High-temperature X-ray Diffraction Method Research Articles

Effect of crystallization conditions on polymorphic diversity of malic acid RS — Racemate

Enantiomers (R(+) and S(−)), RS-racemate (double compound) and (R+S)-conglomerate (mechanical mixture of enantiomers) of malic acid C4H6O5 have been investigated by means of X-ray diffractometry and high temperature X-ray diffraction method. The RS-racemate was found to be able to form three polymorphic modifications, which we denominated as M1 (monoclinic, space group P21/c), M2 (monoclinic, space group Cc), and Tc (triclinic, space group P-1), the latter modification having been unknown before. Modification Tc was also described, and its Xray diffraction characteristics, including interplanar spacings d, hkl indices, unit cell parameters, were defined. In addition, X-ray diffraction characteristics for both reported earlier M1 and M2 monoclinic polymorphic modifications were measured with higher accuracy. The ability of RS-racemate to form one of the above three modifications (M1, M2, and Tc) or their mixtures containing various proportions and combinations of the components (M1+M2, M1+Tc, or M2 +Tc) was found to depend on the type of crystallization medium (a melt, aqueous medium, ethanol or acetone solution), crystallization rate (from 2–3 minutes to 4 months), and crystallization temperature. Heating S-enantiomer and M1 RS-racemate up to their respective melting points (100 °C and 124 °C, correspondingly) only made them undergo thermal deformations, while heating (R+S)-conglomerate in the temperature range of 96–110 °C resulted in its homogenization to form M2 RS-racemate, which, near the melting point (118 °C), namely, in the range of 112–116 °C, was transformed into M1 RS-racemate.

Nanocrystallization in Fe75Mo2.5Mn2.5Si6B14 amorphous alloy

Abstract Structure changes in Fe75Mo2.5Mn2.5Si6B14 amorphous alloy at heating within temperature range of 293–878 K have been studied by means of high-temperature X-ray diffraction method. Intensity curves and main structure parameters estimated from them are analyzed. It is shown that nanocrystallization starts from formation of clusters, size of which as well as a density and volume fraction notably depend on temperature.

Thermal stability and expansion studies of cesium molybdates and cesium thorium molybdates

In Cs–Mo–O system, Cs2MonO3n+1 (n=1, 3, 5 and 7) were prepared by solid state route and n=7 was established as the highest stable analog. Differential thermal analysis of the compound Cs2MoO4 (n=1) in air showed a reversible phase transition followed by melting whereas compounds with n=3, 5 and 7 did not show any phase transition up to their melting temperatures. Thermal expansion of all the molybdates were studied in vacuum using high temperature X-ray diffraction method. In quaternary Cs–Th–Mo–O system, Cs2Th(MoO4)3 and Cs4Th(MoO4)4 were synthesized by reacting cesium molybdate and thorium molybdate in 1:1 and 2:1M ratios, respectively, at 873K in air. Both compounds did not show any phase transition up to the melting and the compounds showed positive thermal expansion when heated in vacuum in the temperature range of 298–873K.

Thermodynamic and spectroscopic properties of spinel with the formula Li4/3Ti5/3O4

In the present work temperature dependence of heat capacity of Li4/3Ti5/3O4 has been measured for the first time in the range from 6 to 330K by precision adiabatic vacuum calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity C°p(T), enthalpy H°(T)−H°(0), entropy S°(T)−S°(0) and Gibbs function G°(T)−H°(0), for the range from T→0 to 670K. Raman and IR investigations have also been performed. The high-temperature X-ray diffraction method was used for the determination of thermal expansion coefficients.

Synthesis of hydroxyapatite whiskers

The synthetic method of nanosized hydroxyapatite Ca5(PO4)3OH (∼80–100 nm) is optimized. The functional structure is analyzed in a wide temperature range using the combination of the high-temperature X-ray diffraction method, differential thermal analysis, and infrared spectroscopy. A novel method of obtaining hydroxyapatite whiskers without using hydrothermal conditions is developed.

