Microhardness Data Research Articles

Characterization of fine-scale rock structure and differences in mechanical properties in tight oil reservoirs: An evaluation at the scale of elementary lithological components combining photographic and X-ray computed tomographic imaging, profile-permeability and microhardness testing

Optimal development of tight-oil resources requires better petrophysical understanding of several key reservoir and mechanical properties. We highlight these for the Cardium Formation at the Pembina field, where controls on these properties appear to occur within elementary lithological components (ELCs) at the cm- to sub-cm scale moderated in part by the effects of synsedimentary bioturbation. This complexity in reservoir behavior necessitates new and innovative approaches for petrophysical property estimation, which is the subject of the current work. The workflow outlined starts with the quantification of the volumetric distribution of ELCs. For this purpose, 360° photographic imaging was used to first identify ELCs, and then quantify their volumetric percentages in whole core. This initial step is limited to the exposed surfaces of the core, consequently we used X-ray computed tomography (XRCT) in order to project the ELCs volumetric distribution into the core interior. The correlation between CT number, mineralogy, and bulk density of the rock further allowed porosity to be calculated from XRCT and shed light on its distribution throughout the core interior. Variations in fine-scale permeability were evaluated by collecting pressure-decay profile permeability measurements across a core slab surface following a 5×5mm-2D grid. Relationships between ELCs permeability and porosity were then generated and, when combined with the volumetric distribution of ELCs previously assessed, enabled a 3D distribution of reservoir quality at the mm-scale throughout the core. Finally, microhardness data was collected on the same 2D grid enabling ELC-scale quantification of mechanical properties. Reservoir properties of whole core samples identified in previous publications appear to be reasonably predicted when utilizing ELCs-specific permeability versus porosity transforms and volumetric percentages generated in this study, thus demonstrating scale-up potential.

Antibacterial properties of copper iodide-doped glass ionomer-based materials and effect of copper iodide nanoparticles on collagen degradation.

This study investigated the antibacterial properties and micro-hardness of polyacrylic acid (PAA)-coated copper iodide (CuI) nanoparticles incorporated into glass ionomer-based materials, and the effect of PAA-CuI on collagen degradation. PAA-CuI nanoparticles were incorporated into glass ionomer (GI), Ionofil Molar AC, and resin-modified glass ionomer (RMGI), Vitrebond, at 0.263wt%. The antibacterial properties against Streptococcus mutans (n=6/group) and surface micro-hardness (n=5/group) were evaluated. Twenty dentin beams were completely demineralized in 10wt% phosphoric acid and equally divided in two groups (n=10/group) for incubation in simulated body fluid (SBF) or SBF containing 1mg/ml PAA-CuI. The amount of dry mass loss and hydroxyproline (HYP) released were quantified. Kruskal-Wallis, Student's t test, two-way ANOVA, and Mann-Whitney were used to analyze the antibacterial, micro-hardness, dry mass, and HYP release data, respectively (p<0.05). Addition of PAA-CuI nanoparticles into the glass ionomer matrix yielded significant reduction (99.999%) in the concentration of bacteria relative to the control groups. While micro-hardness values of PAA-CuI-doped GI were no different from its control, PAA-CuI-doped RMGI demonstrated significantly higher values than its control. A significant decrease in dry mass weight was shown only for the control beams (10.53%, p=0.04). Significantly less HYP was released from beams incubated in PAA-CuI relative to the control beams (p<0.001). PAA-CuI nanoparticles are an effective additive to glass ionomer-based materials as they greatly enhance their antibacterial properties and reduce collagen degradation without an adverse effect on their mechanical properties. The use of copper-doped glass ionomer-based materials under composite restorations may contribute to an increased longevity of adhesive restorations, because of their enhanced antibacterial properties and reduced collagen degradation.

