Equivalent Circle Diameter Research Articles

Behavior of organic matter-hosted pores within shale gas reservoirs in response to differential tectonic deformation: Potential mechanisms and innovative conceptual models

Remarkable breakthroughs have been achieved in exploration of marine shale gas, acting as important cleaner energy resources in complex tectonic regions, encouraging us to accurately estimate different reservoir capacity of tectonically deformed gas shales. In particular, organic matter (OM) pore system, acting as the most important storage space for high-over-mature marine gas-shale reservoirs in South China has not yet been specifically targeted and comparatively studied in a regional and differential tectonic deformation regime. A set of shale drilling core samples from the Upper Silurian to Lower Ordovician Wufeng-Longmaxi Formations in the Sichuan Basin and its periphery were targeted by a multi-methodical approach utilizing organic geochemistry and mineralogical investigations, FE-SEM observation and digital image processing and extraction, and combined fluid intrusion (N2 and CO2 adsorption analysis). From undeformed shales (UDS) through slightly deformed shales (SDS) to intensely deformed shales (IDS), an obviously and progressively “Triple Jump” reduction in multi-scale pore volume and specific surface areas, and characteristic parameters for OM pores including the plane porosity (Phi) (the average dropped from 23.14% to 10.33%), the equivalent circle diameter (ECD) (the average dropped from 28.38 nm to 10.09 nm), the perimeter over area (PoA) (the average rose from 0.1126 to 0.2718), and the dominant pore diameter (DOM size) (the average dropped from 113.80 nm to 20.78 nm). The reactivation of seepage channels and intrusion of brittle minerals are proposed as two main microscopic forcing mechanisms, updated and innovative conceptual models are proposed to reconstruct an OM pore response processes under a differential tectonic deformation regime in panoramic view for Lower Paleozoic marine gas shale reservoirs of China. Thus, an evolution of spatial resolution spanning a total of three different scales respectively as structural styles, shale reservoir architectures, and microscopic petrological compositions are together portrayed.

Variation in thyroid volumes due to differences in the measured length or area of the cross-sectional plane: A validation study of the ellipsoid approximation method using CT images.

PurposeThis study examined the variation in the thyroid volume determined by the ellipsoid approximation method due to differences in the measured length or area of the cross‐sectional plane of CT images.MethodsForty‐five patients with Graves' disease were included in this retrospective study. We designated the three‐dimensional thyroid volumes extracted manually (V CT) as the reference data and calculated five approximate volumes for comparison: (a) the mean volume of 8100 different thyroid volumes depending on the diameter of the cross‐sectional plane at the midpoint of the major axis, (V ellipsoid,mean); (b) the volume using the maximum diameter and its orthogonal diameter, (V ellipsoid,maxlength); (c) the maximum (V ellipsoid,maxvolume); (d) minimum (V ellipsoid,minvolume) of the 8100 thyroid volumes; and (e) the volume determined with an equivalent circle diameter, (V ellipsoid,Heywood).ResultsThyroid volumes obtained via the ellipsoid approximation method varied depending on the diameter of the cross‐sectional plane and included a mean error of approximately 20%, while the concordance correlation coefficient (CCC) differed for each approximate volume. Among these volumes, V ellipsoid,mean and V ellipsoid,Heywood were in good agreement with V CT, according to single regression analyses and the resultant CCC values, with mean errors of 0.1% and 10.4%, respectively.ConclusionWhile V ellipsoid,Heywood approximated thyroid volumes with vastly reduced errors, we recommend utilizing three‐dimensional thyroid volumetry if measurement accuracy is required.

On-line measurement of pulverized coal fineness on a 300 MWe power plant with pulsed digital inline holography

Pulverized coal fineness (PCF) is a key parameter in coal-fired power plants, demanding accurate and on-line monitoring. This study presents on-line measurement of PCF on a 300 MWe coal-fired power plant with pulsed digital inline holography (DIH). A prototypal instrumentation system, comprised of sampling, measurement, collection, and output, is established and tested on the two mills of the plant. Fineness characterized by the size-area distribution (SAD) and various size-volume distributions (SVD) obtained by DIH are compared to the size-mass distribution (SMD) by the off-line sieving method. The absolute R90 deviations of SAD are 3.60% and 3.72% for the two mills, respectively, with the equivalent area circle diameter (Deac) to estimate the sieve size (Ds). A SVD for which Ds is estimated by the maximum inscribed circle diameter (Dmic) and the particle volume (VSeac) by the equivalent sphere with diameter of Deac yields the deviations of 2.18% and − 0.25%.DIH is applied to the on-line coal fineness monitoring on a 300 MWe power plant. An on-line holographic instrumentation system is established. Fineness results indicate the operation conditions of the tested mills. Different fineness characterizations are compared and two optimums are recommended.

