共查询到20条相似文献,搜索用时 12 毫秒
1.
Xinqiang Wang Dong Xu Weiliang Liu Ji Huang Mengkai Lü Hau Ping Chan Pak Lim Chu 《Materials Research Bulletin》2004,39(10):1407-1416
The crystal density and Mohs hardness of zinc cadmium thiocyanate (ZCTC), ZnCd(SCN)4 have been measured at room temperature. The specific heat of the crystal is 699.5 J mol−1 K−1 at 300 K. The thermal expansion coefficient (TEC) along the a and c axes, respectively, is interpreted on the basis of crystal structure. The thermal decomposition process is characterized by thermogravimetry analysis and differential scanning calorimetry (TGA/DSC). The intermediates and final products of the thermal decomposition were identified by X-ray powder diffraction at room temperature. The high-temperature effect in air on the optical transmission of the crystal was also studied. 相似文献
2.
Yinghua Hu 《Materials Research Bulletin》2008,43(10):2703-2708
The thermal analysis of Fe8(OOH)16Cl1.3 (Akaganeite-M) nanospindles prepared by the hydrolysis of FeCl3 solutions are determined by thermogravimetric analyses and differential scanning calorimetry (TG/DSC), in conjunction with field-emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD). Different products are formed after Fe8(OOH)16Cl1.3 nanospindles are calcined at different temperatures for 30 min in N2 atmosphere: Fe1.833(OH)0.5O2.5 and magnetite obtained at 250 °C; pure magnetite (Fe3O4) obtained at 630 °C; and magnetite containing some iron nitrides (Fe2N and Fe4N) obtained at 800 °C. The calcination of Fe8(OOH)16Cl1.3 provides a new method to prepare pure magnetite. 相似文献
3.
L. Guelmami 《Materials Research Bulletin》2007,42(3):446-455
Chemical preparation, X-ray characterization, IR spectroscopy and thermal analysis of a new cyclotriphosphate: (C7H10NO)3P3O9·4H2O abbreviated as OACTP, are reported. This mixed organo-mineral compound crystallizes in the monoclinic system with P21/n space group, the unit cell dimensions are: a = 6.605(3) Å, b = 26.166(3) Å, c = 18.671(8) Å, β = 91.95(3)°, Z = 4 and V = 3255(2) Å3. The structure was solved using a direct method and refined to a reliability R-factor of 0.043 using 3931 independent reflections (I > 2σI). Atomic arrangement exhibits infinite (P3O9·2H2O)n3n− chains connected by organic cations. The thermal behavior and the IR spectroscopic studies of this new compound are discussed. 相似文献
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5.
The title compound, (N4C6H21)·(Co(H2PO4)(HPO4)2), was prepared hydrothermally (473 K, 10 days, autogenous pressure), in the presence of the tris(2-aminoethyl)amine as organic template. Its structure is built up from a network of four membered-rings, formed by the vertex linkages between [CoO4] and [H2PO4] tetrahedra with [HPO4] moieties hanging from the Co center. Hydrogen bonds involving the cobalt phosphate units and the triply protonated amine molecule, contribute to the stability of the structure. The IR spectrum shows bands characteristic of the (N4C6H21)3+ cations and the (H2PO4)− and (HPO4)2− phosphate anions. The UV-Visible-NIR spectrum confirms the tetrahedral coordination of Co2+ ions. The TGA analysis indicates that the dehydration of (N4C6H21)·(Co(H2PO4)(HPO4)2) occurs in one step. Magnetic measurements from 4.5 to 305 K show a weak antiferromagnetic character of this compound. 相似文献
6.
A survey of the subsolidus phase equilibria in the system Li2O-Nd2O3-Fe2O3 was made at subsolidus temperatures in the range 1000-1050 °C. A ternary phase was identified. The phase is centered on Li5Nd4FeO10, with a cubic lattice a = 11.9494 Å. The compound melts incongruently at 1105 °C. The magnetic susceptibility was measured in the temperature range 4-300 K. The compound is paramagnetic in the temperature range 150-300 K and follows the Curie-Weiss law. At about TN = 10 K, a long-range magnetic ordering is observed. 相似文献
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Ya-Wen Zhang 《Materials Research Bulletin》2004,39(11):1763-1777
By the citrate gel method, (ZrO2)0.85(REO1.5)0.15 (RE = Y, Sc) solid solutions in pure cubic fluorite structure were prepared at relatively low calcination temperatures. The existence of the strong coordination interaction between the COO− groups of the ligands and metal ions could effectively prevent the segregation of metal ions during the gel formation. Upon heat treatment within 110-500 °C, the gel decomposed by multi-steps, with the formation of well-defined intermediate decomposition products, while, the bonding nature between COO− groups and metal ions changed with temperature: unidentate (110-250 °C) → bridging (300-350 °C) → ionic (400-500 °C). The oxide powder resulted from the calcination of the gel at 800 °C is an assembly of mesoporous nanoparticles with uniform sizes, but agglomerated in lumps. It was confirmed that the chemical homogeneity, nanoparticle size uniformity and crystallinity, sinterability and electrical conductivity of (ZrO2)0.85(REO1.5)0.15 can be remarkably improved by avoiding the phase separation (solid/liquid) phenomenon during the preparation of the gels. 相似文献
9.
