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1.
M. J. Guiomar H. M. Lito M. Filomena G. F. C. Camões Arthur K. Covington 《Journal of solution chemistry》1998,27(10):925-933
A new computer program has been developed for the calculation of pH, pOH, hydroxide ion concentration m
OH, species distribution coefficients i, ionic activity coefficients i ionic strength I, buffer capacity , solubility product K
s0, and the two dissociation constants, K
b1 and K
b2, corresponding, respectively, to first and second dissociation steps of Ca(OH)2 in aqueous solution. Previously developed methodology, for the calculation of pH, i, i
I, and parameters of pH buffer solutions, starting from the corresponding acidity constants, has been adapted for the case of aqueous Ca(OH)2 solutions, for which the pertinent stoichiometric relationships are different from those applicable to mixtures of acids and their salts. The results show that, contrary to what is currently assumed, the first dissociation is far from complete. Values are given for the concentrations and activities of species Ca(OH)2(aq), Ca(OH)+(aq), and Ca2+ (aq) in saturated calcium hydroxide solutions at 25°C. 相似文献
2.
Shape apprearance and crystallite characterization of magnesium hydroxide at different hydrothermal tempera-tures have been investigated by SEM, XRD and DSC methods. The grain size, cell parameter and lattice distortion rate of powders under each condition were obtained. The results show that the grains had grown up, especially along the (001) surface as the hydrothermal temperature was raised, accompanying the shrinkage of lattice and the de-scending of distortion rate. These could be relate to the re-crystallization of Mg(OH)2, as well as the thermal dif-fusion of OH- with lower charges, resulting in good dispersion, high thermal decomposition temperature and en-thalpy of Mg(OH)2. Moreover, it is helpful for the increase of the retardant behavior of Mg(OH)2. 相似文献
3.
Chromium(III)isanessentialtraceelement.Inanactiveform.chronlium(III)asacomponentofglucosetolerancefactor(GTF)canimproveinsulinbiologicalactivity.CrsupplementationinhumansandanimalsreducessymptomsofTypeIIdiabetesandhypoglycemia.Forabetterunderstandingofthenatureofbiologicallyactivechromium(ill)complex,manyGTFmodelcomplexeshavebeenstudiedpreviously'.Here,oneGTFmodelcomplexofN,N'-ethylenebis(salicylideneiminato)diaquochromium(ill)chloride,[Cr(salen)(H,O)=]CIwaspreparedandcharacterized.a… 相似文献
4.
Zsakó J. Várhelyi Cs. Marcu Gh. Liptay G. 《Journal of Thermal Analysis and Calorimetry》1999,55(1):311-320
14 mixed Co(III) dioximine chelates of the types [Co(Diox·H)2(amine)2]X (X = Br, I, NO3, ClO4) and H[Co(Diox·H)2(N3)2], respectively (Diox·H2-1,2-cyclohexane dione dioxime (nyoxime), 1,2-cycloheptane dione dioxime (heptoxime) 1,2-cyclooctane dione dioxime (octoxime)
were obtained and their thermal decompositions were studied in an argon atmosphere. After the dehydration of the crystallohydrates,
both types of complexes exhibit 3 decomposition stages. For the [Co(Diox·H)2(amine)2]X type complexes (X = Br, I) the first endothermal stage is the substitution of an amine molecule for the external sphere
anion and this process is followed by two exothermal decomposition stages. With H[Co(Diox·H)2(N3)2] type complexes the first and third processes are relatively slow, but the second process is very fast, corresponding to
a vertical portion of the TG curves. From the TG curves kinetic parameters were derived for 11 processes and the validity
of a non-linear compensation law was observed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
SUN Ling-na WANG Ke-li LUO Sheng-jun GUO Qing-rong HU Chang-wen 《高等学校化学研究》2007,23(5):508-510
β-Co(OH)2 and Mg(OH)2 nanoplates were synthesized via a facile template-free hydrothermal approach.The different conditions of preparation and catalytic properties of the products were studied and discussed.The products were characterized by X-ray diffraction,transmission electron microscopy,scanning electron microscopy,selected area electron diffraction(SAED),and gas chromatograph. 相似文献
6.
1 INTRODUCTION Over the past decades, considerable attention has been devoted to the synthesis, characterization and property studies of Schiff bases and their com- plexes because of their potential and developed appli- cations in the fields of conducting and magnetic ma- terials, dyes, non-linear optics, catalysis, analytical chemistry, biochemical research, agriculture and so on[1~7]. A large number of reports are available in the chemistry and biologic activities of transition metal co… 相似文献
7.