Measurement of the five morphological indexes of follicles using image processing toolbox

This study aims to investigate the morphological characteristics of mature follicles with clinical value. The five morphological indexes of follicles in 72 natural ovulation cycles were measured. The shoot time of follicle photos was the day before ovulation. Measurement software was the MATLAB Image Processing Toolbox. The measured average area, perimeter, equivalent circle diameter, and roundness were 301.29 ± 8.52 mm2, 62.23 ± 6.82 mm, 20.21 ± 3.08 mm, and 0.89 ± 0.05, respectively; and the maximal diameter was 23.12 ± 3.06 mm. Image Processing Toolbox is a simple and convenient measurement software. The standardization of the reference indexes of follicular morphology has important clinical application value in reproductive medicine.

A Study of Particle Size Metrics Using Non-Spherical Feedstock for Metal Additive Manufacturing

The goal of this work was to determine which standard particle size metric derived from optical analysis most closely approximates the sieved weight percent of irregularly shaped powder intended to be used for directed energy deposition. In this investigation, equivalent circle diameter, maximum diameter, minimum diameter, and perimeter were used as metrics to “virtually sieve” the particles in samples of irregularly shaped powder into the following particle size bins: <45 µm, 45 µm – 150 µm, and >150 µm. The percentage in the 45 µm – 150 µm bin were then compared to the weight percent of the powder mechanically sieved into this size range. The absolute difference between the virtually sieved percentage and the mechanically sieved percentage was assessed for 81 samples of mechanically-generated stainless steel 316L powder, all produced under different processing conditions in an oscillation ball mill. This difference was found to be on average, the least with the minimum diameter assessed as an area percentage, followed by the equivalent diameter assessed as an area percentage, and then the maximum diameter assessed as a percentage of the total number of particles ranked third. These findings and the methodology used to obtain them may be used by powder production process engineers and quality assurance personnel to assist in process control as more diverse additive manufacturing feedstocks become utilized.

Attribute Profiles of Different Attributes for Spectral-Spatial Classification of Hyperspectral Imagery

Incorporation of spatial information along with spectral features has a great impact on the analysis of hyperspectral images (HSIs). Attribute profiles have been proved to be a very effective state-of-the-art method for fusing spectral and spatial information in HSI. This paper recalls the construction of attribute profiles (APs) for HSI classification and provides a comprehensive analysis of different properties of connected components that can be used as an attribute while constructing APs. Various attributes have been widely and successfully used to construct attribute profiles for spectral-spatial classification of HSIs. In this paper, we investigate several unexplored attributes in addition to the existing ones. An empirical study on the attribute profiles, constructed by using different attributes, is carried out considering three real HSI data sets. Our study reveals that each attribute possesses interesting filtering capabilities among which the attributes namely complexity and diameter of equivalent circle, which are new in the HSI literature, are found most promising to incorporate spatial information for HSI classification. The paper also lists out suitable attributes for recognition of different classes in a remote sensing scene.

Structural analysis of porous bioactive glass scaffolds using micro-computed tomographic images

Three-dimensional structural properties such as pore size, interconnectivity, and tortuosity of scaffold play an essential role in bone tissue regeneration. We report the structural characterization of bioactive glass-based scaffolds by employing micro-computed tomography (µCT) imaging. µCT images were filtered and binarized to get 3D reconstruction of the scaffold. Fast march method was applied on 3D reconstructed scaffold to estimate tortuosity. Further, Canny edge detection algorithm was used to identify pore boundaries. Graph traversal algorithm was used to identify pore networks as open, close, and through. Pore and minimum throat size for a through path were quantified using equivalent circle diameter based on ASTM F2603-06. The porosity (66.69%), mean pore size (443 µm), mean pore throat diameter (131 µm), and tortuosity in different planes (~ 1) imply suitability of the scaffold for bone tissue engineering. Any porous sample can be characterized by the methodology directly with µCT or other imaging techniques.

