formation was encountered in dentin stored in zinc-containing solutions. Zinc might allow to reach the balance between dentin demineralization and remineralization processes.
Anoop Kumar Mukhopadhyay - One of the best experts on this subject based on the ideXlab platform.
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Influence of loading rate on Nanohardness of sapphire
Ceramics International, 2016Co-Authors: Manjima Bhattacharya, Arjun Dey, Anoop Kumar MukhopadhyayAbstract:Abstract This work reports the loading rate effect on Nanohardness of sapphire. The intrinsic nanoscale contact deformation resistance of sapphire increased with the loading rates following empirical power law dependence with a positive exponent. The results showed a significant enhancement (e.g., ~66%) of the Nanohardness of sapphire with the increase in loading rates from 10 to 10,000 μN s −1 . These results were explained mainly in terms of the maximum shear stress generated underneath the nanoindenter, dislocation density and critical resolved shear stress of the sapphire.
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grain boundary Nanohardness of coarse grain alumina
International Journal of Applied Ceramic Technology, 2015Co-Authors: Arjun Dey, Manjima Bhattacharya, Anoop Kumar MukhopadhyayAbstract:Here, we present the results of nanoindentation experiments conducted at ultralow peak loads of, for example, 1000, 5000, and 10,000 μN on a dense (~99.5%), coarse grain (~10 μm) alumina ceramic. The results showed that the Nanohardness values of alumina were sensitive to the applied loads as well as to the locations of measurements, for example, the center of the grain, away from the center of the grain and at the vicinity of the grain boundary. The location sensitivity of Nanohardness was linked to compositional variations of the different locations and to the presence of an amorphous phase.
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role of the energy of plastic deformation and the effect of loading rate on Nanohardness of soda lime silica glass
2010Co-Authors: Riya Chakraborty, Arjun Dey, Anoop Kumar MukhopadhyayAbstract:The role of energy dissipated by plastic deformation during Nanohardness testing of a soda-lime-silica glass with a Berkovich indenter for various peak loads (100-1000 mN) as a function of loading rate (1-1000 mN s(-1)) was examined. The maximum increase in Nanohardness with loading rate was about 10%. The maximum rate of enhancement in Nanohardness with loading rate, was found to occur up to a threshold loading rate (TLR) where a change of deformation mechanism happens. TLR was shown to be linked to the maximum in the relative amount of energy dissipated in plastic deformation which contributed to the enhancement of Nanohardness. A new concept of inelastic deformation (IED) parameter was found to describe well the observed trend of Nanohardness on loading rate. It was established further that the maximum magnitude of the IED parameter occurred when the relative amount of energy dissipated in plastic deformation during the nanoindentation process was also a maximum. Thus, the interrelation between the amount of energy dissipated in plastic deformation and the IED parameter could be utilized to suggest why the maximum rate of change in enhancement of Nanohardness of the present glass with loading rate occurred at the TLR values.
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anisotropy in Nanohardness of microplasma sprayed hydroxyapatite coating
Advances in Applied Ceramics, 2010Co-Authors: Arjun Dey, Anoop Kumar MukhopadhyayAbstract:Abstract Abstract In the present paper, the authors report the observation of pronounced Nanohardness anisotropy in a phase pure, 230 μm thick microplasma sprayed bioactive hydroxyapatite coating on a surgical grade SS316L substrate. The coating had a very heterogeneous microstructure with a large number of macrocracks, microcracks, inter- and intrasplat cracks, intra- and interlamellar macro- and micropores, etc. The Nanohardness values measured by the nanoindentation technique at various loads in the range 10-1000 mN on cross-section was usually higher than those measured on plan-section of the coating. This anisotropy of Nanohardness could be attributed to the larger volume per cent porosity as well as higher spatial density of planar defects, pores and cracks on plan-section over those in the cross-section. In addition, the dependence of hardness on porosity of hydroxyapatite was studied in detail.
