共查询到20条相似文献,搜索用时 15 毫秒
1.
Stefano Livraghi M. Cristina Paganini Mario Chiesa Elio Giamello 《Research on Chemical Intermediates》2006,32(8):777-786
Sulfur contamination of alkaline earth oxide surfaces has important consequences in many fields of chemistry, such as surface
science and catalysis. We used the Electron Paramagnetic Resonance (EPR) technique to study the interaction of CS2 molecules under different pressure and temperature conditions, with the bare and electron-enriched surface of MgO. CS2 reacts on the oxide surface through two distinct reaction paths, one leading to diamagnetic species, the other to paramagnetic
surface entities. Both these reaction paths lead to the fragmentation of the CS2 molecule and, in some cases to oligomerization processes. EPR experiments allowed to follow the formation of the unstable
CS
2
−
radical intermediate and its evolution through formation of several surface radicals like S−, S
3
−
and S
n
−
(n ⩾ 3), depending on the reaction conditions. 相似文献
2.
O<Superscript>−</Superscript> radical anions on oxide catalysts: Formation,properties, and reactions
A systematic in situ EPR study of processes yielding O− radical anions on the surface of oxide dielectrics (MgO, CaO), semiconductors (ZnO, TiO2), supported systems (V/SiO2), and zeolite FeZSM-5 is reported. Methodological approaches to the study of O-radical anions are considered for the cases
in which these species are directly undetectable by EPR. Particular attention is focused on the development of methods of
investigation of so-called α-oxygen on the FeZSM-5 surface, which is an O− radical anion stabilized on the paramagnetic ion Fe3+. The reactions involving α-oxygen and the analogous reactions known for O-radical anions stabilized on the oxide surface
are demonstrated to occur in similar ways. The photostimulated formation of spatially separated electron and hole centers
on the surface of oxide systems is most likely due not to charge separation, but to the spatial separation of the radicals
resulting from the homolytic photodissociation of chemisorbed water. A scheme is suggested for this process on the partially
hydroxylated MgO surface. 相似文献
3.
Thomas Schwab Dr. Matthias Niedermaier Dr. Gregor A. Zickler Dr. Milan Ončák Prof. Dr. Oliver Diwald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):16049-16056
Atomic dispersion of dopants and control over their defect chemistry are central goals in the development of oxide nanoparticles for functional materials with dedicated electronic, optical or magnetic properties. We produced highly dispersed oxide nanocubes with atomic distribution of cobalt ions in substitutional sites of the MgO host lattice via metal organic chemical vapor synthesis. Vacuum annealing of the nanoparticle powders up to 1173 K has no effect on the shape of the individual particles and only leads to moderate particle coarsening. Such materials processing, however, gives rise to the electronic reduction of particle surfaces, which—upon O2 admission—stabilize anionic oxygen radicals that are accessible to UV/Vis diffuse reflectance and electron paramagnetic resonance (EPR) spectroscopy. Multi-reference quantum chemical calculations show that the optical bands observed mainly originate from transitions into 4A2g (4F), 4T1g (4P) states with a contribution of transitions into 2T1g, 2T2g (2G) states through spin-orbit coupling and gain intensity through vibrational motion of the MgO lattice or the asymmetric ion field. Related nanostructures are a promising material system for single atomic site catalysis. At the same time, it represents an extremely valuable model system for the study of interfacial electron transfer processes that are key to nanoparticle chemistry and photochemistry at room temperature, and in heterogeneous catalysis. 相似文献
4.
O. Martins J.Y. Buzaré J. Emery P. Claudy J.M. LéTOFFé V. Brandel M. Genet 《Journal of Sol-Gel Science and Technology》1997,8(1-3):315-319
Different transparent phosphate xerogels were synthesized using concentrated solutions of metal chlorides and phosphoric acid
with a proper mole ratio of both components. By this method we prepared bulk samples of thorium and tin(IV) phosphate xerogels
by drying at room temperature or at 350 K. Some properties of these amorphous materials were studied by means of differential
scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) techniques. Depending on mole ratio metal/phosphate,
these xerogels show, near 180 K, inflection points which we interpret asT
g
. Samples dried at 425 K lose their transparency and have noT
g
. Thus, it seems that the “glassy” state is due to water molecules remaining in the material. The same properties were confirmed
by EPR studies of the xerogels doped with Cr3+ and Fe3+ ions as probes. These results show the existence of two different phases in the xerogels: a liquid-like one, in the range
from 190 K to 350 K and a solid-like one, in the range from 4 K to 190 K. 相似文献
5.
