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1.
The anodic oxidation of highly oriented pyrolytic graphite in H2SO4–CH3COOH electrolytes in a galvanostatic mode (I = 1.5 mA) is studied as a function of electrolyte composition. The concentration ranges for the formation of stage I–V graphite intercalation compounds (GICs) are determined. The concentration threshold for intercalation is 1 wt % H2SO4. There are three distinct concentration ranges differing in the shape of the charging curve E(Q), which depends primarily on the content of H2SO4 (active intercalant). The potentials of formation of stage I–III GICs in H2SO4–CH3COOH electrolytes are found to be higher than those for graphite bisulfate, which points to an increase in the potential barrier for intercalation and is obviously associated with the intercalation of acetic acid into the graphite host. The specifics of the charging curves obtained in 60–80% H2SO4, together with gravimetry and chemical analysis data, indicate the formation of ternary GICs with sulfuric and acetic acids. In this composition range, stage I* and II* cointercalation compounds are obtained, with an intercalate layer thickness d
i = 7.94 Å. The composition of the ternary GICs is shown to depend on the relative amounts of the acids in the electrolyte. A mechanism of the formation of graphite cointercalation compounds is proposed. In solutions containing less than 40 wt % H2SO4, only graphite bisulfate is formed. 相似文献
2.
3.
The reactions between highly oriented pyrolytic graphite and HNO3–R (R = H2O, CH3COOH, H3PO4, H2SO4) solutions were studied by x-ray diffraction and potentiometry. The results demonstrate that the nature of component R has a crucial effect on the intercalation process and phase composition of the reaction products. The ability to form ternary graphite intercalation compounds (GICs) depends on the acidity of R. It is shown that CH3COOH, a weak protic Brönsted acid (pK
= 4.76), does not form cointercalation compounds when graphite is treated chemically or electrochemically in HNO3–CH3COOH solutions. H3PO4, a weak Brönsted acid (pK
= 2.12) forms ternary intercalation compounds. Stage II–IV ternary GICs with HNO3 and H3PO4 (d
i = 8.05 Å) were for the first time synthesized and investigated. H2SO4, a strong Brönsted acid (pK
= –2.8), forms stage I cointercalation compounds (I
c = 8.02 Å), independent of the HNO3 content (5–95 wt %) of the oxidizing mixture. The potential of the HNO3–H2SO4 solutions was found to be E
Ag/AgCl = 1.39 V, independent of the HNO3 : H2SO4 ratio. The main relationships in the ternary systems were shown to be similar to those for the formation of binary GICs with acids. There is a perfect correlation between the redox potential of the HNO3–R (R = H2O, CH3COOH, H3PO4, H2SO4) solutions and the stage index of the resulting GIC. The concentration ranges of GIC formation in nonaqueous HNO3 solutions were extended substantially. The behavior of stage I–IV graphite nitrates in different solvents (H2O, CH3COOH, H3PO4, and H2SO4) was studied. Based on the experimental results, mechanisms of the processes in the systems studied were proposed. 相似文献
4.
V. V. Avdeev N. E. Sorokina N. V. Maksimova I. Yu. Martynov A. V. Sezemin 《Inorganic Materials》2001,37(4):366-371
The reactions of stage II–IV graphite nitrates with concentrated H2SO4, H3PO4, and CH3COOH were studied at graphite : acid weight ratios from 3 : 1 to 1 : 1. The results demonstrate that the reactions in question follow different paths. In the graphite nitrate–H2SO4system, the reaction decreases the stage index and yields a ternary graphite intercalation compound. The contents of intercalated HNO3and H2SO4are controlled by the amount of H2SO4and the stage index of the parent graphite nitrate. The reaction between graphite nitrate and H3PO4leads to partial replacement of HNO3by H3PO4, increasing the identity period without changes in the stage index. The results for the graphite nitrate–CH3COOH system provide no direct evidence for the formation of an intercalation compound with HNO3and CH3COOH. It is shown that varying the nature and amount of the second intercalate species opens up possibilities for preparing oxidized graphite with controlled physicochemical properties. 相似文献
5.
Poly(anilino sulphamicphosphazenes) such as [NP(HNC6H5)2–x
(HNC6H4SO3H)
x
]
n
for polymer (I) x=0.3 and for polymer (II) x=0.8 were prepared by the reaction of poly(anilinophosphazene) [NP(HNC6H5)2]
n
and sulphonic chloride HSO3Cl in tetrachloroethane solvent several timeS. Also, H protons in the polymer (I) and (II) were prepared from lithum hydroxide in aqueous solution. It was found, by chemical analysis, that the product prepared with (I) and (II) had compositions such as [NP(HNC6H5)1.7 (HNC6H4SO3H)0.1(HNC6H4SO3Li)0.2]
n
(III) and [NP(HNC6H5)1.2(HN-C6H4SO3Li)0.8]
n
(IV). Also, the resistivity of products (III) and (IV) were determined and found to be 3.3×107 and 1.5×107 cm–1, respectively. 相似文献
6.
