Sodium monofluorophosphate (Na2FPO3, MFP) is mainly used as an ingredient in fluoride-based dentifrices as it has a high safety profile, with one-third of the toxicity of sodium fluoride (NaF), as well as the ability to reach deep into the dentin. The purpose of this study was to assess the prevention of dentin erosion by MFP upon exposure to citric acid, which has a chelating effect, and to compare the effects to those of the conventional acidulated phosphate fluoride (APF) application method. Bovine dentin was used, and four groups were created: (i) APF (9000 ppmF, pH 3.6) 4 min group; (ii) acidulated phosphate MFP (AP-MFP, 9000 ppmF, pH 3.6) 4 min group; (iii) AP-MFP 2 min + APF 2 min (dual) group; and (iv) no fluoride application (control) group. Compared with the conventional APF application method, the application of AP-MFP was shown to significantly reduce substantial defects, mineral loss, and lesion depth; better maintain Vickers hardness; and promote the homogenous aggregation of fine CaF2 particles to seal the dentin tubules, enhancing acid resistance in their vicinity. The ΔZ value of the AP-MFP group was 2679 ± 290.2 vol% μm, significantly smaller than the APF group’s 3806 ± 257.5 vol% μm (p < 0.01). Thus, AP-MFP-based fluoride application could effectively suppress citric acid-induced demineralization and could become a new, more powerful, and biologically safer professional-care method for preventing acid-induced dentin erosion than the conventional method.

Herein, we report the synthesis, structural and microstructural characterization, and thermoelectric properties of AgSnm[Sb0.8Bi0.2]Te2+m and Br-doped telluride systems. These compounds were prepared by solid-state reaction at high temperature. Powder X-ray diffraction data reveal that these samples exhibit crystal structures related to the NaCl-type lattice. The microstructures and morphologies are investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and high-resolution transmission electron microscopy (HRTEM). Positive values of the Seebeck coefficient (S) indicate that the transport properties are dominated by holes. The S of undoped AgSnm[Sb0.8Bi0.2]Te2+m ranges from +40 to 57 μV·K−1. Br-doped samples with m = 2 show S values of +74 μV·K−1 at RT, and the Seebeck coefficient increases almost linearly with increasing temperature. The total thermal conductivity (κtot) monotonically increases with increasing temperature (10–300 K). The κtot values of undoped AgSnm[Sb0.8Bi0.2]Te2+m are ~1.8 W m−1 K−1 (m = 4) and ~1.0 W m−1 K−1 (m = 2) at 300 K. The electrical conductivity (σ) decreases almost linearly with increasing temperature, indicating metal-like behavior. The ZT value increases as a function of temperature. A maximum ZT value of ~0.07 is achieved at room temperature for the Br-doped phase with m = 4.

Aluminum–silicon alloys require modification due to their coarse-grained microstructures and resulting low strength properties. So far, research into the modification process has focused on the use of various chemical components and technological processes, the tasks of which are to refine the microstructure and, thus, increase the mechanical properties of the alloy. In this paper, the answer to the question of whether the form of the modifier influences the modification effect of the hypoeutectic silumin will be found. The tests were carried out using the popular silumin AlSi7Mg. To answer our research question, the alloy was modified under comparable conditions using the following elements: Ti, B, and master alloys AlTi1.5 and AlB1.5. Modifiers in the form of Sr and master alloy AlSr1.5 were also used. All mentioned modifiers were produced and introduced into the liquid alloy in the form of a powder and a rod. Master alloys AlSr1.5 were also produced via cooling from the liquid state through cooling in air and the second variant at a speed of 200 °C/s (in the form of powder and a thin strip). The microstructure and mechanical properties were analyzed based on the following measures: tensile strength, elongation, and hardness of silumin. Based on the conducted research, it was found that the form of the modifier also affects the modification effect visible in the form of changes in the microstructure and mechanical properties. For the powder-modified alloy, greater fineness in the eutectic phase (α and B phases) and an increase in all analyzed mechanical properties were obtained.

Steel strands are widely used in structures such as bridge cables, and their integrity is critical to keeping these structures safe. A steel strand is under the working condition of an alternating load for a long time, and fatigue damage is unavoidable. It is necessary to find characteristic parameters for evaluating fatigue damage. In this study, nonlinear coefficients and attenuation coefficients were employed to evaluate fatigue damage based on magnetostrictive guided wave testing. Unlike pipe and steel wire structures, there is a phenomenon of a notch frequency when guided waves propagate in steel strands. The influence of the notch frequency on the nonlinear coefficient and attenuation coefficient is discussed. The relationship between the nonlinear coefficient, attenuation coefficient, and cyclic loading times was obtained through experiments. The amplitudes of the nonlinear coefficient and attenuation coefficient both increased with the increase in cyclic loading times. The experiments also showed the effectiveness of using these two characteristic parameters to evaluate fatigue damage.

