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1.
A series of calcium silicate hydrate (C–S–H)-polymer nanocomposite
(C–S–HPN) materials were prepared by incorporating poly(acrylic
acid) (PAA) into the inorganic layers of C–S–H during precipitation
of quasicrystalline C–S–H from aqueous solution. The as-synthesized
C–S–HPN materials were characterized by X-ray fluorescence (XRF),
X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy
(SEM-EDS), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric
analysis (TG) and differential scanning calorimetry (DSC). The XRD analysis
of C–S–HPN materials suggest the intermediate organizations presenting
intercalation of PAA within C–S–H and exfoliation of C–S–H.
The SEM micrographs of C–S–H, PAA and C–S–HPN materials
with different PAA contents exhibit the significant differences in their morphologies.
The effect of the material’s composition on the thermal stability of
a series of C–S–HPN materials along with PAA and C–S–H
were studied by TG, DTA and DSC. Three significant decomposition temperature
ranges were observed on the TG curves of all C–S–HPN materials. 相似文献
2.
Jakubowska N Polkowska Z Kujawski W Konieczka P Namieśnik J 《Analytical and bioanalytical chemistry》2007,388(3):691-698
The analysis of volatile organic compounds in samples of biological fluids characterized by complex matrices is highly challenging.
This paper presents a comparison of the results obtained in this field using three solvent-free techniques: thin-layer headspace
with autogenous generation of liquid sorbent (TLHS) and membrane separation of the trace substances (pervaporation, PV), both
of which are coupled to direct aqueous injection gas chromatography–electron capture detection (TLHS–DAI–GC–ECD and PV–DAI–GC–ECD),
as well as conventional static headspace analysis followed by GC analysis with ECD detection (HS–GC–ECD). Basic validation
parameters of the HS–GC–ECD, TLHS–DAI–GC–ECD and PV–DAI–GC–ECD procedures were calculated for water and urine samples. The
calibration curves for all procedures were linear within the concentration range examined. The intermediate precisions of
the procedures were good and reached about 10% (for all analytes) for HS–GC–ECD and TLHS–DAI–GC–ECD. The poorest results were
obtained for PV–DAI–GC–ECD: about 20% for all analytes. The lowest method detection limits were obtained for the TLHS–DAI–GC–ECD
procedure: below 0.0022 μg/L for all analytes. The enrichment factors did not differ significantly between water and urine
samples, indicating little or no matrix effect in all procedures. 相似文献
3.
Dianxue Cao Xue Cao Guiling Wang Lin Wu Zhanshuang Li 《Journal of Solid State Electrochemistry》2010,14(5):851-855
Mg–Li–Al–Sn and Mg–Li–Al–Sn–Ce alloys were prepared using a vacuum induction melting method. Their electrochemical oxidation
behavior in NaCl solution was investigated by means of potentiodynamic and chronoamperometric measurements. The surface morphology
after discharge was examined using scanning electron microscopy. Utilization efficiency was estimated with a mass-loss method.
The results indicated that Mg–Li–Al–Sn has a higher discharge current density but lower utilization efficiency than Mg–Li–Al–Sn–Ce.
The typical utilization efficiency after continuous discharging at constant potential of −1.0 for 2 h is 65% and 70% for Mg–Li–Al–Sn
and Mg–Li–Al–Sn–Ce, respectively. The utilization efficiency decreased with the increase of anodic potential. Both alloys
have similar self-discharge rate in NaCl solution at open-circuit potential. 相似文献
4.
Several calcium silicate hydrate (C–S–H)-polymer nanocomposite
(C–S–HPN) materials have been prepared by incorporating poly(acrylic
acid) (PAA) into the inorganic layers of C–S–H during precipitation
of quasicrystalline C-S-H from aqueous solution. The synthetic C–S–HPN
materials were characterized by X-ray fluorescence (XRF), X-ray diffraction
(XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy/energy
dispersive spectroscopy (SEM-EDS), thermogravimetry (TG), differential thermogravimetry
(DTG) and differential scanning calorimetry (DSC). The XRD peaks of C–S–HPN
materials suggest the intermediate organizations presenting both intercalation
of PAA and exfoliation of C–S–H. The SEM images of C–S–H
and C–S–HPN materials with different PAA contents exhibit the
significant differences in their morphologies. Effects of the material compositions
on the thermal stability of series of C–S–HPN materials along
with PAA and C–S–H has been studied by TG, DTG and DSC. Three
significant decomposition temperature ranges were observed on the TG curves
of all C–S–HPN materials. 相似文献
5.
