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1.
Marcin Środa 《Journal of Thermal Analysis and Calorimetry》2009,97(1):239-243
Glasses have been synthesized in the system SiO2–Al2O3–Na2O–AlF3–LaF3–Er2O3. A base glass (in mol% 67SiO2–9Al2O3–20Na2O–Al2F6–3La2F6) was modified by 0.5, 0.75, 1, 1.25, 1.5, 2 and 5 mol% Er2O3, respectively. Glasses were prepared by conventional fusion method from 20 g batches. The glass transition temperature (T
g), the jump-like changes of the specific heat (ΔC
p) accompanying the glass transition and the enthalpy of crystallization (ΔH) were calculated. DTA measurements clearly reveal that the increase of the Er2O3 content in the glass changes the effects of crystallization and diminishes the thermal stability of the glassy network. In
the same time the changes in the transition temperature are observed. The formation of NaLaF4 and Na1.45La9.31(SiO4)6(F0.9O1.1) as a main phase was confirmed. The diminishing of the thermal stability was connected with erbium which incorporated into
Na1.45La9.31(SiO4)6(F0.9O1.1) structure. 相似文献
2.
Magdalena Szumera Irena Wacławska Zbigniew Olejniczak 《Journal of Thermal Analysis and Calorimetry》2010,99(3):879-886
Glasses of the SiO2–P2O5–K2O–MgO–CaO–B2O3 system acting as nutrients carriers in the soil environment were synthesised by the melt-quenching technique. Thermal properties
were studied using DTA/DSC methods and the influence of B2O3 and P2O5 content on thermal stability and crystallization process of these glasses was examined. The structure of the glass network
was characterized by FTIR, 31P, and 11B MAS NMR. The chemical activity of the glasses in the 2 mass% citric acid solution was measured by the ICP-AES method. The
analysis indicated that the formation of P–O–B units with chemically stable tetrahedral borate groups decreases the glass
solubility in conditions simulating the soil environment. 相似文献
3.
M. Środa 《Journal of Thermal Analysis and Calorimetry》2007,88(1):245-249
Oxyfluoride glass-ceramics
based on the aluminosilicate glass-matrix with the nano-phase of fluoride
is an interesting material for optoelectronics. A new glass from the SiO2–B2O3–Na2O–LaF3 system
in which nanocrystallization of LaF3 could be obtained
as well is presented.
Thermal stability of glass and the crystalline
phases formed upon heat treatment were determined by DTA/DSC and XRD methods,
respectively. The effect of the glass composition on thermal stability was
investigated by the SEM method.
It has been found that the addition
of LaF3 increases the tendency to decomposition of
the borosilicate glass. In glasses with the ratio B2O3/(Na2O+3La2F6)<1 it is possible to obtain the immersed crystallization
of LaF3 in transparent glassy matrix. The process is
preceded by LaOF formation. Glasses with the composition B2O3/(Na2O+3La2F6)≥1 revealed the tendency to La(BSiO5)
crystallization. 相似文献
4.
H. C. Vasconcelos 《Journal of Sol-Gel Science and Technology》2010,55(1):126-133
SiO2-TiO2-PO2,5 (STP) and SiO2-TiO2-AlO1,5 (STA) glasses were prepared by sol-gel processing. Their infrared absorption spectra (IR), differential thermal analysis
curves (DTA) and X-ray diffraction patterns (XRD) have been recorded. In the SiO2-TiO2 system, the chemical homogeneity of the sol-gel glass could be evaluated by the relative concentration of Si-O-Ti heterocondensation
comparing to Si-O-Si homocondensation. For the STA system, a gradual decrease of the Si-O-Ti/Si-O-Si band ratio (based on
IR spectra) with the addition of Al2O3 is observed, with the simultaneous formation of Si-O-Al and Ti-O-Al bounds, i.e Al3
+ ions are dissolved in the SiO2-TiO2 glass matrix and do not promote glass-in-glass phase-separation in the composition range of 0–15 mol% AlO1.5. In the STP system, on the other hand, P=O bond IR stretch in the ternary glasses indicates that P=O free PO2O2/2
− tetrahedra are formed, rather than the double bonded POO3/2 tetrahedra that usually occur in binary SiO2-P2O5 glasses. It can be concluded that SiO2-TiO2-P2O5 glass separates into a SiO2-rich phase and a TiO2(P2O5)-rich phase. During heat-treatment in STA system only anatase precipitates, even at T ~ 1,000 °C, while in for STP, anatase (TiO2) or (TiO)2P2O7 (TOP) crystals precipitate at ~600 °C, depending on the P2O5 concentration. The major crystal phase, cristobalite, precipitated at ~1,000 °C and at ~1,200 °C, the P-containing phase
melts. 相似文献
5.
