Silicon carbide porous ceramics are widely used in many fields because of their corrosion resistance, good thermal shock resistance, large specific surface area and superior mechanical properties. Silicon carbide porous ceramics are mainly prepared by different methods (i.e., pore-forming agent method, organic foam impregnation method, freeze-drying method, and foaming method). Among these, the foaming method with simple operation and controllable density and shape of the products is a common approach to prepare silicon carbide porous ceramics with a high porosity. However, silicon carbide porous ceramics still have the disadvantage of low mechanical properties. The In-situ generation of SiC whiskers can greatly improve the mechanical properties of the materials. Therefore, in this paper, silicon carbide whiskers self-reinforced porous ceramics were prepared by foaming method and reactive sintering with silicon carbide powder of 70% (in mass fraction) as a raw material, 30% silicon powder and carbon black as a self-bonding phase, AlF₃·3H₂O as an additive. In addition, the effect of AlF₃·3H₂O content on the phase composition, microstructure and mechanical properties of silicon carbide whiskers self-reinforced porous ceramics was also investigated.

In this work, silicon carbide powders were used as raw materials. Silicon powders and carbon black were used as self-bonding phase materials. AlF₃·3H₂O was selected as an additive. Triethanolamine dodecyl sulfate was used as a blowing agent. The ground powders were slowly added to a solution containing 0.5% Isobam 104 and 0.15% sodium carboxymethylcellulose, which was vigorously stirred in a mechanical stirrer to produce a slurry containing 50% (in volume fraction) of ground powders. Subsequently, 1.0% (in volume fraction) triethanolamine dodecyl sulphate was added to the obtained slurry and then vigorously stirred to prepare a homogeneous wet foam, which was rapidly poured into moulds with the dimensions of 160 mm × 80 mm × 40 mm and dried at ambient temperature for 48 h. Afterwards, the demoulded foam green bodies were dried at 40-100 ℃. Finally, the dried foam green bodies were fired in argon atmosphere furnace at 1600 ℃ for 2 h to obtain porous ceramics.

, The average large spherical pore size and annular pore size in as-prepared silicon carbide whiskers self-reinforced porous ceramics both firstly decrease and then increase with increasing the content of AlF₃·3H₂O from 0 to 4%. These results are due to the minimum surface free energy of the slurry with 2% AlF₃·3H₂O, leading to the stable bubbles existing in the slurry. Adding an appropriate amount of AlF₃·3H₂O can promote the formation of silicon carbide whiskers and improve the strength of as-prepared silicon carbide whiskers self-reinforced porous ceramics. At AlF₃·3H₂O content of 2%, the flexural and compressive strengths of porous ceramic samples with a porosity of 76.9% are 2.6 MPa and 3.7 MPa, respectively, which are significantly higher than those of the porous ceramic samples prepared without AlF₃·3H₂O (i.e., 1.1 MPa and 1.4 MPa). The enhanced mechanical properties can be related to the microstructure of the porous samples. The more uniform pore distribution and smallest average spherical pores and annular pores in porous sample with AlF₃·3H₂O addition of 2% are formed, resulting in improved mechanical properties of porous sample. Also, a large number of silicon carbide whiskers with the largest length are generated, which act as a reinforcing phase for further improving the mechanical properties of porous samples.

Adding an appropriate amount of AlF₃·3H₂O could promote the formation of silicon carbide whiskers and improve the strength of porous ceramic specimens. At AlF₃·3H₂O content of 2%, the flexural and compressive strengths of as-prepared silicon carbide whisker self-reinforced porous ceramic samples with a porosity of 76.9% were 2.6 MPa and 3.7 MPa, respectively. The length and the diameter of SiC_w whiskers generated in the samples were 4 μm and 62 nm, respectively, and their growth was controlled due to the gas-solid reaction mechanism.

The Clausius-Mossotti (C-M) equation is one of the most fundamental theoretical models to calculate the dielectric constant of materials. As was proposed over a century ago, it has been widely applied in dielectric material research due to its relatively simple mathematical form and clear physical interpretation. The equation, derived based on the Lorentz effective field approximation and the assumption of constant polarization, establishes a relationship among the macroscopic dielectric constant and the microscopic polarizability and unit cell volume. However, with the growing understanding of dielectric materials, it becomes clear that dielectric constant is affected by a range of additional factors, such as bond length, packing density and symmetry. These factors are not captured by the conventional C-M equation, indicating the limitations of the equation. Recently, machine learning (ML) methods show a promise in improving the prediction accuracy of dielectric properties. The ML models can outperform classical equations in terms of accuracy, but they often lack interpretability, which hinders their widespread use in material design and optimization. To address these issues, this study proposed a novel bidirectional embedding approach with domain knowledge and machine learning. The ML-based correction term was integrated into the classical C-M equation, enhancing its predictive accuracy, while retaining physical interpretability. This work could explore a potential of combining physical formulas with ML methods to create more robust and explainable models for material design.

