Search Results (28)

Nano- and pico-bubble water (NPB), containing hydrogen or ozone, is widely used as a cleaning agent due to its bactericidal and antiviral properties. However, some products—such as certain hydrogen waters—contain only large bubbles or have an extremely low bubble count, making them sometimes indistinguishable from ordinary drinking water. To accurately evaluate NPB activity, we developed a method for producing ultra-nano–pico-bubble water (NanoGAS water [NGW]), an ultra-fine bubble water that is stable and non-volatile over extended periods. By combining a mixed gas–liquid fluid rotary mixer and a shear filter, we produced ultra-fine bubbles that could be sealed in water. This method produced bubbles that remained stable in water even after 10 years since production. NGW has been clinically evaluated as a solvent for fecal microbiota transplantation (FMT) and has been demonstrated to be effective at improving bacterial engraftment in the intestinal tract in patients with autism spectrum disorder (ASD). Furthermore, encapsulating specific gases (hydrogen and ozone) can achieve more diverse effects. In this study, we evaluated the aroma-encapsulating effects, as well as the strength and persistence of the antimicrobial activity, of novel NGW formulations (Air-NGW, H₂-NGW, S-O₃-NGW, and L-O₃-NGW). Both H₂-NGW and O₃-NGW generated in this study demonstrated slight inclusion activity with volatile aromatic compounds (citral). Furthermore, both H₂-NGW (at ≥10% dilution) and O₃-NGW (even at a 1% dilution) exhibited sustained antibacterial efficacy against general viable bacteria for 24 weeks. Moreover, additive effects were observed when combined with antibacterial and antiviral compounds (polyoxometalates) developed by the authors. While further consideration, including cost-effectiveness, is needed to translate these findings into practical applications, they provide a fundamental framework for future research. Full article

High-purity copper features excellent electrical conductivity but generally low mechanical properties. Adding a three-dimensional graphene network as reinforcement to make a copper–graphene metal matrix composite is promising for a wide range of applications with better mechanical performance and functional capabilities. However, direct application in a metal matrix is difficult due to unfavorable wetting, which causes poor dispersion and weak interfacial bonding in the graphene–metal system. Here, the powder metallurgy method was used to construct a three-dimensional continuous graphene network in the copper matrix combined with high-pressure torsion. Optimized deformation/thermomechanical treatment enhanced the microstructural development processed by the severe plastic deformation method of high-pressure torsion. The primary advantage of this hybrid process is that it enables us to achieve grains with a size in the ultra-fine or even nanoscale. A homogeneous equiaxed nanostructure without segregation was observed during microstructural characterization, with a grain size of ~300 nm. This study investigated structural development during progressive deformation, and the samples were evaluated from the viewpoint of grain size and grain boundaries. The process significantly increased the microhardness of the copper–graphene composite. The tensile strength reached ~500 MPa at room temperature. The interpenetrating structural feature of graphene promoted interfacial shear stress to a high level, whereas plastic deformation increased the dislocation density and grain boundaries, thus resulting in significantly enhanced load transfer strengthening and crack-bridging toughness simultaneously. Full article

The quality of the feedstock powder plays a key role in determining the properties of coatings produced by cold spray (CS). However, most commercially available powders are not specifically designed for CS, which makes it difficult to tailor powder characteristics for optimal performance. In this study, we examined the cold sprayability of five copper (Cu) powders manufactured using electrolysis, gas atomization, and mechanical grinding. The powders were characterized in terms of their microstructure, particle shape, and size distribution to evaluate how the production method influences powder properties. Powder flowability was measured using a shear cell test, while mechanical properties and deformability relevant to CS were assessed through nano-indentation. The results showed that gas-atomized powders with equiaxed grain structures offered the best combination of flowability and deformability, making them the most suitable for CS. Their spherical particle shape resulted in a lower surface area compared to the irregular electrolytic powder, which reduced inter-particle surface forces and allowed for smoother powder flow. Nano-indentation measurements indicated that the mechanically ground powder with ultra-fine grains and the gas-atomized powder containing fine dendrites had the highest nano-hardness values (HIT = 2.1 ± 0.15 GPa and 1.6 ± 0.1 GPa, respectively). In contrast, the porous electrolytic Cu powder showed the lowest hardness (HIT = 0.7 ± 0.2 GPa). These trends were confirmed by microstructural analysis of the deposited coatings. Coatings produced from the irregular electrolytic powder exhibited limited particle deformation, weak inter-particle bonding, and the highest porosity. Conversely, spherical gas-atomized powders produced much denser coatings. In particular, the powder with the most uniform spherical shape and no microsatellite particles resulted in the lowest coating porosity due to its superior deformation behavior upon impact. Full article