The effects of gamma irradiation on crystallization kinetics and microhardness properties of the Li2O–Al2O3–SiO2 (LAS) glass–ceramic sample have been investigated. The glass–ceramic was irradiated to γ-source 60Co of 0.7 MGy. The crystallization kinetics of the irradiated and non-irradiated samples were characterized using differential
scanning calorimetry. The crystallization kinetics and microhardness properties of the glass–ceramic changed the gamma irradiation,
and the high dose of gamma irradiation affects significantly the crystallization kinetics and microhardness properties of
the Li2O–Al2O3–SiO2 glass–ceramic sample. 相似文献
6.
Marcela Stoia C. Caizer M. Stefanescu P. Barvinschi I. Julean 《Journal of Thermal Analysis and Calorimetry》2007,88(1):193-200
This article presents the results
of our investigation on the obtaining of Ni0.65Zn0.35Fe2O4 ferrite nanoparticles embedded in a SiO2 matrix using
a modified sol–gel synthesis method, starting from tetraethylorthosilicate
(TEOS), metal (FeIII,NiII,ZnII)
nitrates and ethylene glycol (EG). This method consists in the formation of
carboxylate type complexes, inside the silica matrix, used as forerunners
for the ferrite/silica nanocomposites. We prepared gels with different compositions,
in order to obtain, through a suitable thermal treatment, the nanocomposites
(Ni0.65Zn0.35Fe2O4)x–(SiO2)100–x (where x=10,
20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential
thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy.
The formation of Ni–Zn ferrite in the silica matrix and the behavior
in an external magnetic field were studied by X-ray diffraction (XRD) and
quasi-static magnetic measurements (50 Hz). 相似文献
7.
Electrical conductivity in the monoclinic Li2TiO3, cubic Li1.33Ti1.67O4, and in their mixture has been studied by impedance spectroscopy in the temperature range 20–730 °C. Li2TiO3 shows low lithium ion conductivity, σ300≈10–6 S/cm at 300 °C, whereas Li1.33Ti1.67O4 has 3×10–8 at 20 °C and 3×10–4 S/cm at 300 °C. Structural properties are used to discuss the observed conductivity features. The conductivity dependences
on temperature in the coordinates of 1000/T versus loge(σT) are not linear, as the conductivity mechanism changes. Extrinsic and intrinsic conductivity regions are observed. The change
in the conductivity mechanism in Li2TiO3 at around 500–600 °C is observed and considered as an effect of the first-order phase transition, not reported before. Formation
of solid solutions of Li2–
x
Ti1+
x
O3 above 900 °C significantly increases the conductivity. Irradiation by high-energy (5 MeV) electrons causes defects and the
conductivity in Li2TiO3 increases exponentially. A dose of 144 MGy yields an increase in conductivity of about 100 times at room temperature.
Electronic Publication 相似文献
8.
Nano-structured spinel Li2Mn4O9 powder was prepared via a combustion method with hydrated lithium acetate (LiAc·2H2O), manganese acetate (MnAc2·4H2O), and oxalic acid (C2H2O4·2H2O) as raw materials, followed by calcination of the precursor at 300 °C. The sample was characterized by X-ray diffraction,
scanning electron microscope, and energy-dispersive X-ray spectroscopy techniques. Electrochemical performance of the nano-Li2Mn4O9 material was studied using cyclic voltammetry, ac impedance, and galvanostatic charge/discharge methods in 2 mol L−1 LiNO3 aqueous electrolyte. The results indicated that the nano-Li2Mn4O9 material exhibited excellent electrochemical performance in terms of specific capacity, cycle life, and charge/discharge
stability, as evidenced by the charge/discharge results. For example, specific capacitance of the single Li2Mn4O9 electrode reached 407 F g−1 at the scan rates of 5 mV s−1. The capacitor, which is composed of activated carbon negative electrode and Li2Mn4O9 positive electrode, also exhibits an excellent cycling performance in potential range of 0–1.6 V and keeps over 98% of the
maximum capacitance even after 4,000 cycles. 相似文献
9.
The processes of nucleation of Li2O-Al2O3-SiO2 glasses with TiO2 and TiO2+ZrO2 as nucleating agents were discussed. The DTA peak temperature and DTA peak height shown a strong dependence on the nucleation temperature in the glass with TiO2, while in the glass with TiO2+ZrO2 this tendency was small. The optimum nucleation temperatures were 745 and 760°C for two glasses. It suggested that with TiO2+ZrO2 as nucleating agents, the crystallization had lower sensitivity for nucleation temperature, and the glass had higher nucleation efficiency than with TiO2. 相似文献
10.
