- Stability and reactivity of coordination and inclusion compounds in the reversible processes of thermal dissociation
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The thermoanalytical approach to the study of the kinetic lability of coordination and inclusion compounds in the reversible processes of thermal dissociation is discussed. The secondary crystal structure that existed initially and its transformation into the reaction zone on the surface of the grain are considered. It is pointed out that in any experiment the measured decomposition rate is averaged over all crystal faces. Kinetic data can be interpreted in terms of the transformation mechanism only for a series of isostructural compounds. The author's own experimental data on thermal dissociation processes for coordination and inclusion compounds are presented and considered.
- Logvinenko
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- Effusion Studies of the Decomposition of Zinc Sulfate and Zinc Oxysulfate
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The torsion-effusion method has been used to measure the SO3 decomposition pressure over the crystalline solids ZnSO4 and ZnO*2ZnSO4 in the range of about 800 to 900 K.SO3 is the only detectable vapor species under these conditions.Vapor composition was verified by mass spectrometry and by molecular weights obtained from simultaneous torsion and mass-loss effusion measurements.The vaporization process is kinetically limited in two respects, since SO2 and O2 are the dominant gaseous products at equilibrium and since the SO3 effusion pressures show a pronounced dependence on orifice size. Equilibrium SO3 pressures over both ZnSO4 and ZnO*ZnSO4, derived by extrapolation of steady-state pressures to zero orifice area, are more than a factor of five lower than values calculated from established thermodynamic data, indicating the likelihood that the product solid phases are formed in a finely divided metastable condition.Addition of a few mole percent of Pt powder to ZnO*2ZnO4 led to a dramatic pressure increase and to effusing gas compositions consistent with decomposition to SO2 and O2, while for ZnSO4 the effusing gas was converted to SO2 and O2 but the pressure increase was smaller and not entirely reproducible.The mechanistic implications of these results and correlations with other sulfate studies are discussed.
- Brittain, R. D.,Lau, K. H.,Knittel, D. R.,Hildenbrand, D. L.
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- Crystallization and characterization of the compounds Gly·MSO 4·mH2O (M = Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+; M = 0, 3, 5, 6)
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The equilibrium crystallization of complex compounds of the type Gly·MSO4·5H2O with a structure derived from those of the crystallized double salts MSO4·xH2O, where x = 6, 7 was predicted and proven in the systems Gly-MSO 4-H2O (M = Mg2+, Mn2+, Fe 2+, Co2+, Ni2+ and Zn2+). It was predicted that stable octahedral complexes [M(H2O)6] 2+ and trans-[M(H2O)4(O-gly)2] 2+, as well as [SO4]2- tetrahedra, which were the main building units of the crystallizing Gly·MSO4· 5H2O compounds (triclinic crystal system, space group P - 1), were predominating in these solutions. The vibrational spectra and the thermal behavior of the Gly·MSO4·5H2O compounds (M = Mg2+, Co2+, Zn2+) are in accord with the refined crystal structures. The cobalt compound displays antiferromagnetic behavior whereas the nickel and manganese compounds are ferromagnetic. In the manganese system where MnSO4·H2O (308 K) crystallizes, the only complex compound is the anhydrous Gly·MnSO 4 with a polymeric type structure (trans-[Mn(SO4) 4(O-gly)2]n2-). A new compound Gly·CoSO 4·3H2O was found in the cobalt system under unstable equilibrium conditions. Gly·CoSO4·3H 2O was proven to consist of two types of octahedra, trans-[Co(H 2O)4(O-gly)2]2+ and trans-[Co(H 2O)2(SO4)2(O-gly)2] 2-, forming a chain structure (monoclinic crystal system, space group P21/c).
