Hydroxyl Stretching Bands in Micas: A Quantitative Interpretation

Clay Minerals ◽  
1970 ◽  
Vol 8 (4) ◽  
pp. 375-388 ◽  
Author(s):  
Paul G. Rouxhet
Keyword(s):  
Chemical Composition ◽  
Absorption Coefficient ◽  
Frequency Band ◽  
Low Frequency ◽  
Orientation Distribution ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Quantitative Interpretation ◽  
Oh Content

AbstractMethods are described for estimating a valuable absorption coefficient for OH stretching bands of micas: the integrated parallel absorption coefficient K.From a correlation between this coefficient and the OH content of biotites and phlogopites, it was found that the parallel absorption coefficient per hydroxyl group in these trioctahedral micas is not appreciably influenced by the chemical composition and the direction of the OH bond. A clear deviation was observed for the low frequency band of a biotite characterized by a well-ordered orientation distribution for the corresponding hydroxyl groups.The integrated parallel absorption coefficient of muscovite is proportionally 2·5 to 3 times larger than that of trioctahedral micas.

The structure of an intercalated ordered kaolinite — a Raman microscopy study

Clay Minerals ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 587-596 ◽  
Author(s):  
R. L. Frost ◽  
T. H. Tran ◽  
J. Kristof
Keyword(s):  
Raman Band ◽  
Low Frequency ◽  
Potassium Acetate ◽  
Microscopy Study ◽  
Raman Microscopy ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Surface Hydroxyl ◽  
Inner Surface ◽  
Order Of Magnitude

AbstractChanges in the molecular structure of a highly ordered kaolinite, intercalated with urea and potassium acetate, have been studied using Raman microscopy. A new Raman band, attributed to the inner surface hydroxyl groups strongly hydrogen bound to the acetate, is observed at 3605 cm-1 for the potassium acetate intercalate with the consequential loss of intensity in the bands at 3652, 3670, 3684 and 3693 cm-1. Remarkable changes in intensity of the Raman spectral bands of the low-frequency region of the kaolinite occurred upon intercalation. In particular, the 144 and 935 cm-1 bands increased by an order of magnitude and were found to be polarized. These spectroscopic changes provide evidence for the inner surface hydroxyl group-acetate bond being at an angle approaching 90° to the 001 face. Decreases in intensity of the bands at 243, 271 and 336 cm-1 were observed. The urea intercalate shows additional Raman bands at 3387, 3408 and 3500 cm-1 which are attributed to N-H vibrations after formation of the urea-kaolinite complex. Changes in the spectra of the inserting molecules were also observed.

scholarly journals Research on sound absorption characteristics of Alberich anechoic coatings in debonding states

2019 ◽  
Vol 283 ◽  
pp. 09008
Author(s):  
Xianwen Zhao ◽  
Dejiang Shang ◽  
Chao Zhang ◽  
Lu Yin
Keyword(s):  
Absorption Coefficient ◽  
Frequency Band ◽  
Incident Wave ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Absorption Coefficient ◽  
Absorbing Boundary ◽  
Reflected Wave ◽  
Important Position ◽  
Absorption Characteristics

Viscoelastic structures with periodic cavity arrangement occupy an important position in acoustic stealth. Most studies focus on the absorption at low frequency, under large pressure and in a wide frequency band, however, the sound absorption properties of the anechoic coating in debonding states are seldom studied. The acoustic response of the composite structure is calculated by the FEM, and the incident wave and the reflected wave are separated based on the plane wave propagation principle. The sound absorption coefficient of the model can be solved with the pressure data of transmission wave, incident wave and reflected wave. Based on the finite element method, the absorption characteristics of anechoic coating in debonding states have been studied. Firstly, the FEM model is verified by comparing the solution of uniform non-cavity coatings with the corresponding analytical solution. The results indicate that the problem of acoustic pressure field can be simulated well by the symmetry condition and the absorbing boundary. Then, the Alberich anechoic coating models in different debonding ratio states and in different cavity water filling states are established by FEM, and then the corresponding absorption characteristics are calculated and analyzed. The results show that the effects of debonding on absorption characteristics are small when the cavities of coatings are filled with water, however the effects are much more when the cavities of coatings are filled with air. For the case of cavities filled with air, the main frequency band of sound absorption moves to low frequency with the debonding ratio increasing. When the frequency is very high, there are few impacts on the sound absorption coefficient no matter whether the packing medium is water or air, no matter whether the coating is debonding or not.

