Phase Content Research Articles

Optimized magnetic properties of a Terfenol-D alloy in an extended temperature range using a high magnetic field

Tb–Dy–Fe alloys are among the most suitable magnetostrictive materials for high-power transducers. Optimizing magnetic properties in an extended temperature range could ensure the stable operation of transducers. In this work, a high magnetic field is applied to the directional solidification of Tb–Dy–Fe alloys. We study the microstructure, crystallographic orientation, magnetic susceptibility, crystal structure, and magnetic domain of samples. When the content and alignment of the magnetic phase along with crystallographic orientation remain basically invariant, the magnetic susceptibility of samples increases with the magnetic flux density of the high magnetic field throughout the temperature range from 273 K to Curie temperature (T C). At 4 T, the maximum magnetic susceptibility is increased by ∼ 40% compared with the sample without a high magnetic field applied, and the advantage is maintained in the range ∼ 300 K. Analysis shows that the enhancement of magnetic susceptibility is not due to the change in crystal structure, as commonly believed, but to the highly ordered alignment of magnetic domains. This research provides a new method for improving the temperature properties of magnetic materials using a high magnetic field.

Use of graphene (go and rGO) as a reinforcement filler to increase the beta phase in fluorinated copolymer nanocomposites

The present study aims to evaluate the influence of different types of graphene, graphene oxide (GO, synthesized by the Hummers method) and reduced graphene oxide (rGO, obtained by thermal reduction of GO) on the piezoelectric properties of composites based on PVDF copolymer. Hydrogen-fluorine interaction is expected to occur between GO or rGO and the fluorinated copolymer, increasing the β-conformation content in the polymer. The samples were prepared in the molten state at two concentrations of each charge inside a twin-screw extruder with interpenetrating screws. The characterizations of the nanocomposites were made according to their thermal and electrical properties. The effect of graphene incorporation into the P(VDF-TrFE) matrix was observed from thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results obtained indicated that the incorporation of graphene contributed to the increase in the β phase content of P(VDF-TrFE), which is indicative of the increase in its piezoelectricity.

Discovery of a new volcanic soil material, "Akahoya," as an adsorbent for bacterial and viral pathogens and its application to environmental purification.

Akahoya is a volcanic soil rich in alumina, primarily deposited in Kyushu, Japan. We have found that Akahoya adsorbs bacteria in the water surrounding cattle grazing areas, suggesting a potential for environmental purification. This study investigated the spectrum of microorganisms adsorbed by Akahoya using a column filled with Akahoya through which a suspension of microorganisms was passed. Shirasu soil, another volcanic soil with a different chemical composition, was used as a control. Akahoya effectively adsorbed a diverse range of microorganisms including Escherichia coli, Campylobacter jejuni, Vibrio parahaemolyticus, Salmonella Enteritidis, Staphylococcus aureus, Clostridium perfringens, spores of Bacillus subtilis and Bacillus anthracis, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), murine norovirus, and avian influenza virus (H3N2), whereas Shirasu soil did not adsorb any of the organisms examined. Moreover, bacteria naturally present in river water, such as aerobic bacteria, total coliforms, and Enterobacteriaceae as indicators of river contamination, as well as E. coli added artificially to sterilized river water, were reduced to below the detection limit (<1 CFU/mL) after being passed through Akahoya. Additionally, the number of viable E. coli continued to decrease after contact with Akahoya for 1 month, suggesting bactericidal effects. Notably, the adsorption of E. coli to Akahoya was influenced by the concentration of phosphate and the pH of the suspension due to the interaction between the surface phosphorylation of organisms and Al2O3, the major chemical component of Akahoya. The present results demonstrate the remarkable ability of Akahoya to remove phosphate and microbes, suggesting that Akahoya could be used for water purification processes.IMPORTANCEAlthough a safe and sufficient water supply is essential for the maintenance of hygienic conditions, a major challenge is to develop a comprehensive effective, sustainable, and cost-effective technological approach for the treatment and purification of contaminated water. In this study, we demonstrated that a novel volcanic soil, Akahoya, which has unlimited availability, is a highly effective adsorbent for a wide range of bacterial and viral pathogens, suggesting its potential as a sustainable resource for this purpose. It was suggested that the adsorption of microorganisms on Akahoya was mediated by phosphate groups present on the surface structures of microorganisms, which bind to the alumina component of Akahoya according to the phosphate concentration and pH of the liquid phase. The present findings highlight the exceptional ability of Akahoya to eliminate or reduce phosphate and microorganisms effectively in water purification processes, thus contributing to the development of efficient and sustainable solutions for addressing water pollution challenges.

