Search

As a near-net-shape technology, the twin-roll strip casting (TRC) process can be considered to apply to the fabrication of TiAl alloy sheets. However, the control of the grain distribution is very important in strip casting because the mechanical properties of strips are directly determined by the solidification microstructure. A threedimensional (3D) cellular automation finite-element (CAFE) model based on ProCAST software was established to simulate the solidification microstructure of Ti-43Al alloy. Then, the influence of casting temperature and the maximum nucleation density (nmax) on the solidification microstructure was investigated in detail. The simulation results provide a good explanation and prediction for the solidification microstructure in the molten pool before leaving the kissing point. Experimental and simulated microstructure show the common texture <001> orientation in the columnar grains zone. Finally, the microstructure evolution of the Ti-43Al alloy was analyzed and the solidification phase transformation path during the TSC process was determined, i.e., L → L+β → β → β+α → α+γ+β/B2 phase under a faster cooling rate and L → L+β → β → β+α → γ+lamellar (α2+γ)+β/B2 phase under a slower cooling rate. [ABSTRACT FROM AUTHOR]

Asphalt crack repair materials, known as crack sealants, are directly exposed to ultraviolet (UV) radiation in asphalt pavements. This exposure causes the gradual aging and deterioration of both their surface and internal properties. To study this phenomenon, the sealant was subjected to UV irradiation for a range of 0–385 hours, with the basic properties of the aged sealant tested every 55 hours. Several techniques were employed to investigate the changes in the internal chemical composition of the sealant, including Fluorescence microscopy (FM), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FT-IR). The results revealed that the UV aging of the sealant mainly occurs in the thinner surface layer, which becomes progressively lighter in color. Notably, obvious surface cracks form after aging process. The cone penetration and softening point of the sealant exhibit an exponential or logarithmic change corresponding to the aging time. The most pronounced changes occur during the early stages of UV aging, with the properties tending to stabilize after approximately 220 h of aging. In addition, the FM images showed that the dispersed polymer particles within the sealant gradually transform into a continuous network structure after aging over time. The GPC spectrum of the aged sealant shifts to the left, indicating an increase in molecular weight, particularly in the polymer modifier. This is consistent with the transformation observed in the FT-IR analysis, which demonstrates that UV irradiation leads to the breaking and recombination of polymer chemical bonds in the sealant. The FT-IR analysis reveals the conversion of monosubstituted benzene to polysubstituted benzene in the polymer modifier, which also correlates with the formation of the network structure observed in the FM images and the increase in molecular weight detected in the GPC spectrum of the polymer modifier. • UV aging of the sealant only exists in its surface, and obvious surface cracks appeare after aging. • Cone penetration and softening point changes exponentially or logarithmically with UV aging time. • Polymer particles dispersed in sealant gradually change into continuous network structure after aging. • The styrene of monosubstituted benzene in polymer gradually changes into poly-substituted benzene. [ABSTRACT FROM AUTHOR]

This study explores the hot deformation behavior of Al–Zn–Mg–Cu alloy through uniaxial hot compression (200 °C–450°C) using the Gleeble-1500. True stress–strain curves were corrected, and three models were established: the Arrhenius model, strain compensated (SC) Arrhenius model, and strain compensated recrystallization temperature (RT) segmentation-based (TS-SC) Arrhenius model. Comparative analysis revealed the limited predictive accuracy of the SC Arrhenius model, with a 25.12% average absolute relative error (AARE), while the TS-SC Arrhenius model exhibited a significantly improved to 9.901% AARE. Material parameter calculations displayed variations across the temperature range. The SC Arrhenius model, utilizing an average slope method for parameter computation, failed to consider temperature-induced disparities, limiting its predictive capability. Hot processing map, utilizing the Murty improved Dynamic Materials Model (DMM), indicated optimal conditions for stable forming of the Al–Zn–Mg–Cu alloy. Microstructural analysis revealed MgZn2 precipitation induced by hot deformation, with crystallographic defects enhancing nucleation rates and precipitate refinement. [ABSTRACT FROM AUTHOR]

