With the stabilization of Korea’s industrialization, it has become interested in the efficient use of rare metals, climate change and industrial environment and safety etc. It is thus making efforts to implement economic policies that address such issues. Therefore it is necessary to understand the demand, supply and use of metal materials. Since 2010, the Korean government has developed the integrated material flow methodology and has been trying to examine the demand, supply and use of metal materials. In 2013, the Korean government surveyed the material flow of chromium. Material flow analysis and environment emission of chromium were investigated 8 steps; (1) raw material, (2) first process, (3) Intermediate product, (4) End product, (5) Use/accumulation, (6) Collection, (7) Recycling, (8) Disposal. Chromium was used for stainless steel, alloy steel, coated sheets, refractory material and coating materials. Recycling was done mainly in use of stainless steel scrap. To ensure efficient use of chromium, process improvement is required to reduce the scrap in the intermediate product stage. In the process of producing of the products using chromium, it was confirmed that chromium was exposed to the environment. It requires more attention and protection against environment emission of chromium.

This study was conducted to investigate the effects of Chromium-Methionine (Cr-Met) chelate feeding for different durations on growth and carcass characteristics in the late fattening stage of Holstein steers. Nine Holstein steers were randomly assigned to three dietary treatments (3 head per treatment) including Non Cr-Met chelate feeding (NCM, av. BW of 433.3 kg), Cr-Met chelate feeding for 2 months (2CM, av. BW of 459.6 kg), and Cr-Met chelate feeding for 4 months (4CM, av. BW of 490.0 kg), respectively. The feeding amount of Cr-Met chelate to an animal was limited to 400 ppb/day. Dry matter intake showed no differences among all the treatments (p>0.05). Average daily gain was also higher in the animals fed Cr-Met chelate diets than NCM (p<0.05). Carcass weights were also observed to be higher in Cr-Met chelate feeding treatments, especially in 4CM compared with other treatments (p<0.05). Although no significant differences were observed on back fat thickness and rib eye area(p<0.05), but 4CM showed much higher effects than NCM and 2CM. Marbling score meat color, fat color, texture, and maturity were not affected by treatments (p>0.05). The variations in meat quality were smaller in 4CM compared to other treatments. 4CM showed higher total and net income than other treatments (p<0.05). Therefore, the current study concluded that Cr-Met chelate supplementation for 4 months could increase daily gain, carcass characteristics, and profitability of Holstein steers in the late fattening stage.

말똥성게 (Hemicentrotus pulcherrimus)의 생식세포 및 pluteus 유생을 이용하여 중금속인 Arsenic (As)와 Chromium (Cr)이 정상 수정률 및 배아 발생률에 미치는 독성 영향을 조사하였다. H. pulcherrimus의 수정률 및 배아 발생률에 미치는 As와 Cr의 독성은 6.25, 12.5, 25, 50, 100 ppb의 농도에서 조사하였다. 0.5 M KCl 용액을 이용하여 방란 및 방정을 유도하였고, 정상 수정률 및 배아발생률은 수정 후 각각 10분 및 64시간째 관찰하였다. As와 Cr을 첨가하지 않은 대조구에서 정상 수정률과 배아 발생률은 각각 94%와 93% 이상을 나타냈다. 이들 중금속 첨가에 의해 수정률은 아무런 변화가 나타나지 않았지만 배아 발생률은 농도 의존적 감소하는 것으로 나타났으며, As의 첨가에 의해 배아 발생률은 6.25 ppb에서 유의적으로 감소하였으며 (P⁄0.01), Cr의 경우는 25 ppb에서 유의적인 감소를 나타냈다 (P⁄0.05). H. pulcherrimus의 정상 배아 발생률에 대한 LOEC는 As의 경우는 6.25 ppb를 Cr은 25 ppb를 나타냈다. 이들 연구결과로 해양생태계 내에서 As가 6.25 ppb, Cr이 25 ppb를 초과하는 농도일 때는 H. pulcherrimus와 같은 무척추동물의 정상부화율은 급격히 감소할 것으로 판단된다. 본 연구결과를 바탕으로, H. pulcherrimus의 정상 배아 발생률을 이용한 생물학적 평가방법은 중금속과 같은 유해물질에 대한 해양생태계의 영향을 판단하기 위한 시험방법으로 유용하게 이용될 수 있을 것으로 판단된다.

One of the trace constituents included in cement clinker, chromium, has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects the human body negatively. The purpose of the present study was to investigate leaching properties of water-soluble hexavalent chromium by different manufacturing conditions of cement clinker. Raw materials were prepared to add different SiO2, Al2O3 and Fe2O3 sources. After the raw materials, such as limestone, sand and clay, iron ore was pulverized and mixed, and the raw meal was burnt at 1450˚C in a furnace with an oxidizing atmosphere. Leaching of soluble hexavalent chromium showed a tendency to decrease with an increasing LSF and IM. However, leaching of soluble hexavalent chromium increased with an increasing S.M. Alkali contents of iron source minerals is closely related to the leaching properties of soluble hexavalent chromium. Green sludge has the highest content of alkali added; leaching of water-soluble hexavalent chromium was mostly high. In order to reduce the water-soluble hexavalent chromium in cement, reducing the alkali content in raw materials is important.

