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The phase transitions in the homologous series of normal alkanes: hexadecane (C16H34), heptadekane (C17H36), octadekane (C18H38), nonadekane (C19H40), and eicosane (C20H42) have been studied by differential scanning calorimetry. The elimination of methodic errors enables the obtainment of true values of the thermodynamic parameters of these transitions. The quantitative analysis of the profiles of the heat capacity jumps performed for the solid-phase first-order transitions on the base of the blurred phase transition theory allowed the calculation of a new-phase nucleus sizes in the volume of the old phase during the structural phase transition and the consideration of the kinetics of their development. The method of separating asymmetric peaks of the heat capacity into components has been improved, which enables the separation of various stages of developing the solid-phase transitions.

The effect of gamma irradiation and doping with silicon dioxide on the first-order solid-state phase transition in polytetrafluoroethylene is studied by the differential scanning calorimetry method. A quantitative analysis of the profiles of the heat capacity peaks is carried out on the basis of the theory of diffuse phase transitions. It is shown that the elementary volume of the phase transformation depends on the γ irradiation and the concentration of silicon dioxide.

We show how the combined use of the methods of Rutherford backscattering of ions and X-ray fluorescence analysis under conditions of total external reflection of the flow of exciting hard X-ray radiation and registration of the X-ray radiation output during ion excitation allows to effectively diagnose the elemental composition of thin-film coatings and films of dry residues of liquids. These methods and the features of their experimental application are briefly described. Examples of the complex methodological analysis of real objects are given. The possibility of increasing the efficiency of the methods of X-ray fluorescence analysis of materials due to the inclusion in the X-ray optical schemes of experimental measurements of flat X-ray waveguide resonators is indicated.

We analyze heat effects associated with the solid-state phase transition in ultrahigh molecular weight polyethylene from the unstable monoclinic phase into thermodynamically stable orthorhombic phase. The model proposed here for the structure of supramolecular formations of monoclinic phase does not contradict to earlier X-ray diffraction data for this polymer.

We perform a comparative study of melting of polytetrafluoroethylene (PTFE) in its unmodified form, after irradiation, and after adding plant-derived silicon dioxide as an additive (content, 1%). Calculation of peak shapes on thermal capacity profiles within the theory of smeared phase transitions enable us to identify the structural changes and their features resulting from irradiation of PTFE and incorporation of the additive in it. α-relaxation at the glass transition in our samples is studied by dynamic mechanical analysis.

Comparative analysis of phase and relaxation transitions in poly(tetrafluoroethylene) by differential scanning calorimetry and dynamic mechanical analysis has been carried out. Elimination of procedural errors in the first case has allowed us to obtain true values of thermodynamic parameters for phase transitions and reveal their nature. Quantitative analysis of heat capacity peak profile was performed on the basis of smeared first-order phase transition theory and relaxation glass transition has been characterized.

The effect of additives of 1 and 3 wt % of halloysite on the rate and small jumps of deformation under uniaxial compression of ultrahigh-molecular-weight polyethylene was investigated. A procedure for precision interference measurement with a resolution of 325 nm for displacement and 1 kHz for frequency enabled the detection of several levels of deformation in the micro- and nanometer ranges. The addition of halloysite results in a decrease in the strain rate under the same loading conditions and a change in the characteristics of the strain jumps. Calorimetric measurements showed that melting of polyethylene with a different concentration of halloysite causes a change in the transition energy and the degree of crystallinity.

We analyze the dependency of melting points of molecular crystals with different chain lengths on the crystal habit of elementary volume for the first-order phase transition. We demonstrate that molecular crystals with identical chemical structure of their cores—unbranched alkanes CH3(CH2)nCH3, diols HOC(CH2)nCOH, unbranched aliphatic alcohols CH3(CH2)nCOH, saturated carboxylic acids CH3(CH2)nCOOH, and dicarboxylic acids HOOC(CH2)nCOOH—lose their identity and individual properties and evolve toward polyethylene as the number of repeating–CH2–groups increases.

The effect of solid-state phase transitions on the kinetic parameters of creep deformation in polytetrafluoroethylene has been studied by differential scanning calorimetry and a laser-interferometric creep rate meter. It has been shown that the deformation activation volumes and the elementary phase transition volume differ from each other by more than an order of magnitude. The crystalline component of this polymer becomes a liquid-crystal phase coexisting with an amorphous phase.

