Chromium Ions (chromium + ion)

Distribution by Scientific Domains
Polymers and Materials Science66%

Selected Abstracts

Lanthanum Chromite-Based Interconnects as Key Materials for SOFC Stack Development

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2004
Natsuko Sakai
The historical investigations on the physicochemical and transport properties of lanthanum chromite-based perovskite oxides are reviewed to evaluate the compatibility as interconnects in solid oxide fuel cells. These materials improve sinterability in air. This has led to investigations on other physicochemical properties of these materials, such as thermal expansion, mechanical strength, and chemical stability. Lanthanum and chromium ion can be substituted by alkaline earths or transition metals, and this translates into a large flexibility in physicochemical properties. However, the formation of oxygen vacancies in a reducing atmosphere can result in an undesirable isothermal expansion or oxygen permeation. The chemical stability of these materials is governed by the fast cation diffusion at the grain boundary of the polycrystals. [source]

Hierarchical Nanomaterials: Smart Microcapsules Encapsulating Reconfigurable Carbon Nanotube Cores (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Mater.
Heavy metal ion removal is demonstrated using carbon nanotubes (CNTs) surrounded by iron oxide microcapsules by W. S. Choi on page 820. The CNTs conglomerate and form a core inside the capsule upon exposure to high temperature, while they scatter when they are subjected to mild sonication. These hierarchical structures can capture lead and chromium ions, which can later be desorbed by exposure to low pH conditions. [source]

Smart Microcapsules Encapsulating Reconfigurable Carbon Nanotube Cores

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Won San Choi
Abstract The encapsulation of carbon nanotubes (CNTs) to form a reconfigurable conglomerate within iron oxide microcapsules is demonstrated. The individual CNTs conglomerate and form a core inside the capsule upon exposure to high temperature, while they scatter when subjected to mild sonication at low pH. The assembly/disassembly of CNTs within the capsule was reversible and could be repeated by alternate heating and sonication. Also, the fabrication protocol could be used for the generation of various multifunctional hollow structures. To test the feasibility of using the capsules in real applications, the capacity of the capsules as a heavy metal ion remover was explored. The resulting capsules showed an excellent ability to remove lead and chromium ions. In addition, desorption of the metal ions adsorbed on the CNTs could be induced by exposure to low pH. Thus, encapsulated CNTs might be a recyclable, environmentally friendly agent for the removal of heavy metal ions. [source]

Genetic correlation between chromium resistance and reduction in Bacillus brevis isolated from tannery effluent

JOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2009
T. Verma
Abstract Aims:, To investigate the genetic basis of Cr(VI) resistance and its reduction to Cr(III) in indigenous bacteria isolated from tannery effluent. Methods and Results:, Four bacteria resistant to high Cr(VI) levels were isolated and identified as Bacillus spp. Their Cr(VI) reduction ability was tested. To assess the genetic basis of Cr(VI) resistance and reduction, plasmid transfer and curing studies were performed. Among all, B. brevis was resistant to 180 ,g Cr(VI) ml,1 and showed the greatest degree of Cr(VI) reduction (75·8%) within 28 h and its transformant was resistant to 160 ,g Cr(VI) ml,1 and reduced 69·9% chromate. It harboured a stable 18 kb plasmid DNA. Transfer and curing studies revealed that both the chromate resistance and reduction were plasmid mediated. The presence of other metal cations did not have any significant effect on Cr(VI) bioreduction. Conclusions:,Bacillus brevis was resistant to elevated Cr(VI) levels and may potentially reduce it in short time from an environment where other metal ions are also present in addition to chromium ions. The strain tested shows a positive correlation between genetic basis of Cr(VI) resistance and reduction. Significance and Impact of the Study:, To our knowledge, this is the first study on the genetic correlation between chromium resistance and reduction in bacteria. Such strains may potentially be useful in biotechnological applications and in situ Cr(VI) bioremediation. [source]

Production of microporous resins for heavy-metal removal.

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008

Abstract Ion-exchange polymers were used successfully in water-treatment operations. In this study, three ion-exchange resins based on 4-vinylpyridine and divinylbenzene functionalized with N -oxide groups were obtained. Their ion-adsorption properties were measured in solutions containing chromium at concentrations of 4 and 500 ppm with column and batch equilibrium techniques. The removal efficiency of the chromium ions with HCl was observed to increase after the protonation of the N -oxide groups. The resins could be reused after 10 cycles with the metal removal efficiency maintained at higher than 95%. These studies evidenced a strong correlation between the morphology and ionic group content in the resin and its chromium ion sorption capability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source]

Origin of red luminescence of sodium titanium phosphate crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005
R.S. Boyko
Abstract Sodium titanium orthophosphate NaTi2(PO4)3 crystals were synthesized and their luminescence properties were investigated. Luminescence spectra of this compound consist of two main bands in the green and red spectral regions. Maximum positions of the bands depend on temperature of the samples. At some conditions the red band reveals details of a fine spectra structure. Obtained results are discussed taking into account similarity of spectral properties of the investigated crystals with ones described recently for sodium aluminum diphosphate crystals doped with chromium ions. Conclusion is made that red emission band is corresponded to radiation transitions in the Ti3+ titanium ions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]