Tooth enamel properties and morphology after microabrasion: an in situ study

This study evaluated the effect of saliva on enamel after microabrasion with different microabrasive compounds under in situ conditions. Enamel/dentin blocks (16 mm2 ) from bovine incisors were divided into nine groups (n = 19): one control group (no treatment), four groups treated with microabrasion using 35% phosphoric acid (H3 PO4 ) + pumice, and the last four groups treated with microabrasion using 6.6% hydrochloric acid (HCl) + silica. The treated groups were subdivided according to the in situ regimen: without salivary exposure, 1 h, 24 h, or 7 days of saliva exposure. Surface microhardness (SMH) and cross-sectional microhardness (CSMH) were tested. Scanning electron microscopy (SEM) was used to evaluate enamel morphology. Microhardness data were tested by analysis of variance, and Tukey's and Dunnett's tests (α = 0.05). The SMH analysis revealed that all the microabrasion-treated groups presented significantly-reduced SMH values when compared to the control group (P < 0.05). Treatment with HCl + silica was more prone to the effect of saliva than H3 PO4 + pumice, even for CSMH analysis, once the superficial layers reached the same microhardness of that of the control group (P > 0.05). These results were confirmed by SEM, which demonstrated the mineral recovery effect over time. Saliva was effective in promoting the rehardening of enamel after microabrasion, mainly for the surfaces treated with HCl + silica.

Influência de agentes clareadores nas propriedades superficiais (rugosidade e microdureza) de uma cerâmica odontológica

Resumo O objetivo desse estudo in vitro foi avaliar a influência de agentes clareadores na rugosidade superficial e na microdureza de uma cerâmica odontológica (porcelana). Foram confeccionadas 30 amostras de cerâmica odontológica de 2 mm de espessura e 6 mm de diâmetro de acordo com as instruções do fabricante. Posteriormente, as amostras foram aleatoriamente divididas em 3 grupos (n=10) e avaliadas quanto à rugosidade e à microdureza para obtenção dos valores iniciais. Dois grupos foram submetidos ao tratamento superficial com agentes clareadores (GII: peróxido de hidrogênio a 9,5% e GIII: peróxido de hidrogênio a 37,5%). O GI, que constituiu o grupo controle, ficou imerso em água destilada. O peróxido de hidrogênio a 9,5% foi aplicado 3 h/dia por 3 semanas. O agente mais concentrado foi utilizado 3 vezes ao dia, por 8 min durante 3 semanas (uma vez por semana). Ao fim de cada exposição ao agente clareador, os espécimes foram lavados e armazenados em água destilada. Os dados obtidos relativos à rugosidade e à microdureza dos espécimes cerâmicos foram registrados nos intervalos de tempo: inicial (baseline) e 3 semanas após a aplicação dos agentes clareadores. A rugosidade e a microdureza de superfície não foram alteradas de maneira estatisticamente significativa, considerando o tempo de clareamento, independente do grupo analisado (p&gt; 0,05). Os valores médios da rugosidade (Ra em μm) foram: GI (0,084, 0,086, 0,078, 0,083), GII (0,085, 0,085, 0,086, 0,080) e GIII (0,079, 0,088, 0,083, 0,086). Os valores médios de microdureza (VHN em kgf/mm2) foram: GI (618, 589), GII (573, 578) e GIII (584, 600). Concluiu-se que as propriedades superficiais (rugosidade e microdureza) da cerâmica odontológica não foram alteradas pelo tratamento clareador. Novas pesquisas são necessárias para explicar o efeito do clareamento em cerâmicas odontológicas.

Effect of three nanobiomaterials on microhardness of bleached enamel.

ObjectivesThe aim of this in vitro study was to evaluate the effect of incorporating three different nanobiomaterials into bleaching material on microhardness of bleached enamel.Materials and MethodsThe crowns of 24 extracted sound human molars were sectioned. Sixty enamel specimens (2 × 3 × 4 mm) were selected and divided into five groups (n = 12): Group 1 received no bleaching procedure (control); Group 2 underwent bleaching with a 40% hydrogen peroxide (HP) gel; Groups 3, 4, and 5 were bleached with a 40% HP gel modified by incorporation of bioactive glass (BAG), amorphous calcium phosphate (ACP) and hydroxyapatite (HA), respectively. The enamel microhardness was evaluated. The differences in Knoop microhardness data of each group were analyzed by one-way ANOVA, followed by post hoc Tukey tests.ResultsSignificant differences were observed between the study groups. The enamel microhardness changes in Groups 1, 3, 4, and 5 were significantly lower than that of Group 2 (p < 0.001).ConclusionsWithin the limitations of this study, it can be concluded that incorporation of each one of the three tested biomaterials as remineralizing agents might be effective in decreasing enamel microhardness changes subsequent to in-office bleaching.