Phase transitions in normal alkanes, such as tricosane (C23H48), tetracosane (C24H50), and pentacosane (C25H52), were studied by differential scanning calorimetry. The elimination of some procedural errors provided the possibility to obtain true values for the thermodynamic parameters of phase transitions and ascertain their nature. The comparative analysis of heat capacity jumps was performed on the basis of the theory of diffuse first-order phase transitions.

Thermal effects in some nanoporous silicate matrices (with different pore sizes) loaded with ferroelectric NaNO2 from both a saturated solution and from a melt have been studied in a wide temperature range including the phase transition temperatures. All the samples reliably demonstrate maxima of the heat capacity, corresponding to first-order ferroelectric phase transitions. The characteristics of the maxima (intensity, half-width, phase transition temperature, etc.) have been determined. A more complex situation is the observation of an incommensurable phase (sinusoidal antiferroelectric), in particular, in the case of pore sizes comparable to the period of an “incommensurable” wave, the manifestation of which can be explained by the appearance of a corresponding orientation of sodium nitrite nanocrystals in pores of these matrices. It is found that the characteristics of above noted effects depend on the prehistory of the samples under study.

Silicon carbide samples synthesized from silicon by topochemical substitution of atoms are studied by the ion channeling method. The results of the analysis unambiguously demonstrate the occurrence of structural heteroepitaxy. The lattice of synthesized silicon carbide of hexagonal polytype 6H is epitaxially matched in the 〈0001〉 direction with the lattice grating grid array network of an initial substrate silicon in the 〈111〉 direction. The main features of structural self-coupling matching in this epitaxial heterocomposite are revealed. Despite the very large silicon carbide and silicon lattice parameter mismatch, the misfit dislocation density at the interface is low, which is a feature of the topochemical substitution method leading to comparable structures.

Comparative analysis of phase transition in normal paraffins, heneicosane (C21H44) and docosane (C22H46), was performed using differential scanning calorimetry. Elimination of methodical inaccuracies allowed obtaining proper values of the thermodynamic parameters of the phase transitions and revealing their nature. Quantitative analysis of the heat capacity steps was made based on the theory of blurred first-order phase transitions and Landau’s theory for second-order phase transitions.

The quantitative analysis of the temperature dependence of the heat capacity of molecular crystals with chains of different lengths was performed using the theory of diffuse first-order phase transitions. The same chemical structure of the “core” of molecular crystals of {CH3(CH2)nCH3} normal paraffins, {COH(CH2)nCOH} diols, {CH3(CH2)nCOH} normal alcohols, and {CH3(CH2)nCOOH} saturated carboxylic and {COOH(CH2)nCOOH} dicarboxylic acids enabled the comparative analysis of phase transition parameters.

Xerogel reactor powders and supramolecular polyethylene fibers with various degrees of hood have been studied via differential scanning calorimetry. A higher strength of laboratory fibers in comparison with industrial ones is found to be achieved due to a multistage band high-temperature hood that causes the thermodynamic parameters of supramolecular polymer structure.

The dependence of the crystallization temperature of bismuth microparticles on their size has been measured using calorimetry. It has been shown that, for particles with radii of more than 10 µm, this dependence can be approximated by the logarithmic function. The crystallization temperatures at the ends of the studied range of particle sizes agree satisfactorily with the data available in the literature.

The influence of preliminary incomplete shape memory (SM) deformation on the generation of reactive stresses in single crystals of the Cu-13.6 wt % Al-4.0 wt % Ni alloy under conditions of constrained SM deformation has been studied. It has been found that, with an increase in the deformation, the value of reactive stresses increases linearly with increasing stress of preliminary deformation of the alloy.

A comparative analysis of phase transitions in molecular crystals of saturated dicarboxylic acids with {COOH(CH2) n COOH} chains of different lengths has been performed by differential scanning calorimetry, which revealed a number of new effects related with specific features of the phase transitions. A quantitative analysis of temperature dependence of the heat capacity has been carried out in the context of the theory of smeared (Λ-shaped) first-order phase transitions.