Since it was developed by Joseph Aspdin, cement has been a common construction materials up to the present time.However, there are trace constituents in cement clinker. One of the trace constituents included in cement clinker, chromium,has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects thehuman body negatively. The aim of the present study was to investigate the concentration of water-soluble hexavalent chromiumin cement clinker by using industrial by-products. For that reason, raw materials were prepared to add different SiO2 , Al2O3,and Fe2O3 sources. After the raw materials such as the limestone, the sand and the clay, iron ore was pulverized and mixed,and the raw meal was burnt at about 1450oC in a furnace with an oxidizing atmosphere. The part in the raw materials of theclinker was substituted with slag, sludge, etc. and this was used to manufacturing cement clinker. To investigate the water-soluble hexavalent chromium content in clinker, raw meal was prepared by changing the modulus, the type, and the contentof clinker materials and tested concentrations of hexavalent chromium in the clinkers. To determine Cr+6 formation of theclinker, tests were done with raw meals adding chromium by using different industrial by-products. Consequently because thechromium was to be included in the raw materials of the clinker, production of Portland cement clinker was included with thechromium. Also, the chromium was converted into hexavalent chromium in the burning process.

This study aimed at investigating the gene expression profile in basal ganglia of hexa-valence chromium exposed rat based on cDNA array analysis. For cDNA array, Sprague-Dawley male rats (300 ± 25 g) were administrated with 15 mg/kg B.W/day of potassium dichromate by gavage (0.3 ml) dissolved in saline for 10 days (n=5). For dose-related gene expression analysis, rats were administrated with 0, 1, 5 mg/kg B.W/day of potassium dichromate for 10 days. Control rats were administrated with equal volume of saline (n=5). For cDNA array analysis, RNA samples were extracted from brain tissue and reverse-transcribed in the presence of [α³²P]-dATP. Membrane sets of the Atlas array II and Toxicology array kits were hybridized with cDNA probe sets. RT-PCR and Northern blot hybridization methods were employed for validation and assessment of the dose-related gene expression profile, respectively. Among the 2352 cDNAs, 43 genes showed significant (>two-fold) changes in expression. 22 genes were up-regulated and 21 genes were down-regulated in the 15 mg/kg B.W/day hexa-valence chromium treated group than control. According to the Northern blot hybridization analysis, heat shock protein 47, neurodegeneration associated protein 1 and pituitary specific growth factor 1a genes were up-regulated, but Gamma-aminobutyl-acid a1 subunit, neuroligin2, brain calcium-transporting plasma membrane type ATPase genes were down-regulated even in the low-dose of hexa-valence chromium exposed group (1 mg/kg B.W/day) than control. Genes that detected in this study may be closely related to the hexa-valence chromium-induced neurotoxicity in the rat basal ganglia and addition study of these genes can give some more useful information about the neuro-toxic mechanism by hexa-valence chromium.

Chemically activated carbons were prepared from maize cobs, using phosphoric acid of variable concentration. The texturalparameters of the activated carbons were determined from the nitrogen adsorption isotherms measured at 77K. The chemistryof the carbon surface was determined by measuring the surface pH, the pHPZC and the concentration of the carbon - oxygengroups of the acid type on the carbon surface. Kinetics of Cr(VI) sorption/reduction was investigated at 303K. Two processeswere investigated in terms of kinetics and equilibrium namely; Cr(VI) removal and chromium sorption were studied at variousinitial pH (1-7). Removal of Cr(VI) shows a maximum at pH 2.5. At pH<2.5, sorption decreases because of the protoncompetition with evolved Cr(III) for ion exchange sites. The decrease of sorption at pH>2.5 is due to proton insufficiencyand to the decrease of the extent of Cr(VI) reduction. The chemistry of the surface of activated carbon is an important factorin determining its adsorption capacity from aqueous solutions particularly when the sorption process involves ion exchange.

This study was to invesigate the effect of dietary supplemention of Pozzolan, Chromium-methionine chelate and rhus verniciflua stokes additive feed on growth performance and ultrasound live body characteristics in finishing Hanwoo steer. The animal used in the experiment were a total of 17 heads and weighted 577.09±35.90㎏. The experimental diets were basal hi-lok branded only concentrat and rice straw and 4% Rhus, 0.4% Cramin and 2% Pozzolan, which additice in basal diet. Individually average daily gain was tended to decreased with treated group. Ultrasound back fat thickness and marbling score were not significantly different(p<0.05)between teratment, however Pozzolan additive treat was showed tend to increased. Longissimus muscle area was showed tended to decreased in the Pozzolan treatment.

