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The simplest model of the structure and interatomic interaction is applied to hydrogen solutions in liquid alloys of Fe – Ni system, which earlier (2019 – 2021) was used by the authors for nitrogen solutions in alloys of Fe – Cr, Fe – Mn, Fe – Ni, Ni – Co and Ni – Cr systems. The theory is based on lattice model of the Fe – Ni solutions. The model assumes a FCC lattice. In the sites of this lattice are the atoms of Fe and Ni. Hydrogen atoms are located in octahedral interstices. The hydrogen atom interacts only with the metal atoms located in the lattice sites neighboring to it. This interaction is pairwise. It is assumed that the energy of this interaction depends neither on the alloy composition nor on the temperature. For simplicity it was assumed that liquid solutions in the Fe – Ni system are perfect. Within the framework of the proposed theory an expression is presented for the Wagner coefficient of interaction between hydrogen and nickel in liquid steel. The right-hand part of the appropriate formula is a function of the ratio of the Sieverts law constants for hydrogen solubility in liquid iron and in liquid nickel. The values of these constants for a temperature of 1873 K are taken equal to K′H(Fe) = 0,0025, K′H(Ni) = 0,0040 wt. %. At the same time, an estimate was obtained for the Wagner coefficient of interaction between hydrogen and nickel in liquid steel εHNi = –0,54. This corresponds to the value of the Langenberg interaction coefficient eHNi = –0,002, wich is very close to the experimental estimate eHNi = –0,0022.

A simple theory of thermodynamic properties of liquid nitrogen solution in Fe–Mn alloys is proposed. This theory is completely analogous to the theory for liquid nitrogen solution in alloys of the Fe–Cr system proposed previously by the authors in 2019. The theory is based on the lattice model of the considered Fe–Mn solutions. The model assumes a FCC lattice. The atoms of Fe and Mn are in these lattice sites. Nitrogen atoms are located in octahedral interstices. The nitrogen atom interacts only with the metal atoms located in the lattice sites neighboring to it. This interaction is pairwise and it is assumed that the energy of this interaction depends neither on the composition nor on the temperature. Furthermore, the solution in the Fe–Mn system is assumed to be perfect. Within the framework of the proposed theory, a relation was obtained that expresses the value of the Sieverts law constant for N solubility in liquid Mn through the similar constant for the N solubility in liquid Fe and the Wagner N–Mn interaction coefficient in liquid Fe. The values of the Sieverts law constants in this relation are taken directly from the experimental measurements of the solubility of N in liquid Fe and in liquid Mn. In this case, the obtained relation is considered as an equation with respect to the Wagner interaction coefficient $$\varepsilon _{{\text{N}}}^{{{\text{Mn}}}}$$ . The equation’s solution gives the value of Wagner interaction coefficient $$\varepsilon _{{\text{N}}}^{{{\text{Mn}}}}$$ = –5.25 in liquid steel at a temperature of 1873 K. Wagner interaction coefficient $$\varepsilon _{{\text{N}}}^{{{\text{Mn}}}}$$ is related with Langenberg interaction coefficient $$e_{{\text{N}}}^{{{\text{Mn}}}}$$ by the relation deduced by Lupis and Elliott in 1965. The relation includes the atomic masses of Fe and Mn. By substituting the value $$\varepsilon _{{\text{N}}}^{{{\text{Mn}}}}$$ = –5.25 and solving the resulting equation with respect to $$e_{{\text{N}}}^{{{\text{Mn}}}}$$ , we obtain the value $$e_{{\text{N}}}^{{{\text{Mn}}}}$$ = –0.0230. This value corresponds to the experimental data of Beer (1961), which is likely one of the most probable of all experimental values of $$e_{{\text{N}}}^{{{\text{Mn}}}}$$ for liquid steel at 1873 K. Another such value is $$e_{{\text{N}}}^{{{\text{Mn}}}}$$ = 0.0209 obtained by Shin with coworkers in 2011.

Ceramic in the system Ca2P2O7–Ca(PO3)2 was obtained by firing cement stone fabricated from a powder mixture which included β-tricalcium phosphate β-Ca3(PO4)2 and monocalcium phosphate monohydrate Ca(H2PO4)2 ∙ H2O. The molar ratio Ca/P of the initial powder mixtures was set as Ca/P ≤ 1. X-ray phase analysis shows all ceramic samples after firing at 1000°C to include β-calcium pyrophosphate β-Ca2P2O7, and a sample of the ceramic made from a powder mixture with the maximum content of monocalcium phosphate monohydrate Ca(H2PO4)2 ∙ H2O also contained β-calcium polyphosphate β-Ca(PO3)2. The obtained calcium phosphate ceramic with reduced firing temperature can be used to develop a resorbable matrix for tissue engineering structures.