- Tepavitcharova,Rabadjieva,Havlí?ek,Němec,Vojtí?ek,Plocek,Koleva
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- Spectral and thermal studies on new hydrazinium metal sulfite dihydrates
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Some new hydrazinium transition metal sulfite dihydrate complexes of the formula (N2H5)2M(SO3) 2(H2O)2 where M=Fe, Co, Ni, Cu and Zn have been prepared and characterized by hydra
- Vikram,Shanthakumar,Ragul,Sivasankar
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- Oxidation of a ZnS nanobelt into a ZnO nanotwin belt or double single-crystalline ZnO nanobelts
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Single-crystalline wurtzite ZnS nanobelts are synthesized by the vapor phase transport (VPT) process. When oxidized, a single-crystalline ZnS nanobelt turns into a ZnO nanotwin belt containing two twinning parts with a sharp and clear edge, which is a (0001) twinning plane parallel to and running through the length direction. The two twinning parts in a ZnO nanotwin belt have the same crystalline direction, [0001], along their width, and the [011?0] and [112?0] crystalline directions along the length direction. On some ZnO nanobelts, nanovoids appear along the twinning planes and when those nanovoids connect with each other, one original ZnS nanobelt can divide into two single-crystalline ZnO nanobelts with quite clear edges. Published by Elsevier Ltd.
- Li, Yujie,You, Liping,Duan, Ran,Shi, Pengbo,Qin, Guogang
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- AQUEOUS COMPOSITION AND METHOD OF PRODUCING CHLORINE DIOXIDE USING AQUEOUS COMPOSITION
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An aqueous composition includes an activator, a chlorite ion source, and water. The aqueous composition is alkaline. The aqueous composition produces chlorine dioxide upon contact with an acid. A method of producing chlorine dioxide includes contacting the aqueous composition with an acid.
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- Interpenetrated and Catenated Zinc Thiosulfates Frameworks with dia and qtz Nets: Synthesis, Structure, and Properties
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Reactions between Zn(NO3)2·6H2O, Na2S2O3, 4,4′-bipyridine (bpy), 1,2-bis(4-pyridyl)ethene (bpe), 1,2-bis(4-pyridyl)ethane (bpa), and 1,3-bis(4-pyridyl)propane (bpp) under solvothermal conditions resulted in four new zinc thiosulfate hybrid compounds. Compound I has four-membered zinc thiosulfate rings connected by the ligand, 1,3-bis(4-pyridyl)propane (bpp) forming a two-dimensional structure. Compounds II-IV have one-dimensional zinc thiosulfate chains connected by the ligands, bpy (II), bpe (III), and bpa (IV) giving rise to three-dimensional structures. All the four-structures exhibit 3-fold interpenetration. Proton conductivity studies indicate reasonable proton mobility at 34 °C and at 98% relative humidity. The compounds also exhibit Lewis acid character and good photocatalytic activity for the decomposition of cationic dyes.
- Karthik, Rajendran,Natarajan, Srinivasan
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p. 2239 - 2248
(2016/05/09)
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- METHOD OF PROMOTING WOUND HEALING
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A method of establishing a therapeutic window of wound fluid nitric oxide (WFNO) in the wound of a mammal, the method including: obtaining a wound fluid sample from a mammal; analyzing the WFNO level; determining whether the WFNO is at or below a lower threshold level, or is at or above an upper threshold level; wherein the lower threshold level and upper threshold level define the therapeutic window of WFNO; and treating the mammal with a substance that alters the WFNO level such that the therapeutic window of WFNO in the wound is established.
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Page/Page column
(2015/03/16)
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- Local investigation of hyperfine interactions in pure and Co-doped ZnO
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In the present work bulk samples of pure as well as Co-doped ZnO with different concentrations were prepared by sol-gel method from highly pure metallic Zn (99.9999%) and Co (99.9999%). The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray microanalysis (EDS) and perturbed gamma-gamma angular correlation (PAC) spectroscopy. Carrier-free 111In nuclei were introduced during preparation of the samples and used as probe nuclei at Zn sites for PAC measurements. PAC results show that both pure and Zn1 - x Cox O (x ≤ 0.15) samples have the same electric quadrupole frequency when Co-doped samples are annealed in air, argon or nitrogen atmosphere at 1173 K. SEM and EDS results showed that Co-doped samples are homogeneous without any secondary Co phases. These observations indicate that Co ions are substituted for Zn ions and have a similar electronic structure of Zn ions. A weak local magnetism was observed at temperatures below about 300 K for Co concentration of 10% when sample was annealed in Nitrogen.
