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Molecular dynamics simulations allow to investigate the microscopic evolution of a structure, and can also point the way to tool material design. In this paper, the effect of adding CaF2 and CaF2@SiO2 on the Si3N4/TiC system is studied using molecular dynamics simulations. The results show that the system with the addition of CaF2@SiO2 to the model has a higher hardness than the system with the addition of CaF2. In order to obtain the optimum parameters for self-lubricating ceramic tools, the effect of adding different amounts of CaF2@SiO2 on the Si3N4/TiC system was investigated. The Si3N4/TiC/CaF2@SiO2 system achieved optimum mechanical properties when four CaF2@SiO2 were included in the model. By analyzing the effect of the sintering temperature on the system, it was deduced that the hardness achieved a maximum value of 15.89 GPa and the modulus of elasticity reached 132.53 GPa when the sintering temperature was at 2073 K. Based on this sintering parameter, the Si3N4/TiC/CaF2@SiO2 composite ceramic tool material was experimentally prepared with the mechanical properties of 15.66 GPa hardness and 128.08 GPa modulus of elasticity. The experimental results were consistent with the simulation results.

A gradient nano self-lubricating ceramic cutting tool material was prepared by vacuum hot-pressing sintering technique. The composition of each layer is designed in a gradient so that the nano-sized solid lubricant content is gradually reduced from the surface to the center, and residual compressive stresses are formed in the tool surface. The components and microstructure of the prepared ceramic tools showed gradient changes, with clear and well-bonded interfaces between the gradient layers. Compared with the mechanical properties of homogeneous tool, the flexural strength, fracture toughness, and hardness of this ceramic tool were increased by 74.0%, 3.9%, and 5.0%, respectively. The gradient design had little effect on the friction coefficient, but the improved mechanical properties and the presence of residual compressive stresses in the surface layer improved the wear resistance of the tool. The higher the friction speed and load, the more effectively the gradient design will improve the wear rate.

ZrB2/SiC ceramic granules with uniform a size and spherical shape were prepared by spray drying technology. ZrB2/SiC ceramic granules were added into ceramic matrix, and ZrB2/SiC/Si3N4 ceramic tool materials with double composite architectures were prepared by spark plasma sintering technology. The mechanical properties from room temperature to 1100°C were measured. The hardness, flexural strength and fracture toughness at room temperature are 18.0 GPa, 589.0 MPa and 5.93 MPa m1/2, respectively. While the fracture toughness at 1100°C reach 6.1 MPa m1/2 increase by 74.3% compared with the ceramic tool material without double composite architectures. At high temperature, the improvement of fracture toughness is due to the addition of ZrB2/SiC ceramic granules that deflect the cracks and propagates along the boundary between the granules and the matrix, which greatly increase the path during the crack propagation process, thereby improving the fracture toughness of the ceramic tool material.

Based on the finite element model, laminated graphene ceramic tool materials were designed, and the effects of the number of layers and thickness ratio on the residual stress were investigated. According to the simulation design results, laminated Al2O3–TiB2–graphene/Al2O3–TiN (ATBGN) ceramic tool materials with various structures were prepared using the spark plasma sintering process, and their mechanical properties and microstructures were studied and analyzed. The fracture toughness and flexural strength of ATBGN were 8.65 ± 0.18 MPa m1/2 and 755 ± 25 MPa, respectively, which increased by 66.7% and 21.6%, respectively, compared to those of monolithic Al2O3–TiB2 ceramic. Under the synergistic action of graphene and residual compressive stress, the multiscale deflection of cracks and the change in fracture mode occurred, which made the substantial contribution to the improvement in mechanical properties.

Core-shell particles are considered to be one of the primary strengthening and toughening methods of cermet. In this study, a (W,Ti,Ta)C based cermet was prepared by vacuum hot pressing sintering technology with the addition of c-BN@Al2O3 (Al2O3 coated c-BN). Localized high residual stress around the core-shell particles causes the strengthening and toughening mechanism at short distances behind the crack tip, such as crack deflection, secondary cracks, crack branching, and grain pull-out, even at a small volume fraction of 10 vol%. Compared with cermet without Al2O3 and c-BN, the flexural strength and fracture toughness of the cermet with 10 vol% c-BN@Al2O3 are increased by 35.62% and 28.45%, reaching 1462 ± 49 MPa and 13.68 ± 0.51 MPa m1/2, respectively.

Tool wear damages the surface quality of the workpiece and increases equipment downtime. Tool wear prediction is of great importance for reducing processing costs and improving processing efficiency. This paper applies multisensor fusion technology to predict tool wear. The cutting force, vibration, and acoustic emission signals are collected simultaneously during the milling process. The time domain, frequency domain, and time–frequency domain characteristics of each signal are extracted, reduced, and filtered through correlation analysis. A GSA-BP prediction model is established by a BP neural network in which the weights and thresholds are optimized through the gravitational search algorithm (GSA). The test results show that the prediction results of the GSA-BP model are in good agreement with the actual wear, and the prediction accuracy is higher than that of the traditional BP neural network model.

