With the rapid development of wireless communication and information technology, the electromagnetic wave generated by electronic equipment and communication facilities will cause serious damage to human health and living environment. Electromagnetic wave absorbing materials can convert electromagnetic waves into heat or other forms of energy, which plays an important role in reducing electromagnetic wave pollution. Electromagnetic wave absorbing materials have attracted recent attention. Common electromagnetic wave absorbing materials include magnetic materials and dielectric materials, such as ferrite, magnetic metals, carbon materials (i.e., carbon nanotubes, graphite carbon, etc.), oxide ceramics (i.e., zinc oxide, tin oxide, etc.) and silicon carbide, etc.. However, these materials are prone to oxidization and impedance mismatch at high temperatures. It is thus important to develop new dielectric materials with intense electromagnetic loss characteristics at high temperatures. Polymer-derived silicon boron carbon nitrogen (SiBCN) ceramics have superior corrosion resistance and high-temperature oxidation resistance, as one of electromagnetic wave absorbing materials that can be applied in harsh environments. However, pure phase SiBCN ceramics have the poor absorption of electromagnetic waves due to their low dielectric constant and low conductivity.

At present, in-situ generation or addition of high electromagnetic loss phases are often used to improve the absorption ability of SiBCN ceramics for electromagnetic waves. In this paper, SiZrBCN composite ceramics were prepared via introducing Zr into a polymer-derived SiBCN ceramic precursor. The evolution of the physical phase composition and microstructure of SiZrBCN composite ceramics by Zr addition was investigated, and the effect of physical phase compositions on the electromagnetic wave absorption performance of SiZrBCN ceramics was discussed.

Under the condition of ice bath, THF (280 mmol), DCMVS (150 mmol) and (CH₃)₂S·BH₃ (250 mmol) were injected into a three-necked round-bottomed flask and stirred thoroughly for 24 h to obtain an intermediate dichloromethylmethylsilyl ethylborane (TDSB). DCMS (180 mmol) and HMDZ (450 mmol) were sequentially added to TDSB. DCMS (180 mmol) and HMDZ (450 mmol) were added sequentially to TDSB and stirred for 24 h. Subsequently, the material in a three-necked flask was heated at 110 ℃ for 4 h, and then slowly heated at 170 ℃ for 4 h to obtain a clear liquid. The above products were distilled at a reduced pressure for three times to obtain PBSZ, and ZrCl₄ (12.5 mmol) was added into PBSZ and heated at 80 ℃ for 12 h and distilled at a reduced pressure to obtain a beige precursor named as sample Z5. The above experiments were repeated to prepare samples Z0, Z5, and Z10, respectively, and the experiments were carried out in Ar atmosphere throughout the whole process. The resulting samples Z0, Z5 and Z10 were heated at a heating rate of 2 ℃ at 280 ℃ for curing, and then the cured samples were heated in N₂ atmosphere at 1 600 ℃ to obtain samples Z0-1600, Z5-1600 and Z10-1600.

The chemical bonding and group compositions of SiBCN ceramic precursors were investigated by a model VERTEX 70 Fourier infrared spectrometer. The physical phase composition of SiBCN ceramics was investigated by a model X'Pert MPD Pro X-ray diffractometer under the following conditions (i.e., Cu as an anodic target, K_α-rays as a radiation source, voltage and current of 40 kV and 40 mA, respectively, and scanning range (2θ) of 10° to 90°. The chemical bonding composition of SiBCN ceramics was analyzed by a model ESCALAB250XI X-ray electron spectrometer. The microstructure of SiBCN ceramics was determined by a model Apreo S HiVac scanning electron microscope with a model TalosF200X transmission electron microscope. The electromagnetic parameters of the ceramics were examined by a model E5071C vector network analyzer.

ZrCl₄ reacts with the Si—H bond/N—H bond of PBSZ, and atom Zr replaces atom H to generate Si—Zr and N—Zr bonds. The addition of Zr inhibits the formation of SiC nanocrystals inside the ceramics, increases the generation of Si₃N₄ inside the ceramics, and increases the size of graphitic carbon inside the ceramics from 1.50 nm to 1.77 nm and 1.82 nm. SiZrBCN ceramics with Zr addition of 5% have the superior electromagnetic wave absorption performance, and the RL_min of SiZrBCN ceramics reach -21.8 dB at 7.8 GHz when the thickness is 2.5 mm.

