Compound Particles Research Articles

Characterizing sliding wear behavior of A1100/AlFe (p) composites produced via repeated fold-forging and annealing

Abstract Aluminum matrix/aluminum-iron intermetallic composite materials pose challenges in plastic processing due to the susceptibility of hard intermetallic compound particles to fracture. This study introduces a novel fabrication method involving pure iron mesh, hot-dip aluminum plating, and solidification. Through ten consecutive folding, forging, and intermediate annealing cycles, aluminum matrix and iron undergo diffusion, leading to the formation of Fe2Al5 and FeAl3 interface reaction layers, as confirmed by X-ray diffraction analysis. Subsequent forging cycles cause the breakage or detachment of Fe2Al5 and FeAl3 particles from the interface, resulting in the formation of large-sized Fe2Al5 and small-sized Fe2Al5 intermetallic particles. FeAl3 intermetallic particles are observed via microscopic examination. These particles can be uniformly dispersed within the aluminum matrix through plastic flow, enabling the successful fabrication of A1100/Fe2Al5 and AlFe3 composite sheets. Furthermore, the study investigates the impact of intermetallic compound content, sliding speed, and forward load on the dry sliding wear of A1100/FeAl composites. It is found that Fe2Al5 and AlFe3 intermetallic compound particles effectively mitigate adhesive wear, plowing, and oxidative wear of the composites. With an AlFe intermetallic compound content of 4.3 wt.%, the volume wear rate remains low under conditions corresponding to PV = 56.652 (equivalent to a normal load of 19.6 kPa and a sliding speed of 2.87 m s−1).

Surrogate model-based assessment of particle damage behaviour of Al[sbnd]Zn[sbnd]Mg alloy

Recent research has found some intermetallic compound particles with even stronger hydrogen trapping capacity (e.g., Al7Cu2Fe) than the age-hardening precipitates that are reported to be the origin of hydrogen embrittlement in aluminium. Such intermetallic compound particles can reduce hydrogen concentration at the interface between the precipitates and aluminium by absorbing hydrogen in their interiors, thus preventing the hydrogen embrittlement of aluminium. However, this cannot be achieved if the particles, which have absorbed large amounts of hydrogen, are damaged due to hydrogen embrittlement. In this study, the hydrogen embrittlement of aluminium was observed in situ by X-ray CT, and the damage behaviour was analysed of all the particles that were located in the gauge section of a single tensile specimen. After exhaustive quantification of the size, shape, and spatial distribution of the particles, coarsening processes identified highly correlated design variables. Subsequently, particle damage behaviour was analysed utilizing a surrogate model using a support vector machine. The damage to Al7Cu2Fe particles could be described only by design variables representing size and shape, while those representing spatial distribution were removed through the coarsening processes. No change was observed in the damage behaviour of Al7Cu2Fe particles with increasing hydrogen concentrations, and it was concluded that the dispersion of Al7Cu2Fe particles is effective in preventing hydrogen embrittlement of aluminium. The contribution of damaged particles to the formation of fracture surfaces and the damage behaviour of Mg2Si particles, where damage is accelerated by hydrogen, were also analysed.

Study of secondary charged particles produced in 12C-emulsion interactions at 4.5A GeV/c

This paper deals with the interactions of [Formula: see text]C-nucleus with the nuclear emulsion at 4.5[Formula: see text]A[Formula: see text]GeV/c, focused on distributions of multiplicity and the variation of the average multiplicities for secondary charged particles (black, gray, shower, and heavy particles) for the events released from these interactions. These averages have been calculated based on a model of modified cascade evaporation. A comparison has been made between the average multiplicities of the charged secondary particles produced from [Formula: see text]C and others from projectiles that interact with the nuclear emulsion at different energies, this comparison of [Formula: see text]C with other projectiles shows the fluctuations of the values of the average shower with gray for [Formula: see text]O and [Formula: see text]Si interactions occurring somewhat faster. The average number of shower, gray particles increases with the increasing mass number of the projectile Ap, except for black particles, which are nearly constant. The correlations of the average multiplicities for the different charged secondary particles are discussed. There is strong linear dependence in the correlations of average particles of shower, compound, and heavy on gray particles. The results of experimental and theoretical data were also verified with recent analysis data and new observations and were found to be consistent. Moreover, the results indicate that the residual target nucleus may have reached a temperature and constant excitation energy at a certain value for shower particles. The excess amount of energy at higher values of shower particles may be pumped into the system, and this energy may be expended during a transition of phase in the target nucleus system. The theoretical calculation results show good agreement with experimental data.