P.P. Lopes B.J.M. Leite Ferreira N.A.F. Almeida M.C. Fredel M.H.V. Fernandes R.N. Correia 《Materials science & engineering. C, Materials for biological applications》2008,28(4):572-577
The nature of the orthopaedic implant surface affects the interaction with cells and subsequent bone formation. The bone/cement interface in cement-held prostheses is considered to be the main cause of fracture leading to implant revision. It is thought that the introduction of a bioactive phase, such as bioglass, in the cement may permit a more stable interface by encouraging direct bone apposition rather then encapsulation of the implant by fibrous tissue. In this work new poly(methylmethacrylate) (PMMA) based composites filled with 0, 30, 40 and 50 (wt.%) of a Ca3(PO4)2–SiO2–MgO glass, were processed. The prepared composites consist of a poly(methylmethacrylate)–co–(ethylhexylacrylate) (PMMA–co–EHA) matrix filled with a glass (G7), with nominal composition 33.26CaO, 28.07P2O5, 23.03SiO2, 15.64MgO (wt.%). The in vitro bioactivity of the composites was assessed by determining the changes in surface morphology and composition, by X-ray diffraction (XRD) and scanning electron microscopy coupled with X-ray energy dispersive spectroscopy (SEM-EDS), after soaking in a simulated body fluid (SBF) for periods of up to 21 days at 37 °C. Inductively coupled plasma (ICP) was used to assess the evolution of ionic concentrations in the SBF solution. The results obtained confirmed the growth of a hydroxyapatite (HA)-like layer on the surface of the prepared composites. As expected, HA layer formation was faster for composites prepared with higher glass content. 相似文献
7.
L. B. Serezhkina A. V. Vologzhanina M. O. Karasev V. N. Serezhkin 《Radiochemistry》2011,53(2):142-145
The compound Cs3[UO2(CH3COO)3]2(NCS)·H2O (I) was synthesized and studied by IR spectroscopy and single crystal X-ray diffraction. Compound I crystallizes in the monoclinic system with the following unit cell parameters: a = 7.8286(9), b = 19.892(2), c = 20.050(2) Å, β = 94.527(2)°, space group P21/c, Z = 4, R = 0.0387. The uranium-containing structural units in crystals of I are mononuclear complexes [UO2(CH3COO)3]? belonging to crystal-chemical group AB 3 01 (A = UO 2 2+ , B01 = CH3COO?) of uranyl complexes. 相似文献
8.
《Materials Science and Engineering: B》2001,79(1):31-44
The first principles calculations for K3H(SO4)2 (KHS) system are performed in order to determine its stable structure in the presence of the hydrogen or the deuterium in its hydrogen bond, and to discuss the origin of the large isotope effect in the KHS system. As a result, a reasonable value of the antiferroelectric interaction energy is obtained. It is also found that the position of the hydrogen is closer to the center of the hydrogen bond than that of the deuterium, based on the calculated results of the proton-position dependence of the oxygen–oxygen distance and on the experimental fact that the oxygen-oxygen distance in K3D(SO4)2 (DKHS) is larger than that in KHS. 相似文献
9.
Y. Moritomo Y. Tokura N. Nagaosa T. Suzuki K. Kumagai 《Journal of Low Temperature Physics》1995,99(1-2):55-70
Dielectric and thermodynamic properties have been investigated for isotopically mixed crystals of K3D1–x Hx(SO4)2, which are composed of structurally isolated dimeric units SO
4
–
... H-SO
4
–
. The critical temperature Tc for the antiferroelectric phase transition decreases with proton concentration (x) and eventually the phase transition vanishes at xc 0.66 ± 0.04. The x-dependent behavior of Tc, the dielectric constant (T) and the specific heat C(T) are well accounted for by the mean-field theory for the transverse Ising model, indicating an important role of the proton tunneling on the phase transition and related properties. These features are compared with conventional hydrogen-bonded dielectrics with infinite networks of the hydrogen bonds. 相似文献
10.
The structure of NH4[(NpO2)3(C2H5COO)4(H2O)]·3H2O was studied by single crystal X-ray diffraction. The single crystals were prepared by hydrothermal synthesis. In the structure, there are three crystallographically independent Np atoms with different equatorial surrounding. All of them have CN 7; the coordination polyhedron is a distorted pentagonal bipyramid. Each NpO 2 + cation is bonded to four other cations, acting simultaneously as a bidentate ligand and a coordination center for two other dioxocations. The cation-cation interactions result in formation of trigonal-hexagonal cationic networks. 相似文献
11.
Shuhei Uchiyama Toshihiro Isobe Sachiko Matsushita Kiyotaka Nakajima Michikazu Hara Akira Nakajima 《Journal of Materials Science》2012,47(1):341-349
Porous ZrO2–SiO2 composite sphere particles were prepared by impregnating precursor solutions into organic monolith particles, with subsequent
calcination in air. The porous spheres possessed uniformly sized pores of around 10 nm. Addition of SiO2–ZrO2 decreased the ZrO2 crystallinity and increased the specific surface area. The acid amount on the surface of the composite spheres was increased
by treatment with H2SO4. The acid strength and its amount, including the Lewis/Br?nsted acid ratio, depended on the SiO2/ZrO2 ratio and the H2SO4 concentration. The powder treated under an optimum condition exhibited higher solid acidity than the reference solid acid
catalyst. The prepared porous SO4
2−/ZrO2–SiO2 spheres showed higher saccharization activity than the reference solid acid catalyst did. 相似文献
12.
