High Melting Point Research Articles

Development of an eco-fractionation process for Ricinodendron heudelotii oil to obtain α-eleostearic acid and β-eleostearic acid

Abstract The present article studies the transformations and fractionation of the reserve lipids of Ricinodendron heudelotii. The native triglycerides of this oil are composed mainly of conjugated polyunsaturated fatty acids, in particular α-eleostearic acid C18:3 n– 5 (9c, 11t, 13t) at 60%. This particular fatty acid of CLnA family exerts many activities potentially beneficial for health: anti-inflammatory, anti-leukemic, anti-microbial, anti-tumor, anti-ulcer and anti-diabetic. A process for transforming this acid into its isomers β-eleostearic acid and catalpic acid was explored with the aim of obtaining fractions enriched in β-eleostearic acid C18:3 n– 5 (9t, 11t, 13t). The β-eleostearic acid is a fatty acid of great interest because it is even more reactive and more efficient as antioxidant than α-eleostearic acid due to its higher trans content. Isomerization reaction of α-eleostearic acid in oil was carried out using artificial solar radiation treatment. The enrichment of concentrates in β-eleostearic acid was therefore tested using an eco-fractionation process. This process was carried out in two stages. The first step was the Candida rugosa lipase-catalyzed hydrolysis of triglycerides from native or isomerized Ricinodendron heudelotii oil. The second step was fractionation of the reaction medium obtained after hydrolysis. Triglyceride hydrolysis was complete, with a yield of free fatty acids of over 95% after 2 h of reaction. Treatment of the reaction media yielded 3 lipid concentrates with new chemical compositions of polyunsaturated fatty acids: a first concentrate, derived from hydrolysis of the native oil, composed of 60% α-eleostearic acid and 22% linoleic acid, and two other concentrates derived from fractionation of the hydrolysate of the oil isomerized by radiation. One was composed of 34% linoleic acid, 21% β-eleostearic acid, 11% α-eleostearic acid and 6% catalpic acid, and the last concentrate was composed of over 80% β-eleostearic acid. In addition to offering nutritional benefits similar to those of α-eleostearic acid, β-eleostearic acid also offers an interesting physical property: a very high melting point of 72 °C. Such a polyunsaturated fatty acid, which is solid at room temperature, could prove to be a raw material of choice, particularly in the world of food formulation, where manufacturers are looking for replacements with physical properties close to those of palm oil (the melting point of palmitic acid is 62 °C). Ricinodendron heudelotii oil has thus demonstrated its major role as a source of the triptych of α-eleostearic, β-eleostearic and linoleic fatty acids.

Utilization of Alternative Fibres Manufactured from Recycled PET Bottles in Concrete Technology for the Improvement of Fire Resistance

This article addresses the potential use of secondary polymer fibres in the field of structural concrete as a replacement for primary polymer fibres (mainly polypropylene/PP/), which are used in concrete to enhance its resistance when exposed to high temperatures (especially in the case of fire). Research has shown that, in addition to PP fibres, polyethylene terephthalate/PET/fibres, produced by recycling packaging materials (mainly PET bottles), can also be used as an alternative. These fibres are industrially produced in similar dimensions as PP fibres and exhibit similar behaviour when added to fresh and hardened concrete. In terms of their effect on increasing resistance to extreme heat loads, it has been found that despite a higher melting point (Tm), concrete with these fibres demonstrates comparable fire resistance. Therefore, it can be concluded that secondary PET fibres represent an interesting alternative to primary PP fibres from the perspective of a circular economy, and their use in construction represents a potentially valuable application for PET obtained through the collection and recycling of PET packaging materials.

