The paper focuses on material characterization and technology properties of a new Ti-12Al-42Nb spherical powder alloy for additive manufacturing of personal medical implants. The electrode induction melting inert gas atomization (EIGA) method was used to produce the powder alloy. The powder sphericity coefficient (PSC) was 1.02. Image J software was used to calculate the spherical degree by processing images sets from scanning electron microscopy (SEM) and optical microscopy (OM). SEM of particles cross-sections indicated internal thermal-induced porosity (TIP) with a 2.3 μm pore diameter. Particle size distribution was in the range from 15.72 μm (d10) to 64.48 μm (d100) as measured by laser particle analyzer. It was indicated that flowability and powder bulk density were 196 sec and 2.79 g/cm3, respectively. XRD analysis confirmed the beta phase of the powder alloy with no additional phases. X-ray fluorescence spectrometry confirmed the alloyed composition. Reducing and oxidative melting methods of analysis showed a slight amount of impurities: oxygen (0.0087 wt.%), nitrogen (0.03 wt.%), hydrogen (0.0012 wt.%), sulfur (0.0016 wt.%), and carbon (0.022 wt.%). Simultaneous thermal analysis (STA) was performed to indicate weight growth and losses and thermal effects in argon, nitrogen, and air as well as the oxidation of Al2O3, TiO2, and Nb2O5 on the surface layer of Ti-12Al-42Nb powder alloy particles. Different phase transformations of γAl2O3 → θAl2O3 → αAl2O3 and TiO2 rutile → TiO2 anatase phase transformation were detected by STA in the oxidative layer.

The large-scale commercialization of polymer electrolyte membrane (PEM) water electrolyzers is still constrained by their high capital cost, which is largely associated with the use of noble metal-based electrocatalysts. There is an urgent need to reduce their loading in the composition of electrocatalytic layers. In the present work, an approach of the microporous sublayer made of titanium nitride (TiNx) and formed over the anode surface by magnetron sputtering is proposed. It contributes to an increase in the anode electrocatalyst utilization, opening up wide possibilities to reduce its loading.

Samples of composites of ultra-high molecular-weight polyethylene (UHMWPE) with addition of 2.24, 5, and 8.1 wt

One of the most important problems in the development of proton exchange membrane fuel cells remains the selection of an efficient electrocatalyst support capable of providing a low loading of active metal with minimal changes in the electrochemical surface, electronic conductivity, and activity. In this work, carbon nanotube arrays (CNTAs) grown directly on commercial gas diffusion layers (GDLs) are used to form electrodes of a new type. The CNTAs are used in the electrode as a microporous layer. The catalytic layer is formed in the microporous layer by a method that does not destroy the carbon support structure and consists of the controlled impregnation of CNTAs with the Pt-precursor with subsequent reduction in platinum particles in the surface volume of the layer. The resulting electrode was studied by scanning/transmission electron microscopy and Raman spectroscopy. This electrode provides increased electrical conductivity of the layer and can also improve stability and longer service life due to the enhanced adhesion of carbon materials to the GDL.

The present research deals with the adaptation of hydrogen-air fuel cells with proton exchange membrane (PEMFC) to autonomous periodic operation at subzero ambient temperatures. The main goal of the research is to limit the influence of subzero temperatures on component integrity and electrochemical performance stability of PEMFC in the cause of the freeze-thaw (F/T) cycling test. The MEAs stability in cycling from subzero (−35 °C) to operating temperature (+35 °C) was ensured without any specific preparatory operations modeling the PEMFC stop and “cold start” procedure. This is provided through the use of hydrogen-methanol compositions (no more than 4 vol % of methanol vapor) as fuel and a composite anode. Advanced membrane-electrode assembly (MEA) based on the composite anode layer (Pt40/C + Pt20/10 wt%–SnO2/C) for efficient and stable subzero operation during F/T cycling. High stability of electrochemical performance of the MEA with the composite anode at subzero ambient temperatures is shown. Advantages of use a two-component fuel PEMFC for autonomous periodic operation at subzero ambient temperatures are highlighted.

A complex study of the structure, morphology, and electrochemical properties of the Pt20/SnO210/RGO electrocatalyst is presented. The advantage of the chemical synthesis of reduced graphene oxide (c-RGO) compared to thermal methods (t-RGO) is due to the formation of graphene plates with amorphous carbon black agglomerates and the chemical composition of the surface. The nature of the interaction between platinum and tin dioxide particles and a conclusion about the formation of heterostructures Pt-SnO2 with the surface interaction of lattices excluding the formation of hetero phases has been established. This achieves high dispersity during the formation of platinum particles without significant agglomeration and increases the electrochemical surface area (ESA) of platinum to 85 m2 g−1 vs. carbon black. In addition, the surface interaction of particles and the formation of hetero-clusters Pt-SnO2 can cause the improved activity and stability of the Pt20/SnO210/c-RGO electrocatalyst.

