Chromium Particles Research Articles

Characteristics of copper-containing cobalt chromium particles: Metal ion release, passive behavior, and biological response

Wear particle-induced periprosthetic osteolysis, leading to aseptic loosening, is the primary cause of total joint arthroplasty failure. Our study aimed to design Cu-containing Co29Cr9W particles (Co29Cr9W3Cu) to investigate the potential release of Cu ions from these particles in mitigating osteoclast over-activation. Analysis of Cu, Co, and Cr ion release from Co29Cr9W3Cu particles in simulated body fluid showed that Cu addition did not significantly increase metal ion release. In vitro tests confirmed the non-toxicity of Cu-containing particles to osteoblast cells, indicating minimal impact on Co, Cr, and W ion release with 3 wt% Cu addition. Importantly, Cu-containing Co29Cr9W particles demonstrated the ability to reduce osteoclast expression, potentially via inhibition of NF-κB signaling pathway. Alloying 3 wt% Cu into Co29Cr9W particle presents a promising strategy for mitigating osteoclast over-activation in wear particle-induced osteolysis.

Complex Modification of the Surface Layer of a High-Entropy Al-Cr-Fe-Co-Ni Alloy by Electron-Ion-Plasma Treatment

Using the technology of wire-arc additive manufacturing (WAAM – wire arc additive manufacture), a high-entropy alloy (HEA) of non-equiatomic composition Al, Cr, Fe, Co, Ni was manufactured. Using the methods of modern physical materials science, an analysis of the elemental and phase composition, defective substructure, mechanical and tribological properties of the HEA surface layer, formed as a result of complex modification, combining the deposition of a film (B + Cr) and irradiation with a pulsed electron beam in an argon medium, was carried out. In the initial state, the alloy has a simple cubic lattice with a lattice parameter of 0.28795 nm; the average grain size of the HEA is 12.3 µm. Chemical elements (at. %) 33.4 Al; 8.3 Cr, 17.1 Fe, 5.4 Co, 35.7 Ni, which form HEA, are distributed quasi-periodically. The irradiation regime was revealed (energy density of the electron beam ES = 20 J/cm2, pulse duration 200 µs, number of pulses 3 pulses, frequency 0.3 s more than 5 times), allowing to increase microhardness (almost 2 times) and wear resistance (more than 5 times), reduce the coefficient of friction by 1.3 times. Regardless of the value of ES, HEA is a single-phase material and has a simple cubic crystal lattice. High-speed crystallization of the surface layer leads to the formation of a subgrain structure (150–200) nm. It is shown that an increase in the strength and tribological properties of HEA is due to a significant (4.5 times) decrease in the average grain size, the formation of particles of chromium and aluminum oxyborides, and the incorporation of boron atoms into the crystal lattice of HEA.

Assessment of the ecotoxicity of heavy metal contaminants on aquatic organisms: A reviewon the impact of Lead, Chromium, Cadmium, Zinc and Mercury

Heavy metal ecotoxicity has been recognized to be a major threat to aquatic organisms and there are several health risks associated with it.This in-depth review investigation explores the critical issue of heavy metals pollution, concentrating on the hazardous effects of chromium, cadmium, lead, mercury, and zinc oxide nano particles on aquatic species.

Efficient NiFeCr0.1/NF by incorporating chromium to boost OER catalysis

This study developed ternary NiFeCr hydroxide microsphere composites for efficient oxygen evolution reaction (OER) in alkaline water. Compared to binary NiFe composites, the ternary composites exhibited superior electrocatalytic activity. In a 1 M KOH solution, the ternary composite demonstrated a low initial potential of 1.46 V (RHE), and the overpotential is only 268 mV @ 100 mA cm−2. Charge rearrangement due to chromium oxidation helped maintain iron's low oxidation state, preserving OER activity. The redistribution of chromium particles stabilized iron and prevented its dissolution in an alkaline solution. Consequently, the optimized NiFeCr catalyst exhibits excellent stability, with a stability of 200 h at 100 mA cm−2. This study offers a novel approach to designing efficient and stable catalysts for water decomposition.

