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The fracture mechanics of frozen rock are important to engineering in cold regions, yet the basic properties and influences remain unclear. The fracture toughness of semi-circular bend (SCB) samples with different initial saturation degrees (ISDs) was tested at − 20 ℃. Acoustic emission (AE) and digital image correlation (DIC) systems were used to capture AE signals and surface deformation under load testing. In addition, the phase composition in rock pores was measured by low-field nuclear magnetic resonance (LF-NMR). It was found that: (1) Fracturing of frozen sandstone generally consists of three stages: pore or microcrack closing, elastic deformation and microcrack propagation which is evidenced by the variation of AE counts and the maximum horizontal strain within the fracture process zone (FPZ) under loading. (2) The ISD has a great influence on fracture toughness and the microcrack propagation process. With increases in ISD, both the fracture toughness and fracture energy of frozen sandstone varies in a mode of slow increase (ISD < 40%), rapid increase (ISD 40–90%) and slight decrease (ISD 90–100%). (3) The phase composition in pores of frozen rock with low ISD (< 40%) is significantly different from that with high ISD (40–100%). At ISDs of < 40%, the ice in rock pores mainly originates from adsorbed water; however, at ISDs of 40–100%, the ice increasingly comes from free and capillary water. Based on the test results, the difference in fracture mechanical properties of frozen sandstone introduced by different ISDs can be attributed to the changes in pore phase composition, which determines the interaction between pore ice/unfrozen water and rock skeleton involving three processes: strengthening due to the filling effect of pore ice, strengthening due to the adhesion force and tensile strength of pore ice, and weakening due to frost damage.HighlightsFreezing strengthens water-bearing sandstone significantly, and the fracture toughness of frozen sandstone increases with its initial saturation degree.Initial saturation degree differs the fracturing process of frozen sandstone in terms of energy release and range of fracture process zone.Pore phase composition primarily determines the fracturing behaviour of frozen sandstone involving ice–pore interactions.The ice–pore cementation and tensile strength of ice are the main contributors to the increase of fracture toughness of frozen rock.

Four kinds of (Ta, Nb, Ti, V, W)C high-entropy ceramics with different combinations of bonding phases, namely Co, CoNi, CoNiCr, and CoNiCrFe, have been successfully prepared by conventional pressureless sintering method, and their microstructures and mechanical properties have been investigated. The results show that the complete high-entropy ceramics can be made using various metal elements as binder phases, which enhances the high-entropy formation ability of (Ta, Nb, Ti, V, W)C series high-entropy ceramics and improves their mechanical properties, and the transverse rupture strength of the CoNi combination reaches 797.42 MPa, the hardness of the CoNiCr combination reaches 1680 HV 30 , and the fracture toughness of the CoNiCrFe combination reaches 8.1 MPa. The present study shows that the multi-element combination mode is favorable to improve the grain formation ability of high-entropy cemented carbide ceramics and is important for reducing the Co element dependence in the field of pressureless sintering of ceramics. Graphical abstract

Four different columns with mixed-mode properties were used to investigate the retention behavior of four acidic compounds (ascorbic, nicotinic, p -toluenesulfonic, and p -hydroxybenzenesulfonic acids) and two neutral compounds (dexamethasone and paracetamol). The effect of mobile phase composition (acetonitrile content and buffer pH) on the retention of the analytes was studied to better understand the separation role of an ion-exchange group position within a stationary phase for acidic analytes. The impact of C18 hydrophobic moiety, identical for all the tested stationary phases, was studied on retention of two neutral compounds via selected parameters characterizing the investigated stationary phases. The results obtained were compared and discussed with data previously reached using an Acclaim ™ WAX-1 mixed-mode column. Graphical abstract

This study investigates the development of sustainable ceramic materials using industrial and agricultural waste from the Kyzylorda region of Kazakhstan. The research focuses on the combined use of local clay, ash from the Kyzylorda thermal power plant (TPP), and rice husk ash (RHA). Experimental investigations included the evaluation of chemical composition, linear and volumetric shrinkage, water absorption, bulk density, and compressive strength of ceramic samples fired at 950–1050 °C. Microstructural (SEM) and phase composition (XRD) analyses were performed to explain the observed behavior. The results showed that the optimal composition was 70% clay, 20% TPP ash, and 10% RHA, which demonstrated the highest compressive strength (15.45 MPa), reduced water absorption, and improved densification. The enhanced performance is attributed to partial vitrification and viscous-phase-assisted densification and the formation of crystalline phases such as mullite, cristobalite, and anorthite. The study confirms that the combined use of TPP ash and RHA enables effective recycling of local waste materials and improves the physical and mechanical properties of ceramic products.