— β-Tricalcium phosphate (β-Ca 3 (PO 4 ) 2 ) based ceramics with a relative density of 20–21%, grain size from 200 to 600 nm, and compressive strength from 1.6 to 1.8 MPa have been produced by 1000°C firing of cement stone prepared from a powder mixture having a Ca/P molar ratio of 1.5 and consisting of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ), calcium citrate tetrahydrate (Ca 3 (C 6 H 5 O 7 ) 2 ·4H 2 O), and calcium dihydrogen phosphate monohydrate (Ca(H 2 PO 4 ) 2 ·H 2 O). The mixing liquid used to initiate chemical binding reaction in the powder mixture was distilled water. The phase composition of the cement stone included brushite (CaHPO 4 ·2H 2 O) and unreacted starting materials. The presence of platelike calcium pyrophosphate (Ca 2 P 2 O 7 ) particles, formed from platelike brushite (CaHPO 4 ·2H 2 O) particles, impeded densification of the ceramics during firing and ensured the formation of an ultraporous structure. The submicron-grained microstructure and phase composition of the β-Ca 3 (PO 4 ) 2 -based ceramics resulted mainly from heterophase interactions between the products of thermal decomposition of cement stone components. Offering sufficient strength, biocompatible and bioresorbable ultraporous submicron-grained β-Ca 3 (PO 4 ) 2 -based ceramics can be recommended for use in regenerative medicine for bone tissue defect repair.

β-Tricalcium phosphate (β-Ca3(PO4)2) based ceramics with a relative density of 20–21

A mixture of abramis brama (freshwater bream), carassius carassius (crucian carp), and sander lucioperca (pike perch) scales was used for the preparation of fish scale powder containing constituents of organic and inorganic nature. The mixture of the mentioned fish scales was washed, dried, and ground for the preparation of fish scale powder. Vibration sieving was used to prepare fish scale powder enriched with inorganic components. According to thermal analysis data, this fish scale powder enriched with inorganic components included about 36.5 wt.% components removed when heating, primarily those of organic nature, and 63.5 wt.% mineral components. Inorganic powders consisting of hydroxyapatite and magnesium whitlockite were obtained via heat treatment of this fish scale powder at 800–1000 °C. Particles of these inorganic powders consisted of sintered grains with dimensions less than 100 nm after heat treatment at 800 °C, less than 200 nm after heat treatment at 900 °C, and 100–1000 nm after heat treatment at 1000 °C. Fish scale powder enriched with inorganic components as well as heat-treated inorganic powders consisting of hydroxyapatite and magnesium whitlockite can be recommended for the production of different materials, such as ceramics or composites.

The selective sputtering of reduced-activation ferritic-martensitic steel Eurofer upon deuterium plasma irradiation with ion energy of 100 eV is investigated. The experiments are carried out at 550 K and the radiation-dose range of (3–70) × 1024 ion/m2, and in the temperature range 350–730 K at fixed a radiation dose of 3 × 1025 ion/m2. The sputtering-coefficient dependences and information about the complex relief formed on the surface of Eurofer steel under ion irradiation are obtained. The elemental composition of the surface layer is studied by energy-dispersive X-ray spectroscopy and Rutherford backscattering. Enrichment of the surface layer with tungsten is found, which increases with the fluence of plasma irradiation. At the maximum radiation dose, the concentration of tungsten on the surface, averaged over an area of the analyzing beam of 1.7 mm2, was increased by about 13 times and reached a value of about 6 at % (about 14 wt %).

Convolutional neural networks (CNNs) have been widely used in image recognition and processing tasks. Memristor-based CNNs accumulate the advantages of emerging memristive devices, such as nanometer critical dimensions, low power consumption, and functional similarity to biological synapses. Most studies on memristor-based CNNs use either software models of memristors for simulation analysis or full hardware CNN realization. Here, we propose a hybrid CNN, consisting of a hardware fixed pre-trained and explainable feature extractor and a trainable software classifier. The hardware part was realized on passive crossbar arrays of memristors based on nanocomposite (Co-Fe-B)x(LiNbO3)100−x structures. The constructed 2-kernel CNN was able to classify the binarized Fashion-MNIST dataset with ~ 84% accuracy. The performance of the hybrid CNN is comparable to the other reported memristor-based systems, while the number of trainable parameters for the hybrid CNN is substantially lower. Moreover, the hybrid CNN is robust to the variations in the memristive characteristics: dispersion of 20% leads to only a 3% accuracy decrease. The obtained results pave the way for the efficient and reliable realization of neural networks based on partially unreliable analog elements.