Simultaneous Tailoring of Chemical Composition and Morphology Configuration in Metal Hexacyanoferrate for Ultrafast and Durable Sodium‐ion Storage

Metal hexacyanoferrates (MHCFs) with adjustable composition and open framework structures have been considered as intriguing cathode materials for sodium‐ion batteries (SIBs). Exploiting MHCFs with ultrafast and durable sodium storage capability as well as comparable capacity is always a goal that many investigators pursue, but remains challenging. Herein, simultaneous tailoring of chemical composition and morphology configuration is carried out to design a hollow monoclinic high‐entropy MHCF (HMHE‐HCF) assembled by nanocubes for the first time to realize the objective. The “cocktail effect” of high‐entropy construction, rich sodium content of monoclinic phase, and unique hollow structure endow HMHE‐HCF cathode with fast reaction kinetics and energetically stable performance during continuous charging/discharging processes. As a result, the HMHE‐HCF cathode demonstrates superior rate performance up to an ultra‐high rate of 100 C (71.1% retention to 0.1 C), and remarkable cycling stability with a capacity retention of 77.8% over 25,000 cycles at 100 C, outperforming most reported sodium‐ion cathodes. Further, the HMHE‐HCF//hard carbon full‐cell delivers capacities of 99.0 and 82.3 mAh g–1 at 0.1 C and 10 C, respectively, and retains 98.1% of the initial capacity after 1,600 cycles at 5C, demonstrating its potential application for sodium‐ion storage.

Simultaneous Tailoring of Chemical Composition and Morphology Configuration in Metal Hexacyanoferrate for Ultrafast and Durable Sodium-ion Storage.

Metal hexacyanoferrates (MHCFs) with adjustable composition and open framework structures have been considered as intriguing cathode materials for sodium-ion batteries (SIBs). Exploiting MHCFs with ultrafast and durable sodium storage capability as well as comparable capacity is always a goal that many investigators pursue, but remains challenging. Herein, simultaneous tailoring of chemical composition and morphology configuration is carried out to design a hollow monoclinic high-entropy MHCF (HMHE-HCF) assembled by nanocubes for the first time to realize the objective. The "cocktail effect" of high-entropy construction, rich sodium content of monoclinic phase, and unique hollow structure endow HMHE-HCF cathode with fast reaction kinetics and energetically stable performance during continuous charging/discharging processes. As a result, the HMHE-HCF cathode demonstrates superior rate performance up to an ultra-high rate of 100 C (71.1% retention to 0.1 C), and remarkable cycling stability with a capacity retention of 77.8% over 25,000 cycles at 100 C, outperforming most reported sodium-ion cathodes. Further, the HMHE-HCF//hard carbon full-cell delivers capacities of 99.0 and 82.3 mAh g-1 at 0.1 C and 10 C, respectively, and retains 98.1% of the initial capacity after 1,600 cycles at 5C, demonstrating its potential application for sodium-ion storage.

Microstructural evolution and mechanical properties of FeNiVAlx medium-entropy alloy