We studied the effects of peak temperature and cooling rate in the secondary welding thermal cycles on the martensite/austenite (M/A) constituents’ characteristics (including fraction, average size and distribution), corrosion resistance and hydrogen permeation behaviors in the inter-critically reheated coarse-grained heat-affected zone (ICCGHAZ) of X80 pipeline steel. We observed that the M/A constituents’ characteristics mainly depend on the secondary peak temperature and cooling rates, while the microstructure style and prior austenite grain size are dependent on the first peak temperature. In addition, the variations in the M/A constituents’ characteristics result in different corrosion resistance and hydrogen permeation behaviors by changing the micro-galvanic effect and the number of hydrogen trapping sites. The high fraction and coarse grain size of M/A constituents are against the corrosion resistance and hydrogen permeation in ICCGHAZs, and their functional relationships are established. Moreover, the effects of the fraction of M/A constituents on the corrosion resistance and hydrogen permeation behaviors are much greater than those of the average size.

The addition of CaF

Al2O3/TiB2 and Al2O3/TiB2/graphene nanoplatelets (GNPs) ceramic tool materials were prepared by spark plasma sintering, and the effect of the sintering parameters and different GNPs addition amounts on the densification, mechanical properties, and microstructure have been investigated. The optimum comprehensive mechanical properties of Al2O3/TiB2 were obtained at synthesis conditions of 1525 °C under 30 MPa for 5 min. However, the addition of GNPs could promote the densification and improve the mechanical properties. The results show that the ceramic tool material with 0.3 wt% GNPs exhibits mechanical properties superior to those of pure Al2O3/TiB2; the fracture toughness increases by 41.6% and reaches the maximum value of 7.35 ± 0.23 MPa m1/2, and the flexural strength increases by 6.4%–661 ± 16 MPa. The toughening mechanisms of Al2O3/TiB2/GNPs are explained by graphene pull-out, crack bridging, branching and deflection.

Colorectal cancer (CRC) is associated with one of the highest rates of mortality among cancers worldwide. The early detection and management of CRC is imperative. Biomarkers play an important role in CRC screening tests, CRC treatment, and prognosis and clinical management; thus rapid and sensitive detection of biomarkers is helpful for early detection of CRC. In recent years, electrochemical biosensors for detecting CRC biomarkers have been widely investigated. In this review, different electrochemical detection methods for CRC biomarkers including immunosensors, aptasensors, and genosensors are summarized. Further, representative examples are provided that demonstrate the advantages of electrochemical sensors modified by various nanomaterials. Finally, the limitations and prospects of biomarkers and electrochemical sensors in detection are also discussed. Graphical abstract.

A novel ceramic coating-like (CCL) structure was proposed for preparing a potential ceramic cutting tool material. The influence of critical factors, including the material composition, composition content and surface layer thickness, on the residual stress was analyzed by the finite element method (FEM). Under the condition of the optimized parameters, the compressive stress generated on the surface layer of the CCL tool material ranged from −163 MPa to −248 MPa. Based on the obtained results, a (Ti,W)C/Al2O3+SiC CCL tool material was prepared by vacuum hot-pressing sintering, indicating the residual compressive stress (−122.3 MPa) of the surface layer. Compared with the performance of homogeneous cermet materials, the surface hardness and flexural strength of the CCL tool materials were increased by 46.58% and 37.76%, respectively. Moreover, the SEM imaging results of the sample surface and fracture morphology and the energy dispersive spectroscopy (EDS) analysis results showed that the dense ceramic surface and phase interfacial transition layer were formed with a uniform gradient distribution and without defects.

Cutting force in lathe work is closely related to tool wear and affects the turning quality. Direct measurement of the cutting force by measuring the strain of the tool holder is challenging because the tool holder design aims to be highly rigid in order to undertake large cutting forces. Accordingly, the most popular dynamometer designs modify the standard tool holder by decreasing the structural rigidity of the holder, which reduces the machining precision and is not widely accepted. In order to solve the issue of the low stiffness of the dynamometer reducing the machining precision, in this paper, the ultra-low strain on the tool holder was successfully detected by the highly sensitive semiconductor strain gauges (SCSG) adjacent to the blade cutting insert. However, the cutting process would generate much heat, which increases the force measuring area temperature of the tool holder by about 30 °C. As a result, the readout drifted significantly with the temperature changes due to the high temperature coefficient of SCSG. To solve this problem, the temperature on the tool holder was monitored and a BP neural network was proposed to compensate for temperature drift errors. Our methods improved the sensitivity (1.14 × 10−2 mV/N) and the average relative error of the BP neural network prediction (≤1.48%) while maintaining the original stiffness of the tool holder. The smart tool holder developed possesses high natural frequency (≥6 kHz), it is very suitable for dynamic cutting-force measurement. The cutting experiment data in the lathe work show comparable performance with the traditional dynamometers and the resolution of the smart tool holder is 2 N (0.25% of total range).

