Search Results (62)

With the increasing demand for premium-quality aluminum alloy castings that can be used as safety-critical structural components, as well as the rising urge to utilize sustainable materials during the manufacturing process, novel technologies need to be developed and implemented during the treatment of liquid alloys. Impurity and alloying elements accumulate in recycled aluminum alloys, which frequently results in the formation of coarse intermetallic compound (IMC) particles in the microstructure that have a detrimental effect on the ductility of cast products. One successful approach to alleviate this negative effect relies on affecting the phase selection and refinement of IMC phases. A growing body of literature has shown that the crystallization process of IMCs is affected by the native oxide phases present in the liquid alloys. It has also been demonstrated that by appropriate technologies, harmful oxide inclusion (like oxide bifilms) can be transformed into small-sized oxide particles that can be dispersed throughout the liquid alloy to serve as heterogeneous nucleation sites for different phases. In this way, the adverse effects of oxide inclusions and IMCs are simultaneously mitigated. This contribution aims to review the recent progress of experimental and theoretical work related to intermetallic particle refinement by oxide phases. Emerging technological solutions capable of refining intermetallics through transforming harmful oxide inclusions into numerous, well-dispersed heterogeneous nucleation sites are comprehensively reviewed. Besides analyzing the current state of these techniques, this discussion evaluates their future implications and the potential challenges that may arise in their application and development. Full article

Phytosterol exhibits cholesterol-lowering, cardiovascular-protecting, anti-inflammatory, and anticancer efficacies but has low bioavailability due to its high melting point and poor solubility. Esterification with fatty acids enhances liposolubility, improving absorption and utilization fivefold. Industrial production of phytosterol esters mainly relies on chemical synthesis, which faces challenges in separation, purification, and quality assurance due to side reactions. Enzymatic synthesis, featuring mild conditions, environmental friendliness, and high selectivity, has gained attention from academia and industry. Candida rugosa lipase (CRL) is widely utilized due to its high efficiency in catalyzing the esterification of phytosterol. Natural lipases are highly sensitive to changes in temperature and pH and are difficult to reuse in continuous cycles; however, certain immobilization techniques can improve their catalytic activity and stability. Furthermore, the application of immobilized lipases in the synthesis of phytosterol esters can be combined with ultrasonic treatment to enhance the efficiency of enzymatic catalysis. This paper reviews the research progress on the catalytic esterification of phytosterol by immobilized lipases, highlighting the current challenges and future research directions, thereby fostering further advancements in the field of preparing phytosterol esters through immobilized lipase catalysis. Full article

In this paper, the ultrasonic vibration treatment (UVT) technique was used to prepare a SnSbCu11-6 alloy semi-solid slurry, and the effects of ultrasonic power on its microstructure size, distribution and properties were studied. The results show that the UVT technique significantly refines the Cu6Sn5 phase and SnSb phase and improves their distribution uniformity. Interestingly, the second SnSb phase is also well refined to nearly 100 °C below the melting point; furthermore, the morphology is transformed from coarse petal-like to fine regular cubic, and the average grain size is refined to 48.8 ± 8.8 μm. The alloy’s comprehensive properties are best when the ultrasonic power is 1200 W. The yield strength, tensile strength, elongation and microhardness reach 60.6 MPa, 70.3 MPa, 4.9% and 27.4 HV, respectively, which represent increases of 4.7%, 6.0%, 113% and 23.4%, respectively, compared with conventional liquid casting. This may be attributed to the grain size refinement and distribution uniformity enhancement of the Cu6Sn5 phase and the SnSb phase. This work provides a feasible and effective method for the preparation of high-performance tin-based babbitt alloys by UVT technology. Full article

