Addition Of Chromium Research Articles

Effects of hexavalent chromium on phytoplankton and bacterioplankton of the Río de la Plata estuary: an ex-situ assay.

We examined the responses of the phytoplankton and the bacterioplankton of the freshwater zone of the Río de la Plata estuary when exposed to an addition of hexavalent chromium (Cr+6). The planktonic community from a coastal site was exposed to a chromium increase of 80μgL-1 for 72h in laboratory conditions. The results showed a decrease in the concentration of Cr+6 by 33% in the treatments, along with significant decreases in chlorophyll-a (63%), the chlorophyll-a:pheophytin-a ratio (33%), oxygen production (37%), and in the total density of the phytoplankton (15%). The relative abundance of chlorophytes and diatoms decreased, while the cyanobacteria thrived. Finally, the total bacterial density and the density of viable bacteria decreased. These results show that even small increments in Cr+6 can cause significant effects on the phytoplankton and bacterioplankton, which could potentially affect other trophic levels of the community, risking alterations of the entire ecosystem.

Effects of Cr doping in the structural and optoelectronic properties of Cu2ZnSnS4 (CZTS) thin film by magnetron co-sputtering

In this letter, we report the structural and optoelectronic properties of chromium-doped Cu2ZnSnS4 (CZTS:Cr) deposited by co-sputtering technique. Addition of chromium was observed to deteriorate the Cu2ZnSnS4 crystallinity as well as inducing the growth of cubic-ZnCr2S4 secondary phase. Grain size as large as 0.5 µm was observed for the doped sample. Bandgap was found to vary (1.51–1.70 eV), whereas the deep level defect state was calculated to be positioned at 0.20–0.33 eV above the valence band maximum (VBM) depending on the chromium concentration.

Penambahan Kromium Organik pada Pakan Yang Dibatasi Terhadap Performa Produksi Puyuh

The aim of this research was to know the effect of organic chromium on feed which was limited to quail phase pre-layer production performance. The experimental design of the study was a Completely Randomized Design (CRD) consisting of twelve treatments, three replicates, and each replication consisted of five quails. Data were analyzed by variance analysis then tested continued with the Least Significance Different (LSD). The treatments were P0R1 (adlibitum feed, energy metabolism (EM) 2,900 kcal/kg, protein 22%), P0R2 (adlibitum feed, EM 2,800 kcal/kg, 23% protein), P1R1 (restriction feed 10% of adlibitum, EM 2,900 kcal/kg, 22% protein), P1R2 (restriction feed 10% of adlibitum, EM 2,800 kcal/kg, 23%.protein), P2R1 (restriction feed 20% of adlibitum, EM 2,900 kcal/kg, 22%protein), P2R2 (restriction feed 20% of adlibitum, EM 2,800 kcal/kg, 23% protein), P0R1Cr (adlibitum feed, EM 2,900 kcal/kg, 22% protein with adding 2 ppm chromium), P0R2Cr (adlibitum feed, EM 2,800 kcal/kg, 23% with adding protein 2 ppm chromium), P1R1Cr (restriction feed 10% of adlibitum, EM 2,900 kcal/kg, 22% protein with adding 2 ppm chromium), P1R2Cr (restriction feed 10% from adlibitum, EM 2,800 kcal/kg, 23% protein with adding 2 ppm chromium), P2R1Cr (20% restriction feed of adlibitum, EM 2,900 kcal/kg, 22% protein with adding 2 ppm chromium) and P2R2Cr (restriction feed 20% from adlibitum, EM 2,800 kcal/kg, 23% protein with adding 2 ppm chromium). Parameters observed included feed intake, body weight gain, and feed conversion. The results showed that the addition of organic chromium to the limiting feed had a significant effect (P<0.01) on feed consumption, body weight gain, and feed conversion. Organic chromium might give 2 ppm on feed that was limited to 10% of EM 2,900 kcal/kg adlibitum, 22% protein.