The data of single-phase microwave dielectric ceramics were collected from published literatures and the Materials Project database. The dataset included materials whose dielectric constants were measured by the Hakki-Coleman method in a frequencies range from 5 to 18 GHz. A machine learning model identified molecular dielectric polarizability per volume (ppv), average bond length (blm) and unit cell volume (va) as the most significant contributors to the dielectric constant in a previous study. To enhance the accuracy of the C-M equation, correction terms were introduced based on the three key features. Symbolic regression, combined with genetic algorithms, was used to derive mathematical expressions for the correction terms. The symbolic regression technique utilized evolutionary algorithms to generate and evolve potential expressions. The structures and parameters of expressions were optimized to minimize prediction errors. Hyperparameters were optimized by a grid search method to identify the best-performing models. The process was carried out iteratively. A total of 16,000 candidate mathematical expressions were generated and compared. Finally, the Pareto front analysis was used to select the optimal expression that balances accuracy and complexity.

The revised C-M equation results in significant improvements in its predictive performance. For the Shannon polarizability dataset, the R² value of the revised C-M equation is increased by 42.29%, and the RMSE value is decreased by 14.72%. The correction term compensates for the inaccuracies of the original equation, particularly in cases where the molecular dielectric polarizability per volume of Shannon value (ppv_s) is either overestimated or underestimated. For low-polarizability materials with ppv_s values less than 0.2087, the Shannon database tends to underestimate the dielectric constant, and the correction term compensates for this error. Conversely, for high-polarizability materials, the dielectric constant is often overestimated, and the correction term reduces the overestimation. The analysis of the relationship between the correction term (Δppv_s) and features reveals that the correction term is most sensitive to ppv_s, followed by blm, with va having the least impact. This finding indicates that the dielectric polarizability plays a dominant role in determining the accuracy of the revised C-M equation. The influence of the features on the correction term is further explored through partial derivatives. The first-order partial derivatives show that the correction term's contribution from ppv_s is much greater than that from blm or va. The second-order partial derivatives reveal a non-linear relationship between the correction term and ppv_s and blm, while the relationship with va is linear. The results indicate that the compensatory effect of the correction term gradually diminishes, and the suppression effect becomes more pronounced as ppv_s increases. This behavior is consistent with the correction mechanism of "elevating the underrated, reducing the overrated".

This study introduced a bidirectional embedding approach that could integrate machine learning with domain knowledge to enhance both the accuracy and interpretability of the Clausius-Mossotti equation. The revised equation achieved a higher prediction accuracy with a 42.29% increase in R² and a 14.72% decrease in RMSE via incorporating the correction term derived from symbolic regression. The revised equation retained the physical meaning of the original one. The research could highlight a potential of bidirectional embedding approach to create models that could balance both accuracy and interpretability, offering a promising perspective on optimizing classical equations and material design.

Y₂O₃ transparent ceramics are increasingly demanded in advanced technological applications, particularly in high-power laser systems, infrared optical windows, and semiconductor devices. These applications require materials that maintain both exceptional optical transmittance (i.e., >80% at 1064 nm) and mechanical strength (i.e., flexural strength >200 MPa), even when fabricated into complex geometries. Gel casting offers a promising route for producing large-scale, complex-shaped Y₂O₃ components. However, process-induced defects such as delamination, microcracks, and density gradients often compromise the microstructural integrity of green bodies, leading to a reduced performance in the ceramics. These defects primarily stem from excessive internal stresses generated during gelation, thus highlighting a need for precise control over gelation kinetics. This study was to investigate the synergistic effects of catalyst concentration and reaction temperature on the microstructural homogeneity of Y₂O₃ green bodies. The highly uniform green bodies were obtained via optimizing the parameters, thus enabling the fabrication of Y₂O₃ transparent ceramics with a high optical performance through vacuum sintering.

A certain amount of commercial Y₂O₃ powder was mixed with ethanol as a dispersion medium. The slurry was ground in a ball mill with ZrO₂ beads of 2 mm in diameter for 8 h. Ammoniumpolymethacrylate (A40) was added as a dispersant, concentrated H₂SO₄ as an additive and ZrO(NO₃)₂ as a sintering aid. The ground slurry was placed in an oven to dry at 120 ℃ for 6 h. After drying, the powder was sifted through a 200-mesh screen. The sifted powder was then calcined in air at a certain temperature for 4 h to obtain a Y₂O₃ nano-powder.