The design and growth of a new nanowire structure (Cu 2 O micro-nanowire structure) in the three-dimensional frame were studied. After super-hydrophobic modification, the surface has high water collection efficiency. [Display omitted] • The Cu 2 O micro/nano thin wire structure was fabricated. • The employed method is simple and easy. • The surface fabricated shows fog-collecting properties. Fog harvesting is one of the most effective, direct, and low-cost methods to achieve sustainable development of freshwater resources. In recent years, slippery surfaces infused with lubricants have received much attention in terms of mist collection. Inspired by the lubrication characteristics of Nepenthes and guided by previous work experience, more slippery surfaces with structural features need to be studied. In this study, we successfully fabricated the Cu 2 O micro/nano thin wire structure on the surface of the copper foam three-dimensional framework by a simple two-step method. After the injection of dimethylsilicone oil, the smooth surface of the three-dimensional framework with lubricant injection was successfully designed. The fog collection efficiency can reach 0.277 g min−1 cm−2. [ABSTRACT FROM AUTHOR]

Silicon nitride ceramics were prepared by plasma-activated sintering at 1550 °C with 2−5 wt% Mg 2 Si as a sintering agent. The effects of the Mg 2 Si content on the phase, microstructure, and thermal conductivity of the ceramics were studied. Mg 2 Si reacts with SiO 2 to form MgO and Si, benefiting to the transformation and densification of Si 3 N 4. After heat treatment at 1700 °C for 6 h in a flowing N 2 , the residue Si reacted with N 2 and lattice O to form Si 3 N 4 and SiO, resulting in decreases in the grain-boundary phase and lattice O content. After the heat treatment, the sample prepared with 3 wt% Mg 2 Si achieved a relatively good balance between the thermal conductivity and strength, with values of 110 W/(m⋅K) and 705 ± 30 MPa, respectively. [ABSTRACT FROM AUTHOR]

We elucidate the effect of nano-SiC whisker (SiC w) on the microstructure and mechanical properties of Ti6Al4V alloy manufactured by selective laser melting (SLM). The transformation of cross-sectional plate-like α grains and longitudinal-sectional β columnar grains to equiaxed grains could be achieved by adding a trace amount of SiC w , and the weak texture strength microstructure with fine equiaxed grains was obtained. The in situ formed nanosized TiC particles promoted grain refinement through three mechanisms: (i) The diffusion distribution of nanosized TiC particles provided a favorable nucleation position for the α phase, it also limited the growth of the α phase. (ii) Nanosized TiC particles were dispersed to fix dislocations and grain boundaries, inhibit the grain growth. (iii) Nanosized TiC was embedded in the matrix and bound well to the matrix. The Ti matrix was easy to nucleate on some specific crystal planes of primary TiC, which increased the nucleation rate. In addition, the addition of SiC w significantly improved the mechanical properties of Ti6Al4V alloy, compared with that of the Ti6Al4V alloy (360.2 HV), the microhardness of the sample with 1.0-wt% SiC w (522.7 HV) increased by 45.1%. The addition of 0.5-wt% SiC w (1445.34 MPa) increased the ultimate tensile strength by 19.4% compared with that of the Ti6Al4V alloy (1210.13 MPa), and good ductility was maintained. The results show that the microstructure of Ti6Al4V alloy can be significantly improved by adding a trace amount of SiC w , which provided an effective way for the grain refinement of titanium matrix composites manufactured by SLM. [ABSTRACT FROM AUTHOR]