S. C. Mojumdar L. Raki N. Mathis K. Schimdt S. Lang 《Journal of Thermal Analysis and Calorimetry》2006,85(1):119-124
A non-ionic polymer (poly(vinyl
alcohol) (PVA)) has been incorporated into the inorganic layers of calcium
silicate hydrate (C–S–H) during precipitation of quasicrystalline
C–S–H from aqueous solution. C–S–H and a C–S–H-polymer
nanocomposite (C–S–HPN) material were synthesized and characterized
by X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), 29Si
magic angle spinning nuclear magnetic resonance (29Si
MAS NMR) and 13C cross-polarization nuclear magnetic
resonance (13C CP NMR) spectroscopy, atomic force
microscopy (AFM), thermal conductivity, thermogravimetric analysis (TG) and
differential thermal analysis (DTA). Thermal conductivity of PVA, C–S–H
and C–S–HPN material was studied in the temperature range 25–50°C.
C–S–HPN materials exhibited the highest thermal conductivity at
25 and 50°C. The thermal conductivity increases from 25 to 50°C are
7.03, 17.46 and 14.85% for PVA, C–S–H and C–S–HPN
material, respectively. Three significant decomposition temperature ranges
were observed on the TG curve of C–S–HPN material. 相似文献
6.
Geoff Rayner-Canham 《Foundations of Chemistry》2011,13(3):223-232
As part of a series of contributions on patterns in the periodic table, the relationships among the transition metals are
examined here in a systematic manner. It is concluded that the traditional method of categorizing transition elements by group
or by period is not as valid as by using combinations thereof. From chemical similarities, it is proposed that the transition
metals be considered as the [V–Cr–Mn] triad; the [Fe–Co–Ni–Cu] tetrad; the [Ti–Zr–Hf–Nb–Ta] pentad; the [Mo–W–Tc–Re] tetrad;
and the [Ru–Os–Rh–Ir–Pd–Pt–Au] heptad. Silver does not fit neatly in anywhere and is better linked with thallium. 相似文献
7.
The poly(glycidyl methacrylate) adsorbents P(GMA–EDMA) and P(GMA–DVB) were synthesized by the radical suspension–polymerization
method and farther coupled by oligo-β-cyclodextrin (CDP) to obtain P(GMA–EDMA)–CDP and P(GMA–DVB)–CDP. The synthesized polymeric
media were characterized by Fourier transform infrared (FTIR) spectrometer, scanning electron microscopy, and BET surface
area. The adsorption of puerarin from aqueous solution onto the four media, i.e., P(GMA–EDMA), P(GMA–DVB), P(GMA–EDMA)–CDP,
and P(GMA–DVB)–CDP, was studied. An enhanced adsorption of puerarin apparently presented on grafted media. The interaction
between the polymeric media and the puerarin was researched by FTIR. The result shows that the adsorption efficiency on P(GMA–DVB)–CDP
driven by multiple weak interactions is much higher than that on P(GMA–EDMA) driven by hydrogen bonding interaction only and
on P(GMA–DVB) or P(GMA–EDMA)–CDP driven by two interactions. 相似文献
8.
Zou Hantao Yi Changhai Wang Luoxin Liu Hongtao Xu Weilin 《Journal of Thermal Analysis and Calorimetry》2009,97(3):929-935
Thermogravimetric (TG), differential thermal analysis (DTA) and thermal degradation kinetics, FTIR and X-ray diffraction (XRD)
analysis of synthesized glycine–montmorillonite (Gly–MMT) and montmorillonite bound dipeptide (Gly–Gly–MMT) along with pure
Na–MMT samples have been performed. TG analysis at the temperature range 25–250 °C showed a mass loss for pure Na–MMT, Gly–MMT
and Gly–Gly–MMT of about 8.0%, 4.0% and 2.0%, respectively. DTA curves show the endothermic reaction at 136, 211 and 678 °C
in pure Na–MMT whereas Gly–MMT shows the exothermic reaction at 322 and 404 °C and that of Gly–Gly–MMT at 371 °C. The activation
energies of the first order thermal degradation reaction were found to be 1.64 and 9.78 kJ mol−1 for Gly–MMT and Gly–Gly–MMT, respectively. FTIR analyses indicate that the intercalated compounds decomposed at the temperature
more than 250 °C in Gly–MMT and at 250 °C in Gly–Gly–MMT. 相似文献
9.