The machinability and wear reduction mechanism of self-repairing and self-lubricating ceramic tools sintered by vacuum hot-pressing method in the dry turning of 40Cr hardened steel were studied. By comparing the cutting performance and wear morphology of AT (Al2O3/TiC) ceramic tools under different cutting parameters, it was found that AT10B@5 (Al2O3/TiC/10 vol% TiB2/5 vol%h-BN@Al2O3) tool has a longer service life and better machining quality. Owing to the precipitation of solid lubricant during the cutting of AT10B@5 ceramic tool, the friction force during the cutting is reduced, thus decreasing the cutting force and cutting temperature of AT10B@5 ceramic tool during the cutting. The main cutting force decreased by 20.8%; the cutting temperature decreased by 22.2%; and the friction coefficient of front tool face decreased by 11.6% compared with AT tool. This effectively improved the surface quality of working parts, reduced the tool wear, increased the processing quality of work piece, and prolonged the tool life.

Alumina-coated cubic boron nitride (c-BN) particles (c-BN@Al2O3) were prepared using a heterogeneous nucleation method. Then, they were added to a (Ti,W)C-based cermet tool material after synthesis via vacuum hot-press sintering. The microstructure and mechanical properties of the (Ti,W)C-based cermet tool material with varying c-BN@Al2O3 contents were recorded and analyzed. The results show that with increasing c-BN@Al2O3 concentration, the relative density, flexural strength, fracture toughness, and Vickers hardness all increase first and then decrease, and the average grain size first decreases and then increases. The introduction of Al2O3 into the c-BN particles used for surface modification can improve the wettability and interfacial bonding strength between the c-BN and matrix particles, restrain the grain growth of the matrix particles, and improve the flexural strength of cermet tool materials. The addition of c-BN@Al2O3 also alters the crack propagation mechanism of the cermet tool material and introduces multiple toughening mechanisms to improve the fracture toughness of the cermet tool material. The high hardness of c-BN and Al2O3 is the main reason for the increase in hardness; however, excessive addition of such material reduces the relative density, resulting in a decrease in hardness.

Tribological performance between 45 hardened steel and Si3N4/TiC based composite ceramic tool materials containing 5 wt% graphene platelets with different orientation angle of graphene have been investigated by pin-on-disc tests in dry sliding conditions. The experimental results show that the composite ceramic tool materials with different orientation angle of graphene have different friction coefficients and wear rates. The friction coefficient and wear rate of the developed ceramic tool materials with the 30°orientation angle is 0.46 and 4.29 × 10-6 mm3/N·m, respectively, which is decreased by 31.3% and 63.0% compared with that of the commonly distributed 0° orientation angle. Experimental analysis shows that the improvement can be attributed to the uniform distribution of the adhered tribofilm and the combined effect of graphene pull-out and the contact area between graphene and the friction surface.

In recent years, as an energy storage device with a fast charge and discharge speed, long cycle life, and good stability, flexible supercapacitors (SCs) have been extensively used in flexible electronic devices such as smart textiles, flexible display screens, and micro-robots. Combining the advantages of conductive materials and hydrogels, conductive polymer hydrogels have good flexibility, biocompatibility, and adjustable mechanical and electrochemical properties, which enable them to be used as electrolyte or electrode materials for flexible SCs, endowing flexible SCs with various excellent properties and meeting their various working requirements. This paper comprehensively reviews the flexible SCs based on conductive polymer hydrogels, from the design, synthesis and application aspects of conductive polymer hydrogels, the various superior functions (e.g., self-healing, high stretchability and compressibility, high toughness, electrochromic and shape memory) of flexible SCs based on conductive polymer hydrogels to different structures of flexible SCs, including fiber-shaped structures, all-in-one sandwich structures, and in-plane interdigital microstructures. Finally, we summarize the challenges faced by flexible SCs based on conductive polymer hydrogels, which provides new research directions and prospects for future development in this field.

In this study, we propose a novel method to exfoliate hexagonal boron nitride (h-BN) powders to produce boron nitride nanosheets (BNNSs) by applying the synergistic exfoliation resulting from pure shear ball milling and ultrasonication. Pure shear ball milling is based on traditional ball milling, but uses a supplemental weight block as a vertical load on the milling balls. The effects of the vertical load on the average tangential force, average normal force, and the number of contacts among the milling balls were analyzed by discrete element method (DEM) simulation. The simulation results showed that applying a vertical load to the milling balls could alter their pattern of motion. It also increased their average tangential force and number of contacts, resulting in higher exfoliation and less impact action on the bulk h-BN powders. BNNSs were respectively produced by using the proposed method, traditional ball milling combined with ultrasonication method, and the ultrasonication method. Analyses by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) have revealed that the proposed method can produce BNNSs having larger lateral sizes with higher productivity, as compared to the other two methods. The proposed method is also expected to be applicable in the production of other layered two-dimensional (2D) materials.