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evaluation of microwave processed glass ceramic coating on nimonic superalloy substrate
Ceramics International, 2010Co-Authors: Sumana Das, Anoop Kumar Mukhopadhyay, Someswar Datta, Debabrata BasuAbstract:Abstract MgO–Al 2 O 3 –TiO 2 based glass–ceramic coatings were formed on nimonic superalloy substrates by microwave and conventional heat treatment processes. The resultant glass–ceramic coatings were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), image analysis, Nanohardness and Young's modulus evaluation by depth sensitive indentation (DSI) technique. Nanohardness and Young's modulus values of the microwave heat treated glass–ceramic coatings were improved in comparison to those of the conventionally treated glass–ceramic coatings due to presence of finer sized crystallites in the microwave processed coatings. Slight enhancement in the Nanohardness and Young's modulus values with soaking time for the microwave processed coatings were explained in terms of the microstructural refinement and the reinforcement of the parent glass matrix.
Roumen Petrov - One of the best experts on this subject based on the ideXlab platform.
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the sensitivity of the microstructure and properties to the peak temperature in an ultrafast heat treated low carbon steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020Co-Authors: M A Valdestabernero, Ankit Kumar, Roumen Petrov, M A Monclus, J M Molinaaldareguia, I SabirovAbstract:Abstract In this work, we investigate the sensitivity of the microstructure and mechanical properties of an ultrafast heat treated low carbon-steel to the peak temperature. In all studied cases, the steel was heated within the intercritical temperature range (i.e. between the AC1 and AC3 temperatures). Both the peak temperature and soaking time were varied, and their effect on the size, the fraction of individual microstructural constituents and their tensile mechanical response were investigated. It is shown that the increasing peak temperature and soaking time promote austenite formation and recrystallization processes in the ferritic matrix. The highest Nanohardness is shown by martensitic grains, while recovered ferrite demonstrated slightly higher Nanohardness compared to recrystallized ferrite. The applied heat treatment parameters have a strong effect on the Nanohardness of martensite, whereas the Nanohardness of ferrite microconstituents is not sensitive to variations of peak temperature and soaking time. The non-recrystallized ferrite is harder than its recrystallized counterpart due to the higher dislocation density of the former. Increasing peak temperatures promote strengthening in the material at the expense of its ductility mainly due to increased martensite fraction. The steel demonstrates enhanced strain hardening ability independently of the peak temperature. Analysis of the experimental results showed that the industrial processing window of ±10 °C may lead to some heterogeneity of the local microstructure in the ultrafast heat treated sheets. However, the latter should not have any negative effect on the overall mechanical behavior of the ultrafast heat treated steel sheets on the macro-scale.
František Lofaj - One of the best experts on this subject based on the ideXlab platform.
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mechanical and tribological properties of the high target utilization sputtering w c coatings on different substrates
International Journal of Refractory Metals & Hard Materials, 2016Co-Authors: František Lofaj, Petra Hviščová, Pavol Zubko, Dusan Nemeth, Margita KabátováAbstract:Abstract The effects of three types of substrates (Si, bearing steel, and WC-Co) and acetylene addition (0–3.2 vol.% in Ar atmosphere) on the topography, structure, composition, Nanohardness and tribological behavior of the High Target Utilization Sputtering W-C coatings were investigated. The results showed that the substrates affected mostly the coating topography, roughness and Nanohardness whereas the composition, indentation moduli and coefficients of friction were influenced only by the increase of free carbon content from acetylene addition. Up to ~ 5 GPa difference in the hardness of the W-C coatings on Si substrates compared to that on steel was obtained. Simultaneously, methodological problems with the hardness measurements were identified on WC-Co substrate which has the hardness close to that of the coatings. The average values of the coefficient of friction were around 0.3 and slightly decreased at higher carbon contents but the influence of the substrates was small.