Li Chen Haixia Shen Zhen Lu Cang Feng Su Chen Yanru Wang 《Colloid and polymer science》2007,285(13):1515-1520
TiO2–SiO2 composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO2–SiO2 composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO2–SiO2) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO2–SiO2 composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO2–SiO2 composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO2–SiO2 core surface via surface functionalized reaction. The particle size of TiO2–SiO2 composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and
Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid
films. The average particle size of the TiO2–SiO2 composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO2–SiO2 composite nanoparticles are well dispersed in the PU matrix. 相似文献
11.
Junqing Dou Xueya Kang Tuerdi Wumaier Hongwei Yu Ning Hua Ying Han Guoqing Xu 《Journal of Solid State Electrochemistry》2012,16(4):1481-1486
The effect of the lithium boron oxide glass coating on the electrochemical performance of LiNi1/3Co1/3Mn1/3O2 has been investigated via solution method. The morphology, structure, and electrochemical properties of the bare and coated
LiNi1/3Co1/3Mn1/3O2 are characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and charge–discharge
tests. The results showed that the lattice structure of LiNi1/3Co1/3Mn1/3O2 is not changed after coating. The coating sample shows good high-rate discharge performance (148 mAh g−1 at 5.0 C rate) and cycling stability even at high temperature (with the capacities retention about 99% and 87% at room and
elevated temperature after 50 cycles). The Li+ diffusion coefficient is also largely improved, while the charge transfer resistance, side reactions within cell, and the
erosion of Hydrofluoric Acid all reduced. Consequently, the good electrochemical performances are obtained. 相似文献
12.
Xiangzhong Ren Yingkai Jiang Peixin Zhang Jianhong Liu Qianling Zhang 《Journal of Sol-Gel Science and Technology》2009,51(2):133-138
One-dimensional (1D) submicron-belts of V2O5 have been prepared by a sol–gel route using V2O5, H2O2 and aniline as starting materials. Thermogravimetric and differential thermal analysis, X-ray diffraction, Fourier transform
infrared spectroscopy and scanning electron microscopy were employed to characterize the samples. Electrochemical behaviors
as cathode material in rechargeable lithium-ion batteries were investigated by galvanostatic charge–discharge measurement
and cyclic voltammeter. The results showed that the synthesized V2O5 appeared to be submicron-belts and orthorhombic structure. The V2O5 submicron-belts exhibited a high initial discharge capacity of 346 mAh/g and stayed 240 mAh/g after 20 cycles at 0.1 C discharge
rate in the potential region 1.8–4.0 V. 相似文献
13.
Žaneta Dohnalová Petra Šulcová Miroslav Trojan 《Journal of Thermal Analysis and Calorimetry》2010,101(3):973-978
The main aim of this work was to synthesize the magnesium orthostannate doped by terbium cations and tested whether these
materials can be used for colouring of the different materials, e.g. organic binder and ceramic glazes. Initial composition
of pigments was counted according the general formula 2MgO(1 − x)SnO2–xTbO2, where values of x varied from 0.1 to 0.5 in 0.1 steps. The simultaneous TG/DTA measurements of mixture containing tin oxide, magnesium carbonate
hydroxide and terbium oxide showed that the formation of a new compound started at temperature 1,029 °C, but single-phase
system was not prepared. Granulometric compositions of samples that were prepared by calcining at temperatures 1,300–1,400 °C
are characterized by values of median (d
50) in range 4–8 μm. The calcining temperature 1,500 °C caused the increase of the particle sizes at around 12 μm. The composition
of sample 2MgO–1.5SnO2–0.5TbO2 and heating temperature 1,500 °C are the most suitable conditions for preparation of colourfully interesting pigment that
can be recommended also for colouring of ceramic glazes. Especially, for colouring of decorative lead containing glaze G 07091
containing 5 wt% of PbO and 8 wt% of Al2O3. 相似文献
14.
Jianxia Jiao Qun Xu Limin Li Takano Tsubasa Takaomi Kobayashi 《Colloid and polymer science》2008,286(13):1485-1491
Titania–silica composite have been prepared using polyethylene glycol (PEG) with different molecular weights (M
w), PEG20000, PEG10000, and PEG2000, as template in supercritical carbon dioxide (SC CO2). The composite precursors were dissolved in SC CO2 and impregnated into PEG templates using SC CO2 as swelling agent and carrier. After removing the template by calcination at suitable temperature, the titania–silica composite
were obtained. The composite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen
sorption–desorption experiment. Photocatalytic activity of the samples has been investigated by photodegradation of methyl
orange. Results indicate that there are many Si–O–Ti linkages in the TiO2/SiO2 composite; the PEG template has a significant influence on the structure of TiO2/SiO2. In addition, the TiO2/SiO2 prepared with PEG10000 exhibited high photocatalytic efficiency. So this work supplies a clue to control and obtain the TiO2/SiO2 composite with different photocatalytic reactivity with the aid of suitable PEG template in supercritical CO2. 相似文献
15.