Jerzy Jurczyk Rafał Sitko Beata Zawisza Franciszek Buhl Ewa Malicka 《Mikrochimica acta》1999,132(1):41-47
A simple and quick method of durable samples preparation by the thin layer method through direct digesting of the analysed
material on the substrate has been presented. Four- and three-component mono- and polycrystals have been analysed. Standards
have been used in calibration containing: Cr, Co, Ni, Cu, Zn, Ga, Se, Sb, Yb. To improve the correlation between the concentration
and the fluorescent radiation models of mathematical corrections have additionally been used: multiple linear regression,
Lucas-Tooth-Pyne model (L. T. P.) and de Jongh model (d. J.).
Statistical parameters: detection limits for 0.5 mg samples: Cr–0.041%, Co–0.034%, Ni–0.042%, Cu–0.053%, Zn–0.054%, Ga–0.057%,
Se–0.057%, Sb–0.113%, Yb–0.077%. Correlation coefficients: simple regression 0.9946–0.9997, multiple regression 0.9974–1.0000,
L. T. P. 0.9993–1.0000, d. J. 0.9995–1.0000.
Received August, 1, 1998. Revision March 25, 1999. 相似文献
10.
Complexes of cell–THPC–urea–ADP with transition metal ion Co2+ and lanthanide metal ions such as La3+, Ce4+, Nd3+ and Sm3+ have been prepared. The thermal behavior and smoke suspension of the samples are determined by TG, DTA, DTG and cone calorimetry.
The activation energies for the second stage of thermal degradation have been obtained by following Broido equation. Experimental
data show that for the complexes of cell–THPC–urea–ADP with the metal ions, the activation energies and thermal decomposition
temperatures are higher than those of cell–THPC–urea–ADP, which shows these metal ions can increase the thermal stability
of cell–THPC–urea–ADP. Moreover, these lanthanide metal ions can more increase thermal stability of samples than do the transition
metal ion Co2+. The cone calorimetry data indicate that the lanthanide metal ions, similar to transition metal Co2+, greatly decrease the smoke, CO and CO2 generation of cell–THPC–urea–ADP, which can be used as smoke suppressants. 相似文献
11.
It was recently shown that complexes of the type F–Cl···CN–R, ostensibly halogen bonded, sometimes have properties (relatively
high binding energies, short Cl–C separations and considerably lengthened F–Cl distances) that are inconsistent with typical
halogen bonds (Del Bene et al. in J Phys Chem A 114:12958–12962, 2010). We attribute these anomalous features, as well as analogous observations for F–Cl···SiN–R systems, to the strong polarization
of the CN–R carbons and SiN–R silicons by the electric field of the positive σ-hole of the F–Cl chlorine. This polarization
may evolve into some degree of dative sharing of electrons by the carbons and silicons. This interpretation is supported by
the fact that complexes of CN–R and SiN–R with Cl–Cl, which has a much weaker positive σ-hole than F–Cl, are considerably
less likely to show the unusual features. It is demonstrated that the full ranges of binding energies of the CN–R and SiN–R
complexes with either F–Cl or Cl–Cl can be represented well (R
2 > 0.96) in terms of the most negative electrostatic potentials and the lowest local ionization energies on the carbon and
silicon surfaces. These properties reflect the electrostatic components of the interactions and the polarizabilities/dative
reactivities of the carbons and silicons. 相似文献
12.
A. Ebrahimi S. M. Habibi Khorassani H. Delarami H. Esmaeeli 《Journal of computer-aided molecular design》2010,24(5):409-416
The substituent effects on the geometrical parameters and the individual hydrogen bond (HB) energies of base pairs such as
X–adenine–thymine (X–A–T), X–thymine–adenine (X–T–A), X–guanine–cytosine (X–G–C), and X–cytosine–guanine (X–C–G) have been studied by the quantum mechanical calculations at the B3LYP and MP2 levels with the 6–311++G(d,p) basis set. The
electron withdrawing (EW) substituents (F and NO2) increase the total binding energy (ΔE) of X–G–C derivatives and the electron donating (ED) substituent (CH3) decreases it when they are introduced in the 8 and 9 positions of G. The effects of substituents are reversed when they are located in the 1, 5, and 6 positions of C, with exception of CH3 in the 1 position and F in the 5 position, which in both cases the ΔE value decreases negligibly small. With minor exceptions (X=8–CH3, 8–F, and 9–NO2), both ED and EW substituents increase slightly the ΔE values of X–A–T derivatives. The individual HB energies (∆E
HBs) have been estimated using electron densities that calculated at the hydrogen bond critical points (HBCPs) by the atoms
in molecules (AIM) method. Most of changes of individual HBs are in consistent with the ED/EW nature of substituents and the
role of atoms entered H-bonding. The remarkable change is observed for NO2 substituted derivative in each case. 相似文献
13.
