Differential Thermal Analysis Results Research Articles

Towards white light emission in Dy3+/Sm3+ co-doped niobio silicate glasses via adjusting doping concentration and excitation wavelength for w-LED applications

The commercial LED has the disadvantages of low thermal stability and poor luminous quality at high temperature due to the organic resin encapsulation phosphor, and luminous glass is one of the effective ways to solve this problem. A series of niobium silicate (SiO2–Nb2O5–Na2O–K2O–Dy2O3–Sm2O3, labeled as SNNKDS) luminous glasses have been obtained by melt quenching method. The results of differential thermal analysis prove the existence of high thermal stability. The infrared spectrum, Raman spectrum and the calculation of physical parameters reveal the excellent thermal stability and stable structure of the prepared glass. The optical properties of luminescent glass have been studied in detail, the energy transfer from Dy3+ ions to Sm3+ ions has been observed, the Dy3+/Sm3+ co-doping glasses can achieve warm white light emission by changing the excitation wavelength and the doping amount of Sm3+. The variable temperature emission spectrum of SNNK:0.8D0.4 S is analyzed. At 423 K, the comprehensive emission intensity is 79.91 % of that at room temperature, the ΔC value of colorimetric shift at 473 K is 2.1 × 10−2. The warm white light output with excellent correlated color temperature (3746 K) has been achieved using glass samples encapsulated with 395 nm LED chip. The analysis shows that Dy3+/Sm3+ co-doped niobium silicate glasses can be regarded as a candidate for the w-LED applications.

ДОСЛІДЖЕННЯ МОДИФІКОВАНОГО В’ЯЖУЧОГО ДЛЯ ВИГОТОВЛЕННЯ ГАЗОБЕТОНУ

In the case of energy saving, the main direction in the technology of modern wall materials is to reduce the density in order to achieve better thermal performance while simultaneously increasing the strength characteristics, i.e. creation of effective wall materials. One of these materials is aerated concrete, which is successfully used all over the world. One of the ways to increase the physical and mechanical properties of the binder as the main component of aerated concrete and to expand the raw material base can be the use of waste from all kinds of production, as well as the secondary use of damaged building materials from destroyed buildings and structures as a result of hostilities (recycling). The purpose of the research is to obtain aerated concrete on a modified binder using recycling of destroyed building materials. At this stage, a modified binder is being studied. As a result of the research, the optimal ratio of the components of the modified binder (Portland cement, metakaolin, brick mortar) was determined. Mathematical models describing the dependence of the bending and compression strength of the binder on its composition were obtained. The results of X-ray phase and differential thermal analysis show that the introduction of methacoaline and brick mortar additives into the binder based on Portland cement, after 28 days of normal hardening, do not cause new phase and mineralogical formations compared to samples without additives, but only affect the quantitative mineralogical storage. More intensively expressed hydro-silicate phases and a decrease in crystallization calcium hydroxide are observed. The micrographs of the structure of the obtained binder clearly show the monolithic structure of the cement stone, the alkali-dispersed cement grains, sand and calcium hydro-silicate clusters are visible.

Environmental – Solar thermal effects a long-term on the efficiency of amorphous climate-resilient mortar using a central composite design application