- Mercurio,Carbonari,Cordeiro,Saxena,D'Agostino
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p. 1195 - 1197
(2010/07/04)
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- Polytypism, disorder, and anion exchange properties of divalent ion (Zn, Co) containing bayerite-derived layered double hydroxides
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Incorporation of Zn2+ into bayerite results in the formation of a cation-ordered layered double hydroxide (LDH) of monoclinic symmetry in which about half the vacancies of Al(OH)3 are occupied by Zn2+ giving rise to positi
- Britto, Sylvia,Kamath, P. Vishnu
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p. 11370 - 11377
(2011/02/27)
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- Thermal decomposition kinetics of some aniline complexes of zinc group metals
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The kinetics and mechanism of thermal decomposition of aniline complexes of zinc group metals have been studied using non-isothermal thermogravimetry. Kinetic parameters have been calculated for each of the decomposition stages using the Coats-Redfern equation. The mechanisms of the reactions have also been found out, and the rate controlling processes are found to be either random nucleation with the formation of one nucleus on each particle (Mampel equation) or phase boundary reaction with cylindrical symmetry or spherical symmetry.
- Sikha,Indrasenan
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p. 1393 - 1402
(2007/10/03)
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- Thermal degradation kinetics of Co(II), Ni(II), and Zn(II) hydrazinesulfinates in air, oxygen and nitrogen atmospheres
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Cobalt, nickel and zinc hydrazinesulfinate complexes of the molecular formula M(N2H3SOO)2 where M=Co, Ni and Zn, respectively, have been prepared and characterized by analytical and spectral techniques. The thermal decomposition of these complexes have been studied in three different atmospheres, viz. static air, oxygen and nitrogen. In static air, cobalt and zinc complexes give respective metal sulfites while the nickel complex yield nickel sulfate. In oxygen atmosphere, cobalt complex gives a mixture of oxide and sulfate while the nickel and zinc complexes yield the respective metal oxide. In the nitrogen atmosphere, the complexes decompose to yield a mixture of metal sulfide and metal sulfite in the case of cobalt and nickel while zinc complex gives ZnO. The above complexes have also been subjected to sudden heating at high temperatures ca. 500 °C, i.e. combustion, which resulted in the formation of metal oxide in the case of cobalt while the nickel complex gives nickel sulfide as the final product. However, the zinc complex gives mixture of zinc oxide and zinc sulfate. The kinetic parameters were evaluated for these complexes using Coats-Redfern equation. The parameters have been studied on the basis of TG-data and in most of the cases, the decomposition is found to follow first order kinetics.
- Sivasankar,Ragunath
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p. 237 - 247
(2008/10/08)
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- Some electrochemical studies on cementation of copper onto zinc from sulfate bath
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Cementation of copper onto zinc from a sulfate bath was investigated through polarization measurements of both the anodic and cathodic half-cell reactions as well as practical cementation studies. Individual half-cell reactions, when isolated in a dual cell, followed a first-order rate with respect to [Cu2+] (cathodic) without any excess zinc dissolution (at the anode) via a hydrogen reaction. In the presence of a zinc surface and Cu2+ in a single bath, excess zinc dissolved via hydrogen reduction and the first-order copper cementation rate was enhanced after an initial slow step. The enhanced rate is associated with a decrease of the mixed potential, Em. Deposited copper catalyzes, excess zinc dissolution via hydrogen reduction reaction.