Structure and Thermal Transformations of Hydrated Magnesium Silicates

The article is devoted to an estimation of phase transformations of silicates magnesium at heating in the temperatures range from 0°C to 1100°С. The object of study is a silicates of magnesium containing oxide nickel ore. Differentially-thermal (NETZSCH 449 C - Jupiter), weights – spectrometer (QMS 403 C Aёolos), high-temperature X-ray diffraction, electron-probe microanalysis (JSM - 5900 LV) and chemical analysis methods have been used in the study. The temperature ranges of existence Mg6[(OH)8Si4O10] and Mg2Si2O6 are obtained. Parameters of an elementary cell of the above minerals and their changes with temperature and features of nickel distribution in magnesium silicates with various ration MgO/SiO2 are defined in this work.

Solubility studies and thermal expansion coefficient of uranium–lanthanum mixed oxide system

Uranium–lanthanum mixed oxides (U 1− y La y ) O 2± x ( y = 0.1–0.9) of 13 different compositions were prepared by combustion synthesis using citric acid as the fuel. Sintering of the solid solutions was carried out at 1873 K. The solubility limit of La 2O 3 in UO 2 at 1873 K was determined to be ∼82% from the room temperature XRD patterns of the sintered samples. However, the solubility limit of La 2O 3 in the mixed oxides prepared by solid-state route and sintered under identical conditions was found to be ∼70%. The coefficients of thermal expansion for (U 1− y La y ) O 2± x ( y = 0.2, 0.4, 0.6, 0.8) in the temperature range 298–1973 K determined by high temperature X-ray diffraction (HTXRD) method are 17.7, 18.5, 19.2 and 20.0 × 10 −6 K −1, respectively.

Thermal Contraction of Electrodeposited Bi/BiSb Superlattice Nanowires

The lattice parameter of Bi/BiSb superlattice nanowire (SLNW) has been measured using in situ high-temperature X-ray diffraction method. The single crystalline Bi/BiSb SLNW arrays with different bilayer thicknesses have been fabricated within the porous anodic alumina membranes (AAMs) by a charge-controlled pulse electrodeposition. Different temperature dependences of the lattice parameter and thermal expansion coefficient were found for the SLNWs. It was found that the thermal expansion coefficient of the SLNWs with a large bilayer thickness has weak temperature dependence, and the interface stress and defect are the main factors responsible for the thermal contraction of the SLNWs.

Thermal expansion behaviors of hcp and fcc Co nanowire arrays

The lattice parameters of as-prepared and annealed Co nanowires with hcp and fcc structures have been measured using the in situ high-temperature x-ray diffraction method. The hcp and fcc Co nanowires have been fabricated within the porous anodic alumina membranes by a direct-current electrodeposition technique. The results indicate that the variational quantity of the interplanar spacing for hcp Co nanowire arrays is bigger than that for fcc Co nanowire arrays in spite of as-prepared and annealed samples. The structural difference between hcp and fcc Co nanowires results in the different thermal expansion behaviors.

The synthesis and transport properties of the cuprates La2 − x Sr1 + x Cu2O6 + δ

The cuprates La2 − xSr1 + xCu2O6 + δ(x = 0, 0.1, 0.2) are synthesized by solid-state method. Their dc conductivity was studied over the 373 to 1173 K temperature range and 10 to 2.1 × 104 Pa oxygen partial pressure range by using four-probe technique. It is shown that the cuprate conductivity in air is maximal at ∼673 K; it is 60 S/cm for La2SrCu2O6.09; 68 S/cm, for La1.9Sr1.1Cu2O6.18; and 81 S/cm, for La1.8Sr1.2Cu2O6.10. The thermal expansion coefficient of La2SrCu2O6.09 is determined by thermomechanical method and high-temperature X-ray diffraction method; its value (16 ppm K−1) shows that the material is compatible with the ceria-based solid electrolytes during the thermal cycling.

