Backscattered Electron Mode Research Articles

Morphological aspects and distribution of granules composed of deproteinized bovine bone or human dentin into a putty mixture: an in vitro study

ObjectiveThe main aim of this study was to evaluate the morphological aspects and distribution of granules composed of deproteinized bovine bone mineral (DBBM) and human dentin-derived bone graft (HDBG) into a putty consistency mixture.Materials and methodsDBBM or HDBG were mixed with an alginate-based hydrogel at two different granule/hydrogel ratio (1:1 and 1:3) and divided into four test groups while two control groups were composed of DBBM or HDBG free of hydrogel. Groups of specimens were cross-sectioned for morphological evaluation by scanning electron microscopy (SEM) at backscattered electrons mode. Details on the dimensions and pores’ size of DBBM and HDBG were evaluated after mixing different amounts of particles and alginate-based hydrogels.ResultsMicroscopic analyses revealed a size of DBBM granules ranging from 750 up to 1600 μm while HDBG particles showed particle size ranging from 375 up to 1500 μm. No statistical differences were identified regarding the size of granules (p > 0.5). The mean values of pores’ size of DBBM particles were noticed at around 400 μm while HDBG particles revealed micro-scale pores of around 1–3 μm promoted by the dentin tubules (p < 0.05). The lowest distance between particles was at 125 μm for HDBG and 250 μm for DBBM when the particle content was increased. On decreasing the particles’ content, the distance between particles was larger for DBBM (~ 1000 μm) and HDBG (~ 1100 μm). In fact, statistically significant differences were found when the content of granules increased (p < 0.05).ConclusionsThe increased content of bioactive ceramic granules in a putty consistency mixture with hydrogel decreased the space among granules that can promote a high ceramic density and stimulate the bone growth over the healing process. Macro-scale pores on bovine bone mineral granules stimulate the formation of blood vessels and cell migration while the micro-scale pores of dentin-derived granules are proper for the adsorption of proteins and growth of osteogenic cells on the bone healing process.Clinical significanceA high amount of bioactive ceramic granules should be considered when mixing with hydrogels as a putty material since that result in small spaces among granules maintaining the bone volume over the bone healing process. Deproteinized bovine bone mineral granules have macro-scale pores providing an enhanced angiogenesis while dentin-derived granules possess only micro-scale pores for the adsorption of proteins and proliferation of osteogenic cells on the bone healing process. Further studies should evaluate the combination of different bioactive ceramic materials for enhanced bone healing.

Pentlandite and its alteration products in serpentinites of the Itkulsky ultrabasic massif (Southern Urals)

The relevance of the work is due to the need to study the mineralogy of the only indigenous manifestation of jewelry olivine within the Ural region. The purpose of the work is to study pentlandite and the products of its supergene alteration in serpentinites of the Itkulsky ultrabasic massif in the Southern Urals. Research methodology. The composition of some minerals was analyzed using a scanning electron microscope JSM6390LV from Jeol with an energy dispersive attachment INCA Energy 450 X-Max 80 from Oxford Instruments (analyst L. V. Leonova). The same instrument was used to obtain images of minerals in BSE (back-scattered electron) mode. X-ray structural study of minerals was carried out on an XRD-7000 X-ray diffractometer from Shimadzu with polycapillary optics and a high-temperature attachment NTK-1200N from Anton Paar for operation in the temperature range 25–1500 °C (analyst O. L. Galakhova). Conditions: copper radiation, V = 40 kV, I = 30 mA, step size – 0.02°. Results. Pentlandite is the main sulfide mineral of antigorite serpentinites; it is characterized by a fairly pure chemical composition; the only impurities in the mineral are cobalt (from 0 to 1.18 wt. %). According to the Ni/Fe ratio, the sulfide belongs to nickel and pentlandite proper. Smythite replaces pentlandite grains along the cracks and at the edges. Chemical composition, wt. %: S – 40.81; Fe – 37.65; Co – 1.66; Ni – 19.87, well calculated for the crystal chemical formula of smythite – (Fe5.83Ni2.93Co0.24)9.00S11.00. Cronstedtite replaces the pentlandite matrix in the form of veined segregations. It is distinguished by its chemical composition: SiO2 – 17,82; Fe2 O3 – 40,00; NiO – 11,02; FeO – 18,06; MnO – 0,57; MgO – 2,23; CaO – 1,30; H2 O – 9,00 (by difference in accordance with the standard), which is calculated based on the crystal chemical formula of Ni-Mg-bearing cronstedtite – (Fe2+ 0.95Ni0.71Mg0.21Ca0.09Mn0.03)1.99Fe3+ 1.01[(Si1.12Fe3+ 0.88)2.00O5 ](OH)3.80. Conclusions. Pentlandite from antigorite serpentinites of the Itkulsky ultrabasic massif (Southern Urals) was studied. Under the influence of weathering processes, most of the pentlandite grains were partially replaced by secondary sulfide – smythite and ferruginous serpentine – cronstedtite.