Silver Alloy Surface Modification for Mechanical Property Enhancement in Aviation and Transportation

Silver alloys are often used for electrical switches in railway transportation. However, a well-known issue with these switches is their relatively short application period due to certain disadvantages of silver alloys, mainly their low hardness and low resistance to abrasive wear, in contrast to their excellent electrical conductivity. Therefore, the main goal of this study was to increase or maintain the hardness of the surface layer in order to extend the life of worn parts without compromising their electrical properties. Instead of ceramic particles, as in other studies, metallic powders were used, which could increase the electrical and/or thermal properties of silver alloys. The following work presents the use of laser processing as a relatively new technique for metal and metal alloy surface processing technology. In particular, a process based on the melting of silver (Ag) with metallic powders, such as chromium (Cr) and nickel (Ni) particles, is presented. The aim was for these powders to create intermetallic phases with a silver matrix in the obtained surface layer, significantly improving the mechanical properties based on the formation of the phases coherent or semi-coherent with the silver matrix. Regarding the original practical implications of this work, it was important to investigate the possibility of applying fibre laser for surface property enhancement. The scientific aim was to describe the changes in microstructure and compounds that occurred in the laser-remelted surface silver layer after Ni and Cr particles were fed into the basic silver material. It was concluded that the surface layer obtained after chromium application was without cracks and defects and had a higher hardness than the untreated material. A three-zone structure was also found in the obtained surface layer: (1) the remelted zone, (2) the heat-affected zone, and (3) the matrix material. The remelting zone revealed a higher hardness compared to the untreated material, reaching 92 HV0.3, which is more than twice the initial hardness value.

Restoration of continuous casting machine mold copper plates made of Cr–Zr bronze using multi-pass friction stir lap welding

An innovative technology has been developed and implemented for the restoration and manufacturing of new mold copper plates for continuous casting machines (CCMs) using wear-resistant composite coatings. These copper plates significantly surpass the service life of imported copper plates featuring galvanic coatings, sometimes by up to 20 times. However, the pressing challenge of restoring the copper plates of molds once they have reached the minimum permissible thickness remains unresolved. This study aimed to explore the feasibility of restoring a plate composed of precipitation-hardening Cr–Zr bronze with the same material by employing friction stir lap welding (FSLW). The objectives were to examine the structure, quality, and hardness of the welded joint, alongside investigating the impact of heat treatment (quenching and aging). By utilizing multi-pass FSLW method with a rotating tool crafted from a heat-resistant alloy and overlapping (partially overlapping) successive passes, a welded joint with a thickness of ~5 mm was achieved, devoid of critical continuity flaws (cracks or voids). Within the bronze layer restored through FSW, a softening effect ranging from 85–105 HV1 was observed compared to the initial hardness of the bronze in its hardened and aged state while in service (116–126 HV1). This is attributed to recrystallization and overaging, specifically the coarsening of chromium particles within the Cr–Zr bronze due to the heating of the weld nugget (stir zone) to 600–700 °C. The observed softening effect during FSW can be effectively rectified through heat treatment involving dissolution of the hardening phases followed by aging, resulting in a hardness increase to approximately 120–150 HV1. The process of restoring copper plates to their original thickness via the progressive and environmentally friendly FSW method, followed be the subsequent application of wear-resistant composite coatings, presents the opportunity for an almost infinite operational cycle of molds. This advancement could potentially eradicate the necessity for Russia to rely on importing such molds copper plates.