It has been shown that the phase transitions observed at temperatures of about 250 K in crystals of protein amino acids and of their compounds grown from water solutions are related to drops of these solutions trapped by crystals in their growth.

The structure and thermal properties of polycrystalline samples of samarium monosulfide have been investigated in the homogeneity region (Sm1 + xS at 0 < x < 0.17). The X-ray structural parameters and porosity of the samples have been measured, and their correlation with the thermodynamic parameters of the first-order phase transition occurring in polycrystalline samarium monosulfide at temperatures in the range from 240 to 260 K in Sm1 + xS has been established. It has been assumed that the measured nanopores correspond to voids between misoriented coherent X-ray scattering regions. It has been shown that the maximum of the absorbed heat energy is achieved in the case where the volume of the pore becomes comparable to the volume of the nucleus of a new phase of samarium sulfide, which is calculated from thermodynamic relationships.

The effect of heat absorption has been found for powder samples of samarium sulfide (SmS) in a temperature range of 235–250 K. The comparison with a similar effect in single-crystal SmS has been performed and thermodynamic parameters of the process have been determined. It has been shown that the collective injection of electrons into the conduction band from impurity donor levels is responsible for the appearance of this effect in both cases. The shift of the endothermic peak upon powdering toward lower temperatures and an increase in the enthalpy are associated with a decrease in the characteristic size of the X-ray coherent scattering regions and, as a consequence, with an increase in the concentration of impurity donor levels.

The heat of the β′1-β1-martensitic transition in single crystals of the alloy Cu-13.5 wt % Al-4.0 wt % Ni was studied under conditions of a constrained shape memory deformation and emergence of reactive stresses. The experiments were performed with samples bended in the form of a clamp. The sample was put into a continuous stainless steel ring, and this construction was placed in the capsule of a differential calorimeter. It was found that, with an increase in the magnitude of preliminary bend deformation, the maximum in the heat release (or heat absorption) curves decreases noticeably and its position shifts to higher temperatures. It was revealed that the latent heat of the transition decreases by a factor of 2 and 3 during heating and cooling, respectively. It was assumed that the observed effects are related to the influence of reactive stresses on the parameters of martensitic transitions. A quantitative analysis of the data obtained was performed in terms of the theory of diffuse martensitic transitions taking into account both the thermodynamic and kinetic factors.

A comparative analysis of the phase transitions in molecular crystals of diols with different chain lengths [1,15-pentadecanediol (CH2)14(OH)2 and 1,16-hexadecanediol (CH2)15(OH)2] has been performed using differential scanning calorimetry. A quantitative analysis of the temperature dependence of the heat capacity within the theory of diffuse (Λ-shaped) first-order phase transitions and the use of the temperature hysteresis have revealed a number of new effects associated with the specific features of the phase transitions in molecular crystals of diols.

New members of the family of inorganic solid-state protonic conductors are synthesized on the basis of KOH, NaOH, and H2O. The equimolar eutectics KOH/NaOH and KOH/KOH · H2O and the monohydrate KOH · H2O are superprotonic conductors in the temperature ranges 360–458, 360–370, and 320–420 K, respectively, with the conductivities of above 1 mS/cm and activation energies below 0.4 eV. A characteristic feature of the eutectics is the presence of anomalies in the temperature dependences of the conductivity and heat capacity in the range 360 ± 1 K. The isotopic effect of the protonic conductivity for KOH · H2O and for the high-temperature form of KOH/NaOH is found to be 1.40 ± 0.15. The role played by the self-organized microheterogeneity of the KOH/NaOH and KOH/KOH · H2O solid eutectics in the substantial increase in the conductivity and in the change of its pattern as compared to the individual KOH and NaOH is discussed.

The effect of copper doping on charge-orbital ordering in La1/3Ca2/3Mn1 − yCuyO3 (0 ≤ y ≤ 0.07) is studied by measuring the temperature dependences of the magnetization, the electrical resistivity, and the heat capacity in combination with an electron microscopic investigation of the structure. It is demonstrated that copper doping leads to a lowering of the charge ordering temperature TCO and that this decrease is proportional to the decrease in the Mn3+ ion concentration. In the temperature range 5–300 K, the semiconducting pattern of the electrical resistivity persists for all values of 0 ≤ y ≤ 0.07. Electron microscope studies have shown that the presence of copper suppresses the formation of a regular superstructure, which is characteristic of the undoped starting compound, beginning already from low concentrations (y = 0.01). Differential scanning calorimetry revealed a substantial decrease in the transition entropy at the onset of charge ordering in copper-doped samples as compared to the starting compound. Doping with copper destroys long-range charge-orbital ordering and retains apparently only short-range order.