The objective of this investigation is to evaluate the durability of dune sand mortar containing display e-glass waste (DEGW) in severe Saharan environments, chemical attacks, or other factors that can cause cementitious materials to deteriorate at long- term. The aim is to use DEGW powder as a partial replacement for dune sand in various mortar mixtures and assess the performance of hardened mortar in terms of ultrasonic pulse velocity, dynamic elasticity modulus, compressive strength, and flexural strength and sportivity. The study also examines the influence of the curing period and different climatic conditions in curing environments, such as those in Algeria's Sahara region. The Response Surface Methodology (RSM) was used to adjust the e-waste glassy mortar, with the statistical tool Central Composite Design (CCD) approach. The hydration of cement compounds was monitored using differential thermal analysis (DTA), thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), and X-ray diffraction (XRD). The DEGW was replaced in 5% increments from 0% to 20%. The results showed that the glassy dune sand mortar exhibited the highest properties at 20% incorporation after 365 days of severe climatic conditions. The feasibility of the proposed quadratic model was recommended for the five responses by RSM, in which the coefficient of determination (R2) ranges from 0.93 to 0.97, showing the model’s high significance. For structural display e-glassy dune sand mortar, display glass E-waste can replace 20% of dune sand, which improves all durability and environmental sustainability. Furthermore, the DSC, TGA / DTA results and XRD analysis showed that the < 0.08 mm class exhibited good pozzolanic behaviour, and the specimens significantly improved as curing periods increased.

Халлимонд түтігіндегі мыс сульфидті минералдардың флотациясы

Under laboratory conditions, studies were carried out to determine the hydrophobicity of the surface of copper sulfide minerals bornite and chalcopyrite by differential thermal analysis and the infrared (IR) spectra of samples of these minerals were studied before and after the experiments. From the nature of the absorption of copper sulfide minerals by IR radiation, it is possible to determine the best indicators of the adsorption of reagents on the surface of minerals. When treating the chalcopyrite surface with anabazinium-O, O-dimethylthiophosphate and N-phenylthiosemicarbazide reagents N-morpholinylacetic acid has been found to weaken hydrogen bonds and evaporate adsorbed moisture. This indicates an increase in the hydrophobicity of the chalcopyrite surface compared to bornite. Studies of the non-soil flotation of the monomineral fraction of sulfide minerals were carried out in the Hallimond tube. During flotation of chalcopyrite treated with a solution of 1% N-phenylthiosemicarbazide of N-morpholinyl acetic acid, its extraction was 94.54%. The achieved indicators are confirmed by the results of differential thermal analysis and IR spectroscopy

Fine martensite and beta-grain variational effects on mechanical properties of Ti–6Al–4V while laser parameters change in laser powder bed fusion

In this study, several variations of Ti–6Al–4V β-grains and α′-martensites were observed while changing the combinations of laser parameters and keeping the energy density (ED) constant in the laser powder bed fusion (LPBF) process. Several combinations of laser power, scanning speed, and hatch spacing were considered, resulting in high product density between 99.3% and 100.0%. Accordingly, tensile specimens were fabricated to observe the above strategic fabrication and microstructural effects on tensile properties. At the same time, microhardness was also measured to observe the similarities. However, the size and shape of the β-grains differed significantly, while the scanning speed gradually decreased along with the laser power, with the shape changing from irregular to classically hexagonal and the size increasing sharply. Using the results of differential thermal analysis (DTA), it can be said that most of the tertiary and quaternary α′-martensites formed after the following few thermal cycles below 370 °C. Similarly, the α′-particles decomposed and formed β-particles due to thermal treatment at 370 °C. Therefore, a denser and higher number of tertiary and quaternary α′-martensites and a lower number of primary and secondary α′-martensites occurred, while the cooling rate decreased and the number of thermal cycles increased due to a lower scanning speed. These phenomena increased the hardness 370–395 HV and deteriorated the yield strength 1250-840 MPa. Changes in track overlap (hatch spacing) of 30–50% affect mechanical and microstructural characteristics more than track overlap of 10–25%. The columnar β-grains became longer and wider as the lane overlap increased from 30 to 50%. At the same time, some β-grains also changed to contain finer and fewer α′-martensites. These factors reduced both hardness and tensile properties.

