Search Results (24)

The coupled effects of Ni and Ti additions on amorphization, spark plasma sintering (SPS) response, and hardness evolution were investigated in Al-rich Al–Fe–Nb-based metastable alloys. Mechanically alloyed Al₈₂Fe₁₄Nb₂Ni₂, Al₈₂Fe₁₄Nb₂Ti₂, and Al₈₂Fe₁₂Nb₂Ni₂Ti₂ powders showed progressive loss of long-range order, with the quinary alloy exhibiting the strongest amorphization tendency, consistent with its higher configurational entropy (5.420 J·mol⁻¹·K⁻¹) and more negative mixing enthalpy (−9.36 kJ·mol⁻¹). SPS displacement analysis revealed that primary displacement contribution occurs during heating and is progressively limited by crystallization-induced stiffening. Consolidation at 500 °C produced amorphous–nanocrystalline composites containing Al₁₃Fe₄ and Al₃Nb, whereas increasing the temperature to 550 °C promoted further devitrification. The highest hardness, 445.4 HV, was obtained for Al₈₂Fe₁₄Nb₂Ni₂, despite its lower amorphous-forming ability than the quinary alloy. This demonstrates that hardness is controlled not by maximum amorphization, but by the kinetic balance between amorphous retention, fine intermetallic precipitation, and densification efficiency. The results identify SPS as a coupled densification–transformation route for designing high-strength Al-based amorphous–nanocrystalline alloys. Full article

Nanostructured products synthesized using electric arc vapor plasma with various alcohol solutions exhibiting very high enthalpy and low mass flow rates in a direct current discharge in direct contact with a vapor vortex surrounding the arc column were studied. The nanostructured products obtained in our experiments with various alcohol solutions (ethanol, propanol, and benzene) were analyzed using modern nanostructure identification methods. The diameters of the synthesized multi-walled carbon nanotubes (MWNTs) ranged from 9 to 35 nm, single-walled carbon nanotubes (SWNTs) from 2 to 4 nm, and graphene flakes from 1 to 7 sheets, depending on the alcohol solution composition. Fullerene-like structures identified by HRTEM were obtained from a benzene mixture using electric arc vapor plasma synthesis. It is shown that the thermal steam plasma process with various alcohol solutions has great potential for the synthesis of nanotubes and graphene flakes due to the continuous and easy-to-implement method, cheap raw materials and adjustable carbon content due to the combination of different mixture compositions. Full article

Tropaeolum tuberosum (mashua) is a native Andean tuber recognized for its high nutritional and bioactive compound content. Among the various morphotypes, the black and yellow variants show potential differences in composition and functionality. This study aimed to compare the thermo-energetic, nutritional, and physicochemical characteristics of two morphotypes (black and yellow) of Tropaeolum tuberosum flour from the Peruvian Andes. Flours were obtained from tubers harvested in Ayacucho, Peru, and analyzed using elemental analysis for carbon, hydrogen, nitrogen, and sulfur (CHNS), inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and bomb calorimetry. The empirical formula is CH_1.74O_0.91N_0.06S_0.005 for black mashua and CH_1.78O_0.92N_0.05S_0.005 for yellow mashua. Black flour exhibited higher protein (17.6% vs. 14.8%) and fat contents (8.0% vs. 6.7%), along with nearly double the iron content. Both flours showed similar starch granule morphology and gelatinization enthalpy (~2 J/g), but the black flour had higher gelatinization temperatures. Calorimetric analysis revealed a greater net calorific value (qNCV) in black mashua flour (4157 ± 22 kcal/kg) than in yellow flour (4022 ± 19 kcal/kg). The thermogravimetric profiles indicated good thermal stability with approximately 30% residual mass. These findings suggested that black mashua flour possesses superior nutritional and energy characteristics, supporting its application in functional food formulations and energy-rich gluten-free products. Full article