Acrylamide (AM) and N,N'-Methylenebisacrylamide (MBAM) were dissolved in deionized water to prepare a 15% AM aqueous solution in a mass ratio of AM to MBAM of 88∶10. After the organic compounds were completely dissolved, 5 mm ZrO₂ beads were added in a mass ratio of ball-to-powder of 5∶2. Tetramethylammonium Hydroxide (TMAH), ammonium citrate (TAC), A40, and Y₂O₃ powder were then added sequentially to prepare Y₂O₃ slurry with a solid content of 50%. The suspension was ground at 170 r/min for 6 h, then degassed under a vacuum of 1×10^-1Pa for 30 min. Catalyst and initiator were added sequentially, and followed via degassing the slurry again under a vacuum of 1×10^-1Pa for 3 min. Finally, the well-mixed slurry was poured into polytetrafluoroethylene or silicone molds heated at different temperatures (i.e., 25, 40, 60, and 80 ℃). The obtained green bodies were dried in air.

The gelation rate is evaluated via monitoring temperature variations during the process. The results show that increasing catalyst content accelerates gelation, but exceeding 0.08% causes a rapid reaction, leading to a green body cracking. The SEM images reveal a stratified microstructure, with a dense surface layer and a porous interior. The dense layer thickness decreases as catalyst content increases. Elevated reaction temperature also enhances gelation rate, and, stratification disappears at 60 ℃, yielding uniformly porous structures.

The infrared spectra of green bodies (i.e., 0.02% catalyst, 25 ℃) indicate an incomplete AM polymerization on the surface, while a well-developed PAM network in the interior impeded particle movement during drying. This structural disparity results in a dense surface and porous interior.

Pre-sintered green bodies exhibit heterogeneous microstructures that persist during densification. Higher catalyst content and temperature reduce the surface dense layer thickness and internal porosity.

The final vacuum-sintered samples further demonstrate that lower gelation reaction temperatures correspond to thicker surface dense layers under identical vacuum sintering temperatures, significantly hindering the expulsion of internal pores in the ceramics. This results in the center of the ceramic exhibiting an opaque condition.

Y₂O₃ transparent ceramics with excellent properties were prepared via gel casting and vacuum sintering with Y₂O₃ nano-powder as a raw material. During the gel casting process, the rate of gelation significantly affected the uniformity of the green body microstructure. A complete and uniformly structured Y₂O₃ green body was obtained via controlling the factors influencing the gelation rate at a catalyst addition of 0.04% and a reaction temperature of 60 ℃, while ensuring that the slurry met the filling requirements. After vacuum sintering at 1850 ℃ for 6 h, the obtained Y₂O₃ transparent ceramic (with a thickness of 2 mm) achieved a transmittance of 82% at 800 nm. This study demonstrated that during the gel casting process, the rate of gelation could affect the uniformity of the internal microstructure of the green body, and this internal microstructural non-uniformity further influence the subsequent densification process of the ceramic during sintering.

Refractories are important supporting materials for high-temperature industries. During high-temperature service, refractories are subjected to severe thermal shock, complex chemical corrosion, and mechanical wear, and must balance superior properties like thermal shock resistance, corrosion resistance, and high strength. However, the key service properties of refractories are often interdependent, such as superior corrosion resistance requiring a dense structure, which sacrifices the thermal shock resistance of the material. The superior thermal shock resistance requires a certain amount of pores to relieve thermal stress, but this reduces the strength and corrosion resistance of the material. Developing novel refractories with gradient composition and structure based on the different service micro-environments of refractory products in different regions, such as cold and hot surfaces, to enhance key service performance in different zones is an important research direction. In this paper, a gradient functional material with "21R-SiAlON dense layer AlN-SiC solid solution reinforced corundum porous structure" was developed based on the sensitivity of metal Al and Si to oxygen partial pressure at high temperatures.