以CuSO4.5H2O和NaOH为原料,采用沉淀法制备得到Cu(OH)2纤维,再进行Cu(OH)2的分解反应.考察了在不同实验条件下温度对Cu(OH)2热分解过程的影响.结果表明:在反应温度20℃,反应终点pH值为12,搅拌速度为1 200 r.min-1,NaOH溶液的滴加速度为50 mL.min-1的反应条件下,得到的样品为纳米Cu(OH)2纤维,其直径为10~30 nm、长度为1~6μm;在固相纳米Cu(OH)2热分解制备CuO过程中CuO粒径随温度的升高而增大,在温度不超过200℃时CuO的粒径约为20 nm左右;在液相中先沉淀后升温时,产物的形貌为球形,CuO粒径随温度的升高而增大,低于80℃可得到纳米级的CuO. 相似文献
8.
C. -W. Chang Y. -C. Chou J. -M. Tseng M. -Y. Liu C. -M. Shu 《Journal of Thermal Analysis and Calorimetry》2009,95(2):639-643
Many concerns over unsafe or unknown properties of multi-walled carbon nanotubes (MWNTs) have been raised. The thermal characteristics
regarding stability would represent potential hazards during the production or utilization stage and could be determined by
calorimetric tests for various thermokinetic parameters. Differential scanning calorimetry (DSC) was employed to evaluate
the thermokinetic parameters for MWNTs at various compositions.
Thermoanalytical curves showed that the average heat of decomposition (ΔH
d) of the MWNTs samples in a manufacturing process was about 31,723 J g−1, by identifying them as an inherently hazardous material. In this study, significant thermal analysis appeared in the presence
of sulfuric acid (H2SO4). From the DSC experiments, the purification process of MWNTs could induce an unexpected reaction in the condition of batch
addition with reactants of H2SO4. The results can be applied for designing emergency relief system and emergency rescue strategies during a perturbed situation
or accident. 相似文献
9.
沉淀转化法制备的Co(OH)2的超级电容特性 总被引:11,自引:0,他引:11
Cobalt hydroxide, often used as an additive in nickel electrode, is rarely studied as active material for su-percapacitors. In this paper, the Co(OH)2 with the particle size less than 20nm by deposition transformation was synthesized. Its single electrode specific capacitance was measured to be 92F·g-1, and the electrode resistance was so low that the initial potential drop when discharging is unobvious even the discharge current increased to 200mA for a 1cm2 electrode. After ten thousand cycles, Co(OH)2 on the electrode changes to Co3O4 gradually, the resistance of the electrode does not increase much, while the specific capacitance increases to 133F·g-1 at 10mA。 相似文献
10.
Debao Wang Caixia Song Zhengshui Hu 《Journal of Dispersion Science and Technology》2013,34(7):1010-1012
Mono-dispersed Mg(OH)2 nanoflakelets have been prepared with the assistant of 4-(p-nitrophenylazo)resorcinol. The samples were characterized using XRD, TEM, and ED. Electron diffraction analysis showed that single crystalline nanoflakelets were obtained in hydrothermal process, and porous Mg(OH)2 nanosheets were prepared at lower temperature. Nitrogen adsorption isotherms show that the surface area of Mg(OH)2 nanosheets is 129 m2/g. Possible growth mechanism of the nanoflakelets is discussed. 相似文献
11.
12.
Shas V. Mattigod Dhanpat Rai Andrew R. Felmy Linfeng Rao 《Journal of solution chemistry》1997,26(4):391-403
The solubility of crystalline Ni(OH)2 was studied in solutions of 0.01M NaC104 with pH ranging from 7 to near 14. Equilibrium was approached both from over-and undersaturation, and the equilibration times
extended from 3 to 90 days. The solubility of Ni(OH)2(c) in the pH range of approximately 7 to 11.3 was effectively modeled by including aqueous Ni2+ and NiOH+ species. Values of the logarithm of the thermodynamic equilibrium constants for the reactions [Ni(OH)2(c) ⇌ Ni2+ + 2OH-] and [Ni2+ + OH- ⇌ Ni(OH)+] were determined to be -16.1±0.1 and 5.65 ± 0.10, respectively. These data, in conjunction with Pitzer ion interaction parameters
given in the literature, were used to model the reported solubilities of Ni(OH)2(c) in chloride, sodium acetate, and potassium chloride solutions. The model predictions for these systems were in excellent
agreement with the experimental data from the literature. 相似文献
13.
采用配位沉淀法制备出了Ni(OH)2样品,经XRD测试为β-Ni(OH)2,TEM测试结果表明其为平均粒径50nm左右的不规则的颗粒。将所制备的纳米Ni(OH)2按8wt%的比例在球镍中混合后制成电极,可使正极的比容量提高11%左右。热分析表明,纳米Ni(OH)2的电化学活性高于球镍的电化学活性。激光拉曼光谱的测试结果说明了8wt%混合后制成的纳米电极确实有较好的放电容量,同时也证实了用拉曼光谱可以表征电极材料的充放电 相似文献
14.