• Ti6Al4V-SiCw composites have evenly distributed equiaxed grains after heat treatment. • Ti6Al4V-SiCw composite limited the formation of coarse columnar grains after heat treatment. • Ti6Al4V-SiCw composites have lower texture strength and reduced anisotropy of material properties after heat treatment. Ti6Al4V alloy and Ti6Al4V-1SiCw composites were manufactured by selective laser melting (SLM), and the effect of solution aging heat treatment on the microstructure evolution was studied. The experimental results show that the Ti6Al4V alloy after heat treatment had many coarse columnar crystals, forming a strong fiber texture. The microstructure of the composite was uniformly distributed equiaxed grains, resulting in a scattered texture distribution, which greatly reduced the anisotropy of the material properties. After heat treatment, the proportion of low-angle grain boundaries in the composite was larger than that of Ti6Al4V alloy, forming a large number of sub-grain boundaries, thus separating the grains and avoiding the formation of coarse columnar grains. In addition, the heat treatment can effectively reduce the dislocation and internal stress produced in the SLM forming process. [ABSTRACT FROM AUTHOR]

Cold-set oat protein isolate (OPI) and gellan gum (GG) binary gels with various microstructures was fabricated with different amounts glucono-δ-lactone (GDL) as a carrier to deliver bioactive compounds. OPI and GG formed gel-like mixture at pH 8 mainly via hydrophobic interactions with a binding constant (K a) of 3.85 × 104 M−1, while the mixture showed highest storage modulus (G′) with 0.1% GG (w/w, based on the dry weight of protein). Novel binary gels fabricated with 7% OPI (w/v) and 0.1% GG (w/w) (OGG) were then developed through addition of various amounts of GDL. For the gels prepared with 1.5% and 4.0% GDL (w/w, based on the dry weight of protein, pH 7.1 and 6.3, respectively), heterogeneous network formed by co-aggregated OPI and GG with a small amount of small GG particles dispersed within large aqueous pores were fabricated mainly through hydrophobic interactions. For OGG-3 (9.0% GDL, w/w) and OGG-4 (20.0% GDL, w/w), the final pH was 5.1 and 4.1 that around or lower than OPI's isoelectric point, hydrogen bonding and electrostatic attractive forces were developed between two polymers since OPI contained neat or positive charges, resulting in a compact coupled OPI-GG network structure. Heterogeneous network with small GG particles dispersed in pores allowed OGG-2 (4.0% GDL, w/w) had comparable good gel hardness to the gel formed with 9.0% GDL (w/w, OGG-3) with coupled microstructure, whereas OGG-3 showed a better ability to restrict the swelling induced release of riboflavin in SGF, and allowed sustainable release of riboflavin in SIF. Therefore, OPI-GG binary gels with various microstructures prepared by simple acidification method at ambient temperature have great potential to be used as delivery systems for heat-sensitive bioactive compounds in food and non-food applications. [Display omitted] • OPI-GG gel formed with 1.5% and 4.0% GDL showed heterogeneous aggregated structure. • OPI-GG gel fabricated with 9.0% and 20.0% GDL showed compact coupled microstructure. • Hydrophobic interactions and slow gelation rate contributed to heterogeneous structure. • H-bonding and electrostatic interactions contributed to compact coupled structure. • OPI-GG gel has capacity to control release riboflavin in simulated gastrointestinal fluids. [ABSTRACT FROM AUTHOR]

In this study, the corrosion behavior and microstructure of the surface corrosion film of WE43 (Mg-4 wt%Y-3 wt%RE) and ZX21 (Mg-2 wt%Zn-1 wt%Ca) Mg alloys immersed in Hanks' balanced salt solution (HBSS) at 37 °C are investigated. Through cross-sectional transmission electron microscopy (TEM) analysis, the surface corrosion films formed on both alloys after immersion in HBSS for 24 h are mainly a mixture of magnesium hydroxide (Mg(OH) 2) and dicalcium phosphate dihydrate (DCPD) (CaHPO 4 ·2H 2 O). Nevertheless, the surface corrosion film on WE43 alloy is only 114 ± 17 nm with Ca and P enriched in the outer portion of the film, while the surface corrosion film on ZX21 alloy is thicker (406 ± 50 nm) with some scattered hollow corrosion products on top of the film. The difference in the surface corrosion film thickness and microstructure is because of the faster corrosion rate of the ZX21 alloy, which resulted from the occurrence of localized corrosion on the alloy surface. • Corrosion behavior and microstructure of WE43 and ZX21 alloys were studied in HBSS. • Surface corrosion film on Mg alloys formed in HBSS was characterized by TEM/STEM/EDS. • Surface corrosion film on Mg alloys formed in HBSS was a mixture of Mg(OH) 2 and DCPD. • Corrosion rate of ZX21 alloy is faster due to the occurrence of localized corrosion. • Surface corrosion film on ZX21 alloy is thicker with hollow corrosion product on top. [ABSTRACT FROM AUTHOR]

