Chromium Particles Research Articles

Thresholds for indirect DNA damage across cellular barriers for orthopaedic biomaterials

Cobalt–chromium particles and ions can induce indirect DNA damage and chromosome aberrations in human cells on the other side of a cellular barrier in tissue culture. This occurs by intercellular signalling across the barrier. We now show that the threshold for this effect depends on the metal form and the particle composition. Ionic cobalt and chromium induced single strand breaks at concentrations equivalent to those found in the blood of patients with well functioning metal on metal hip prostheses. However, they only caused double strand breaks if the chromium was present as chromium (VI), and did not induce chromosome aberrations. Nanoparticles of cobalt–chromium alloy caused DNA double strand breaks and chromosome aberrations, of which the majority were tetraploidy. Ceramic nanoparticles induced only single strand breaks and/or alkaline labile sites when indirectly exposed to human fibroblasts. The assessment of reproductive risk from maternal exposure to biomaterials is not yet possible with epidemiology. Whilst the barrier model used here differs from the in vivo situation in several respects, it may be useful as a framework to evaluate biomaterial induced damage across physiological barriers.

Macrophages detoxify the genotoxic and cytotoxic effects of surgical cobalt chrome alloy particles but not quartz particles on human cells in vitro

Particles of surgical cobalt chrome alloy are cytotoxic and genotoxic to human fibroblasts in vitro. In vivo orthopaedic patients are exposed to cobalt chrome particles as a result of wear of a joint replacement. Many of the wear debris particles that are produced are phagocytosed by macrophages that accumulate at the site of the worn implant and are disseminated to local and distant lymph nodes the liver and the spleen. In this study we have tested whether this process of phagocytosis could have altered the cytotoxic and genotoxic properties of the cobalt chrome particles. Quartz particles have been investigated as a control. Micron-sized particles of cobalt chrome alloy were internalised by either white cells of peripheral blood or by THP-1 monocytes for 1 week and 1 day, respectively. The particles were then extracted and presented at different doses to fibroblasts for 1 day. There was a reduction of the cytotoxicity and genotoxicity of the cobalt chrome particles after phagocytosis by white cells or THP-1 cells. Cobalt chrome particles that were internalised by fibroblasts also showed a reduction of their cytotoxicity but not their genotoxicity. In contrast the cytotoxicity and genotoxicity of quartz particles was increased after internalisation by THP-1 cells. The surface morphology of the cobalt chrome particles but not the quartz particles was changed after phagocytosis by THP-1 cells. This study suggests that the genotoxic and cytotoxic properties of particles that fall within the size range for phagocytosis may be highly complex in vivo and depend on the combination of material type and previous phagocytosis. These results may have relevance for particle exposure from orthopaedic implants and from environmental or industrial pollution.

Environmental inequality: Air pollution exposures in California's South Coast Air Basin

Environmental inequality is quantified here using linear regression, based on results from a recent mobility-based exposure model for 25,064 individuals in California's South Coast Air Basin [Marshall et al., 2006. Inhalation intake of ambient air pollution in California's South Coast Air Basin. Atmospheric Environment 40, 4381–4392]. For the four primary pollutants studied (benzene, butadiene, chromium particles, and diesel particles), mean exposures are higher than average for people who are nonwhite, are from lower-income households, and live in areas with high population density. For ozone (a secondary pollutant), the reverse holds. Holding constant attributes such as population density and daily travel distance, mean exposure differences between whites and nonwhites are 16–40% among the five pollutants. These findings offer a baseline to compare against future conditions or to evaluate the impact of proposed policies.

Effect of Microstructure on the Accelerated Creep of 20CrMoV12‐1 and P 91 Steels

In the initial part the change of microstructure for steel X20 CrMoV 121 is discussed in terms of the distribution of carbide precipitates and its effects on accelerated creep resistance and hardness are presented. In the following, experimental results of microstructure and accelerated creep resistance are presented for the steels X20CrMoV 121 and P91 annealed for up to 8760 hours at 650°C and 750°C before the testing. A similar evolution of the distribution of carbide particles of a size above 102 nm is found for both steels, while the accelerated creep resistance is diminished much stronger for the steel X20CrMoV 121. This difference is due to a greater stability of NbC than that of VC precipitates, both related to the evolution of the chemical composition of complex chromium, molybdenum and iron carbide particles.