Ines García-Lodeiro A. Fernández-Jiménez M. Teresa Blanco Angel Palomo 《Journal of Sol-Gel Science and Technology》2008,45(1):63-72
The study explored the compatibility between the main product of Portland cement hydration and the main product of the alkali
activation of fly ash: C–S–H and N–A–S–H gels, respectively. Both gels were synthesized with laboratory reagents at different
pH values. Blends of the two were synthesized as well, using the sol–gel procedure. All the gels were characterized with Fourier
transform IR spectroscopy (FTIR). The gels synthesized with this procedure were shown to precipitate together with a silica-rich
gel. In addition, the pH level was found to play a determinant role in both C–S–H and N–A–S–H gel synthesis. The C–S–H gel
is the major phase formed at pH > 11 and N–A–S–H gel for pH > 12. The results relating to the joint synthesis of the two (C–S–H
and N–A–S–H) gels were not conclusive. Technique used for the characterization failed to differentiate between them in the
blended material.
相似文献
Ines García-LodeiroEmail: |
14.
R. Schindler R. Vonach B. Lendl R. Kellner 《Fresenius' Journal of Analytical Chemistry》1998,362(1):130-136
A new process control methodology for the simultaneous determination of sugars, alcohols and organic acids in wine based
on multivariate evaluation of mid-IR transmission spectra of wine samples is presented. In addition to ethanol several lower
level wine components (glucose, fructose, glycerol, citric-, tartaric-, malic-, lactic- and acetic acid) were determined.
To establish a multivariate calibration model a set of 72 calibration solutions was prepared and measured, using a novel,
fully automated sequential injection (SI) system with Fourier transform infrared (FTIR) detection. The resulting spectra were
evaluated using a partial least square (PLS) model. The developed PLS model was then applied to the analysis of real wine
samples containing 79–91 g L–1 ethanol, 5.9–8.1 g L–1 glycerol, 0.4–6.9 g L–1 glucose, 1.5–7.5 g L–1 fructose, 0.3–1.6 g L–1 citric acid, 1.0–1.7 g L–1 tartaric acid, 0.02–3.2 g L–1 malic acid, 0.4–2.8 g L–1 lactic acid and 0.15–0.60 g L–1 acetic acid, yielding results which were in good agreement with those obtained by an external reference method (HPLC-IR).
The short analysis time (less than 3 min) together with high reproducibility makes the newly developed method applicable to
process control and screening purposes (average of the standard deviations calculated from four repetitive measurements of
six different real samples: ethanol: 0.55 g L–1, glycerol: 0.037 g L–1, glucose: 0.056 g L–1, fructose: 0.036 g L–1, citric acid: 0.020 g L–1, tartaric acid: 0.010 g L–1, malic acid: 0.052 g L–1, lactic acid: 0.012 g L–1 and acetic acid: 0.026 g L–1).
Received: 21 January 1998 / Revised: 5 March 1998 / Accepted: 6 March 1998 相似文献
15.
An improved version of Junmeng–Fang–Weiming–Fusheng approximation for the temperature integral has been developed. The accuracy
of the improved approximation for the temperature integral has been tested by some numerical analyses. The systematic analysis
of the relative errors involved in the kinetic parameters obtained from Junmeng–Fang–Weiming–Fusheng integral method and its
improved version has been also carried out. The results have shown that the improved approximation is more accurate than Junmeng–Fang–Weiming–Fusheng
approximation as the solution of the temperature integral, and that more accurate kinetic parameters can be determined from
the integral method based on the improved temperature integral approximation. 相似文献
16.
