Intensities Of Diffraction Reflections Research Articles

Alkali-activated binders based on technogenic fibrous waste

Alkali-activated binders based on technogenic fibrous waste (TFW) were developed. An increase in the specific surface area (Ssp) of TFW makes it possible to change the strength parameters. Thus, at Ssp = 160 m2/kg, the strength of the binder was 1 MPa, at Ssp = 220 m2/kg, an increase in activity by almost 3 times is noted (compressive strength 3.2 MPa). With an increase in the specific surface of the particles, the microstructure of the binder samples is characterized by a higher density, with a small number of cavities not filled with hydration products. Analysis of the microstructure revealed the presence of a denser matrix in all cases compared to the compositions obtained with a lower specific surface area of TFW. The pressed sample has a dense matrix with an increased number of contact zones between particles; TFW fibers are clearly visible over the entire surface under study. When the alkaline activator NaOH is introduced into the system, the solubility of the crystalline phases of pyroxenes (albite, anorthite) and quartz increases, which is noted by a decrease in the intensity of diffraction reflections. The main chemical composition in the binder is represented by oxides of SiO2, Na2O, CaO, MgO, Al2O3. The presence of sodium-calcium hydroaluminosilicate compounds in the synthesized system of compounds is confirmed by differential thermal analysis. The endothermic peak at 733 °C is associated with the decomposition of sodium-calcium hydroaluminosilicates. The exoeffect peak at 900 °C is associated with the crystallization of tobermorite-like compounds C–A–S–H and C–S–H into wollastonite. The presence of hydrosilicate tobermorite-like compounds is also confirmed by microstructural analysis, where almost the entire surface of waste particles is covered with fibrous new growths, which, most likely, belong to calcium silicate hydrates of tobermorite type C–A–S–H.

Размещение водорода в оксигидриде титана

Possible models of the arrangement of hydrogen atoms at the sites of the cubic lattice of titanium oxyhydride TiOyHp with vacancies in the metallic and nonmetallic sublattices are considered. It was found that titanium oxyhydride retains the B1 type crystal lattice of the initial cubic titanium monoxide TiOy and contains structural vacancies in the metal and oxygen sublattices. Comparison of the found analytical expressions for the intensity of diffraction reflections with experimental X-ray and neutron diffraction data showed that interstitial H atoms in oxyhydrides occupy vacant octahedral positions 4(b) of the oxygen sublattice. No displacement of H atoms in tetrahedral positions 8(c) is observed. A disorder-order phase transition channel associated with the formation of an ordered monoclinic titanium oxyhydride of the Ti5O5 type was found. The distribution functions of Ti, O, and H atoms in the partially ordered monoclinic oxyhydride Ti5.33O5.12H0.74 (Ti0.89O0.85H0.12) with a Ti5O5-type structure are calculated for the first time, and the concentrations of these atoms at the positions of its lattice were found.

Placing of hydrogen in titanium oxyhydride

Possible models of the arrangement of hydrogen atoms at the sites of the cubic lattice of titanium oxyhydride TiOyHp with vacancies in the metallic and nonmetallic sublattices are considered. It was found that titanium oxyhydride retains the B1 type crystal lattice of the initial cubic titanium monoxide TiOy and contains structural vacancies in the metal and oxygen sublattices. Comparison of the found analytical expressions for the intensity of diffraction reflections with experimental X-ray and neutron diffraction data showed that interstitial H atoms in oxyhydrides occupy vacant octahedral positions 4( b) of the oxygen sublattice. No displacement of H atoms in tetrahedral positions 8( c) is observed. A disorder-order phase transition channel associated with the formation of an ordered monoclinic titanium oxyhydride of the Ti5O5 type was found. The distribution functions of Ti, O, and H atoms in the partially ordered monoclinic oxyhydride Ti5.33O5.12H0.74 (Ti0.89O0.85H0.12) with a Ti5O5-type structure are calculated for the first time, and the concentrations of these atoms at the positions of its lattice were found. Keywords:Titanium monoxide, Hydrogen, Nonstoichiometry, Vacancies, Octahedral and tetrahedral positions, Distribution function.

Effect of Mechanical Activation and Gamma-Irradiation on Structural-Phase State of Ti-Al-C Powder Reagents

The influence of mechanical activation and gamma-irradiation on the structural-phase state of Ti-Al-C powder reagents was studied. The following compositions were used for research: 1) 78% Ti + 14% Al + 8% C; 2) 80% Ti + 12% Al + 8% C; 3) 81% Ti + 10% Al + 9% C. Mechanical activation of these compositions leads to an increase in the diffuse background, a decrease in the intensity of diffraction reflections of mixture components and a broadening of peaks, as well as micro-deformations. Depending on the ratio of components, the structural parameters can either increase in comparison with the initial ones, or decrease. The effect of gamma radiation with a dose rate of 1 Gy/s and accumulated dose of 3·104 Gy on the mechanocomposites of the Ti-Al-C system causes unsystematic change in crystal lattices of elements, which can be explained by radiation-stimulated diffusion. Gamma-irradiation also reduces micro-deformations that occur after mechanical activation, while crystallites of the components remain nanoscale.