Günther Vogg Lex J.-P. Meyer Christian Miesner Martin S. Brandt Martin Stutzmann 《Monatshefte für Chemie / Chemical Monthly》2001,132(10):1125-1135
Summary. Epitaxial thin films of Ca(Si
1 − x
Ge
x
)2 with 0 < x ≤ 1 are found to react with the moisture of ambient atmosphere to form new Ca-Si-Ge-O-H compounds which were studied by X-ray
diffraction, energy dispersive X-ray analysis, infrared absorption, and thermally induced hydrogen desorption measurements.
Pure CaGe2 forms the polygermyne calcium hydroxide intercalation compound Ca(OH)2(GeH)2 upon exposure to humidity, with a trigonal tr6 crystal lattice with a = 4.00(1) and c = 65.3(1)?. In mixed Ca(Si
1 − x
Ge
x
)2 with smaller Ge content, the group-14 layers are subject to intense oxidation leading to decreased crystallinity. The products
exhibit characteristic colours and intense photoluminescence, the peak luminescence varying from 1.35 eV for the reaction
product of Ca(Si0.3Ge0.7)2 to 2.6 eV for that of Ca(Si0.5Ge0.5)2.
Received March 12, 2001. Accepted (revised) May 2, 2001 相似文献
15.
Thermal decomposition of Bi(SCN)3, Cd(SCN)2, Pb(SCN)2 and Cu(SCN)2 has been studied. The thermal analysis curves and the diffraction patterns of the solid intermediate and final products of the pyrolysis are presented. The gaseous products of the decomposition (SO2 and CO2) were detected and quantitatively determined. Thermal, X-ray and chemical analyses have been used to establish the nature of the reactions occurring at each stage in the decomposition.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
16.
Fe(OH)2悬浮液在EDTA作用下氧气氧化生成δ-FeOOH的机理研究 总被引:1,自引:0,他引:1
At room temperature and in the presence of trace EDTA, the formation of δ-FeOOH was studied by the rapid oxidation of Fe(OH)2 suspension with O2. The structural and morphological changes were characterized by various techniques such as XRD, FTIR and TEM. γ-FeOOH and (δ-FeOOH) formed simutaneously in the early period of oxidation. But as the rate of mass transfer was in equilibrium, trace (γ-FeOOH) vanished gradually. Accordingly, pure phase δ-FeOOH was obtained. At the same time, critical amount ratio K of EDTA to Fe2+ was verified. The experiments show that the reactivity, rate of the oxidizing agent and pH of the initial medium were important factors for the formation of pure phase (δ-FeOOH). Under the auxiliary effect of EDTA, the reactivity of O2 was nearly improved to that of H2O2. And the process of the oxidation that Fe(OH)2 suspension was oxidized by O2 under that condition was discussed. 相似文献
17.
18.
Mei-Li You Ming-Yang Liu Sheng-Hung Wu Jen-Hao Chi Chi-Min Shu 《Journal of Thermal Analysis and Calorimetry》2009,96(3):777-782
Lauroyl peroxide (LPO) is a typical organic peroxide that has caused many thermal runaway reactions and explosions. Differential
scanning calorimetry (DSC) was employed to determine the fundamental thermokinetic parameters that involved exothermic onset
temperature (T0), heat of decomposition (ΔHd), and other safety parameters for loss prevention of runaway reactions and thermal explosions. Frequency factor (A) and activation
energy (Ea) were calculated by Kissinger model, Ozawa equation, and thermal safety software (TSS) series via DSC experimental data.
Liquid thermal explosion (LTE) by TSS was employed to simulate the thermal explosion development for various types of storage
tank. In view of loss prevention, calorimetric application and model analysis to integrate thermal hazard development were
necessary and useful for inherently safer design. 相似文献
19.
M. A. Rodríguez P. Millán R. M. Rojas O. García Martínez 《Journal of Thermal Analysis and Calorimetry》1995,44(2):395-404
The basic salt cobalt(II) hydroxide fluoride was obtained by partial hydrolysis of a 0.2M solution CoF2. Mixed Co(II)·Cu(II) hydroxide fluorides with an isomorphic substitution of Co(II) by Cu(II) ions up to 20% were also prepared. XRD data obtained on these compounds indicate that they are single-phase compounds, their X-ray powder patterns being almost identical to the Co(OH)0.7F1.3 diagram, with Zn(OH)F-type structure. However, their stoichiometries are very close to Co1?xCux(OH)F (0≤x≤0.2). Thermal analysis studies carried out up to 1273 K in still air or under dynamic vacuum conditions show that in air CoO or a mixture of CoO and CuO is formed as final product. In vacuum, at high temperature, with a Ta heating surface, pure α-Co or a mixture of α-Co and Cu is formed at about 973 K. 相似文献
20.
J. Straszko M. Olszak-Humienik J. Możejko 《Journal of Thermal Analysis and Calorimetry》2000,59(3):935-942
Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition
of cobalt sulphate hexahydrate under an air atmosphere.
The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the
thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献