The article considers basic expansion of thermodynamics and thermodynamic interaction coefficients of the first, second and third orders of low-concentrated binary alloys. The values of interaction coefficients of the first and second orders in 37 such systems were estimated according to experimental thermodynamic data on the concentration dependence of excess chemical potential of an impurity in liquid alloys of binary systems. Estimates were obtained by the numerical differentiation method. This method is based on Newton first interpolation formula. Calculation formulas for the corresponding estimates are given. A simple theory is proposed that relates the thermodynamic interaction coefficient of the second order with the first-order one in the liquid alloy of certain system. The theory is based on the lattice model of a solution and the principles of statistical mechanics. The FCC lattice is adopted as a model lattice. The model of pair interaction between metal atoms in the alloy was used. The radius of this interaction corresponds to radius of the nearest atomic shell. Using the proposed theory, thermodynamic interaction coefficients of the second-order for all 37 systems considered in this work, as well as the values of the third order interaction coefficients for 23 systems out of 37 mentioned above, were calculated. For these 23 systems, theoretical estimates of the second-order interaction coefficients are in agreement with experimental ones both by sign and by order of magnitude. This circumstance can be considered as evidence of applicability of the numerical differentiation method for estimation of thermodynamic interaction coefficients of the first and second orders in liquid binary alloys. The accuracy of estimating the values of the third derivative by numerical differentiation is insufficient. That makes it impossible to compare the calculated values of the interaction coefficients of the third order with the experimental ones, obtained by this method. It can be assumed that the theoretical calculations just give an idea of the magnitudes’ order of these coefficients.

A simple theory is proposed for the thermodynamic properties of nitrogen solutions in Fe–Cr melts. The theory is based on a lattice model of the solution. An fcc model lattice is adopted. Iron and chromium atoms are distributed at the lattice sites. Nitrogen atoms are located in octahedral interstices. The nitrogen atoms only interact with metal atoms at neighboring lattice sites. The energy of this interaction is assumed to depend neither on the composition nor on the temperature. The liquid Fe–Cr solutions are assumed perfect. Within this framework, the constant in the Sieverts law governing the solubility of nitrogen in liquid chromium may be expressed in terms of its value for the solubility of nitrogen in liquid iron and the value of the Wagner parameter for N–Cr interaction in liquid iron alloys. In addition, the partial enthalpy of solution of nitrogen in liquid chromium at infinite dilution is expressed in terms of the corresponding enthalpy for the solution of nitrogen in liquid iron and the Wagner parameter for N–Cr interaction in liquid iron alloys. A relation is also established between the Wagner parameter for N–Fe interaction in liquid chromium alloys and the Wagner parameter for N–Cr interaction in liquid iron alloys. On that basis, the constant in the Sieverts law governing the solubility of nitrogen in liquid chromium is calculated, along with enthalpy of solution of nitrogen in liquid chromium at infinite dilution and the Wagner parameter for N‒Fe interaction in liquid chromium alloys at 1873 K. The calculation results are compared with experimental data regarding the solubility of nitrogen in liquid chromium and Cr–Fe alloys obtained by various methods. The theoretical data are in best agreement with experimental data obtained by quenching. The values of the Wagner parameter for N–N interaction in liquid chromium alloys and iron alloys are discussed.

The feasibility of using the diffraction peaks in x-ray emission spectra detected with energy dispersion for measuring the spacing between lattice planes in crystalline substances is demonstrated.

Thermodynamic parameters of the first order (Wagner interaction parameter e2(2), enthalpy, and entropy parameter σ2(2)) in low-concentration liquid binary alloys are considered. The values of these parameters for 32 binary systems are estimated from experimental data. A system of classification is proposed for the obtained data. These data are compared to similar data for aqueous solutions of nonelectrolytes. A qualitative explanation of the obtained differences is given.