Tabular alumina (3-1 mm, 1-0 mm; w(Al₂O₃) > 99.31%; Anmai Aluminum Co., China), α-Al₂O₃ powder (≤5 μm; w(Al₂O₃) > 99.28%), active α-Al₂O₃ powder (≤ 5 μm; w(Al₂O₃)>99.28%; Anmai Aluminum Co., China), metal aluminum powder (≤ 45 μm; w(Al)>99.77%, Henan Yuayang Co., China) and silicon powder (≤ 45 μm; w(Si)>99.52%; Yingkou Xianren Island Taihe Silicon Co., China) were used as raw materials, with phenolic resin (residual carbon of about 56%, Shengquan Group, China) as a binder. In the preparation, the weighted raw materials were mixed in a planetary mixer for 40 min to obtain uniform mixed slip. Afterwards, Al-Si-Al₂O₃ composite green brick samples (with the sizes of 230 mm × 113 mm × 65 mm) were obtained by compacting the mixed slip under 200 MPa by a model 630 t friction press. After natural dehydration for 24 h, the sample bricks were dried in a tunnel kiln at 200 ℃ for 12 h. The dried samples were nitriding sintered in a high-temperature nitriding furnace at 1550 ℃ for 3 h.

The phase composition of the sintered samples was analyzed by X-ray diffraction (XRD; Ultima IV, Rigaku Co., Japan). The microstructures of the samples were analyzed by scanning electron microscopy (SEM) in a model NOVA NANOSEM 450 electron microscope (FEI Co., USA). The pore structure of the samples was determined by a model FF35 CT microfocus industrial computered tomography (CT, YXLON International GmbH, Germany).

Based on the sensitivity of metal Al and Si to oxygen partial pressure at high temperatures, Al-Si-Al₂O₃ composites are sintered in a nitrogen atmosphere at 1550 ℃ for 3 h to prepare a gradient functional material, which is composed of "21R-SiAlON dense layer-AlN-SiC solid solution reinforced corundum with a porous structure". The synthesis mechanism is analyzed by CT, SEM, and XRD combined with thermodynamic analysis. The results indicate that P(O₂) on the surface of the sample is higher, where the"active oxidation to indirect nitridation"mechanism of Al and Si is predominated. Al and Si on the surface layer preferentially undergo active oxidation, generating gaseous sub oxides such as Al₂O and SiO, and reducing the local P(O₂). 21R-SiAlON is formed via a reaction of metal Al, Si, active α-Al₂O₃ powder and N₂. Under the action of concentration gradient, the preformed gaseous sub-oxides diffuse into the surface layer and react with nitrogen to form 21R-SiAlON, thus promoting the staggered growth of sheet-like 21R-SiAlON and ultimately forming a dense layer (with porosity<4%), which is constructive to the corrosion resistance of the material. As the active oxidation of outer Al and Si consumes O₂ layer by layer, P(O₂) inside the brick becomes extremely low, and the "direct nitriding/carbonization" reaction mechanism of Al and Si becomes dominant. Al and Si inside the brick react directly with nitrogen and residual carbon of phenolic resin, generating granular AlN-SiC solid solution reinforcement phase in-situ, forming a high-strength porous structure (with a porosity of 15%), which can alleviate a stress concentration caused by temperature gradient and improve thermal shock resistance.

A gradient functional material with a "21R-SiAlON reinforced denselayer—AlN-SiC solid solution reinforced porous structure" was prepared via nitriding Al-Si-Al₂O₃ composite in a nitrogen atmosphere at 1550 ℃ for 3 h. During sintering, there were two reaction mechanisms for metal Al and Si in different regions of the outer and inner layers of the sample, i.e., the "active oxidation to indirect nitridation" mechanism and the "direct nitridation/carbonization" mechanism in the outer and inner layers resulting in a gradient change in the composition and structure of the material. In the outer layer of the sample, the oxygen partial pressure was higher, and metal Al and Si preferentially underwent an active oxidation, generating gaseous sub oxides (i.e., Al₂O, AlO, SiO, etc.), which reduced the oxygen partial pressure. As the oxygen partial pressure decreased, Al powder, Si powder, and α-Al₂O₃ micro powder reacted with nitrogen to form 21R-SiAlON. Gaseous metastable phases such as Al₂O and SiO diffused to the outer layer of the sample to deposition, further promoting the staggered growth and development of sheet-like 21R-SiAlON, forming a dense layer. The porosity of this dense layer was less than 4%, and it was mainly composed of closed micropores. With the consumption of O₂ by the outer metal Al and Si of the sample, the oxygen partial pressure inside the sample was reduced to an extremely low level. Metal Al and Si directly reacted with N₂ and residual carbon of phenolic resin, generating AlN-SiC solid solution reinforcement phase in-situ. The porosity inside the sample was approximately 15%.