A novel magnesium (Mg)-based metal matrix nanocomposite (MMNC) was fabricated using ultrasonic melt treatment to promote the de-agglomeration of the bioactive glass–ceramic nanoparticles and the homogenization of the melt. The cast samples were then heat treated, machined, and hot rolled to reduce grain size and remove structural defects. Standard mechanical and electrochemical tests were conducted to determine the effect of fabrication and processing on the mechanical and corrosion properties of MMNCs. Compression tests, potentiodynamic polarization tests, electrochemical impedance spectroscopy, and static immersion testing were conducted to determine the characteristics of the MMNCs. The results showed that the combination of ultrasonic melt processing and thermomechanical processing caused the corrosion rate to increase from 8.7 mmpy after 10 days of immersion to 22.25 mmpy when compared with the ultrasonicated MMNCs but remained stable throughout the immersion time, showing no statistically significant change during the incubation periods. These samples also experienced increased yield stress (135.5 MPa) and decreased elongation at break (21.92%) due to the significant amount of grain refinement compared to the ultrasonicated MMNC (${\mathsf{\sigma }}_{\mathrm{Y}}$ = 59.6 MPa, elongation = 40.44%). The MMNCs that underwent ultrasonic melt treatment also exhibited significant differences in the corrosion rate calculated from immersion tests. Full article

The widespread presence of ammonia nitrogen (NH₄⁺–N) pollutants poses a serious threat to water environment health. In this study, a novel zeolite (WTR–CFA zeolite) with excellent adsorption performance is synthesized using CFA as the raw material and water treatment residue (WTR) as the aluminum source through an ultrasonic–assisted alkali melt hydrothermal method. Compared with traditional CFA–zeolite, WTR–CFA zeolite only generates 4A zeolite with a single crystal phase, and the peak shape is sharp, which results in better crystallization. WTR–CFA zeolite perfectly solves the technical problems of the low utilization rate and poor controllability of the crystal form in traditional artificially synthesized zeolites. The maximum NH₄⁺–N adsorption capacity of WTR–CFA zeolite is 29.80 mg/g, which is higher than that of most adsorbents reported in previous studies. After five cycles of adsorption regeneration, the regeneration efficiency of WTR–CFA zeolite only decreased from 98.84% to 97.12%, which demonstrates excellent environmental value. The adsorption isotherms and kinetics of NH₄⁺–N conform to the Langmuir model and quasi–second order kinetic model, respectively, which indicates that ion–exchange–dominant chemical adsorption plays a major role in the adsorption mechanism. In summary, this study combines the use of CFA and WTR resources with the treatment of aquatic pollution to reduce material synthesis costs, control the crystal structure of WTR–CFA zeolite, and increase adsorption capacity. This approach achieves the goals of “waste treatment and turning waste into treasure”. Full article

Hot deformation constitutive analysis and processing maps of ultrasonic melt treated (UST) A5052 alloy were carried out based on a hot torsion test in this study. The addition of the Al–Ti master alloy as a grain refiner with no UST produced a finer grain size than the UST and pure Ti sonotrode. The Al3Ti phase particles in the case of the Al–10Ti master alloy acted as a nucleus for grain refinement, while the Ti atoms dissolved in the melt from the sonotrode were considered to have less of a grain refinement effect, even under UST conditions, than the Al3Ti phase particles in the Al–Ti master alloy. The constitutive equations for each experimental condition by torsion test were derived. In the processing maps examined in this study, the flow instability region was not present under UST in the as-cast condition, but it existed under the no UST condition. The effects of UST examined in this study are considered as (i) the uniform distribution of Ti solutes from the sonotrode and (ii) the reduction of pores by the degassing effect. After the homogenization heat treatment, most instability regions disappeared because the microstructures became uniform following the decomposition of intermetallic compounds and distribution of solute elements. Full article