Exploring the effects of austenitizing conditions on the heterogeneous microstructure and mechanical properties of 11Cr–11Ni–Ti–Mo maraging stainless steel: Breakthrough in the strength-ductility trade-off

Based on the microstructure analysis, the present research investigated the influence of various austenitizing conditions on the transformation behavior of intermetallic compound particles, i.e. η-Ni3Ti, and the reversed austenite during ageing treatment in Ti–Mo maraging stainless steel, as well as the related mechanical properties. The results revealed numerous tiny rod-like intermetallic compound particles, i.e. η-Ni3Ti, having a Burgers orientation relationship, i.e., {101}α′//{0001}η ; <111‾>α′//<112‾0>η, with the martensite matrix, as well as blocky, lath, and granular reversed austenite of various sizes distributed within the tempered martensite matrix. Regardless of the austenitizing treatment condition, more reversed austenite was found in the samples aged at 520 °C than in those aged at 640 °C. Although this finding was not consistent with the Thermo-Calc predictions, it should be associated with the thermal stability of reversed austenite at different ageing temperatures. In other words, the greater amount of reversed austenite that formed at 640 °C did not remain at room temperature due to secondary martensite transformation during cooling, as was verified by EBSD analysis.

Interfacial reaction characteristics and mechanisms during dissimilar friction stir lap welding of pure copper and Al0.1CoCrFeNi alloy

In order to explore the weldability and widen the applicability of high entropy alloys (HEAs), dissimilar friction stir lap welding of pure copper and Al0.1CoCrFeNi alloy was investigated in this research. The results indicate that a sound dissimilar weld without tunnels and voids is produced, where a ∼20 μm thick interfacial layer is evident at the Cu-HEA interface. The lap joint is fractured at the upper Cu sheet rather than the lap surface during tensile shear test, suggesting an effective bonding of the dissimilar materials. The lap weld roughly consists of three layers along the plate thickness direction, i.e. welds of Cu, HEA and Cu-HEA interface, respectively. The interface of weld, which has experienced the most severe Cu-HEA interaction during welding, is characterized by uniformly distributed and highly recrystallized ultra-fine grains (∼0.79 μm). Meanwhile, intermetallic compounds particles (Al13Cr2 and Al13Co4) ranging in size of 150∼400 nm are generated at the fine grain boundaries. Fast diffusion of Al, Cr and Co elements and easy segregation of these elements during welding result in the formation of the particles. The sufficient DDRX and the pinning effect of particles are responsible for the formation of ultra-fine grains in the weld interface. The present study lays a theoretical foundation for the joining of conventional Cu and the multi-component HEA, which contributes to the improvement of HEA availability in the field of manufacturing industry.

Исследование железоматричных композитов с карбидным упрочнением, полученных спеканием механоактивированных смесей титанидов железа с углеродом

