ESR and IR Evidence for Chromium in Kaolinites

Clay Minerals ◽  
1993 ◽  
Vol 28 (3) ◽  
pp. 353-364 ◽  
Author(s):  
C. Mosser ◽  
S. Petit ◽  
M. Mestdagh
Keyword(s):  
Spectral Feature ◽  
Structural Disorder ◽  
Esr Spectra ◽  
Octahedral Position ◽  
Broad Resonance ◽  
Edx Analysis ◽  
Ir Studies ◽  
Ft Ir ◽  
Hydrothermal Environment ◽  
Xrd Patterns

AbstractEvidence obtained from ESR and IR studies is presented for the presence of structural Cr in two natural kaolinites (MILO and GEY) formed in an hydrothermal environment in Sonoma County, California. The XRD patterns show a greater structural disorder for GEY than for MILO, but both have the usual hexagonal shapes as shown by TEM observations. On the basis of EDX analysis of different particles, GEY, on average, appears to be richer in Cr (2.1% Cr203) than MILO (0.6% Cr203). The presence of Fe oxide particles containing some Cr, Ni and V is also indicated by EDX analysis. By FT-IR observation, the octahedral Cr 3+ position was easily detected by a well resolved spectral feature at 3586 cm -1. The adsorbed Cr 3+ kaolinite (KMRXCR) presents no band at 3586 cm -1, but two other bands situated at 3527 and 3477 cm -1. The main features of the ESR spectra of these two kaolinites are a set of resonances near geff4; a broad resonance centred near geff2 with some modulations; and a set of resonances near gcffl. The broad resonance centred near geff2 is interpreted as the free iron oxide signal with modulations due to VO 2+. The set of resonances near geff4 is similar to that observed for octahedral Fe 3+, but the position is shifted compared to that of octahedral Fe 3+. This set of resonances near geff4 is, therefore, interpreted as belonging to Cr 3+ in octahedral position. The resonances at geff1 are also interpreted as belonging to Cr 3-. Comparison with the Cr 3+ surface-adsorbed ESR signal of a Cr-saturated kaolinite (which is a broad resonance centred near geff2) strengthens the interpretation of the geff4 resonances belonging to Cr 3+ in the octahedral position. The results obtained by the combination of FT-IR and ESR spectroscopics indicate that Cr 3+ is present in the octahedral position of the MILO and GEY kaolinites.

scholarly journals A Facile One-Pot Approach to the Synthesis of Gd-Eu Based Metal-Organic Frameworks and Applications to Sensing of Fe3+ and Cr2O72− Ions

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1679
Author(s):  
Roberta Puglisi ◽  
Anna L. Pellegrino ◽  
Roberto Fiorenza ◽  
Salvatore Scirè ◽  
Graziella Malandrino
Keyword(s):  
Surface Area ◽  
Metal Organic Frameworks ◽  
3D Structure ◽  
Inorganic Ions ◽  
Total Surface Area ◽  
One Pot ◽  
Green Approach ◽  
Metal Organic ◽  
Ft Ir ◽  
Xrd Patterns

Gadolinium metal-organic frameworks (Gd-MOFs) and Eu-doped Gd-MOFs have been synthesized through a one-pot green approach using commercially available reagents. The 1,4-benzenedicarboxylic acid (H2-BDC) and 2,6-naphthalenedicarboxylic acid (H2-NDC) were chosen as ditopic organic linkers to build the 3D structure of the network. The Gd-MOFs were characterized using powder X-ray diffraction (XRD), FT-IR spectroscopy, field emission scanning electron microscopy (FE-SEM) and N2 adsorption–desorption analysis. The Gd-MOF structures were attributed comparing the XRD patterns, supported by the FT-IR spectra, with data reported in the literature for Ln-MOFs of similar lanthanide ionic radius. FE-SEM characterization points to the effect of the duration of the synthesis to a more crystalline and organized structure, with grain dimensions increasing upon increasing reaction time. The total surface area of the MOFs has been determined from the application of the Brunauer–Emmett–Teller method. The study allowed us to correlate the processing conditions and ditopic linker dimension to the network surface area. Both Gd-MOF and Eu-doped Gd-MOF have been tested for sensing of the inorganic ions such as Fe3+ and Cr2O72−.

A Simple Dissolved Metals Mixing Route to Prepare Nanostructured Mg0.8Zn0.2TiO3 Solid Solution

2015 ◽  
Vol 1112 ◽  
pp. 47-52 ◽  
Author(s):  
Frida Ulfah Ermawati ◽  
Suasmoro Suasmoro ◽  
Suminar Pratapa
Keyword(s):  
Solid Solution ◽  
Particle Size ◽  
Rietveld Analysis ◽  
Dissolved Metals ◽  
Intermediate Phases ◽  
Particle Size Analyzer ◽  
Ft Ir ◽  
Xrd Patterns ◽  
Zn Ions

A study of liquid mixing route to synthesize high purity Mg0.8Zn0.2TiO3 nanopowder, a candidate dielectric ceramics, has been successfully performed. Formation of the phases on the dried powder was studied using TG/DTA, XRD and FT-IR data. Rietveld analysis on the collected XRD patterns confirmed the formation of solid solution in the system. Such solid solution can be obtained from the powder calcined at 500 °C, but calcination at 550 °C gave rise to the most optimum molar purity up to 98.5% without intermediate phases. The role of Zn ions on the formation of solid solution was also discussed. Homogeneity of particle size distribution and nano-crystallinity of the system was verified from the particle size analyzer data, TEM image and the Rietveld analysis output.