Taxanes are the best-known compounds in Taxus cuspidata owing to their strong anticancer effects. However, the traditional taxanes extraction method is the solid–liquid extraction method, which is limited by a large energy consumption and low yield. Therefore, it is urgent to find an efficient method for taxanes extraction. The ultrasonic microwave synergistic extraction (UME) method integrates the cavitation effect of ultrasound and the intensifying heat transfer (ionic conduction and dipole rotation of molecules) effect of microwave to accelerate the release of intracellular compounds and is used in active ingredient extractions. This study aimed to evaluate the performance of UME in extracting taxanes from T. cuspidata needles (dichloromethane-ethanol as extractant). A single-factor experiment, Plackett–Burman design, and the response surface method showed that the optimal UME parameters for taxanes extraction were an ultrasonic power of 300 W, a microwave power of 215 W, and 130 sieve meshes. Under these conditions, the taxanes yield was 570.32 μg/g, which increased by 13.41% and 41.63% compared with the ultrasound (US) and microwave (MW) treatments, respectively. The reasons for the differences in the taxanes yield were revealed by comparing the physicochemical properties of T. cuspidata residues after the UME, US, and MW treatments. The cell structures were significantly damaged after the UME treatment, and numerous tiny holes were observed on the surface. The absorption peaks of cellulose, hemicellulose, and lignin increased significantly in intensity, and the lowest peak temperature (307.40 °C), with a melting enthalpy of −5.19 J/g, was found after the UME treatment compared with the US and MW treatments. These results demonstrate that UME is an effective method (570.32 μg/g) to extract taxanes from T. cuspidata needles by destroying cellular structures. Full article

This study developed a technical task associated with the formation of welded joints based on biodegradable polymers and their subsequent physicochemical characterization. The primary objective was to establish the effect of the welding process and modification of natural poly(3-hydroxybutyrate) (PHB) with N,N-dibutylundecenoylamide (DBUA) as a plasticizing agent on the structure and properties of PHB-based biopolymer materials as well as the process and structure of welded joints formation using ultrasonic welding technique. The weldability of biodegradable layers based on PHB and PHB/DBUA mixture was ultrasonically welded and optimized using a standard Branson press-type installation. The effect of the DBUA plasticizer and welding process on the structure of PHB-based biodegradable material was investigated using scanning electron microscopy, X-ray diffraction, FT-IR spectroscopy, differential scanning calorimetry, and thermomechanical analysis. The results confirmed that the DBUA acted as an effective plasticizer of PHB, contributing to lower crystallinity of the PHB/DBUA mixture (63%) in relation to the crystallinity degree of pure PHB film (69%). Ultrasonic welding resulted in an additional increase (approximately 8.5%) in the degree of crystallinity in the PHB/DBUA in relation to the initial PHB/DBUA mixture. The significant shift toward lower temperatures of the crystallization and melting peaks of PHB modified with DBUA were observed using DSC concerning pure PHB. The melt crystallization process of PHB was affected by welding treatment, and a shift toward higher temperature was observed compared with the unwelded PHB/DBUA sample. The butt-welded joints of biodegradable PHB/DBUA materials made using the ultrasonic method tested for tensile strength have damaged the area immediately outside the joining surface. Full article

Single-pressure and ultrasonic action have their own unique advantages in the treatment of metal melts. When the two are combined into a composite field, the advantages of a single physical field can be fully utilized. So, the cavitation and acoustic streaming effects characteristics of an Al-5.0Cu alloy treated under different coupling process parameters, related to applied extrusion pressure and ultrasonic vibration, were analyzed by combining numerical simulation and experimental verification. The simulation results were experimentally verified by quantitative analysis of the microstructure, the melt, and its macro characteristics. The results show that the closing time t decreases with an increase in the extrusion pressure. In addition, when the ultrasonic power and extrusion force are increased simultaneously (100 MPa and 1 kW), the average grain size and the proportion of columnar grains reach the ideal effect. The influence of pressure parameters is greater, which will also lead to an increase in the proportion of columnar crystals. By optimizing the parameters, the grain size can be further reduced, the proportion of columnar crystal structure can be reduced, and fine and uniform equiaxed crystal structures can be easily obtained. Full article