Fabrication of TiC from the Cu–Ti–C system under the super-gravity field

Abstract An innovative approach of fabricating fine TiC particles through the dissolution of solid carbon in the CuxTi melt and subsequently separation with super-gravity is proposed in this study. The reactant mixtures of titanium sponge, copper and carbon particles reacted at 1573 K for 4 h and then the near-spheroidal TiC grains gradually precipitated out of the Cu–Ti–C system. The influences of copper content, separating temperature, gravity coefficient and separating time on the separation of precipitated TiC from the Cu–Ti–C melt have been studied. The particle size distribution and stoichiometric of TiC were calculated, and the detailed mechanism of fabricating TiC was discussed. The experimental results showed that the mass fraction of copper mixed with TiC in the residue was 6.5 wt% and the yield of the copper-rich phase exceeded 89 wt% under super-gravity treatment with the conditions of χCu = 90 wt%, T = 1523 K, t = 120 s and G = 600. After leaching with the sulfuric acid solution, the purity of TiC particulates was 99 wt% and the removal rate of the copper impurity could be up to 97.8%. Finally, the product of the homogeneous and fine TiC particles with good dispersibility was obtained. The circle equivalent diameter and the median diameter of the TiC particulates were found to be 2.09 μm and 2.12 μm, respectively. The elongation and the aspect ratio of the TiC particulates were 83.4% and 74.4%, respectively. Moreover, the lattice parameter of the purified TiC particulates was calculated by the Nelson-Riley extrapolation function which was near to the standard value, and the stoichiometry of TiC particulates obtained in this work was close to 1.

Characterization of the Microstructure and Precipitates Formed During the Thermomechanical Processing of a CrNiMoWMnV Ultrahigh‐Strength Steel

The effect of total applied strain (TAS), finish forging temperature (FFT) on the microstructure, and precipitation kinetics of a newly developed low‐cost, low‐alloy CrNiMoWMnV ultrahigh‐strength steel has been investigated. A Gleeble 3800 thermomechanical simulator is used to simulate the hot forging process and its influence on the precipitation kinetics. Field‐emission scanning electron microscopy combined with electron‐backscattered diffraction is used to characterize the final overall microstructures, whereas transmission electron microscopy on carbon extraction replicas is used to characterize the precipitates in terms of morphology, size distribution, mean equivalent circle diameter, the 90th percentile in the cumulative diameter distribution (D90%ppt), chemical composition, and crystallography. Thermo‐Calc software is used to predict the precipitates expected in austenite at equilibrium. The final microstructure consists of lath martensite and a small fraction of the precipitates AlN, TiN, and composite TiN–AlN. Differences in the degree of strain‐induced precipitation caused by variations in TAS and FFT have been shown to greatly influence precipitate size distributions. Variations in the degree of precipitate dissolution and coarsening cause variations in the prior austenite grain size, which subsequently cause variations in the effective grain size of the final microstructure, i.e., that are defined by high‐angle grain boundaries.

Prediction of Inclusion State in Molten Steel by Morphology and Appearance of Inclusions in Liquid Steel Samples

Inclusions are unwanted but to some extent inevitable in molten and solid steel. Usually solid inclusions are considered to be the most harmful. Inclusions can be converted into a less detrimental form with calcium treatment. The success of calcium treatment can be evaluated by analyzing the state of the inclusion population. The state of inclusions is usually determined by computational thermodynamics making use of the chemical composition of inclusions and system conditions. In this process, liquid and solid inclusions are usually distinguished. Herein, a classification procedure which combines computational thermodynamics and data‐driven reasoning is presented. The objective of this work is to study the predictability of the inclusion state based on its appearance and morphological properties. As a result, Al2O3–CaO–MgO–CaS inclusions are classified as liquid and solid ones based on their aspect ratio, equivalent circle diameter, and mean gray value with a recall of 82.7% and precision of 84.9%, by making use of a logistic regression‐based classifier.

