Form Of Bulk Material Research Articles

Effect of manufacturing route on microstructure and micromechanical properties of AlCoCrFeNi high entropy alloy

The manufacturing route of a particular metallic alloy profoundly affects its microstructure, as well as mechanical properties. In that respect, the present research investigates the microstructure and microstructure-dependent mechanical properties of the AlCoCrFeNi high entropy alloy (HEA), that was manufactured via two different routes: (i) Atmospheric plasma spraying (APS) in the form of coating on a stainless steel subtract and (ii) vacuum arc melting (VAM) in the form of bulk material. AlCoCrFeNi HEA coating microstructure is composed of a solid solution (Ni) as a matrix, which contains different phases, as well as intermetallics and defects, such as splat boundaries. On the contrary, the microstructure of bulk AlCoCrFeNi HEA alloy is free from any secondary phases, and is homogeneous in nature, which consists of only the solid solution of Ni. The experimental results show that the strength of the bulk HEA (963.14 ± 28.58MPa of yield strength and 1005.58 ± 22.08MPa of compressive strength) is better than that of HEA coating (yield strength of 802.33 ± 43.76MPa and compressive strength of 817.73 ± 43.84MPa). The phase, as well as splat boundaries in the microstructure, are the ‘weakest link’ in the HEA coating, that serves as defect initiation site. As the bulk HEA alloy is free from these ‘weakest link’, thus, deformation of the material is guided through plastic flow of materials, in the terms of the barrelling effect.

Rhodium-decorated nanoconical nickel electrode synthesis and characterization as an electrochemical active cathodic material for hydrogen production

Noble metals in form of bulk materials are rarely used as catalysts in industrial applications due to their price and limited accessibility. However, the surface of commonly-used materials can be modified with an exceptionally low amount of platinoids to enhance their electrochemical activity.In this work, the surface of the free-standing nanoconical Ni structures was modified with a thin metallic rhodium layer with a spontaneous galvanic displacement process. It emerged that Rh-decorated Ni nanoconical electrodes exhibited higher catalytic activity in a model hydrogen evolution reaction in an alkaline environment in comparison to the unmodified electrode. Furthermore, the proposed synthesis protocol is high-speed and straightforward, making it promising in application on a semi and industrial scale. Linear Sweep Voltammetry measurements were used to test the catalytic activity in 1 M NaOH electrolyte. The nanoconical structures were highly-hydrophobic, what has been observed by dedicated camera-based equipment. In addition, the electrochemically-active surface area (ECSA) of tested electrodes were estimated and confirmed in atomic force microscope AFM measurements. The durability of coatings was tasted in 1 M NaOH for 14 days.

Сравнительная стойкость против кавитационной эрозии аустенитных сталей различного уровня метастабильности

Introduction. Reliability-critical components of equipment working in contact with high-speed liquid media (for example, turbine blades of hydroelectric power stations, pump impellers, ship propellers) are subjected to one of the types of wear – cavitation erosion. The current study aims to select and scientifically substantiate the type of coating and its structural-phase state for the effective protection of parts from cavitation erosion. Research methods. The study carries out a comparative analysis of differences in the cavitation erosion resistance of characteristic austenitic steels, in the form of bulk material (316L) and coatings (E308L, 60Cr8TiAl), used for protection against cavitation Arc surfacing, i.e. MMA and MIG, is used for depositing the coatings. The tests are carried out on an original installation for evaluating the cavitation resistance of materials with applying ultrasound and the electrical potential difference. Results and Discussion. The results show that the 60Cr8TiAl has a higher resistance to cavitation erosion than that of E308L and 316L by 4 and 10 times, respectively. The structural factors that determine the resistance to cavitation erosion damage are identified to analyze the reasons for the differences in material resistance. Firstly, a strong dependence of the cavitation erosion resistance of austenitic steels on the intensity of the deformation martensitic transformation, developing under the influence of cavitation, is confirmed. This structural transformation contributes to an increase in cavitation resistance of the surface layer. In metastable austenitic steel, a deformation martensite (α′) is formed in the surface layer during the initial test period. This causes an increase in hardness, dissipation of the energy of external action, and the appearance of compressive stresses that prevent the occurrence of microcracks. Subsequently, additional hardening of the previously formed dispersed crystals of α′-martensite occurs. In 60Cr8TiAl, these effects are significantly stronger than that of E308L and 316L due to the higher level of metastability of austenite and formation of carbon deformation martensite.