Introduction. The addition of dispersed solid particles of refractory compounds (carbides, borides, silicides) to the structure of alloy is a widely used effective way to increase the wear resistance of steels and alloys. Composites with a matrix of iron-based alloys (steel and cast iron) strengthened by titanium carbide particles are of great practical interest. The main structural characteristics, which define hardness and wear resistance of the composites, are volume fraction, dispersion and morphology of the particles of the strengthening carbide phase. The structure of composites depends on the method of its preparation. The methods of powder metallurgy combined with preliminary mechanical activation of powder mixtures have become widespread. It is previously established that in mechanically activated powder mixtures of FTi35S5 ferrotitanium, consisting of 82 % of (Fe,Al)2Ti phase, and P-803 carbon black, a reaction occurs with the formation of a composite consisting of a steel binder and titanium carbide. The synthesis reaction of carbides occurs in a solid-phase mode at combustion’s temperatures of 900–950 °C. Therefore, there is no coarsening of the structure due to the growth of carbide particles, which is typical for reactions in the presence of a liquid phase. FTi35S5 alloy contains a plenty of impurities (silicon, aluminum and etc). The purpose of the work is to investigate the phase composition and structure of the products of the interaction of Fe2Ti and FeTi iron titanides with carbon under the conditions of reaction sintering of mechanically activated powder mixtures and to determine the possibility of synthesizing iron-matrix composites strengthened with submicron titanium carbide particles. Research methods. The structure and phase composition of sintered compacts from mechanically activated powders were studied by optical metallography, X-ray diffraction (XRD) and scanning electron microscopy (SEM) using determination of the elemental composition by energy-dispersive X-ray spectroscopy (EDX). Experimental technique. The reaction mixtures were prepared using intermetallic powders obtained by vacuum sintering of compacts from iron and titanium powder mixtures of 2Fe+Ti and Fe+Ti compositions. Carbon black was added to the intermetallic powders to convert all the titanium containing in the intermetallic compounds into carbide. The titanides – carbon black mixtures were processed by an Activator 2S planetary ball mill for 10 min milling time at a rotation speed of 755 rpm (40g). The mechanically activated mixtures were cold compacted into cylindrical samples with a diameter of 20 mm, which were sintered in vacuum at а temperature of 1,200 °C and an isothermal holding time of 60 minutes. Results and discussion. According to the results of X-ray diffraction analysis, almost all titanium contained in iron titanides reacts with carbon to form carbide and reduced iron. The sintering products of compacts of both compositions contain target phases: titanium carbide with a slight shift from the equiatomic ratio and α-iron, which has the lattice parameters close to the reference data, and also a few of other phases. The titanium carbide particles in the iron binder were identified on the back-scattered electron (BSE) images due to the tonal contrast: the heavy iron appears darker against the carbide, which is composed of lighter elements. According to EDX analysis, the relative content of titanium and carbon in the carbide particles indeed corresponds to the composition of non-stoichiometric titanium carbide. Conclusion. The composites including titanium carbide and α-iron binder were obtained by sintering of iron titanides and carbon (carbon black) mechanically activated powder mixtures. The granules of composite powders obtained by crushing of sintered compacts are of interest as feedstocks for wear-resistant coatings and additive technologies, as well as for manufacturing of dense materials by other compaction methods: spark plasma sintering (SPS) or hot pressing (HP).

Internal Force Mechanism of Pisha Sandstone as a Soil Amendment to Improve Sandy Soil Structural Stability in Mu Us Sandy Land