A comparative analysis of the phase transitions in molecular crystals of n-alkane alcohols with different lengths of the (CnH2n + 2OH) chain was performed using differential scanning calorimetry (DSC). Investigation of the temperature hysteresis made it possible to reveal a number of new effects associated with the specific features of the first-order phase transitions. A quantitative analysis of the temperature dependence of the heat capacity was carried out in the framework of the theory of diffuse (Λ-shaped) first-order phase transitions.

Phase transitions in ceramic samples of (1 − x)BaTiO3-xBa(Mg1/3Nb2/3)O3 solid solutions were studied by differential scanning calorimetry for x = 0, 0.01, 0.02, and 0.03 in the temperature ranges 255–290 K and 310–410 K. The experimental data obtained were used to derive the thermodynamic parameters of the phase transitions occurring at T c ≈ 400−300 K and T 1 ≈ 290−300 K and construct the concentration phase diagram.

Differential scanning calorimetry (DSC) was used under the highest resolution conditions to study the phase transition in diserine sulfate monohydrate crystals. In the temperature range 255–270 K, the DSC signal was found to exhibit sharp Λ-shaped peaks with a thermal hysteresis of 8.5 K, which indicates the occurrence of a first-order phase transition. The experimental data are used to determine the thermodynamic parameters of the phase transition.

Oxygen-deficient La0.67Sr0.33MnO3−α solid solutions have been studied. A comparison is made with the results obtained in an earlier study of a similar lanthanum-calcium manganite series. The physical characteristics of both series are accounted for as being due to a change in the Mn3+/Mn4+ ratio caused by oxygen removal. The differences between the strontium and calcium series originate from differences in both the bulk properties of the original oxygen-stoichiometric materials and their texture. In the strontium series, the texture manifests itself in intergrain magnetoresistance, which exceeds in magnitude the colossal magnetoresistance caused by bulk properties of the material. Study of the oxygen-deficient La0.67Sr0.33MnO3−α compound revealed specific features in the dependence of the electrophysical parameters on temperature and the Mn4+ fractional content that were not observed in the La0.67Ca0.33MnO3−α compound studied by us earlier and in La1−x SrxMnO3 samples described in the literature. The physics underlying these differences is discussed. A modified phase diagram relating the phase transition temperature to the Mn4+ fraction is proposed.

The optical and structural properties of multilayer Si/Ge structures with precritical, as well as close-to-critical, germanium inclusions in a silicon matrix, for which the transition from the two-dimensional to island growth occurs, were studied. The possibility of obtaining intense photoluminescence at room temperature in both cases under optimally chosen growth parameters is demonstrated. The proposed approaches to producing an active region appear promising for applications in silicon-based optoelectronics.

The morphological nature of discontinuous (jumplike) deformation is studied. Recording creep behavior of materials using a laser interferometer permits one to determine the parameters of deformation jumps on a micron scale. The objects of investigation were poly(dimethylsiloxane) (PDMS) and a composite material consisting of PDMS and quartz (SiO2). It is shown that the height and sharpness of jumps depend on the composition of the material and the stage of deformation. An analysis of differential scanning calorimetry (DSC) curves of the materials in the deformed and initial states suggests that deformation results in ordered domains in rubberlike polymers. This confirms the assumption that deformation jumps reflect the presence and the evolution of structural inhomogeneities in amorphous polymers.

This paper reports on a first study of the effect of oxygen content in La0.67Ca0.33MnO3−α on the electrical conductivity, magnetoresistance, and specific heat within a broad range of oxygen deficiency variation, 0≤α 0.006. The effects of a variation in the cation composition and the oxygen content on the physical properties are compared.