Porous ceramics based on yttrium and scandium-cerium doped ZrO2 with fluorite structure: Impact of chromium on conductivity

The total conductivity of the compositions containing Zr0.89Sс0.1Ce0.01О2 or Zr0.92Y0.08О2 powders and Cr2O3 was studied to evaluate a potential impact of the chromium deposition on the surface of electrolyte grains in the porous composite cathode. The compositions were fabricated in the corresponding ratios: (100-х) mol% Zr0.89Sс0.1Ce0.01О2 - х mol% CrO1.5 (10Sc1CeSZ-Cr) and (100-х) mol% Zr0.92Y0.08О2 - х mol% CrO1.5 (8YSZ-Cr) with х = 0.25, 0.5, 1, and 2. Porous ceramic Zr0.89Sс0.1Ce0.01О2 with 49% relative density exhibits higher conductivity than Zr0.92Y0.08О2. In general, a small addition of chromium decreases the conductivity of Zr0.89Sс0.1Ce0.01О2 and Zr0.92Y0.08О2, although the values of the conductivity change in a non-linear way, reaching minimum for 10Sc1CeSZ-Cr1 and 8YSZ-Cr0.25 compositions. This is accompanied by the decrease in the activation energy of the conductivity from 1.35 eV to 1.19 eV in the 10Sc1CeSZ-Cr series and from 1.28 eV to 1.19 eV in the 8YSZ-Cr series with the rise in the chromium content. Evolution of the conductivity values is associated with the interstitial incorporation of chromium into the fluorite structure as well as with its segregation on the surface of grains and grain boundaries. Chromium coexists in the multivalent states (Cr3+ and Cr6+) on the surface of grains. Considering a long-term operation of the SOFC system, one could suggest that Zr0.89Sс0.1Ce0.01О2 will show more promising transport characteristics in the presence of the chromium containing interconnects.

Dynamic Strain Aging Phenomena and Tensile Response of Medium-Mn TRIP Steel

Dynamic strain aging (DSA) and rapid work hardening are typical behaviors observed in medium-Mn transformation-induced plasticity (TRIP) steel. Three alloys with manganese ranging from 10.2 to 13.8 wt pct with calculated room temperature stacking fault energies varying from − 2.1 to 0.7 mJ/m2 were investigated. Significant serrations were observed in the stress-strain behavior for two of the steels and the addition of 4.6 wt pct chromium was effective in significantly reducing the occurrence of DSA. Addition of chromium to the alloy reduced DSA by precipitation of M23(C,N)6 during batch annealing at 873 K (600 °C) for 20 hours. Three distinct DSA mechanisms were identified: one related to manganese ordering in stacking faults associated with e-martensite and austenite interface, with activation energies for the onset and termination of DSA being 145 and 277 kJ/mol. A second mechanism was associated with carbon diffusion in γ-austenite where Mn-C bonding added to the total binding energy, and activation energies of 88 and 155 kJ/mol were measured for the onset and termination of DSA. A third mechanism was attributed to dislocation pinning and unpinning by nitrogen in α-ferrite with activation energies of 64 and 123 kJ/mol being identified. Tensile behaviors of the three medium manganese steels were studied in both the hot band and batch annealed after cold working conditions. Ultimate tensile strengths ranged from 1310 to 1404 MPa with total elongation of 24.1 to 34.1 pct. X-ray diffraction (XRD) was used to determine the transformation response of the steels using interrupted tensile tests at room temperature. All three of the processed steels showed evidence of two-stage TRIP where γ-austenite first transformed to e-martensite, and subsequently transformed to α-martensite.