Studies on Engine Oil Degradation Characteristics in a Field Test with Passenger Cars

Nowadays, a car’s engine oil change interval is an essential factor in reducing wear. The correct choice depends on various factors. This study analyzes the changes in the composition of three different engine oils (0W30, 5W30, and 5W40) during the generally accepted oil change interval (15,000 km) in gasoline and diesel cars during the post-warranty period. Commercially available low-level biofuel blends (B7 and E10) were used to power test vehicles in a field test. Engine oil samples were taken every 3000 km for more detailed analysis and tested in an accredited laboratory. The contaminants in the engine oil were determined using several testing methods: spectrometric analysis, gas chromatography, etc. Studies have shown that all used cars have an increase in the number of iron particles, an increased concentration of silicon, and also an increase in the number of nickel particles above 12,000 km. Tests also showed a sharp drop of molybdenum anti-friction additives 4.5 times and a gradual increase in fuel concentration for the Opel Insignia over 12,000 km, but over 9000 km, a significant increase in the concentration of chromium particles. Based on this research results, it is preferable to choose a maintenance interval of no more than 12,000 km for cars during the post-warranty period. In this way, the intensity of engine wear can be reduced due to the loss of adequate protective properties of the engine oil.

Precipitates evolution during isothermal aging and its effect on tensile properties for an AFA alloy containing W and B elements

A 20Cr-25Ni-2.5Al alumina-forming austenitic alloy containing W and B elements was aged at 923 K for 5000 h, and the microstructure and tensile properties with different aging time were investigated. NiAl, σ and Laves were observed at grain boundaries (GBs) successively. The matrix was covered by NiAl and Laves with the extension of aging. The evolution of precipitates during aging contributed to the variation of tensile properties. Precipitation of nanosized NbC carbides within grains and σ phase at GBs led to a rapid increase in strength and a decrease in elongation for 500 h aging sample. In the later stage of aging, the coarsening of NiAl and Laves phases, as well as the reduction in dislocation density caused a decline in strength. The coarsening of precipitates upon aging time follows the Ostwald ripening theory. Due to its lower diffusion rate in austenite compared to Mo, W may accelerate the growth of Laves at GBs. Boron was mainly enriched in Laves instead of NiAl, NbC and σ phases after high temperature aging. The addition of W and B improved the precipitation strengthening of Laves, increasing the high temperature tensile strength after long term thermal aging. The difference in tensile properties between room temperature and 923 K is due to the ductile–brittle transition of NiAl. No σ phase was observed within grains even after 5000 h aging and elemental chromium particles occurred around Laves due to boron hindering the growth of σ.

Phenylalanine Self-Assembled Nanotubes Intercalated Sol-Gel Silica Membrane for Synergetic Removal of Harmful Chromium and Dye Particles—Assembling, Probing and Novel Photocatalytic Recycling

Phenylalanine Self-Assembled Nanotubes Intercalated Sol-Gel Silica Membrane for Synergetic Removal of Harmful Chromium and Dye Particles—Assembling, Probing and Novel Photocatalytic Recycling

Achieving strong Pb-Cr complexation in Mg/Al LDHs for ultrafast chromate ions separation and chrome recovery from complex water matrices

Layered double hydroxides with high anion exchange capacity and positive surface charge were being explored to remove metal oxo-anions. Environmental complexities such as the presence of other major interfering anions, organic matter, etc., drastically hampers their performance and limit their applicability. Based on the fundamental understanding of strong Pb-Cr complexation, in this work, Pb2+ incorporated LDH (LDH-Pb) was designed for selective chemisorption of chromate ions overcoming existing environmental limitations of LDH for chromium removal. LDH-Pb was designed by substituting Mg2+ ions of Mg/Al LDH with Pb2+ during crystallization process. Pb2+ have shown efficient incorporation at MII crystal sites of Mg/Al LDH and also sorbed in form of oxy-hydroxide on the surface. Pertaining to faster Pb-Cr complexation, strong binding, and formation of insoluble PbCrO4, LDH-Pb has shown efficient and higher removal of chromate ions than LDHs. Despite environmental complexities such as varying pH, competitive ions, organic matter, and natural matrices, efficiency of LDH-Pb remained less altered. Direct application (proof-of-concept) has been shown for extraction of chromate ions and chrome recovery from collected chromite ore processing residue leachate contaminated groundwater samples. Higher-order of removal kinetics and sorption capacity of LDH-Pb (n = 9.2, and 188.7 mg/g) further justified its candidature. Strong Pb-Cr complexation in LDH-Pb further resulted in faster and efficient continuous chromate filtration (47.3 mg/g) with adsorbent loaded syringe filters. Chrome recovery was achieved through easy acid dissolution of LDH from LDH-Pb-Cr waste (pH <3) resulting in chrome particles (monocrystalline micro rods) that have several potential industrial applications in various sectors.