13.
The aim of this study was to synthesize materials of α-tricalcium phosphate doped with small amounts of dicalcium silicate, by solid state reaction, at high temperature and slow cooling to room temperature. The obtained materials were characterized by X-ray diffraction, Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy, showing that there is a region between 0.5 and 4.0 wt.% of dicalcium silicate where solid solution α-tricalcium phosphate (α-TCPss) is stable to room temperature. 相似文献
14.
The heat capacity of dimethylammoniumgallium sulfate crystals was measured using adiabatic calorimetry in the range 80–300
K before and after gamma irradiation with doses of 107 and 108 R. Heat-capacity anomalies were revealed around the ferroelastic-ferroelectric (135 K) and ferroelectric-paraelectric (119
K) phase transitions. Gamma irradiation was found to reduce the temperature stability range of the ferroelectric phase. 相似文献
15.
A. U. Sheleg K. V. Iodkovskaya N. F. Kurilovich P. A. Pupkevich 《Inorganic Materials》2001,37(2):189-193
The effect of gamma irradiation on the dielectric permittivity and loss tangent of (CH3)2NH2Ga(SO4)2 · 6H2O crystals was studied near the ferroelectric transition at different frequencies. Irradiation was found to sharply reduce and tan
at gamma doses below 5 × 107 R. At higher doses, and tan
level off. With increasing gamma dose, the ferroelectric transition shifts to lower temperatures, irrespective of frequency. 相似文献
16.
Safronova T. V. Belokozenko M. A. Yahyoev Sh. O. Shatalova T. B. Kazakova G. K. Peranidze K. Kh. Toshev O. U. Khasanova S. S. 《Inorganic Materials》2021,57(8):867-873
Inorganic Materials - Ceramics consisting of anhydrous calcium sulfate, CaSO4, after firing in the range 800–1000°C have been prepared from calcium sulfate dihydrate (CaSO4?2H2O)... 相似文献
17.
18.
Experimental data are presented on (Mo,W)5Si3 and (Mo,W)Si2 solid solutions and are analyzed using the known phase diagrams of the binary systems Mo–Si and W–Si. It is shown that, with increasing tungsten content, the melting temperature of the (Mo,W)5Si3–(Mo,W)Si2 eutectic rises. Surprisingly, the alloys with W : Mo atomic ratios close to unity are found to contain, along with the silicide solid solutions, molybdenum disilicide almost free of tungsten. The mean room-temperature hardness of the eutectic alloys varies nonmonotonically with tungsten content and shows maxima at 33 and 75 at. % W. The surface texture is found to have a significant effect on the rate of high-temperature gas corrosion. The possibility of compositional control (variations in the W : Mo and (Mo,W)5Si3 : (Mo,W)Si2 ratios) over the thermal expansion of the alloys is analyzed. Data are presented on the temperature-dependent resistivity of SiC-matrix composites. 相似文献
19.
《晶体工程》1999,2(4):251-264
The influence of concentration of water and metal salt in the reaction between Cd(NO3)2·4H2O and 4,4′–bipyridine in MeOH has been studied and three compounds namely, T-shaped [Cd(bpy)1.5(NO3)2]·3H2O, 1 square grid [Cd(bpy)2(H2O)2](NO3)2 4H2O, 2 and one dimensional linear polymer, [Cd(bpy)(H2O)2(NO3)2], 3 were isolated quantitatively in this process. Compound 1 forms in MeOH at high dilution of the metal salt (5.0 mg/mL or less) and for the metal-to-ligand ratio 1:(1.5–2.0). Compound 2 forms exclusively in the concentration range, 17–33% for water in MeOH by volume and 12–28 mg/mL for the metal salt of the solution. Outside these limits, mixtures of 2 and 3 were isolated. For 1:1 ratio of metal salt to bpy, the linear polymer, 3 was obtained in major quantity and its formation was found to be independent of concentration of water or the metal salt. Compounds 1 and 2 have been characterized by X-ray crystallography. On heating all the compounds decompose through a common intermediate [Cd(bpy)(NO3)2] and finally to CdO as monitored by TG. 相似文献
20.
Bioactivity and magnetic properties were investigated in glass and glass ceramics based on the SiO2–Na2O–Fe2O3–CaO–P2O5–B2O3 system to find their suitability as thermoseed for hyperthermia treatment of cancer. The effect of change in compositions on bioactivity was examined in simulated body fluids. The glass ceramic samples exhibit Na3CaSi3O8 and Na3-XFeXPO4 phases. After dipping the glass ceramic samples in simulated body fluids silica hydrogel first forms, followed by an amorphous calcium phosphate layer. Magnetic and microwave resonance experiments further demonstrate the potential of these glass ceramics for possible use in hyperthermia. 相似文献