Three-body abrasive wear behaviour of metastable spheroidal carbide cast irons with different chromium contents

Abstract The effect of heat treatment and chromium contents (up to 9.1 wt.%) on the wear resistance of spheroidal carbide cast iron (9.5 wt.% V) was studied using optical and scanning electron microscopy, X-ray diffractometry, dilatometry and three-body abrasive testing. It was found that quenching from 760 °C and 920 °C improved the alloys’ wear resistance compared to the as-cast state due to the formation of metastable austenite transforming into martensite under abrasion. The wear characteristics of alloys studied are 1.6 – 2.3 times higher than that of reference cast iron (12 wt.% V) having stable austenitic matrix. Chromium addition decreases surface damage due to the formation of M 7C3 carbides, while it reduces wear resistance owing to austenite stabilization to abrasion-induced martensite transformation. The superposition of these factors results in decreasing the alloys’ wear behaviour with chromium content increase.

Concentration of Point Defects in Metal Deficient Zn1-yO

AbstractIn this paper the doping effect has been used to indirectly calculate point defect concentration in metal-deficient Zn1-yO zinc oxide. The proposed method consists of determining the concentration of prevailing point defects in the studied oxide from the influence of chromium addition on the point defect situation in doped zinc oxide. It has been found that chromium addition into the crystal lattice of zinc oxide changes its ionic disorder, enabling calculation of predominant point defects in Zn1-yO. The concentration of predominant point defects in Zn1-yO is the following function of oxygen pressure and temperature: $$\eqalign{\left[{\,{{\rm V''}_{\rm Zn}}\,} \right]\, &= \,{1 \over 2}\left[{\,{\rm h^ \bullet}\,} \right]\, = \,0.63 \cdot \,\rm p_{{O_2}}^{1/6}\, \cdot {K^{1/3}}\,_{}^{}\, \cr& = \,\,5.6 \cdot {10^{- 3}} \cdot \,\rm p_{{O_2}}^{1/6}\, \cdot \exp \left({- {{27\,kJ/mol} \over {RT}}} \right)\cdot}$$

Effects of chromium on the morphology and mechanical properties of Fe2B intermetallic in Fe-3.0B alloy

In this work, the effects of chromium addition on the morphology and mechanical properties of Fe2B in Fe-3.0B alloy have been systematically investigated by a combination of experimental observations and the first-principles calculations. The results indicate that, with chromium addition in Fe-3.0B alloy ranging from 0 to 2.5 wt%, the average grain size of the boride firstly decreases and then increases slightly, mainly attributed to the volume fraction of coarse block boride. The nanoindentation hardness H of the boride remains almost constant while the elastic modulus E r firstly drops and then rises. Accordingly, the H/E r of the boride achieves a peak value at the chromium addition of 2.0 wt%, where the highest toughness is obtained. High-resolution transmission electron microscopy (HRTEM) observation demonstrates that the lattice of borides evolves from tetragonal to orthorhombic ((Fe, Cr)2B) after chromium addition, in good accordance with the calculation results. During the lattice evolution, a shrinkage of B–B bond along [002] direction is simultaneously revealed. The inherently weak B–B bond can be strengthened, which improves fracture toughness of Fe2B.

Effect of molybdenum addition on hardenability of chromium-boron steels used for press hardening applications

Two laboratory heats of low-Carbon low-alloy steels, one with boron and chromium additions and other with boron, chromium and molybdenum additions were made and cast into pencil ingots. These ingots were hot-rolled to 2 mm sheets suitable for press hardening application in an experimental rolling mill. A detailed study was made on the effect of various alloying elements on the microstructure and mechanical properties of these steels. A significantly higher hardness (~496 VHN), yield strength (~1137 MPa) and ultimate tensile strength (~1673 MPa) with comparable elongation (~6%) could be achieved in the as rolled and water-quenched Mo-Cr-B steel in comparison to Cr-B steel under similar processing condition. Moreover, a reduction of critical cooling rate by10?C/s was observed in this steel to obtain fully martensitic structure. The combined addition of boron, chromium and molybdenum was found to be more effective than that of boron and chromium in enhancing the microstructure and mechanical properties of boron-added steels. Additionally, a few hot compression tests were carried out to simulate the press hardening process of these experimental steels. It was found that one of the press hardening process parameters, viz., prior strain had a greater impact on the transformation behaviour of Cr-B and Mo-Cr-B steels during cooling.