Utilizing High Melting Point Long-Chain Fatty Acid Based CO2 Response ILs for Suppression of CO2 Gas Channeling and Clay Swelling

Utilizing High Melting Point Long-Chain Fatty Acid Based CO₂ Response ILs for Suppression of CO₂ Gas Channeling and Clay Swelling

A DFT exploration of the stabilities, physical properties, and tensile strength of new synthesized Nb2AC (A=Ni and Co) MAX phases

Based on first-principles calculations, this study explored the structural stability, elastic anisotropy, tensile strength, and the mechanical, electronic, and thermodynamic properties of the newly synthesized MAX phases Nb2NiC and Nb2CoC. It has been found that these compounds are thermodynamically and mechanically stable, exhibit metallic conductivity, and possess ductile nature. The ultimate tensile strengths of Nb2NiC and Nb2CoC depend on their crystallographic directions, specifically [0001] and [112̄0]. In the [0001] direction, Nb2CoC has a tensile strength of about 36.63 GPa at a strain of 26%, compared to Nb2NiC, which has a tensile strength of 31.70 GPa at a strain of 24%. In the [112̄0] direction, Nb2CoC exhibits a tensile strength of around 23.29 GPa at a strain of 12%, while Nb2NiC has a tensile strength of approximately 18.51 GPa at an strain of 8%. Both Nb2CoC and Nb2NiC demonstrate significant elastic deformation before reaching their ultimate tensile strengths, indicating good ductility. It is noteworthy that Nb2NiC is less elastic than Nb2CoC in both the [0001] and [112̄0] directions, as the elastic constants of Nb2CoC are comparatively higher than those of Nb2NiC. Furthermore, the estimated thermal parameters show that these compounds exhibit a relatively low Debye temperature, a high melting point, low minimum thermal conductivity, and thermal expansion coefficient values that are similar to those of well-established thermal barrier coating (TBC) materials such as Al2O3, LaPO4, and TiO2. Consequently, the newly synthesized MAX phases Nb2NiC and Nb2CoC are promising candidates for TBC applications.

Designing dicationic organic salts and ionic liquids exhibiting high fluorescence in the solid state

Dicationic ionic liquids (DILs) are emerging as a powerful, next-generation approach to designing applied ILs because of their superior physicochemical properties as well as their diverse complexity and tunability for task specific applications. DILs are scarce in the literature compared to monocationic ILs (MILs), and one of their main issues is their expected tendency to possess higher melting temperatures. A series of 1,4-bis[2-(4-pyridyl)ethenyl]benzene and 1,4-bis[2-(2-pyridyl)ethenyl]benzene quaternary salts (Q-BPEBs) with different counterions (bromide, tosylate, and triflimide) and carbon chain lengths (C6, C9, and C12) have been synthesized for their potential as DILs with thermal properties and strong photoluminescent properties in the solid state. All Q-BPEB salts demonstrated robust thermal stabilities as determined by thermogravimetric analysis (TGA). The differential scanning calorimetry (DSC) thermograms for Q-BPEB tosylates and triflimides displayed crystalline polymorphisms before melting transitions as verified by polarizing optical microscopy (POM). The Q-BPEB bromide and tosylate salts all showed high melting points of above >170 °C because of their dicationic rigid structures and strong ionic interactions of their anions. Once the Q-BPEB tosylates were exchanged with triflimide ions, para- isomers 1aTf2N-1cTf2N still possessed very high melting points (>225 °C), however, the ortho- isomers 2aTf2N, 2bTf2N, and 2cTf2N exhibited melting points lower than 100 °C, classifying them as DILs. Their photoluminescent properties were also studied in methanol with the emission values of λem = 476-482 nm for the para- isomers and those of λem = 448-453 nm for the ortho- isomers. In the solid state, the Q-BPEB salts exhibited strong fluorescence with quantum yields of up to 50%. The relatively simple synthesis of these fluorescent dicationic organic salts and ILs are pertinent towards the scarcity of these materials in the literature and provide a deeper insight on the design of fluorescent ILs containing more than one charge center.

Simultaneous fluoridation strategies for achieving high thermionic emission and low melting point in aluminate impregnants for Ba-W cathodes

Simultaneous fluoridation strategies for achieving high thermionic emission and low melting point in aluminate impregnants for Ba-W cathodes

Improving strength and plasticity via pre-assembled dislocation networks in additively manufactured refractory high entropy alloy

Refractory high entropy alloys (RHEAs), as a novel class of multi-principal element alloys, have attracted significant attention owing to their excellent properties. However, their low plasticity limits their potential applications, while the high melting points of the alloying elements face challenges to additive manufacturing (AM). Herein, RHEA, with extensively distributed cellular structure within their grains, was successfully fabricated using AM. Furthermore, we proposed a simple strategy to form a complete dislocation network within the cellular structure region in advance through cyclic deformation processing in the elastic stage (microplastic deformation). Dislocation networks are entangled with other dislocations, creating numerous pinned points adjacent cell walls, which impede dislocation motion. As a result, the cyclic deformation processing of RHEA achieves a yield strength of 1136 MPa while maintaining 50% deformation strain without fracturing. The cyclic deformation processing method provides a route to strengthen additively manufactured alloys, offering a solution to overcome the trade-off between strength and plasticity.