Zirconium and its alloys are widely used in nuclear power engineering due to their favorable physical and mechanical properties and their low thermal-neutron absorption cross-section. Their high corrosion resistance in aqueous and steam environments at elevated temperatures is essential for the reliable operation of fuel assemblies and is associated with the formation of a stable, compact ZrO₂ oxide layer. However, under reactor conditions, the presence of hydrogen, iodine and other fission products can reduce corrosion resistance, making detailed corrosion assessment necessary. Manufacturing technology, alongside alloy composition, also plays a decisive role in determining corrosion behavior. This study presents corrosion test results for a Zr-1%Nb alloy processed under thermomechanical conditions corresponding to rolling in a special type of three-roll skew rolling–Radial-Shear Rolling (RSR). The applied rolling technology ensured the formation of a pronounced ultrafine-grained (UFG) structure in the near-surface layers, with an average grain size below 0.6 µm. EBSD and TEM observations revealed a largely equiaxed microstructure with refined grains and increased grain boundary density. The corrosion testing was performed in high-temperature steam vessels at 400 °C and 10.3 MPa for 72, 336, 720 and 1440 h. The results demonstrate that RSR processing is an efficient alternative to conventional multi-pass normal bar rolling with vacuum heat treatments, allowing a significant reduction in processing steps and eliminating the need for expensive tooling and intermediate thermal or chemical treatments. Bars manufactured using this method meet the ASTM B351 requirements. The specific weight gain did not exceed 22 mg/dm² after 72 h and 34.5 mg/dm² after 336 h. After 1440 h, the samples exhibited a continuous, uniform dark-grey oxide layer with an average thickness below 5.3 µm. Full article

Cemented tailings backfill (CTB) plays an important role in mine filling operations. In order to study the long-term stability of CTB under the dynamic disturbance of deep wells, ultrafine cemented tailings backfill was taken as the research object, and the true triaxial hydraulic fracturing antireflection-wetting dynamic experimental system of coal and rock was used to carry out a static true triaxial compression test, a true triaxial compression test under unidirectional disturbance, and a true triaxial compression test under bidirectional disturbance. At the same time, the acoustic emission monitoring and positioning tests of the CTB were carried out during the compression test. The evolution law of the mechanical parameters and deformation and failure characteristics of CTB under different confining pressures is analyzed, and the damage constitutive model of the filling body is established using stochastic statistical theory. The results show that the compressive strength of CTB increases with an increase in intermediate principal stress. According to the change process of the acoustic emission ringing count over time, the triaxial compression test can be divided into four stages: the initial active stage, initial calm stage, pre-peak active stage, and post-peak calm stage. When the intermediate principal stress is small, the specimen is dominated by shear failure. With an increase in the intermediate principal stress, the specimen changes from brittle failure to plastic failure. The deformation and failure strength of CTB are closely related to its loading and unloading methods. Under a certain stress intensity, compared with unidirectional unloading, bidirectional unloading produces a greater deformation of the rock mass, and the failure strength of the rock mass is higher. This study only considers the confining pressure within the compressive limit of the specimen. Future research can be directed at a wider range of stresses to improve the applicability and reliability of the research results. Full article