Compounding Pisha sandstone (PSS) with sandy soil in Mu Us Sandy Land is a viable agronomical measure to effectively reduce soil erosion and improve soil quality due to the complementary characters and structures of the two materials. Aggregate stability is an important indicator to assess sandy soil erosion resistance and quality, which could be largely affected by soil surface electrochemical properties and particle interaction forces. However, the effect of the compound ratio and particle interaction forces on the aggregate stability of compound soils with Pisha sandstone and sandy soil is still unclear. Therefore, in this study, the electrochemical properties, particle interaction forces, and their effects on the aggregate stability of PSS and sandy soil at five volume ratios (0:1, 1:5, 1:2, 1:1, and 1:0) were determined to clarify the internal force mechanism of PSS to increase sandy soil structural stability in a 10-year field experiment. Experiments were measured by a combined method for the determination of surface properties and aggregate water stability. A ten-year field study revealed that the incorporation of Pisha sandstone significantly enhanced the soil organic carbon (SOC) and cation exchange capacity (CEC) (p &lt; 0.05), while the CEC value notably increased from 4.68 to 13.76 cmol·kg−1 (p &lt; 0.05). The soil surface potential (absolute value) and the electric field intensity gradually decreased with the increase in the Pisha sandstone content. For the compound soil particle interaction force, the addition of Pisha sandstone enhanced the van der Waals attraction force, reduced the net repulsive force between compound soil particles, and promoted the agglomeration of aeolian sandy soil. The overall trend of the aggregate breaking strength of compound soils under different addition ratios of PSS was 1:0 &gt; 1:1 &gt; 0:1 &gt; 1:5 &gt; 1:2. When the Pisha sandstone content in the compound soils was &lt;50%, the aggregate stability was mainly influenced by compound soil particle interaction forces, and the interaction force increase was the key reason for the aggregate breakdown. When the Pisha sandstone content in the compound soils was ≥50%, the aggregate stability was affected by the combined effects of the compound soil particle composition and particle interaction forces. These results indicate that PSS addition ratios and particle interaction force are important factors affecting the structural stability of compound soils, in which the volume ratio of PSS to sandy soil of 1:2 is the appropriate ratio. Our study provides some theoretical references for further understanding of the compound soil structure improvement and sandy soil erosion control in Mu Us Sandy Land.

Removal of reactive black 5 in water using adsorption and electrochemical oxidation technology: kinetics, isotherms and mechanisms

AbstractIn this work, a novel graphite intercalation compound (GIC) particle electrode was used to investigate the adsorption of Reactive Black 5 (RB5) and the electrochemical regeneration in a three-dimensional (3D) electrochemical reactor to recover its adsorptive capacity. Various adsorption kinetics and isotherm models were used to characterise the adsorption behaviour of GIC. Several adsorption kinetics were modelled using linearised and non-linearised rate laws to evaluate the viability of the sorption process. Studies on the selective removal of RB5 dyes from binary mixture in solution were evaluated. RSM optimisation studies were integrated with ANOVA analysis to provide insight into the significance of selectivity reversal from the salting effect of textile dye solution on GIC adsorbent. A unique range of adsorption kinetics and isotherms were used to evaluate the adsorption process. Non-linear models best simulated the kinetic data in the order: Elovich &gt; Bangham &gt; Pseudo-second-order &gt; Pseudo-first-order. The Redlich–Peterson isotherm was calculated to have a dye loading capacity of 0.7316 mg/g by non-linear regression analysis. An error function analysis with ERRSQ/SSE of 0.1390 confirmed the accuracy of dye loading capacity predicted by Redlich–Peterson isotherm using non-linear regression analysis. The results showed that Redlich–Peterson and SIPS isotherm models yielded better fitness to experimental data than the Langmuir type. The best dye removal efficiency achieved was ~ 93% using a current density of 45.14 mA/cm2, whereas the highest TOC removal efficiency achieved was 67%.

Structural Analyses of Polysaccharides Extracted from Cyanobacterial Extracellular Gels and Oriented Liquid Crystalline Microfiber Processing by Poly(vinyl alcohol)-Assisted Electrospinning.