Waste Pisha sandstone (WPS) is the main damming material for the check dam in the Loss Plateau of northwest China. The dissolution characteristics of WPS in alkaline solutions were investigated as a basis for studying WPS modification materials and revealing the modification mechanism to further study the pozzolanic activity of WPS and the development of cementitious materials for concrete utilizing WPS. In this paper, WPS was milled and calcined at 600 °C, 700 °C, and 800 °C, respectively. After that, the activated WPS was immersed in 0.05, 0.1, 0.5, 1.0, 2.0, and 5.0 M NaOH solutions for leaching tests. The two curing temperatures of 20 °C and 80 °C were set, respectively. The ion concentration of Si, Al, and Ca in the alkaline solutions was determined using chemical titration, silicon–molybdenum blue colorimetric method, and graphite furnace atomic absorption spectrometry, respectively. After the leaching tests, the residues of WPS were characterized using XRD and SEM-EDS. The results show that the concentration of each ion in the leachate did not increase with leaching time but showed fluctuating variations with leaching time. Mechanochemical activation and thermal activation will promote the dissolution of minerals in alkaline solutions and increase the leaching efficiency of Si. However, the soluble Si in the leachate is not able to generate further gelling-like substances, limited by the total amount of available Ca in the mineral. WPS can dissolve more ions in higher concentrations of a NaOH solution, but the mineral crystallinity of its residue will be reduced. Higher curing temperatures can greatly increase the leaching efficiency of Si in a short time, which is better than thermal activation, and it can also promote the generation of newborn minerals and increase the crystallinity of minerals in WPS after leaching. [ABSTRACT FROM AUTHOR]

The mesoscopic structure of rocks determines their strength and deformation characteristics. The grain and pore size distribution of granite samples buried depth of 1600 m to 1900 m in a goldmine of Shandong Province are measured by polarizing microscope and low-field nuclear magnetic resonance. The splitting test is carried out and the acoustic emission signal is obtained in real time by using an electro-hydraulic servo press and PCI-2 acoustic emission collector. The relationship between meso-mechanics and acoustic emission characteristics of split granite is analyzed. The experimental result shows that there is no clear correlation between meso-grain size and pore size distribution. Rocks with larger mineral grains easily form inter-embedded structures between grains and grains, the bearing effect of grains is enhanced, and the tensile strength of rocks is improved. The level of stress concentration in the rock is closely related to the pore size of the rock, and the acoustic emission ringing count before the main rupture in the large aperture (0.1~10 mm) of the rock is more active than that of the small aperture rock (0.01~1 mm), and a large number of high frequency acoustic signals are induced by the penetration between the pores in the unstable failure stage and post-peak failure stage, the stress concentration is higher, and the energy release frequency is increased, however the energy released strength by a fracture is weak. [ABSTRACT FROM AUTHOR]

• The Fe-Cr-Ni based composite coating was prepared using laser cladding method. • The addition of rare earth elements makes the cladding layer more dense and more refined. • Increased tensile strength, increased yield strength and increased impact value. Laser cladding technology was used to prepare Fe314 coating with added CeO 2 and La 2 O 3 on the surface of EA4T steel. The microstructure and structure of the coating were analyzed using scanning electron microscopy, electron probe microanalyzer, and X-ray diffraction. The mechanical properties of the coating were tested using a microhardness tester, universal testing machine, and pendulum impact testing machine. The results show that the addition of rare earth elements makes the cladding layer more dense and more refined; at the same time, compared to the base material, the tensile strength of the repaired specimen increased by 12.9 %, the yield strength increased by 23.3 %, and the impact value increased by 43.6 %. [ABSTRACT FROM AUTHOR]