Evaluation of coal component liberation upon impact breakage by MLA

To elucidate the coal component liberation mechanisms upon typical impact breakage, the coal was selected from the Shangwan mine in China. Thereafter, mineral liberation analysis was adopted as the main method for investigating phase interface characteristics, classification characteristics of the various classes of comminuted products, and changes in the mineral area and length gradients upon mechanical impact breakage. The results indicate that the grain sizes of the comminuted products decreased in the following order: slag product >classifier product >bag product. Moreover, the disseminated grain size, dissemination mode, and original cleavages had a direct influence on the recovery rate of the completely liberated phase. The coal, which formed the main component of the samples, exhibited the highest cumulative mass recovery (CMR) in classified products and was most easily liberated. Furthermore, the kaolinite-bearing coal and pyrite were moderately liberated, the quartz and kaolinite were difficult to liberate, and the illite was extremely difficult to liberate. Under mechanical impact breakage, intragranular and intergranular fractures mainly occurred in particles, with the changes in the mineral boundary and mineral area corresponding to varying fracture modes. To a certain extent, the particle comminution could be quantified by the changes in the slope of the equivalent circle diameter–-CMR curve. It was determined that the main cause of the increased liberation degree is the generation of the completely liberated phase of the component of interest. Furthermore, by adopting the liberation factor for quantification of the mineral liberation, the calculation model for coal component liberation was obtained.

Particle analysis of shape factors according to American Society for Testing and Materials.

Polyethylene wear is one of the major factors influencing the survivorship of joint replacements. Depending on the number, size and morphology of the polyethylene particles, biological responses of the periprosthetic soft tissue in terms of inflammatory processes can occur, leading to loosening of the implant. Various parameters are used to analyze wear particles, which are usually determined by examining scanning electron microscopy (SEM) images with a particle analysis program. In this study, three different software solutions for particle analysis (self-developed Particleanalyzer_HD, Leica QWin and ImageJ) were compared regarding particle number, size and morphology. These solutions were also compared to the American Society for Testing and Materials (ASTM) F1877-16 specifications regarding particle morphology. SEM image analysis revealed no differences for the equivalent circle diameter (p = 0.969). However, a significant difference was found for the aspect ratio between the Particleanalyzer_HD and the other two software solutions (p < 0.001) and between Leica QWin and the other two software solutions regarding the roundness (p < 0.001). Only the Particleanalyzer_HD showed an excellent agreement with the ASTM standard for both morphology parameters (intraclass correlation = 1.000). Only the Particleanalyzer_HD calculated the two morphology parameters according to the ASTM standard. A comparison of the particle morphology between different studies is barely possible, as different algorithms for particle analysis are used. It is strongly recommended that the calculation according to the ASTM standard is used to improve future comparability of findings from wear analysis studies. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:225-233, 2020.

In situ terminal settling velocity measurements at Stromboli volcano: Input from physical characterization of ash

Ash particle terminal settling velocity is an important parameter to measure in order to constrain the internal dynamics and dispersion of volcanic ash plumes and clouds that emplace ash fall deposits from which source eruption conditions are often inferred. Whereas the total Particle Size Distribution (PSD) is the main parameter to constrain terminal velocities, many studies have empirically highlighted the need to consider shape descriptors such as the sphericity to refine ash settling velocity as a function of size. During radar remote sensing measurements of weak volcanic plumes erupted from Stromboli volcano in 2015, an optical disdrometer was used to measure the size and settling velocities of falling ash particles over time, while six ash fallout samples were collected at different distances from the vent. We focus on the implications of the physical parameters of ash for settling velocity measurements and modeling. Two-dimensional sizes and shapes are automatically characterized for a large number of ash particles using an optical morpho-grainsizer MORPHOLOGI G3. Manually sieved ash samples show sorted, relatively coarse PSDs spanning a few microns to 2000 μm with modal values between 180 and 355 μm. Although negligible in mass, a population of fine particles below 100 μm form a distinct PSD with a mode around 5–20 μm. All size distributions are offset compared to the indicated sieve limits. Accordingly, we use the diagonal of the upper mesh sizes as the upper sieve limit. Morphologically, particles show decreasing average form factors with increasing circle-equivalent diameter, the latter being equal to 0.92 times the average size between the length and intermediate axes of ash particles. Average particle densities measured by water pycnometry are 2755 ± 50 kg m−3 and increase slightly from 2645 to 2811 kg m−3 with decreasing particle size. The measured settling velocities under laboratory conditions with no wind, <3.6 m s−1, are in agreement with the field velocities expected for particles with sizes <460 μm. The Ganser (1993) empirical model for particle settling velocity is the most consistent with our disdrometer settling velocity results. Converting disdrometer detected size into circle equivalent diameter shows similar PSDs between disdrometer measurements and G3 analyses. This validates volcanological applications of the disdrometer to monitor volcanic ash sizes and settling velocities in real-time with ideal field conditions. We discuss ideal conditions and the measurement limitations. In addition to providing sedimentation rates in-situ, calculated reflectivities can be compared with radar reflectivity measurements inside ash plumes to infer first-order ash plume concentrations. Detailed PSDs and shape parameters may be used to further refine radar-derived mass loading retrievals of the ash plumes.