Feng-Yun Wang Soofin Cheng Chen-Hung Chung Ben-Zu Wan 《Journal of Solid State Electrochemistry》2006,10(11):879-885
Electrolytes of Ce1-x-y
Y
x
Mg
y
O2-0.5x-y
were prepared with citrate method and were characterized by inductively coupled plasma-atomic emission spectrometry, energy dispersive spectrometry, powder X-ray diffraction, and impedance spectroscopy. The effect of composition on the structure, conductivity, and stability of the electrolytes were investigated. When 0≤x≤ about 0.2 and 0≤y≤ about 0.05, the electrolytes were all single phase materials of ceria-based solid solution. However, when y> about 0.05, the electrolytes became two-phase materials, Y3+ and Mg2+ co-doped ceria-based solid solution and free MgO. The sample with nominal composition of Ce0.815Y0.065Mg0.12O2-d
showed ionic conductivity at 973 K close to or even a little higher than that of similarly prepared Ce0.9Gd0.1O1.95, but had lower cost of raw materials and a little better stability in reducing atmosphere. The existing of free MgO improved the stability of the electrolytes in reducing atmosphere, but too much free MgO reduced the conductivity. 相似文献
6.
Crystallization, morphology and mechanical properties of a spodumene-diopside glass ceramics with adding different amount
of CaO and MgO in Li2O-Al2O3-2SiO2 were investigated. With CaO and MgO addition, the crystallization temperature (T
p) decreased, the value of Avrami constant (n) decreased from 3.2±0.3 to 1.4±0.2, the activation energy (E) increased from 299±3 kJ mol−1 to 537±5 kJ mol−1. The crystalline phases precipitated were h-quartz solid solution, β-spodumene and diopside. The mechanism of crystallization of the glass ceramics changed from bulk
crystallization to surface crystallization. The grain sizes and thermal expansion coefficients increased while flexural strength
and fracture toughness of the glass-ceramics increased first, and then decreased. The mechanical properties were correlated
with crystallization and morphology of glass ceramics. 相似文献
7.
J. Goslar M. Wojciechowska M. Pietrowski M. Zieliński 《Research on Chemical Intermediates》2007,33(8):841-851
Electron paramagnetic resonance (EPR) and infrared (IR) spectroscopy were used to study the formation of ruthenium and adsorbed
species appearing on the catalyst upon the adsorption of CO and O2 on 1.37 wt% Ru/MgF2 catalysts derived from Ru3(CO)12. The presence of Ru
x+ sites in spite of a reductive H2 treatment at 673 K was observed by EPR and IR spectroscopy beside metallic Ru0 species. Both IR and EPR results provided clear evidence for the interaction between surface ruthenium and probe molecules.
The IR spectra recorded after admission of CO showed a band at approx. 2000 cm−1, due to linearly adsorbed CO on Ru0/MgF2 and two bands at higher frequencies (approx. 2140 and approx. 2070 cm−1), related to CO on oxidized Ru
n+ species, e.g., to Ru(CO)3 complex with Ru in the 1+ and/or 2+ state of oxidation and Ru(CO)2 with Ru in the 3+ and/or 4+ state of oxidation. A weak anisotropic EPR signal with g
‖ = 2.017 and g
⊥ = 2.003 is due to O
2
−
radicals and a formation of Ru4+-O
2
−
complex is postulated. The Ru3+ appears to oxidize to Ru4+ and the resulting dioxygen anion is coordinated to the ruthenium. The strong, isotropic EPR signal at g
0 = 2.003 detected upon admission of CO is attributed to CO radical anion rather than to any ruthenium carbonyl complexes. 相似文献
8.