Induced Spirals in Polyethylene Terephthalate Films Irradiated with Ar Ions with an Energy of 70 MeV

This paper presents the results of a study of the ordering in polyethylene terephthalate (PET) film induced by Ar8+ ions with an irradiation fluence of 2 × 1012 ions/cm2, and of the temporal stability of the induced ordering in the irradiated sample, over a three month period. Immediately after irradiation, sharp new reflections not seen at lower fluences were observed in X-ray diffraction patterns, with angular positions of 2 θ = 9–10° and 19° and variable azimuthal intensities. X-ray reflections, previously observed at lower fluences, were also seen: at 2 θ = 26° and 23°, associated with PET crystallites, and at 2 θ = 5–12°, associated with induced ordering in the amorphous zone. Aging of the irradiated sample led to significant growth of the ordering region in the amorphous zone for angles up to 2 θ < 15°, as well as to dissipation and blurring of the new diffraction reflections at 2 θ = 9–10° and 2 θ = 19° and the formation of a new diffraction ring reflection in the range 2 θ = 11–16°. The azimuthal distribution of diffraction reflection intensities immediately after irradiation displays a clear oblique cross located predominantly along lines at angles of π/4 with respect to the direction of the texture of the PET film, indicating the formation of spiral structures based on the molecular strands of PET. Our experimental results lead us to conclude that the formation of coherent scattering areas in the amorphous region at 2 θ < 15° is due to intra-chain rotations of benzene-carboxyl subunits of repeat units of the PET chain molecules interacting with the residual electric field of a single latent track; whereas the formation of spiral structures is due to the inter-chain interaction of these preordered asymmetric subunits under the influence of the electric fields from overlapping latent tracks.

Long-Wavelength Oscillations of the Intensity of Diffraction Reflections of High-Energy Electrons from a Growing Heteroepitaxial Film due to the Quantum Size Effect with Absorption Taken into Account

An analytical expression is proposed and a graphic illustration is presented for the quantum size effect, arising as a result of the reflection of an electron beam from a growing heteroepitaxial single crystal, with electron absorption taken into account. The intensity curves of the reflected beam are calculated for various values of parameters. Short-wavelength oscillations of the intensity of the electron beam reflected from the film surface are shown to be modulated by long-wavelength vibrations. They occur due to the quantum size effect in the growing film. The total intensity decays exponentially as the layer grows. The obtained theoretical curves are compared with experimental data.

Structural, optical and luminescence properties of CdTe quantum dots: Investigation on the effect of capping ligand ratio

Well-crystallized cadmium telluride quantum dots (CdTe QDs) were fabricated by a simple wet chemical process under open air condition at a growth temperature of 100 °C. Various amounts of the capping ligands were used in order to study the effects of them on the structural, optical and luminescence properties of C dTe QDs. The structural properties were studied using x-ray diffractometer (XRD) and scanning electron microscope (SEM). All the as-obtained CdTe QDs displayed a zinc blende crystal structure with no extra phases observed in the XRD analysis. The diffraction reflection intensities were enhanced with an increase in the capping ratio with the optimum condition achieved at a capping ratio of 1.2. The average particle sizes estimated from various techniques increased with an increase in the amounts of capping ligands used (2.14, 3.19, 2.75, 3.00, 3.27 and 4.47 nm for 0.8, 1.0, 1.4, 1.6 and 2.0 capping ratio). The SEM analysis revealed spherical shaped CdTe QDs with string-like features covering the surface of the QDs observed at higher capping ratio. Aggregation of the CdTe QDs was observed for the QDs prepared at a lower capping ratio (Cd:Cyst of 1:0.8). The Photoluminescence (PL) studies displayed a red shift in the emission wavelength accompanied by variation in the emission peak intensity. The emission wavelength shifted from 558–571 nm for 0.8–2.0 capping ratio. Highest PL emission peak intensity was obtained at a capping ratio of 1.2 which was in line with the results obtained from the XRD. The absorbance of the as-prepared CdTe QDs increased while the band gap decreased with increasing capping ratio due to the growth of the QDs.