- Mishra,Paramguru
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p. 3302 - 3310
(2008/10/08)
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- Molten potassium pyrosulphate: Reactions of oxides of ten main-group elements
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The reactions of MgO, CaO, SrO, BaO, ZnO, CdO, SnO, PbO, Pb3O4 and As2O3 with K2S2O7 were investigated using TG and DTA methods of thermal analysis. The exothermic peaks diagnost
- Salem,Tariq
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p. 123 - 125
(2008/10/09)
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- Differential thermal study of the interactions between sulphates, oxides and ferrites
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The solid state interactions in the ZnSO4.7H2O-MeO (Me = Cd, Pb, Ca, Mg) and CuSO4.5H2O-MeO (Me = Zn, Cd, Pb, Ca, Mg) systems, sulphate-ferrite systems, double sulphate systems and triple system FeSO4
- Boyanov
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p. 109 - 115
(2008/10/09)
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- Etude thermodynamique et cinetique de la lixiviation du sulfure de zinc en solution aqueuse d'acide sulfurique
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The dissolution of a synthetic zinc sulfide in aqueous sulfuric acid has been investigated without and with oxygen in an autoclave up to 200 deg C.In absence of oxygen, hydrogen sulfide is produced and the following chemical equilibrium takes place: Zn(S) + H2SO4 Zn2+ + SO4-- + H2S(aq) The Henry coefficient of H2S has been experimentally determined.The activity coefficients for sulfuric acid and zinc sulfate in presence of each other have been computed by Pitzer's model.The equilibrium constant was calculated up to 200 deg C and reaction enthalpies were deduced.In the presence of oxygen, hydrogen sulfide is oxidized; elemental sulfur and sulfuric acid are consequently produced.The kinetics of reaction was determined in relation to zinc sulfide mass, sulfuric acid concentration, oxygen pressure and temperature.The activation energies are 93.2 kJ/mol below 160 deg C and 171.1 kJ/mol between 160 and 200 deg C.The dissolution of zinc sulfide is inhibited by the produced hydrogen sulfide.The reaction is accelerated by activated carbon which adsorbs H2S.The reaction rate is controlled mainly by the oxidation of hydrogen sulfide by oxygen under 160 deg C and by the oxidation reactions of H2S by oxygen and sulfuric acid above 160 deg C.The resulting elemental sulfur covers in part the grains surface and is partly oxidized to sulfuric acid.
- Gely, Roger,Corriou, Jean-Pierre,Viers, Philippe
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p. 405 - 412
(2007/10/02)
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- Aspects of the Inorganic Chemistry of Rubber Vulcanisation. Part 4. Dialkyl- and Diaryl-dithiophosphate and -dithiophosphinate Complexes of Zinc: Phosphorus-31 Nuclear Magnetic Resonance Spectral Studies and Structures of 4>2P(OC6H4Me-p)2)3> and 4>2PPh2
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The complexes 4>2P(OC6H4Me-p)2)3> and 4>2PPh2)3> have been prepared by treatment of 2PR2)2> with (NR'4>2PR2> (R=OC6H4Me-p or Ph, R'=Me or Et).Preparation of 2(S2P(OPri)2)>- and 2PR2)2(S2CNMe2)>- (R=OC6H4Me-p or Ph) is also described.From reactions of 2P(OR)2)2> (R=Pri or C6H4Me-p) with H2O2 or ButO(OH), zinc phosphates and ZnSO4 have been obtained, and 2P(OPh)2)2> and 2P(OPh)2)3>- react with ROH (R=Et or Pri) in solution to give amongst other products 2P(OR)2)2> and 2P(OR)2>- with loss of phenol.The 31P n.m.r. spectra of a series of dialkyl- and diaryl-dithiophosphate and -phosphinate complexes have been recorded and used to establish rapid exchange within the equilibrium 2P(OR)2)3>- 2P(OR)2)2> + 2P(OR)2>-.The structures of the title compounds have been determined crystallographically: 4>2P(OC6H4Me-p)2)3> is monoclinic with a=29.311(9), b=11.032(3), c=17.515(5) Angstroem, β=106.83(2) deg, space group P21/a, Z=4, and 2490 reflections give R 0.0532; 4>2PPh2)3> is monoclinic with a=11.160(6), b=9.962(5), c=43.11(3) Angstroem, β=104.73(5) deg, space group P21/c, Z=4, and 3304 reflections give R 0.0411.Both have slightly distorted tetrahedral geometries in which one S2PR2 ligand is bidentate, and the other two are unidentate.
- McCleverty, Jon A.,Kowalski, Rick S. Z.,Bailey, Neil A.,Mulvaney, Robert,O'Cleirigh, Donal A.
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p. 627 - 634
(2007/10/02)
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