Preparation and Characterization of Black Chrome Solar Selective Coatings

Black chrome coatings (Cr-Cr2O3) were prepared on nickel-coated copper substrates by using an electroplating technique. The changes in the physical properties of the sample due to thermal degradation were characterized by Auger electron spectroscopy, glow discharge spectrometry, and UV-Vis-NIR spectrophotometry. The optimum black chrome coating was made on a nickel-coated copper substrate by using a newly synthesized electrolyte at a current density of 260 270 mA/cm 2 for 1.5 2.0 min. Its optical properties were a solar absorptance of 0.80 0.90 and a thermal emittance of 0.01 0.03. From the surface analysis, the concentration of chrome granules near the nickel layer was higher than at the surface, which suggests that the selective absorption was dominated by finely divided metallic chrome particles. The surface of this film exhibited a morphology with root-mean-square roughness of 55.83 nm. We also found that the thermal aging characteristics of the black chrome coating annealed at temperature of above 450 C occurred primarily due to both oxidation of the metallic chrome particles and diusion of the copper substrate materials. Atomic force microscopy showed that black chrome layers with increasing annealing temperatures became very rough and that their grain sizes became very large. X-ray photoelectron spectroscopy measurements showed that the binding energy of the major component in the as-prepared black chrome films was chrome in the hydroxide form. The result of the thermal stability test showed that the black chrome selective coating was stable for use at temperatures under 350 C.

Effects of Chromium Particle on Elevated Temperature Tensile Strength of Cu-Cr Alloy

Effects of Chromium Particle on Elevated Temperature Tensile Strength of Cu-Cr Alloy

Genotoxic effects of particles of surgical cobalt chrome alloy on human cells of different age in vitro

Humans are exposed to metals from industry, the environment and from wear debris from worn orthopaedic joint replacements. Patients exposed to worn cobalt chrome hip replacements show an increase of chromosome aberrations in the bone marrow adjacent to the implant and an increase of chromosome translocations and aneuploidy in the peripheral blood. This study has tested whether particles of surgical cobalt chrome alloy are able to induce similar DNA damage and chromosome aberrations in human cells in vitro. Because increasingly young patients are receiving hip replacements it has also tested whether the response is altered at different cellular age in vitro. Primary human fibroblasts, were tested at different pre senescent population doublings (PD10 (young) and PD35 (older)) to particles of cobalt chrome alloy for up to 15 days. As in patients there was an increase of aneuploidy, chromosome translocations and DNA damage after exposure to the cobalt chrome particles in vitro. The overall level of DNA damage and numerical and structural aberrations was approximately the same in young and older cells. However, the cellular reaction to the DNA damage was different. Older cells showed a greater loss of viability and induction of senescence and a lesser rate of mitosis and cell growth than young cells. They showed less change in transcription, particularly of p38 and caspase 10 mRNA levels, than young cells. They showed more complex aneuploidy in association with unseparated or prematurely separated chromatids. This study suggests that at least part of the chromosome changes in patients with worn implants may be due to direct effects of the metal wear particles from the implant. It would be of interest to test whether the altered reaction of the human cells at different in vitro age might correspond with a different incidence of chromosome aberrations in patients at different ages.

Eco-Friendly Rubberized Cotton Fabric Roller for Ginning Machines

This article discusses the pollution caused by chrome composite leather-clad (CCLC) rollers commonly used in cotton roller ginning mills and suggests an alternative roller material. CCLC rollers contain about 18,000 to 36,000 mg/kg (ppm) total chromium in trivalent and hexavalent forms, which are toxic to human health and carcinogenic. When seed-cotton is processed in double roller (DR) ginning machines, the lint is contaminated with chromium, and chromium particles are carried into the spun yarns and cotton by-products. Specifically, due to persistent rubbing of the leather-clad roller over the stationary knife during the ginning process, the lint is contaminated with about 140 to 1990 ppm of chromium, and the spun yarns and cotton by-products contain about 100 to 200 ppm, far in excess of the standard limit of 0.1 ppm. Gin and mill workers are directly exposed to this carcinogenic substance. To offset this problem, pollution-free rubberized cotton fabric (RCF) rollers have been fabricated and tested in roller gins. The RCF roller covering is made of multiple layers of fabric bonded together using a white rubber compound, which has a surface finish conducive to high ginning efficiency. This eliminates chromium contamination and pollution during the ginning process. On the basis of the design and development of various test rollers and subsequent evaluation studies, the performance of pollution-free RCF rollers has been demonstrated with reference to their commercial benefit and eco-friendliness in cotton ginning mills.