Wear Reduction in Heavily Loaded Units of Transport Vehicles

Introduction. The pivot assembly provides connection between the rotating and non-rotating parts of machines and mechanisms such as cranes, excavators, trailers, railway rolling stocks. In relation to rolling stock, it connects the load-carrying part of the car with the bogie and is one of the most critical and wear-out friction units. Its technical condition affects the intensity and form of wear of the surfaces themselves, the amount of resistance to rotation of the bogie when the car moves in curved sections of the track, the amplitude of the lateral rocking of the car, the intensity of wear of the wheel flanges and, as a consequence, the safety of operation of the rolling stock as a whole. Until now, periodic grease is used for this unit, which, even with a short mileage, manages to be squeezed out of the contact zones and, thereby, creates conditions for the predominance of dry friction. Until now, various proposals to solve this problem have not found application in mass production for a number of reasons, and therefore the search for ways to reduce wear in the pivot assembly of cars is still relevant. This study proposes a solution to this problem that does not require structural changes to the pivot assembly itself. The aim of this work was to develop a technologically advanced anti-friction coating with good adhesion, which will be applied to the surface of a replaceable disk installed between the rubbing surfaces of the pivot assembly during scheduled repairs of the car chassis. This approach will reduce the friction force and wear rate in the unit when lubrication shortage occurs due to squeezing out of the grease. Materials and Methods. Antifriction characteristics of the developed coating was observed on a friction machine providing specific loads on the test sample up to 5000 N and a sliding speed from 0.13 m/s. The samples were examined by scanning electron microscopy (FEI Quanta 200 microscope). SEM images were acquired in a back-scattered electron (BSE) mode using a semiconductor detector. To analyze the elemental composition of beam samples, an energy dispersive spectrometer (EDAX Element EDS system) was used. Results. A three-layer functional phosphorus-containing composite coating of the surfaces of the unit was developed, which made it possible to significantly reduce the coefficient of friction and, as a consequence, the intensity of wear of the pivot unit surface during dry friction. The optimal conditions for obtaining composite coating layers were determined. The influence of the thickness of each layer and the conditions for its production on its functional characteristics was studied. Discussion and Conclusion. The proposed solution is manufacturable and, with appropriate adaptation, can be used to reduce wear in any open pivot assembly without radically changing its design. The methods for producing coating layers are accessible and technologically advanced for serial use.

Вarothermic treatment of TixZr1-xC mixed carbides produced by MA-SHS consolidation

High density TixZr1-xC (x = 0.15; 0.24; 0.49; 0.88; 0.92) mixed alloys with a submicron structure have been successfully produced by MA-SHS under pressure followed by barothermic treatment (HIP) in a gas-static chamber. The effect of mechanical activation (MA) on the properties of reaction blends containing titanium, zirconium and carbon black powders, the formation of phase composition and microstructure, and the physical and mechanical properties of the alloys were investigated by means of X-ray diffraction (XRD) and backscattered electron mode (BSE). It was shown that the MA of the reaction blends in hexane for 40–60 min resulted in the amorphization of the metal particles and the formation of the carbide phase crystallites in them. TixZr1-xC mixed alloys produced by MA-SHS and aged at 1600 °C. The resulting TixZr1-xC mixed alloys are characterized by grain sizes of 0.1 μm, relative density of 99.2 %, microhardness (HV) of 20.9 GPa and a fracture toughness (K1c) of 12.53 MPa × m1/2. It has been shown that during ageing of the SHS alloy, the high temperature Ti0.49Zr0.51C phase completely decomposes into the daughter phases Ti0.15Zr0.85C and Ti0.92Zr0.08C. The characteristics of the alloys produced by the SPS and SHS methods are discussed.