Effects of Cr on anodising and microstructure of cast aluminium alloys

Aluminium has been widely used in several applications due to its outstanding properties such as light weight and high corrosion resistance. However, development of surface mechanical properties and corrosion resistance is necessary for many applications especially in severe environment. The improvement of surface properties of commercial 6063 aluminium alloy by aluminium anodizing process was studied in this research. Chemical compositions of aluminium are important factor on aluminium matrix and properties of anodized layer. The addition of chromium in commercial 6063 aluminium alloy with different chromium amounts were prepared by ingot metallurgy. The effects of chromium addition on the microstructure, and corrosion properties were investigated. The minimum surface roughness of ingot obtained is 2.44 μm (Rq) can be seen inspecimen of 100-g chromium addition. The chromium amount also plays important role on corrosion resistance. Passive film was found in chromium-added anodized samples. Owing to the microstructure, addition of chromium leads to formation of intermetallic compounds in the aluminium matrix. These compounds are responsible for changes in microstructure and corrosion properties of bulk aluminium and anodized layer.

Experimental and numerical investigations of the critical values of J-integral for the steel of steam pipelines

Steel grade 14MoV6-3 is a low-carbon microalloyed steel with addition of chromium and molybdenum. This grade is designed mainly for power industry applications, withstanding operating at elevated temperatures. In this paper, mechanical properties of steel grade 14MoV6-3 and methodology of calculation of critical values of the J-integral are presented. The level of damage is determined by analyzing the virgin material of the same grade. The focus of presented investigation is on the experimental J-integral determination, where critical values of the J-integral (JIC) are compared with the values obtained by using the finite element methods (FEM). FEM model was defined on the basis of experimental conditions and obtained numerical values should confirm our experimental results.

An in-vitro bioactive, structural and degradation studies on B2O3–SiO2–P2O5–Na2O–CaO glass system incorporated with chromium ions

Calcium borosilicate glasses with composition 43B2O3–5SiO2–2 P2O5–20 Na2O–(30–x) CaO–x Cr2O3 with 0 ≤ x ≤ 1 mol%, have been prepared by the conventional melt-quenching technique. The samples were characterized by FTIR, UV-vis-absorption and X-ray diffraction techniques. The physico chemical properties such as density, molar volume, oxygen packing density and chromium ion concentration were also evaluated. The data obtained indicated that the Cr2O3 will break the bonds of the glass network by the creation of non bridging oxygens (NBO’s); as a result an increase in the volume of the glass network due to loosely packed structure. Results from FTIR, UV-vis.-spectroscopy studies indicated that Cr2O3 acted as a network modifier, by converting four coordinated to three coordinated boron atoms. In this context, we have examined the bioactivity of various concentrations of Cr2O3 doped glasses with the help of simulated body fluid (SBF). After immersion of glasses in the SBF, formation of hydroxyapatite layer on the surface was confirmed by XRD, FT-IR and SEM-EDS analysis. The solubility test data indicated that a clear increase of degradability of glass and significant change in the pH of the body fluid was observed with the addition of chromium. The results showed that partial substitution of Cr2O3 with CaO positively influenced the bioactivity. Thus bioactivity is increased with increase in the content of Cr2O3.