1,2,4-triazole-3-one (TO) and guanidine nitrate (GN) have the potential to be used as alternative gas-generating agents. To
obtain a better understanding of thermal decomposition properties of TO/GN mixtures, sealed cell differential scanning calorimetry,
thermogravimetry–differential thermal analysis–infrared spectroscopy (TG–DTA–IR), and thermogravimetry–differential thermal
analysis–mass spectrometry (TG–DTA–MS) were carried out. The endothermic peak and onset temperatures of TO/GN mixtures were
lower than those of individual TO and GN. TG–DTA–IR and TG–DTA–MS showed that the mass of TO/GN mixtures decreased with heat
generation and N2 evolved as the major gas during thermal decomposition. The interaction between TO and nitric acid from the dissociation of
GN is proposed for the thermal decomposition of TO/GN mixtures. 相似文献
17.
V. Shanthi K. Ramanathan Rao Sethumadhavan 《Applied biochemistry and biotechnology》2010,160(5):1473-1483
C–H….π interactions are known to be important contributors to protein stability. In this study, we have analyzed the influence
of C–H….π interactions in single chain “all-alpha” proteins. In the data set, a total of 181 C–H….π interactions were observed.
The most prominent representatives are the interactions between aromatic C–H donor groups and aromatic π acceptors. Eighty-one
percent of the C–H….π interactions between side chain to side chain and remaining19% of the C–H….π interactions were observed
between side-chain to side-chain five-member aromatic ring. The donor atom contribution to C–H….π interactions was mainly
from Phe, Tyr, and Trp residues. The acceptor atom contribution to C–H….π interactions was mainly from Phe, Tyr, Trp, and
His. The highest percentage of C–H….π interactions were observed form Phe residue. The secondary structure preference analysis
of all C–H….π interacting residues showed that Phe, Tyr, Trp, and His preferred to be in helix. Long-range C–H….π interactions
are the predominant type of interactions in single chain all-alpha proteins data set. All the C–H….π interactions forming
residues in the data set preferred to be in the buried region. Seventy-three percent of the donor residues and 65% of the
acceptor residues are highly conserved. 相似文献
18.
Summary The simultaneous quantitation of acids and sugars as their trimethyl silyl (TMS) derivatives has been extended in order to
identify and quantitate the simple acid and sugar constituents in the hydrolyzates of various immunostimulant, water-soluble
polysaccharides obtained from various Basidiomycetes, such as Armillariella mellea, Auricularia auricula-judae, Coriolus versicolor,
Flammulina velutipes, Fomes fomentarius, Ganoderma applanatum, Ganoderma lucidum, Pleurotus ostreatus, Schizophyllum commune,
Trametes hirsuta. Optimum hydrolysis conditions, performed with 2 M trifluoroacetic acid (TFAA) for five hrs, proved the presence
of several sugars and acids with maximum recovery. (i) the total sugar/sugar alcohol content of polysaccharides varied between
20- and 65% and consisted of arabitol (0.01–10.2%), arabinose (0.09–1.3%), ribose (0.2–1.8%), fucose (0.3–1.2%), mannitol
(0.01–5.3%), sorbitol (0.01–0.05%), galactiol (0.04%), fructose (0.08–0.8%), galactose (0.9–29%), glucose (10–53%), uronic
acids (0.14–3.7%), sucrose (0.03–2%), trehalose (0.2–1%), cellobiose (0.01–0.6%), maltose (0.2–1.9%), other disaccharides
(0.2–8%). (ii) The total of acids varied from 1.5 to 30% including o-phosphoric (1.3–19%), malic (0.08–4.7%), citric (0.08–4.7%),
isocitric; (3%) and C16−C18 fatty acids (1–6%). 相似文献
19.
20.
Tomáš Grygar Petr Bezdička Pawel Piszora Emilia Wolska 《Journal of Solid State Electrochemistry》2001,5(7-8):487-494
Electrochemical reductive dissolution of Li–Mn–O and Li–Fe–Mn–O spinels and Li+ extraction/insertion in these oxides were performed using voltammetry of microparticles. Both electrochemical reactions are
sensitive to the Fe/(Fe+Mn) ratio, specific surface area, Li content in tetrahedral positions, and Mn valence, and can be
used for electrochemical analysis of the homogeneity of the elemental and phase composition of synthetic samples. The peak
potential (E
P) of the reductive dissolution of the Li–Mn–O spinel is directly proportional to the logarithm of the specific surface area. E
P of Li–Fe–Mn–O spinels is mainly controlled by the Fe/(Fe+Mn) ratio. Li+ insertion/extraction can be performed with Mn-rich Li–Fe–Mn–O spinels in aqueous solution under an ambient atmosphere and
it is sensitive to the regularity of the spinel structure, in particularly to the amount of Li in tetrahedral positions and
the Mn valence.
Electronic Publication 相似文献