BMP2 Is Associated with Caries Experience in Primary Teeth

Bone morphogenetic proteins (BMPs) play an important role during the initial process of enamel development and therefore may play a role in caries susceptibility. The purpose of this study was to evaluate the association between the polymorphisms in the BMP2, BMP4 and BMP7 genes and their association with caries experience and primary enamel microhardness characteristics. DNA from buccal cells as well as clinical and demographic information from 1,731 subjects from three different data sets from Brazil were included. Polymorphisms in BMP2, BMP4 and BMP7 were analyzed by real-time polymerase chain reaction from genomic DNA. Association between caries experience, genotype, and allele distribution in both cohorts was evaluated using χ² and logistic regression analyses. In the family-based set, the association between caries experience and alleles was tested using the transmission disequilibrium test. In the Rio de Janeiro cohort, microhardness data on 108 exfoliated primary teeth before and after demineralization and remineralization challenges was included. Associations between microhardness values and genotype and allele distribution were evaluated using χ² and logistic regression analyses. Differences between caries experience and some risk factors were statistically significant. In the cohort from Nova Friburgo, BMP2 was associated with caries experience in primary dentition during logistic regression analysis (p = 0.023; OR = 2.58; 95% CI 1.13-5.86). There was no association between genotype and allele distribution for BMP polymorphisms and primary enamel microhardness alterations. Our result suggests that BMP2 may be involved in caries experience in primary dentition from a Nova Friburgo cohort.

Long-term accelerated weathering of HAS stabilized PE and PP plaques: Compliance of ESRI, IR, and microhardness data characterizing heterogeneity of photooxidation

Polymers in various applications are subjected to photooxidation processes resulting in loss of their material properties due to appearance of oxidation products and consequent degradation. Heterogeneous space distribution of concentration of oxidation products, crystallinity, stabilizer concentration and microhardness (MH) can be determined utilizing IR microspectroscopy and microhardness tester, respectively. We devoted this paper to direct determination of heterogeneity of the above mentioned parameters inside PE polymer plaques stabilized with secondary HAS Tinuvin® 770 and to the comparison of the data with nitroxide concentration profiles determined by ESRI that outline heterogeneity of the oxidation process inside the plaques. Data on heterogeneity of photooxidation processes in PP plaques stabilized with Tinuvin® 770 or binitroxide Prostab® 5415 are presented for comparison.

Determination of the Mechanical Properties of Plasma-Sprayed Hydroxyapatite Coatings Using the Knoop Indentation Technique

The microhardness and elastic modulus of plasma-sprayed hydroxyapatite coatings were evaluated using Knoop indentation on the cross section and on the top surface. The effects of indentation angle, testing direction, measurement location and applied load on the microhardness and elastic modulus were investigated. The variability and distribution of the microhardness and elastic modulus data were statistically analysed using the Weibull modulus distribution. The results indicate that the dependence of microhardness and elastic modulus on the indentation angle exhibits a parabolic shape. Dependence of the microhardness values on the indentation angle follows Pythagoras’s theorem. The microhardness, Weibull modulus of microhardness and Weibull modulus of elastic modulus reach their maximum at the central position (175 µm) on the cross section of the coatings. The Weibull modulus of microhardness revealed similar values throughout the thickness, and the Weibull modulus of elastic modulus shows higher values on the top surface compared to the cross section.

Is It Possible to induce Artificial Caries-affected Dentin using the Same Protocol to Primary and Permanent Teeth?

This in vitro study compared the mineral loss of natural and artificially-created caries-affected dentin in primary and permanent teeth using the same protocol to induce caries lesions. Twenty molars presenting natural occlusal dentin caries lesions (10 primary-PriC and 10 perma-nent-PermC; control group), and 20 sound molars (10 primary -PripH and 10 permanent-PermpH; experimental group), were selected. Occlusal cavities were prepared in teeth of the experimental group that were submitted to pH-cycling for 14 days to simulate caries-affected dentin. All specimens were longitudinally sectioned and prepared in order to obtain Knoop micro-hardness values from 15 to 250 urn depth, starting in bottom of center of natural lesions or cavities. The microhardness (KHN) data were submitted to three-way repeated measures analysis of variance (ANOVA) and Tukey's tests (α = 0.05). Considering all depths, there was no statistically significant differences (p > 0.05) between the mineral loss of the control (PriC = 30.9 ± 6.4 and PermC = 40.8 ± 8.6) and experimental (PripH = 27.3 ± 11.1 and PermpH = 35.5 ± 14.0) groups, neither between primary and permanent teeth. The mineral loss of the artificially-created caries-affected dentin is similar to that from naturally developed dentin caries lesions. The pH-cycling model may be a suitable method to simulate caries-affected dentin in both permanent and primary teeth.