Sliding wear behavior of cold metal transfer cladded Stellite 12 hardfacings on martensitic stainless steel

Cold metal transfer (CMT) welding technique was used in the manufacturing of hypoeutectic carbide-type Co-based Stellite 12 hardfacings on martensitic stainless steel. It was discovered that the CMT process is capable of producing relatively thick (> 2.5 mm) low diluted single-layer coatings with cored Stellite 12 wire without cracks and pores. These coatings were investigated using microscopy (optical and scanning electron microscopy), X-ray diffraction, and hardness measurements. The high melting point chromium and tungsten particles inside the cored wire were relatively large and therefore remained unmelted in the clad layers. Self-mated sliding wear tests were performed using a pin-on-disc tribometer at room temperature and at 300 °C to determine the wear resistance and friction of the coatings. The coefficients of friction were relatively similar (~ 0.35) at both temperatures. Differences were exhibited in the ~ 40% greater loss of material at high temperature. The wear performance of the CMT clad Stellite 12 coatings did not, however, reach the wear performance of self-mated laser clad Stellite 6 reference material. CMT hardfacing was finally successfully demonstrated on a ring-shaped component.

Preparation of carbon materials from chromium-tanned leather shavings for the removal of dyes from aqueous solution

Chromium-Tanned Leather Shavings are hazardous residues generated during leather processing. Since they contain considerable amounts of chromium, they represent a threat to life and the environment if managed improperly. The present study examines the transformation of such residues into carbon adsorbents and their use in the removal of azo dyes (methylene blue, Congo red and acid black 210) from water. The effects of temperature, holding time and the presence of an activating agent were studied, and basic characterization of the produced materials was performed. Carbon materials contain a low amount of chromium and an improved surface area that was only developed when high temperatures and an activating agent were employed. Depending on the synthesis conditions, the adsorbents’ surface charge was positive or negative, which impacts the dye uptake from aqueous solution. Both the chemical speciation of the dye and the material´s pore volume played a critical role during the adsorption process. It is possible to obtain carbon materials from Chromium-Tanned Leather Shavings, containing no hazardous chromium(VI) particles, that are capable of removing polluting dyes from water.

Influence of the powder metallurgy route on the mechanical properties of Cu–Cr–diamond composites

Metal-bonded grinding tools are commonly based on copper as bond material and possess low porosity. The powder metallurgic fabrication and the applied process parameters have a high influence on the mechanical properties of these grinding layers. In this study, Cu–diamond composites are fabricated through Field Assisted Sintering Technology with a variation of holding time, temperature, pressure, and chromium powder particle size. The addition of chromium to these composites can ensure a higher adhesion of the diamonds through carbide formation within the interface of the diamonds and the copper bonding matrix. The coating of diamond with chromium-carbide is mainly controlled by the chromium powder particle size, which leads to a higher critical bond strength with decreasing particle size. Maximum critical bond strength of 463 N/mm2 is reached using chromium with an average particle size of 10 µm. Increasing holding time decreases porosity and increases the critical bond strength of the composites. An increase of sintering temperature from 900 to 1040 °C leads to a decrease of porosity due to local melting of the copper. The interlocking of diamonds due to their high concentration of 50 vol% within the composites results in a relatively high porosity above 7%.Article HighlightsModelling of the influence of sintering temperature, sintering time and chromium particle size on the critical bond strengthAddition of chromium results in an in-situ formed carbide-layer when sintering above a temperature of 900 °CSmaller chromium particle sizes significant increase the mechanical stability of CuCr–diamond composites

Impact of Nano- and Micro-Sized Chromium(III) Particles on Cytotoxicity and Gene Expression Profiles Related to Genomic Stability in Human Keratinocytes and Alveolar Epithelial Cells.