Ferroelectric thin films have drawn growing interest for their potential in electro-optic modulation, nonlinear optics, and integrated photonics, owing to their intrinsic spontaneous polarization. Among them, BaTiO₃ (BTO) stands out for its strong ferroelectricity, piezoelectricity, and nonlinear optical properties, making it a promising material for high-performance optoelectronic devices. To realize these functionalities, it is essential to achieve high crystallinity and controlled orientation in BTO films—especially along the c-axis, which is critical for polarization-related responses. While techniques such as pulsed laser deposition (PLD) and atomic layer deposition (ALD) have been used for BTO growth, they face challenges in scalability and substrate compatibility. Radio frequency (RF) magnetron sputtering offers a scalable alternative with good control over film uniformity and composition. However, obtaining high-quality epitaxial BTO films via sputtering remains challenging due to the sensitivity of the process to parameters like substrate temperature, gas composition, and RF power. This work systematically investigates the effects of key sputtering parameters on the structural and optical properties of c-axis-oriented BTO thin films. The relationship between deposition conditions, domain structure, and optical performance is further explored using second harmonic generation (SHG), aiming to guide the fabrication of high-quality ferroelectric films for integrated photonic applications.

Epitaxial BaTiO₃ (BTO) thin films were deposited on (001) (La,Sr)(Al,Ta)O₃ (LSAT) and (110) GdScO₃(GSO)single-crystal substrates using RF magnetron sputtering with a 2 in ceramic BTO target. The chamber pressure was maintained at 1.5 Pa, with either pure Ar or Ar/O₂ gas mixtures as the sputtering atmosphere. Substrate temperatures ranged from 25 ℃ to 750 ℃, and RF power was set at 50 W or 75 W (2.47 W/cm² and 3.70 W/cm², respectively). A 10 min pre-sputtering step was performed before each run to stabilize film composition. Structural characterization was conducted using an X-ray diffractometer (SmartLab, Rigaku) with a Cu-Kα₁ source and Ge (220) monochromator. Measurements included θ-2θ scans, rocking curves, X-ray reflectivity (XRR), and reciprocal space mapping (RSM). Surface morphology and roughness were analyzed via atomic force microscopy (AFM, tapping mode), while domain structures were evaluated using second harmonic generation (SHG) with a Ti:sapphire femtosecond laser (800 nm, 35 fs). SHG measurements were performed in reflection geometry at a 45° incidence angle. Film composition was assessed using a Zeiss GeminiSEM 500 with a windowless EDS detector at 20 kV to determine the Ba/Ti ratio. Optical constants, including refractive index (n₀) and extinction coefficient (k₀), were measured by spectroscopic ellipsometry (UVISEL plus, Horiba) and fitted using the Lorentz model. Ellipsometric thickness values were validated by XRR.

The deposition temperature plays a critical role in determining the crystallinity, strain state, morphology, and polarization of BaTiO₃ (BTO) thin films grown on LSAT and GSO substrates. High-resolution X-ray diffraction (HRXRD) results show enhanced c-axis orientation and crystallinity with increasing temperature, peaking at 700 ℃ on LSAT. A further rise to 750 ℃ slightly reduces quality, likely due to defect formation. On GSO, improved Laue oscillations and narrower FWHM at 750 ℃ indicate better lattice matching and epitaxial growth. Scherrer-based estimates reveal that vertical coherence length peaks at 700 ℃ (about 32 nm) on LSAT and increases steadily on GSO, reaching about 60 nm at 750 ℃. This contrast reflects superior lattice compatibility between GSO and BTO. Reciprocal space mapping shows strain evolution with temperature. At 500 ℃, films exhibit strong in-plane tensile strain (c/a ratio < 1), which relaxes at higher temperatures as c/a exceeds 1. Calculated strain confirms this, with in-plane strain decreasing and out-of-plane strain increasing from 500 ℃ to 750 ℃. SHG measurements reveal that low-temperature films (500 ℃) favor in-plane polarization, while higher temperatures induce out-of-plane domains and complex multi-domain structures, indicating temperature-driven polarization reorientation. AFM results show the smoothest surface at 600 ℃ (RMS is 1.175 nm), with roughness slightly increasing at higher temperatures due to strain relaxation and defect formation. These findings align with XRD and XRR trends. Ellipsometry and XRR confirm that film thickness decreases from about 80 nm at 500 ℃ to about 50 nm at 600-650 ℃ due to enhanced lateral growth, then slightly increases at higher temperatures. Clearer XRR fringes at 700 ℃ indicate improved interface quality. Deposition optimization identified the best conditions as 30° angle, pure Ar atmosphere, 13.361 cm target-substrate distance, and 75 W RF power, achieving uniform and high-quality films. Finally, SEM and EDS analyses show denser, smoother films at elevated temperatures. However, Ba/Ti ratios deviated from stoichiometry (0.66-0.97), likely due to off-axis sputtering effects, contributing to strain and preferential c-axis domain formation.