A Study on Smelting Temperature through analysis of Slag Excavated from Iron Manufacturing Remains on Site of Jangamjinseong in Seocheon, Korea

This study studied the smelting temperature by the principal components, crystal structure, microstructure, and differential thermal analysis on four slags excavated from iron manufacturing remains on site Jangamjinseong in Seocheon, Korea. As a result of the principal component analysis, the content of the T⋅Fe and Deoxidation agent which was the same as the characteristics of the direct smelting slag. As a result of the crystal structure analysis, Fayalite(Fe&lt;sub&gt;2&lt;/sub&gt;SiO&lt;sub&gt;4&lt;/sub&gt;) and Wustite(FeO) were detected. and as a result of microstructure analysis, Fayalite and Wustite were present on the Glass Matrix. As a result of differential thermal analysis, Fayalite was melted at an endothermic peak of 1,132.0°C. At 1,370.0°C, Wustite was melted. In No. 2, it was found that Fayalite melted at an endothermic peak of 1,096.0°C, and Wustite melted at 1,311.0°C. As a result of the analysis of the FAS ternary phase diagram and the FCS ternary phase diagram, the smelting temperature range was 1,150.0 to 1,250.0°C. The FeO-SiO&lt;sub&gt;2&lt;/sub&gt; binary state is also a range in which Fayalite is melted on Wustite + Fayalite to become a Wustite + Liquid phase. When combined with the results of differential thermal analysis, the range of the smelting temperature is 1,096.0°C to 1,370.0°C. To sum up all the results of the analysis, the steel relics in the site of Jangamjinseong in Seocheon used a direct smelting method, and were carried out in the range of 1,096.0℃ to 1,370.0℃ during the process.

Thermochemical Properties of Synthesized Urea from Recovered Ammonia and Carbon Dioxide in Well-Ordered Nanospaces of Hollow Silica Spheres.

The present work investigated the thermochemical properties of urea synthesized in well-ordered nanospaces of porous hollow silica spheres' shells from recovered ammonia and carbon dioxide in aqueous solution. Thermochemical behaviors of the urea synthesized in well-ordered nanospaces of the hollow spheres' shells prepared with 1-dodeclyamine were analyzed from the results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and endothermic peaks assigned as the phase transition and decomposition were observed at ca. 440 and 514 K, respectively, which were higher than those of pristine urea (405 and 408 K, respectively), probably because of the nanoconfinement effect. The decomposition behavior was also confirmed by the result of diffuse reflectance infrared Fourier transform (DRIFT) spectra of the samples treated at various temperatures up to 573 K, and the decomposition of urea synthesized in the well-ordered nanospaces of the hollow spheres' shells started at 468 K and completed up to 533 K.

QUASIBINARY SYSTEM Ag7PSe6– Ag2Se

Semiconductor binary and ternary argentum selenides are of considerable practical interest, particularly as promising thermoelectric materials. These include Ag2Se, a narrow-band semiconductor, and Ag7PSe6, with a disordered cationic sublattice and a rigid anionic framework that causes efficient phonon scattering. Doping of Ag7PSe6 with the narrow bandgap semiconductor Ag2Se should increase its conductivity and Ag2Se with a more disordered Ag7PSe6 argyrodite phase to a decrease in thermal conductivity. In both cases, this should increase the thermoelectric figure of merit of the respective phases. At the same time, establishing the conditions for obtaining doped phases requires studying the conditions of their existence in the Ag7PSe6-Ag2Se system. Present work studies phase equilibria in the Ag7PSe6-Ag2Se system in the entire concentration range. A corresponding phase diagram was constructed based on the X-ray phase and differential thermal analysis results. It was found that the Ag7PSe6-Ag2Se system is quasi-binary. It is characterized by four processes: two eutectoid processes at 405 K and 433 K, caused by the presence of two polymorphic modifications in Ag2Se and Ag7PSe6, respectively; eutectic process at 893 K (the coordinates of the eutectic point are 893 K and ~8 mol% Ag2Se) and monotectic process at 977 K. Above this temperature, in the concentration range of ~9 - ~87 mol%, a region of immiscibility in the liquid is observed. The homogeneity regions of the initial components are less than 5 mol%.&#x0D; Keywords: quasibinary system; selenides; phase equilibria; phase diagram.