Experimental Research on the Normal Absorption Coefficient of the Multilayer Material

2011 ◽  
Vol 213 ◽  
pp. 608-612
Author(s):  
Tao Feng ◽  
Bin Liu ◽  
Jing Wang ◽  
Xue Wu ◽  
Nan Li
Keyword(s):  
Absorption Coefficient ◽  
Frequency Band ◽  
High Frequency ◽  
Low Frequency ◽  
Experimental System ◽  
Aluminum Plate ◽  
Multilayer Material ◽  
Area Density ◽  
Normal Absorption ◽  
Peak Value

The normal absorption coefficient of the multilayer material was studied in this research. A measurement duct system was established at first, and then the absorption coefficients of multilayer material with different structures were measured through this experimental system. Some conclusions could be drawn: Compared with the uniform material, the multiple layer material can change the absorption coefficient significantly without increasing the thickness of the material in low frequency band. The position and the area density of the aluminum plate can both change the absorption coefficient significantly. The frequency corresponding to the absorbing peak value decreases with the increasing of the area density of aluminum plate. The absorption coefficient becomes larger near to one in low frequency band and in the meantime changes lower than 0.1 in the high frequency band. The position and area density of the aluminum plate can be designed to satisfy the requirements of the sound absorption.

Contact Current Density Analysis Inside Human Body in Low-Frequency Band Using Geometric Multi-Grid Solver

2020 ◽  
Vol E103.C (11) ◽  
pp. 588-596
Author(s):  
Masamune NOMURA ◽  
Yuki NAKAMURA ◽  
Hiroo TARAO ◽  
Amane TAKEI
Keyword(s):  
Frequency Band ◽  
Current Density ◽  
Human Body ◽  
Low Frequency ◽  
Density Analysis

scholarly journals Reactivity of Aliphatic and Phenolic Hydroxyl Groups in Kraft Lignin towards 4,4′ MDI

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2131
Author(s):  
Leonardo Dalseno Antonino ◽  
Júlia Rocha Gouveia ◽  
Rogério Ramos de Sousa Júnior ◽  
Guilherme Elias Saltarelli Garcia ◽  
Luara Carneiro Gobbo ◽  
...  
Keyword(s):  
Experimental Work ◽  
Chemical Structure ◽  
31P Nmr ◽  
Kraft Lignin ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Diphenylmethane Diisocyanate ◽  
Complex Chemical ◽  
Heterogeneous Reactivity ◽  
Phenolic Hydroxyl Groups

Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.

Low-frequency sound absorption of a tunable multilayer composite structure

2021 ◽  
pp. 107754632110082
Author(s):  
Hanbo Shao ◽  
Jincheng He ◽  
Jiang Zhu ◽  
Guoping Chen ◽  
Huan He
Keyword(s):  
Porous Material ◽  
Absorption Coefficient ◽  
Composite Structure ◽  
Low Frequency ◽  
Acoustic Absorption ◽  
Multilayer Composite ◽  
Absorption Frequency ◽  
Acoustic Absorption Coefficient ◽  
Simulation And Experiment ◽  
Single Material

Our work investigates a tunable multilayer composite structure for applications in the area of low-frequency absorption. This acoustic device is comprised of three layers, Helmholtz cavity layer, microperforated panel layer, and the porous material layer. For the simulation and experiment in our research, the absorber can fulfill a twofold requirement: the acoustic absorption coefficient can reach near 0.8 in very low frequency (400 Hz) and the range of frequency is very wide (400–3000 Hz). In all its absorption frequency, the average of the acoustic absorption coefficient is over 0.9. Besides, the absorption coefficient can be tunable by the scalable cavity. The multilayer composite structure in our article solved the disadvantages in single material. For example, small absorption coefficient in low frequency in traditional material such as microperforated panel and porous material and narrow reduction frequency range in acoustic metamaterial such as Helmholtz cavity. The design of the composite structure in our article can have more wide application than single material. It can also give us a novel idea to produce new acoustic devices.

scholarly journals Enhanced Magnetic Microwave Absorption at Low‐Frequency Band by Ferrite Assembled Microspheres with Controlled Components and Morphologies

2021 ◽  
Author(s):  
Mengqiu Huang ◽  
Xuefeng Yu ◽  
Lei Wang ◽  
Jiwei Liu ◽  
Wenbin You ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Frequency Band ◽  
Low Frequency

scholarly journals Enhancement of Antioxidant and Hydrophobic Properties of Alginate via Aromatic Derivatization: Preparation, Characterization, and Evaluation

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2575
Author(s):  
Smaher M. Elbayomi ◽  
Haili Wang ◽  
Tamer M. Tamer ◽  
Yezi You
Keyword(s):  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Benzoyl Group ◽  
Antioxidant Evaluation ◽  
Thermo Stability