The high-efficiency dewatering of ultra-fine tailings is one of the most prominent challenges in tailings thickening. The two-step shear flocculation process represents a promising practical method to achieve the dewatering of ultra-fine tailings. In this paper, a small self-made experimental device was used to simulate the two-step shear flocculation process of ultra-fine tailings, strengthening the effect of shear failure and shear coagulation, and we explored the mass fraction of ultra-fine tailings, floc structure size, floc strength, and regeneration performance of tailings slurry according to the variation in shear action in different stages. In addition, the synergistic mechanism of shear failure and shear coagulation in the two-step high-efficiency dewatering process of ultra-fine tailings was proposed. The results show that the dewatering of ultra-fine tailings was significantly improved by two-step flocculation, and the mass fraction of tailings can reach more than 71%. In the primary floc failure stage, the value of G₁T₁ should be higher than 100,000, and in the secondary floc regeneration stage, the value of G₂T₂ should be in the range of 7000~11,000. This paper provides a reference for the regulation of the shear mode and action range in the two-step flocculation process of ultra-fine tailings. Full article

Commercially pure Cu features excellent electric conductivity but low mechanical properties. In order to improve the mechanical properties of Cu, strengthening elements can be added to prepare alloys or composites featuring enhanced performances. This study focuses on the detailed characterization of the microstructure of a Cu composite strengthened with Al₂O₃ particles during high shear strain processing. The Cu-Al₂O₃ mixture was prepared by powder metallurgy and directly consolidated by the intensive plastic deformation method of hot rotary swaging. Samples cut from the consolidated piece were further processed by the severe plastic deformation method of high pressure torsion (HPT). The primary aim was to investigate the effects of varying degrees of the imposed shear strain, i.e., the number of HPT revolutions, microstructure development (grain size and morphology, texture, grain misorientations, etc.) of the consolidated composite; the microstructure observations were supplemented with measurements of Vickers microhardness. The results showed that the added oxide particles effectively hindered the movement of dislocations and aggravated grain fragmentation, which also led to the relatively high presence of grain misorientations pointing to the occurrence of residual stress within the microstructure. The high shear strain imposed into (the peripheral region of) the sample subjected to four HPT revolutions imparted equiaxed ultra-fine grains and an average Vickers microhardness of more than 130 HV0.1. Full article

Carbon/carbon (C/C) composite materials are widely used in aerospace, the military and nuclear energy. The outstanding mechanical qualities of C/C composites mean that they are difficult to crush and recycle using traditional technology. The current recycling methods primarily involve stacking and landfill disposal. Therefore, achieving efficient and environmentally friendly recycling of carbon/carbon (C/C) composites is an urgent and challenging issue. In this work, we reported a simple high-value recycling approach for carbon–carbon frictional composite material (CFCM). The solid-state shear milling (S³M) technology is employed to achieve ultrafine milling of carbon matrices in carbon/carbon (C/C) composite materials while preserving carbon fibers. By this means, carbon fibers and the carbon matrix were mainly split, and the prepared composite powder had combined functionalities of conductivity, thermal conductivity, reinforcement, and wear resistance. The experimental results showed that the tensile strength of the material increased from 64.35 MPa to 72.79 MPa after being compounded with PA6, and the thermal conductivity increased from 0.211 W/mK to 0.611 W/mK. The friction coefficient was reduced from 0.51 to 0.36, a reduction of 25.4%, and the heat deflection temperature was increased from 47.2 °C to 108.2 °C. The S³M technique proposed in this work is an efficient, high-value, and scalable recycling strategy for CFCM, which can be used to produce value-added products and has great application prospects. Full article

In developing materials for the nuclear industry, it is crucial to enhance both alloy composition and processing methods. This study focuses on investigations of applying radial-shear rolling (RSR) to a Zr-1%Nb alloy ingot, aiming to refine its microstructure and improve its properties for nuclear applications. This method, with complex vortex metal flow inside of a casted workpiece, has not been previously tested for processing zirconium ingots, so experimental verification of its applicability is of scientific interest. The 30 mm diameter ingot, produced by vacuum induction melting, was initially rolled to 20 mm at 800 °C to eliminate defects and refine the cast structure. A second rolling stage reduced the diameter to 13 mm at 530 °C, resulting in an ultrafine-grained structure. The RSR method effectively combines structural refinement and defect healing within fewer cycles, making it suitable for producing components for nuclear reactors. This approach demonstrates a potential reduction in traditional processing steps, providing a more efficient route for preparing high-quality materials for nuclear applications. Full article