E. Ya. Misochko A. V. Akimov V. F. Lavitskii S. V. Chapyshev 《Russian Chemical Bulletin》2007,56(12):2364-2369
An EPR spectrum of solid Ar isolated quintet 4-amino-3,5-dichloropyridin-2,6-diyldinitrene that formed by the photolysis of
4-amino-2,6-diazido-3,5-dichloropyridine at 15 K was recorded. Using computer simulation based on numerical diagonalization
of the quintet spin Hamiltonian matrices, it was established that this EPR spectrum corresponds to a quintet spin state with
the magnetic parameters g = 2.0023, |D
q| = 0.2100 cm−1, and |E
q| = 0.0560 cm−1. Owing to high resolution of the experimental spectrum, the zero-field splitting parameters of the quintet intermediate were
determined to an accuracy of at least 5·10−4 cm−1. Calculations of the fine-structure energy levels in external magnetic field and the dependences of the EPR signal positions
and intensities of the quintet dinitrene on the direction of external magnetic field were performed for the first time. This
allowed unambiguous assignment of all EPR lines of quintet molecules having both in-principal-axis and off-principal-axis
orientations.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2284–2289, December, 2007. 相似文献
9.
Ultra-high-molecular-weight polyethylene (Mˉ
v: 5 × 106, 100-times elongated film) was irradiated with γ-rays under a 1,3-butadiene atmosphere at room temperature. Electron paramagnetic
resonance (EPR) measurements indicated that the radicals formed on the polyethylene substrate during the irradiation were
short-lived. EPR, Fourier transform IR spectroscopy, solid-state NMR, and differential scanning calorimetry of the as-irradiated
materials indicated that butadiene molecules were covalently bound to the polyethylene chains as pendant groups bearing trans-vinylene and vinyl functions in a ratio of 3:1. Some crosslinks among the pendants, or between pendants and the main chains
were produced. The number of unsaturated pendants introduced (including bridges) per carbon atom of the polyethylene main
chain was dependent on the irradiation dose and the butadiene pressure, and was 0.096 butadiene units for 10 kGy irradiation
under a 304 kPa butadiene atmosphere. The unsaturated pendants or bridges on the polyethylene chain thus introduced may be
good targets to functionalize polyethylene by covalent modification.
Received: 22 February 1999 Accepted in revised form: 30 June 1999 相似文献
10.
Exploring the physical,chemical and thermal characteristics of a new potentially insensitive high explosive RX-55-AE-5 总被引:1,自引:0,他引:1
R. K. Weese A. K. Burnham Heidi C. Turner T. D. Tran 《Journal of Thermal Analysis and Calorimetry》2007,89(2):465-473
Current work at Lawrence Livermore National Laboratory (LLNL) includes both understanding properties of old explosives and
measuring properties of new ones. The necessity to know and understand the properties of energetic materials is driven by
the need to improve performance and enhance stability to various stimuli, such as thermal, friction and impact insult.
This paper will concentrate on the physical properties of RX-55-AE-5, which is formulated from heterocyclic explosive, 2,6-diamino-3,5-dinitropyrazine-1-oxide,
LLM-105, and 2.5% Viton A. Differential scanning calorimetry (DSC) was used to measure a specific heat capacity, C
p, of≈0.950 J g−1 °C−1, and a thermal conductivity, κ, of≈0.475 W m−1 °C−1. The LLNL kinetics modeling code Kinetics05 and the Advanced Kinetics and Technology Solutions (AKTS) code thermokinetics
were both used to calculate Arrhenius kinetics for decomposition of LLM-105. Both obtained an activation energy barrier E≈180 kJ mol−1 for mass loss in an open pan. Thermal mechanical analysis, TMA, was used to measure the coefficient of thermal expansion
(CTE). The CTE for this formulation was calculated to be ≈61 μm m−1 °C−1. Impact, spark, friction are also reported. 相似文献
11.
Hongbo Guan Pei Wang Biying Zhao Yuexiang Zhu Youchang Xie 《Frontiers of Chemistry in China》2007,2(2):204-208
Nanometer MgO samples with high surface area, small crystal size and mesoporous texture were synthesized by thermal decomposition
of MgC2O4 · 2H2O prepared from solid-state chemical reaction between H2C2O4 · 2H2O and Mg (CH3COO)2 · 4H2O. Steam produced during the decomposition process accelerated the sintering of MgO, and MgO with surface area as high as
412 m2 · g−1 was obtained through calcining its precursor in flowing dry nitrogen at 520°C for 4 h. The samples were characterized by
X-ray diffraction, N2 adsorption, transmission electron microscopy, thermogravimetry, and differential thermal analysis. The as-prepared MgO was
composed of nanocrystals with a size of about 4–5 nm and formed a wormhole-like porous structure. The MgO also had good thermal
stability, and its surface areas remained at 357 and 153 m2·g−1 after calcination at 600 and 800°C for 2 h, respectively. Compared with the MgO sample prepared by the precipitation method,
MgO prepared by solid-state chemical reaction has uniform pore size distribution, surface area, and crystal size. The solid-state
chemical method has the advantages of low cost, low pollution, and high yield, therefore it appears to be a promising method
in the industrial manufacture of nanometer MgO.