• AlMo 0.5 NbTa 0.5 TiZr alloy was prepared by laser-directed energy deposition (L-DED). • The L-DED and vacuum arc melting (VAM) alloys were compared for the first time. • The L-DED alloy has a higher microhardness than the VAM alloy. In this study, the AlMo 0.5 NbTa 0.5 TiZr alloy was successfully manufactured by laser-directed energy deposition (L-DED) using element powder blends. The microstructure and mechanical properties of the L-DED alloy have been compared with the alloy prepared by vacuum arc melting (VAM). The L-DED alloy consists of rod-shaped equiaxed dendrites. The interdendritic HCP phase content of the L-DED alloy is much higher than that of the VAM alloy. The L-DED alloy has the same superior high-temperature strength as the VAM alloy. Due to the precipitation strengthening, the microhardness of the L-DED alloy has a better performance than the VAM alloy. [ABSTRACT FROM AUTHOR]

The porous hydrophilic nature of cement-based material is susceptible to water and corrosive media, severely reducing the durability. In this paper, methyl siloxane-based hydrophobic powder was prepared, and its effect on the physicochemical and anti-corrosion properties of mortar with different water-cement ratios were investigated. The results show that the addition of hydrophobic powder significantly improved the hydrophobic properties of mortars. Especially for the mortars with w/c ratios of 0.2 and 0.4, it showed superhydrophobicity with a water contact angle up to 156.5 ° and 152.3 ° respectively. Lower w/c ratio mortar has a denser microstructure, which reduces the water absorption rate of the mortar, and the hydrophobic powder enhances the hydrophobic effect of low w/c ratio mortar more significantly. The methyl siloxane groups in the hydrophobic powders will bind to the C-S-H gel in the mortar through Si-O bonding, preventing the C-S-H gel connections from forming a continuous network structure. This increased the pore volume and reduced the compressive strength by 14.6%-22.7%, but the total hydration degree was increased, and significant corrosion protection of the steel rebar was demonstrated. [Display omitted] • Super hydrophobicity of mortar was achieved by modification of hydrophobic powder. • Hydrophobic mortar with lower w/c ratio exhibits better anti-corrosion performance. • Methylsiloxane groups combine with C-S-H gel by Si-O enhancing hydrophobic properties of mortar. [ABSTRACT FROM AUTHOR]

[Display omitted] • The MoNbTaWTi-based refractory high entropy alloy coatings by laser cladding. • TiN/(Nb, Ti) 5 Si 3 particles were in-situ synthesized by adding nano-Si 3 N 4. • The high-entropy alloy coating structure primarily consisted of BCC, TiN, and (Nb, Ti) 5 Si 3 phase. • The Si 3 N 4 -2.0 coating exhibits the best wear resistance with an average hardness of 628.07 HV 0.1. MoNbTaW Refractory High Entropy Alloy (RHEA) coating has caught the extensive interest of researchers due to its simple body-centered cubic structure and excellent room temperature plasticity. However, it is difficult to prepare refractory high-entropy alloy coatings by laser melting due to its high melting point. In this study, MoNbTaWTi (Si 3 N 4) x: (weight ratio; x = 0.5, 1.0, 1.5 and 2.0) RHEA composite coatings were fabricated by laser cladding on the Ti-6Al-4V alloy. The experimental results show that laser cladding may produce TiN/(Nb, Ti) 5 Si 3 ceramic particles and BCC phases in- situ in the coating when nano-Si 3 N 4 is added. Moreover, the in-situ reaction between element Ti and element N in the molten pool can be release a large amount of heat, which can efficiently facilitate the synthesis of RHEA coating. The in-situ generated TiN/(Nb, Ti) 5 Si 3 ceramic particles significantly increase the hardness and wear resistance of the composite coatings. The influence of the content of Si 3 N 4 on the ceramic morphology, microstructure, microhardness, and tribology of RHEA coatings was comprehensively evaluated. [ABSTRACT FROM AUTHOR]

