Product Chromium Research Articles

THE ROLE OF SULFUR-CONTAINING AMINO ACIDS IN THE PREVENTIVE NUTRITION OF WORKERS IN CONTACT WITH CHROMIUM

In the world, a large number of workers are exposed to fumes, mists and dusts containing Chromium and its compounds. One of the ways to prevent chromium intoxication is the enrichment of food rations with substances that have antioxidant and complexing ability. Attention is focused on the recommendations on the use of sulfur-containing amino acids and sulfur-rich proteins in the composition of food products for the prevention of intoxication in workers who come into contact with chromium in production. The mechanism of reduction of hexavalent chromium compounds by cysteine was considered. It has been shown that the process of reduction of chromates with cysteine is accompanied by the oxidation of cysteine to cystine and subsequent complexation with trivalent chromium. The structure of chromium III cystinate was confirmed by IR and electron spectroscopy and elemental analysis. It has been established that in the formed chelate complex [Cr(SNO2C3H6)6Cr], chromium (III) has a bond with cystine through the amino and carboxyl groups, LD50 is 2100 mg/kg and is less toxic than inorganic chromium (III) salts. The article analyzes protein raw materials rich in cysteine, which can be recommended to satisfy the daily requirement of cysteine, or to reduce chromium intoxication of workers working in a work area with a high content of chromium salts.

Studies on self-assembly hydrothermal fabrication and thermal stability of Chromium oxyhydroxide nanomaterials synthesised from Chromium oxide colloids

Chromium oxyhydroxide nanomaterials with narrow size-distribution were synthesised through a simple hydrothermal method. Experimental conditions, such as reaction duration and pH values of the precipitation process and hydrothermal treatment played important roles in determining the nature of the final product chromium oxyhydroxide nanomaterials. The effect of these synthesis parameters were studied with the assistance of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and thermogravimetric analyses. This research has developed a controllable synthesis of Chromium oxyhydroxide nanomaterials from Chromium oxide colloids.

Skin Deposition of Nickel, Cobalt, and Chromium in Production of Gas Turbines and Space Propulsion Components

Skin exposure to nickel, cobalt, and chromium may cause sensitization and allergic contact dermatitis and it is known that many alloys and platings may release significant amounts of the metals upon contact with skin. Occupational exposure to these sensitizing metals has been studied in different settings with regards to airborne dust and different biological end points, but little is known about deposition on skin from airborne dust and direct contact with materials containing the metals. In this study, skin deposition was studied in 24 workers in an industry for development and manufacturing of gas turbines and space propulsion components. The workers were employed in three departments, representing different exposure scenarios: tools sharpening of hard metal items, production of space propulsion structures, and thermal application of different metal-containing powders. A novel acid wipe sampling technique was used to sample metals from specific skin surfaces on the hands and the forehead of the workers. Total amounts of nickel, cobalt, and chromium were measured by inductively coupled plasma mass spectrometry. The result showed that nickel, cobalt, and chromium could be detected on all skin surfaces sampled. The highest level of nickel was 15 microg cm(-2) h(-1), the highest for cobalt was 4.5 microg cm(-2) h(-1), and for chromium 0.6 microg cm(-2) h(-1). The three departments had different exposures regarding the metals. The highest levels of nickel on the skin of the workers were found in the thermal applications department, cobalt in the tools sharpening department, and chromium in the space propulsion components department. In conclusion, the workers' exposure to the metals was more likely to come from direct skin contact with items, rather than from airborne dust, based on the fact that the levels of metals were much higher on the fingers than on the back side of the hands and the forehead. The skin exposure levels of nickel and cobalt detected are judged capable to induce sensitization and elicit allergic contact dermatitis.

First Direct Detection of Chromium(IV) as a Long Lived Intermediate in the Oxidation of Methanol by Chromium(VI)

Reduction of chromium(VI) by excess methanol in solutions buffered by 2-ethyl-2-hydroxy butanoic acid and its sodium salt proceeds through a 2-electron path to produce pink chromium(IV). With the progress of this reaction, a slow oxidation of the product chromium(IV) by reactant chromium(VI) takes place. When all the chromium(VI) is consumed, the chromium(IV) undergoes very slow disproportionation to chromium(V) and chromium(III). The formation of chromium(IV) is accelerated by both 2-ethyl-2-hydroxy butanoate ion and hydrogen ion.

An internal synthesis method for producing a mullite–chromium carbide composite

In situ formation of chromium carbide in mullite matrix through the reaction of Cr2O3, SiC, and Al2O3 has been studied. Three different chromium compounds, Cr3Si, Cr3C2, Cr7C3, and mullite were formed. The Cr3Si particles formed first and the Cr7C3 phase was only dominant above 1600 °C. The Cr3C2 phase was the main product chromium carbide at temperatures ranging from 1450–1550 °C. The mullite phase formed concurrently through the reaction of SiO2 with Al2O3. SiO2 is the product of the reaction between Cr2O3 and SiC. The composite hot-pressed at 1450 °C in argon gives a flexural strength and fracture toughness up to 407 MPa and 3.8 MPa m1/2, respectively.