FeNiV alloys exhibit potential applications in magnetic, radiation-resistant, mechanical, and superconducting fields, however, the formation of the hard yet brittle sigma phase enriched with Fe and V hindered their application in extreme environments. Therefore, improving the mechanical properties of FeNiV alloys has been a crucial problem. In this study, a series of as-cast FeNiVAlx (values of x is 0, 0.1, 0.2, 0.3) medium-entropy alloys (MEAs) were fabricated by vacuum arc melting, and the evolution of microstructure and mechanical properties with different Al microalloying were investigated systematically. As the Al content increased, FeNiVAlx MEAs underwent a structural transformation from a dual-phase structure consisting of a FCC phase (46.4 %; phase content) and a sigma phase (53.6 %) at x=0 to a single BCC phase in FeNiVAl0.3, while the mechanical properties of the alloy show a decrease in strength and a significant increase in elongation. Notably, the FeNiV alloy exhibits the highest yield strength of 1851 MPa with 7.8 % ductility. In contrast, the FeNiVAl0.2 alloy demonstrated superior comprehensive compressive properties, with a high yield strength of 1255 MPa and an exceptional ductility exceeding 50 % without fracturing. The elimination of the harmful sigma phase, coupled with the formation of BCC phase, contributes to the observed decrement in strength and increment in ductility. This study elucidates the intrinsic relationship between microstructure and mechanical properties with Al contents in FeNiVAlx alloys, providing insights for the design of MEAs with excellent strength-ductility balance through microalloying.

Spectral induced polarization (SIP) measurements across a PFAS-contaminated source zone

There is a need to develop field-scale, in situ screening technologies for assessing variations in aqueous film-forming foam (AFFF) concentrations in soils at former fire training and storage sites. Field-scale Spectral Induced Polarization (SIP) geophysical measurements were acquired on a transect crossing an AFFF source zone. Soil samples were acquired to determine variations in poly- and per-fluoroalkyl substances (PFAS) concentrations in soils, characterize soil texture, and create triplicate soil columns for laboratory SIP measurements. Field and laboratory observations show that SIP measurements are sensitive to the concentration of AFFF constituents associated with soil pore surface area. The specific polarizability and the phase of the SIP measurements for the laboratory samples were linearly correlated with total soil-sorbed PFAS concentration. The phase from the field SIP measurements was highest over the location of maximum PFAS concentration measured on the laboratory samples. However, a significant correlation between field-measured phase and laboratory-measured total PFAS concentration still needs to be established. These observations, along with the demonstrated sensitivity of the SIP response to the removal of soil PFAS using a methanol wash procedure, support the case for SIP characterization of AFFF source zones.

Correlation between preparation techniques and frictional properties of cellulose nanocrystals as additives in water-based lubricants

To explore the tribological characteristics of cellulose nanocrystals derived through various preparation techniques when utilized as additives in water-based lubricants, two types of cellulose nanocrystals (S-CNC and C-CNC) were chosen. These were produced via sulfuric acid hydrolysis and oxidation methods. The morphology and structural features were assessed through techniques such as Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), laser confocal Raman spectroscopy, elemental analysis, scanning electron microscopy (SEM), and laser particle size analysis. According to thermogravimetric analysis (TGA), the thermal stability of S-CNC is slightly superior to that of C-CNC. S-CNC exhibits liquid crystallinity when the concentration exceeds 0.5 %, whereas C-CNC does not display liquid crystallinity at any concentration tested. Further investigation was conducted on the frictional properties of the two types of CNCs using a UMT reciprocating friction tester. The results indicate that both types of CNC exhibit significant friction reduction properties at various additive concentrations, provided the addition does not exceed w=1 %. When below their respective liquid crystalline phase concentrations, the friction reduction performance of S-CNC is slightly inferior to that of C-CNC; however, when above the liquid crystalline phase concentration, the friction reduction performance of S-CNC surpasses that of C-CNC. The addition of w=0.5 % S-CNC leads to a relative reduction of 63.4 % in the friction coefficient compared to the base system. Analysis of the steel plate surface contact angle and post-wear surface suggests that the lubrication mechanism of CNC involves the adsorption of polar functional groups such as hydroxyl or carboxyl groups from the CNC structure onto the friction pair surface, forming a lubricating protective film to varying degrees. Additionally, the liquid crystalline structure of S-CNC facilitates the formation of an ordered lubricating film, further enhancing the frictional properties. These findings provide valuable insights into the application of nanocellulose crystals as lubricant additives.

