The relationship between microstructure parameters and mechanical properties was studied in this paper. The steel was heat-treated at different austenitizing temperatures to acquire varying microstructure. The results showed that austenite grain size increases with austenitizing temperature, while the pearlite colony size was relatively constant. The strength followed a Hall–Petch relationship with the austenite grain size, but the austenite grain size has nothing to do with the impact toughness. The control unit for determining the impact toughness of pearlitic steel is the pearlite colony size using a comparison method. Further studies have found that, in the hypoeutectoid steel and hypereutectoid steel, the pearlite colony size changes with the austenitizing temperature. However, when the eutectoid steel with a carbon content of 0.81% undergoes the isothermal transformation, the number of grain boundary precipitates is very few. There are many nucleation sites at the grain boundary. The pearlite colonies randomly nucleate at the grain boundaries and grow into the interior of the grains. Simultaneously, new pearlite colonies nucleate by the side of the existing pearlite colony. The intragranular pearlite colonies are also randomly nucleated. These nucleation sites increase the chance of the growing pearlite colonies colliding with each other, eventually resulting in a constant pearlite colony size.

High-strength, multiphase steels consisting of pearlite surrounded by tempered martensite were prepared by pre-quenching and ultrafast tempering heat treatment of high-carbon pearlitic steels (0.81% C). The microstructures were analyzed by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. With an increasing quenching temperature from 120 °C to 190 °C, the quenched martensite variants nucleated via autocatalytic nucleation along the interface. Furthermore, the tempered nodules exhibited a distinct symmetrical structure, and the tempered martensite and pearlitic colonies in the group also showed a symmetrical morphology. In addition, a reasonable model was formulated to explain the transformation process from quenching martensite to the multiphase microstructure. When the quenching temperature was set to 120 °C, followed by ultrafast heating at 200 °C/s to 600 °C and subsequent isothermal treatment for 60 s, the multiphase structure showed highest strength, and the pearlite volume fraction after tempering was the lowest. The microhardness softening mechanism for the tempered structures consisted of two stages. The first stage is related to martensitic sheets undergoing reverse transformation and the nucleation of cementite on dislocations. The second stage involves the transformation of austenite into pearlite and continued carbide coarsening in the martensitic matrix.

In order to fabricate the artificial bone with high bioactive property, lead-free barium titanate (BaTiO3, BT) piezoelectric material added hydroxyapatite (HA) composites were prepared in this study. Compared with the pure HA materials, the introduction of BT can increase the electrical properties of the samples while ensuring good biological properties. The electrical properties, such as piezoelectric constant d33, hysteresis loop and dielectric spectrum were measured, respectively. The bending strength, Vickers hardness, cytotoxicity and osteogenic property of the BT/HA composites were also discussed. It is revealed that the non-toxic sample with 95 wt% BT and 5 wt% HA (95BT+5HA) has the best osteoinductivity, the piezoelectric constant d33 of which is 79.2 pC N-1. The bending strength and Vickers hardness of the 95BT+5HA sample are 138.3 MPa and 472.4, respectively, realizing the desired mechanical properties of human bones. Comprehensive analyses of various properties show that the 95BT+5HA composite can meet the requirements of artificial bone, and is expected to be a promising generation of substitute bone materials.

Lead-free (Bi_1/2Na_1/2)(Ti_1−x(Mg_1/3Nb_2/3)_x)O₃ ceramics were synthesized using the solid-phase method, and the effects of varying (Mg_1/3Nb_2/3)⁴⁺ content, substituting for Ti⁴⁺ ions at the B-site of the BNT perovskite lattice, on piezoelectric performance were systematically investigated. The influence of sintering temperature on both piezoelectric and ferroelectric properties was also explored, revealing that sintering temperature significantly affects both the microstructure and the electrical properties of the ceramics. The results indicate that the incorporation of (Mg_1/3Nb_2/3)⁴⁺ significantly enhances the piezoelectric and ferroelectric properties of BNT ceramics. Specifically, a maximum piezoelectric constant of 91 pC/N was achieved at a sintering temperature of 1160 °C and a doping concentration of x = 0.01. By comparing the ferroelectric properties across different doping levels and sintering temperatures, this study provides valuable insights for further design and process optimization of BNT-based piezoelectric materials.

Background Periodontitis is a risk factor linked to Alzheimer's disease (AD), and amyloid-beta (Aβ) is a pathological characteristic of AD. Increasing evidence suggests that periodontitis contributes to the formation and progression of AD. Type I interferons are upregulated in Porphyromonas gingivalis (Pg)-induced periodontitis in mice. Colonization of Pg has been identified in the brains of patients with AD. Recently, interferon-induced transmembrane protein 3 (IFITM3), an inflammation-induced innate immunity protein, was identified as a novel γ-secretase modulatory protein for Aβ production in AD. However, it is unknown whether periodontitis also increases type I interferons in the brain and induces AD-like pathology by triggering the innate immune response of glial cells and activating the IFITM3-Aβ axis. Whether colonization of Pg in brain induces innate immune in astrocytes and microglia remains elusive. Methods We evaluated the effects of periodontitis on cognitive impairment in C57BL/6J and APP/PS1 mice using behavioral tests. The effects of Periodontitis/Pg on microglia and astrocytes were measured using qRT-PCR, western blotting, and histological staining. Results Pg-induced periodontitis caused cognitive impairment in C57BL/6J mice and exacerbated a cognitive decline in APP/PS1 mice. Furthermore, periodontitis increased the level of interferon (IFN)-β, IFITM3, and Aβ deposition of C57BL/6J and APP/PS1 mice in the brain. And we identified Pg DNA, apoptotic cells, glial activation, and the expression of inflammatory mediators in the brain of a mouse periodontitis model. Furthermore, our results confirmed that astrocytes were the main responders to Pg-induced innate immunity and inflammation in vitro and in vivo. Periodontitis also induces an increase in IFITM3 expression in periodontal tissue, salivary glands, and saliva. Conclusions We define a previously unidentified link between periodontitis and cognitive decline, and provide new evidence linking oral pathogenic bacteria-induced innate immunity and neuroinflammation to AD pathogenesis and cognitive decline in part by disrupting the BBB, triggering neuroinflammation and increasing IFITM3 in glial cells for Aβ deposition. Periodontitis also exacerbates innate immunity and cognitive impairment in AD mice, which implies the necessity of preventing and controlling periodontal disease in AD patients.

The development of effective biomaterials for bone defect repair remains challenging due to limitations in mechanical properties, bioactivity, and degradation characteristics. We summarize recent progress in synthetic bone materials, including metals, ceramics, and polymer composites, critically analyzing their clinical strengths and weaknesses. This review presents the fabrication of a new generation of mineralized collagen materials through biomimetic mineralization, demonstrating that their composites exhibit promising clinical application potential. Inspired by the hierarchical architecture of natural bone, a multiscale cascade regulation strategy is further proposed to achieve multidimensional mimicry in composition, structure, mechanical properties, and biological functionality. Special attention is given to multidimensional biomimetic strategies integrating nano-scale molecular self-assembly, electrospinning, and macroscale pressure-driven fusion to construct artificial lamellar bone and artificial cortical bone. In summary, this article provides valuable insights into understanding artificial bone repair materials and their development trends, offering significant guidance for the development of new degradable biomimetic artificial compact bone materials.