Experimental study on mechanical and corrosion characteristics of nab alloy with the addition of chromium

The issue of corrosion is a major problem on equipment failure and damage in industrial that would affect the safety and efficiency of the equipment. Especially, materials used in marine environments have to withstand corrosion and need more hardness to withstand corrosion. Nickel–aluminum bronze (NAB) alloys show good corrosion resistance under marine conditions. Therefore material requirements to withstand such a high corrosive environment are most important. Along with these, cost effectiveness also considered in the usage of material. Many papers gives the corrosion resistance of behavior of NAB alloys in sea water or 3.5M NaCl solution in detail manner. But the alternate material to NAB is not studied as copper is the material shows very high corrosion resistance in sea water. In order to enhance the properties of NAB alloy, chromium is added additionally and excluding iron, manganese, bronze, etc of the NAB alloy. This paper will be focusing on the influence of chromium addition to the aluminum nickel alloy in the corrosion resistance properties and hardness. Chromium is added in 4%, 8% and 12% through powder metallurgy route. The specimen prepared for the corrosion testing by sintering and hot – extrusion. The electro-chemical corrosion test was carried out in Potentiostat in order to find out the corrosion properties of the alloys. The corrosion properties were increased than the available alloy composition of ASTM B505M – 14. Further, the micro-vicker’s is done which shows that the micro-hardness also has got increased due to the addition of chromium. The main aim of the paper is to find an alternate material which withstands high corrosive environment especially in salt water and also high strength.

Hot-dip Aluminizing of Low Carbon Steel in Al & Al-5wt % Cr Baths

Hot dip aluminizing of low carbon steel is carried out in pure aluminium bath and Al-5wt% Cr bath. The coating is characterized by scanning electron microscopy and chemical composition of the coating is analysed by EDS (energy dispersive spectroscopy) attached to SEM. The coating consists of three regions, viz., outer aluminium topcoat, intermediate Fe-Al intermetallics layer and the base alloy. The intermetallics layer consists of FeAl3 and Fe2Al5 phases. Fe2Al5 is the major phase in the intermetallics layer. The growth kinetics of intermetallics layer is parabolic in nature implying that it is diffusion controlled. Addition of chromium forms Al7Cr dispersed intermetallics phases in the aluminium topcoat. Addition of chromium has no influence on the morphology of the intermetallics layer. Scratch resistance of the coating is carried out to evaluate the scratch hardness of the coating. Chromium addition improves scratch resistance of the coating.

Effect of hard faced Cr-alloy on abrasive wear of low carbon rotavator blades using design of experiments

Aversive wear of tillage tool is major problem faced all-over the world. The surface modification techniques are used to improve surface properties of target surface. Hard-facing is effective technique for enhanced the surface properties of tillage tool and metallic components. The performance of tillage tool and quality of work are highly influenced by the aversive wear. In the present study the wear resistance of modified and regular rotavator blades in laboratory and in actual working field of sandy soil. Hardfacing is used as surface modifying technique and Cr based electrode are used for the investigation. Experimentation has conducted to evaluate the effect of chromium alloys on mechanical properties of base material. Addition of chromium increases the surface hardness of blades. ASTM G-99 standard wear testing method is used to study wear resistance of modified and regular blades. Taguchi L9 array of to optimize the laboratory investigation used in present work. Wear performance of unhardfaced and hardfaced blades is examined after fixed interval of time in term of weight loss. The wear rate in the field tests was found to be significantly different statistically than laboratory test run. Hardfaced blades shows higher wear resistance then regular blades of rotavator.

Using chromate to investigate the impact of mineral-organic contact time on the surface reactivity of goethite.

Chromate was used as a chemical probe to investigate the impact of mineral-organic contact time on the surface reactivity of two different sizes of goethite particles. A series of goethite-chromate sorption batch reactions were conducted in the presence and absence of Suwannee River humic acid (HA) and natural organic matter (NOM) using nano- and micro-scale goethite particles. In experiments with added organics the amount of time allowed for goethite-organic matter interaction (i.e. contact time) was varied from less than 1 minute, up to 24 hours prior to the addition of chromate. Results indicated that nano- and micro-scale goethite in the absence of organics sorbed nearly identical amounts of chromate on a per mass basis, despite the greater surface area of the smaller particles. Results also indicated that the presence of ∼10 mg L-1 of HA and a contact time of less than 1 minute reduced the amount of chromate sorbed by both nano- and micro-scale goethite. Increasing the contact time resulted in greater decreases in chromate sorption. Experiments using NOM produced similar results. While chromate sorption was most rapid during the first hour of the experiments, goethite particles continued to sorb additional chromate over a period of up to 7 days. Additionally, a noticeable impact on chromate sorption due to increased contact time was present over that time period.