1) During the precursor synthesis, ZrCl₄ reacted with Si—H bond/N—H bond of PBSZ, and Zr replaced H atoms to generate Si—Zr and N-Zr bonds, which grafted Zr onto the active sites of PBSZ.

2) After the ceramic precursor was heat-treated at 1 600 ℃, the crystals of Zr₂CN, SiC, Si₃N₄ and graphitic carbon were generated in-situ inside the ceramic, in which the addition of Zr suppressed the formation of SiC nanocrystals, increased the generation of Si₃N₄ inside the ceramic, and improved the impedance matching of the substrate. The presence of Zr promoted the generation of graphitic carbon inside the ceramic, and caused the in-plane crystallization of the graphitic carbon size increasing from 1.50 nm to 1.77 nm and 1.82 nm.

3) SiZrBCN ceramics with 5% Zr addition had the optimum electromagnetic wave absorption performance due to the large number of dielectric crystals generated inside the ceramics and the good impedance matching performance. The RL_min of the SiZrBCN ceramics reached -21.8 dB at 7.8 GHz when the thickness was 2.5 mm. The generation of a variety of dielectric crystals could improve the absorption performance of the material. The crystals could improve the electromagnetic wave absorption ability of the material, indicating that SiZrBCN ceramics could be used as an effective candidate in the field of wave-absorbing materials.

Lead zirconate titanate (PZT) piezoelectric ceramics are widely used in electronic components. With the continuous development of intelligent, integrated and lightweight piezoelectric devices, the shape and structure of piezoelectric ceramic components become more complex. 3D printing technology has potential advantages in the personalized manufacturing of complex ceramic parts, especially the fused deposition modeling (FDM) method, which has the advantages of high efficiency, low cost, and wide material adaptability. This paper was to prepare PZT piezoelectric ceramics by FDM. In addition, the process optimization, printing performance, sintering behavior, and electrical properties were also investigated.

A PZT powder with an average particle size of 2.85 μm was used. An organic binder was composed of 58% paraffin wax (PW, purity: 99% in mass fraction, the same below), 5% stearic acid (SA, 98%), 20% Polyethylene (PE, 99%), and 17% ethylene-vinyl acetate copolymer (EVA, 98%). The ceramic powder and organic binder were thoroughly mixed by a double-roller mixing machine at 130 ℃ for 60 min, and then crushed into granules of less than 5 mm. The solid loading of the feedstock was set to 83%, 85%, 87%, and 89%. A commercial extrusion printer (UP-R200, Shenzhen Uprise 3D Technology Co., Ltd., China) with the extrusion nozzle diameter of 0.5 mm, and the layer thickness of 0.2 mm for FDM was used in this study. The printing condition was printing temperature of 120 ℃, print speed of 40 mm/s, and printing platform temperature of 85 ℃. Some complex shaped parts like ring array, rectangular array, and thin-walled cylindrical structures were printed. The printed green bodies were firstly placed in kerosene for solvent debinding at 40 ℃ for 20 h and then dried in an oven at 40 ℃ for 15 h. The dried parts were heated at 600 ℃ for 2 h. After thermal debinding, the samples were put into a crucible with a lid, buried on PZT powder, and sintered in the furnace at 1 100 ℃ for 2 h. The PZT ceramics coated with silver electrodes were polarized in an electric field of 2.5 kV/mm in silicone oil at 120 ℃ for 20 min. The phase composition and structure of the sample were determined by a model D8 Advance X-ray diffractometer (XRD, Germany) with detect angles ranging from 10° to 80°. The rheological properties of the printing consumables were tested at 180 ℃ by a model Rosand RH2000 capillary rheometer (Malvern Co., UK). The microstructures of samples were analyzed by a model JSM-6700F field emission scanning electron microscope (SEM, JEOL Co., Japan). The density of the samples was measured by a drainage method. The dielectric constant ε_r and dielectric loss δ were measured by a model Agilent-4294A impedance analyzer (USA). The ferroelectric properties were analyzed by a model aix ACCT-TF Analyzer 2000 ferroelectric tester (Germany). The piezoelectric constant of the polarized sample was measured by a model ZJ-3AN quasi-static d₃₃ meter (Institute of Acoustics, Chinese Academy of Sciences, China).