An effective strategy for achieving cost-effective and environmentally friendly desulfurization wastewater in coal-fired power plants involves the incorporation of desulfurization wastewater into the slag water system. The objective of this study was to analyze the corrosion behavior of Q235-A slag-picker shell material upon the introduction of FGD wastewater into the slag water system. The dynamic weight loss method, electrochemical testing method and microscopic phase characterization were employed to investigate the impact of varying chloride ion concentrations (ranging from 1000 mg/L to 30,000 mg/L) of flue gas desulfurization wastewater (FGD wastewater) on the corrosion of Q235-A slag-picker shell material. The test results indicate that as the concentration of chloride ions increases, the corrosion rate increases from 1.1487 mm/a to 1.5590 mm/a when the concentration is less than 10,000 mg/L. However, when the concentration exceeds 10,000 mg/L, the corrosion rate decreases from 1.559 mm/a to 1.0393 mm/a. The corrosion rate is above 1 mm/a at all concentrations. As the Cl− concentration, the quality of the corrosion product film initially increases and then decreases. The primary components of the corrosion product are α- FeOOH, γ-FeOOH, β-FeOOH, Fe3O4 and γ-Fe2O3.

The aim of this paper is to test the previously stated hypothesis and several experimental facts about the effect of the ion flux or ion beam current under irradiation with heavy ions on the radiation damage formation in the ceramic near-surface layer and their concentration. The hypothesis is that, when considering the possibilities of using ion irradiation (usually with heavy ions) for radiation damage simulation at a given depth, comparable to neutron irradiation, it is necessary to consider the rate factor for the set of atomic displacements and their accumulation. Using the methods of X-ray diffraction analysis, Raman and UV–Vis spectroscopy, alongside photoluminescence, the mechanisms of defect formation in the damaged layer were studied by varying the current of the Xe23+ ion beam with an energy of 230 MeV. As a result of the experimental data obtained, it was found that, with the ion beam current elevation upon the irradiation of nitride ceramics (AlN) with heavy Xe23+ ions, structural changes have a pronounced dependence on the damage accumulation rate. At the same time, the variation of the ion beam current affects the main mechanisms of defect formation in the near-surface layer. It has been found that at high values of flux ions, the dominant mechanism in damage to the surface layer is the mechanism of the formation of vacancy defects associated with the replacement of nitrogen atoms by oxygen atoms, as well as the formation of ON–VAl complexes.

Carbon-fiber-reinforced polymer (CFRP) composites are widely used in industries such as aerospace due to their lightweight nature and high strength. However, weak interfacial bonding strength is one of the main problems of resin-based composites. In this study, a prepreg was prepared by melt mixing. By dispersing nanoreinforcement particles in the resin, the interlaminar shear strength of the CFRP was increased by approximately 23.6%. When only 0.5 wt% multiwalled carbon nanotube (MWCNT) was used for reinforcement, scanning electron microscopy (SEM) micrographs showed that cracks were hindered by the MWCNTs during propagation, causing crack deflection. At the same time, the mechanism of MWCNTs pulling out increased the energy required for crack propagation. When only 0.5 wt% graphene oxide (GO) was added, the reinforcement effect was inferior to that of using the same amount of MWCNTs. The laminar structure formed by GO and the resin matrix adhered to the carbon fiber surface, reducing the degree of destruction of the resin matrix, but its hindering effect on crack propagation was weak. When 0.5 wt% of MWCNT and GO mixture was added, the interlayer shear strength increased from 55.6 MPa in the blank group to 68.7 MPa. The laminar structure of GO provided a platform for the MWCNTs to form a mesh structure inside its matrix. At the same time, the tubular structure of the MWCNTs inhibited the stacking of GO, providing better dispersion and forming a synergistic enhancement effect.