An optical trapped microhand for manipulating micron-sized objects

We have developed a real time interface for holographic optical tweezers where the operator's fingertips are mapped to the positions of silica beads captured in optical traps. The beads act as the fingertips of a microhand which can be used to manipulate objects that otherwise do not lend themselves to tweezers control, e.g. objects that are strongly scattering or highly light sensitive. We illustrate the use of the microhand for the real time manipulation of micron sized chrome particles.

Spirometric Abnormalities Among Welders

P-751 Abstract: A group of manual welders (N=57) engaged in gas welding joint faces of moulded brasswares, age group 13–60 years (mean: 29.2 ± 1.37 years), having a mean exposure period of 12.4 ± 1.12 years (range 1–35 years) were subjected to spirometry to evaluate the prevalence of spirometric abnormalities. The findings were compared with those obtained from a reference group (N=131) (mean age 31.2 ± 1.35 years) engaged in non-welding jobs such as packing, labelling and transportation of finished brassware articles. The welders showed a significantly higher prevalence of respiratory impairment (28.0%) than that observed among the unexposed controls (6.1%) (p <0.001) as a result of exposure to welding gases which comprised fine particles of Lead, zinc, chromium and manganese. This occurred despite the lower concentration of the pollutants at the work place. In the exposed group, the smoking welders showed a prevalence of respiratory impairment significantly higher than that observed in the non-smoking welders (40.0 vs 18.7%) (p < 0.10). A similar trend was observed in the control group indicating that smoking had a deteriorating effect on spirometric tests. The results of the pulmonary function tests showed a predominantly restrictive type of pulmonary impairment (12.3%) followed by a mixed ventilatory defect (8.7%) among the welders. The effect of age on pulmonary impairment was not discernible either in the exposed or unexposed group. Welders exposed for over 10 years showed a prevalence of respiratory abnormalities significantly higher than those exposed for less than 10 years (44.4% vs 13.3%) (p<0.01) thereby showing that occupational exposure to welding fumes resulted in increased prevalence of pulmonary impairment.

Laboratory Study of Simulated Atmospheric Transformations of Chromium in Ultrafine Combustion Aerosol Particles

While atmospheric particles can have adverse health effects, the reasons for this toxicity are largely unclear. One possible reason is that the particles can contain toxic metals such as chromium. Chromium exists in the environment in two major oxidation states: III, which is an essential nutrient, and VI, which is highly toxic and carcinogenic. Currently little is known about the speciation of chromium in airborne particles or how this speciation is altered by atmospheric reactions. To investigate the potential impacts of atmospheric aging on the speciation and toxicity of chromium-containing particles, we collected chromium and chromium-iron combustion ultrafine particles on Teflon filters and exposed the particles to a combination of light, ozone, water vapor, and, in some cases, basic or acidic conditions. After the aging process, the aged and not-aged samples were analyzed for Cr oxidation state using X-ray Absorption Near Edge Spectroscopy (XANES). We found that the aging process reduced Cr(VI) by as much as 20% in chromium particles that had high initial Cr(VI)/Cr(total) ratios. This reduction of Cr(VI) to Cr(III) appears to be due to reactions primarily with light and hydroperoxyl radical (HO 2 ) in the chamber. Particles that had low initial Cr(VI)/Cr(total) ratios experienced no significant change in Cr oxidation states after aging. Compared to particles containing only Cr, the addition of Fe to the flame decreased the Cr(VI)/Cr(total) ratio in fresh Cr-Fe particles by ∼60%. Aging of these Cr-Fe particles had no additional effects on the Cr(VI)/Cr(total) ratio.

Processing, microstructure and mechanical properties of Al 2O 3–Cr nanocomposites

Alumina–chromium composites are well known for their good mechanical properties in comparison with pure alumina or metals. The composites have high hardness, high mechanical strength and because of their strong resistance to abrupt changes of temperature within the 25–1300 °C range or high temperature resistance to oxidation, they can be used at temperatures exceeding 1000 °C. Most of earlier works tended to use particles in the micrometer range. In this work, Al 2O 3–Cr nanocomposites with 25, 50 and 75 vol.% Cr were made by pressureless sintering and hot pressing of aluminium oxide nanopowder (∼80 nm) and chromium particles in the micrometer range. The presented paper concerns the examination of the microstructure and mechanical properties (hardness, bending strength, wear resistance) of Al 2O 3–Cr nanocomposites. The microstructural examinations (optical, scanning and transmission microscopy) show that almost fully dense materials can be obtained (typically 98–99% of theoretical density), when pressureless sintering at 1600 °C or hot pressing at 1400 °C. Moreover, the sintering process did not cause any major changes in the structure of the composite, although it was stated significant growth of the Al 2O 3 nanograins.