At a constant solid loading, the shear viscosity of the feedstock at 180 ℃ decreases with the increase of shear rate, and has obvious shear thinning characteristics, which is beneficial to the extrusion process. At a constant shear rate, the higher the solid loading is, the higher the measured shear viscosity will be. At a shear rate of 100 s^-1, the shear viscosity is 30.30, 45.07, 47.08 Pa·s and 655.21 Pa·s respectively as the solid loading increases. Annular arrays with a wall thickness of 1 mm, rectangular arrays with an element spacing of 0.25 mm, and annular thin-wall blank samples with an inclination angle of 30° are printed, indicating that the prepared feedstock has a good printing performance. The SEM images show that the prepared PZT ceramic samples have a good interlayer bonding. Each layer is straight, uniform and continuous. After debinding and sintering, the interior of the material is uniform and dense without obvious pore defects, which shows that PZT ceramics with a good interlayer bonding can be obtained by the FDM method. The density of both green body and sintered body increases with the increase of solid loading, and the density of sintered body increases from 7.55 g/cm³ to 7.84 g/cm³. The results show that the sintering shrinkage in the Z direction is higher than that in the X-Y direction. The SEM images of PZT samples at each stage show that the two-step debinding process of solvent debinding + thermal debinding is beneficial to eliminating organic binders without causing defects. PZT piezoelectric ceramic sheets with a diameter of 17.5 mm and a thickness of 1.35 mm are prepared using a feedstock with a solid loading of 87%. The electrical property analysis indicates that the Curie temperature reaches 295℃, the coercive electric field E is 7.57 kV/cm, the remnant polarization P_r reaches 3.66 μC/cm², and the piezoelectric constant d₃₃ reaches 316 pC/N.

The prepared feedstock with a high solid content and a low viscosity exhibited a typical shear thinning rheology and an excellent printing performance. A PZT spherical shell structure without support was prepared. The PZT ceramic samples had good interlayer bonding and no interlayer cracks. The density of PZT ceramics increased with increasing the solid loading. At a solid loading of 87%, the density of PZT ceramic reached 7.82 g/cm³, and the piezoelectric constant d₃₃ was 316 pC/N. This study provided an effective approach for the preparation of complex structure PZT piezoelectric ceramics.

La_1-xSr_xCr_0.5Mn_0.5O₃ (LSCM) perovskite as a SOC fuel electrode material has attracted much attention due to its excellent comprehensive performance. However, there is still a lack of systematic and in-depth research on the its structural stability that is affected by some factors such as Sr content, temperature, and atmosphere under operating conditions of SOC. In particular, previous work indicate that this material exhibits different electrode performances and crystal structures under Sr-free and Sr-containing conditions, having the Sr content impact on its structural stability and electrochemical performance. Therefore, this paper was to analyze the crystal structures of La_1-xSr_xCr_0.5Mn_0.5O₃ heat-treated in a reducing atmosphere at elevated temperatures from 500 ℃ to 1 000 ℃. In addition, the mechanism of crystal structural transformation of LSCM in a high-temperature reducing atmosphere was also discussed.

The LSCM precursors with different Sr contents (i.e., x of 0, 0.1, 0.2, and 0.3) were prepared by a citric acid sol-gel method. The precursors were calcined into LSCM powders in a muffle furnace at 1100 ℃. The LSCM powders were then thermally reduced in a reducing atmosphere at 500 ℃-1 000 ℃. After reduction, the phase transformations of each sample were characterized by X-ray diffraction (XRD). The lattice constants of the samples were calculated based on the Rietveld method using a software named Rietica. In addition, the first-principles calculations, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were also performed to reveal the effects of Sr content and reduction heat treatment on the crystal transformation of LSCM.