Large animal model of optic nerve (ON) injury is an essential tool for translational medicine. Perfusion fixation with paraformaldehyde is mainly used for preparing the semi-thin (1–2 μm thick) and ultra-thin (<0.5 μm thick) sections of the ON tissues. However, this conventional fixation technique in large animals needs a large volume of fixatives, which increases the risk of toxic exposure and is environmentally unfriendly. Additionally, fixed residual ON cannot be used for other tests that require fresh tissue samples. Although conventional immersion fixation is feasible for preparing a semi-thin section of the ON in small animals (0.2–0.6 mm in diameter), it faces technical challenges when fixing the ON of large animals (3 mm in diameters), as increased diameter limits the permeability of the fixatives into deeper tissue. Therefore, we optimized the immersion-fixation method to obtain high-quality, large-scale, semi-thin, and ultra-thin sections for the ON of goat and rhesus macaques. Using this optimized technique, the ON microstructure was well preserved throughout the entire area of 1.5*1.5 square millimeters, allowing confident quantification of axon density/diameter on semi-thin section and identification of specific organelles and glial cells on ultra-thin sections. Furthermore, the optimized technique is a quick, simple, and environmentally friendly fixation method. Notably, the ON regions of large animals with or without an intact neurovascular system can be prepared for light and electron microscopy. In contrast, the residual unfixed ON from the same animal can be further utilized for experiments such as tissue culture and biomolecular tests. • The optimized procedure with immersion fixation circumvents the drawbacks of perfusion fixation in large animals. • Large scale, high-quality semi-thin sections of the optic nerve in goat and rhesus macaque were obtained. • Identification of organelles and glial cells can be made on the ultra-thin sections of the optic nerve from large animals. [ABSTRACT FROM AUTHOR]

The present work is aimed to investigate the influences of arc current on the microstructure evolution of the as-deposited Cr coatings for accident tolerant fuel. Cr coatings were prepared on the surface of Zr-4 alloy by multi-arc ion plating with different arc currents. Electron backscattering diffraction (EBSD) technology was employed to characterize the microstructure evolution of the as-deposited Cr coatings, including the distribution of grain boundaries, the mean grain size, the crystallographic orientation distribution, the dislocation density and dynamic recrystallization (DRX). The results showed that: regarding the mean grain size of the Cr coating, the largest was that prepared by 80A, followed by 100A, 70A and 90A; regarding the number fraction of HAGBs, the highest was that prepared by 80A, followed by 90A, 100A and 70A; regarding the grain morphology, the Cr coating prepared by 70A exhibited equiaxed grains without obvious texture, while that prepared by 80A, 90A and 100A had elongated columnar grains along the building direction; regarding the crystal phase, the Cr coating prepared by 80A, 90A and 100A exhibited the (100)〈001〉 texture component; regarding the dislocation density, there was a large number of scattered high dislocation density regions in the Cr coating prepared by 70A, the high dislocation density regions only appeared on the surface layer in the Cr coating prepared by 90A, and along the boundaries of elongated grains in the Cr coating prepared by 100A, while it was almost non-existent in the Cr coating prepared by 80A; regarding the DRX, discontinues DRX (DDRX) was the principal DRX mechanism for the Cr coating prepared by 70A, while continues DRX (CDRX) was the dominant DRX mechanism for the Cr coatings prepared by 80A, 90A and 100A. • The microstructure of Cr coatings prepared by different arc current is characterized by EBSD. • The effect of arc current on the microstructure evolution is studied. • The DRX mechanism of Cr coatings prepared by different arc current is investigated. [ABSTRACT FROM AUTHOR]