An experimental study of the abrasive water jet cutting process of Inconel 718 alloy samples with varying values of cutting speed, abrasive flow rate and cutting material height was carried out. Surface roughness and waviness were measured at different cutting depths, and the variation of the kerf angle was studied. It was shown that the depth of cut has the greatest effect on roughness and waviness. The height of the sample has no impact on the roughness and waviness at a particular depth of cut. As the depth of cut increases, in most cases, roughness and waviness increase as well. It has been proven that the cutting speed has a negligible effect on surface roughness, but it has a significant effect on surface waviness. The waviness, on the other hand, depends only slightly on the abrasive flow. It has been proven that the kerf angle does not depend on the abrasive flow. The kerf angle depends mainly on the height of the sample. The models were developed for the parameters of roughness Ra and Rz, waviness Wa and Wz and kerf angle. All models were calculated without separating the surface into smooth and rough cutting regions.

Re-entrant auxetics offer the potential to address lightweight challenges while exhibiting superior impact resistance, energy absorption capacity, and a synclastic curvature deformation mechanism for a wide range of engineering applications. This paper presents a systematic numerical study on the compressive and flexural behaviour of re-entrant honeycomb and 3D re-entrant lattice using the finite element method implemented with ABAQUS/Explicit, in comparison with that of regular hexagonal honeycomb. The finite element model was validated with experimental data obtained from the literature, followed by a mesh size sensitivity analysis performed to determine the optimal element size. A series of simulations was then conducted to investigate the failure mechanisms and effects of different factors including strain rate, relative density, unit cell number, and material property on the dynamic response of re-entrant auxetics subjected to axial and flexural loading. The simulation results indicate that 3D re-entrant lattice is superior to hexagonal honeycomb and re-entrant honeycomb in energy dissipation, which is insensitive to unit cell number. Replacing re-entrant honeycomb with 3D re-entrant lattice leads to an 884% increase in plastic energy dissipation and a 694% rise in initial peak stress. Under flexural loading, the re-entrant honeycomb shows a small flexural modulus, but maintains the elastic deformation regime over a large range of strain. In all cases, the compressive and flexural dynamic response of re-entrant auxetics exhibits a strong dependence on strain rate, relative density, and material property. This study provides intuitive insight into the compressive and flexural performance of re-entrant auxetics, which can facilitate the optimal design of auxetic composites.

This paper introduces a new type of gypsum-based humidity-control material. The material combines gypsum–silica gel humidity-control material with 20% sepiolite powder activated by calcium chloride. Both experimental and simulation studies were conducted to assess its humidity-control performance. The experimental results indicate that gypsum-based humidity-control material has the property of absorbing moisture in high-humidity environments and releasing moisture in low-humidity environments. Moreover, both environmental temperature and relative humidity (RH) have an impact on the material’s humidity-control performance. At a relative humidity of 97.4%, the maximum equilibrium moisture content of the material is 0.225 g/g, which is 1.4 times that of the gypsum–silica gel humidity-control material and 4.5 times that of pure gypsum material. The simulation results indicate that gypsum-based humidity-control material effectively mitigates indoor relative humidity fluctuations and maintains indoor air relative humidity within a narrow range. Furthermore, the material has the potential to reduce building energy consumption. This is especially evident under climate conditions with large temperature and relative humidity differences between day and night, such as in Beijing, Paris, and Atlanta. The maximum potential energy-saving rate in Beijing can reach up to 19.31%.

This study assessed the modification effects of zirconia-based nanopowder and cement contents and curing age on the mechanical properties of silty soil. The orthogonal test design was applied to derive the best combination of each influencing factor using the lateral unconfined compressive test. Two-dimensional particle flow code (PFC2D) distinct-element modeling software was also used to fit and analyze the test curves, as well as simulate the triaxial test with the derived parameters. The test results reveal the optimal combination of 20% cement, 2% zirconia-based nanopowder, and 28 d curing age. The extreme difference table was used to plot the orthogonal trend diagram, and cement content was found to be the most significant factor controlling the silty soil strength. The maximum peak stress was 2196.33 kPa under the optimum combination of factors, which could be obtained through the index estimation, and these results were experimentally verified. According to the predicted strength envelope, the cohesive force of nanopowder-cement-modified silty soil in the optimal proportion was 717.11 kPa, and the internal friction angle was 21.05°. Nano zirconium dioxide will accelerate the hydration reaction of cement, the flocculent structure produced by the hydration of cement and soil particles connected to each other, play the role of filling and anchoring, and thus increase the strength of the nano-zirconium dioxide, and the optimal dosage of nano-zirconium dioxide is 2%.