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the influence of indentation conditions on Nanohardness depth profiles of w c based coatings
Key Engineering Materials, 2014Co-Authors: Michal Novak, František Lofaj, Petra HviščováAbstract:The influence of different indentation parameters including loading type, loading/strain rate, frequency and amplitude on Nanohardness depth profiles on DC-MS W-C based coatings thick from 300 to 850 nm were investigated with the aim to determine the best conditions for the measurement of hardness of thin films during sinusoidal loading cycle. Nanohardness tests were performed on G200 (Agilent Technologies) and NHT (CSM Instruments) nanoindenters using standard loading/unloading cycle, CMC (continuous multicycle) mode and continuous stiffness measurement method (CSM) or sinus mode, respectively. The increase of strain rate and sinus amplitude results in decrease of maxima hardness of profiles while the increase of frequency caused its increase.
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Nanohardness of crn coatings versus deposition parameters
Key Engineering Materials, 2014Co-Authors: Petra Hviščová, František Lofaj, Michal NovakAbstract:Nanohardness of chromium nitrid coatings deposited with DC magnetron from Cr target in the reactive atmosphere with various percentual contribution of nitrogen in Ar flow was investigated to determine the influence of nitrogen content and negative bias. The Nanohardness of pure Cr coating was between 11 14 GPa and the addition of 50 % of nitrogen into Ar flow resulted in the increase of coating hardness up to ~ 22 GPa. The highest hardness of the studied CrN coatings of ~ 28 GPa was achieved at 700 W power, working pressure of 0.5 Pa with 50 % of nitrogen in Ar flow and negative bias of-30 V . The increase was ascribed to the formation of near-stoichiometric CrN compounds.
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Nanohardness and tribological properties of nc tib2 coatings
Journal of The European Ceramic Society, 2013Co-Authors: František Lofaj, Tomasz Moskalewicz, Grzegorz Cempura, Marian Mikula, J Dusza, A CzyrskafilemonowiczAbstract:Abstract The work is devoted to the investigation of Nanohardness and tribological properties in TiB 2 coatings deposited on austenitic steel substrates using an unbalanced magnetron sputtering with the focus on the coatings prepared under small negative bias to reduce compressive stresses. The coating prepared under floating potential exhibited nanocomposite microstructure with the size of TiB 2 (hcp) nanocrystallites in the range of 2–7 nm. It is in contrast with the textured microstructure typically developed under higher negative bias. The reduction of the compressive stresses up to −0.4 GPa while keeping the Nanohardness >30 GPa and the coefficient of friction of 0.77 were obtained in this coating. The highest Nanohardness of 48.6 ± 3.1 GPa and indentation modulus of 562 ± 18 GPa were achieved at −100 V bias in the textured coating. The friction mechanisms include mechano-chemical formation of a tribological oxide film between the sliding partners combined with an abrasive wear.
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Nanohardness of individual phases in wc co cemented carbides
Key Engineering Materials, 2013Co-Authors: Annamaria Duszova, František Lofaj, Radoslav Halgas, Pavol Priputen, Marek Bľanda, Pavol Hvizdos, Jan DuszaAbstract:The Nanohardness of WC – Co hardmetals has been investigated using instrumented indentation and Berkovich tip indenter. The Nanohardness, HIT, and indentation modulus, EIT, of Co phase and individual WC grains and the influence of their crystalographic orientation have been studied. SEM, AFM and EBSD methods were used for the characterization of the microstructures and indents and for the identification of crystallographic orientation of WC grains, respectively. Strong indentation load-size effect and significant influence of the crystallographic orientation of WC crystals on HIT and EIT have been found. The Nanohardness of Co binder was approximately 10 GPa and that of WC grains varied between 25 and 50 GPa, depending on the grain orientation and load. The Nanohardness values of the basal and prismatic planes of individual WC grains at load of 10 mN were 40.4 ± 1.6 GPa and 32.8 ± 2.0 GPa, respectively.