Sacran is a supergiant cyanobacterial polysaccharide that forms mesogenic supercoil rods that exhibit liquid crystalline (LC) gels at deficient concentrations of around 0.5 wt%, and has several bioactive stimuli-responsive functions. Here, we attempted to form oriented microfibers of sacran by electrospinning, following structural analyses of the sacran rods. A heterogeneous acid-hydrolysis method using a protonated cation-exchange resin was adopted to examine the short-time exposition of concentrated acid to sacran rods. From the supernatant, the oligomeric fraction that was soluble in water and methanol was isolated. The oligomeric fraction had a main sugar ratio of α-Glc:β-Glc:α-Xyl:β-Xyl:α-Rha of 2:5:1.5:1.5:4 (Glc:Xyl:Rha = 7 (=4 + 3):3:4), and it was speculated that the sacran structure includes rhamnoglucan and xyloglucan (4:3), which are generally rigid enough to exhibit LC. To make oriented microfibers of LC sacran, solubility testing was performed on sacran to find good new solvents of polyhydroxy alcohols such as ethylene glycol, 1,2-propanediol, and glycerol. The oriented film was prepared from a sacran aqueous solution where calcium compound particles deposited on the film are different from polyhydroxy alcohol solutions. Although sacran could not form microfibers by itself, polymer composite microfibers of sacran with poly(vinyl alcohol) were prepared by electrospinning. Cross-polarizing microscopy revealed the molecular orientation of the microfibers.

Inorganic Compound and Cycloserine Composite Particles for Improved Stability

The aim of this study was to improve the chemical stability of cycloserine containing organic and inorganic compounds. Composite particles were manufactured with a 1:1 weight ratio of organic/inorganic compounds and cycloserine. The influence of organic/inorganic compounds on the stability of cycloserine was investigated under accelerated stress conditions at 60°C/75% RH for 24 hours. In addition, the properties of the composite particles were evaluated using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and the dissolution of the drug was assessed by preparing it as a hard capsule. Among the organic and inorganic compounds investigated, calcium hydroxide most improved the stability of cycloserine under accelerated stress conditions (53.3 ± 2.2% vs 1.7 ± 0.2%). DSC results confirmed the compatibility between calcium hydroxide and the cycloserine, and SEM results confirmed that it was evenly distributed around the cycloserine. Calcium hydroxide also showed more than 90% cycloserine dissolution within 15 minutes. Therefore, the calcium hydroxide and cycloserine composite particles may be candidates for cycloserine oral pharmaceuticals with enhanced drug stability.

Mechanical Bonding Properties of Solderable Anisotropic Polymer Composite containing Low-Melting-Point and High-Melting-Point Solder Fillers

In this papers, to enhance the mechanical bonding properties of solderable anisotropic polymer composites (SAPCs) containing low-melting-point solder filler only, a new low-melting-point solder and high-melting-point solder mixed filler filled SAPCs (LH-SAPCs) was proposed, and the influence of the high-melting-point solder filler on the conduction path formation and mechanical bonding properties of the LH-SAPC were investigated. Two types of LH-SAPC were synthesized by adding high-melting-point solder within the low-melting-point solder/high-melting-point solder mixed filler at mixing ratios of 0 and 50 vol% (the volume fraction of low-melting-point solder/high-melting-point solder mixed filler in the polymer composite was 20%), and a bonding test was conducted using QFP. The results exhibited that the LH-SAPC containing high-melting-point solder formed a wide and stable conduction path due to the proper selective conduction path formation behavior by the interaction between molten low-melting-point solder and solid-state high-melting-point solder fillers within the polymer composite with low viscosity condition. Furthermore, the mechanical bonding properties of the LH-SAPC joints containing high-melting-point solder were enhanced compared to that of LH-SAPC containing low-melting-point solder only owing to the precipitation hardening and dispersion strengthening effects due to the increase of fine Bi-rich, Cu&lt;sub&gt;6&lt;/sub&gt;Sn&lt;sub&gt;5&lt;/sub&gt;, and Ag&lt;sub&gt;3&lt;/sub&gt;Sn intermetallic compound particles inside the conduction path.

Dysprosium hydroxide nanoparticle-embedded photoluminescent composite films

Dy(NO3)3 was dissolved in water–ethanol complex solvent, and the obtained solution was used to fabricate composite films wherein Dy compound particles were embedded in a transparent urethane resin. All the resulting composite films exhibited photoluminescence properties attributed to the Dy-based compounds. When the composite films were prepared by varying the water/ethanol ratio of the raw material solution, the PL intensity was stronger when the water content of the composites was higher. Further ultraviolet irradiation of the resulting films caused the disappearance of the Dy–OH bonds and decrease in the PL intensity of the films. The increase in the PL intensity with increasing water content was attributed to the presence of Dy–OH bonds in the films. In addition, we investigated the presence and PL properties of Dy–OH bonds in Dy-based particle composite films.