The samples with different Sr contents were calcined in air at 1 100 ℃. A single trigonal phase appears when the Sr contents x≤0.2, while a small amount of SrCrO₄ phase occurs besides the perovskite phase when x=0.3. After reduction at elevated temperatures, the sample with x of 0 transforms from a trigonal phase to an orthorhombic phase, and its crystal structure is relatively stable according to the fact that there are no other phases formed with increasing the reduction temperature. The XRD patterns of LCM samples reduced at different temperatures are analyzed using the Rietveld method. The results show that the unit cell volume of the reduced perovskite samples increases with the increase of heat treatment temperature from 700 ℃ to 1 000 ℃. However, the unit cell volume of the sample reduced at 600 ℃ is smaller than that at 500 ℃. This is because the sample begin to lose a considerable amount of oxygen at 500-600 ℃ during the reduction heat treatment, leading to a significant change in the shape of the crystal unit cell. For the samples with x of 0.1 and 0.2, trigonal and orthorhombic phases co-exist, and the proportion of trigonal phase increases with increasing x value but decreases with increasing reduction temperature. A layered perovskite oxide phase of (La,Sr)₂MnO₄ appears in the sample with x of 0.2 when the reduction temperature increases to 900 ℃, indicating that this sample has a poorer structural stability, compared with the sample with x of 0.1. According to the XPS results, compared with the LCM without Sr, the Mn³⁺ concentration in the reduced LSCM is relatively low as the Sr content increases, which can alleviate the Jahn-Teller distortion. Therefore, LSCM tends to form a trigonal phase, while LCM undergoes a more significant Jahn-Teller distortion, making it tends to transform into a more stable structure of orthorhombic phase than trigonal phase. The FTIR spectra reveal that the Mn/Cr—O bond energy increases in the LSCM perovskite with the increase of Sr content. The lattice parameters of each sample are calculated using the Rietveld method based on the XRD data, and subsequently the lengths of Mn/Cr-O bonds of each crystal are calculated. The results demonstrate that the length of Mn/Cr—O bond in the crystals decreases with the increase of Sr content, which is consistent with the conclusion derived from the FTIR spectra. However, the first-principles calculations confirm that the binding energy of the crystal of LSCM gradually increases with the increase of Sr content. Therefore, in summary, the existence of trigonal phase and the increase of binding energy caused by Sr doping jointly lead to the fact that the structural stability of Sr-containing LSCM perovskite is lower than that of Sr-free LCM under high-temperature reduction atmosphere conditions.

The structural transformation process and regularity of the LSCM perovskites under high-temperature reducing atmosphere were mainly controlled by the Jahn-Teller distortion, which depended on the concentration of Mn³⁺. The LCM without Sr underwent a more significant Jahn-Teller distortion, making it form an orthorhombic phase. The increase of Sr content mitigated the Jahn-Teller distortion, making the Sr-containing LSCM perovskites more likely to form a trigonal phase as well as possess an increased binding energy, thus reducing the structural stability of LSCM.

The rapid development of radar and radio communication technology plays a critical role in enhancing the competitiveness of national defense, while subsequent electromagnetic interference seriously threatens the stealth and information security of military equipment. Consequently, electromagnetic wave absorption (EWA) materials that can eliminate or reduce electromagnetic waves by converting electromagnetic energy into thermal energy or other energy through their own electromagnetic loss mechanism have attracted much attention. Nevertheless, the development of EWA materials is still a challenge to simultaneously satisfy efficient microwave absorption and excellent anticorrosive performance in the case of the complex and changeable marine military environment. Reduced graphene oxide (rGO) with a unique sheet structure, a great chemical stability and a high electrical conductivity can extend the diffusion path of corrosive media and provide conductive loss, which is an excellent candidate for anticorrosion and wave absorption material. To improve the environmental adaptability of EWA materials for practical applications, constructing nanocomposites via combining rGO and MOFs derivatives is an effective strategy to achieve significant EWA and anticorrosion properties. In this paper, metal nanoparticle uniformly loaded carbon skeleton-rGO composites were prepared with MOFs as precursors to improve the impedance matching and EWA performance via utilizing the synergistic effect of magnetic nanoparticles and dielectric rGO. In addition, a theoretical and experimental reference for the development of new multifunctional materials with a high-efficiency electromagnetic wave absorption and an anticorrosion performance was also provided.