Modeling quasi-lattice with octagonal symmetry

We prove the possibility to use the method of modeling of a quasi-lattice with octagonal symmetry similar to that proposed earlier for the decagonal quasicrystal. The method is based on the multiplication of the groups of basis sites according to specified rules. This model is shown to be equivalent to the method of the periodic lattice projection, but is simpler because it considers merely two-dimensional site groups. The application of the proposed modeling procedure to the reciprocal lattice of octagonal quasicrystals shows a fairly good matching with the electron diffraction pattern. Similarly to the decagonal quasicrystals, the possibility of three-index labeling of the diffraction reflections is exhibited in this case. Moreover, the ascertained ratio of indices provides information on the intensity of diffraction reflections.

New approaches to scaling data measured on a CCD diffractometer

New methods have been developed for scaling the intensities of diffraction reflections measured on a diffractometer with a CCD detector. The algorithm involves cyclic alternation of the refinement of a structure model from experimental data corrected for anisotropic effects with the refinement of anisotropic parameters from initial data for a fixed structure model. The first method consists of refining scale factors for the intensities after they have first been corrected for anisotropic effects of known physical nature (thermal diffuse scattering, absorption, extinctionetc.). It has been shown that the majority of the observed biases of intensities are caused by the characteristics of the CCD detector and the technique used for data collection on the diffractometer, rather than by the properties of the sample. The second (alternative) method of fixed scaling has been implemented here. This method does not require refinement of empirical scale factors but uses intensity correction maps obtained by averaging the results derived from several experiments with different crystals. The first map describes the non-uniformity of the response over the surface area of the detector. The second map accounts for distortions dependent on the setting angles of the goniometer. The methods were checked for data measured on an Oxford Diffraction Xcalibur Sapphire 3 CCD diffractometer. The proposed methods significantly improve the results of the refinement and make it possible to obtain a structure model that is reproduced in repeated investigations of samples of the same compound.

X-Ray Diffraction Study of Micro Amounts of Polycrystalline Samples

With the use of reference polycrystalline 6h-Al2O3 (NIST SRM- 1976) and MoO3 samples we consider the most significant geometric and physical factors affecting the accuracy of X-ray diffraction data obtained on a diffractometer equipped with a flat two-dimensional detector (Debye-Scherrer scheme). A general strategy to measure polycrystalline samples in the amount of 20–30 fug is proposed. By the example of SRM-1976 it is shown that with the proper processing of two-dimensional diffraction patterns and the introduction of certain corrections the angles 2θ can be measured with the accuracy not less than ±0.01°. Even with a strong tendency of particles towards preferred orientation the relative intensities of diffraction reflections are shown to be obtained with the accuracy not less than ±10%.

Thermal Expansibility of 310S Steel-Based PVD Coating in Presence of Metastable Phase

The paper discusses the examination of the thermal expansibility of a coating composed of the austenitic steel 310S using the X-ray diffraction technique. Temperature measurements were made in the temperature interval of Tamb200°C, in which the transition of the metastable bcc phase forming the as-applied coating into an fcc-type phase occurred in the coating. The values of the coefficients of thermal expansion of both phases were determined by using the weighted average of the intensities of diffraction reflections recorded. The values of the coefficients of thermal expansion of both phases within the entire examination range (Tamb200°C), determined as the weighed averages with the weight allowing for the intensities of individual reflections, were found to be, respectively, 0.910-5 K-1 for the bcc phase and 1.510-5 K-1 for the fcc phase, and by approx. 0.110-5 K-1 lower than the values typical of the phases of austenite and ferrite in conventional steels.

Crystallographic characteristics and phase transitions in the [N(C2H5)4]2CdBr4 crystal in the low-temperature range

The results of x-ray structural studies of the [N(C2H5)4]2CdBr4 crystal at low temperatures are presented. The unit cell parameters and the thermal expansion coefficients along the main crystallographic directions are measured at temperatures in the range from 90 to 320 K. The integrated intensities of the diffraction reflections are investigated as a function of the temperature. It is shown that the curves a = f(T), c = f(T), I 500 = f(T), and I 006 = f(T) at temperatures T 1 ≈ 174 K and T 2 ≈ 226 K exhibit anomalies in the form of abrupt changes in the lattice parameters and the diffraction reflection intensities. This indicates that the [N(C2H5)4]2CdBr4 crystal undergo phase transitions at these temperatures. Moreover, there is an anomaly in the form of a small maximum at the temperature T 3 = 293 K.

Orientational order parameter in CO2-based alloys with rare gases from THEED data: pure CO2

Using the transmission high-energy electron diffraction technique, we study the temperature dependence of the diffraction reflection intensities from the solid phase of CO2. To deduce absolute values of the orientational order parameter, we modify the existing reconstruction method to take into account the triatomic shape of the molecule. It is shown that for triatomic solids a higher-rank order parameter, η4, is important and cannot be neglected. Application of the modified approach yield η and η4 values as a function of temperature over the range from 6 to 70K. Both orientational order parameters prove to be a nonmonotone function of temperature.