Thermal Expansion Behaviors of Bismuth Nanowires

The linear and volumetric thermal expansion coefficients of bismuth nanowire and nanoflower have been measured from 298 to 478 K by high-temperature X-ray diffraction methods. The bismuth nanowire and nanoflower were prepared by a simple solvothermal technique. It was found that the linear and volumetric thermal expansion coefficient of the nanowire decreases initially, then increases, and decreases finally with increasing temperature. The nanowire and nanoflower possess smaller linear thermal expansion coefficient in the a-axis direction in the whole measured temperature range and in the c-axis direction at high temperature as compared to the conventional bulk bismuth. The volumetric expansion coefficients of the nanowire and nanoflower are always smaller than those of the corresponding bulk materials. The results were discussed on the basis of the contributions from point defects, stress, and valence electrons. Our results demonstrated that the anisotropic thermal expansion behavior of bismuth nanowires is an intrinsic property.

Thermal expansion of TRU nitride solid solutions as fuel materials for transmutation of minor actinides

The lattice thermal expansion of the transuranium nitride solid solutions was measured to investigate the composition dependence. The single-phase solid solution samples of (Np 0.55Am 0.45)N, (Pu 0.59Am 0.41)N, (Np 0.21Pu 0.52Am 0.22Cm 0.05)N and (Pu 0.21Am 0.18Zr 0.61)N were prepared by carbothermic nitridation of the respective transuranium dioxides and nitridation of Zr metal through hydride. The lattice parameters were measured by the high temperature X-ray diffraction method from room temperature up to 1478 K. The linear thermal expansion of each sample was determined as a function of temperature. The average thermal expansion coefficients over the temperature range of 293–1273 K for the solid solution samples were 10.1, 11.5, 10.8 and 8.8 × 10 −6 K −1, respectively. Comparison of these values with those for the constituent nitrides showed that the average thermal expansion coefficients of the solid solution samples could be approximated by the linear mixture rule within the error of 2–3%.

Structure and negative thermal expansion of Pb 1 − xBi xTiO 3

Pb 1- x Bi x TiO 3 ( x = 0.0–0.1) compounds were prepared to study the unique dopant effect of bismuth in PbTiO 3. Their thermal expansions and structures were investigated by high-temperature X-ray diffraction and X-ray Rietveld method. The results indicated that Bismuth substitution evidently weakened the tetragonality of PbTiO 3 solid solution, but increased the spontaneous polarization. Both the enhanced spontaneous polarization and the decreased tetragonality led to small volume shrinkage with temperature rising, where the average volumetric thermal expansion coefficient changed from − 1.99 × 10 − 5 /°C for pure PbTiO 3 to − 0.56 × 10 − 5 /°C for Pb 0.90Bi 0.10TiO 3. The Curie point of Pb 1 − x Bi x TiO 3 was slightly raised compared to PbTiO 3 and permitted one to use it in a wide temperature range.

X-ray diffraction study on the thermal properties of CuMPt 6 (M = 3d elements) alloys

The effect of ternary addition of the 3d elements Ti, V, Cr, Mn, Fe, Co and Ni to CuPt 3 to form ternary CuMPt 6 alloys on the thermal properties was investigated using high-temperature X-ray diffraction method. Data obtained were utilized to determine the lattice parameters, coefficients of thermal expansion, Debye temperature and mean-square displacements of an atom. It was found that the addition increases the lattice spacing, increases the degree of thermal expansion and lowers the Debye temperature. The results are discussed within the framework of the classical theory.

Lattice thermal expansions of NpN, PuN and AmN

Lattice parameters of NpN, PuN and AmN were measured by a high temperature X-ray diffraction method from room temperature up to 1478 K. Linear thermal expansions of these TRU nitrides were determined as a function of temperature. The average coefficients of linear thermal expansion from 293 to 1273 K were 8.8, 11.1 and 11.2 × 10 −6 K −1 for NpN, PuN and AmN, respectively. The instantaneous coefficient of thermal expansion either at 293 or at 1273 K against the reciprocal decomposition temperature under 1 atm of nitrogen showed a linear relationship for TiN, ZrN, HfN, UN, NpN and PuN. Based on this relationship, the decomposition temperature of AmN was roughly predicted to be 2700 K.