For the preparation of Ni/Zn/NC@rGO nanocomposites, graphene oxide (GO) was prepared by a modified Hummer method. Also, white ZIF-8 precursor powder was obtained via dissolving zinc nitrate in 2-methylimidazole solution in methanol system. Meanwhile, nickel nitrate was dissolved into ZIF-8 precursor powder, and GO with different mass ratios of nickel nitrate was added. Finally, the obtained powder was treated at a high temperature to obtain Ni/Zn/NC@rGO nanocomposites. The composition of Ni/Zn/NC@rGO nanocomposites was determined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The magnetic properties of the composites were measured via hysteresis curves. The microstructures of the nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electromagnetic parameters of Ni/Zn/NC@rGO nanocomposites were examined by a vector network analyzer. The dynamic potential polarization of bare carbon steel, carbon steel coated with pure epoxy resin coating, carbon steel coated with 3% (in mass fraction) doped Ni/Zn/NC epoxy resin (Ni/Zn/NC/EP), and carbon steel coated with 3% doped Ni/Zn/NC@rGO epoxy resin (Ni/Zn/NC@rGO/EP) were analyzed by an electrochemical workstation for three times to ensure the accuracy of the results.

The XRD patterns of Ni/Zn/NC and Ni/Zn/NC@rGO nanocomposites show a crystalline facet C(002) of rGO as well as crystalline facets (111), (200) and (220) of Ni metal, indicating that Ni²⁺ is reduced to magnetic Ni monomers at a high temperature. The XPS spectra show that the Ni/Zn/NC@rGO nanocomposites consist of elements C, N, Ni, O and Zn. Ni/Zn/NC@rGO-1∶1 nanocomposite has the maximum degree of graphitization and more structural integrity, possibly due to the promotion of wave absorption and anticorrosion properties. Besides, the SEM and TEM images of Ni/Zn/NC@rGO nanocomposites reveal that the nanocomposites have a large number of pore structures, which allow electromagnetic waves to be dissipated through multiple reflection and scattering. Furthermore, Ni nanoparticles are uniformly dispersed on rGO nanosheets, and the multiple interfaces formed lead to the polarization relaxation phenomenon, which is beneficial for the attenuation of electromagnetic waves through polarization loss.

Ni/Zn/NC@rGO-1∶1 nanocomposite has the maximum electromagnetic wave storage and attenuation capabilities, which can be attributed to that the interface polarization induced by the rGO multilayer structure and the uniformly dispersed Ni nanoparticles and the rGO sheets, as well as the dipole polarization originated from the defects created by N atoms doping during the pyrolysis process. Moreover, the imaginary part of the complex permittivity of Ni/Zn/NC@rGO-1∶1 shows slight fluctuations, indicating that the existence of multiple polarization relaxation processes, which is also confirmed by the Cole-Cole semicircle plots. As a result, Ni/Zn/NC@rGO-1∶1 exhibits the optimum EMA performance. The minimum reflection loss value (RL_min) is -63.70 dB with a matching thickness of 1.67 mm, and the effective absorption bandwidth (RL<-10 dB) reaches 5.36 GHz at the thickness of 1.63 mm. The synergistic benefits of magnetic nanoparticles and dielectric rGO optimize the impedance matching characteristics of Ni/Zn/NC@rGO-1∶1 sample, while the porous structure and abundant interface polarization effectively improve the attenuation constant of the sample.

Compared with carbon steel of other coating samples, Ni/Zn/NC@rGO/EP coating sample possesses a higher corrosion potential and a lower corrosion current, thus showing the most excellent anticorrosion performance. Ni/Zn/NC@rGO nanoparticles fill the micropores of the epoxy resin, which can effectively inhibit the infiltration of corrosive ions. In addition, the unique sheet structure of graphene is also easy to stack and thereby extend the diffusion pathway of corrosive media to achieve the purpose of improving the anticorrosion performance.

Ni/Zn/NC@rGO nanocomposites derived from MOF were synthetized via co-precipitation and pyrolysis processes., The outstanding impedance matching and microwave attenuation ability was realized via adjusting the mass ratios between the Ni source and GO. At a mass ratio of 1∶1, the effective absorption bandwidth and the RL_min values were 5.36 GHz and -63.70 dB with the thicknesses of 1.63 mm and 1.67 mm, respectively, which could be attributed to that the porous structure provide transmission paths for multiple reflections and scattering of electromagnetic waves, as well as multiple interfaces bring more polarization loss. In particular, the graphene layer structure also extended the diffusion path of the corrosive medium, resulting in a higher corrosion potential and a lower corrosion current in Ni/Zn/NC@rGO-doped nanocomposite coatings. This study provides a reference for the development of efficient anticorrosion and EWA materials, which could have a promising application in the field of marine environment.