Fleas and lesions in armadillo osteoderms.

Armadillos are bitten by several species of flea. Females of the genus Tunga penetrate the epidermis and when in place are fertilised by males, after which the abdomen swells enormously to form a 'neosome'. Within the penetrans group, T. perforans, makes lesions that perforate the osteoderms within the integument to form ~3 mm diameter cavities occupied by a discoid neosome. We examined these lesions in carapace material from animals which had died in the wild to see whether we could recruit evidence as to how they may be generated, either by the insect or by the host. We studied one species without such lesions, the nine-banded armadillo Dasypus novemcinctus, and two species with, the greater hairy armadillo Chaetophractus villosus and the southern three-banded armadillo Tolypeutes matacus, both showing the characteristic 'flea bite' holes in the external surfaces of the osteoderms. Samples were studied by three-dimensional backscattered electron mode scanning electron microscopy and X-ray microtomography. Both methods showed resorption pit complexes in the external surfaces of the osteoderms characteristic of those made by osteoclasts in active bone resorption. Lesions involved both the syndesmoses (sutures) between adjacent bones and the central regions of the osteoderms. Many lesions showed extensive repair by infilling with new bone. We conclude that the T. perforans neosome creates a local host response which causes bone resorption, creating the space in which it can grow.

Evaluation the Solubility and the Porosity of the Nano Fast Cement Comparing to the Mineral Trioxide Aggregate: An in vitro Study.

New calcium silicate base cements are introduced as root repair materials in order to defeat the problems of early root repair materials. Their mechanical properties such as solubility and porosity should be concerned. This study was conducted to evaluate the solubility and porosity of the NanoFastCement (NFC) as a new calcium silicate base cement comparing to mineral trioxide aggregate (MTA). In this in vitro study, scanning electron microscope (SEM) was used to evaluate the porosity at five different magnifications (200×, 1000×, 4000×, 6000× and 10000×) in secondary backscattered electron mode. All analyses were performed at 20kV. The obtained images were subjected to qualitative evaluation regarding the porosity. Solubility was determined following the international standards organization (ISO) 6876 method. Twelve specimens in specially fabricated stainless steel ring molds were weighed, initially and after 24 hour and 28 days of immersion in distilled water. Each weight was measured three times to record the average weight. Solubility was measured by calculating the difference of the initial and final weight. Solubility of the NFC in comparison with MTA showed no statistical difference (p Value > 0.05) after one day and 28 days. NFC acted like MTA and showed an acceptable solubility value at exposure time intervals. In both groups, solubility increased as time went on (p Value<0.05). The porosity of NFC was comparable to MTA, and NFC presented a less porous and a slightly smoother surface compared to MTA. NFC has similar solubility and porosity to Proroot MTA. Therefore, it can be a good, more available and less expensive substitute for MTA.

Clarification of Photoelectrochemical Oxygen Evolution Sites in TiO2 Nanotube Array Electrodes by PbO2 Deposition Method

TiO2 nanotube (TNT) photoanodes exhibit activity and stability for the oxygen evolution reaction (OER) by photoelectrochemical water oxidation. However, the location of the OER site by the photogenerated holes has not been clarified for the TNT photoanodes, unlike well-studied macrocrystalline photocatalysts. In this study, we performed reactions of TNT photoanodes in a 0.1 M Pb(NO3)2 under UV irradiation. The photoelectrochemically deposited PbO2 particles were observed through scanning electron microscopy in the backscattered electron mode. We found that β-PbO2 was deposited on the nanotubes with photocurrent decay and that the reaction site was located on the upper part (∼1 μm) of the TNT array with ∼3 μm length. The photocurrent decay implies the selective deposition of PbO2 on the catalytic site for water oxidation. The PbO2 nanoparticles were deposited on the inner and outer surfaces of the tube walls. This result is consistent with the mechanism of charge separation at the space charge layers formed on both surfaces of the walls. We also confirmed that the OER site changes depending on the wavelength of the incident light due to the change in the light penetration depth.