Fatigue properties of Cu–Cr in situ composite

The new electrical conductive material, Cu–15 mass%Cr in situ composite, has been developed for the application to lead frame, high field magnet and trolley wire. The Cu–Cr composite was fabricated by casting method in vacuum and forged, solution-treated and cold drawn. The value of the cold drawing strains, η, for the composite were 4.66 and 6.94. η is defined by the value of ln( A 0/ A), where A 0 and A are virgin area and final area of material, respectively. The cold drawn Cu–Cr composite was tested using a rotating bending fatigue testing machine and axial loading fatigue testing machine ( R = 0.1, where R is stress ratio of minimum stress to maximum stress) at room temperature in comparison to the data for pure copper. The fatigue stresses decreased with increasing number of cycles to failure. The double-knees, which have been found in other face centered cubic materials, such as aluminum alloys, were not seen on the S– N curves for both alloys. The fatigue strength of Cu–Cr composite was twice higher than that for pure copper. The fatigue strength of Cu–Cr composite cold drawn up to η = 6.94 was higher than that drawn up to η = 4.66 when tested under an axial loading. In the fatigue fracture surface, the fatigue crack initiated from the un-dissolved chromium particle situated beneath the specimen surface and the crack direction was changed along the chromium fiber. It was suggested that, in order to improve the fatigue strength of Cu–Cr composite, it is very important to reduce the size and amount of un-dissolved chromium particles.

The effect of the GMA cermet-wire surfacing method on the weld quality in multipass welding

Surfacing is a technological process which is finding an ever widening range of applications. It is used for both the repairing of the worn-out, and the manufacture of new machine parts and equipment. This is linked to economic (cost of materials, and cost of repairs), technological, and usage factors. One of the methods which lowers costs of repairs, and of manufacture of new parts, while ensuring their high quality, is the GMAW, cermet-wire surfacing technique (Gas Metal Arc Welding-employing consumable electrodes in gas shields). Cermets are ceramic materials with metal or alloy bases which thus combine characteristic properties of both types of materials. They are characterised by their high resistance to abrasive wear, dynamic loading, thermal shocks, heat effects, and by their strength and resistance to corrosion. Flux-core wires with metallic particles of chromium or tungsten carbides are used in this process1–5 making it possible to produce surfaces which are highly resistant to abrasive wear.

Metallkundliche Differenzierung von Kobalt-Chrom-Legierungen für Implantate

Cobalt Chromium alloys are used in cemented total hip or knee arthroplasty as well as in metal-on-metal bearings in total hip arthroplasty. An increasing number of publications report about (allergic) reactions to wear particles of Cobalt Chromium alloys. Reactions to nickel are more frequent in comparison to Cobalt or Chromium particles. It is well known that different kinds of Cobalt Chromium alloys contain different amounts of alloying elements; nevertheless. The aim of the current work was to compare the different Cobalt Chromium alloys according to ASTM F or ISO standards in respect to the different alloying elements. Co28Cr6Mo casting alloys according to ASTM F 75 or ISO 5832-4 as well as forging alloy types according to ASTM F 799 and ISO 5832 such as Co20Cr15W10Ni, Co35Ni20Cr, Fe40Co20Cr10Ni, Co20Cr20Ni, and Co28Cr6Mo were analyzed in respect to their element content of Co, Cr, Ni, Mo, Fe, W, and Mn. In 1935 the Cobalt based alloy "Vitallium" Co30Cr5Mo basically used in the aircraft industry was introduced into medicine. The chemical composition of this alloy based on Cobalt showed 30 wt.% Chromium and 5 wt.% Molybdenum. The differentiation using alloy names showed no Nickel information in single alloy names. The information given about different alloys can lead to an unprecise evaluation of histopathological findings in respect to alloys or alloying constituents. Therefore, implant manufacturers should give the exact information about the alloys used and adhere to European law, Euronorm 93/42/EWG.