Exposure to Cr(VI) compounds has been consistently associated with genotoxicity and carcinogenicity, whereas Cr(III) is far less toxic, due to its poor cellular uptake. However, contradictory results have been published in relation to particulate Cr2O3. The aim of the present study was to investigate whether Cr(III) particles exerted properties comparable to water soluble Cr(III) or to Cr(VI), including two nano-sized and one micro-sized particles. The morphology and size distribution were determined by TEM, while the oxidation state was analyzed by XPS. Chromium release was quantified via AAS, and colorimetrically differentiated between Cr(VI) and Cr(III). Furthermore, the toxicological fingerprints of the Cr2O3 particles were established using high-throughput RT-qPCR and then compared to water-soluble Cr(VI) and Cr(III) in A549 and HaCaT cells. Regarding the Cr2O3 particles, two out of three exerted only minor or no toxicity, and the gene expression profiles were comparable to Cr(III). However, one particle under investigation released considerable amounts of Cr(VI), and also resembled the toxicity profiles of Cr(VI); this was also evident in the altered gene expression related to DNA damage signaling, oxidative stress response, inflammation, and cell death pathways. Even though the highest toxicity was found in the case of the smallest particle, size did not appear to be the decisive parameter, but rather the purity of the Cr(III) particles with respect to Cr(VI) content.

Reactive grid-assisted co-sputtering of titanium and chromium in a pure nitrogen atmosphere: Uniformity, optics, and structure of the Ti–Cr–N films

This study provides the results of the first attempt to deposit thin films by reactive grid-assisted co-sputtering with the deployment of small grounded grids having two varying apertures for enabling the transfer of particles. The diameter of all the grids utilized was 50 mm, and their apertures' diameters were changed from 5 mm to 15 mm. Furthermore, the ratios of the grid area to the chamber wall area were lower than 0.0161, preventing the formation of ion-rich sheaths and their adverse impact upon discharge and plasma stability. Accordingly, Ti 1 Cr 1-x N films (0.88 < x < 0.97) with low chromium contents were deposited on soda-lime glass substrates by using pure nitrogen as the sputtering gas. The grazing incidence X-ray diffraction patterns of the films, the average thicknesses of which were lower than 50 nm, showed no sign of crystallinity in the films. Ranging from 3.26 to 3.79 eV, the optical bandgap of the films changed by altering the apertures’ size; chromium content, internal stress, and quantum confinement effect appeared to be the main contributing factors. The photoluminescence intensities appertaining to trap state emissions reflected a decreasing trend by increasing the chromium content, which can be ascribed to the capability of the chromium particles included in the surface, structure, and grain boundaries of the films to prevent photoinduced electron-hole pairs from recombination. It was found that not only is the grid-assisted co-sputtering method an effective tool whereby the doping range of conventional co-sputtering methods can be significantly extended but also it can cover a spectrum of surface morphologies. However, in comparison with the conventional co-sputtering method, the utilization of the grids with fairly small apertures can limit the thickness uniformity of the films; this effect may be attenuated by changing the geometry and design of grids.

Adsorptive removal of chromium from aqueous solutions using flax (Linum usitatissimum): Kinetics and equilibrium studies