Effect of sintering parameters on phase evolution, microstructural development and mechanical behavior of Ni46Al12Co18Cr8Fe12Mo4 high entropy alloy synthesized via mechanical alloying and spark plasma sintering

The aim of this research work was to study phase evolution, microstructural development and resulting mechanical properties in Ni46Al12Co18Cr8Fe12Mo4, at. % high entropy alloys (HEAs) synthesized via spark plasma sintering (SPS) of 50 hr mechanically alloyed (MAed) powder with varied sintering parameters. Detailed microstructural analysis of the consolidated samples revealed that sintering at 1100 °C resulted in improved densification, i.e. up to 99% and enhanced grain growth compared to the samples sintered at lower temperatures. Phase analysis of the sintered HEAs envisaged formation of face centered cubic (FCC) structured single-phase solid solution with minor amount of brittle sigma (σ) phases. Phase diagram generated from Thermo-Calc shows that volume fraction of the σ phases decreases continuously with temperature and further they dissolve at 1180 °C, which is in close agreement with experimental results of differential thermal analysis (DTA) performed on the sintered samples. Moreover, microhardness of the consolidated HEAs decreased gradually with increase in sintering temperature, ascribed to lower volume fraction of the brittle σ phases at higher temperature. Further, nanoindentation test was conducted to estimate the hardness of the individual phases and it was found that nanohardness of σ phase is approximately 1.7 times higher than that of the solid solution phase. The HEA sintered at 1100 °C showed an excellent strength-ductility synergy, with a compressive yield strength of 1121 ± 21 MPa and the elongation to failure up to 20 ± 1%, attributed to the presence of ductile FCC phase with minor amount of brittle σ phase. The present study demonstrates the potential of SPS technique to synthesize Ni base HEA with excellent thermal stability and superior mechanical properties for structural applications.

Kinetic analysis of pyrolysis and thermal oxidation of bitumen

In this study, thermogravimetry (TG) coupled with differential thermal analysis (DTA) was performed to examine the thermal behavior of a straight-run distillation bitumen utilized in a variety of applications, including the conditioning of nuclear waste. The non-isothermal characterization of this bitumen was carried out from 30 to 900 °C with heating rates of 1, 2, 5, 10 and 25 °C/min, in nitrogen and air atmospheres. TG and DTA results showed that under nitrogen atmosphere, pure bitumen shows a single thermal event, which is attributed to its pyrolysis. While under air, it undergoes two exothermic low temperature oxidation stages, one endothermic fuel deposition stage, and one exothermic high temperature oxidation. Kinetic parameters were determined using Kissinger, Friedman and advanced non-linear (NLN) methods to assess activation energy for each event, from the non-isothermal experimental data. Good agreement between kinetic modeling was found for bitumen under nitrogen and air.

Phase diagram of the semiconductor GaSb–ferromagnet GaMn system

In this work we report the results of complex studies of basic properties and phase equilibria in GaSb–GaMn system within wide composition range. Investigated alloys were synthesized using regimes with relatively low crystallization speed, which resulted in a formation of stable monoclinic modification of GaMn, as suggested by the X-ray diffraction data analysis. The latter also suggested the negligible role of mutual solubility of components in agreement with spatial distribution of elements in studied alloys determined using energy dispersive X-ray spectroscopy. Combination of microstructural data and results of differential thermal analysis reveals the eutectic character of interaction in GaSb–GaMn system with eutectic composition corresponding to 45 mol.% of GaMn and melting temperature of 609 °C. This temperature is substantially lower than reported values of peritectic melting temperature of GaMn, which suggests the possibility of stabilizing hard ferromagnetic L10-GaMn modification in GaSb–GaMn system without substantial deterioration of crystal quality typical for GaMn compounds.