Efecto de la adición de un 10 % en volumen de cromo en el comportamiento a tracción de aleaciones pulvimetalúrgicas NiAlCr

The mechanical properties of Ni 3 Al-Cr reinforced with 10% in volume fraction of chromium particles produced by powder metallurgy have been studied. For this purpose, milled powders with composition of Ni-20.9Al-8Cr-0.49B (% at.) with and without the addition of 10% in volume fraction of chromium particles have been produced. Both alloys were consolidated by hot isostatic pressing (HIP). After HIP, heat treatment was applied to homogenize the microstructure. The chromium reinforcement has an important effect in the yield strength and ultimate strength increase. The reinforced alloy presents a yield strength of 1300 MPa at room temperature with respect to 800 MPa for the un-reinforced material. After heat treatment, the yield strength of both alloys does not change significantly. However, a decrease in ductility and ultimate tensile strength have been observed

Synthesis of chromium substituted nano particles of cobalt zinc ferrites by coprecipitation

Nano particles of chromium substituted cobalt zinc ferrite have been synthesized by a chemical co-precipitation method. X-ray diffraction studies of the nano particles of CrxCo0.5−xZn0.5Fe2O4 (x=0.1 to 0.5) heat-treated at 300 °C show that the particle sizes are in the range of 2 to 7 nm. Room temperature Fe-57 Mössbauer spectra of all the samples show only two doublets, confirming the presence of superparamagnetic relaxation in the nano particles. An exponential decrease in the superparamagnetic blocking temperature, with increasing chromium concentration, is observed for these samples.

Isothermal solidification during transient liquid phase bonding of Inconel 738 superalloy

An investigation was carried out on transient liquid phase brazing of IN-738 superalloy with Ni–Cr–B filler. Conventional models used to model the Transient Liquid Phase (TLP) bonding process assume that boride precipitation does not occur during the joining process. However, a significant deviation from this assumption was observed in all brazed samples as extensive intragranular and intergranular precipitation of chromium and boron rich particles was observed to occur within the base alloy in regions beside the braze/ base metal interface. Application of two diffusion models to the isothermal solidification stage was successful in reasonably predicting the time required to achieve complete isothermal solidification of the liquid insert, which is vital in preventing the formation of deleterious centreline eutectic. Diffusion analysis showed that the boron rich particles formed as a result of substantial solute diffusion into the base metal before equilibration of the liquid–solid phases.

Supercritical water oxidation of wastewater from LCD manufacturing process: kinetic and formation of chromium oxide nanoparticles

Supercritical water oxidation (SCWO) has been known as one remarkably effective process for the treatment and disposal wastewater. In this work, SCWO of the wastewater from a liquid crystal display (LCD) manufacturing plant was carried out in an isothermal, isobaric tubular flow reactor with H 2O 2 as an oxidant. All experiments were performed at pressures from 25 to 29 MPa and at temperatures from 396 to 615 °C. At the reactor entrance, the initial chemical oxygen demand (COD) concentrations of wastewater were between 126 and 19,428 mg/l; the oxidant concentrations were between 4.66 × 10 −3 and 1.34 × 10 −1 mol/l. During the SCWO process, in situ formation of chromium oxide nanoparticles (α-HCrO 2 and Cr 2O 3) was found by decomposition of ammonium dichromate, which is contained in wastewater. Based on scanning electron microscope and electrophoretic light scattering analyses for particle size, non-faceted crystalline chromium particles are obtained in the range 200–400 nm. The COD conversion rate was increasing with higher wastewater and oxidant feed concentration. An assumed first-order global power-law rate expression was determined with activation energy of 21.71 ± 1.67 kJ/mol and a pre-exponential factor of 46.84 ± 1.52 s −1 to a 95% confidence level. By taking into account the dependence of the reaction rate on wastewater and oxidant concentration, a global power-law rate expression was regressed from the complete set of data. The resulting activation energy were 47.79 (±1.52) kJ/mol; the pre-exponential factor was 2.78 (±0.71) × l0 2 l 1.075 mmol −0.075 s −1; and the reaction orders for wastewater (based on COD) and oxidant were 1.01 ± 0.01 and 0.065 ± 0.01, respectively.

Hertzian crack analysis in alumina–chromium composites

Ceramic metal composites are of interest for their good resistance to crack propagation. We have prepared different kinds of alumina chromium composites, observed their microstructures and made an analysis of Hertzian cracks in order to identify the principle parameters of crack propagation in relation with the metallic phase size and distribution in the matrix. The crack is analysed at two scales, a macroscopic one to estimate the fracture toughness from the overall crack and a microscopic one to study, at the local level, the influence of the metallic phase on crack propagation. Using macroscopic models the fracture toughness estimation highlights the benefit of the presence of chromium particles. Observations and measurements made on the crack path and metallic phase, from the microstructure analysis, combined with the knowledge of the residual stress state, provide the principal parameters governing crack propagation in these composites.