Titanium alloys additively manufactured by electron beam melting (EBM) inevitably obtained some pore defects, which significantly reduced the very high cycle fatigue performance. An ultrasonic fatigue test was carried out on an EBM TC21 titanium alloy with hot isostatic pressing (HIP) and non-HIP treatment, and the effect of pore defects on the very high cycle fatigue (VHCF) behavior were investigated for the EBM TC21 titanium alloy. The results showed that the S-N curve of non-HIP specimens clearly had a tendency to decrease in very high cycle regimes, and HIP treatment significantly improved fatigue properties. Fatigue limits increased from 250 MPa for non-HIP specimens to 430 MPa for HIP ones. Very high cycle fatigue crack mainly initiated from the internal pore for EBM specimens, and a fine granular area (FGA) was observed at the crack initiation site in a very high cycle regime for both non-HIP and HIP specimens. ΔK_FGA had a constant trend in the range from 2.7 $\mathrm{MPa}\sqrt{\mathrm{m}}$ to 3.5 $\mathrm{MPa}\sqrt{\mathrm{m}}$, corresponding to the threshold stress intensity factor range for stable crack propagation. The effect of pore defects on the very high cycle fatigue limit was investigated based on the Murakami model. Furthermore, a fatigue indicator parameter (FIP) model based on pore defects was established to predict fatigue life for non-HIP and HIP specimens, which agreed with the experimental data. Full article

The effect of the infiltration time of a carbon fiber yarn in the range of 6 to 13.6 s on the infiltrated volume under the cavitation of an aluminum melt has been studied. When the infiltration time was more than 10 s, the carbon fiber was completely infiltrated with the matrix melt, and a decrease in the infiltration time led to a monotonous decrease in the fraction of the infiltrated volume. Based on the experimental data, the infiltration rate and the pressure necessary to infiltrate a carbon fiber yarn with an aluminum melt were estimated. The infiltration rate was 20.9 cm³/s and was independent of the infiltration depth. The calculated pressure necessary for the complete infiltration of a carbon fiber yarn at this rate was about 270 Pa. A comparison of the pressure values calculated according to Darcy’s and Forchheimer’s laws showed that the difference between them did not exceed 0.01%. This indicates that a simpler Darcy’s law could be used to estimate pressure. Full article

Metal matrix nanocomposites (MMNCs) are becoming the materials of choice in a variety of engineering and medical applications owing to their exhibiting a superior combination of targeted properties. Amongst different MMNCs, aluminum-based composites are of special importance. In many applications, a relatively inferior wear property limits the use of this valued metal in practice. However, reinforcing aluminum and its alloys by ceramics, carbon allotropes, etc., may circumvent these limitations to a great extent. In the present study, aluminum alloy A356/SiO₂ nanocomposite is fabricated by a vibration-assisted casting process, wherein varied amount of nanosilica, namely, 0.125, 0.25, and 0.375 wt.%, have been added to the melt. The use of power ultrasonic treatment had a great influence on the microstructure, hardness, and wear properties. Microstructural and XRD analyses were performed on the fabricated monolithic and composite samples. To evaluate wear behavior, a hardness test and pin-on-disk experiment were conducted on the samples under 60, 80, and 100 N forces at a constant speed of 1 m/s and the sliding distance was varied from 1000 to 2000 m. The abraded surfaces, wear debris, and EDS analysis were used to identify wear mechanisms. The samples having 0.125 wt.% exhibited the highest increase in hardness and the highest reduction in both friction coefficient and wear rate by 52%, 50%, and 68%, respectively. The main governing wear mechanism was abrasion, with limited evidence of delamination. Full article