For the first time the thermal stability of the phase composition of (ZnS)(Ag 2 S) x sulfide heteronanostructures are studied. Solid-phase heteronanostructures (ZnS)(Ag 2 S)x with x = 0.002 – 0.50 are synthesized by hydrochemical co-deposition of ZnS and Ag 2 S sulfides. The ZnS nanoparticle size, estimated from the broadening of diffraction reflections, in the produced initial heteronanostructures is 2 – 4 nm. Annealing of the synthesized (ZnS)(Ag 2 S) x heteronanostructures in air at temperature from 25 to 530 ◦C and above leads to a change in their phase composition due to the oxidation of cubic ZnS sulfide to hexagonal zinc oxide. Oxidation begins at a temperature of approximately 250 ◦C; the ZnO nanoparticle size varies in a range of 12 to 17 – 25 nm. Oxidation of solid-phase (ZnS)(Ag 2 S)x heteronanostructures in air showed that weight loss that occurs upon heating from ∼250 to ∼430 – 450 ◦C is associated with the beginning of oxidation of the ZnS sulfide and the formation of the ZnO oxide. The most significant weight loss is observed after heating from ∼450 to ∼580 ◦C due to an increase in the ZnO content, oxidation of sulfur and its removal in the form of SO 2 .

The development of surface morphology, the elemental and phase composition of surface layers, and the microhardness of a VT6 titanium alloy during treatment in a glow-discharge plasma of N+ ions is studied without and with heating alloy samples to 300, 500, and 700°C. The formation of thin surface layers (up to ~20 nm) during ion-plasma nitriding without heating and with heating up to 300°C is shown to be controlled by oxidation processes; at sample temperatures of 500 and 700°C, the formation is controlled by nitrogen diffusion. An increase in the treatment temperature leads to the formation of rounded block-like features on the surface, an increase in surface roughness parameter Ra, and higher microhardness values of the samples, which is attributed to the formation of the Ti2N and TiN titanium nitrides at the surface and in the surface layers.

In this study, the authors analyzed the structural-phase transformations in the surface layer of hypereutectic silumin AK20 (Al—20 wt. % Si), initiated by a sub-millisecond exposure to a pulsed electron beam. It has been established that irradiation of hypereutectic silumin with a pulsed electron beam (17 keV, (15–70) J/cm 2 , 150 μs, 3 pulses, 0.3 s -1 ) is accompanied by high-speed melting of a surface layer up to 120 μm thick, followed by high-speed crystallization with the formation of a cellular-columnar type structure with a transverse cell size of 0.5 to 2.9 μm. It has been shown that crystallization cells are formed by a solid solution based on aluminum and are separated by layers 120 to 700 nm thick, formed by amorphous and crystalline (nanocrystalline) silicon. It has been established that the sizes of cells and the layers separating them increase with increasing energy density of the electron beam. Using X‑ray diffraction analysis methods, changes in the parameters and micro-distortions of the crystal lattice of aluminum and silicon were revealed after exposure to a pulsed electron beam.

This study aims to provide insights into the experimental conditions used during the melting/casting process and subsequent thermal treatments of low-alloy steels, particularly regarding recycled scrap metals. As sustainable practices in metallurgy gain importance, optimizing scrap metal recycling is crucial for producing steel grades with desired chemical compositions, microstructures, and physical properties. Understanding these conditions is vital for enhancing the efficiency and quality of steel production from recycled materials. This study emphasizes the critical role of specific experimental conditions in the steelmaking process, especially with recycled scrap metals. It closely examines the atmosphere during melting/casting to identify key parameters that must be rigorously controlled in lab-scale steel production using a vacuum induction furnace. The findings indicate that both the chemical composition and recyclability of low-alloyed steels are significantly influenced by the surrounding atmosphere during melting and casting. Inert environments, such as vacuum or argon, are shown to be ideal for steelmaking with induction technology, particularly when recycling scrap metals. Additionally, this study highlights the importance of precise heat treatments, including homogenization and normalization, by controlling both thermal conditions and the atmosphere to produce high-quality steel from recycled scraps.

The effect of powerful ultrasonic oscillations (USO) on the microstructure and phase composition of the self-propagating high-temperature synthesis (SHS) products in the Ti–B binary system is studied. It is demonstrated that the application of USO during the synthesis leads to a change in the microstructure and phase composition of the synthesis products and allows one to exert an operational influence on the resulting final product.

In this study, the high-temperature oxidation behavior of a series of AlTiNiCuCox high-entropy alloys (HEAs) was explored. The AlTiNiCuCox (x = 0.5, 0.75, 1.0, 1.25, 1.5) series HEAs were prepared using a vacuum induction melting furnace, in which three kinds of AlTiNiCuCox (x = 0.5, 1.0, 1.5) alloys with different Co contents were oxidized at 800 °C for 100 h, and their oxidation kinetic curves were determined. The microstructure, morphology, structure, and phase composition of the oxide film surface and cross-sectional layers of AlTiNiCuCox series HEAs were analyzed using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD). The influence of Co content on the high-temperature oxidation resistance of the HEAs was discussed, and the oxidation mechanism was summarized. The results indicate that, at 800 °C, the AlTiNiCuCox (x = 0.5, 1.0, 1.5) series HEAs had dense oxide films and certain high-temperature oxidation resistance. With increasing Co content, the high-temperature oxidation resistance of the alloys also increased. With increasing time at high temperature, there was a significant increase in the contents of oxide species and Ti on the oxide film surface. In the process of high-temperature oxidation of AlTiNiCuCox series HEAs, the interfacial reaction, in which metal elements and oxygen in the alloy form ions through direct contact reaction, initially dominated, then the diffusion process gradually became the dominant oxidation factor as ions diffused and were transported in the oxide film.