Plasma spray coating employs a high-temperature plasma jet to melt and deposit powdered materials onto substrates and plays a critical role in aerospace and manufacturing. Despite its importance, the influence of torch behavior, particularly the thermal response of plasma to gas composition changes, remains inadequately characterized. In this study, a three-dimensional MHD simulation using OpenFOAM (v2112) was performed on a Metco 9MB plasma torch operating in an Ar–H₂–N₂ environment under the LTE assumption to investigate the effect of nitrogen addition. The simulation revealed that increasing nitrogen levels results in a dual effect on the temperature distribution: temperatures rise near the cathode tip and decrease downstream, likely due to variations in the net emission coefficient and enthalpy characteristics of nitrogen. Furthermore, although the outlet velocity remained largely unaffected, the Mach number increased as the nitrogen reduced the speed of sound. These findings provide essential insights for optimizing ternary gas mixtures to enhance coating efficiency in thermal spray applications. Full article

CoCrFeMoNiSi_x (x = 0.25, 0.50, 0.75) HEACs were successfully prepared on Q235 steel substrates by the plasma cladding method. The phase structure, microstructure, element distribution, and wear and corrosion resistance of these coatings were investigated by XRD, OM, SEM, EDS, a friction and wear tester, and an electrochemical workstation. The results show that the CoCrFeMoNiSi_x (x = 0.25, 0.50, 0.75) coatings are composed of a major FCC phase and minor BCC phase. With an increase in Si content, the lattice constant and cell volume of both phases and the BCC phase content in these alloys gradually increase, while the enthalpy of mixing, Gibbs free energy, atomic radius difference, VEC, and phase density decrease. All the three alloys exhibit typical dendritic structures. With an increase in Si content, the enrichment of Mo and Si in the interdendrite region is significantly reduced. The friction coefficients of CoCrFeMoNiSi_x (x = 0.25, 0.50, 0.75) HEACs show a trend of first increasing, then decreasing, and gradually stabilizing with an increase in time, and are 0.604, 0.526, and 0.534, respectively. The wear resistance of the three alloys is mainly related to the changes in crystallinity and high-strength BCC phase content caused by different Si contents. The polarization curves of CoCrFeMoNiSi_x (x = 0.25, 0.50, 0.75) high-entropy alloy coatings show an obvious passivation zone, and the corrosion resistance is significantly better than that of Q235 steel substrate. The CoCrFeMoNiSi_0.75 coating has the highest self-corrosion potential, smallest self-corrosion current, largest capacitive reactance arc radius, and best corrosion resistance in a 3.5% NaCl solution. Full article

Arc-jet facility tests are critical for replicating the extreme thermal conditions encountered during high-speed planetary entry, where the precise determination of flow enthalpy is essential. Despite its importance, a systematic comparison of methods for determining enthalpy in the Scirocco Plasma Wind Tunnel had not yet been conducted. This study evaluates three experimental techniques—the sonic throat method, the heat balance method, and the heat transfer method—under various operating conditions in the Scirocco facility, employing a nozzle C configuration (10° half-angle conical nozzle with a 90 cm exit diameter). These methods are compared with computational fluid dynamics (CFDs) simulations to address discrepancies between experimental and predicted enthalpy and heat flux values. Significant deviations between measured and simulated results prompted a reassessment of the numerical and experimental models. Initially, the Navier–Stokes model, which assumes chemically reacting, non-equilibrium flows and fully catalytic copper walls, underestimated the heat flux. By incorporating partial catalytic behavior for the copper probe surface, the CFD results showed better agreement with the experimental data, providing a more accurate representation of heat flux and flow enthalpy within the test environment. Full article