Synthesis of lanthanum(III)-containing heteropoly compounds with a Peacock-Weakley type anion from aqueous-organic solutions

Conditions necessary for the formation of La(III)-containing polyoxotungstates in solutions of the system Na2WO4 – HNO3 – La(NO3)3 – H2O/Solvent (Solvent = acetone, acetonitrile, ethanol; 50/50 vol.% Н2О: Solvent ratio) acidified to acidity Z = ν(H+)/ν(WO42–) = 0.80 were elaborated. It was established that during salting out, the addition of an organic solvent leads to the crystallization of normal salts, Na9[La(W5O18)2]·nH2O (n = 32–35). Using FT-IR spectroscopy, it was shown that the anion [La(W5O18)2]9– in the composition of the isolated salts belongs to the Peacock–Weakley type of structure and the absence of solvent molecules in the composition of the crystalline product was established. Using the method of scanning electron microscopy, the single-phase nature of the synthesized salts was established (according to the uniform contrast of the surface of the samples during scanning in the backscattered electron mode and according to the results of energy dispersive X-ray microanalysis), and the grain sizes were determined (from 140–300 nm for the salt isolated from the H2O: acetone medium, to 300–450 nm for the salt isolated from the H2O: ethanol system). Microphotographs of powders of Na9[La(W5O18)2]·nH2O salts powders in characteristic X-ray emission do not show zones with different surface morphology, and demonstrate uniform distributions of Na, La, W, and O without segregation, which confirms the single–phase nature of the samples isolated from aqueous-organic solutions. The conducted research made it possible to expand the list of organic solvents that can be used for the synthesis of normal salts with a heteropoly anion with a Peacock–Weakley type of structure from aqueous-organic solutions. The use of acetonitrile and ethanol for Na9[La(W5O18)2 ]·nH2O isolating can be extended to the synthesis of salts with other lanthanide heteroatoms.

3D Imaging of Roadside and Underground Railway Particulate Matter Structures

Air pollution in cities is associated with adverse health conditions; however, the underlying reasons are poorly understood. Previous particulate matter (PM) imaging studies have mostly used 2D microscopic techniques. In this study, the 3D appearances of roadside and underground railway station airborne PMs and the elemental characteristics of underground station PM were examined. Roadside and underground station PMs were collected using a cyclone particulate matter collection system. The 3D structures of the PMs were examined using an Olympus LEXT OLS4100 confocal microscope. Elemental characteristics of underground railway station PM were evaluated with a Zeiss EVO 50 scanning electron microscope (SEM) in backscattered electron (BSE) mode. Confocal microscopy of both PM sources indicated some particles can have sharp appearing edges. The longest axis length of roadside particles had a median (range) of 4.0 (1.3 to 6.6) μm and height of 1.4 (0.3 to 2.1) μm. SEM imaging of underground railway station PM was consistent in appearance and size with confocal imaging; BSE mode indicated compositions primarily of iron, calcium, and silicon. In conclusion, we observed that some roadside and underground railway station PMs can have sharp appearing surfaces from 3D confocal microscopy. SEM imaging of underground railway station PM was consistent with confocal microscopy and enabled elemental analysis.

Laser powder bed fusion (LPBF) of NiTi alloy using elemental powders: the influence of remelting on printability and microstructure

PurposeThe purpose of this paper is to investigate the effect of remelting each layer on the homogeneity of nickel-titanium (NiTi) parts fabricated from elemental nickel and titanium powders using laser powder bed fusion (LPBF). In addition, the influence of manufacturing parameters and different melting strategies, including multiple cycles of remelting, on printability and macro defects, such as pore and crack formation, have been investigated.Design/methodology/approachAn LPBF process was used to manufacture NiTi alloy from elementally blended powders and was evaluated with the use of a remelting scanning strategy to improve the homogeneity of fabricated specimens. Furthermore, both single melt and up to two remeltings were used.FindingsThe results indicate that remelting can be beneficial for density improvement as well as chemical and phase composition homogenization. Backscattered electron mode in scanning electron microscope showed a reduction in the presence of unmixed Ni and Ti elemental powders in response to increasing the number of remelts. The microhardness values of NiTi parts for the different numbers of melts studied were similar and ranged from 487 to 495 HV. Nevertheless, it was observed that measurement error decreases as the number of remelts increases, suggesting an increase in chemical and phase composition homogeneity. However, X-ray diffraction analysis revealed the presence of multiple phases regardless of the number of melt runs.Originality/valueFor the first time, to the best of the authors’ knowledge, elementally blended NiTi powders were fabricated via LPBF using remelting scanning strategies.