The thermodynamic transition in the C60 crystals subjected to uniaxial compression at different temperatures and heat treatment has been investigated by differential scanning calorimetry (DSC). The kinetic parameters of the irreversible endothermic “quenching” effect are determined. It is revealed that the process is accompanied by the cooperative molecular motion, which is characteristic of the high-elasticity state of organic glasses.

The temperature spectrum of small-inelastic-strain rates in a vapor-phase-grown C60 single crystal has been measured within the 200–290 K interval with a high-precision strain-rate meter based on a laser interferometer. The spectrum exhibits a strong peak in the region of the phase transition at 250–260 K and a slight strain acceleration at ∼240 K, which correlates well with the calorimetric curve. The first maximum is associated with strain that developes more easily in an fcc than in a primitive cubic lattice, and the second, to the effect on the strain rate of annealing of the defects created with fast crystal heating.

A comparative study of the thermodynamic properties of the C70 fullerene, sulfur, and C70S48 crystals has been made by differential scanning calorimetry. It is shown that only C70S48 has an endothermic δ phase transition with a peak at 430 K, which lies in the temperature region exhibiting conductivity and dielectric anomalies. A correlation between the behavior of the sulfur sublattice in the C70S48 crystals and the thermodynamic parameters of the transition has been established.

Differential scanning calorimetry was used to study phase transitions (PT) in the perovskite BaCeO3. It is shown that its phase state is determined by a second-order λ transition at Ttr=520–540 K and a first-order δ transition at Ttr=600–670 K. Differences in PT parameters between ceramic and fused BaCeO3 have been established.

The electrical conductivity of ceramic samples with a general formula HxBa2YCu3O7+z has been measured in the course of hydrogenation (formation of the hydrocuprate) and subsequent oxidation (formation of the oxyhydrocuprate). The hydrocuprate (x>0, −0.1

The rate spectrum of small inelastic strains of the C60 single crystal in the temperature range 80–300 K has been obtained with a precision laser interferometer. It is revealed that the spectrum exhibits two large peaks in the glass formation (90–100 K) and phase transition (250–260 K) ranges. A small strain acceleration is also observed at ∼220 and 240 K. The first two maxima are attributed to the changes in strain resistance upon transitions, and the strain acceleration at 220 and 240 K is associated with the annealing of the defects formed upon rapid cooling of the crystal. It is demonstrated that the peak at 250–260 K broadens with an increase in the stress. The spectrum of strain rates is compared with the calorimetric curve for the same single crystal.

A thermodynamic transition in C60 crystals, subjected beforehand to uniaxial compression at various temperatures and to thermal action, was investigated by differential scanning calorimetry. It was established that compression of the crystal at temperatures below the phase transition has a much smaller effect on the transition itself than a similar or even much weaker action at a temperature above the phase transition. A “quenching” effect was also found. This effect is probably due to the orientational order of individual fullerene molecules. A correlation was established between the magnitude of the effect and the preliminary deformation of C60 crystals.

We have observed diamagnetic domains (Condon domains) in a beryllium single crystal in magnetic fields H⩽3 T (H∥[0001]) at liquid-helium temperatures. The formation of the domain structure was determined according to magnetic-breakdown quantum oscillations of the resistance thermoelectric power as well as according to the splitting of the resonance peak of the free spin precession frequency of muons (µSR). The alternation of a uniform state (with one µSR peak) and a state with domain structure (with two peaks) is consistent as regards the periodicity with the de Haas-van Alphen effect, the period is ΔH≅78 Oe, and the range of existence of domains and the difference in their magnetizations are ΔB=4πΔM=B2−B1≅30 Oe.

The effect of heat absorption is revealed in the temperature range where the thermovoltaic effect occurs in single-crystal samarium sulfide (SmS). It is shown that the heat absorption is caused by the collective injection of electrons from donor levels into the conduction band.

An orientational phase transition in C60 crystals was studied by differential scanning calorimetry with the highest resolution provided by this method. The temperature dependence of the specific heat ΔCp(T) was found to have a double peak in the range 250–270 K. An analysis of the temperature dependences of heat capacity in the region of the peaks revealed that the lower temperature peak follows a power law of the type ΔCp = A/(T−T0)1/2 characteristic of order-disorder second-order phase transitions, while the high-temperature peak can be identified with a diffuse Λ-shaped first-order phase transition.