The solubility of Mo in borosilicate glasses is relatively low. Therefore, molybdate is easy to separate from glass, forming Mo-yellow phase (alkali molybdates, such as Na₂MoO₄, CsLiMoO₄, and Li₂MoO₄) or CaMoO₄ crystals. The crystal CaMoO₄ performs a superior water resistance ability, which can effectively reduce the Mo leaching rate of a high Mo content and high level waste (HLW) solidification glass. On the contrary, alkali-Mo-yellow phase is highly water-soluble, leading to a serious Mo-leaching, and thus decreases the chemical durability of the products. The duration of the chemical durability test of solidification glass is 7 or 28 days, thus retarding the whole cycle for the investigation of HLW solidification glass. Effective predicting Mo-yellow phase and the Mo leaching rate can accelerate the research via saving time on glass preparation and chemical durability test. Based on the glass structural gene modeling (GSgM), this paper proposed the Structure-Property (S-P) prediction models of chemical durability and the possibility of Mo-phase separation (PS, its value is x_PS) for a simulated high Mo content (MoO₃ 2.6-3.3%) HLW borosilicate solidification glass. The key elements (i.e., Na, Li, B, and Mo) leaching rate r_Na, r_Li, r_B, r_Mo as well as the Mo-phase separation x_PS were predicted by the models. The reliability and practicability of the models were proved. In addition, combined with the Structure-Composition (S-C) modeling, the C-S-P analysis was also carried out for x_PS and r_Mo.

Fifteen borosilicate glasses were designed by an one-component-at-a-time (OCAT) method. Glasses with different weights (130 g and 800 g) were prepared for each composition. Small samples with the mass of 130 g were melted and quenched. Large glass samples with the mass of 800 g were melted, and annealed. The properties of the samples were determined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) with KBr, differential scanning calorimetry (DSC) and PCT-7 day chemical durability test, respectively. Mo-phase (x_PS) was evaluated and scored for each sample by naked eyes (from 0-100%, high score means high probability of Mo-phase separation). The structural data used for modeling were derived from FTIR peak fitting area A_i. Each FTIR spectrum was decomposed into 10 Gaussian bands by a software named GRAMS AI 32 according to the same fitting rules. The S-P and S-C models were constructed by a software named JMP based on the Cornell first-order linear mixture formula. The sample (glass MV) for model validation was also prepared and measured by the same procedure.

No Mo-phase appeats in the small samples (130 g), while a serious Mo-phase separation (i.e., yellow phase and white phase) occurs in some large samples (800 g), which can be attributed to the Mo-phase accumulation and the slow cooling rate of large size glasses. The XRD patterns indicate that the main components of Mo-phase are CsLiMoO₄ (i.e., water-soluble yellow phase, yellow) and CaMoO₄ (i.e., water-resistant crystal, white). The S-P models with satisfied statistical significance (i.e., P<0.0001) and model accuracy (i.e., R_sq≥0.87) are proposed based on the A_i and glass properties. The corresponding prediction formula of the target properties (i.e., Na, Li, B, Mo leaching rate r_i, T_g, x_PS) are

In order to test the reliability of the models, a validation glass (i.e., MV) is designed. The A_i values of MV (130 g, without Mo phase separation) are used to calculate the target properties by formulas (1) to (6), and the predicted values of each property are

The model prediction results show that MV glass can perform high Mo leaching rate, exceeding the EJ-1186 standard (r_i<1 g·m^-2·d^-1). The Mo-phase possibility is 83%, indicating that MV glass has heavy Mo-phase separation. The r_B, r_Li, r_Na meets the standard requirement. The large sample MV (800g) is prepared. Large area of MV glass is covered by Mo phase separation, which is scored by 70% by naked eyes, and the r_B, r_Li, r_Na is qualified to EJ-1186. However, the r_Mo is as high as 0.91 g·m^-2·d^-1, which is close to the standard limit. Considering the test error, MV glass is not valuable for further investigation and measurement (such as viscosity, electrical resistance, liquidus temperature, etc.). The measured properties are