The preparation and characterization of WS2 nanomaterials with different morphologies and the mechanistic study of peroxymonosulfate activation for phenol degradation

Transitional metal chalcogenides like WS2 play a significant role as cocatalysts in activating PMS (peroxymonosulfate) due to their high reductivity. Three WS2 samples with different morphologies, specific surface areas, and 1 T phase contents were prepared in this study. Characterizations by SEM, TEM, BET, XRD, Raman, XPS, and catalytic degradation experiments confirmed that the a-WS2 sample exhibited the richest morphology, the largest specific surface area, the highest 1 T phase content, and the best cocatalytic performance. The a-WS2/Fe(II)/PMS system efficiently degraded 20 mg/L phenol within 15 minutes and was also effective in degrading pollutants like RhB (Rhodamine B) and OFX (Ofloxacin). Characterization predicted the degradation pathway of phenol and revealed 10 intermediate products. The degradation mechanism indicated that the presence of WS2 accelerated the conversion of Fe(III) to Fe(II), thereby further promoting the activation of PMS. ·SO4−, ·OH, and ·O2− were identified as the main active radicals in this system. a-WS2 exhibits characteristics such as high catalytic performance, good stability, high recyclability, and a low ion leaching rate, and it generates sulfur vacancies during use. This system shows promising prospects in the treatment of high-concentration organic wastewater.

Exploring the mechanism of infrared emissivity control in YSZ-based ceramics doped with Yb2O3

Due to its exceptional thermal stability and high conductivity, Yttrium stabilized zirconia (YSZ) has become an essential material in the field of infrared camouflage. Although YSZ exhibits relatively low emissivity within the 3–5 μm wavelength range, the increasing operating temperatures of aircraft necessitate further reduction in infrared emissivity within this specific band, in accordance with the Wien displacement law. This study focuses on the preparation of ceramic samples of YSZ doped with varying concentrations of Yb2O3 through a high-temperature solid-state reaction. It aims to investigate the influence of different doping concentrations on the microstructure, crystal structure, and infrared radiation characteristics of YSZ ceramic blocks. The experimental results demonstrated that the addition of Yb2O3 induces changes in the grain size and phase content of YSZ. Notably, as the amount of Yb2O3 doping increases, the infrared emissivity of YSZ samples in the 3–5 μm wavelength range exhibits a pattern of initial decrease followed by an increase. Remarkably, at a doping amount of 3 % mol, YSZ ceramics demonstrated the lowest emissivity, with the average emissivity of the 3–5 μm wavelength range decreasing from 0.41 to 0.38.

Preparation and evaluation of a pyridine sulfonate betaine-based zwitterionic stationary phase for hydrophilic interaction chromatography

A zwitterionic stationary phase comprising pyridinium cations and sulfonate anions was successfully developed through thiol-ene click chemistry. Using seven polar small molecules as probes, the zwitterionic stationary phase showed high separation selectivity and excellent column efficiency (35,200–54,800 plates/m) compared with two commercial columns. The influence of water proportion, salt concentration, and pH in the mobile phase, and column temperature, on the retention of six polar compounds was examined. The retention mechanism was explored by three hydrophilic retention models, Tanaka test and linear solvation energy relationship analysis. For the analysis of sample dairy products (milk powder, milk, and yogurt), the stationary phase was operated in hydrophilic interaction chromatography mode without the addition of buffer salts, facilitating rapid and efficient detection and quantification of melamine. The LOD and LOQ are 0.04 mg⋅g−1 and 0.13 mg⋅g−1, respectively, and the recovery rate is 90.3 − 102.8 %. The zwitterionic stationary phase has the advantages of simple preparation, good method reproducibility, good selectivity and high precision.

The effect of COVID-19 epidemic and sandstorm on distribution of short-, medium-, and long-chain chlorinated paraffins in outdoor atmosphere of Xi'an, Northwest China

