Addition Of Cr3 Research Articles

Influence of Cr3+ substitution on the electrical and magnetic properties of Ni0.4Cu0.4Zn0.2Fe2O4 nanoparticles

AbstractThe Ni0.4Cu0.2Zn0.4ferrites with different concentrations of Cr3+were synthesized at a low temperature (450°C) using sol–gel auto-combustion method. The X-ray diffraction analysis of the samples confirms the formation of a single-phase cubic spinel structure. The lattice constant decreases from 8.331 to 8.253 Å with an increase in Cr3+substitution. Bulk density decreases from 4.95 to 4.71 gm/cm3whereas porosity increases from 9.34% to 14.76% with an increase in Cr3+substitution. Transmission electron microscopy was adopted to determine the particle size. Particle size decreases from 19 to 13 nm with the addition of Cr3+ions. Saturation magnetization, coercivity, and other hysteresis parameters were measured using a vibrating sample magnetometer at room temperature with a maximum magnetic field of 8 kOe. Magnetization decreases from 62 to 48 emu/g, whereas coercivity increases from 65 to 180 Oe. The direct current (DC) resistivity increases from 3.62 × 106to 4.21 × 106Ω cm with Cr3+contentx. The dielectric constant (ε′) decreases with increasing concentration of Cr3+ions.

Improved Hardness of Single-Crystal ${\rm Nd}^{3+}:{\rm YAG}$ to Ionizing Radiation via Co-Doping with ${\rm Cr}^{3+}$

The proliferation of optical elements in systems that are subject to harsh ionizing radiation environments prompts the need for commercially available radiation-hard materials, such as laser materials. In the present study, changes in the material optical absorption are compared for a suite of single-crystal YAG, Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> :YAG, and Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ,Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> :YAG laser materials in response to high-dose-rate gamma radiation events. It is found that the addition of Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> yields radiation hardened material.

Effect of chromium addition on the structural, morphological and magnetic properties of nano-crystalline cobalt ferrite system

Nano-crystalline chromium doped cobalt ferrite powders have been synthesized by PEG assisted hydrothermal route. The structural, morphological and magnetic properties of the products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and vibrating sample magnetometer (VSM). X-ray analysis showed that the samples were cubic spinel. SEM images reveal that the samples' surfaces exhibit well-defined crystalline nanoparticles of spherical shapes with small agglomeration. The addition of Cr3+ ions caused a decrease in the average crystallite size, magnetization and the coercive field of the sample. The observed decreases in saturation magnetization and coercivity are explained on the bases of exchange interactions.

Role of Cr3+ ions on the microstructure development, and magnetic phase evolution of Ni0.7Zn0.3Fe2O4 ferrite nanoparticles

A series of ferrite samples with the chemical formula Ni0.7Zn0.3CrxFe2−xO4 (x=0.0–0.5) were prepared by a sol–gel auto-combustion method and annealed at 600°C for 4h. The resultant powders were investigated by various techniques, including X-ray diffractometry (XRD), vibrating sample magnetometry (VSM), and permeability studies. The prepared samples have a cubic spinel structure with no impurity phase. As the Cr3+ content x increases, bulk density and crystallite size decrease, whereas porosity increases. The saturation magnetization decreases linearly from 58.31 to 42.90emu/g with increasing Cr3+ content. However, coercivity increases with increasing Cr3+ substitution. The magnetic moments calculated from Neel's molecular-field model are in agreement in the experiment results. The initial permeability (μi) decreases with increasing Cr3+ substitution. The decrease in initial permeability (μi) is attributed to decrease in magnetization on addition of Cr3+. The real part of the permeability decreases gradually with increasing frequency in accordance with Snoek's law. The Curie temperature decreases linearly with increasing Cr3+ content.

Synthesis and electrochemical properties of Cr-doped Li3V2(PO4)3 cathode materials for lithium-ion batteries

Cr-doped Li3V2(PO4)3 cathode materials Li3V2−xCrx(PO4)3 were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li3V2(PO4)3 were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li3V2(PO4)3 has the same monoclinic structure as the undoped Li3V2(PO4)3, and the particle size of Cr-doped Li3V2(PO4)3 is smaller than that of the undoped Li3V2(PO4)3 and the smallest particle size is only about 1 μm. The Cr-doped Li3V2(PO4)3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Cr was that x=0.04 in the Li3V2−xCrx(PO4)3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2(PO4)3 cathode materials are attributed to the addition of Cr3+ ion by stabilizing the monoclinic structure.