Crystals of 2-amino-4-methylpyridinium dihydrogenmonoarsenate (C6H9N2)H2AsO4 and 2-amino-4-methylpyridinium dihydrogenmonophosphate (C6H9N2)H2PO4 have been prepared and grown at room temperature. These materials are isotypic with the following unit cell dimensions (C6H9N2)H2AsO4: a = 12.4415(5) Å, b = 6.8224(3) Å, c = 11.3524(5) Å, Z = 4, V = 963.60(6) Å3; (C6H9N2)H2PO4: a = 12.4410(9) Å, b = 6.7165(3) Å, c = 11.3417(5) Å, Z = 4, V = 925.09(10) Å3. The common space group is Pnma. The structure of these compounds has been determined by X-ray data collection on single crystals of (C6H9N2)H2AsO4 and (C6H9N2)H2PO4. Due to the strong hydrogen-bond network connecting the H2XO4 groups, the anionic arrangement must be described as a linear organization. The chains composed by the macroanion spread along the b-direction, approximately centered by x = 0 and 1/2. All atoms of the structure, except one oxygen atom, are located in the mirror planes situated at y = 1/4 and 3/4, imparting an internal mirror symmetry to the anionic and the cationic entities. The linear macroanions are crossed by organic cations lying in mirrors perpendicular to the b-direction; this atomic arrangement is then described by a three-dimensional network of hydrogen bonds, built up by two types, O–HO bonds inside the chains and N–HO bonds linking adjacent chains. The thermal properties of both compounds are investigated as well as the IR properties supported by group theoretical analyses. 相似文献
10.
Ranko P BontchevAllan J Jacobson 《Materials Research Bulletin》2002,37(12):1997-2005
A high yield hydrothermal synthesis of the open-framework cobalt borophosphate (C4N2H12)Co[B2P3O12(OH)], has been developed. The compound was characterized by single crystal X-ray diffraction methods, thermogravimetric analysis, vibrational (IR and Raman) spectroscopy and magnetic measurements. In the structure Co(II)O6 octahedra, BO4 and PO4 tetrahedra form nine-member rings which in turn are linked to form CoBPO layers parallel to the bc plane. The layers are joined together by another set of PO4 tetrahedra and the (piperazinium)2+ cations occupy the channels running along [1 0 0]. The structure is compared with that of (C2N2H10)Co[B2P3O12(OH)]. 相似文献
11.
Hydromagnesite is a basic magnesium carbonate that undergoes an endothermic decomposition with water and carbon dioxide release in the temperature range of 200-550 °C. Due to this thermal behaviour it has been studied as flame retardant filler for polymers in cable applications. For this purpose the particle size distribution should be optimized, as it is in most cases responsible for decrease in final composite mechanical properties. This work describes the variations found in the thermal behaviour of hydromagnesite associated with the process of particle size reduction. Air jet micronization was compared with mechanical milling. Thermogravimetry and differential scanning calorimetry were used to study thermal decomposition. FTIR spectroscopy and XRD analysis of the solid residue after heating were used to follow structural changes. Decomposition behaviour of synthetic hydromagnesite was shown to be dependent of the applied particle size reduction process. A remarkable increase in the decomposition rate was observed for the milled sample, which was attributed to the introduction of defects in the crystalline structure during the mechanical milling. Therefore, it was concluded that the mechanical milling process may affect the thermal decomposition of hydromagnesite and therefore its characteristics as flame retardant. 相似文献
12.
Chemical preparation, crystallographic characterization, thermal behavior and IR studies are given for two new cyclotriphosphates SrTlP3O9·3H2O and SrTlP3O9. SrTlP3O9·3H2O is orthorhombic, space group Pnma, with the following unit-cell dimensions: a=9.147(7) Å, b=8.180(7) Å, c=15.458(2) Å and Z=4. The total dehydration of SrTlP3O9·3H2O leads between 300 and 650°C to its anhydrous form SrTlP3O9. SrTlP3O9 is monoclinic, space group P21/m or P21, with the following unit-cell dimensions: a=14.544(2) Å, b=8.639(1) Å, c=7.727(1) Å, β=102.05(1)° and Z=4. The thermal behavior has been investigated and interpreted in agreement with IR absorption spectrometry and X-ray diffraction experiments. We calculated the 30 normal frequencies of the P3O9 ring with Cs symmetry and proposed the interpretation of the vibrational spectrum of SrTlP3O9·3H2O. The vibrations were assigned and precised to each frequency for different atoms of the ring on the basis of the results of the theoretical isotopic substitutions and in the light of the crystalline structure of the isotypic compounds, SrMIP3O9·3H2O (MI=Rb+, K+ and NH4+), of SrTlP3O9·3H2O. 相似文献
13.