Technology Focus: High-Pressure/High-Temperature (March 2021)

For the past several months, the rig count in North America has been slowly but steadily improving and some pockets of deepwater operations are finally showing some activity, especially in Central and South America and Africa, where interesting discoveries continue. Arctic operations also are picking up, though not in North America, where a new administration in the US is bringing some uncertainty to upstream operations. Looking at leasing activity in 2020, however, the operators on federal land seem to have built up a backlog, so the immediate consequences of recent executive action seem not to be significant, though they do set an important precedent. More significant seems to be the opposition to pipelines, which are the most-efficient and safest way to transport any form of bulk material, be it gas, liquid, or slurry. Even if the most-stretched targets of an energy transition become reality, the need for pipeline transport will remain, and even increase, if the gas transported is biogas and hydrogen, where much larger volumes must be transported for the same calorific value of natural gas. In my tenure as a reviewer for JPT, I had refrained from a materials-focused special simply because high-pressure/high-temperature (HP/HT) conferences and sessions seem to be dominated by them and I wanted to demonstrate a wider spectrum of the challenges of HP/HT operations. With the energy transition leading to the possibility of free hydrogen being introduced into the energy system outside of established chemical feedstock installations (which are all low-pressure), this is a good time to remind our industry (and the outside world) that vast experience exists in the oil and gas industry on the interaction of hydrogen and metal (at very high pressures), a challenge that is still not completely understood and that is still a large cause of pressure-vessel failures (e.g., in refineries). Also, if carbon dioxide is intended to be captured and contained in metal vessels, another set of metallurgical challenges emerges. This Technology Focus looks at two papers from Asia, where these challenges were discovered and mitigated, and one paper from Gulf of Mexico deepwater operations. Many learnings can be taken from these papers, and extremely costly and safety-critical failures and loss of containment can be avoided. Addressing technical risk, thorough and detailed front-end engineering is a cost-effective and cost-saving activity, and this applies especially for front-end corrosion engineering and testing, as we have seen from several megaprojects in the past where this was not done to the extent finally understood to have been required. So, I invite you all to understand and embrace the fact that sound and competent engineering, as well as communicating learnings across functions and industries, is the key enabler for future success in our stressed industry, and to use our engineering brainpower and imagination to bring those HP/HT projects currently deemed too expensive to develop within the realm of the current oil-price environment.

Insecticide activity of bifenthrin nanoparticles synthesized by laser ablation of solids in liquids

Organic nanoparticles of bifenthrin (agricultural insecticide) were successfully synthesized by the laser ablation of solids in liquids (LASL) technique, using as liquid medium a solution of a polymeric surfactant at 0.1 %. The results showed that the use of the surfactant improves the stability of the organic nanoparticles 18 times as compared to those synthesized in water. The characterization by UV-Vis spectroscopy allowed evaluating the stability of colloids, as well as determining the concentration of nanoparticles in the medium. In the characterization by TEM and HRTEM was possible to observe nanoparticles with the most probable size of 5 nm and interplanar distances which correspond to the crystalline structure of the starting material. Mass coupled gas chromatography technique was used to corroborate the chemical composition of nanoparticles. Results of biological tests using Drosophila Melanogaster fly, showed that the use of the nanostructured compound is effective in lower doses than those used in agriculture in the form of bulk material.

Predicting microstructure evolution for friction stir extrusion using a cellular automaton method

Friction stir extrusion (FSE) offers a solid-phase synthesis method consolidating discrete metal chips or powders into bulk material form. In this study, an FSE machine tool with a central hole is driven at high rotational speed into the metal chips contained in a chamber, mechanically stirs and consolidates the work material. The softened consolidated material is extruded through the center hole of the tool, during which material microstructure undergoes significant transformation due to the intensive thermomechanical loadings. Discontinuous dynamic recrystallization is found to have played as the primary mechanism for microstructure evolution of pure magnesium chips during the FSE process. The complex thermomechanical loading during the process drives the microstructure evolution. A three-dimensional finite element process model is developed using commercial software DEFORM 11.0 to predict the thermal field, mechanical deformation and material flow during the FSE process. Using the simulated thermomechanical loadings as input, a cellular automaton model is developed to simulate the dynamic evolution of the material grain microstructure. The predicted grain size is in good agreement with the experimentally measured grain size. This numerical study provides a powerful analysis tool to simulate the microstructure transformation for friction stir-based processes.

Emergence of Nanoplastic in the Environment and Possible Impact on Human Health.