High-entropy engineering improved the corrosion resistance of rare earth tantalates

High-entropy RETa3O9 ceramics have garnered significant interest in materials science due to their impressive high melting points and lower thermal conductivity. This study focuses on three types of these ceramics: (La0.2Ce0.2Nd0.2Sm0.2Dy0.2)Ta3O9, (La0.2Ce0.2Nd0.2Sm0.2Tm0.2)Ta3O9, and SmTa3O9.The results indicate that the coefficient of thermal expansion (TEC) for RETa3O9 ceramics remains in the range of approximately 5.94×10-6 K-1 to 6.05×10-6 K-1 when subjected to temperatures from room temperature up to 1400°C. This TEC is notably similar to that of silicon carbide ceramic matrix composites (SiC-CMC), which is essential for compatibility in applications where these materials are used together.Moreover, the study highlights an important finding: after 20 hours of exposure to a CMAS (calcium-magnesium-alumino-silicate) environment at 1300°C, the high-entropy tantalates exhibit significantly reduced susceptibility to corrosion compared to traditional single-component tantalate ceramics. While single-component materials, including SmTa3O9, showed greater degradation, the high-entropy RETa3O9 ceramics maintained their original morphology, free from porosity and cracking.This impressive resistance to CMAS corrosion indicates that the high-entropy design is beneficial in enhancing the durability of tantalates in extreme environments. Consequently, these findings suggest that high-entropy RETa3O9 ceramics hold promise for use as thermal/environmental barrier coating (T/EBC) materials in applications involving SiC-CMCs, potentially leading to improved performance and longevity in high-temperature applications.

Effects of La2Ce2O7 on the phase composition, microstructure, wetting behaviour and corrosion resistance of magnesia refractory

The addition of rare earth oxides has a significant impact on the improvement of thermal properties of refractory materials. Magnesia refractory with La2Ce2O7 was prepared by high-temperature solid-phase synthetic sintering at 1873 K for 5h using fused magnesia as raw materials, CeO2 and La2O3 as addition, respectively. The effect of La2Ce2O7 on the phase composition, microstructure, apparent porosity, bulk density, wetting behaviour and corrosion resistance with steel of fused magnesia were investigated. When the content of La2Ce2O7 was 20wt%, the results showed that as-prepared samples from fused magnesia with an apparent porosity of 17.63% and a bulk density of 3.11g·cm-3 were obtained by high temperature solid-phase sintering reaction at 1873 K for 5h, respectively. Due to the addition of La2Ce2O7, and raw materials in the impurity phase CaO and SiO2 for the reaction, the generation of a small amount of CaLa4(SiO4)3O and La8.89Si6O25.9 high melting point phase, plugging the air holes, thus improving the bulk density of the fused magnesia and reduce its apparent porosity. The ability of steel corrosion of as-prepared samples from fused magnesia doped with La2Ce2O7 have better resistance than conventional fused magnesia, which the thickness of the corrosion layer was reduced by 42.1% compared to as-prepared samples without La2Ce2O7.

The effect of CD4 injection on WD molecule sputtering at the divertor target in EAST