New compounds: Mg3Fe4(VO4)6 and Zn3Fe4(VO4)6 were obtained from a solid state reaction. The temperatures of melting of Mg3Fe4(VO4)6 and Zn3Fe4(VO4)6 amount to 950±5 and 850±5°C, respectively. The indexing results and the calculated unit cell parameters for both compounds are given and suggest that both phases are isotypic with Mn3Fe4(VO4)6. The IR spectra of the above-mentioned compounds are presented. 相似文献
14.
The (C3H12N2)0.94[Mn1.50Fe1.50III(AsO4)F6] and (C3H12N2)0.75[Co1.50Fe1.50III(AsO4)F6] compounds 1 and 2 have been synthesized using mild hydrothermal conditions. These phases are isostructural with (C3H12N2)0.75[Fe1.5IIFe1.5III(AsO4)F6]. The compounds crystallize in the orthorhombic Imam space group. The unit cell parameters calculated by using the patterns matching routine of the FULPROOF program, starting from the cell parameters of the iron(II),(III) phase, are: a = 7.727(1) Å, b = 11.047(1) Å, c = 13.412(1) Å for 1 and a = 7.560(1) Å, b = 11.012(1) Å, c = 13.206(1) Å for 2, being Z = 8 in both compounds. The crystal structure consists of a three-dimensional framework constructed from edge-sharing [MII(1)2O2F8] (M = Mn, Co) dimeric octahedra linked to [FeIII(2)O2F4] octahedra through the F(1) anions and to the [AsO4] tetrahedra by the O(1) vertex. This network gives rise two kinds of chains, which are extended in perpendicular directions. Chain 1 is extended along the a-axis and chain 2 runs along the c-axis. These chains are linked by the F(1) and O(1) atoms and establish cavities delimited by eight or six polyhedra along the [1 0 0] and [0 0 1] directions, respectively. The propanediammonium cations are located inside these cavities. The thermal study indicates that the structures collapse with the calcination of the organic dication at 255 and 285 °C for 1 and 2, respectively. The Mössbauer spectra in the paramagnetic state indicate the existence of two crystallographically independent positions for the iron(III) cations and a small proportion of this cation in the positions of the divalent Mn(II) and Co(II) ones. The IR spectrum shows the protonated bands of the H2N- groups of the propanediamine molecule and the characteristic bands of the [AsO4]3− arsenate oxoanions. In the diffuse reflectance spectra, it can be observed the bands characteristic of trivalent iron(III) cation and divalent Mn(II) and Co(II) ones in a distorted octahedral symmetry. The calculated Dq and B-Racah parameters for the cobalt(II) phase are 710 and 925 cm−1, respectively. The ESR spectra of compound 1 maintain isotropic with variation in temperature, being g = 1.99. Magnetic measurements for both compounds indicate that the main magnetic interactions are antiferromagnetic in nature. However, at low temperatures small ferromagnetic components are detected, which are probably due to a spin decompensation of the two different metallic cations. The hysteresis loops give values of the remnant magnetization and coercive field of 84.5, 255 emu/mol and 0.01, 0.225 T for phases 1 and 2, respectively. 相似文献
15.
Lanthanum acetylacetonate La(C5H7O2)3·xH2O has been used in the preparation of the precursor solution for the deposition of polycrystalline La2O3 thin films on Si(1 1 1) single crystalline substrates. The precursor chemistry of the as-prepared coating solution, precursor powder and precursor single crystal have been investigated by Fourier Transformed Infrared Spectroscopy (FTIR), differential thermal analysis coupled with quadrupole mass spectrometry (TG-DTA-QMS) and X-ray diffraction. The FTIR and X-ray diffraction analyses have revealed the complex nature of the coating solution due to the formation of a lanthanum propionate complex. The La2O3 thin films deposited by spin coating on Si(1 1 1) substrate exhibit good morphological and structural properties. The films heat treated at 800 °C crystallize in a hexagonal phase with the lattice parameters a = 3,89 Å and c = 6.33 Å, while at 900 °C the films contain both the hexagonal and cubic La2O3 phase. 相似文献
16.