On account of environmental concerns, the fate and adverse effects of plastics have attracted considerable interest in the past few years. Recent studies have indicated the potential for fragmentation of plastic materials into nanoparticles, i.e., "nanoplastics," and their possible accumulation in the environment. Nanoparticles can show markedly different chemical and physical properties than their bulk material form. Therefore possible risks and hazards to the environment need to be considered and addressed. However, the fate and effect of nanoplastics in the (aquatic) environment has so far been little explored. In this review, we aim to provide an overview of the literature on this emerging topic, with an emphasis on the reported impacts of nanoplastics on human health, including the challenges involved in detecting plastics in a biological environment. We first discuss the possible sources of nanoplastics and their fates and effects in the environment and then describe the possible entry routes of these particles into the human body, as well as their uptake mechanisms at the cellular level. Since the potential risks of environmental nanoplastics to humans have not yet been extensively studied, we focus on studies demonstrating cell responses induced by polystyrene nanoparticles. In particular, the influence of particle size and surface chemistry are discussed, in order to understand the possible risks of nanoplastics for humans and provide recommendations for future studies.

Scaling relationship among indentation properties of electromagnetic materials at micro- and nanoscale

Electromagnetic materials have been widely employed in micro-functional devices. Using multi-field nanoindentation technique, we have investigated the local deformation behavior of various electromagnetic materials in the form of bulk materials, foils, and thin films under electric or magnetic field. Based on dimensional analysis and experimental data, a field tunable scaling relationship among hardness, reduced contact elastic modulus, and indentation work has been found. Furthermore, a method to determine the hardness and reduced modulus of electromagnetic materials is proposed, which avoids the error from estimating the indentation contact area. This work is meaningful for the characterization of mechanical properties and design of devices made of electromagnetic materials.

On the Damping Properties of a Polyurea Elastomer

The development of materials with high damping and energy absorption properties in the form of bulk materials or coatings is today a target for designing components and structures with improved durability and survivability to serve in fields such as aeronautical, mechanical, civil and environmental engineering. This paper presents the results of the dynamic mechanical characterization conducted on reinforced polyurea composites. The mechanical properties of two types of composite materials utilizing the polyurea elastomer as a matrix are compared with those of the pure polymer. The composite materials show a substantial increase of the damping ability. Such materials can be produced in the form of coatings and successfully applied for maximizing the damping of mechanical and structural vibrations or for limiting the damage effects of impact events on structures and components.

Surface-enhanced Raman scattering of SnO2bulk material and colloidal solutions

Surface-enhanced Raman scattering (SERS) effects on tin dioxide in the form of bulk material, nanostructured thin films, and colloidal solutions were investigated. Raman spectra are characterized by the three Raman scattering peaks at 478, 633, and 776 cm${}^{\ensuremath{-}1}$, assigned to the ${E}_{g}$, ${A}_{1g}$, and ${B}_{2g}$ modes, typical of rutile SnO${}_{2}$. In the presence of the silver nanoparticles, in addition to the enhancement intensity of some of the fundamental tin dioxide rutile Raman features, the appearance of a new Raman scattering peak at about 600 cm${}^{\ensuremath{-}1}$ is observed. These spectral features are observed, in the presence of silver nanoparticles, also in other SnO${}_{2}$-based systems such as pulsed laser deposited thin films, with different stoichiometry, and in water colloidal solutions. The observed SERS effects are explained in terms of electric field gradient mechanism that are generated near a metal surface. In particular, the appearance of a peak near 600 cm${}^{\ensuremath{-}1}$ is attributed to the Raman activation of the infrared ${E}_{u}$ transverse optical mode.

Ag Powders Consolidated by Reciprocating Extrusion (CEC)

CEC has unique characteristic. These are applicability of very large strain and deformation under high hydrostatic pressure. Due to these abilities of CEC, several unique phenomena have been observed. One of them is the possibility of consolidation of metallic powders in room temperature to the form of bulk material. In the present paper the consolidation of AgSnBi and AgNi to bulk composites was presented. Applying the deformation of  = 0.42 in the single cycle of CEC, under high hydrostatic pressure, the samples without pores and discontinuities were fabricated. The microstructure observations were performed by optical microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). They show refinement of microstructure at all levels of observation. The nanometric-size subgrains/grains were found inside consolidated granules. The microhardness level of AgSnBi in average achieved level 110 μHV100, and AgNi of about 90 μHV100. The AgSnBi samples consolidated by CEC and additional hydrostatically extruded to wires with 3 mm in diameter average showed 500 MPa yield point.