Effect of Chromium Addition on the Coarsening of Cu-particle in Ferritic Stainless Steels

Effect of Chromium Addition on the Coarsening of Cu-particle in Ferritic Stainless Steels

Effect of alloy composition on hot deformation behavior of some Al-Mg-Si alloys

The hot flow stress behavior of three Al-Mg-Si alloys was determined by performing hot deformation compression tests on a Gleeble 3500 thermomechanical simulator over the temperature range 400 °C–550 °C and at strain rates from 0.01 s−1 to 10 s−1. Using the hyperbolic sine constitutive model, constitutive parameters for prediction of the hot flow stress behavior of these different alloys were determined. The effect of chromium (Cr) addition and increased Mg-Si content on the average steady flow stress, constitutive and strain rate sensitivity (m) parameters was determined. For deformation at low strain rates (0.01–1s−1), the alloy containing 0.2 wt % Cr exhibited higher average steady flow stress than the alloy with similar Mg-Si content and no Cr addition. The addition of 0.2 wt % Cr and an increase in Mg-Si content were observed to result in a decrease of the strain rate sensitivity parameter (m) and an increase in the activation energy for hot deformation. The predictive accuracy of the developed models was demonstrated by comparing the predicted and experimental flow stress behavior of alloy 3 at deformation conditions different from the temperature and strain rate conditions used to develop the models parameters. Results indicate that the developed model can accurately predict the alloy behavior at strain rate and temperature conditions beyond the range of model development.

Effect of Cr-N codoping on structural phase transition, Raman modes, and optical properties of TiO2 nanoparticles

Noncompensated cation-anion codoping in TiO2 nanoparticles has been achieved by a chemical synthesis route. Significant reduction in the optical bandgap and enhancement in the absorption of visible light have been observed. Structural phase transformation has been tracked in detail as a function of doping and heat treatment temperature. Anatase to rutile phase transition temperature for doped samples was higher in comparison to the pure TiO2 nanoparticles. Nitrogen and chromium addition increases the phase transformation barrier, where the effect of the former dopant is of more significance. The Raman results showed an increase in the oxygen content with higher post annealing temperatures. With Cr incorporation, the peak associated with the Eg mode has been found to shift towards a higher wave number, while with nitrogen incorporation, the shift was towards a lower wave number. A decrease in reflectance with N co-doping for all samples, irrespective of phase and annealing temperatures, has been observed. In compositions with nitrogen of the same content, bandgap reduction was higher in the rutile phase in comparison to the anatase phase. In general, overall results revealed that with a higher loading fraction of ammonia, the N content increases, while Cr addition prevents nitrogen loss even up to high post annealing temperatures, i.e., 850 °C.

Effect of Intensive Cooling of Alloy AZ91 with a Chromium Addition on the Microstructure and Mechanical Properties of the Casting

AbstractThe work presents the results of the investigations of the effect of intensive cooling of alloy AZ91 with an addition of chromium on the microstructure and mechanical properties of the obtained casts. The experimental castings were made in ceramic moulds preliminarily heated to 180°C, into which alloy AZ91 with the addition was poured. Within the implementation of the research, a comparison was made of the microstructure and mechanical properties of the castings obtained in ceramic moulds cooled at room temperature and the ones intensively cooled in a cooling liquid. The kinetics and dynamics as well as the thermal effects recorded by the TDA method were compared. Metallographic tests were performed with the use of an optical microscope and the strength properties of the obtained castings were examined: UTS (Rm), elongation (A%), and HB hardness.