High-temperature thermal behaviour of Cr-Doped LiMn2O4 spinels synthesized by the sucrose-aided combustion method

Chromium doped spinels LiCrYMn2−YO4 (0.2≤Y≤0.8) has been synthesized by the sucrose-aided combustion procedure. The thermal behaviour, phase homogeneity and structural characteristics of the samples were studied by thermal analysis, coupled mass spectrometry, and room-and high-temperature X-ray diffraction methods. It was found that the ‘as prepared’ samples contained residual organic impurities undetectable for X-ray diffraction, that burn out completely at 400°C. Samples treated between 400 and 750°C are single phase spinels, whose crystallites size increase from 10 to 50 nm on increasing the temperature. Cr-doping enhances the thermal stability of the spinels, which augments on increasing the Cr content Y. The enhanced thermal stability of the spinels has been accounted for based on the high excess stabilization energy of Cr3+ in octahedral ligand field.

High-temperature X-ray diffraction and specific heat studies on GdAlO 3, Gd 3Al 5O 12 and Gd 4Al 2O 9

Gadolinium aluminates, GdAlO 3, Gd 3Al 5O 12 and Gd 4Al 2O 9 were synthesized by the solution combustion method. Very fine particles in the nanoparticle range of ∼10–20 nm could be prepared by this method as evidenced by surface area measurement by multipoint BET method. Thermal studies on these compounds were carried out using high-temperature X-ray diffraction (HT-XRD) and differential scanning calorimetry (DSC) methods. The thermal expansion coefficients of GdAlO 3, Gd 3Al 5O 12 and Gd 4Al 2O 9 were calculated from the lattice parameter data and specific heats were calculated from DSC data. The lattice parameters of GdAlO 3 and Gd 3Al 5O 12 were found to increase linearly with temperature whereas Gd 4Al 2O 9 did not show a linear trend. The specific heats of these compounds show an increasing trend with increase in aluminum atom fraction. Based on the thermodynamic data available in the literature and the specific heat data obtained in this study, oxygen potential diagram was constructed at 1000 K.

Lattice thermal expansions of (Dy, Zr)N solid solutions

ZrN is a possible candidate for the diluent material for the nitride fuels containing transuranium elements. In the present study, ZrN, DyN and their solid solutions (Dy x Zr 1− x )N ( x = 0.2, 0.5 and 0.8) as the analogous fuel material, were prepared by powder metallurgical method through the hydrides. Lattice thermal expansions of these nitrides were measured by a high-temperature X-ray diffraction method from room temperature to 1414 K. The average linear thermal expansion coefficients from 293 to 1300 K for these nitrides increased with Dy fraction x from 7.86 × 10 −6 K −1 (ZrN) to 9.54 × 10 −6 K −1 (DyN). The effects of the impurities and hypostoichiometry on the lattice parameters and thermal expansions are discussed. On the analogy with the results on the composition dependence of the thermal expansion coefficients, the preferable effect of ZrN as the diluent material is suggested.

X‐ray investigations of nanopowder WO3 thick films

AbstractNanoparticle tungsten trioxide thick films based on commercial WO3 nanopowder and powder mixtures with different concentrations of metals (Ag, In and Bi) were prepared by screen‐printing onto alumina substrates. The changes in phase composition, crystallite size and cell parameters induced in tungsten trioxide thick films by the inclusion of metal impurities were investigated by X‐ray diffraction (XRD). Some of the samples were further analysed using a high temperature XRD method. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Diameter-depended thermal expansion properties of Bi nanowire arrays

The lattice parameter of bismuth nanowires has been measured using the in situ high-temperature x-ray diffraction method. Single-crystalline Bi nanowire arrays with the diameters from 10nmto250nm have been fabricated within the porous anodic alumina membranes by a pulsed electrodeposition technique. Different temperature dependencies of lattice parameter and thermal expansion coefficient were found for Bi nanowires with different diameters, and there is a transition from positive thermal expansion coefficient at low temperature to negative one at high temperature, and the transition temperature shifts to high temperature with the increase in the diameter of Bi nanowires.