Among the main benefits of powder-based materials is the possibility of combining different constituents to achieve enhanced properties of the fabricated bulk material. The presented study characterizes the micro- and sub-structures and related mechanical properties of ferritic steel strengthened with a fine dispersion of nano-sized Y₂O₃ oxide particles. Unlike the typical method of preparation via rolling, the material presented herein was fabricated by direct consolidation from a mixture of powders using the versatile method of hot rotary swaging. The mechanical properties were evaluated at room temperature and also at 1300 °C to document the suitability of the prepared steel for high-temperature applications. The results showed that the imposed shear strain, i.e., swaging ratio, is a crucial parameter influencing the microstructure and, thus, material behavior. The workpiece subjected to the swaging ratio of 1.4 already exhibited a sufficiently consolidated structure with ultra-fine grains and featured high room-temperature microhardness values (up to 690 HV0.5), as well as a relatively high maximum flow stress (~88 MPa) when deformed at the temperature of 1300 °C with the strain rate of 0.5 s⁻¹. However, the dispersion of oxides within this sample exhibited local inhomogeneities. Increasing the swaging ratio to 2.5 substantially contributed to the homogenization of the distribution of the Y₂O₃ oxide particles, which resulted in increased homogeneity of mechanical properties (lower deviations from the average values), but their lower absolute values due to the occurrence of nucleating nano-sized recrystallized grains. Full article

Semi-aromatic poly (hexamethylene terephthalamide) (PA6T) oligomer (prePA6T) ultrafine powder, with a diameter of <5 μm, was prepared as an emulsion sizing agent to improve the impregnation performance of CF/PA6T composites. The prePA6T hyperfine powder was acquired via the dissolution and precipitation “phase conversion” method, and the prePA6T emulsion sizing agent was acquired to continuously coat the CF bundle. The sized CF unidirectional tape was knitted into a fabric using the plain weave method, while the CF/PA6T laminated composites were obtained by laminating the plain weave fabrics with PA6T films. The interfacial shear strength (IFSS), tensile strength (TS), and interlaminar shear strength (ILSS) of prePA6T-modified CF/PA6T composites improved by 54.9%, 125.3%, and 120.9%, respectively. Compared with the commercial polyamide sizing agent product PA845H, the prePA6T sizing agent showed better interfacial properties at elevated temperatures, especially no TS loss at 75 °C. The SEM observations also indicated that the prePA6T emulsion has an excellent impregnation effect on CF, and the fracture mechanism shifted from adhesive failure mode to cohesive failure mode. In summary, a facile, heat-resistant, undamaged-to-fiber environmental coating process is proposed to continuously manufacture high-performance thermoplastic composites, which is quite promising in mass production. Full article

The mechanical characteristics of polycrystalline metallic materials are influenced significantly by various microstructural parameters, one of which is the grain size. Specifically, the strength and the toughness of polycrystalline metals exhibit enhancement as the grain size is reduced. Applying severe plastic deformations (SPDs) has a noticeable result in obtaining metallic materials with ultrafine-grained (UFG) microstructure. SPD, executed through conventional shaping methods like extrusion, plays a pivotal role in the evolution of the texture, which is closely related to the plastic behavior and ductility. A number of SPD processes have been developed to generate ultrafine-grained materials, each having a different shear deformation mechanism. Among these methods, linear twist extrusion (LTE) presents a non-uniform and non-monotonic form of severe plastic deformation, leading to significant shifts in the microstructure. Prior research demonstrates the capability of the LTE process to yield consistent, weak textures in pre-textured copper. However, limitations in production efficiency and the uneven distribution of grain refinement have curbed the widespread use of LTE in industrial settings. This has facilitated the development of an improved novel method, that surpasses the traditional approach, known as the nonlinear twist extrusion procedure (NLTE). The NLTE method innovatively adjusts the channel design of the mold within the twist section to mitigate strain reversal and the rotational movement of the workpiece, both of which have been identified as shortcomings of twist extrusion. Accurate anticipation of texture changes in SPD processes is essential for mold design and process parameter optimization. The performance of the proposed extrusion technique should still be studied. In this context, here, a single crystal (SC) of copper in billet form, passing through both LTE and NLTE, is analyzed, employing a rate-dependent crystal plasticity finite element (CPFE) framework. CPFE simulations were performed for both LTE and NLTE of SC copper specimens having <100> or <111> directions parallel to the extrusion direction initially. The texture evolution as well as the cross-sectional distribution of the stress and strain is studied in detail, and the performance of both processes is compared. Full article