Numerous studies have been conducted on fiber-reinforced concrete; however, comparative investigations specifically focusing on the utilization of fibers in CLSM remain limited. In this study, we conducted a systematic investigation into the mechanical properties of controlled low-strength material (CLSM) by manipulating the length and doping amount of fibers as control variables. The 7-day compressive strength (7d-UCS), 28-day compressive strength (28d-UCS), and 28-day splitting strength of CLSM were employed as indicators to evaluate the material’s performance. Based on our comprehensive analysis, the following conclusions were drawn: (1) A positive correlation was observed between fiber length and material strength within the range of 0–6 mm, while conversely, a negative correlation was evident. Similarly, when the fiber doping was within the range of 0–0.3%, a positive correlation was identified between material strength and fiber doping. However, the strength of CLSM decreased when fiber doping exceeded 0.3%. (2) SEM and PCAS analyses provided further confirmation that the incorporation of fibers effectively reduced the porosity of the material by filling internal pores and interacting with hydration products, thereby forming a mesh structure. Overall, this study offers valuable insights into the manipulation of fiber length and doping amount to optimize the mechanical properties of CLSM. The findings have important implications for the practical application of CLSM, particularly in terms of enhancing its strength through fiber incorporation.

The forging–healing of the internal porosity defects affects the tensile, impact and fatigue properties of heavy forgings. In the present work, the effect of deformation process on the microstructure in the joint area as well as the tensile strength, impact toughness and fatigue strength was studied experimentally. It is shown that the tensile strength is restored once the porosity defects were healed, and the impact toughness is recovered when the flat grain band is eliminated. The fatigue strength can be restored if a uniform grain structure can be achieved in both the joint area and the matrix, whereafter precipitate become the key factor affecting the fatigue strength. A complete healing of the porosity defects, a uniform grain structure in the joint area and the matrix, and a fully controlled precipitate are essential to guarantee the mechanical properties and in-service performance of the heavy forgings.

Wood-based composites are increasingly used in the industry not only because of the shortage of solid wood, but above all because of the better properties, such as high strength and aesthetic appearance compared to wood. Medium-density fiberboard (MDF) is a wood-based composite that is widely used in the furniture industry. In this work, an attempt was made to predict the surface roughness of the machined MDF in the milling process based on acceleration signals from an industrial piezoelectric sensor installed in the cutting zone. The surface roughness parameter Sq was adopted for the evaluation and measurement of surface roughness. The surface roughness prediction was performed using a radial basis function (RBF) artificial neural network (ANN) and a Takagi–Sugeno––Kang (TSK) fuzzy model with subtractive clustering. In the research, as inputs to the ANNs and fuzzy model, the kinematic parameters of the cutting process and selected measures of the acceleration signal were adopted. At the output, the values of the surface roughness parameter Sq were obtained. The results of the experiments show that the surface roughness is influenced not only by the kinematic parameters of the cutting, but also by the vibrations generated during the milling process. Therefore, by combining information on the cutting kinematics parameters and vibration, the accuracy of the surface roughness prediction in the milling process of MDF can be improved. The use of TSK fuzzy modelling based on the subtractive clustering method for integrating the information from many acceleration signal measurements in the examined range of cutting conditions meant the surface roughness was predicted with high accuracy and high reliability. With the help of two tested artificial intelligence tools, it is possible to estimate the surface roughness of the workpiece with only a small error. When using a radial neural network, the root mean square error for estimating the value of the Sq parameter was 0.379 μm, while the estimation error based on fuzzy logic was 0.198 μm. The surface of the sample made with the cutting parameters vc = 76 m/min and vf = 1200 mm/min is characterized by a less concentrated distribution of ordinate densities, compared to the surface of the sample cut with lower feed rates but at the same cutting speed. The most concentrated distribution of ordinate density (for the cutting speed vc = 76 m/min) is characterized by the surface, where the feed rate value was vf = 200 mm/min, with 90% of the material concentrated in the profile height of 28.2 μm. When using an RBF neural network, the RMSE of estimating the value of the Sq parameter was 0.379 μm, while the estimation error based on fuzzy logic was 0.198 μm.

The objective of this study was to investigate and visualize the initiation and propagation of crevice corrosion in grade 2205 duplex stainless steel by means of time-lapse imaging. Transparent Poly-Methyl-Meth-Acrylate washer and disk were coupled with duplex stainless steel to create an artificial crevice, with electrochemical monitoring applied to obtain information about the nucleation and propagation characteristics. All nucleation sites and corroding areas inside crevices were recorded in situ using a digital microscope set-up. Localized corrosion initiated close to the edge of the washer, where the crevice gap was very tight, with active corrosion sites then propagating underneath the disk into areas with wider gaps, towards the crevice mouth. The growth was associated with a rise in anodic current interlaced with sudden current drops, with parallel hydrogen gas evolution also observed within the crevice. The current drops were associated with a sudden change in growth direction, and once corrosion reached the crevice mouth, the propagation continued circumferentially and in depth. This allowed different corrosion regions to develop, showing selective dissolution of austenite, a region with dissolution of both phases, followed by a region where only ferrite dissolved. The effect of applied electrochemical potential, combined with time-lapse imaging, provides a powerful tool for in situ corrosion studies.