Tungsten (W) is one of the preferred plasma-facing materials for future fusion reactors because of the advantages of high melting point, low physical sputtering rate and low fuel retention. The lifetime and service performance of W materials are limited by erosion processes. In recent years, tungsten deuteride molecular (WD) sputtering has been discovered in tokamak. Studying WD sputtering helps to better understand the erosion of tungsten materials in tokamak. EAST adopts the method of injecting impurity gas in the divertor to alleviate the particle flux and heat flux bombarding the tungsten divertor, and CD4 is one of the impurities used. CD4 injection experiments on EAST show that after CD4 is injected from the upper outer (UO) divertor target, despite that the electron temperature (Te) around the strike point on the UO divertor target drops to about 8 eV, strong WD sputtering occurs in the far scrape-off layer (SOL) region. The divertor probe data shows that after CD4 injection, the particle flux from the upstream plasma onto the divertor split into two bands, creating a new particle flux strike point in the far SOL region. The energy of incident particles at the original strike point is significantly reduced, while the energy of incident particles at the far SOL region is enhanced. The edge electron density profile at mid-plane indicates that CD4 injection causes an increase of density in the SOL, which could improve the coupling of Lower-Hybrid Wave (LHW) with the edge plasma as evidenced by the decreasing reflected power of LHW. The increase in absorbed power of LHW could change the particle and energy transport in the edge plasma, thus plays an important role in the enhanced WD sputtering in the far SOL region after CD4 injection.

Promoting transparency: Defect-driven sintering of Gd2Zr2O7 ceramics for advanced radiation applications

Transparent Gd2Zr2O7 (GZO) ceramics show significant potential for radiation detection and nuclear energy applications. However, scalable production through cost-effective solid-state vacuum sintering is challenging due to the material's high melting point and low thermal conductivity. This study introduces a novel approach by incorporating excess Gd to increase lattice defects, such as cation disorder and oxygen vacancies, which have low formation energy. This strategy lowers the energy barrier for ion diffusion, enhances material migration during sintering, and promotes the elimination of residual pores, leading to high densification. We examined the densification behavior of GZO compositions with varying Gd content (Gd1.8Zr2O6.7 to Gd2.5Zr2O7.75) during vacuum sintering at 1450°C to 1900°C, focusing on phase transformation, grain growth, and pore elimination. Notably, the optimal sample achieved 78.3 % transmittance, approaching the theoretical maximum. These findings offer a promising route for the large-scale production and commercialization of transparent GZO ceramics for advanced radiation applications.

Investigation on titanium wire melting through high-frequency induction heating for additive manufacturing process

ABSTRACT A high-frequency induction heating (HFIH) system is a novel and clean heat source that can potentially melt high melting point material to develop the wire feed-based additive manufacturing (AM) process. The present study establishes the optimised coil parameters, including coil geometry for melting the titanium wire using induction heating. A fully coupled electromagnetic-thermal-fluid flow model is established to analyse the temperature profile of the wire. The wire feed velocity (0.012 m/s) is incorporated in the coupled model using the deformed mesh method. Optimised wire diameter and coil parameters, such as a three-turn helical coil with a circular cross-section, coil turn spacing of 1.5 mm, and a coupling distance of 4 mm, melt the 3.6 mm titanium wire rapidly and create the molten droplet. The results suggest that the optimised coil parameters improve the magnetic flux density, which enhances joule heating in the wire. However, the conical-spiral coil geometry of the three-turn fails to melt the wire completely. In contrast, the helical coil of the three-turn melts the wire completely. The maximum velocity of the molten metal is found as 0.25 m/s. Effectively, the heat transfer and material flow analysis drives to develop the potential additive manufacturing system.

On the Electrochemical Properties of Poly(Vinylidene Fluoride)/Polythiophene Blends Doped with Lithium‐Based Salt

AbstractIn this study, polymer blends of polythiophene (PTH) and poly(vinylidene fluoride) (PVDF) are investigated by focusing on their structural and electrochemical characteristics. These blends displayed immiscibility confirmed through field emission scanning electron microscopy (FE‐SEM) and interaction assessments. PTH's role as a plasticizer is evident, diminishing crystallinity. A rise in PTH level led to a lower glass transition temperature and a higher melting point, suggesting reduced intermolecular forces and increased polymer chain flexibility. Conversely, a dispersed phase presence elevated the melting point, restricting chain movement and crystallization. The thermal properties of blends are enhanced by increased PTH content. Applying the Vogel–Tammann–Fulcher model to ionic conductivity measurements, it observed a direct relationship between temperature and free volume, impacting conductivity and ion transport numbers. Certain materials exhibit increased activation energies, indicating substantial thermodynamic barriers to local motion. Higher PTH content within the PVDF matrix notably increased the lithium ion transfer number from 0.22 to 0.71, a change tied to the C–S–C structure of polythiophene. However, elevated PTH levels also led to diminished negative charge transfer and ionic conductivity in the PTH‐PVDF blend compared to pure PVDF, likely due to an ionic conduction hindrance.