This paper presents the initial results of the synthesis of β-Ga₂O₃ luminescent ceramics via plasma gas-thermal spraying synthesis, where low-temperature plasma of an argon and nitrogen mixture was employed. A direct current electric arc generator of high-enthalpy plasma jet with a self-aligning arc length and an expanding channel of an output electrode served as a plasma source. The feedstock material consisted of a polydisperse powder of monocrystalline β-Ga₂O₃ with particle sizes ranging from 5 to 50 μm. The study presents the results of both theoretical and experimental studies on the heating rate and average temperature of gallium oxide particles in a plasma jet. The results of computational modelling of the synthesis process of β-Ga₂O₃ via plasma gas-thermal spraying are shown. The obtained ceramic samples were characterized using scanning electron microscopy and X-ray diffraction analysis. Our results indicate that the synthesis process yielded ceramics with a layered texture. The stoichiometric composition of ceramics exhibited a shift towards gallium-rich content. X-ray diffraction data demonstrated a reduction in the lattice parameters and unit cell volume of β-Ga₂O₃ ceramic structure. Radioluminescence spectra of β-Ga₂O₃ ceramics revealed an intensive emission band with a maximum at ~360 nm and non-exponential decay. The synthesized β-Ga₂O₃ ceramics possess potential applications in scintillation detectors. Full article

The enantioselective binding of three proton pump inhibitors (PPIs)—omeprazole, rabeprazole, and lansoprazole—to two key plasma proteins, α1-acid glycoprotein (AGP) and human serum albumin (HSA), was characterized. The interactions between PPI enantiomers and proteins were investigated using a multifaceted analytical approach, including high-performance liquid chromatography (HPLC), fluorescence and UV spectroscopy, as well as in silico molecular docking. HPLC analysis demonstrated that all three PPIs exhibited enantioseparation on an AGP-based chiral stationary phase, suggesting stereoselective binding to AGP, while only lansoprazole showed enantioselective binding on the HSA-based column. Quantitatively, the S-enantiomers of omeprazole and rabeprazole showed higher binding affinity to AGP, while the R-enantiomer of lansoprazole displayed greater affinity for AGP, with a reversal in the elution order observed between the two protein-based columns. Protein binding percentages, calculated via HPLC, were greater than 88% for each enantiomer across both transport proteins, with all enantiomers displaying higher affinity for AGP compared to HSA. Thermodynamic analysis indicated that on the HSA, the more common, enthalpy-controlled enantioseparation was found, while in contrast, on the AGP, entropy-controlled enantioseparation was observed. The study also identified limitations in using fluorescence titration due to the high native fluorescence of the compounds, whereas UV titration was effective for both proteins. The determined logK values were in the range of 4.47–4.83 for AGP and 4.02–4.66 for HSA. Molecular docking supported the experimental findings by revealing the atomic interactions driving the binding process, with the predicted enantiomer elution orders aligning with experimental data. The comprehensive use of these analytical methods provides detailed insights into the enantioselective binding properties of PPIs, contributing to the understanding of their pharmacokinetic differences and aiding in the development of more effective therapeutic strategies. Full article

Higher operating temperatures for gas turbine engines require highly durable thermal barrier coatings (TBCs) with improved insulation properties. A suspension plasma spray process (SPS) had been developed for the deposition of columnar-structured TBCs. SPS columnar TBCs are normally achieved at a short standoff distance (50.0 mm–75.0 mm), which is not practical when coating complex-shaped engine hardware since the plasma torch may collide with the components being sprayed. Therefore, it is critical to develop SPS columnar TBCs at longer standoff distances. In this work, a commercially available pressure-based suspension delivery system was used to deliver the suspension to the plasma jet, and a high-enthalpy TriplexPro-210 plasma torch was used for the SPS coating deposition. Suspension injection pressure was optimized to maximize the number of droplets injected into the hot plasma core and achieving the best particle-melting states and deposition efficiency. The highest deposition efficiency of 51% was achieved at 0.34 MPa injection pressure with a suspension flow rate of 31.0 g/min. With the optimized process parameters, 1000 μm thick columnar-structured SPS 8 wt% Y₂O₃-stabilized ZrO₂ (8YSZ) TBCs were successfully developed at a standoff distance of 100.0 mm. The SPS TBCs have a columnar width between 100 μm and 300 μm with a porosity of ~22%. Furnace cycling tests at 1125 °C showed the SPS columnar TBCs had an average life of 1012 cycles, which is ~2.5 times that of reference air-plasma-sprayed dense vertically cracked TBCs with the same coating thickness. The superior durability of the SPS columnar TBCs can be attributed to the high-strain-tolerant microstructure. SEM cross-section characterization indicated the failure of the SPS TBCs occurred at the ceramic top coat and thermally grown oxide (TGO) interface. Full article