Discussion on the presence condition of suboxide ZrO beneath the oxide in zirconium alloys

Characteristics related to the oxide-metal interface of oxidized (corroded) zirconium alloys in an autoclave have been extensively explored using both experimental and theoretical methods during the last ten years. A thin intermediate or suboxide layer with an approximate 1:1 ZrO stoichiometry was observed at the oxide-metal interface in several zirconium alloys. Through investigating its chemical composition, morphology, grain size and orientation relationship with the substrate α-Zr, some researchers assumed that the suboxide layer is related to the oxidation (corrosion) rate, whereas others did not. The majority of earlier studies used aqueous corrosion samples that were exposed to high pressure and low temperature, simulating in-service conditions. However, the interfacial characteristics at higher temperature have been scarcely reported. In this study, we focused on the microstructure and micro-chemistry of the oxide and suboxide ZrO in Zircaloy-4 and Zr-1.0Nb-0.01Cu oxidized at 650–1000 °C by combining Backscattered Electron (BSE) mode in Scanning Electron Microscope (SEM), Transmission Electron Backscatter Diffraction (t-EBSD) and (Scanning) Transmission Electron Microscope fitted with an Energy Dispersive X-ray Spectroscope ((S)TEM-EDS). The results show that the suboxide ZrO in oxidized Zircaloy-4 and Zr-1.0Nb-0.01Cu alloys has different morphologies. With increasing oxidation temperature, the suboxide ZrO distribution varies significantly, from a continuous layer to a few occasional blocky grains, until any ZrO grains are undetectable at the ZrO2/α-Zr(O) interface. The hexagonal crystallographic structure of ZrO has also been confirmed. According to discussions combining our investigations and earlier reports, the presence of suboxide ZrO and their morphology are probably related to the oxidation temperature, chemical composition of alloys and complex stress accumulation adjacent to the interfacial region.

Periarticular calcifications containing giant pseudo-crystals of francolite in skeletal fluorosis from 1,1-difluoroethane "huffing".

Inhalant use disorder is a psychiatric condition characterized by repeated deliberate inhalation from among a broad range of household and industrial chemical products with the intention of producing psychoactive effects. In addition to acute intoxication, prolonged inhalation of fluorinated compounds can cause skeletal fluorosis (SF). We report a young woman referred for hypophosphatasemia and carrying a heterozygous ALPL gene variant (c.457T>C, p.Trp153Arg) associated with hypophosphatasia, the heritable metabolic bone disease featuring impaired skeletal mineralization, who instead suffered from SF. Manifestations of her SF included recurrent articular pain, axial osteosclerosis, elevated bone mineral density, maxillary exostoses, and multifocal periarticular calcifications. SF was suspected when a long history was discovered of 'huffing' a computer cleaner containing 1,1-difluoroethane. Investigation revealed markedly elevated serum and urine levels of F-. Histopathology and imaging techniques including backscattered electron mode scanning electron microscopy, X-ray microtomography, energy dispersive and wavelength dispersive X-ray emission microanalysis, and polarized light microscopy revealed that her periarticular calcifications were dystrophic deposition of giant pseudo-crystals of francolite, a carbonate-rich fluorapatite. Identifying unusual circumstances of F- exposure is key for diagnosing non-endemic SF. Increased awareness of the disorder can be lifesaving.