Translated from Chinese Journal of Catalysis, 2006, 27(9): 793–798 (in Chinese) 相似文献
12.
G. M. Larin A. N. Gusev Yu. V. Trush K. V. Rabotyagov V. F. Shul’gin G. G. Aleksandrov I. L. Eremenko 《Russian Chemical Bulletin》2007,56(10):1964-1971
Spacer-armed dinuclear copper(II) complexes with condensation products of isophthalic and terephthalic acid dihydrazides with salicylaldehyde and 2-hydroxyacetophenone
were synthesized and studied by EPR and X-ray diffraction. The compositions and structures of most of the complexes were determined
by elemental analysis, thermogravimetric analysis, and IR spectroscopy. The structure of the copper(II) complex with acyldihydrazone of salicylaldehyde and 1,3-benzenedicarboxylic acid (H4L) with the composition [Cu2L1·2morph·MeOH] (morph is morpholine) was established by X-ray diffraction. The CuII atoms are spaced by 10.29 Å and are structurally nonequivalent. One copper cation has a square-planar coordination formed
by donor atoms (2 N + O) of the doubly deprotonated acylhydrazine fragment and the N atom of the morpholine molecule. The
second copper atom is additionally coordinated by a methanol molecule through the oxygen atom, so that this copper atom is
in a tetragonal-pyramidal coordination with the oxygen atom in the axial position. The EPR spectra of liquid solutions of
the complexes based on 1,4-benzenedicarboxylic acid acyldihydrazones and 1,3-benzenedicarboxylic acid bis(salicylidene)hydrazone
at room temperature show a four-line hyperfine structure with the constant a
Cu = 54.4–67.0·10−4 cm−1 (g = 2.105–2.147), which is indicative of the independent behavior of the paramagnetic centers. The EPR spectrum of a solution
of the complex based on isophthalic acid and 2-hydroxyacetophenone shows the seven-line hyperfine structure corresponding
to two equivalent copper nuclei (g = 2.11, a
Cu = 36.5·10−4 cm−1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1898–1905, October, 2007. 相似文献
13.
Sulekh Chandra Rachna Gupta Nidhi Gupta Sukhwant Singh Bawa 《Transition Metal Chemistry》2006,31(2):147-151
Copper(II) macrocyclic complexes have been synthesized with five novel ligands: L1-1,7,10,16-tetraaza-2,6,11,15-tetraone-4,13-dithiacycloocta-decane, L2-1,7,11,17-tetraaza-2,6,12,16-tetraone-4,14-dithia-cyclocosane, L3-1,7,10, 13,19,22-hexaaza-2,6,14,18-tetraone-4,16-dithiacyclo-tetracosane, L4-1,7,14,20,tetraaza-2,6,15,19-tetraone-4,17,di- thiatricyclo [22, 4, O21,26, O8,13] hexacosa-8,10,12,21,23,25-hexene, L5- 1,7,13,19,25,26-hexaaza-2,6,14,18 tetraone-4,16 dithia tricyclo [23, 3, 1, I8,12] hexacosa [8(26), 10, 12, 20(25), 22, 24] hexane and characterized by elemental analysis, molar conductance, magnetic susceptibility,
i.r, u.v.–vis, EPR spectral studies, thermal studies and electrochemical properties. The molar conductance measurements of
the complexes in DMSO correspond to 1:2 electrolytes. g-Values are calculated for all of the complexes in the polycrystalline form as well as in DMSO solution. On the basis of i.r,
electronic and EPR spectral studies a square planar geometry has been assigned to these complexes. Cyclic voltammograms for
all the complexes are similar to quasi-reversible redox processes CuIICuII⇆CuIICuI⇆CuICuI. The complexes were also evaluated against the growth of bacteria (S. fecalis and E.coli) in vitro.
An erratum to this article is available at . 相似文献
14.