Epitaxial BaTiO₃ (BTO) thin films were successfully deposited on (001)-oriented LSAT and (110)-oriented GSO substrates via radio-frequency (RF) magnetron sputtering. The structural, morphological, compositional, and optical properties of the films were systematically investigated. X-ray diffraction (XRD) analysis confirmed that the films predominantly crystallized in the tetragonal phase with a strong (001) preferred orientation, indicating high-quality epitaxial growth. Particularly, the film deposited on the GSO substrate at 750 ℃ exhibited superior crystallinity, as evidenced by the appearance of distinct Laue oscillations. Deposition parameters such as target-to-substrate distance, deposition angle, O₂/Ar gas volume flow ratio, and RF power were found to significantly influence the film's structure and performance. Optimal results were achieved using a target-to-substrate distance of 13.361 cm, a deposition angle of 30°, and an RF power of 75 W, with pure Ar atmosphere yielding the best film quality and highest deposition rate. The synergistic optimization of these parameters is essential for obtaining high-crystalline-quality BTO thin films and provides a solid foundation for their application in optoelectronic and ferroelectric devices.

It is necessary for an ideal bioceramic scaffold to have a suitable structure. The structure can affect the mechanical properties of the scaffold (i.e., elastic modulus and compressive strength) and the biological properties of the scaffold (i.e., degradability and cell growth rate). Lattice structure is a kind of periodic porous structure, which has some advantages of light weight and high strength, and is widely used in the preparation of bioceramic scaffolders. For the structure of the scaffold, high porosity and large pore size are important for bone growth, bone integration and promoting good mechanical interlocking between neighboring bones and the scaffold. However, scaffolds with a high porosity often lack mechanical strength. In addition, different parts of the bone have different structural requirements. In this paper, scaffolds with a non-uniform structure or a hierarchical structure were designed, with loose and porous exterior to facilitate cell adhesion, osteogenic differentiation and vascularization as well as relatively dense interior to provide sufficient mechanical support for bone repair.

In this work, composite ceramics scaffolds with 10% akermanite content were prepared by DLP technology. The scaffold had a high porosity outside to promote the growth of bone tissue, and a low porosity inside to withstand external forces. The compressive strength, fracture form, in-vitro degradation performance and bioactivity of graded bioceramic scaffolds were investigated. The models of scaffolds were imported into the DLP printer with a 405 nm light. The samples were printed with the intensity of 8 mJ/cm² and a layer thickness of 50 µm. Finally, the ceramic samples were sintered at 1100 ℃. The degradability of the hierarchical gyroid bioceramic scaffolds was evaluated through immersion in Tris-HCl solution and SBF solution at a ratio of 200 mL/g. The bioactivity of bioceramic was obtained via immersing them in SBF solution for two weeks. The concentrations of calcium, phosphate, silicon, and magnesium ions in the soaking solution were determined by an inductively coupled plasma optical emission spectrometer.

In this work, a hierarchical Gyroid structure HA-AK10 scaffold (sintered at 1100 ℃) with a radial internal porosity of 50% and an external porosity of 70% is prepared, and the influence of structural form on the compressive strength and degradation performance of the scaffold is investigated. The biological activity of the bioceramics in vitro is also verified. The mechanical simulation results show that the stress distribution corresponds to the porosity distribution of the structure, and the low porosity is larger and the overall stress concentration phenomenon does not appear. After soaking in SBF solution, Si—OH is firstly formed on the surface of bioceramics, and then silicon gel layer is produced due to the presence of calcium and silicon ions. The silicon gel layer is dissociated into negatively charged groups under alkaline environment secondary adsorption of calcium ions and phosphate ions, forming amorphous calcium phosphate, and finally amorphous calcium phosphate crystals and adsorption of carbonate ions, forming carbonate hydroxyapatite. This indicates that the composite bioceramics have a good biological activity in-vitro and can provide a good environment for the growth of bone cells. A hierarchical Gyroid ceramic scaffold with a bone geometry is prepared via applying the hierarchical structure to the bone contour scaffold. The maximum load capacity of the hierarchical Gyroid ceramic scaffold is 8 times that of the uniform structure.

The hierarchical structure scaffold designed had good overall compressive performance, good degradation performance, and still maintained a good mechanical stability during degradation. In addition, in-vitro biological experimental results showed that the surface graded composite scaffold could have a good in-vitro biological activity and provide a good environment for bone cells. Compared to the heterosexual structure, the graded scaffold had greater mechanical properties.