The formation of a cellular hierarchically organized NiO film on a carbon paper substrate under hydrothermal conditions using triethanolamine as a base has been studied. The thermal behavior of the carbon paper substrate with the applied semi-product shell was studied using synchronous thermal analysis (TGA/DSC) and it was demonstrated that such modification of the material surface leads to a noticeable increase in its thermal stability. Using scanning electron microscopy (SEM), it was shown that the NiO film grown on the carbon fiber surface is characterized by a complex cellular morphology, organized by partially layered individual nanosheets of about 4–5 nm thickness and lateral dimensions up to 1–2 μm, some edges and folds of which are located vertically relative to the carbon fiber surface. The surface of the obtained material was also examined using atomic force microscopy (AFM), and the electronic work function of the oxide shell surface was evaluated using the Kelvin probe force microscopy (KPFM) method. The electrochemical parameters of the obtained flexible NiO/CP electrode were analyzed: the dependence of the specific capacitance on the current density was determined and the stability of the material during cycling was studied, which showed that the proposed approach is promising for manufacturing hierarchically organized electrodes for flexible supercapacitors.

Structural steels and alloys represent a wide domain of materials whose development directly affects human civilization [...]

Titanium alloy Ti6Al4V is a commonly used bone implant material, primarily prepared as a porous material to better match the elastic modulus of human bone. However, titanium alloy is biologically inert and does not have antibacterial properties. At the same time, the porous structure with a large specific surface area also increases the risk of infection, leading to surgical failure. In this paper, we prepared three porous samples with different porosities of 60%, 75%, and 85%, respectively (for short, 3D-60, 3D-75, and 3D-85) using 3D printing technology and clarified the mechanical properties. Through tensile experiments, when the porosity was 60%, the compressive modulus was within the elastic modulus of human bone. Anodic oxidation technology carried out the surface modification of a 3D-printed porous titanium alloy with 60% porosity. Through change, the different voltages and times on the TiO2 oxide layer on the 3D-printed porous titanium alloy are different, and it reveals the growth mechanism of the TiO2 oxide layer on a 3D-printed unique titanium alloy. The surface hydrophilic and antibacterial properties of 3D-printed porous titanium alloy were significantly improved after modification by anodic oxidation.

The microbiologically influenced corrosion of 201 stainless steel by Shewanella algae was investigated via modulating the concentration of fumarate (electron acceptor) in the medium and constructing mutant strains induced by ΔOmcA. The ICP-MS and electrochemical tests showed that the presence of S. algae enhanced the degradation of the passive film; the lack of an electron acceptor further aggravated the effect and mainly affected the early stage of MIC. The electrochemical tests and atomic force microscopy characterization revealed that the ability of ΔOmcA to transfer electrons to the passive film was significantly reduced in the absence of the c-type cytochrome OmcA related to EET progress, leading to the lower corrosion rate of the steel.

The paper presents the results of tests of rapid solidification (RS) aluminum alloys with the addition of silicon (5%, 11%, and 20%). Casting by melt-spinning on the surface of an intensively cooled copper cylinder allowed to obtain a metallic material in the form of flakes, which were then consolidated in the process of pressing and direct extrusion. The effect of refinement on structural components after rapid solidification was determined. Rapidly solidified AlSi materials are characterized by a comparable size of Si particles, regardless of the silicon content, and the shape of these particles is close to spheroidal. Not only Si particles are fragmented, but also the Al-Si-Fe phase, which also changed its shape from irregular with sharp edges to regular and spherical. The melt-spinning process resulted in a fine-grained structure compared to materials obtained by gravity-casting and extrusion. The influence of the high-temperature compression test on the mechanical properties of rapidly solidified materials was analyzed, and the results were compared with those of gravity-cast materials. An increase in strength properties was found in the case of the AlSi5 RS alloy by 20%, in the case of AlSi11RS by 25%, and in the case of the alloy containing 20% Si by as much as 86% (tensile test). On the basis of the homogeneity of the particle distribution determined by the SEM method, it was found that rapid solidification is an effective method of increasing the strength properties and improving the plastic properties of Al-Si alloys.