Metal Nanoparticles Decorated on Carbon Nanotube Surfaces as Fillers to Improve Thermal Conductivity of Stable Phase Change Composite Materials

The composite phase change materials (CPCM) are prepared by using porous silicon carbide foam as the carrier, N-octadecane (C18) as the phase change material, and metal nanoparticles decorated on carbon nanotube surfaces (M-NPs@CNTs) as fillers. It is a new type of shape and performance stable C18/M-NPs@CNTs/SF CPCM with better performance. The thermal conductivity of the C18/M-NPs/CNT/silicon carbide foam (SF) composite is higher than that of pure C18. When the thermal filler is AgNPs@CNTs, the thermal conductivity of CPCM is improved by 666% compared with C18. The results of thermogravimetric and differential thermal analysis indicate good structural stability and chemical stability. C18/1wt%AgNPs/CNT/SF has the highest thermal conductivity and heat storage capacity, and the best overall performance in the process of thermal energy storage and release. The silver nanoparticles The well-dispersed thermal fillers (M-NPs@CNTs) form excellent heat conduction path and improve the thermal performance of the system. The SF is an excellent thermal conductive carrier materials and its porous structures are attributed to the adsorption of phase change materials and structural stability of CPCM. The application of SF both improves the thermal conductivity and electrical resistivity of CPCM and decreases its leakage during phase change. The application of solid-liquid CPCM can be enlarged in thermal management field.

On the structure of cetylpyridinium perchlorate: A combined XRD, NMR, IR and DFT study

Cetylpyridinium perchlorate has been synthesized and characterized by using the differential thermal analysis (DTA), X-ray powder diffraction (XRD) techniques, Fourier transform infrared spectroscopy (FT-IR), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The investigated salt melts congruently at 100 °C. The DTA and XRD results indicate that the cetylpyridinium perchlorate samples synthesized at different temperatures differ in crystallinity. It has been established that the crystallinity degree of the samples affects the decomposition temperature. The highest decomposition temperature (Td = 265 °C) is observed for the sample crystallized at 20 °C. Cetylpyridinium perchlorate crystallizes in the monoclinic crystal system with the cell parameters a = 20.31 Å, b = 16.20 Å, c = 7.25 Å, β = 95.26°, Z = 4.According to the DFT calculations, the interionic interactions in the structure are characterized by electron transfer from the perchlorate anion to the cetylpyridinium cation. This explains a noticeable difference in the 1H NMR chemical shifts of the hydrogen atoms in the ortho-position (∼0.2 ppm) and the α-methylene group (∼0.1 ppm) of the DMSO solutions of the cetylpyridinium perchlorate and chloride salts micelles. The electronic structure analysis of cetylpyridinium perchlorate and cetylpyridinium chloride in terms of the “quantum theory of atoms-in-molecules” and the analysis of non-covalent interactions with the “reduced density gradient” method have revealed the presence of strong interactions between the ions in the DMSO solution.

Prediction of thermal and thermo‐mechanical behavior of nano‐zirconia reinforced aluminium matrix composites

AbstractAluminium bequeaths the same benefits to medical industry as it does to other industries: it is incredibly lightweight and possesses superior strength‐to‐weight ratio. This study‘s aim is to investigate the thermal and thermomechanical behaviour of aluminium 6061 alloy reinforced with nano zirconia (0 wt. % to 15 wt. %; in 5 % steps) for medical applications. The effect of nano zirconia loading on thermal conductivity and thermo‐mechanical (thermo‐gravimetric analysis and dynamic mechanical analysis) have been systematically investigated. The thermal conductivity (128 W/m⋅K to 79 W/m⋅K) decreases with the increasing of nano zirconia particles reinforcement. The storage modulus increases with the nano zirconia particles (64 GPa to 172 GPa), whereas loss modulus indicates an increasing trend concerning the increasing temperature. The thermogravimetric analysis and differential thermal analysis result shows that composites’ decomposition temperature improved with the weight percentage of nano zirconia particles. Furthermore, representative volume element analysis is conducted to evaluate the thermal conductivity and results indicates good agreement with the experimental results within a deviation of ∼5 %.