The short-term (5 min) exposure to the supersonic flow of carbon dioxide plasma on ultrahigh-temperature ceramics of HfB₂-30vol.%SiC composition has been studied. It was shown that, when established on the surface at a temperature of 1615–1655 °C, the beginning of the formation of an oxidized layer takes place. Raman spectroscopy and scanning electron microscopy studies showed that the formation of a porous SiC-depleted region is not possible under the HfO₂-SiO₂ surface oxide layer. Numerical modeling based on the Navier–Stokes equations and experimental probe measurements of the test conditions were performed. The desirability of continuing systematic studies on the behavior of ultrahigh-temperature ZrB₂/HfB₂-SiC ceramics, including those doped with various components under the influence of high-enthalpy gas flows, was noted. Full article

High activity of lipoxygenase (LOX) has been identified as a primary cause of oxidative rancidity in legumes. In this study, the application of dielectric barrier discharge atmospheric cold plasma (DBD-ACP) (5 W, 10 min) resulted in an obvious decrease in LOX activity in mung bean (MB), kidney bean (KB), and adzuki bean (AB) flours by 36.96%, 32.49%, and 28.57%, respectively. Moreover, DBD-ACP induced significant increases (p < 0.05) in content of soluble dietary fiber, saturated fatty acids, and methionine. The starch digestibility of legumes was changed, evidenced by increased (p < 0.05) slowly digestible starch and rapidly digestible starch, while resistant starch decreased. Furthermore, DBD-ACP treatment significantly affected (p < 0.05) the hydration and thermal characteristics of legume flours, evidenced by the increased water absorption index (WAI) and gelatinization temperature, and the decreased swelling power (SP) and gelatinization enthalpy (ΔH). Microscopic observations confirmed that DBD-ACP treatment caused particle aggregation. Full article

The European Shock Tube for High-Enthalpy Research is a new state-of-the-art facility, tailored for the reproduction of spacecraft planetary entries in support of future European exploration missions, developed by an international consortium led by Instituto de Plasmas e Fusão Nuclear and funded by the European Space Agency. Deployed state-of-the-art diagnostics include vacuum-ultraviolet to ultraviolet, visible, and mid-infrared optical spectroscopy setups, and a microwave interferometry setup. This work examines the specifications and requirements for high-speed flow measurements, and discusses the design choices for the main diagnostics. The spectroscopy setup covers a spectral window between 120 and 5000 nm, and the microwave interferometer can measure electron densities up to 1.5 × 10²⁰ electrons/m³. The main design drivers and technological choices derived from the requirements are discussed in detail herein. Full article

The transmissive mode laser micro-ablation performance of near-infrared (NIR) dye-optimized ammonium dinitramide (ADN)-based liquid propellant was investigated in laser plasma propulsion using a pulse YAG laser with 5 ns pulse width and 1064 nm wavelength. Miniature fiber optic near-infrared spectrometer, differential scanning calorimeter (DSC) and high-speed camera were used to study laser energy deposition, thermal analysis of ADN-based liquid propellants and the flow field evolution process, respectively. Experimental results indicate that two important factors, laser energy deposition efficiency and heat release from energetic liquid propellants, obviously affect the ablation performance. The results showed that the best ablation effect of 0.4 mL ADN solution dissolved in 0.6 mL dye solution (40%-AAD) liquid propellant was obtained with the ADN liquid propellant content increasing in the combustion chamber. Furthermore, adding 2% ammonium perchlorate (AP) solid powder gave rise to variations in the ablation volume and energetic properties of propellants, which enhanced the propellant enthalpy variable and burn rate. Based on the AP optimized laser ablation, the optimal single-pulse impulse (I)~9.8 μN·s, specific impulse (I_sp)~234.9 s, impulse coupling coefficient (C_m)~62.43 dyne/W and energy factor (η)~71.2% were obtained in 200 µm scale combustion chamber. This work would enable further improvements in the small volume and high integration of liquid propellant laser micro-thruster. Full article