Investigation of microhardness evolution in an ultrafine grained NiTi alloy formed via high speed high pressure torsion (HSHPT)

An investigation was conducted so as to evaluate the homogeneity of microstructure and mechanical properties of an NiTi shape memory alloy subjected to high speed high pressure torsion (HSHPT). The alloy chosen for the study had 50.3 at.% of Ni in its composition and was supplied in the form of hot extruded rods of 9 mm diameter. The final shape achieved after severe plastic deformation was a disc, whose diameter and thickness measured 40 mm and 0.18 mm, respectively. The TEM studies and the microhardness determination using a Vickers hardness tester revealed the effect of dynamic recrystallisation, which is very unique to severe plastic deformation involving HSHPT. An analysis of the microhardness data shows that the disc-shaped element is essentially homogeneous. In addition, the microhardness increases with the increase in accumulated strain. The results are presented and discussed in detail in the paper..

Characterization of a wollastonite glass-ceramic material prepared using sugar cane bagasse ash (SCBA) as one of the raw materials

Glass-ceramic material prepared with sugar cane bagasse ash as one of the raw materials was characterized to determine some important properties for its application as a coating material. X-ray diffraction patterns showed that wollastonite-2M (CaSiO3) was the major glass-ceramic phase. The Rietveld method was used to quantify the crystalline (60wt.%) and vitreous (40wt.%) phases in the glass-ceramic. The microstructure (determined by scanning electron microscopy) of this material had a marble appearance, showing a microporous network of elongated crystals with some areas with dendritic, feather-like ordering. Microhardness data gave a mean hardness value of 564.4HV (Vickers-hardness), and light microscopy disclosed a greenish brown colored material with a vitreous luster.

Influence of Aging Time on the Tensile Strenght of a Duplex Stainless Steel

This article was aimed at studying the influence of different aging times during the precipitation phase of the UNS S31803 (SAF 2205) duplex steel. To do so, all the test specimens were solution heat treated at 1050oC for 1 hour and quenched in water. After this step, the samples were aged at 850°C for periods of 10, 60 and 600 minutes and cooled in water. The aging heat treatments (TT) were performed in order to precipitate the sigma phase. Samples were subjected to microhardness and tensile tests so that the influence of the microstructural changes over the mechanical properties of the steel was assessed. Based on the microhardness and tensile test data, it was possible to verify a significant change over the mechanical properties of the UNS S31803 steel.

Assessment of the Mechanical Properties of ProTaper Next Nickel-Titanium Rotary Files

IntroductionThe purpose of this study was to compare the torsional resistance, flexibility, and surface microhardness of ProTaper Next files (PTN) with Twisted Files (TF) and RaCe (RC). MethodsA metal block with a cubical hole was used to evaluate the torsional resistance. Five millimeters of the tip of each file was securely held in place by filling the mold with a resin composite, and the files were driven clockwise at 300 rpm. The number of load applications before fracture was recorded for each file. A scanning electron microscope was used to characterize the topographic features of the fracture surfaces of the broken files. The files were tested for bending resistance by using cantilever-bending test. Vickers microhardness was measured on the cross section of instruments with 300-g load and 15-second dwell time. Torsional resistance data were analyzed by using the nonparametric Kruskal-Wallis and Mann-Whitney U tests. Bending resistance and microhardness data were analyzed by using analysis of variance and Tukey tests. ResultsPTN showed the highest torsional resistance and microhardness, followed by RC (P < .05). The fracture cross sections of all brands showed dimpling near the center of fracture surface. The ranking in the bending resistance values was as follows: RC > PTN > TF. ConclusionsPTN improved its resistance to torsional stresses and wear compared with TF and RC. TF showed improved flexibility compared with other tested brands.