T. López E. Ortiz R. Gómez M. Picquart 《Journal of Sol-Gel Science and Technology》2006,37(3):189-193
Samples of amorphous sol-gel titania were prepared at 50%wt with tungstophosphoric or molybdophosphoric acid. The resulting
gels were dried and annealed at 100, 150 and 200°C and studied by FT-IR, UV-Vis, EPR, TGA and Raman spectroscopy. By FT-IR
the evolution of the stretching vibration of the OH groups (3450–3700 cm−1) was followed. The intensity of this band decreased as the annealing temperature increased. With UV-Vis spectroscopy the
band gap was determined for each sample, and the Eg was found between 2.72 and 3.38 eV. Raman spectroscopy revealed the formation
of Mo—O—Ti and W—O—Ti—O bonds. An intense EPR signal at g = 1.998 was observed during annealing of the samples. Amorphous solids with a significant number of vacancies and promising
photocatalytic properties were obtained. 相似文献
15.
Galactose oxidase (GOase) is a fungal enzyme which is unusual among metalloenzymes in appearing to catalyse the two electron
oxidation of primary alcohols to aldehydes and H2O2. The crystal structure of the enzyme reveals that the coordination geometry of mononuclear copper(II) ion is square pyramidal,
with two histidine imidazoles, a tyrosinate, and either H2O (pH 7.0) or acetate (from buffer,pH 4-5) in the equatorial sites and a tyrosinate ligand weakly bound in the axial position. This paper summarizes the results
of our studies on the structure, spectral and redox properties of certain novel models for the active site of the inactive
form of GOase. The monophenolato Cu(II) complexes of the type [Cu(L1)X][H(L1) = 2-(bis(pyrid-2-ylmethyl)aminomethyl)-4-nitrophenol and X− = Cl−
1, NCS−
2, CH3COO−
3, ClO4
−
4] reveal a distorted square pyramidal geometry around Cu(II) with an unusual axial coordination of phenolate moiety. The coordination
geometry of 3 is reminiscent of the active site of GOase with an axial phenolate and equatorial CH3COO− ligands. All the present complexes exhibit several electronic and EPR spectral features which are also similar to the enzyme.
Further, to establish the structural and spectroscopic consequences of the coordination of two tyrosinates in GOase enzyme,
we studied the monomeric copper(II) complexes containing two phenolates and imidazole/pyridine donors as closer structural
models for GOase. N,N-dimethylethylenediamine and N,N’-dimethylethylenediamine have been used as starting materials to obtain
a variety of 2,4-disubstituted phenolate ligands. The X-ray crystal structures of the complexes [Cu(L5)(py)], (8) [H2(L5) = N,N-dimethyl-N’,N’-bis(2-hydroxy-4-nitrobenzyl) ethylenediamine, py = pyridine] and [Cu(L8)(H2O)] (11), [H2(L8) = N,N’-dimethyl-N,N’-bis(2-hydroxy-4-nitrobenzyl)ethylenediamine] reveal distorted square pyramidal geometries around Cu(II) with the axial tertiary
amine nitrogen and water coordination respectively. Interestingly, for the latter complex there are two different molecules
present in the same unit cell containing the methyl groups of the ethylenediamine fragmentcis to each other in one molecule andtrans to each other in the other. The ligand field and EPR spectra of the model complexes reveal square-based geometries even in
solution. The electrochemical and chemical means of generating novel radical species of the model complexes, analogous to
the active form of the enzyme is presently under investigation. 相似文献
16.
Reactions of photogenerated fluorine atoms with C60 fullerene molecules isolated in solid argon were studied by EPR spectroscopy in the temperature range from 15 to 25 K. Highly
resolved anisotropic EPR spectrum of the FC60
⋅ radical was obtained for the first time. The spectrum is characterized by low anisotropy of the g-tensor and by axially symmetric HFC tensor on 19F nuclei. The parameters of the HFC tensor for 19F magnetic nuclei were determined. The isotropic HFC constant A
iso equals 202.8 MHz and the anisotropic magnetic dipole-dipole interaction constant A
dip equals 51.8 MHz. Quantum chemical calculations of FC60
⋅ radical showed that the PBE1/Λ22m method (PBE1 functional and the correlation triple-zeta basis sets augmented with polarization
functions on inner atomic shells) provides good agreement between the theoretical magnetic parameters and experimental data.