Improvement of Apatite-Forming Ability of Tantalum Metal by CaCl2 Treatment

2007 ◽  
Vol 361-363 ◽  
pp. 681-684
Author(s):  
Deepak K. Pattanayak ◽  
Tomiharu Matsushita ◽  
Hiroaki Takadama ◽  
Tadashi Kokubo ◽  
Takashi Nakamura
Keyword(s):  
Heat Treatment ◽  
Simulated Body Fluid ◽  
Body Fluid ◽  
Edx Analysis ◽  
Na Ions ◽  
Naoh Treatment ◽  
Tantalum Metal ◽  
Cacl2 Treatment ◽  
Xrd Patterns

Tantalum metal was soaked in NaOH and CaCl2 solutions, and then subjected to heat treatment at 500°C. EDX analysis showed that about 6.5 at. % of Na was incorporated into the surface of the tantalum metal by the first NaOH treatment. These Na+ ions were replaced by Ca2+ ions by the subsequent CaCl2 treatment. According to TF-XRD patterns, an amorphous sodium tantalate was seemed to be formed on the tantalum metal by the NaOH treatment and transformed into amorphous calcium tantalate by the CaCl2 treatment. This phase was crystallized into Ca2Ta2O7 by heat treatment. Critical detaching load of the surface of the CaCl2-treated tantalum metal was as low as 5mN, while as high as 42mN after the heat treatment. Apatite-forming ability of the NaOH-treated tantalum metal in a simulated body fluid (SBF) was appreciably increased by the CaCl2 treatment and maintained even after the heat treatment.

Effects of ultra-high pressures (>3.6 GPa) on the electrical resistance of polyaniline by in situ FT-IR studies

1997 ◽  
Vol 280 (5-6) ◽  
pp. 469-474 ◽  
Author(s):  
Xing-Rong Zeng ◽  
Ke-Cheng Gong ◽  
Ke-Nan Weng ◽  
Wan-Sheng Xiao ◽  
Wen-Hong Gan ◽  
...  
Keyword(s):  
Electrical Resistance ◽  
High Pressures ◽  
Ir Studies ◽  
Ft Ir

FT-IR studies on the acidity of gallium-substituted mesoporous MCM-41 silica

2004 ◽  
Vol 85 (1) ◽  
pp. 145-150 ◽  
Author(s):  
Gemma Turnes Palomino ◽  
Juan José Cuart Pascual ◽  
Montserrat Rodrı́guez Delgado ◽  
José Bernardo Parra ◽  
Carlos Otero Areán
Keyword(s):  
Ir Studies ◽  
Ft Ir ◽  
Mcm 41

ICP-AES and FT-IR Studies on the Effect of Cadmium on the Groundnut Cultivar

2008 ◽  
Author(s):  
K. Karpagavalli ◽  
V. K. Vaidyan ◽  
V. S. Jayakumar
Keyword(s):  
Ir Studies ◽  
Ft Ir

scholarly journals Physical, Optical and FT-IR studies of Bismuth-Boro-tellurite Glasses containing BaO as modifier

2018 ◽  
Vol 360 ◽  
pp. 012022 ◽  
Author(s):  
B Srinivas ◽  
Abdul Hameed ◽  
M N Chary ◽  
Md Shareefuddin
Keyword(s):  
Tellurite Glasses ◽  
Ir Studies ◽  
Ft Ir

Effects of Indium Incorporation on the Optical Properties of ZnO Films

2006 ◽  
Vol 11-12 ◽  
pp. 159-162 ◽  
Author(s):  
Yong Ge Cao ◽  
Lei Miao ◽  
Sakae Tanemura ◽  
Yasuhiko Hayashi ◽  
Masaki Tanemura
Keyword(s):  
Optical Transmission ◽  
Full Width Half Maximum ◽  
Structural Disorder ◽  
Band Gaps ◽  
Zno Films ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optical Band Gaps ◽  
Xrd Patterns

Transparent indium-doped ZnO (IZO) films with low In content (<6at%) were fabricated through radio-frequency (rf) helicon magnetron sputtering. Formation of In-Zn-O solid solution was confirmed by X-ray diffraction (XRD) patterns. Incorporation of indium into ZnO films enhances the optical transmission in the visible wavelength. The optical band-gaps slightly increase from 3.25eV (ZnO) to 3.28eV (In0.04Zn0.96O) and to 3.30eV (In0.06Zn0.94O) due to Burstain-Moss effect. The Urbach tail parameter E0, which is believed to be a function of structural disorder, increases from 79meV (ZnO), to 146meV (In0.04Zn0.96O), and to 173meV (In0.06Zn0.94O), which is consistent with increase of Full-Width Half-Maximum (FWHM) in corresponding XRD patterns. Decreasing in crystal quality with increasing indium concentration is also confirmed by photoluminescence spectra.

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