Precipitate evolution in the early stages of ageing in Inconel 718 investigated using small-angle x-ray scattering

Microstructural evolution during the early stages of ageing (less than one hour) in a Ni–Cr–Fe based superalloy Inconel 718 (IN718) has been investigated using Small-Angle X-ray Scattering (SAXS). The effects of precipitate kinetics on the precipitate size distribution are compared indirectly with SAXS measurements by using Vickers microhardness data. The microhardness increased after 4min of ageing at a temperature of 760°C, although the recorded SAXS data did not reveal the precipitate size distribution. This indicates that the precipitates had not evolved enough to be detected, but still a small number of precipitates increased the yield strength. After ageing the alloy for the shortest period for which data were available, 8min, clear evidence of precipitates could be found from the SAXS data, showing that the γ″- precipitates are about 6nm in width and 3nm in height.

Investigation on superconducting properties of GdBa2Cu3O7−δ added with nanosized ZnFe2O4

The effect of nanosized ZnFe2O4, prepared by Co-precipitation method, on GdBa2Cu3O7−δ superconductor was studied. Therefore, superconducting samples of type (ZnFe2O4)xGdBa2Cu3O7−δ, 0.0⩽x⩽0.1wt.%, were prepared by the conventional solid-state reaction technique. Moreover, nanosized ZnFe2O4 was characterized using X-ray powder diffraction (XRD), transmission electron microscope (TEM) and magnetic hysteresis measurements. The results revealed that a nanosized ZnFe2O4 was achieved with average grain size 9nm and a super-paramagnetic hysteresis. On the other hand, the superconducting samples were characterized and investigated through XRD, scanning electron microscope (SEM), electrical resistivity, ac magnetic susceptibility and Vickers microhardness. XRD results showed that the volume fraction of Gd-123 phase increases as x rises from 0.0 to 0.06wt.% while the SEM results showed that the grain connectivity between the grains increases with increasing x. The superconducting transition temperature Tc, determined from electrical resistivity and ac magnetic susceptibility, increases up to x=0.06wt.%, and then it decreases. Moreover, electric field–current density (E–J) characteristic curves were measured at 77K. An improvement of the critical current density was obtained with x increase up to 0.06wt.%. Furthermore, the Vickers microhardness data were analyzed using Meyer’s law, Hays–Kendall approach, elastic/plastic deformation model and proportional specimen resistance model. The results indicated that Vickers microhardness number HV increases as x increases and it exhibits a normal indentation size effect. Moreover, the proportional specimen resistance model is found to be the best model to verify the experimental load independent Vickers microhardness values.

Multifunctional Erosion-Resistant Gas-Diffusion Coatings on Steels

Multicomponent coatings on 20 and Kh18N10T steels formed by the method of vacuum activated diffusion saturation are studied. A mixture of B4C, Al, Ni, Si, Cr, and C powders is used as the saturating medium. A thermodynamic analysis of reactions that accompany the titanizing process. Metallographic, micro-hardness, and X-ray diffraction data are discussed. The cavitation–erosion resistance of multicomponent coatings on steels is studied. It is established that these coatings improve the resistance of steel 20; the destruction rate being the same for both 20 and Kh18N10T steels.

Experimental and numerical assessment of mechanical properties of welded tubes for hydroforming

The identification of welded tubes properties considering the weld bead and Heat Affected Zone (HAZ) is important for reliable and accurate finite element simulation of tubular plastic forming processes such as tube hydroforming and rotary draw bending processes. Therefore, a simplified method is proposed to extract the weld bead and HAZ properties. Full size standard tensile specimens cut from the welded tube and comprising the weld parallel to the load direction are extended to failure. Mechanical properties obtained from uniaxial tensile test are correlated with the microhardness data measured across the welded specimen and by using the rule of mixtures; the constitutive model parameters of weld bead and HAZ regions are identified. Accuracy of the proposed method is assessed by comparing finite element simulation predictions to experimental measurements obtained from two mechanical tests: the first one is the uniaxial tensile test performed on specimens comprising the weld line perpendicular to the loading direction and the second test is the free bulge hydroforming test achieved on seamed tubular samples. This investigation has shown that the presented method is practical in use and sufficiently accurate to extract the weld metal properties of seamed tubes.