We studied the shear bond strength (SBS) of two PEEK composites (BioHPP, BioHPP plus) with three veneering composites: Visio.lign, SR Nexco and VITA VM LC, depending on the surface treatment: untreated, sandblasted with 110 μm Al₂O₃, sandblasted and cleaned ultrasonically in 80% ethanol, with or without adhesive Visio.link, with applied Visio.link and MKZ primer. For the BioHPP plus, differential scanning calorimetry (DSC) revealed a slightly lower glass transition temperature (T_g 150.4 ± 0.4 °C) and higher melting temperature (T_m 339.4 ± 0.6 °C) than those of BioHPP (T_g 151.3 ± 1.3 °C, T_m 338.7 ± 0.2 °C). The dynamical mechanical analysis (DMA) revealed a slightly higher storage modulus of BioHPP (E’ 4.258 ± 0.093 GPa) than of BioHPP plus (E′ 4.193 ± 0.09 GPa). The roughness was the highest for the untreated BioHPP plus, and the lowest for the polished BioHPP. The highest hydrophobicity was achieved on the sandblasted BioHPP plus, whereas the highest hydrophilicity was found on the untreated BioHPP. The highest SBSs were determined for BioHPP and Visio.lign, adhesive Visio.link (26.31 ± 4.17 MPa) or MKZ primer (25.59 ± 3.17 MPa), with VITA VM LC, MKZ primer and Visio.link (25.51 ± 1.94 MPa), and ultrasonically cleaned, with Visio.link (26.28 ± 2.94 MPa). For BioHPP plus, the highest SBS was determined for a sandblasted surface, cleaned ultrasonically, with the SR Nexco and Visio.link (23.39 ± 2.80 MPa). Full article

In this work, Al(OH)₃ nanosheets are synthesized in situ on the surface of an Al-20Si alloy via the water bath method, and Al–20Si@Al₂O₃ composites are then obtained after calcination. The growth mechanism of the Al(OH)₃ nanosheets is revealed, and a pathway is demonstrated to obtain Al–20Si@Al₂O₃ nanosheets with the desired structure and thickness. Furthermore, the influence of different Al–20Si@Al₂O₃ contents on the primary silicon phase in the Al–20Si alloy is investigated, and the mechanism of such an influence is theoretically analyzed. The mechanical properties of the modified Al–20Si alloy are tested, and the effects of the morphology and particle size of the silicon phase on the alloy properties are studied. The results show that Al–20Si@Al₂O₃ synthesized in situ by water bath has good dispersion in the melt. There is a lot of γ-Al₂O₃ dispersed in the matrix of the alloy, and the primary silicon of the Al-20Si alloy is obviously refined. By increasing the content of the modifier, the average size of primary silicon decreases first and then increases. When 15 wt% of the modifier is added, the refinement effect of primary silicon reaches its peak, and the size of primary silicon is reduced from unmodified 86.4 μm to 28.5 μm. The hardness and tensile strength of 75.2 HB and 120.3 MPa are increased to 107.2 HB and 185.9 Mpa by 42% and 55%, respectively. Compared with adding γ-Al₂O₃ directly, this experiment provides a simple method to synthesize the modifier, and γ-Al₂O₃ can be dispersed evenly in the aluminium-silicon alloy melt more easily by in-situ generation, without ultrasonic treatment or other ways. During mass production, the cost can be better controlled and good results can be achieved at the same time. Full article

This study aims to explore a preparation method based on a combination of melting and ultrasound to produce a Ga₂O₃/ZnO (GZ) spherical composite with a snake raspberry structure for the degradation of methyl orange at room temperature in dark. The catalyst exists in the form of a (GZ) composite and an anhydrous ethanol mixture after the ultrasonic treatment of premelted GaZn liquid metal alloy in anhydrous ethanol. The degradation activity of the catalyst was evaluated according to the amount of catalyst, alloy extraction temperature, acid–base environment, and inorganic salt ions. A transmission electron microscope (TEM) was used to confirm that the material was Ga₂O₃ coated with ZnO, with a structure similar to that of snakeberry. The electron paramagnetic resonance (EPR) and a series of free radical inhibition experiments demonstrated that ·O²⁻ is produced during the ultrasonic preparation of the catalyst and plays an important role in the degradation process after adding MO. The removal rate of MO reached 99.75% at 3 min. Three possible degradation pathways were proposed based on the intermediates produced during the degradation process, which were identified by liquid chromatography–mass spectrometry (LC–MS). The results of this study may provide a new choice for the degradation of organic pollutants. Full article