Photonic crystals based on amorphous SiO2 nanospheres have been obtained in four-component H2O–Si(OC2H5)4–NH3–EtOH systems at a constant initial volume (100 mL), a constant molar ratio of NH3:Si(OC2H5)4 = 10 : 1, and varied molar ratio of H2O–Si(OC2H5)4 (x1) and H2O–EtOH (x2) within the range of 30–110 and 0.4–2.8, respectively. The increase in water concentration and simultaneous decrease in the alcohol concentration in the initial mixture have resulted in the reduction of mean diameter of the SiO2 spheres from 440 to 270 nm. The curves of the correlation curves between effective diameter of the nanospheres– and the H2O–Si(OC2H5)4 and H2O–EtOH molar ratio have shown two regions with different slopes: for the samples obtained at low H2O–Si(OC2H5)4 and H2O–EtOH molar ratios for these obtained at [H2O] : [Si(OC2H5)4] > 50, [H2O] : [EtOH] > 1. Correlations between the size of the nanospheres of oligomerized SiO2, the initial rate of the process, and the dielectric constant of the initial mixture have been found. The spectral parameters of the photonic crystals obtained on the basis of the amorphous SiO2 spheres have been affected by the H2O–Si(OC2H5)4 and H2O–EtOH molar ratios in the initial mixtures.

Comparative studies of resistive switching (RS) effect of metal/nanocomposite/metal (M/NC/M), metal/nanocomposite/LiNbO3/metal (M/NC/LNO/M) structures based on NC (Co40Fe40B20)х(LiNbO3)100-x (x = 6–20 at.%) with CoFe nanogranules 2–4 nm in size, as well as structures without a NC layer (M/LNO/M), have been carried out. It was found that the percolation conductivity in NC and presence of a thin LNO layer play a key role in the RS effect. When the metal content approaches the percolation threshold of M/NC/M structures (xp ≈ 10 at.%), low-resistance percolation nanochannels of granules are formed in structures with an embedded LNO layer, which ensure their stable RS, which, however, are noticeably suppressed as x decreases relative to xp by Δх ≈ 1-2 at.%.

Comparative studies of resistive switching (RS) effect of metal/nanocomposite/metal (M/NC/M), metal/nanocomposite/LiNbO 3 /metal (M/NC/LNO/M) structures based on NC (Co 40 Fe 40 B 20 ) x (LiNbO 3 ) 100-x (x=6-20 at.%) with CoFe nanogranules 2-4 nm in size, as well as structures without a NC layer (M/LNO/M), have been carried out. It was found that the percolation conductivity in NC and presence of a thin LNO layer play a key role in the RS effect. When the metal content approaches the percolation threshold of M/NC/M structures (x p ~10 at.%), low-resistance percolation nanochannels of granules are formed in structures with an embedded LNO layer, which ensure their stable RS, which, however, are noticeably suppressed as x decreases relative to x p by Delta x~1-2 at.%. Keywords: resistive switching, memristor, nanocomposite, percolation.

The main features of the synthesis of carboxylate-substituted analogs of octacalcium phosphate Ca8(HPO4)2(PO4)4·5H2O (OCP) by hydrolysis of brushite (CaHPO4·2H2O) and tricalcium phosphate α-Са3(РО4)2 (α-TCP) in buffer solutions based on the salts of succinic, adipic, and citric acids were summarized. The synthesis of succinate-substituted (Suc@OCP) and adipinate-substituted (Adi@OCP) OCPs gives the powders with Ca8(HPO4)2 – xАx(PO4)4·zH2O (А = Suc, Аdi) composition. Thermolysis of substituted OCPs results in a mixture of β-Са3(РО4)2 (β-TCP) and hydroxyapatite Са10(РО4)6(ОН)2 (HAp). Thermolysis features include the absence of an apatite-like decomposition product of pure OCP and higher decomposition temperatures compared to the pure OCP. Suc@OCP and Adi@OCP powders were used for the filling of hydrogels based on polyethylene glycol diacrylate (PEGDA) for the creation of a deformable composite implant by a stereolithographic 3D printing method, and fabrication of biphasic TCP/HAp ceramics.