Hardness and tribological properties of electrodeposited Ni–P multilayer coatings fabricated through a stirring time-controlled technique

Ni–P multilayer coatings were deposited on the surfaces of low-carbon steel by direct current electrodeposition through a stirring-time controlled technique (STT). The microstructure, hardness, friction coefficient and wear properties of the deposits were investigated. Scanning electron microscopy (SEM) in back-scattered electron mode revealed multilayer structures of Ni–P coatings fabricated by repeatedly turning the magnetic stirrer in the bath on and off. Energy dispersive X-ray spectroscopy (EDS) was employed to quantitatively compare the P content in the alternating layers. The hardness of the Ni–P multilayer coatings was found to be significantly greater than that of monolithic Ni–P coatings. A maximum hardness value of 580 ± 8.7 HV0.1 was found in the sample prepared using the on- and off-stirring periods of 8 and 15 min, respectively. This showed an increased hardness of 20.1% from that of sample prepared with the stirrer turned off. The Ni–P multilayer coatings prepared by STT also had superior wear resistance to that of monolithic Ni–P coatings.

High-temperature PEM fuel cell electrode catalyst layers part 1: Microstructure reconstructed using FIB-SEM tomography and its calculated effective transport properties

The main topic of this study is the microstructure of catalyst layers (CLs) of a high-temperature gas diffusion electrode in a PEM fuel cell, bonded by polybenzimidazole. Using focused ion beam scanning electron microscopy in both the secondary and backscattered electron modes, Pt distribution in the CLs was studied. It was found that the choice of binder and preparation history had an important impact on the CL 3D microstructures. Polybenzimidazole-bonded CLs exhibited smooth surface, low porosity and homogeneous distribution of Pt. On the other hand, penetration of Pt into the microporous layer of the electrode was observed. Good thermal and mechanical stability of the CL made it possible to carry out FIB-SEM tomography and to reproduce its 3D microstructure by alternating use of ion milling and imaging of emerging cross-sectional planes. The 3D microstructure obtained served as an input for mathematical models allowing an evaluation of the effective macroscopic transport properties of the CL. This represents important information for reliable mathematical modelling and optimisation of the high-temperature PEM fuel cell.

Thermal Aging Effects on Mechanical and Intergranular Corrosion Resistance of Super-Austenitic Stainless Steel exposed at 600˚C

Super-austenitic stainless steels (SASS) are alloys with better performance in industrial applications in comparison with standard degrees of austenitic stainless steels (ASS), mainly because of elevated Ni and Mo contents and residual control of certain elements because the improvement of refine techniques. These facts, promotes an improvement of mechanical properties and minimize detrimental effects of intergranular corrosion. Besides, some industrial applications involve high temperatures services, because these alloys families have an excellent creep and oxidation resistances performances. In this work, the objective is evaluate the microstructural and mechanical properties in high Mo SASS exposed at 600˚C in specimens aged until 2000 hours. Thus, hardness and toughness values and Double Loop Electrochemical Potentiodynamic Reactivation (DL-EPR) measurements were analyzed in several thermal aging in comparison to solution treatment condition. Complementary, analysis by Light Optical (LOM), of specimens tested by DL-EPR, and Scanning Electron Microscopies (SEM) in fractured surface from Charpy specimens were also analysed by SEM by backscattered electron mode (BSE). The results show that the aging provokes intergranular embrittlement by inhomogeneous distribution in grain boundaries of Mo rich phase precipitation.

Origin of surface ridging in Ti-6Al-4V sheets produced by pack rolling and its effect on microstructural and mechanical properties

Pack rolling is an effective process for manufacturing Ti-6Al-4V products, especially thin sheets; however, it tends to cause surface defects. Surface ridging is the most significant surface defect produced during the pack rolling of thin sheets. Hence, in this study, the effects of pack-rolling conditions on the origin of surface ridging on Ti–6Al–4V alloy surfaces were investigated using experimental and numerical techniques. Pack rolling was carried out at temperatures of 830, 860, 930, and 980 °C until a thickness reduction of up to 30 % was achieved. The surface ridging mechanism, microstructural evolution, and mechanical properties after pack rolling were studied using optical microscopy, scanning electron microscopy in the backscattered electron mode, microhardness tests, and the finite element method to identify the influence of pack-rolling parameters and the surface quality at various temperatures. The stress, strain, and temperature distributions after pack rolling at different temperatures revealed that the difference in the plastic flow between the core and cover resulting from the temperature rise was the mechanism controlling surface ridging on the surface of the Ti–6Al–4V plate. These results can be used for optimizing the pack-rolling processes of Ti-6Al-4V alloys.