The short-, medium- and long-chain chlorinated paraffins (SCCPs, MCCPs, and LCCPs) were measured in outdoor fine particulate matter (PM2.5) and gas-phases in Xi'an in spring, autumn and winter of 2021, which containing two special events during this time, the sandstorms happened in spring and the COVID-19 epidemic in winter. The CPs concentrations in PM2.5 were seasonal variated, with spring (mean: 17.5 ng/m3) > autumn (mean: 8.6 ng/m3) > winter (mean: 5.8 ng/m3). The CPs concentrations in gas phases (mean:12.6 ng/m3) were lower than in PM2.5 in spring, and it showed shorter carbon chain and lower chlorinated CPs dominated in SCCPs in gas phase (C10, Cl5,6) compared with in PM2.5 (C11, Cl6,7). The absorption was the main mechanism for the partitioning of CP in particle and gaseous phase. The shorter carbon chain CPs (C10,11, C14) with lower chlorinated (Cl6,7) CPs dominated in SCCPs and MCCPs, while the longer carbon chain (C25 or C29) with Cl6,12 dominated in the LCCPs. So, more researches about the LCCPs should be concerned. Additionally, the CPs concentrations of all samples during the sandstorms in spring were increased 30.4%–136.5% and the proportion of SCCPs was obviously elevated. CPs concentrations obviously decreased during the COVID-19 epidemic in winter, while SCCPs, MCCPs attributed comparable in autumn and winter. Potential source analysis showed that during the sandstorms in spring, atmospheric pollutants were mainly transported over a long distance from northern and northeast of Shaanxi Province, while it was mainly from local emission during the COVID-19 epidemic in winter. The health risk assessment of CPs displayed that there had no or very low inhalation exposure risks of CPs for all age groups, but the younger age groups (younger than 6 years old) should be played more attention for their not fully development of their immune and respiratory systems.

Characterization of CrMnNi Steel Powders Obtained via Gas Atomization

To obtain a successful product during additive manufacturing, the powder as a raw material must have the high quality. The purpose of this work is to investigate CrMnNi steel powders obtained by inert gas atomization with nickel content: 3, 6, and 9 wt% and to identify dependencies between the powder size and morphology, solidification structure, and change in chemical composition and thermophysical properties. Particle size distribution is measured by a laser scattering analyzer: d50 value are 82.02, 69.32, and 75.54 μm for powders with 3, 6, and 9 wt%, respectively. Surface tension (ST) measurements are made by maximum bubble pressure method: for steels with 3, 6, and 9 wt% at temperature 1500 °C, ST is 1.01, 1.07, and 1.15 mN m−1, respectively. It is found that the change in particle size affects the chemical composition, the content of the ferromagnetic phase and secondary dendritic arm‐spacing. Changes in the content of elements such as S, O, N, and Mn are determined, depending on the diameter of the particles. The influence of changes in content of S, O, and N on the thermophysical properties such as ST is investigated.

Effects of Thermal Exposure Temperature on Room-Temperature Tensile Properties of Ti65 Alloy.

As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the α2 phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, α2 phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO2 oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the α2 phase in the matrix promotes the planar slip of dislocations, while silicides at the α/β phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility.

Effect of P2O5 on the viscous flow and crystallisation behaviour of slag in the double slag converter steelmaking process

In the current study, the effect of P2O5 on the viscous flow and crystallisation behaviour of slag in the double slag converter steelmaking process was investigated in laboratory. The results indicated that with the increase of P2O5 content, the softening temperature, hemispherical temperature and flowing temperature of steelmaking slag showed a decreasing trend, however, the viscosity increased. The FactSage thermodynamic software was used to predict the types and contents of crystallisation phases in the crystallisation process of steelmaking slag. It showed that with the increase of P2O5 content, the precipitation content of Ca5P2SiO12 increased, while the precipitation content of melilite decreased. The composition and microstructure of crystallisation phases were analysed using X-ray diffraction and scanning electron microscopy. The phase composition did not change with the increase of P2O5 content, but the diffraction peak intensity of each crystallisation phase was different. Besides, the precipitation of phosphorus-enriched phase was enhanced with the increase of P2O5 content.

Oil-in-water microemulsion of Arthrospira platensis carotenoid as antiphotooxidation in vitamin C beverages