The S-P models indicate that within the designed glass composition, the Mo phase separation can prevent effectively with the decrease of Si—O—Si vibrations at 518-528 cm^-1, and the increase of B—O—B bending vibrations in [BO₃] units. In order to figure out the components that affect the target structure as well as x_PS and r_Mo, a detailed exploration of the components associated with the structure units that screen for PS and r_Mo from S-P models is simulated via S-C modeling. The results indicate that Li₂O and CaO enhancement can increase the formation of Mo-phase, in which CaO can lead to the formation of the water resistance white crystal CaMoO₄, while Li₂O intensifies the precipitation of water-soluble Mo-yellow phase CsLiMoO₄. SiO₂ can affect the formation of CaMoO₄ and CsLiMoO₄. Certainly, Li₂O can promote the Mo leaching rate.

A series of high Mo (MoO₃ 2.6%-3.3%), HLW borosilicate solidification glass was investigated by Glass Structural gene Modeling (GSgM) to establish the prediction models for the key elements (i.e., Na, Li, B, Mo) leaching rate r_Na, r_Li, r_B, r_Mo and the Mo-phase separation. The r_Na, r_Li, r_B, r_Mo and x_PS with a satisfied accuracy were predicted. The results were summarized as bellow:

1) The main components of Mo-phase were water-soluble yellow phase CsLiMoO₄ (yellow) and water-resistant white crystal CaMoO₄.

2) The S-P models for all the target properties exhibited high accuracy (R_sq≥0.87) and satisfied statistical significance (P<0.000 1). The model validation proved the reliability of the models.

3) Composition-structure-property analysis showed that SiO₂ variation could affect the concentration of Si—O—Si (at 518-528 cm^-1) and B—O—B bending vibrations in [BO₃] units, inducing two opposite effects on the Mo-phase separation, which could be evaluated via the simulated parameter calculation. Li₂O enhancement increased the formation of water-soluble Mo yellow phase CsLiMoO₄, and promoted the Mo leaching rate consequently. CaO could lead to the formation of the water resistance white crystal CaMoO₄.

SnO₂-based DSSCs have a potential to replace TiO₂ DSSCs due to their outstanding charge transport capabilities and stable optical properties. However, a lower conduction band position of pure SnO₂ makes it difficult to achieve an V_OC beyond 500 mV. Also, the lower isoelectric point limits dye adsorption, inherently reducing the J_SC. To address the poor performance of SnO₂ nanoparticles, modifications such as changing their structural morphology, surface coating, and ion doping can be employed to enhance charge transport and suppress charge recombination, significantly improving the photoelectric conversion efficiency of SnO₂ cells. To date, the photoelectric conversion efficiency of cells based on pure SnO₂ is 8.74%, while that of SnO₂-TiO₂ composite cells is 9.53%. Although these are significant breakthroughs, there is still a gap, compared to TiO₂ cells (i.e., 13%). It is evident that the current density of SnO₂ is able to reach a high level (i.e., greater than 20 mA·cm^-2) due to the good transport performance of SnO₂, compared to that of TiO₂, but there is still some gaps in open-circuit voltage and fill factor.

Future research aspects are as follows:

1) There is a great need for a deep understanding of electron generation, transport, loss, and collection within DSSCs, but many issues remain to be resolved. For instance, the recombination mechanism of photo-generated electrons with I₃^- is still unclear. The complex internal electron transport process has yet to be fully explained by any model, especially under certain light intensity disturbances affecting photo-generated current and voltage (IMPS/IMVS), necessitating further detailed theoretical studies. There are many possibilities for the process of electron injection from the semiconductor film to the FTO interface, such as thermal emission and tunneling, and there is currently no suitable theory to describe this interface, requiring a further research.

2) The further use of transition metals with radii that are similar to Sn⁴⁺ (such as Ti⁴⁺, W⁴⁺, and In³⁺) or the synergistic effect of co-doping metals can be explored to specifically improve various properties of SnO₂.

3) To further break through the photoelectric conversion efficiency of SnO₂, it is necessary to investigate the working process of DSSCs from a microscopic perspective and optimize each part to identify the processes limiting electron transport, improve electron yield, enhance electron transport processes, and reduce electron loss, aiming to achieve the optimum photoelectric conversion efficiency.