Chromium nitride (CrN) films were deposited on silicon substrate by RF magnetron sputtering assisted by inductive coupled nitrogen plasma without intentional substrate heating. Films were deposited with different levels of bombarding energy by nitrogen ions (N+) to investigate the influence of substrate bias voltage (Vb) on the growth of CrN thin films. XRD spectra showed that the crystallographic structure of CrN films was strongly affected by substrate bias voltage. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that surface roughness and grain size of the CrN films varied significantly with bias voltage. For - 80 Vb depositions, the CrN films showed bigger grain sizes than those of other bias voltage conditions. The lowest surface roughness of 0.15 nm was obtained from the CrN films deposited at .130 Vb.

Several boride sintered bodies such as , , and were previously reported. In the present study, the sinterability and physical properties of chromium boride containing chromium carbide sintered bodies were investigated in order to determine its new advanced material. The samples were sintered at desired temperature for 1 hour in vacuum under a pressure by hot pressing. The relative density of sintered bodies was measured by Archimedes' method. The relative densities of addition of 0, 5, 10, 15 and 20 mass% composites were 92 to 95%. The Vickers hardness of the with 10 and 15 mass% composites were about 14 and 15 GPa at room temperature, respectively. The Vickers hardness at high temperature of the addition of 10 mass% composite decreased with increasing measurement temperature. The Vickers hardness at 1273 K of the sample was 6 GPa. The Vickers hardness of addition of composites was higher than monolithic sintered body. The powder X-ray diffraction analysis detected CrB and phases in containing composites.

Cr-C-Ni composites were synthesized in situ from elemental powders of Cr, Ni and C by high energy milling followed by reactive sintering. The milled powders with the grain size in nano-scale were pressed to compacts and sintered. During the following thermal treatment at first the chromium carbide was formed and then the cermets were sintered in one cycle. The interface between the binder phase and the carbide grains of the in situ composite has a good bonding strength as it is not contaminated with oxidation films or other detrimental surface reactions.

The effect of chemical composition of the sintering atmosphere on density, microstructure and mechanical properties of Fe-3%Mn-(Cr)-(Mo)-0.3%C steels is described. Pre-alloyed Astaloy CrM and CrL, ferromanganese and graphite were used as the starting powders. Following pressing in a rigid die, compacts were sintered at 1120 and in atmospheres having different ratio and furnace cooled to room temperature. It has been found that the atmosphere composition has negligible effect on the as-sintered properties of the investigated materials.

The solubility of Cr in cubic carbides in the systems WC-Co-TaC and WC-Co-ZrC has been determined using equilibrium samples. Thermodynamic calculations were used to design the alloys through extrapolations of Gibbs energy expressions. The alloys were designed to have a microstructure containing the following phases: WC, liquid, , graphite and cubic carbide. The alloys were investigated using scanning electron microscopy and analyzed using energy-dispersive X-ray spectrometry. The present work shows how the Cr solubility depends on which cubic carbide former that is present. The WC-Co-Cr-Zr alloy has no detectable amount of Cr whereas the WC-Co-Cr-Ta alloy has 12% Cr in the cubic carbide.

Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature although well-monitored sintering atmospheres are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range , due to positive effects from pore rounding, increased density and more effective oxide reduction. Astaloy CrM (Fe-3 wt% Cr-0.5 wt% Mo) with 0.6 wt% graphite added obtains an ultimate tensile strength of 1470 MPa and an impact strength of 31 J at density , after sintering at followed by cooling at and tempering.

Sintered steels are materials characterized by residual porosity, whose dimension and morphology strongly affect the fatigue crack growth behaviour of the material. Prismatic specimens were pressed at from Astaloy CrM powder and sintered varying the sintering temperature and the cooling rate. Optical observations allowed to evaluate the dimensions and the morphology of the porosity and the microstructural characteristics. Fatigue tests were performed to investigate the threshold zone and to calculate the Paris law. Moreover tests were performed to complete the investigation. Both on fatigue and samples a fractographic analysis was carried out to investigate the crack path and the fracture surface features. The results show that the Paris law crack growth exponent is around 6.0 for sintered and around 4.7 for sintered materials. The same dependence to process parameters is not found for .

Ancorsteel 4300, a high performance Cr-Si-Ni-Mo steel, was unveiled two years ago as the first in a series of powder metallurgy alloys that will simulate wrought steel compositions. Advantages of this alloy include good compressibility, high hardenability, and excellent dimensional stability. More important, however, is that this alloy has the ability to be effectively sintered at and maintain oxygen contents below 500 ppm. This unique blend of performance and processing capabilities provides static and dynamic properties that exceed those of conventional powder metallurgy alloys and approach wrought gearing materials. A second Cr-Si-Ni-Mo alloy has now been developed that offers complimentary performance levels at a lower Mo content. This manuscript reviews properties of the two chromium steels with comparisons to traditional sinter-hardened and heat-treated powder metallurgy alloys.