The Perovskite SrTiO3 on Si/SiO2 by Liquid Injection MOCVD

SrTiO3, which has a very high dielectric permittivity κ in the form of bulk material (κ ~ 300), has been considered as a potential candidate for the replacement of SiO2-based gate oxide in future CMOS transistors and as a promising dielectric for next generations of DRAM capacitors. Like all perovskite-type oxides, optimized properties require a stringent control of the composition and of the interfaces with the electrodes. Here, we address issues such as the stoichiometry control of the films synthesized by metal organic chemical vapor deposition and the interface engineering on Si/SiO2 through the precursor chemistry. The silicate layer formed at 700{degree sign}C can be minimized and even suppressed. The dielectric properties are discussed with respect to thickness and composition. Although the perovskite phase is obtained for a large range of Sr/Ti ratio in the films, optimal dielectric properties are obtained in a very narrow range for Sr-deficient films.

Synthesis and characterisation of carboxylate-terminated silica nanohybrid powders and thin films

Novel organic–inorganic hybrid materials, in the form of bulk materials (powders) and thin films, exhibiting carboxylate functionality have been prepared by sol–gel co-condensation of 11-(triethoxysilyl)methylundecanoate with tetraethoxysilane (TEOS), followed by chemical treatment with AlI3 to convert the ester moieties into terminal carboxylic acid sites. Uniform nanostructured thin films were prepared by spin-coating on silicon wafers. Both powders and thin films were used to study the uptake behaviour of lanthanide cations, such as Eu3+ or La3+ from aqueous solutions. It has been shown that the uptake capacity (mg g−1) of the films is 3–4 times higher than that of bulk (powder) materials. This has been attributed to the larger number of accessible COO−groups in the thin film form compared with the bulk material.

Bioceramics—A New Era

In the last few decades with the introduction of bioceramics, a special class of ceramics to perform tailored functional/biological/chemical activities in living systems, treatment procedure through reconstructive surgery has been revolutionized and this has resulted in marked improvement in quality of life of the rehabilitated persons. The procedure involves an innovative use of specially designed ceramics for reconstruction of diseased/damaged parts of body, e.g. hips, knees, wrists, spines, jaws, diseased long-bones and repair for maxillofacial, periodontal disease, etc. Bioceramics are produced in a variety of compositions, forms and phases and are often used in the form of bulk materials of specific shape to perform a special function, which are called implants, prostheses or prosthetic devices. They are also used in powder/granule forms to fill space of the damaged hard tissues, which through natural repair process get integrated and restore function, and as coatings to provide bio-friendly interface on substrate for cement-less fixation and sometimes also as a second phase in composites. In this review, different classes of bioceramics, their chemical compositions, structures, tailored functions and broad application areas have been outlined and the effects of their usage on treatment of different trauma/degenerative diseases have been discussed. Along with the current research status of the advanced laboratories around the world on this emerging subject, the developments made so far at CGCRI, Kolkata have also been outlined.

One-pot self-assembly of mesostructured silica films and membranes functionalised with fullerene derivativesElectronic supplementary information (ESI) available: selected analytical data of 2 and 3. See http://www.rsc.org/suppdata/jm/b4/b401916d/

Three fullerene derivatives have been employed with amphiphilic block copolymers both as structure-directing agents and doping molecules in one-pot synthesis of self-assembled 2D-hexagonal and cubic porous silica mesostructures, in the form of bulk materials, thick cast films and thin films through an evaporation-induced self-assembling procedure. Thermal calcination of the samples at 280 °C almost completely removed the block copolymer from the silica matrix without substantial loss of the fullerene additive, as demonstrated by FT-Raman spectra in which a clear signature of the fullerene Ag mode at 1467 cm−1 was still clearly observed. Upon irradiation with laser light at 632.8 nm, the fullerene-doped mesostructured materials exhibited photoluminescence at room temperature, which was not observed in the silica matrix.

Carbon-carbon composite bearing materials in hip arthroplasty: analysis of wear and biological response to wear debris.