The thermodynamic parameters of interaction and the enthalpy parameters are of fundamental importance in the theory of solutions, i.e., the coefficients of the expansion of partial excess thermodynamic functions into series in terms of the concentrations of the dissolved components. In the approximation of pairwise interactions between the impurity atoms in the solution, the above parameters can be computed using the methods of the density-functional theory in the electron theory of alloys. As an example, the substitutional solid solutions of Au in Ag have been chosen, which are formed by atoms of the components with close chemical properties, in which the deformation interactions should be small, and in which there is no need to take into account the complex magnetic contributions to the pair potentials. The total energy of the dilute solution of Au in Ag and the contributions from the chemical and strain-induced interactions to the potentials of pairwise interactions are calculated up to the seventh coordination shell. Quite satisfactory agreement with the thermodynamic parameters obtained from the experimental data has been obtained.

Biphase ceramic containing hydroxyapatite Ca10(PO4)6(OH)2 and -tricalcium phosphate -Ca3(PO4)2 has been obtained from a uniform nanocrystalline calcium phosphate powder with the structure of apatite, synthesized from water solutions of calcium apatite and ammonium hydrophosphate with molar ratio CaP = 1.5 at room temperature without pH regulation. After firing at 1100°C the material contained 75% -Ca3(PO4)2 and the grain size did not exceed 600 nm. It is suggested that the carbon formed in the interval 200 – 500°C, as a result of the carbonization of the organic components of synthesis adsorbed by particles of powder, be used as a physical barrier impeding intense mass transfer up to 800°C, which makes it possible to obtain an ultradisperse ceramic with grains smaller than 1 m.

An investigation is made into the basic parameters of a coplanar line used to excite helicon-type waves. The components of the electric and magnetic field vectors, the Poynting vector, and .the characteristic impedance are determined. The possibility of using a coplanar line to excite helicon-type waves is studied.

The properties of hydroxyapatite powder synthesized from calcium acetate and potassium hydrophosphate and hydroxide were investigated. The associated reaction product (ARP), whose basic component is potassium acetate, modifies the surface of the hydroxyapatite nanocrystals. The components of the ARP can play the role of a salt matrix by preventing coalescence of nanocrystallites and can also serve as a source for a sintering additive which is uniformly distributed due to adsorption during synthesis. A ceramic based on hydroxyapatite with a uniform microstructure and a maximum grain size of 300 nm was obtained by incorporation of sintering additives in the form of ARP at a temperature of 700°C. The ARP is the cause of different solid-phase processes and processes involving the liquid phase. The sites where these processes occur are the boundaries of the grains, which also restrains their growth.

A study is made of the volt-ampere, volt-farad, and spectral characteristics of photodetectors based on an n-GaAs/p-CuPc heterojunction. When exposed to white light (E=600 W/m2) through Ag, the elements Cu/GaAs/CuPc/Ag have the following characteristics: Uxx=0.6 V; Isc=30.2 A/m2, FF=0.49. Based on this data and with allowance for the transmission factor (τ=7%), η=18%. Quantum efficiency is 0.5 el./phot. in the UV-region at λ1 = 300 nm, while α2 = 0.85 el./phot. in the visible region at λ2 = 800 nm. The limiting sensitivity of the photodetector is 10−11 W. The following was determined from the volt-farad and spectral characteristics: Cb=8.6·10−4 F/m2; barrier width w1=16nm in CuPc and w2=34 nm in CaAs; exciton diffusion length L1=2.5 nm and L2=7.5 nm, respectively. The photodetectors undergo almost no degradation. The values of Uxx and Isc remain constant with multiple exposures to UV-light of 140 W/m2 intensity over 6 h at constant temperature. The sensitivity region of the photodetectors is from 200 to 1000 nm. It is found that an anisotropic heterojunction in the form of two series-connected Schottky barriers is created at the boundary between n-GaAs and oxygen-doped p-CuPc in the presence of charged surface states at the interface.

Calcium hydroxyapatite (HAP) powder was synthesized from a water solution of potassium hydrophosphate and a suspension of calcium hydroxide in a water solution containing calcium and potassium ions, hydroxide ions, and acetate ions. The Ca(OH)2 amount in the calcium containing component was 50, 75, and 100%. The HAP powder synthesized was used to produce ceramic. After kilning at 700°C the density of the ceramic obtained from the HAP powder containing a by-product of the reaction was 2.9 – 2.6 g/cm3 and bending strength 35 – 45 MPa with grain size 200 nm. The phase composition was represented by HAP and calciumpotassium double orthophosphate. After kilning at 1200°C the density of the HAP-based ceramic made from powder with no by-product of the reaction was 2.2 – 2.3 g/cm3 and the bending strength was 45 – 55 MPa with grain size 500 – 1000 nm.