The effect of electroslag remelting on the cleanliness of CrNiMoWMnV ultrahigh-strength steels

The cleanliness of ultrahigh-strength steels (UHSSs) without and with electroslag remelting (ESR) using a slag with the composition of 70% CaF2, 15% Al2O3, and 15% CaO was studied. Three experimental heats of UHSSs with different chemical compositions were designed, melted in an induction furnace, and refined using ESR. Cast ingots were forged at temperatures between 1100 and 950?C, air cooled, and their non-metallic inclusions (NMIs) were characterized using field emission scanning electron microscopy and laser scanning confocal microscopy. Thermodynamic calculations for the expected NMIs formed in the investigated steels with and without ESR were performed using FactSage 7.2 software while HSC Chemistry version 9.6.1 was used to calculate the standard Gibbs free energies (?G?). As a result of ESR the total impurity levels (TIL% = O% + N% + S%) and NMI contents decreased by as much as 46 % and 62 %, respectively. The NMIs were classified into four major classes: oxides, sulphides, nitrides, and complex multiphase inclusions. ESR brings about large changes in the area percentages, number densities, maximum equivalent circle diameters, and the chemical composition of the various NMIs. Most MnS inclusions were removed although some were re-precipitated on oxide or nitride inclusions leading to multiphase inclusions with an oxide or nitride core surrounded by sulphide, e.g. (MnS.Al2O3) and (MnS. TiN). Also, some sulphides are modified by Ca forming (CaMn)S and CaS.Al2O3. Some nitrides like TiN and (TiV)N are nucleated and precipitated during the solidification phase. Al2O3 inclusions were formed as a result of the addition of Al as a deoxidant to the ESR slag to prevent penetration of oxygen to the molten steel.

Microstructural analysis of undoped and moderately Sc-doped TiO2 anatase nanoparticles using Scherrer equation and Debye function analysis

UV light sensitive undoped and moderate (4 at.%) Sc-doped anatase nanocrystallites were prepared by an efficient and environmentally benign method based on homogeneous hydrolysis of TiOSO4 and Sc2(C2O4)3.5H2O aqueous solutions using urea as a precipitation agent, without post-synthesis calcination or annealing.X-ray diffraction study of the obtained powders revealed single phase anatase in both samples. Two different methods were applied to estimate the anatase crystallite size and shape from the X-ray diffraction data. The first one is based on the more conventional Scherrer equation (as implanted in GSAS-II program) while the second one is based on Debye function analysis (as implanted in DUBUSSY suite version 2.2), which is considered to be more adequate for nanocrystallites. Although each program has its own shape models, both methods indicated similar results of elongated nanocrystallite geometry for Sc-doped TiO2: (i) GSAS-II confirmed ellipsoid shape with equatorial size of 5.1(0) nm and axial size of 6.8(0), (ii) DEBUSSY suite 2.2 showed cylinder shape with diameter of equivalent circle in the ab-plane, Dab = 4.9(1.0) nm and crystallite length along the c-axis, Lc = 5.4(3.2) nm. For the undoped TiO2 sample, equatorial size of 5.5(0) nm and axial size of 7.3(0) nm for the ellipsoid shape was determined according to GSAS-II, while Dab = 5.5(1.3) nm and Lc = 6.0(2.2) nm for the cylinder shape was determined by DEBUSSY suite 2.2. These outcomes were found to corroborate with HRTEM analysis.Doping with 4 at.% Sc caused ~0.3% growth of lattice parameters from a = 3.7979 [4] Å, c = 9.4995 [9] Å for the undoped sample to a = 3.8110 [7] Å, c = 9.5274 [16] Å for the moderately Sc doped sample, while reduction in the Ti vacancies by half was confirmed by both methods.The introducing of Sc as electronically active secondary species into the crystal lattice of TiO2 can greatly alter its optical absorption. The incorporation of Sc into the crystal lattice of TiO2 favors the substitution of Ti, as both have approximately the same ionic size, and generates surface oxygen vacancies which can act as trapping center for the photogenerated electrons and reduce the recombination of electron–hole pairs. We can expect Sc doped TiO2 nanomaterials to have applications as effective photocatalysts for selective photocatalytic oxidation of various environmental organic pollutants.