Specific features of structural, dielectric, and optical properties of CdTiO3

The optical and dielectric properties and the structure of crystalline and ceramic perovskite CdTiO3 modifications have been investigated. The multiplication of the unit cell along three perovskite axes is found. The new possible space groups of symmetry D 2 18 and D 2 21 are determined. It is elucidated how small radiation doses affect the structure and properties of crystalline and ceramic perovskite modifications. Analysis of the intensities of diffraction reflections demonstrate that the defect formation leads to an increase in the antiparallel displacements of Cd atoms in the unit cell.

ChemInform Abstract: PREPARATION AND STRUCTURE OF THE 1:2 Π‐MOLECULAR COMPLEX OF PHENOTHIAZINE WITH PYROMELLITIC DIANHYDRIDE

Single crystals of the black 1:2 donor–acceptor complex of phenothiazine with pyromellitic dianhydride, PTZ:(PMDA)2, were grown by plate sublimation at ∼163 °C from the zone‐refined components. The l:1 complex is produced at lower temperatures. Crystals of the 1:2 complex are monoclinic, P21/c, Z=4, a=7.689(3), b=12.953(5), c=28.14(2) A, β=104.30(2)° at T=19 °C. The structure was refined from 2863 x‐ray diffraction reflection intensities for which I>2.0σ(I) to R=0.064 and Rw=0.057. The structure consists of continuous ... DADA ... polar stacks as does the l:1 complex, but the stacks, which are parallel to the a axis, are separated in the c direction by the extra PMDA molecule. The overlap of adjacent molecules in the stack in the 1:2 complex is more closely related to the overlap of adjacent molecules in the π‐molecular complex of PMDA with anthracene. The resultant angle between the stack axis and the normal to the planar molecules is 27.1°. The geometry of the individual molecules in the l:2 complex is ...

Preparation and structure of the 1:2 π-molecular complex of phenothiazine with pyromellitic dianhydride

Single crystals of the black 1:2 donor–acceptor complex of phenothiazine with pyromellitic dianhydride, PTZ:(PMDA)2, were grown by plate sublimation at ∼163 °C from the zone-refined components. The l:1 complex is produced at lower temperatures. Crystals of the 1:2 complex are monoclinic, P21/c, Z=4, a=7.689(3), b=12.953(5), c=28.14(2) Å, β=104.30(2)° at T=19 °C. The structure was refined from 2863 x-ray diffraction reflection intensities for which I>2.0σ(I) to R=0.064 and Rw=0.057. The structure consists of continuous ... DADA ... polar stacks as does the l:1 complex, but the stacks, which are parallel to the a axis, are separated in the c direction by the extra PMDA molecule. The overlap of adjacent molecules in the stack in the 1:2 complex is more closely related to the overlap of adjacent molecules in the π-molecular complex of PMDA with anthracene. The resultant angle between the stack axis and the normal to the planar molecules is 27.1°. The geometry of the individual molecules in the l:2 complex is not significantly different from those in the l:1 complex.

Effect of low-cycle loading on the mechanical characteristics and structure of unidirectional organoplastic

1. Low-cycle loading causes significant variations in the mechanical properties of unidirectional organoplastic — a variation in the character of the σ — e relationship and corresponding variations in the elastic modulus, the area of the hysteresis loop, and the accumulation of residual strain. 2. Variations in the structure of the reinforcing fibers — the appearance of residual microstrains, a fact that we can associate with conformal transitions in the macromolecules — a variation in the intensity of diffraction reflections, which suggest variations in the degree of mesomorphicity and the appearance of flaws in the structure of the fibers are established by radiographic examinations. 3. The low-cycle loading of organoplastic by stresses σ∼⩽0.88σf gives rise to an increase in the elastic modulus. The elastic modulus also increases for stresses σ∼>0.88σf in the initial interval, but does not attain the level observed for lower stresses, and it begins to decrease after a certain number of cycles. The character of the variation in the elastic modulus can be explained by the effect of two factors: the increase is associated with conformai transitions in chains of macromolecules and by ordering of the structure, and the decrease with damage accumulation. 4. The magnitude of the residual strain during fatigue loading increases with increasing cyclic stress and may reach 1.5% prior to failure. 5. The area of the hysteresis loop decreases under cyclic loading. The area of the loop increases prior to failure. The total energy dissipation increases with decreasing cyclic stress. 6. Preliminary cyclic loading on a base N=103 cycles does not have a pronounced effect on the strength of unidirectional organoplastic.