One-step hydrothermal synthesis of sulfur quantum dots for detection of Hg2+ ions and latent fingerprints

High blue-emitting sulfur quantum dots (SQDs) with quantum yields of up to 58.7% were prepared using elemental sulfur using a facile ethylenediamine-assisted hydrothermal acceleration method at 60 °C for 7 h. In the presence of ethylenediamine, bulk sublimated sulfur powder can be broken down into fine particles of sulfur-nitrogen compounds and then oxidized to produce SQDs. HRTEM analysis of the morphology of SQDs showed that SQDs had a quasi-spherical shape with a size of 3.2 nm. In this process, under the influence of ethylenediamine, sublimated sulfur is rapidly converted from zero-valent sulfur to polysulfide with simple heating, greatly improving manufacturing efficiency. Synthesized fluorescent sulfur quantum dots (SQDs) were used in this study as fluorescent probes for quantitative detection of Hg2+. The SQD served as an effective Hg2+ detection probe with a detection limit of 2.7 μM through an efficient on-off switching mechanism in response to Hg2+. In addition, latent fingerprints were recognized using SQD powder, and fingerprints were detected on the surfaces of various media, such as paper, glass, and aluminum foil. The synthesized SQDs have a high potential for sensing applications of various luminescent materials.

Исследование продуктов синтеза в механоактивированных смесях титанидов меди с углеродом

Metal matrix composites reinforced with dispersed carbide particles have an optimal combination of strength and wear resistance. The composites are used as structural materials, wear-resistant materials and coatings as well as functional materials. Copper matrix composites for electrical purposes are strengthened with particles of refractory compounds (carbides, borides, silicides). They are used to manufacture breaking electrical contacts which have increased resistance to erosion under the electric arc exposure. The highest arc erosion resistance is achieved by composites with a structure, in which submicron particles of refractory compounds are homogeneously distributed in the copper matrix. Powder technologies are used to obtain the copper matrix composites. A large number of publications concerns with the production of copper matrix composites strengthened by dispersed particles of titanium diboride. The composite powder was obtained by self-propagating high- temperature synthesis (SHS) occurring through mechanically activated mixtures of titanium, copper and carbon. The synthesis products were compacted by spark plasma sintering (SPS). In the present work, the microstructure, elemental and phase composition of the products of the synthesis reaction occurring through mechanically activated reactant powder mixtures of copper titanides with carbon (soot) subjected to additional heat treatment were studied using the methods of X-ray diffraction, optical and scanning electron microscopy. Copper matrix composites strengthened by carbide particles were obtained by copper reduction from intermetallic compounds (copper titanides) via reaction: TimCun+ C → TiC + Cu. The use of the copper titanides instead of titanium and copper powders eliminates the blocking of surface titanium-carbon reaction by copper during the mechanical activation of titanium-copper-carbon powder mixtures. This ensures a more complete conversion of titanium carbide in the synthesis reaction. It is established that the dispersion of the carbide phase in the structure of the synthesized ‘titanium carbide-copper binder’ composite depends on the elemental ratio of titanium and copper in the reaction mixtures. With an equiatomic content of titanium and copper the synthesis results in a matrix-type composite, in the structure of which submicron (less than 300 nm) carbide inclusions are homogeneously distributed throughout the copper binder. Unreacted copper and titanium in the titanide powders do not prevent the attainment of target phase composition of the synthesis products that include only titanium carbide and copper.