Influence of Fe substitution on the stability of Pr3Pt4 compound

ABSTRACT The stability of the phase Pr3Pt4 in a series of Pr42.9Pt57.1-x Fe x (x = 0, 1, 2, 3) alloys was investigated by using X-ray diffraction (XRD) and differential thermal analysis (DTA). It was found that the phase Pr3Pt4 (3:4 phase) with Pu3Pd4-type structure formed in the Pr42.9Pt57.1-x Fe x alloy for x = 0 annealed at 1173 K for two weeks. However, the fraction of the 3:4 phase decreased rapidly with increasing x, and approached zero when x = 3. XRD and DTA results showed that the 3:4 phase decomposes gradually into the two neighboring phases PrPt (1:1 phase) and (Pr, Fe)Pt2 (1:2 phase), and the decomposition temperature of the reaction 3:4 → 1:1 + 1:2 is shifted slightly to higher temperature with increasing x. The reason for this phase decomposition is briefly discussed by the preferential site occupation of Fe in Pr3Pt4.

Structure Determination, Mechanical Properties, Thermal Stability of Co2MoB4 and Fe2MoB4.

The precise determination of atomic position of materials is critical for understanding the relationship between structure and properties, especially for compounds with light elements of boron and single or multiple transition metals. In this work, the single crystal X-ray diffraction is employed to analyze the atomic positions of Co2MoB4 and Fe2MoB4 with a Ta3B4-type structure, and it is found that the lengths of B-B bonds connecting the two zig-zag boron chains are 1.86 Å and 1.87 Å, but previously unreported 1.4 Å. Co and Fe atoms occupy the same crystallographic position in lattice for the doped samples and the valence is close to the metal itself, and Co/Fe K-edge X-ray Absorption Fine Structure(XAFS) spectra of borides with different ratios of Co to Fe are collected to detect the local environment and chemical valence of Co and Fe. Vickers hardness and nano indentation measurements are performed, together with the Density Functional Theory (DFT) calculations. Finally, Co2MoB4 possess better thermal stability than Fe2MoB4 evaluated by Thermogravimetric Differential Thermal Analysis (TG-DTA) results.

Changes in Cement Mass under the Influence of Consciousness Bond Field: A Study of Taheri Consciousness Theory

Taheri Consciousness (T-Consciousness) was introduced and defined by Mohammad Ali Taheri as one of the constituent components of the Cosmos in addition to matter and energy, from which Taheri Consciousness Fields (TCFs) are derived. TCFs are not matter or energy, but they can be proven by scientific experiments. In this regard, extensive research on materials indicates that the occurred changes require energy. As no energy was applied during the experiment, the only reason for these changes was the existence of T-Consciousness. By examining the behavior of cement in various functions, it was found that in many cases, the water absorption of cement was reduced or remained constant while the number of elements had changed. This finding raised the possibility of a change in the mass of the matter. This study investigated the volume and mass of 9 identical cement samples up to 28 days old. It was found that water absorption under T-Consciousness Field was still lower (-2.8%, -2.6%), the mass of the samples increased (3 to 4%), and the percentage of crystalline phase was higher in the samples under the Field. TGA (Thermal gravimetric analysis), DTA (Differential thermal analysis), and DSC (Differential scanning calorimetry) analysis results were consistent with XRF (X-Ray Fluorescence) and XRD (X-ray Diffraction).