Structural and thermal properties of the 20Li2O-80TeO2 glass were studied using X-ray diffraction analysis and differential scanning calorimetry techniques to understand and control
the crystallization process on this glass. The γ-TeO2, α-TeO2 and α-Li2Te2O5 phases were identified during the crystallization in this glass. Activation energies and Avrami exponent n were calculated
from non-isothermal measurements for glasses with different particle size. The mean values of Avrami exponent were obtained for glasses with 63–75 and 45–63 μm particle sizes such as , but glasses with particle size 38–45 μm and smaller than 38 g,m presented . 相似文献
16.
Nopsiri Chaiyo Rangson Muanghlua Surasak Niemcharoen Banjong Boonchom Panpailin Seeharaj Naratip Vittayakorn 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1023-1029
The thermal transformation of Na2C2O4 was studied in N2 atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na2C2O4 and its decomposed product were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique
(XRD). The non-isothermal kinetic of the decomposition was studied by the mean of Ozawa and Kissinger–Akahira–Sunose (KAS)
methods. The activation energies (E
α) of Na2C2O4 decomposition were found to be consistent. Decreasing E
α at increased decomposition temperature indicated the multi-step nature of the process. The possible conversion function estimated
through the Liqing–Donghua method was ‘cylindrical symmetry (R2 or F1/2)’ of the phase boundary mechanism. Thermodynamic functions (ΔH*, ΔG* and ΔS*), calculated by the Activated complex theory and kinetic parameters, indicated that the decomposition step is a high energy
pathway and revealed a very hard mechanism. 相似文献
17.
Vinícius D. Araújo Waldir Avansi Elaine C. Paris Lauro J. Q. Maia Maria I. B. Bernardi 《Journal of Sol-Gel Science and Technology》2011,59(3):488-494
Pb2CrO5 nanoparticles were embedded in an amorphous SiO2 matrix by the sol–gel process. The pH and heat treatment effects were evaluated in terms of structural, microstructural and
optical properties from Pb2CrO5/SiO2 compounds. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy
(EDS), and diffuse reflectance techniques were employed. Kubelka–Munk theory was used to calculate diffuse reflectance spectra
that were compared to the experimental results. Finally, colorimetric coordinates of the Pb2CrO5/SiO2 compounds were shown and discussed. In general, an acid pH initially dissolves Pb2CrO5 nanoparticles and following heat treatment at 600 °C crystallized into PbCrO4 composition with grain size around 6 nm in SiO2 matrix. No Pb2CrO5 solubilization was observed for basic pH. These nanoparticles were incorporated in silica matrix showing a variety of color
ranging from yellow to orange. 相似文献
18.
Phase relations in
the solid state in the FeVO4–Co3V2O8
system, in the whole range of components concentration have been studied.
It was found that the composition of the phase of the howardevansite type
structure, formed in the investigated system, corresponds with the Co2.616Fe4.256V6O24 formula. The phase of the lyonsite type structure
has a homogeneity range with the Co3+1.5xFe4–xV6O24 formula (0.476 formula (0.476<x<1.667).
The melting temperature and the volume of the unit cell of the lyonsite type
structure phase increases together with the rise of cobalt quantity contained
in it. Basing on the results of the DTA and XRD measurements a phase diagram
of the FeVO4–Co3V2O8
system up to the solidus line was constructed. 相似文献
19.
A novel trinuclear NiII cluster, {[Ni(H2L)(EtOH)]2(OAc)2Ni} · 2EtOH [H4L:5,5′-Dihydroxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol], has been synthesized and structurally characterized.
The X-ray crystal structure of the cluster reveals that two acetates coordinate to three nickel ions through Ni–O–C–O–Ni bridges
and four μ-phenoxo oxygen atoms from two [Ni(H2L)] units also coordinate to nickel ions. Around three nickel atoms are all octahedral geometries. 相似文献
20.
P. I. Kirienko T. M. Boichuk S. N. Orlik S. A. Solov’ev 《Theoretical and Experimental Chemistry》2012,47(6):384-389
It is shown that palladium–cobalt oxide–cerium catalyst deposited on cordierite catalyzes the reduction of nitrogen(II) oxide
with carbon monoxide, and cobalt–iron catalysts in simultaneous reduction of NO + N2O with C3-C4 alkanes retained high activity in the presence of water vapor and sulfur dioxide. The Pd-Co3O4/cordierite catalyst exceeds the Pt-Co3O4/codierite catalyst in the conversion of NO and CO in the reaction mixture CO + NO + O2 + H2O + SO2. Modification of the Pd-Co3O4/cordierite with cerium oxide considerably increases its sulfur resistance. 相似文献