Study of mechanical and thermophysical properties of Ni3Ti

Abstract This research assesses the thermophysical and ultrasonic characteristics of the intermetallic compound Ni3Ti, which has a hexagonal crystalline structure. The selected material exhibits many noteworthy characteristics, including the shape memory effect, a high melting point, extremely elastic qualities, etc. The Lennard-Jones potential model has been used to calculate the higher-order elastic constants. The mechanical properties of the material, which provide details regarding its stability and intrinsic qualities, are computed using the second-order elastic constants. Additionally, we have computed the thermal conductivity at 300 K, specific heat, ultrasonic velocities, and Debye temperature. Ultimately, the ultrasonic attenuation is determined using all of the available parameters. The obtained results agree with the data available in the literature.

Predicting potential hard materials in Nb[sbnd]B ternary boride: First-principles calculations

To identify potential superhard materials, we conducted a comprehensive theoretical investigation of the thermodynamic and kinetic stability, mechanical properties, electronic structure, Debye temperatures and melting point of sixteen ternary transition metal borides NbTMBx (x = 1, 2, 4 and TM = Ti, V, Fe, Co, Ni, Zr, Ru, Hf, W, Os) using first-principles methods. Our findings indicate that, with the exception of NbFeB, NbRuB, and NbWB, all other borides exhibit both thermodynamic and kinetic stability. Notably, NbTiB4, NbVB4, NbZrB4 and NbHfB4 demonstrate superior hardness and enhanced resistance to deformation, with NbTiB4 showing an impressive hardness value of 40.84 GPa, positioning it as a promising candidate for superhard materials. Both NbVB4 and NbTiB4 have very high Debye temperatures and melting points and can be used in high temperature environments. We further explored the mechanical properties of NbTiB4 at elevated temperatures by employing a combination of first-principles and quasi-static methods. Our analysis reveals that the elastic constants and moduli of NbTiB4 decrease with increasing temperature. Additionally, bonding analysis indicates that all NbB ternary borides exhibit hybridization involving metallic, ionic, and covalent interactions, resulting in the formation of exceptionally strong covalent bonds between boron atoms.

Nonstoichiometry Promoted Solventless Recrystallization of a Thick and Compact CsPbBr3 Film for Real-Time Dynamic X-Ray Imaging.

Inorganic CsPbBr3 perovskite emerges as a promising material for the development of next-generation X-ray detectors. However, the formation of a high-quality thick film of CsPbBr3 has been challenging due to the low solubility of its precursor and its high melting point. To address this limitation, a nonstoichiometry approach is taken that allows lower-temperature crystallization of the target perovskite under the solventless condition. This approach capitalizes on the presence of excess volatile PbBr2 within the CsPbBr3 film, which induces melting point depression and promotes recrystallization of CsPbBr3 at a temperature much lower than its melting point concomitant with the escape of PbBr2. Consequently, thick and compact films of CsPbBr3 are formed with grains ten times larger than those in the pristine films. The resulting X-ray detector exhibits a remarkable sensitivity of 4.2 × 104 µC Gyair -1 cm-2 and a low detection limit of 136 nGyair s-1, along with exceptional operational stability. Notably, the CsPbBr3-based flat-panel detector achieves a high resolution of 0.65 lp pix-1 and the first demonstration of real-time dynamic X-ray imaging for perovskite-based devices.

A First-Principles Study of the Structural and Thermo-Mechanical Properties of Tungsten-Based Plasma-Facing Materials

Tungsten (W) and tungsten alloys are being considered as leading candidates for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for the design of magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield, and low long-term disposal radioactive footprint. Despite these relevant features, there is a lack of understanding of how the structural and mechanical properties of W-based alloys are affected by the temperature in fusion power plants. In this work, we present a study on the thermo-mechanical properties of five W-based plasma-facing materials. First-principles density functional theory (DFT) calculations are combined with the quasi-harmonic approximation (QHA) theory to investigate the electronic, structural, mechanical, and thermal properties of these W-based alloys as a function of temperature. The coefficient of thermal expansion, temperature-dependent elastic constants, and several elastic parameters, including bulk and Young’s modulus, are calculated. Our work advances the understanding of the structural and thermo-mechanical behavior of W-based materials, thus providing insights into the design and selection of candidate plasma-facing materials in fusion energy devices.