Ahlem Chtioui 《Materials Research Bulletin》2009,44(3):560-16812
Chemical preparation, X-ray single-crystal, thermal behaviour, and IR spectroscopy investigations are given for a new organic cation sulfate (C7H10NO)2SO4 (denoted BOAS) in the solid state. This compound crystallizes in the monoclinic space group P21/c. The unit cell dimensions are: a = 7.010(3) Å, b = 11.142(5) Å, c = 20.770(8) Å, β = 95.27(3)° with V = 1615.4(12) Å3 and Z = 4. The structure has been solved using a direct method and refined to a reliability R factor of 0.047. The title compound consists of a framework of isolated SO4 tetrahedral interleaved with organic molecules, so as to build isolated ribbons parallel to a-axis. In the present work, we describe the crystal structure, thermal behaviour and IR analysis of this new compound. 相似文献
17.
(C2H10N2)[Mn2.09Co0.91(HPO3)4] has been synthesized using mild hydrothermal conditions under autogeneous pressure. The compound crystallizes in the triclinic P-1 space group. The unit-cell parameters are a = 5.4061(8), b = 5.4150(7), c = 14.136(2) Å, α = 80.84(1), β = 85.41(1), γ = 60.00(1) and Z = 1. The compound shows a layered structure constructed from M3O12 trimer units linked thorough the (HPO3)2− phosphite oxoanions with the ethylenediammonium cations located between the sheets compensating the anionic charge of the inorganic framework. The IR and Raman spectra confirm the presence of the ethylenediammonium cation and phosphite anion. The diffuse reflectance spectrum is in accordance with the presence of Co(II) and Mn(II) high spin cations in slightly distorted octahedral symmetry. The calculated Dq and Racah parameters for the Co(II) cations are Dq = 710, B = 870 and C = 4100 cm−1. The magnetic measurements indicate the existence of antiferromagnetic interactions as the major interactions. Hysteresis observed at low temperature indicates a weak ferromagnetic component, due to a non-cancellation of spins, with coercitive field of 900 G and magnetization of 700 emu/mol. 相似文献
18.
A bifunctional epoxy resin was modified by using a CO2 fixation solution process in the presence of tetra n-butyl ammonium bromide (TBAB) as catalyst and the modified treated resin was treated by cloisite 30B as nano additive. The Unmodified epoxy resin (UME), CO2 fixated modified epoxy resin (CFME), and CFME/clay nano composite (CFMEN), were cured by diethylenetriamine (DETA). A cycloaliphatic compound as a reactive diluent was used to control the viscosity of high viscose CFME. The exfoliation of organoclay in UME and CFME was investigated by X-ray diffraction and activation energy was computed using the advanced integral isoconversional method. The activation energy dependency demonstrated that the mechanism of UME curing did not change in the presence of nanoclay. In contrast, the CO2 fixation results showed a significant change in the activation energy dependency. The Thermal stability parameters include the initial degradation temperature (IDT), the temperature at the maximum rate of weight loss (Tmax), and the decomposition activation energy (Ed) were determined by thermal gravimetry analysis. Dynamic mechanical thermal analysis measurements showed that the presence of organoclay in CFME increases the Tg of nano composite in contrast to UME. The fracture roughness of UME, CFME and CFNE were determined by scanning electron microscope. The exfoliated UME/1%clay nanocomposite was confirmed by TEM image. 相似文献
19.
Cobalt ethylenediammonium bis(sulfate) tetrahydrate, [NH3(CH2)2NH3][Co(SO4)2(H2O)4], has been synthesised by slow evaporation at room temperature. It crystallises in the triclinic system, space group , with the unit cell parameters: a = 6.8033(2), b = 7.0705(2), c = 7.2192(3) Å, α = 74.909(2)°, β = 72.291(2)°, γ = 79.167(2)°, Z = 1 and V = 317.16(2) Å3. The Co(II) atom is octahedrally coordinated by four water molecules and two sulfate tetrahedra leading to trimeric units [Co(SO4)2(H2O)4]. These units are linked to each other and to the ethylenediammonium cations through OW-H…O and N-H…O hydrogen bonds, respectively. The zero-dimensional structure is described as an alternation between cationic and anionic layers along the crystallographic b-axis. The dehydration of the precursor proceeds through three stages leading to crystalline intermediary hydrate phases and an anhydrous compound. The magnetic measurements show that the title compound is predominantly paramagnetic with weak antiferromagnetic interactions. 相似文献
20.
T JermoumiMustapha Hafid N NiegischM Mennig A SabirN Toreis 《Materials Research Bulletin》2002,37(1):49-57
Experimental determination of the properties of less studied zinc-iron-phosphate glasses was investigated. Glasses of the general composition (50−x)ZnO-xFe2O3-50P2O5, mol%, with x=0, 10, 20, 30 and 40, was chosen for these investigations. These studies included, glass forming, glass density, thermal expansion coefficient, dilatometric softening temperature, an initial test of chemical durability and vibrational properties. It is shown that an Fe/P ratio of the compositions at about 0.6 and 0.8 and the O/P ratio at 3.4 and 3.8 could be considered as chemically durable phosphate candidates. 相似文献