As electronic technology and integrated circuits advance rapidly, the functional demands of devices are increasingly elevated. Ferroelectric/semiconductor heterostructures are significant in applications including memory, sensing, and optoelectronic devices because they combine the best qualities of both ferroelectric and semiconductor materials. In recent years, the variety and refinement of the preparation process have led to the successful direct integration of ferroelectric materials with semiconductor silicon. Nevertheless, constructing ferroelectric/semiconductor heterostructures devoid of any interface layers, particularly on silicon substrates, is exceedingly challenging. Due to thermal diffusion, there is usually a SiO_x layer at the interface, which subsequently affects device performance. However, systematic researches are urgently need regarding the effect of the interface layer on the potential barriers, ferroelectric polarization, and carrier transport. This work develops SiO_x layers of varying thicknesses and densities on the n-Si surface, followed by the fabrication of bismuth ferrite (BiFeO₃) films on the pretreated substrate. When the substrate pretreatment temperature rises, the SiO_x layer progressively thickens, thereby altering the interface barrier, polarization switching, and the transport of photogenerated carriers. This study presents a novel concept for the creation of ferroelectric/semiconductor heterostructures featuring several interface contact types and electrical transport pathways.

Oxygen was introduced into the tube furnace, which was later heated to 400-1000 ℃. Once the temperature stabilizes, the (100) oriented n-Si substrate (resistivity of approximately 10 Ω·cm) is put into the furnace. After heating for 1 h, the substrate is directly removed from the tube furnace and allowed to cool in a room temperature environment.

The raw materials Bi(NO₃)₃·5H₂O and Fe(NO₃)₃·9H₂O were dissolved in acetic acid and ethylene glycol methyl ether, respectively. Subsequently, these two solutions were mixed, stirred for 8 h, and filtered to obtain a BiFeO₃ precursor solution at a concentration of 0.1 mol/L. The precursors were spin-coated onto the pretreated n-Si (100) substrate at 3500 r/min for 30 s and heated at 180 ℃ for 5 min. The spin-coating process was done three times to attain a film thickness of approximately 60 nm, afterwards, the samples were annealed in a nitrogen environment at 380 ℃ for 15 min, followed by 550 ℃ for 50 min, with a heating rate of 10 ℃/min.

The n-Si substrate was pretreated at various temperatures in an oxygen environment. The cross-sectional high-resolution transmission electron microscopy indicates an increase in the thickness of the SiO_x layer with increasing substrate pretreatment temperature. The dielectric measurements show that when the pretreatment temperature is above 600 ℃, the activation energy of the dielectric relaxation begins to decline, signifying a decrease in the oxygen vacancy content while the transition of the oxygen vacancies from divalent to monovalent. Subsequently, BiFeO₃ films were fabricated on the pretreated substrate. X-ray diffraction studies demonstrated that all the BiFeO₃ films exhibit R3c polycrystalline structure.

After substrate pretreatment, the clamping phenomenon of the BiFeO₃/n-Si hysteresis loop disappears. As the pretreatment temperature increases, the loop becomes slimmer, and the coercive voltage decreases. The reason is that the increased thickness of the SiO_x layer hinders the carrier migration between BiFeO₃ and the n-Si substrate. At temperatures below and above 700 ℃, the SiO_x can be considered as a tunneling layer and a resistive layer, respectively. I-V curves show that the BiFeO₃/n-Si samples still exhibit rectification effects, but the cut-off voltage under negative bias and the conduction current under positive bias both decrease, which is consistent with the weakening of the interface barrier and the decrease in conductivity. Although the photocurrent and on-off ratio generally decline with the increasing pretreatment temperature, the on-off ratio of the sample on 700 ℃ pretreated substrate increases abnormally, attributed to the increased conductivity associated with the aggregation of monovalent oxygen vacancies.

BiFeO₃ films are grown on n-Si substrates pretreated at different temperatures. As the pretreatment temperature increases, the SiO_x layer on the n-Si surface became thicker and denser, accompanied by a reduction in oxygen vacancies and a transition from divalent to monovalent. The hysteresis loops are no longer clamped, with the coercive voltage deceased, and both the cut-off voltage of the I-V curves and the on-off ratio of the photocurrent reduce. The primary explanation is that the SiO_x layer reduces the pn junction barrier and the built-in electric field at the BiFeO₃/n-Si interface, facilitating the polarization switching of BiFeO₃ and the transport of photogenerated carriers. The accumulation of oxygen vacancies at a particular temperature can result in an anomalous rise in photocurrent.