Controlled Growth of Single-Walled Carbon Nanotube Films by Iron-assisted Floating Solid Catalyst Chemical Vapor Deposition.

Single-walled carbon nanotube (SWNT) films, with exciting electronic properties are increasingly important for next-generation technologies. Here, an Iron-assisted floating solid catalyst chemical vapor deposition (IA-FSCCVD) method is developed for the controlled growth of high-quality and high-purity SWNT films. Titanium carbide nanoparticles with a high melting point are used as the solid catalysts, which provide a stable template for SWNT growth through the perpendicular growth mode. Trace amounts of iron are introduced to increase the efficiency of SWNT growth. Gas chromatography measurements and density functional theory show that the gas-phase iron acts as a pre-cracking assistance for the carbon source, promoting the growth of SWNTs. Carbon nanotube films with a high quality (average IG/ID = 166) are successfully prepared, a small diameter deviation (mean diameter of 1.6nm), and a high content of SWNTs (97%) using the IA-FSCCVD platform. This work provides a powerful way to prepare the carbon nanotube aggregates with a controlled structure.

Ring‐opening copolymerization of ε‐caprolactone and δ‐valerolactone to cyclic polyesters by a bimolecular system

AbstractBio‐based plastics have received much attraction because they are an alternative to petroleum‐based plastics in recent years. Among them, aliphatic polyesters have garnered the most attention due to their excellent properties. Polyester is primarily synthesized through ring opening polymerization of monomer, and the catalysts used are mostly synthesized through “click” reaction in the laboratory, which exhibits inferior activity and little commercial value. Herein, a facile approach was developed for the synthesis of high molecular‐weight cyclic aliphatic polyesters, specifically poly(valerolactone‐co‐caprolactone) with varying compositions. This involved the ring‐opening copolymerization of ε‐caprolactone (ε‐CL) and δ‐valerolactone (δ‐VL) in the absence of an initiator with commercial hydrogen bond donor triclorocarban and an organic base. The structure and properties of the prepared cyclic polyester were investigated using GPC, 13C NMR, 1H NMR, MALDI‐TOF mass spectrometry, TOF‐SIMS mass spectrometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD) techniques. The results show that the molecular weight of cyclic polyester can rapidly exceed 40 kDa, with a PDI of approximately 1.10. In comparison to linear polyester, it has a higher melting point and superior thermodynamic properties, thus presenting greater application potential. Finally, based on nuclear magnetic resonance titration, the potential catalytic processes and mechanisms of bimolecular systems on monomers in different environments were discussed. This study not only offers new insights into the structure and properties of cyclic polyesters, but also presents novel bimolecular catalytic systems using commercial urea hydrogen bond donors for the synthesis of cyclic polymer polyesters.

Highly Refractive Transparent Half‐Heuslers for Near Infrared Optics and Their Material Design

AbstractAdvanced control of light focusing, reflection, and transmission is possible with highly refractive transparent materials; however, such materials are difficult to discover because of the negative correlation between the refractive index and the optical band gap. This study elucidates half‐Heuslers as highly refractive transparent materials, considering their densely packed crystal structures comprising both covalent and ionic bonds with d orbitals. Theoretical calculations revealed that 22 ternary half‐Heusler systems (αβγ) exhibited higher refractive indices with wider band gaps than conventional high‐refractive‐index‐transparent materials in the near‐infrared region. The key to achieving a high index and wide gap is aligning α‐d and β‐d levels within a small lattice frame given by small γ elements to the verge of forming Γ‐point conduction band minimum. Experimental examinations revealed that α and γ elements with low and high melting points are preferred for the thin‐film preparation of the well‐ordered half‐Heuslers. Highly refractive transparent half‐Heuslers and their material designs expedite post‐silicon technology for controlling near‐infrared light.