In this paper, we study the effect of platinum loading on the structure, density, and uniformity of deposition of a platinum film sputtered by a magnetron, as well as on the electrochemical characteristics of the deposited electrodes, such as the electrochemically active surface area of platinum (EASA), the durability of the electrodes, and the electrochemical performance of membrane-electrode assemblies of a fuel cell generally. An increase in the mean diameter of individual platinum particles from 1.5 to 3.8 nm and particle agglomerates from 5 to 12 nm, respectively, is shown to be observed as the platinum loading in the samples increases from 0.15 to 1.65 mg/cm 2 . A decrease in the EASA of catalysts occurs due to an increase in the thickness of the sputtered film and partial overlap of the active sites of the electrocatalyst. In this case, the platinum film is a nanostructured catalytic layer with a high degree of uniformity of the deposited metal. The catalytic layers obtained by sputtering platinum using a magnetron in a pulsed mode are characterized by high values ​​of the active surface up to 112 m 2 /g and improved durability due to the strong interaction of active sites and carbon particles of the substrate, which is confirmed by the results of X-ray diffraction analysis. EASA losses of platinum in the process of stress testing for deposited electrodes were about 20%, which is twice lower than that for catalytic layers based on platinum powder electrocatalysts. The current–voltage characteristics of a fuel cell with deposited electrodes as a cathode increase with increasing the platinum film thickness. The maximal characteristics were obtained for electrodes with a platinum film thickness of about 100 and 200 nm; values ​​of 0.43 and 0.52 A/cm 2 were obtained at 0.5 V.

The memristive properties of Cu/nanocomposite/ LiNbO 3 /Cu capacitor structures based on a (Co 40 Fe 40 B 20 ) x (LiNbO 3 ) 100 – x nanocomposite and an amorphous LiNbO 3 interlayer with thicknesses of about 40 and 20 nm, respectively, have been studied. It was found that these structures have relatively low resistive switching voltages (~2 V) and are capable of withstanding more than 10 4 cyclic switchings due to the formation of conducting channels in LiNbO 3 in fixed regions specified by the position of percolation chains of CoFe nanograins in the nanocomposite. It is shown that the conductance of Cu/nanocomposite/LiNbO 3 /Cu memristors can vary according to local biosimilar rules. A simple neural network based on such memristors, trained by feeding a frequency-coded noise signal to its inputs, was implemented.

The effect metal additives (7 at %) have оn phase transformations at pressures of 2 and 8 GPa in the temperature range of 500–1100°C in C 60 and C 70 fullerites is studied via Raman spectroscopy and neutron and X-ray diffraction. It is shown that carbide-forming elements, Fe and Al, strongly (by hundreds of degrees) raise the temperature of transformation of fullerenes into disorientated graphite, while non-carbide-forming element Ag does not have such an effect. The stabilization effect of crystalline fullerenes is explained using known data on the interaction between metal atoms and fullerene molecules, and compared to the processes of fulleride formation.

Pt/C and Pt/x-SnO2/C catalysts (where x is mass content of SnO2) were synthesized using a polyol method. Their kinetic properties towards oxygen reduction reaction were studied by a rotating disk electrode (RDE) technique in a temperature range from 1 to 50 °C. The SnO2 content of catalyst samples was 5 and 10 wt.%. A quick evaluation of the catalyst activity, electrochemical behavior and average number of transferred electrons were performed using the RDE technique. It has been shown that the use of x-SnO2 (through modification of the carbon support) in a binary system together with Pt does not reduce the catalyst activity in the temperature range of 1–30 °C. The temperature rising up to 50 °C resulted in composite catalyst activity reduction at about 30%.

Polycrystalline diamond (PCD) compacts, made by conventional high pressure-high temperature (HPHT) technology, contain Co catalyst in inter-granular spaces causing degradation of PCD mechanical strength and thermal stability during rock cutting due to thermal expansion and graphitization. To solve this problem a catalyst-free synthesis of PCD based on HPHT sintering of fluorinated nanodiamond (FND) and submicron size aluminum mixtures was explored in the present work. The feasibility of using FND has been established by evaluation of phase stability of FNDs of 5, 10, and 90 nm sizes under industrially favorable P-T conditions (7.5-8 GPa, 1500-1700 degrees C) for PCD synthesis. It was found that surface fluorine slows down the graphitization of nano diamond particles. Enlargement of diamonds from 5 and 10 nm up to a 10 mu m has been observed for FND/Al systems. This phenomenon can be associated with the Wurtz-type reaction under the HPHT conditions leading to formation of inter-granular carbon-carbon bonds between the nanoparticles and formation of the fluid Al-C-F phases in the samples volume, accelerating the mass transport and re-crystallization of nanodiamond. PCD samples sintered from mixtures of fluorinated micro-diamonds, nano-diamonds FND-90 and 3 wt% aluminum exhibited enhanced up to 1200 degrees C thermal stability and as high wear resistance as leached commercial PCD.