Exploring the properties of uranyl nicotinate: Synthesis, characterization, and thermal analysis

This study reports the successful synthesis and characterization of a uranyl nicotinate compound, UO2(C6H4NO2)2?0.25H2O. The compound was synthesized using a metal 1:2 ligand ratio and water as the solvent. The average yield of the compound was 67 %. Thermogravimetric analysis revealed multiple stages of mass loss, including dehydration, nitrogen decomposition and UO2 2+ reduction. Fourier-transform infrared spectroscopy confirmed the coordination of the carboxylate group in the compound. Field emission gun scanning electron microscope analysis showed the particles with a regular oval shape. Energy-dispersive X-ray spectroscopy provided semi-quantitative data on the elemental composition of the compound. The major elements identified were uranium, carbon, oxygen and nitrogen. These results contribute to understanding the compound?s synthesis, thermal behaviour, molecular composition, particle morphology and elemental composition. Further research can build upon these findings to explore potential applications and develop new compounds with tailored properties.

LaMer-model-based synthesis method for fine particles of octacalcium phosphate and related functional compounds

We developed a new precipitation method based on the LaMer model for synthesising fine particles of plain octacalcium phosphate (OCP) and OCP with incorporated carboxylate ions.

Modes of wear of babbitt-based composite materials produced by hot pressing

The effect of additives of Ti2NbAl intermetallic compound on the friction of B83 babbitt samples obtained by hot pressing was studied using optical, electron microscopy and EDS analysis. The structure, friction surface and wear products were studied. Tribological tests were carried out on a universal test system under conditions of dry sliding friction according to the scheme of axial loading: a steel bush against a disk of the material under study. The temperature values near the friction zone were recorded. The limits of application of the material depend on the mode and mechanism of wear occurring in the tribocontact. Changes in the mode and mechanism of wear were assessed by differences in the behavior of the friction coefficient, temperature, difference in the state of friction surfaces, wear intensity and wear products. The results obtained indicate the prospects of using the method of hot pressing of powder from the B83 alloy and discrete particles of the high-strength Ti2NbAl intermetallic phase to get composite materials with improved tribological properties compared to a babbitt alloy. The introduction of reinforcing high-modulus particles of intermetallic compounds changed the structure of the material and affected the friction processes in babbitt, pushing aside the onset of change in the mode of wear towards more severe friction conditions. A significant decrease in the wear intensity of babbitt-based composite materials compared to the original alloy makes it possible to predict an increase in the service life of tribo-units. The data obtained enable us to determine and recommend modes that improve the performance of tribo-nodes in the manufacture of both volumetric inserts and plain bearings made of B83 alloy and, moreover, to create new functionally organized layered compositions with enhanced tribotechnical properties with a base of structural steels and working surface layers not only using B83 babbitt, but also of composite materials based on B83 babbitt.

Word Formation with Foreign Lexemes: The Case of Hybrid Compounds in Arabic

Arabic compounds consist of a group of two or three words joined together into one vocabulary unit. Syntactically, Arabic compounds consist of a Noun + adjective; Noun + apposited noun; Noun + apposited noun + adjective; Noun + apposited N. + apposited N; Noun + the negative particle لا no/non; compound adverbs; and compound particles. Orthographically, the lexical items in most Arabic compounds are separated by a blank, few are agglutinated (spelled together) and few more are hyphenated. This study aimed to explore the status of hybrid compounds in Arabic within its terminological structure; their denotative and connotative meanings; how productive they are; whether they are used in Standard or Colloquial Arabic; whether they are permanent or transient; in which domains they are used; and why hybrid compounds are coined by Arabic-speakers. To achieve those purposes, a corpus of hybrid compounds containing the foreign lexemes/affixes Arabia, book, café, cast, center, co, com., expo, extra, for, gate, hyper, leaks, link, mania, mart, media, meter; mini, mobile, net, pal, pedia, petro, pharma, phone, press, pro, sat, show, soft, super, talk, tech, tic, times, top, tube, ultra, web, and wiki combined with Arabic lexemes was collected. Data analysis showed that specialized hybrid compounds, those used for names of satellite T.V. station, names of electronic newspapers, news agencies and companies are more permanent than those used during the Arab Spring or those used in names of forums, blogs, T.V. shows or newspaper articles which appeared for a short time then disappeared. The former set of hybrid compounds are used in Standard Arabic and formal contexts, whereas the latter set is used in Colloquial Arabic. The former constitutes a small set of hybrid compounds coined by specialists and Arabic language academies, whereas the latter is more prolific as those compounds were created by activists, political analysts, journalists, and social media users. The study revealed promotional, linguistic, globalization and sociocultural factors for coining hybrid compounds, and lack of a business naming policy. Hybrid compounds constitute a threat to Arabic and hinder the linguistic development of the young generation.