In vitro evaluation of enamel demineralization after several overlapping CO2 laser applications

This study aimed to evaluate the effects of repeated CO2 laser applications on the inhibition of enamel demineralization. Sixty-five human dental enamel slabs were randomly assigned to the following groups (n = 13): control (C), one application of the CO2 laser (L1), two applications of the CO2 laser (L2), three applications of the CO2 laser (L3), and four applications of the CO2 laser (L4). Enamel slabs were irradiated by a 10.6-μm CO2 laser operating at 5J/cm(2). The slabs were subjected to a pH-cycling regimen and then analyzed by FT-Raman spectroscopy, energy-dispersive X-ray fluorescence spectrometry (EDXRF), cross-sectional micro-hardness, and scanning electron microscopy (SEM). Statistical analysis was performed using ANOVA and Tukey tests (p < 0.05). FT-Raman spectroscopy showed a reduced carbonate content for L1, L3, and L4 groups when compared to C (p < 0.05). The EDXRF data showed no statistical differences between the control and irradiated groups for calcium and phosphorus components (p > 0.05). Cross-sectional micro-hardness data showed a statistically significant difference between the control and all irradiated groups (p < 0.05), but no difference was found among the irradiated groups (p > 0.05) up to 30-μm depth. A tendency of lower demineralization occurred in deeper depths for L3 and L4 groups. The SEM results showed that with repeated applications of the CO2 laser, a progressive melting and recrystallization of the enamel surface occurred. Repeated irradiations of dental enamel may enhance the inhibition of enamel demineralization.

Microstructure and interface characterization of dissimilar friction stir welded lap joints between Ti–6Al–4V and AISI 304

The feasibility of dissimilar friction stir welding (FSW) in overlap configuration between Ti–6Al–4V alloy (Ti64) and AISI 304 austenitic stainless steels (304SS) was investigated. Sound joints were achieved when placing titanium as the upper workpiece. Joints were successfully produced by employing a welding speed of 1mm/s and rotational speeds of 300 and 500rpm. A lamellar microstructure was formed in the stir zone of Ti64, where grain size was found to increase with increasing rotational speed, and austenitic equiaxed grains were obtained near the interface of 304SS coupon. Energy dispersive X-ray spectroscopy (SEM-EDS) of the interface revealed a thin intermixed region and suggested intermetallic compound formation. Microhardness data in the titanium weld zone for both rotational speeds exhibited slightly lower values than the base material, with the lowest values in the heat affected zone, whereas the microhardness values in the stainless steel side around the weld center were found to be higher than those obtained for the base material.

Effects of chemical agents on physical properties and structure of primary pulp chamber dentin.

This study evaluated the effects of chemical agents on the physical properties and structure of primary pulp chamber dentin using surface roughness, microhardness tests, and scanning electron microscopy (SEM). Twenty-five primary teeth were sectioned exposing the pulp chamber and were divided into five groups (n = 5): NT, no treatment; SH1, 1% sodium hypochlorite (NaOCl); SH1U, 1% NaOCl + Endo-PTC®; SH1E, 1% NaOCl + 17% EDTA; and E, 17% EDTA. After dentin treatment, the specimens were submitted to roughness, microhardness testing, and SEM analysis. Roughness and microhardness data were submitted to one-way ANOVA and Tukey's test (P < 0.05). The SH1E group showed the highest roughness, followed by the E group (P < 0.05) when compared with the NT, SH1, and SH1U groups. Microhardness values of SH1 and SH1U showed no significant difference as compared to the NT (control) group (P > 0.05). Microhardness values could not be obtained in the EDTA groups (SH1E and E). The presence of intertubular dentin with opened dentin tubules was observed in the NT, SH1, and SH1U groups. SH1E showed eroded and disorganized dentin with few opened tubules and the intertubular/peritubular dentin was partially removed. Considering the physical and structural approaches and the chemical agents studied, it can be concluded that NaOCl and NaOCl associated with Endo-PTC® were the agents that promoted the smallest changes in surface roughness, microhardness, and structure of the pulp chamber dentin of primary teeth.