Conventional Ultra-high Molecular Weight Polyethylene versus Highly Cross-linked Polyethylene from Semi-constrained, Fixed-bearing Total Ankle Arthroplasty Systems

Category: Ankle Arthritis Introduction/Purpose: The aim of this study was to compare the polyethylene wear rate, particle size, and particle shape of primary semi-constrained, fixed-bearing, bone-sparing total ankle arthroplasty using conventional ultra-high molecular weight polyethylene (CPE) versus highly cross-linked polyethylene (HXLPE) by applying a level walking input using a joint simulator. Methods: Two fixed-bearing total ankle replacement systems with different types of polyethylene liners were tested: 1.) CPE sterilized in ethylene oxide, and 2.) HXLPE sterilized with gas plasma after electron beam irradiation. Three implants for each design underwent wear testing using gravimetric analysis over 5 million simulated walking cycles. A fourth implant was used as a load soak control. Equivalent circle diameter (ECD) and equivalent shape ratio (ESR) were computed to determine particle size and particle shape, respectively. Results: The mean wear rate from 1.5-5 million cycles (MC) was 2.0±0.3mg/MC for HXLPE and 16.7±1.3mg/MC for CPE (P &lt; 0.001). The total number of particles per cycle generated for HXLPE and CPE were 0.17x106 particles/cycle and 0.53x106 particles/cycle, respectively (P &lt; 0.001). The mean ECD of HXLPE particles (0.22 ±0.11μm) was significantly smaller than the mean ECD of CPE particles (0.32±0.14μm) (P&lt;0.001). HXLPE particles were significantly more round than CPE particles (P&lt;0.001). Conclusion: HXLPE liners had a significantly lower wear rate and produced significantly fewer and rounder particles than CPE liners. The results of this study suggest that HXLPE has more favorable wear characteristics for total ankle arthroplasty.

Quantification of particle shape by an automated image analysis system: a case study in natural sediment samples from extreme climates

Sediment particle shape and microtexture are key parameters utilized for characterizing sediment transport and weathering (both physical and chemical) processes, which in turn are governed by environmental conditions such as climate. Assessing particle shape often involves either qualitative descriptors or time-consuming measurements of shape parameters by a human operator. This study employs a state-of-the-art, quantitative shape analysis instrument known as the “Morphologi G3” from Malvern Instruments, an automated microscope system capable of determining quantitative shape parameters via static image analysis of > 1000 particles in less than two hours. This instrument captures 2D projected images of particles and provides information on grain size measurements such as circle-equivalent diameter, length, width, perimeter, and area, as well as shape parameters such as circularity and convexity. As a case study, we conducted analyses on mud- and sand-sized particles collected from fluvial/alluvial systems of end-member climates to assess variations in sediment particle morphology potentially related to climate and/or transport distance and processes. Sediment samples were collected from fluvial systems in four contrasting climates: hot-arid (southeastern California, USA), hot-humid (eastern Puerto Rico), glacial-arid (proglacial stream of the Dry Valleys, Antarctica), and glacial-humid (Austerdalen proglacial stream, Norway). Results provide quantitative constraints on shape differences that relate to climate and transport, even for very fine-grained sand and mud size fractions. Comparison of the circularity of sediment particles from the four end-member climates indicates that the very fine sand fractions reflect differential physical abrasion and transport processes, whereas the morphology of the mud fraction seemingly imprints chemical weathering processes. We conclude that this new technique has great potential to further document impacts of climate on particle shape with applications to both modern and deep-time depositional systems.