Effect of Cross Linking Agent on Alkali/Surfactant/Polymer

AbstractAlkali/surfactant/polymer (ASP) multisystem flooding technique, which has an expansive application prospect, is one of the enhancing oil recovery (EOR) methods. By adding the organic chromium to the ASP, the molecular structure of polymer was made to change, and the capability of controlling mobility coefficient of ASP was improved. The results showed that multisystem could still keep ultra‐low interfacial tension between the multisystem and crude oil after addition of Cr3+. The resistance factor and residual resistance factor, the indicator which describes the capability of controlling mobility, upgraded strikingly. However its storage modulus and loss modulus, the indicator which describes viscoelasticity, increased. The results of physical simulation experiment indicated that this type of improved ASP could increase the recovery ratio by 4.3% compared to common ASP multisystem.

Inhibition of ferric chelate reductase in alfalfa roots by cobalt, nickel, chromium, and copper

This research was initiated to examine the influence of metal cations on ferric chelate reducing capacity of alfalfa grown in hydroponic culture under conditions of iron sufficient or iron limited conditions. In the absence of added metal ions, ferric chelate reductase was greater in plants cultivated in iron limited conditions than in plants where iron was not limiting. Ferric chelate reductase activity in alfalfa roots was inhibited in both iron limited and iron sufficient growth by 0.5 to 2.5 μM Co2+. While the addition of Cr3+ at 2.0 μM slightly inhibited ferric chelate reductase in roots of plants grown under iron limited conditions, Cr3+ at 10 μM stimulated ferric chelate reductase in roots from both iron limited and iron sufficient media. Cu2+ additions at 5 uM to hydroponic media greatly inhibits ferric chelate reductase in plants with iron limited growth while shoot growth was inhibited in both iron sufficient and iron limited growth. The addition of Ni2+ at levels greater than 5 μM to alfalfa cultures inhibits both root and shoot growth; however, at these concentrations of Ni2+ ferric chelate reductase is stimulated in iron sufficient media but reduced in iron stressed plants. Acidification of the media was observed only with iron stressed cultures and did not closely correlate with levels of ferric chelate reductase of the roots.

Isomerization ofn-butane on the SO4/ZrO2 catalyst promoted by IV Period metals

The catalytic activity of superacidic systems based on SO4/ZrO2 and modified by IV Period metals in isomerization ofn-butane was studied. At low temperatures of the reaction, the introduction of Fe3+, Sc3+, Co2+, or Zn2+ ions (1%) increases the yield of isobutane by 1.5 times due to the activation ofn-butane on the sites created by the promoting ions. The addition of Cr3+, V4+, or Mn2+ (1%) decreases the catalytic activity because of a decrease in the catalyst acidity, most likely, due to the reduction of surface sulfur species. The influence of the nature of the support and surface additives of SiO2, TiO2, and ZrO2 on the activity and selectivity of the catalytic system inn-butane isomerization was studied.

Synthesis and X-ray structure of a chromium(III)–rhodium(III) heterometallic hydrolytic dimer: [(H2O)4Rh(µ-OH)2Cr(OH2)4](Me3C6H2SO3)4·4H2O

Heterometallic chromium(III)-rhodium(III) oligomers are formed on addition of Cr3+ to alkaline Rh3+ solutions and can be separated by ion-exchange chromatography; solution characterization studies have established the existence of a bis(µ-hydroxo) dimer, [(H2O)2Rh(µ-OH)2Cr(OH2)4]4+, whose structure has been confirmed by X-ray diffraction studies on [(H2O)4Rh(µ-OH)2Cr(OH2)4](Me3C6H2SO3)4·4H2O.

Anisotropy and Magnetostriction of Cr3+ Ions in NiFe2O4 Crystals

Magnetocrystalline anisotropy constants K1 and K2 and magnetostriction constants λ100 and λ111 were determined by ferrimagnetic resonance techniques for NiFe2−xCrxO4 crystals with x=0, 0.04, and 0.07. K1 from Cr3+ ions is negative and at 0°K corresponds to −0.04 cm−1. A theoretical estimate from a spin Hamiltonian considering a trigonal field yields K1=+0.006 cm−1, which disagrees both in sign and magnitude with our experimental results. K2 at 4.2°K is of the order of 104 erg/cm3. The magnetoelastic constants b1 and b2 are decreased by the addition of Cr3+ ions.

Fluorescence of Uranium‐Activated Compounds with Rocksalt Lattice

The green fluorescence of the following phosphors is reported: , , , , and . Their crystal structures are based on the rocksalt lattice. It is found that for increasing lithium content of the host lattice the position of the maximum of the emission band shifts to shorter wavelengths and the quantum efficiency increases. This relation is discussed. Concentration quenching occurs at low activator concentration. with regular octahedra emits also in the green. For some other compounds red emission was found. Green uranium emission is assigned to groups and uranyl groups, red emission to groups. It is shown that this assignment is consistent with the structural data for a large number of uranium‐activated oxides. Energy transfer was observed between the uranium center and Eu3+. Addition of Cr3+ or Rh3+ quenches the uranium fluorescence drastically.