Synthesis and characterization of Dy–Eu–Tm co-doped cubic phase stabilized bismuth oxide based electrolytes in terms of intermediate temperature-solid oxide fuel cells (IT-SOFCs)

In this study, a new Dy–Eu–Tm co-doped cubic phase stabilized bismuth oxide solid electrolyte system was synthesized by using solid-state reaction method in atmospheric conditions. Before conductivity measurements, X-ray diffraction (XRD) profiles of the annealed samples show that created mixtures have heterogeneous phase, but after conductivity measurements, the face-centered cubic (FCC) crystal structure is stabilized for all samples. Also, the increase in total dopant rate causes an increase in full width half maxima (FWHM) of main peak (111) on the XRD pattern while average crystal size decreases with it. On the other hand, the highest conductivity value was obtained for the sample having 15% total dopant rate with 0.62 S/cm at 750 °C, whose dopants are evenly distributed in mole percent. Differential thermal analysis (DTA) results of the samples having 1:1:1 and 1:2:1 dopant content ratios show that endothermic peak occurs on their DTA curve, indicating crystal structure transformation such as phase transition or order–disorder transition. Also, thermo–gravimetric analysis (TGA) depending on temperature was evaluated in terms of mass loss. According to TGA curves, mass loss for both heating and cooling process can be negligible due to the small fluctuations (2%) on their TGA curves.

Polymorphism of the Tb2Ni7 binary compound solubility of lithium and magnesium in α-phase

The solubility of lithium and magnesium in the binary intermetallic compound Tb 2 Ni 7 and its polymorphism were investigated by X-ray powder diffraction, X-ray fluorescent spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The alloys for investigation were synthesized by arc melting of pure components taken in stoichiometric composition with the exception of Li and Mg which were taken in excess of 5 wt. % under purified argon atmosphere and further annealing at 400 °C for two months in sealed evacuated silica tubes. Morphology of the alloys surfaces was studied using scanning electron microscope TESCAN Vega3 LMU. Quantitative compositions of the powders were established using Oxford Instruments energy-dispersive X-ray analyser (Aztec ONE system). X-ray fluorescent spectroscopy (spectrometer ElvaX Pro) was used for investigation of the integral composition of the alloys. X-ray phase analysis was carried out on powder data obtained on diffractometer DRON-2.0M (Fe K α -radiation). We confirmed that the Tb 2 Ni 7 binary compound exists in two polymorphic modifications: low-temperature α -Tb 2 Ni 7 (structure type Ce 2 Ni 7 , space group P 6 3 / mmc ) and high-temperature β -Tb 2 Ni 7 (structure type Gd 2 Co 7 , space group R -3 m ). The phase transition α -Tb 2 Ni 7 &lt;=&gt; β -Tb 2 Ni 7 according to the results of differential thermal analysis occurs at 931 °C. The solubility of lithium and magnesium is observed in both modifications however it is larger in α -phase. Substitution of Ni-atoms by the statistical mixture of Li and Mg in α -Tb 2 Ni 7 and formation of the solid solution α -Tb 2 Ni 7- 2 х Li х Mg x ( х = 0–0.5) causes an increase of the unit cell parameters. This solid solution is in equilibrium with the CaCu 5 -type (space group P 6/ mmm ) and PuNi 3 -type (space group R -3 m ) phases. Keywords: polymorphism, solid solution, X-ray diffraction, energy-dispersive X-ray spectroscopy.

THE NUCLEATION EFFECT OF PbSe ADDITIVE ON Bi2Sr2CaCu2Oδ GLASS CERAMICS

The crystallisation kinetics and effects of doping on Bi2Sr2CaCu2Oδ (BSCCO) glass ceramic system with 0.0, 0.1, 0.3 and 0.5 % PbSe were investigated in this study. Using differential thermal analysis (DTA), the effects of PbSe doping on glass transition, nucleation and crystallisation temperature of glass were investigated. The DTA results were analysed using the Ozawa, Augis–Bennett, Takhor and Kissinger equations for nucleation kinetics to uncover the activation energies and Avrami parameters. Thermogravimetric analysis revealed that the amount of oxidation in the structure increased with increasing PbSe-doping concentration.