Specific features of the spin density distribution in the FC60
⋅ radical are discussed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 424–428, March, 2007. 相似文献
17.
《Magnetic resonance in chemistry : MRC》2002,40(6):381-386
A variety of surface anion vacancies, or point defects, are created by high‐temperature activation of a series of polycrystalline alkaline earth metal oxides (MgO, CaO and SrO). Subsequent UV irradiation of the activated oxide under a hydrogen atmosphere results in the generation of surface colour centres [FS+(H)], by electron trapping at these anion vacancies. The paramagnetic properties of these colour centres were studied by EPR and ENDOR spectroscopy. 1H ENDOR spectroscopy revealed that a well defined heterogeneity of trapped electron species exists on each oxide surface, as characterized by the different superhyperfine couplings between the trapped electron and the nearby proton of the FS+ (H) centre. On MgO and CaO two dominant FS+ (H) centres were identified (labelled sites I and II) whereas on SrO three FS+ (H) species were found (sites I, II and III). The possible surface sites responsible for electron stabilization are discussed, and include a 3C corner mono‐vacancy, a 4C mono‐vacancy and an anion–cation di‐vacancy. The results indicate that regardless of the oxide used, a common degree of morphological similarities exists on each oxide. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
18.
Grazyna Strzelczak Edyta Janeba-Bartoszewicz Ian Carmichael Bronislaw Marciniak Krzysztof Bobrowski 《Research on Chemical Intermediates》2009,35(4):507-517
Radicals formed in γ-irradiated 1,3,5-trithiane (TT) and its three derivatives, α- and β-2,4,6-trimethyl-1,3,5-trithiane (α-TMT
and β-TMT), and 2,4,6-trimethyl-2,4,6-triphenyl-1,3,5-trithiane (TMTPT), were studied by the electron paramagnetic resonance
(EPR) method in the solid state. The sulfur radical cations (>S+•) were identified in all compounds at 77 K. In TT and its two derivatives, α-TMT and β-TMT, the >S+• decay via deprotonation-forming C-centered radicals. Further increase of temperature up to 293 K results in the appearance
of thiyl-type radicals (RS•). In TMTPT, the >S+• are stable up to 250 K. They formed the intermolecularly three-electron-bonded dimeric radical cations (S∴S)+ while RS• radicals were not observed. Some of the radical assignments and their EPR parameters (g and a hyperfine splittings) obtained support from the DFT calculations. 相似文献
19.
Density functional theory, in combination with a) a careful choice of the exchange-correlation part of the total energy and b) localized basis sets for the electronic orbitals, has become the method of choice for calculating the exchange-couplings
in magnetic molecular complexes. Orbital expansion on plane waves can be seen as an alternative basis set especially suited
to allow optimization of newly synthesized materials of unknown geometries. However, little is known on the predictive power
of this scheme to yield quantitative values for exchange coupling constants J as small as a few hundredths of eV (50–300 cm−1). We have used density functional theory and a plane waves basis set to calculate the exchange couplings J of three homodinuclear Cu-based molecular complexes with experimental values ranging from +40 cm−1 to −300 cm−1. The plane waves basis set proves as accurate as the localized basis set, thereby suggesting that this approach can be reliably
employed to predict and rationalize the magnetic properties of molecular-based materials.
Corresponding author. E-mail: Carlo.Massobrio@ipcms.u-strasbg.fr
Received August 5, 2002; accepted August 9, 2002 相似文献
20.
Thermal
and structural properties of model silicate-phosphate glasses containing the
different amounts of the glass network modifiers, i.e. Mg2+
and Ca2+ were studied. To explain the changes of
the parameters characterizing the glass transition effect (Tg, Δcp) and the crystallization
process (Tc, ΔH) depending on the cations modifiers additions,
analysis of the bonds and chemical interactions of atoms in the structure
of glasses was used.
31P
MAS-NMR spectra of SiO2–P2O5–MgO(CaO)–K2O glasses show that the phosphate complexes are mono- and diphosphate. It
has been found that increasing amounts of Mg2+
or Ca2+ cations in the structure of glasses causes
the reduction of the degree of polymerization of the phosphate framework (Q1→Q0).
The influence of increasing of modifiers in the structure of silicate- phosphate
glasses on the number of non-bridging oxygens per SiO4
tetrahedron and density of glasses was presented. 相似文献