The paper describes new combined heating capability of the IPMech RAS inductively coupled plasma facility VGU-4. A 200 W ytterbium laser was added to the facility as a source of radiative heating. The cylindrical specimen made of the Buran orbital vehicle’s heat-shielding tile material with a black low catalytic coating was exposed to subsonic pure nitrogen plasma jet and laser radiation. The specimen surface temperature reached 1325 ${}^{\circ }$C during combined radiative and convective heating. The maximum heat flux obtained in the combined mode for a laser incident power of 47 W and a VGU-4 HF-generator anode power of 22 kW was 32.1 W/cm${}^2$. The convective heat flux from the nitrogen plasma jet at the same anode power was 12.6 W/cm${}^2$. Adding a laser to an existing inductively coupled plasma facility gives the future opportunity to better simulate entry into the atmospheres of Mars, Venus, the outer planets and their moons. Full article

The main aim of this paper is to study the cation fixation sites in montmorillonite after heating at different temperatures. Montmorillonite was used to adsorb cations (Na⁺, Cu²⁺ and Li⁺) in the solution, and the montmorillonite-adsorbed cations were heated at different temperatures (unheated, 100 °C, 200 °C and 300 °C) for 25 h. Subsequently, the basal spacing of montmorillonite treated at different temperatures was monitored by X-ray diffraction (XRD). The exchangeable cationic content (Na⁺, Cu²⁺ and Li⁺) in montmorillonite was determined based on an inductively coupled plasma emission spectrometer (ICP-OES). In addition, the stretching and bending vibration changes in the OH group and the Si-O bond in montmorillonite were detected by Fourier transform infrared spectroscopy (FTIR). The vibration changes were related to the cation fixation sites. The XRD data showed that when the heating temperature reached 200 °C, the structure of montmorillonite adsorbing Li⁺ and Cu²⁺ ions completely collapsed, but the layer spacing of montmorillonite adsorbing Na⁺ decreased slightly, which indicated that Li⁺ and Cu²⁺ were more easily able to enter the crystal structure. The ICP-OES results showed that the contents of exchangeable Na⁺, Cu²⁺ and Li⁺ in montmorillonite decreased with the increase in heating temperature, and Li⁺ was more easily fixed by montmorillonite than Na⁺ and Cu²⁺. The FTIR data showed that when montmorillonite adsorbed with Li⁺ was heated at more than 200 °C, a new OH stretching vibration band appeared at 3971 cm⁻¹, which may be caused by the migration of Li⁺ into the octahedral vacancy to form a local trioctahedral structure. Na⁺ has a large radius; it can only be fixed near the OH group and may not enter the tetrahedron/octahedron of montmorillonite. The number of charges carried by Cu²⁺ is high and the dehydration enthalpy of hydrated Cu²⁺ is high. When the heating temperature was greater than 200 °C, Cu²⁺ mainly entered the hexagonal cavity of the tetrahedron and caused slight changes in the OH bending vibration. The vibration of the Si-O bond hardly changed after montmorillonite adsorbed Na⁺, but the stretching vibration peak of the Si-O bond moved to the high value region after adsorbing Cu²⁺ and Li⁺, which was speculated to be related to the migration of Cu²⁺ and Li⁺ into the crystal structure. Full article