Chromium (Cr) ions, discharging from different industrial activities, especially from leather tanning industries, are becoming a major threat for the environment and human health. Therefore, elimination of chromium ions from industrial effluents should be addressed with great attention. Hence, this study was conducted for evaluating the possibilities of using an agricultural waste “flax” to eliminate Cr (III) ions from aqueous solutions. In order to assess the effects of various experimental parameters (i.e., contact time, pH, adsorbent amount, initial chromium ion concentration and particle size) on Cr (III) ions adsorption process, the batch adsorption study was conducted. This study revealed that adsorption of Cr (III) ions by flax required 420 min to reach equilibrium. On the other hand, the maximum (~70%) Cr (III) ions removal was observed at pH value of 2.0. The desorption efficiency with 0.5 M KOH was found to be 90%. The Langmuir and Freundlich isotherms models were in better correlation with experimental data, according to equilibrium studies. Kinetic experiments showed that the first order kinetics with a rate constant of 0.01 min−1. Use of real wastewater sample became a great success for removing of Cr (III). This result suggests that the flax plant has the potentiality to become an effective and environmentally friendly economical adsorbent for the removal of Cr (III) ions significantly from waste water.

The Influence of Manufacturing Technology on the Properties of Chromium-Bronze Electrodes for Contact Relief Welding of Reinforcing Rods

The article discusses an effective, in comparison with common, technology of manufacturing chromium bronze electrodes for resistance projection welding of reinforcing bars. Within the framework of this technology, a method for preparing a melt with alloying with a multicomponent element, including basic elements, a matrix of copper powder and a filler of nanostructured chromium particles, is considered. The technology is based on a combined molding-plastic deformation process and makes it possible to obtain a finished resistance welding electrode of type D in one operation. The results of microstructural, X‑ray micro-spectral and local energy dispersive (micro) analysis of electrode samples obtained by different technologies, explaining the main nature of the loss of electrode performance, are presented. The results of fractographic studies of the contact surface of the electrodes are considered. Electrical conductivity and mechanical properties were studied for all electrode samples. The results of tests on a resistance welding machine with an assessment of the wear of the electrodes and the reasons for their failure are presented

Dusts Control operations in Ririwai Mines, Kano State, Nigeria

Respirable dust is everywhere (in the surface and underground mine) operations and its environs. Ririwai Tin mine is laden with dust of metallic particles of Arsenic (As), Chromium (Cr), Lead (Pb) and Zinc (Zn). These particles are also found in the soil. Continuous inhalation of dust could lead to irreversible diseases. This paper addresses the control of dust, using previous review of prevailing metallic concentrates. This research answers questions like which are the dust control strategies to be adopted by Ririwai tin mine to obtain best practice? What challenges will Ririwai tin mine face when applying dust control methods in their operation? What is the impact of dust laden with metallic particles on soil, water, vegetation and man in Ririwai tin mine?

Dusts Control operations in Ririwai Mines, Kano State, Nigeria

Respirable dust is everywhere (in the surface and underground mine) operations and its environs. Ririwai Tin mine is laden with dust of metallic particles of Arsenic (As), Chromium (Cr), Lead (Pb) and Zinc (Zn). These particles are also found in the soil. Continuous inhalation of dust could lead to irreversible diseases. This paper addresses the control of dust, using previous review of prevailing metallic concentrates. This research answers questions like which are the dust control strategies to be adopted by Ririwai tin mine to obtain best practice? What challenges will Ririwai tin mine face when applying dust control methods in their operation? What is the impact of dust laden with metallic particles on soil, water, vegetation and man in Ririwai tin mine?

Optimization of machining parameters in chromium-additive mixed electrical discharge machining of the AA7075/5%B4C composite

The present study establishes the optimum process condition for additive mixed electrical discharge machining of Al7075–5%B4Cp metal matrix composite by performing experimental investigation. The suspension of chromium particles in a dielectric fluid is used as an additive. The input process parameters selected for experimentation are specifically pulse on-time, gap voltage, pulse off-time and peak current, for analysing their influence on wear of the tool along with surface roughness of the composite. Comparative study of the machined surface is done by analysing microstructures, cracks and recast layers formed at different settings of input parameters using a scanning electron microscope. Rise in amount of current and pulse on-time led to increased height of the recast layer generated on the surface of the machined workpiece. Furthermore, a confirmatory experiment was performed at the optimal setting. The result revealed an error of 5.5% and 7.5% between experimental and predicted value of tool wear rate and surface roughness.