The preparation of bioactive polymeric molecules requires the attention of scientists as it has a potential function in biomedical applications. In the current study, functional substitution of alginate with a benzoyl group was prepared via coupling its hydroxyl group with benzoyl chloride. Fourier transform infrared spectroscopy indicated the characteristic peaks of aromatic C=C in alginate derivative at 1431 cm−1. HNMR analysis demonstrated the aromatic protons at 7.5 ppm assigned to benzoyl groups attached to alginate hydroxyl groups. Wetting analysis showed a decrease in hydrophilicity in the new alginate derivative. Differential scanning calorimetry and thermal gravimetric analysis showed that the designed aromatic alginate derivative demonstrated higher thermo-stability than alginates. The aromatic alginate derivative displayed high anti-inflammatory properties compared to alginate. Finally, the in vitro antioxidant evaluation of the aromatic alginate derivative showed a significant increase in free radical scavenging activity compared to neat alginate against DPPH (2,2-diphenyll-picrylhydrazyl) and ABTS free radicals. The obtained results proposed that the new alginate derivative could be employed for gene and drug delivery applications.

scholarly journals Spillovers of Stock Markets among the BRICS: New Evidence in Time and Frequency Domains before the Outbreak of COVID-19 Pandemic

2021 ◽  
Vol 14 (3) ◽  
pp. 112
Author(s):  
Kai Shi
Keyword(s):  
Stock Market ◽  
Frequency Band ◽  
Stock Markets ◽  
Emerging Market ◽  
Low Frequency ◽  
Systematic Risk ◽  
Error Variance ◽  
Frequency Bands ◽  
Volatility Spillovers ◽  
Risk Sources

We attempted to comprehensively decode the connectedness among the abbreviation of five emerging market countries (BRICS) stock markets between 1 August 2002 and 31 December 2019 not only in time domain but also in frequency domain. A continuously varying spillover index based on forecasting error variance decomposition within a generalized abbreviation of vector-autoregression (VAR) framework was computed. With the help of spectral representation, heterogeneous frequency responses to shocks were separated into frequency-specific spillovers in five different frequency bands to reveal differentiated linkages among BRICS markets. Rolling sample analyses were introduced to allow for multiple changes during the sample period. It is found that return spillovers dominated by the high frequency band (within 1 week) part declined with the drop of frequencies, while volatility spillovers dominated by the low frequency band (above 1 quarter) part grew with the decline in frequencies; the dynamics of spillovers were influenced by crucial systematic risk events, and some similarities implied in the spillover dynamics in different frequency bands were found. From the perspective of identifying systematic risk sources, China’s stock market and Russia’s stock market, respectively, played an influential role for return spillover and volatility spillover across BRICS markets.

Bisquaternary ammonium salts derived from 3α,12α-Diamino-5β-cholane and 3α,12α-Diamino-24-nor-5β-cholane

1971 ◽  
Vol 24 (3) ◽  
pp. 521 ◽  
Author(s):  
S Ahmed ◽  
M Alauddin ◽  
B Caddy ◽  
M Martin-Smith ◽  
WTL Sidwell ◽  
...  
Keyword(s):  
Deoxycholic Acid ◽  
Ammonium Salts ◽  
Hydroxyl Group ◽  
Amino Compound ◽  
Hydroxyl Groups ◽  
Lithium Aluminium Hydride ◽  
Lithium Aluminium ◽  
Polyhydric Alcohols ◽  
Methane Sulphonate ◽  
Methylene Group

The preparation of 3α,12α-bisdimethylamino-5β-cholane dimethiodide, 3α,12α-bisdimethylamino-5β-cholane dimethiodide, 3α,12α- bisdimethylamino-24-nor-5β-cholanedimethiodide, and 3α,12α- bisdimethylamino-24-nor-5β-cholanediethiodide, from deoxycholic acid are described. During this work it was found that attempted copper- quinoline decarboxylation of dehydrocholic acid gives rise to lactol formation, and that what had previously been considered to be 3α,12α- dihydroxy-5β-cholane is a mixture of this compound and 12α,24- dihydroxy-5β-cholane. Comparable selectivity of attack by methanesulphonyl chloride and toluene-p-sulphonyl chloride occurs with various polyhydric alcohols derived from bile acids, as evidenced from the products of reduction of the sulphonates with lithium aluminium hydride. With both 5α- and 5β-cholane derivatives, a C 3 equatorial hydroxyl group exhibits comparable reactivity to the terminal primary hydroxyl group, generated from the bile acid carboxylic group, towards both sulphonyl chlorides. With axial hydroxyl groups at C 7 and C 12, toluene-p-sulphonate formation is much more difficult than methane- sulphonate formation. Reduction by means of lithium aluminium hydride of equatorial sulphonate esters at C 7 and C 12 gives rise to a methylene group, but the axial sulphonates under the same conditions give the axial alcohol. The same clear distinction between equatorial and axial sulphonate esters is not observed at C 3 and C 6, but 17α- methanesulphonyloxy-5α-androstane gives 5α-androstane and the 17β- ester gives 17β-hydroxy-5α-androstane. Reduction of 12-oximino groups in both 5α- and 5β-cholanes with sodium and ethanol, hydrogen in the presence of a catalyst, or lithium aluminium hydride gives solely the 12α-amino compound.

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