Size-controlled Co/CoO heterogeneous nanoparticles confined in N-doped mesoporous carbon for efficient oxygen reduction in zinc-air batteries

The size of metal compound particles and interface electronic structure of heterojunctions in a matrix greatly affect oxygen reduction performance in zinc-air batteries. However, it is still a big challenge to precisely control or regulate the size of these metal compound particles and the heterojunction structure. Herein, cobalt complexes with different-sized ligands are chosen as cobalt resources and adsorbed onto a mesoporous carbon, after which they are coated with polydopamine and calcined. Under the confinement effect of mesopores and the isolation effect of ligands and dopamine, the as-obtained Co/CoO heterogeneous nanoparticles are restricted to nano-size and uniformly dispersed in N-doped carbon (NC). The sizes of Co/CoO are estimated to be 39.7, 24.9 and 15.6 nm with increased CoO contents, corresponding to the adopted cobalt precursors of Co(OAc)2, Co(acac)2 and Co(acac)3, respectively. The smallest Co/CoO/NC-S shows excellent catalytic activity for oxygen reduction reaction, with a half-wave potential of 0.82 V vs. RHE and a limiting current density of 4.59 mA cm−2. When applied to the cathode of zinc-air battery, a high peak power density of 131.9 mW cm−2 is achieved, which surpasses that of the battery powered by Pt/C. The excellent performance can be attributed to the formation of heterogeneous structures between Co and CoO, the smaller Co/CoO nanoparticles, and N-doped mesoporous carbon with effective charge/mass transport. This work provides an effective way to regulate the size and phase contents of heterogeneous particles in mesoporous carbon, which is highly valuable in electrocatalytic systems.

Refractory high-entropy aluminized coating with excellent oxidation resistance and lubricating property prepared by pack cementation method

Refractory high-entropy alloys (RHEAs) exhibit superior mechanical properties at high temperatures compared to that of conventional high-temperature alloys. However, some refractory metallic elements are highly susceptible to oxygen absorption at room temperature and the resulting oxide films are not protective, resulting in catastrophic oxidation before they can exhibit excellent mechanical properties. Therefore, it is essential for them to improve the high-temperature oxidation properties of RHEAs. The pack cementation method can be used to prepare the aluminized coatings on the surface of RHEAs to improve their high-temperature oxidation resistance. In the present work, the aluminized high-entropy coatings were prepared on the surface of as-cast Ta25Nb25W25V25 RHEAs. The diffusion activation energy required for aluminization was experimentally calculated to be 137.667 kJ/mol, thus the growth kinetics of the coating was constructed. Aluminized coatings with the thickness of ∼75 μm and Vickers hardness of ∼680 HV0.01 obtained by holding at 1100 °C for 9 h were selected for the study. The oxidation activation energy of the aluminized coating at 800–1000 °C was 96.981 kJ/mol, while that of as-cast RHEAs was only 48.816 kJ/mol, so the oxidation resistance of the specimen was greatly improved. At 20–600 °C, the aluminized coatings also exhibited excellent wear resistance and lubrication properties. In particular, the average coefficients of friction were reduced by 0.13–0.24 compared to that of as-cast RHEAs, which can be attributed to the AlW intermetallic compound particles formed within the aluminized coating acting as self-lubricating particles.