Synthesis of organic hafnium polymers gradually tends to be non-oxidation, simplification, low cost, high conversion rate, and high performance. The pyrolysis of polymers containing Hf-O bonds needs to undergo the carbon-thermal reduction process at high temperatures, and the prepared ceramics have more pores and cracks and insufficient performance, so non-oxygen hafnium-containing polymers are an important direction for future research. The molding performance of solid precursors limits their application in preparing ultra-high temperature ceramic composites via the PIP method, and liquid precursors with a high ceramic yield becomes a hot direction for future development. In addition, polymer-derived continuous ultra-high temperature ceramic fibers and their composites is a research hotspot, and exploring a new paradigm of artificial intelligence to accelerate the research of ultra-high temperature ceramic materials is also an important direction for development.

Ammonia is a toxic and harmful gas that affects the environment and human health. It is thus of great significance to identify and detect ammonia and its concentration rapidly and accurately for human health monitoring and ecological environment management. TiO₂ is widely used in the field of gas sensors due to its advantages of good stability, environmental tolerance, non-pollution, and outstanding contact reaction properties. However, it is gradually found that it has the disadvantages of long response/recovery time and low response value. MXene has a great potential in the field of gas sensing because of its large specific surface area and superior electron mobility rate, but its response value is rather low. In this work, TiO₂/Ti₃C₂ composites were prepared by an one-step hydrothermal method. The synergistic effect of semiconductor properties of TiO₂ and excellent electron transport performance of Ti₃C₂ was analyzed.

TiO₂/Ti₃C₂ composites at different hydrothermal temperatures were prepared by a hydrothermal method with MXene-Ti₃C₂ and butyl titanate as raw materials. The physical phase, surface morphology, specific surface area and pore size distribution, and structure of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurement based on BET, and Raman spectroscopy. In addition, the ammonia sensing properties of TiO₂/Ti₃C₂ composites at room temperature were also analyzed.

TiO₂/Ti₃C₂ composites can be prepared by a hydrothermal method. The XRD patterns indicate that the characteristic peaks of Ti₃C₂ and the diffraction peaks of anatase TiO₂ both appear in the composites. The Raman spectra show the generation of anatase TiO₂. The SEM images indicate that TiO₂ nanoparticles are uniformly loaded on the interlayer and surface of Ti₃C₂. The agglomeration of TiO₂ particles becomes more severe with the increase of hydrothermal temperature. The N₂ adsorption-desorption experiment shows that the specific surface area of prepared TiO₂/Ti₃C₂ is much larger than that of Ti₃C₂. Moreover, the specific surface area of TiO₂/Ti₃C₂-150 is the largest, but it gradually decreases with the increase of hydrothermal temperature possibly due to the agglomeration of the generated TiO₂ particles. The gas sensing test results show that TiO₂/Ti₃C₂ composites and pure TiO₂ have responses to 100 μL/L ammonia at room temperature, while Ti₃C₂ has little response. The response values of TiO₂/Ti₃C₂ composites are significantly better than that of pure TiO₂ obtained at the same temperature. Among all the samples, TiO₂/Ti₃C₂-150 has the maximum response value (i.e., 8.37). Also, the response value of the composites increases with the increase of ammonia concentration, showing a high linear correlation. After the stability test for one month, the response value of TiO₂/Ti₃C₂-150 to 100 μL/L ammonia is only decreased by 14.1%, indicating a long-term stability. Compared to TiO₂-150, the response time of TiO₂/Ti₃C₂-150 decreases from 43 s to 28 s, and the recovery time reduces from 49 s to 37 s, manifesting a high selectivity to ammonia. The stable gas absorption/desorption reaction of TiO₂ and thesuperior electron transport rate of Ti₃C₂ can enhance the response of TiO₂/Ti₃C₂ to ammonia.

The nanoparticles of anatase TiO₂ were supported on the interlayer and surface of Ti₃C₂ by a hydrothermal method. At the hydrothermal temperature of 150 ℃, TiO₂ particles were supported evenly and agglomerated weakly, with a greater specific surface area and smaller particle size. Compared to pure TiO₂ and Ti₃C₂, TiO₂/Ti₃C₂-150 had a good response to ammonia at room temperature. At an ammonia concentration of 300 μL/L, the gas sensing response value of TiO₂/Ti₃C₂-150 was 34.77, which was greater than that of pure TiO₂. In addition, TiO₂/Ti₃C₂-150 also showed a rapid response recovery rate, a good selectivity and a long-term response stability, having a promising application prospect in the field of rapid detection of ammonia at room temperature.