Rotary swaging is an industrially applicable intensive plastic deformation method. Due to its versatility, it is popular, especially in the automotive industry. Similar to the well-known methods of severe plastic deformation (SPD), rotary swaging imparts high shear strain into the swaged materials and thus introduces grain refinement down to a very fine, even ultra-fine, level. However, contrary to SPD methods, one of the primary characteristics of which is that they retain the shapes and dimensions of the processed sample, rotary swaging enables the imparting of required shapes and dimensions of workpieces (besides introducing structure refinement and the consequent enhancement of properties and performance). Therefore, under optimized conditions, swaging can be used to process workpieces of virtually any metallic material with theoretically any required dimensions. The main aim of this review is to present the principle of the rotary swaging method and its undeniable advantages. The focus is primarily on assessing its pros and cons by evaluating the imparted microstructures. Full article

In this paper, a novel method for the preparation of ultra-fine-grained bulk materials called asymmetric gradient extrusion (AGE) is proposed. In AGE, the cross-section of the extrusion channel is a rectangle, and two inclined planes are staggered along the extrusion direction. To realize repetitive extrusion, the thickness of the workpiece is limited to be equal to the width of the channel outlet. In order to study the mechanism of ultra-fine grain formation in AGE, the deformation characteristics of AGE were investigated. First, the slip line field method was used to theoretically analyze the deformation characteristics and grain splitting in AGE. Then, the plastic deformation behavior of bulk samples in AGE and traditional extrusion was investigated and compared with the finite element method. In addition, the deformation characteristic and microstructure variation of pure copper bulk samples in AGE were experimentally investigated. The results showed that the deformation characteristics of workpieces were highly related to the two inclined planes within the die channel. Two independent deformation zones can be formed with increasing distance between the two inclined planes. The shear effects in each deformation zone lead to grain splitting during extrusion. Compared with traditional extrusion, the advantage of AGE is its amazing ability to form high and uniform strain during extrusion, which leads to the formation of small and uniform grains in the workpiece. After six passes of AGE, an average grain size of 0.6 μm can be achieved. The enhancement and accumulation of dislocations within grains was the dominating mechanism of grain fragmentation. AGE shows impressive potential in the preparation of ultra-fine-grained bulk materials. Full article

High-pressure torsion (HPT) is an effective severe plastic deformation method to produce ultrafine-grained (UFG) and nanocrystalline (NC) materials. In the past, most studies have focused on the evolutions in the microstructure, texture and mechanical properties of HPT-deformed materials at peripheral regions. The corresponding evolutions at a special area were observed in this study to reveal the potential plastic deformation mechanism for face-centred cubic (FCC) material with high stacking fault energy. A decreasing trend was found in grain size, and the final grain size was less than 1 μm. However, close observation revealed that the general trend could be divided into different sub-stages, in which grain elongation and grain fragmentation were dominant, respectively. Additionally, microhardness demonstrated a non-linear increase with the development of plastic deformation. Finally, the microhardness reached a high level of ~64 HV. At the early stages of HPT, the C component was transformed into a cube component, suggesting the material flows around the shear plane normal (SPN) axis at these stages. However, finally they will be replaced by ideal simple shear orientations. Full article