Arthrospira platensis is a blue-green microalgae that has carotenoid as the main pigments, with the largest content being beta-carotene. Carotenoids are a type of pigment that is water insoluble, unstable, and has a limited bioavailability. One of the efforts to improve its solubility and stability, especially with regard to its anti-photooxidation capabilities, is to make it into a microemulsion. This study aimed to develop the most stable oil-in-water (O/W) microemulsion containing carotenoids from A. platensis for use as an antiphotooxidation agent in vitamin C beverages. Microemulsions consist of three distinct phases: oil, water and surfactant. The oil phase consisted of virgin coconut oil (VCO) or palm oil, with 7.5% and 15% and the aqueous phase was distilled water at a concentration of 65% or 80%. The surfactant used a combination of Tween 80, Tween 20, and Span 80 with a final hydrophilic-lipophilic balance or HLB value of 14.5. All microemulsion formulations were incubated for 24 hrs before being tested for stability by centrifugation at 3000 rpm for 30 mins, heating at 105oC for 5 hrs, and storage for 2 and 4 weeks. The resulting turbidity index was used to test the microemulsion's stability. The most stable microemulsion was chosen as a delivery system for carotenoid compounds. The carotenoid microemulsion was also tested by centrifugation, heating, and stability at different pH (6.5 and 4.2) and in varied ratios (1:1, 1:9 and 1:99). The results revealed that the concentration of oil and water phases in the microemulsion formulation influenced the microemulsion's stability. The best formulation obtained was a microemulsion with 7.5% of virgin coconut oil, 80% of water concentration, and surfactant with a ratio of 92:5.5:2.5 (Tween 80: Span 80:Tween 20). The most stable carotenoid microemulsion was a microemulsion with 100 ppm of carotenoid added. The carotenoid microemulsion was able to inhibit photooxidation at 4000 lux for 4 hrs. The vitamin C beverage model added with 6 ppm carotenoid microemulsion was able to inhibit photooxidation compared to the control and 12 ppm, for up to 6 hrs and there was a significant decrease in vitamin C and antioxidants after 24 hrs of photooxidation. A. platensis carotenoid microemulsion with a concentration of 6 ppm could inhibit photooxidation on vitamin C beverages for up to 6 hrs.

Low Temperature Sintering Al-B Doped-LLZO for All-Solid-State Lithium Battery

This research synthesizes a double Al-B doped LLZO following a composition of Li7+0.5xLa1.14Al1.43xB0.5xZr2-3xO12-δ through a solid-state reaction. The materials were sintered at a low temperature of 900 °C, giving an advantage in reducing Li loss. The material was analyzed to understand the phase content, the crystal structure and cell parameters, the surface morphology, the impedance, the electrical conductivity, and the activation energy for ionic migration. As a result, the Al-B doped-LLZO with x composition of 0.3 (Li7.15La1.14Al0.429B0.15Zr1.1O12-) and ball milling time of 120 h, LLZBAO(0.3)120 h, provides the highest ionic conductivity of 6.898×10–4 Scm–1 at room temperature, and it increases as the temperature increases confirming activation energy of 0.135 eV. A prototype of LCO-LLZBAO(0.3)120h-Li metal battery was produced and tested to investigate the solid electrolyte performance. A cyclic voltammetry analysis confirms a quasi-reversible reaction involving extraction-insertion of Li ions into LiCoO2. However, the excess capacity and a long plateau at low voltage also indicate the reduced Li+ into zero valent-metal, which is poorly reversible, causing the battery capacity to decrease and become stable after 20 cycles.

Development of Ti3SiC2 MAX phase tubular structures for solar receiver applications

Solar receiver tubes are key components of concentrating solar-thermal power (CSP) systems that harvest solar energy. For better efficiency, the Gen3 CSP receivers, which collect heat into a heat transfer fluid, require a temperature exceeding 700 °C during operation and need to perform under extreme conditions of high temperature and high thermal stress. Operators are seeking CSP designs using new high-temperature structural materials with high thermal conductivity and high creep resistance to achieve a design life of 30 years and thus help recover the plant capital cost sooner. MAX phase materials, which consist of an early transition metal element, an A-group element, and carbon or nitrogen, are expected to exhibit high creep resistance as well as high fracture toughness. In this paper, we describe fabricating both (1) dense Ti3SiC2 MAX phase disks and (2) short-length tubes using field-assisted sintering technology (FAST). First, the disk samples that we fabricated are fully dense and contain ≈90 % Ti3SiC2 MAX phase materials and ≈10 % TiC phase materials. We determined a flexure strength of 519 ± 32 MPa by conducting a four-point bending test at room temperature with rectangular bar samples of ≈100 % density. The thermal conductivity of the Ti3SiC2 MAX phase samples, measured by light-flashing analysis, decreases linearly from a value of 41 W·m−1·K−1 at room temperature to a value of 36 W·m−1·K−1 at 650 °C. A solar reflectance measurement of the Ti3SiC2 MAX phase revealed that, temperature increases from 400 to 1400 °C, thermal emittance increases from 0.39 to 0.49, while selectivity decreases from 1.8 to 1.4, respectively. Whereas the surface oxidized MAX phase samples after 100 h exposure to air at 1000 °C exhibit that of SiC.Next, we discuss fabrication of the crack-free Ti3SiC2 MAX phase tubular structures accomplished by using FAST processing in graphite bedding. A Ti3SiC2 MAX phase content of > 95 % with traceable ≈3% remaining TiC phase and ≈15 % porosity were demonstrated after high-temperature annealing. An average fracture strength of ≈250 MPa was determined with Ti3SiC2 MAX phase tubes of ≈85 % density by diametral compression testing at room temperature. Our work demonstrated that using FAST processing to produce Ti3SiC2 MAX phase tubular structures for CSP receiver applications is a viable approach.