Ultra-high molecular weight polyethylene wear particles have been implicated as the major cause of osteolysis, implant loosening and late aseptic failure in total hip arthroplasties in vivo. This study initially screened 22 carbon-carbon composite materials as alternatives for UHMWPE in joint bearings. New bearing materials should satisfy certain criteria--they should have good wear properties that at least match UHMWPE, and produce wear particles with low levels of cytotoxic and osteolytic activity. Initial screening was based on wear resistance determined in short-term tribological pin-on-plate tests. Three materials (HMU-PP(s), HMU-RC-P(s), and SMS-RC-P(s)) which had superior wear resistance were selected for long-term testing. All materials had very low wear factors and SMS-RC-P(s), which had a wear factor of 0.08 +/- 0.56 x 10(-7) mm3/Nm, was selected for the subsequent biological testing and particle size analysis. SMS-RC-P(s) showed good biocompatibility in bulk material form and also the wear particles had low cytotoxicity for L929 fibroblasts in culture compared to metal wear particles. Wear debris size analysis by transmission electron microscopy showed that the particles were very small, with the vast majority being under 100 nm in size, similar to metal wear particles. The potential osteolytic effect of SMS-RC-P(s) wear particles was investigated by culturing particles with human peripheral blood mononuclear cells and measuring TNFalpha production. SMS-RC-P(s) did not significantly stimulate TNFalpha production at a particle volume to cell number ratio of 80:1, indicating that the debris had a low osteolytic potential. The results of this study suggest that carbon-carbon composites, particularly those composed of PAN-based fibers may be important biomaterials in the development of next generation bearing surfaces for use in total joint replacements that have very low wear rates and reduced osteolytic and cytotoxic potential.

Polarization dependent X-ray absorption studies of the chemical bonds anisotropy in wurtzite GaN grown at different conditions

Polarization-dependent X-ray absorption spectroscopy was used to examine the influence of crystal growth techniques and substrates type on the bond lengths and the bond structure of the single crystalline, wurtzite GaN in a form of bulk materials and epitaxial layers. The layers were grown by molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) on different substrates such as SiC, sapphire and GaN. From the observed X-ray absorption near edge structure (XANES) of the Ga K-edges, it was found that MOCVD introduces a stronger disorder around Ga atoms than MBE. Comparing the Ga and N K-edges of the epilayers and the bulk crystal, we found a prevailing contribution of N-vacancies in the layers and dominance of Ga-vacancies in the bulk crystal. The bonds along the c-axis are less perfect than the bonds in the c-plane for all investigated epilayers. The performed standard extended X-ray absorption fine structure analysis (EXAFS) resulted in a direct estimate of the bond lengths in the c-plane and along the c-axis.

Oxide growth on evaporated thin film and bulk iron exposed to humid air and HCl or HNO 3 vapours

High purity iron was used in the form of thin films evaporated on glass and in the form of bulk material. Evaporated films exhibited a geometrical pattern with rectangular or square facets of about 0.2 μm in size. Samples were exposed at ambient temperature to air and to vapours of 1.0 M HNO 3 and 1.0 M HCl aqueous solutions for up to 18 h and then examined by atomic force microscopy (AFM); bulk iron was examined additionally by XPS and ac impedance in a borate solution. XPS indicated the presence of iron oxides in corrosion products, possibly of Fe 2O 3, FeOOH and/or Fe 3O 4; their content increased for the exposures in the sequence: air≤HNO 3<HCl. On evaporated iron, oxides grew in the form of separated features (small columns, spikes, needles) and some of these features appeared to grow on individual facets of the substrate, whereas on bulk iron, oxides grew at random in the form of irregular hills. It was suggested that the unidirectional growth of oxides in HCl vapour was associated with the hindrance of a lateral growth by Cl-containing species. The impedance element Q 1 of the equivalent circuit R o( Q 1( R 1( Q 2 R 2))) differed for various exposures in agreement with the AFM and XPS data, suggesting that it can be used for characterisation of the morphology of surface products.

Crystal chemistry of superconducting copper oxycarbonates

The high T c superconducting oxycarbonates form a large class whose crystal chemistry is presented herein. In the form of bulk materials, five families of oxycarbonates, involving lanthanides, thallium, bismuth, lead and mercury, have been synthesized with T c values up to 80 K. Laser ablation appears to be a very promising new soft chemistry method to synthesize new oxycarbonates in the form of thin films. This is illustrated by the phases (CaCuO 2) m and (Ba 2CuO 2CO 3) n , that exhibit T c values up to 100 K.

Uses of Gold in Jewellery

Gold plays a dominant role in the jewellery market. This is to a large extent due to the intrinsic value of gold, its beauty and its unique resistance to tarnish and corrosion. In 1990 the amount of gold used in jewellery was about 2000 t worldwide, reaching about 75% of the total demand for gold. The demands on gold materials for jewellery, its applications in the form of bulk material for wrought and cast jewellery and as gold solutions for electrodeposition and electroforming as well as activities to introduce powder materials for the manufacture of jewellery are described. Today's conventional carat gold alloys are reviewed; coloured gold alloys based on the Au–Ag–Cu system, as well as the white gold alloys, based on Au–Ni or Au–Pd alloys. Additionally, the development of special gold alloys is mentioned, for instance that of a very high carat gold alloy, 990 gold–titanium.