Microstructural characterization of SiO2/Ni nanocomposites electrodeposited from a sulphate bath modified by PEI

SiO2/Ni nanocomposite coatings containing well-dispersed SiO2 nanoparticles were electrodeposited from a sulphate bath with and without the addition of polyethylenimine (PEI) as a cationic surfactant. The surface morphology and microstructure in the cross-sections of the deposited nanocomposites were examined by scanning electron microscopy. More detailed microstructure characterization was performed using transmission, scanning-transmission and high resolution transmission electron microscopy. It was determined that the addition of 0.05 g/L and 0.1 g/L of PEI allows the incorporation of SiO2 nanoparticles in the nickel matrix to be increased in comparison with the nanocomposite deposited without a surfactant. Based on high spatial resolution microanalysis, performed using high count rate energy dispersive spectroscopy of characteristic X-rays in the scanning-transmission mode, the distribution of SiO2 nanoparticles in the nanocomposite was visualized on elemental maps. Image analysis of the electron microscopy images enabled the mean equivalent circle diameters of grains in the nickel matrix to be determined, together with the volume fraction of SiO2 nanoparticles in the nanocomposites. The volume fraction of SiO2 clusters in the SiO2/Ni + PEI nanocomposites with the addition of 0.05 g/L and 0.1 g/L of PEI is equal to 18.4% and 13.3%, respectively. Furthermore, the PEI addition allows the nickel grain size in the matrix to be reduced. The combination of different imaging techniques confirmed that PEI is not only present as a surfactant in the electrolytic bath, but also incorporates into the microstructure of the nanocomposite. Nanocomposites electrodeposited in the presence of 0.05 g/L of PEI exhibit higher hardness, good tribological properties and improved corrosion resistance. Although increasing the PEI concentration in the bath up to 0.1 g/L strongly promotes grain size reduction and increase of the SiO2 volume fraction, it also causes an increase in the PEI fraction embedded in the microstructure, which results in deterioration of the properties of the SiO2/Ni + PEI nanocomposites.

Fabrication of FeAl Intermetallic Foams by Tartaric Acid-Assisted Self-Propagating High-Temperature Synthesis.

Iron aluminides are intermetallics with interesting applications in porous form thanks to their mechanical and corrosion resistance properties. However, making porous forms of these materials is not easy due to their high melting points. We formed FeAl foams by elemental iron and aluminum powders sintering with tartaric acid additive. Tartaric acid worked as an in situ gas-releasing agent during the self-propagating high-temperature synthesis of FeAl intermetallic alloy, which was confirmed by X-ray diffraction measurements. The porosity of the formed foams was up to 36 ± 4%. In the core of the sample, the average equivalent circle diameter was found to be 47 ± 20 µm, while on the surface, it was 35 ± 16 µm; thus, the spread of the pore size was smaller than reported previously. To investigate functional applications of the formed FeAl foam, the pressure drop of air during penetration of the foam was examined. It was found that increased porosity of the material increased the flow of the air through the metallic foam.

Mechanical tests, wear simulation and wear particle analysis of carbon-based nanomultilayer coatings on Ti6Al4V alloys as hip prostheses.

Carbon-based nanomultilayer coatings were deposited on medical-grade Ti6Al4V alloy using a magnetron sputtering technique under a graded bias voltage. The mechanical properties of the nanomultilayer coatings were investigated by nanoindentation, Rockwell and scratch tests as well as a ball-on-disk tribometer. The biological properties related to the immunological response of the coatings were investigated by wear simulation and wear particles analysis. Wear simulation was done according to ISO 14242, wear particles were analysed according to ISO 17853, and then compared with CoCr femoral heads. The results revealed that the carbon-based nanomultilayer coatings showed a multilayer structure, with a hardness of ∼20 GPa, an elastic modulus of ∼175 GPa, an adhesion higher than 80 N, and a low average coefficient of friction of 0.1. The average gravimetric wear rate of the polyethylene cups between the coated and CoCr groups had no statistical difference (P = 0.098). The average equivalent circle diameter of particles produced in the coated group was larger than that in CoCr (P = 0.001), but the proportion of submicron particles and globular/circular particles was not significantly different between the two groups (P > 0.05). Results showed lower Co/Cr ion contamination in the coated group. Hence, the carbon-based nanomultilayer coating on Ti6Al4V has good mechanical and tribological properties, releases fewer harmful metal ions and would not cause a more intense immunological host response than a CoCr prosthesis. The newly designed a-C nanomultilayer coatings are expected to prolong the longevity of artificial hip joints.