The Effect of Nickel Content and Mechanical Activation on Combustion in the 5Ti + 3Si + &lt;i&gt;х&lt;/i&gt;Ni System

Intermetallic alloys were synthesized in the 5Ti + 3Si + xNi system by the method of self-propagating high-temperature synthesis (SHS) and mechanosynthesis. The influence of nickel content on the morphology, size and yield of composite particles after mechanical activation (MA) of mixtures was studied. The dependences of the maximum temperatures and combustion rates, phase composition, morphology and elongation of synthesis products on the nickel content for the initial and MA mixtures are studied. Under the conditions of the experiments conducted in this work, combustion process was able to realize and at the same time the samples burned completely at a nickel content of 10 to 60 wt.% in the 5Ti + 3Si + xNi system. After MA, the samples from the 5Ti + 3Si mixture burned to the end, and during the activation of the 5Ti + 3Si + 40% Ni mixture, mechanochemical synthesis occurred. With increasing nickel content combustion temperature decreases, and combustion velocity behaves nonmonotonically, increases the size of composite particles and decreases the yield of the mixture after MA. MA practically did not affect the maximum combustion temperatures of mixtures of 5Ti + 3Si + xNi. A multiple (from 0.7 to 2.9 cm/s) increase in the burning rate of samples from MA mixtures with an increase in the Ni content from 20 to 30 wt. % was recorded. An increase in the nickel content leads to an increase in the content of triple phases and the amount of melt in the synthesis products of mixtures of 5Ti + 3Si + xNi. Shrinkage of product samples increases with increasing nickel content in the initial mixtures. After MA, the shrinkage of the product samples is replaced by their growth. Explanations of the observed dependencies are proposed.

Research on a Novel Heat Treatment Process for Boron Steel Used for Soil-Engaging Components of Tillage Machinery

To address the issue of high fracture and wear failure rates caused by the lack of toughness and abrasion resistance in the steel used for soil-engaging components of tillage machinery, a novel composite heat treatment process, “normalizing and intercritical quenching and tempering (NIQT)”, is proposed. By regulating the austenitizing heating temperature in the intercritical area (ferrite/austenite two-phase area), the type, content, and distribution of phases in the 27MnCrB5 test sample could be precisely controlled, which further influenced the mechanical properties of the material. The results demonstrated that a multiphase composite microstructure, predominantly consisting of martensite and ferrite, could be obtained in the 27MnCrB5 steel treated by the NIQT process. The results of an EBSD test indicated that the predominant type of grain boundary following the NIQT heat treatment was a high-angle grain boundary (approximately 59.5%), which was favorable for hindering crack propagation and improving the impact toughness of the material. The results of the mechanical tests revealed that, when the quenching temperature was set to 790 °C, the 27MnCrB5 steel attained excellent comprehensive mechanical properties, with a tensile strength of 1654 MPa, elongation of 10.4%, impact energy of 77 J, and hardness of 530 HV30. Compared with conventional heat treatment processes for soil-engaging components, this novel process has the potential to enhance the performance of soil-engaging components and prolong their service life.