Diversity and Colonization Strategies of Endolithic Cyanobacteria in the Cold Mountain Desert of Pamir.

Microorganisms can survive in extreme environments and oligotrophic habitats thanks to their specific adaptive capacity. Due to its severe and contrasting climate conditions, the cold mountain desert in Eastern Pamir provides a unique environment for analyzing microbial adaptation mechanisms occurring within colonization of endolithic habitats. This study aims to investigate the composition and structure of endolithic microbial communities and analyze the interactions between microorganisms and colonized lithic substrates. Endolithic biofilms were examined using scanning electron microscopy in backscattered electron mode (SEM-BSE) and next-generation sequencing (NGS) applying amplicon sequence variants (ASVs) approach. The investigation of the V3–V4 region of 16S rRNA gene revealed that endolithic communities are dominated by Actinobacteria (26%), Proteobacteria (23%), and Cyanobacteria (11.4%). Cyanobacteria were represented by Oxyphotobacteria with a predominance of subclasses of Oscillatoriophycidae, Synechococcophycideae, and Nostocophycidae as well as the rarely occurring Sericytochromatia. The positive correlation between the contribution of the orders Synechococcales and Rhizobiales to community structure suggests that some functionally closed taxa of Cyanobacteria and Proteobacteria can complement each other, for example, in nitrogen fixation in endolithic communities. The endolithic communities occurring in Eastern Pamir were identified as complex systems whose composition and structure seem to be influenced by the architecture of microhabitats and related microenvironmental conditions.

Local Porosity Measurement From Scanning Electron Microscopy Images in the Backscattered Electrons Mode.

We propose a method to measure the local porosity of porous samples from scanning electron microscopy images in the backscattered electron mode. The porous samples are impregnated with a polymer resin and observed in polished cross sections. Image intensities are calibrated with intensities from pure resin and the bulk phase. The calibration model is justified with Monte Carlo simulations on perfectly homogeneous virtual samples. Uncertainties in measured porosity are given as a function of uncertainties on physical properties of the resin and the bulk phase and on measured signals. The methodology is applied to a series of heterogeneous alumina catalyst supports with varying porosities. A good agreement is found between the averaged local porosity by scanning electron microscopy and global porosity determined by mercury intrusion porosimetry. The use of local porosity statistics allowed the quantitative characterization of the porosity fluctuations of these supports that appeared to be linked with their preparation parameters.

The Influence of Surface Dipping and Bulk Filling Agents on Properties of High-Speed Grinding Wheels: Materialographic-Based Numerical Modelling

In order to increase the peripheral speed of grinding wheels of size of Ø 500 × 18 × Ø 200 mm for precise hard metallic surface finishing from conventional 80 m.s-1 up to 138 m.s-1 while still ensuring their safety and reliability, the critical locations in the grinding wheel were evaluated using the finite element analysis. The microstructure of grinding wheel was revealed using the materialographic techniques and the scanning electron microscope images were recorded in the back-scattered electrons mode. The image analysis was used on recorded micrographs for separation of individual material components, i.e. an abrasive, a binder, and pores, and to extract their geometries and spatial relationships. Subsequently, the influence of different filling agents (Young's modulus of 5, 10, 20, and 40 GPa) was studied, considering both surface dipping and bulk filling treatments.

Microstructural and mechanical properties of Al-Cu functionally graded materials fabricated by powder metallurgy method

In the present work, four dissimilar-layered volume fraction of Al-Cu functionally graded materials were fabricated by using powder metallurgy. The volume fraction of Cu (0, 5, 10 and 15 wt%) powder mixture was hot pressed with a pressure of 400 MPa and sintered at 550 0C for 3 h as layer by layer. The mechanical and microstructural properties shows the material composition distribution of two-layered FGMs varies gradually. The properties such as density and hardness of FGMs was carried out in order to compare with homogeneous mixture of Non-FGM samples. A complete characterization of the microstructural graphs of FGMs achieved using Optical Microscope, Back scattered electron Mode, scanning electron microscopy and XRD analysis. The results shows an improved in micro-mechanical properties of the Al-Cu FGMs based on material selection and sintering temperature as well as dwell time.