SiC_f/SiC ceramic matrix composites can replace high-temperature alloys in manufacturing high-temperature structural parts of aerospace engines due to their excellent properties. In a gas environment, SiC_f/SiC composite materials have a challenge from corrosion by water vapor and oxygen. The specific process of SiC_f/SiC corrosion by water vapor-oxygen coupling is not yet clarified. Therefore, investigating its corrosion behavior is of extremely important significance in guiding the protection of SiC_f/SiC from corrosion and ensuring the application of high-temperature components.

In this paper, the water-oxygen corrosion behavior of SiC_f/SiC was simulated via hydrothermal corrosion experiment in water environment and water-oxygen corrosion experiment in water-oxygen coupling environment, respectively.

In the hydrothermal corrosion experiment, SiC_f/SiC was placed in deionized water in a closed container and kept in an oven at 200 ℃ for 2 450 h. The pressure inside the container was approximately 2 MPa. After the corrosion was completed, the aqueous solution was taken out and dried in an oven at 35 ℃, and the dried powder was characterized. In the water-oxygen corrosion experiment, SiC_f/SiC was placed in a closed high-temperature furnace tube, and water vapor-oxygen mixed gas (A volume ratio of 90%∶10%) was injected into the furnace tube. The pressure inside the furnace tube was normal pressure, the temperature was maintained at 1 300 ℃ for 50-200 h.

The crystal structure of water-oxygen corrosion products was analyzed by X-ray diffraction (XRD, Smart Lab., Japan). The morphology and composition of SiC_f/SiC and its corrosion products were determined by scanning electron microscopy (SEM, Zeiss Co., Germany). The Si content in hydrothermal corrosion products dissolved in aqueous solution was measured by inductively coupled plasma (ICP, Leeman Prodigy 7, USA). The electronic states of Si and O in the hydrothermal corrosion products were characterized by X-ray photoelectron spectroscopy (ESCALAB 250Xi, XPS). The thermal stability of hydrothermal corrosion products was analyzed by thermal gravimetric analysis-differential scanning calorimetry (TGA-DSC, Netzsch Co., Germany).

Based on the observation of the microstructure, the connected pores of SiC_f/SiC composite materials are the entry and exit channels for corrosion media/products. Corrosion products mainly exist in three types of areas, i.e., pores remaining during the precursor impregnation process, lamellar holes produced in the gaps between fiber cloths, and suture holes in the z direction.

In a hydrothermal environment at 200 ℃, the corrosion of SiC_f/SiC in water is a volume expansion process, the matrix becomes loose, and the pores are filled with corrosion products. After hydrothermal corrosion for 2 450 h, the Si content in the milky white colloid measured is 1 045.4 mg/L. According to the EDS analysis, the O/Si atomic number ratio is 2.9, and the chemical composition is close to H₂SiO₃ (SiO₂·H₂O). The comprehensive analysis by XRD (PDF 38-0448) and XPS (O 1s has two chemical states, namely Si—O and Si—O—H) indicates that the milky white product is H₂SiO₃.

In the water-oxygen coupled corrosion environment at 1 300 ℃, the fibers and interface layers of the SiC_f/SiC composite material are corroded, and cracks are formed. After corrosion for 200 h, the thickness of the sample expands from 4.85 mm to 6.66 mm, which is increased by 37%. The internal structure of the sample becomes loose, the corrosion intermediate product is H₂SiO₃, and the final product is cristobalite SiO₂.

This article studied the corrosion process of SiC_f/SiC composite materials in hydrothermal (oxygen-free) and water-oxygen coupling environments. The connected pores of SiC_f/SiC composite materials were channels for corrosive media/products, which could not be avoided. In an oxygen-free hydrothermal environment at 200 ℃, the corrosion of SiC_f/SiC by water was a volume expansion process, forming a milky white product H₂SiO₃. In a water-oxygen coupled corrosion environment at 1 300 ℃, the SiC_f/SiC composite material expanded in volume and formed cracks. The fibers and interface layers were corroded and the structure became loose. The corrosion product was cristobalite SiO₂.

Some prospects for future development were provided. In the future, with the continuous development of precise temperature control, uniform, and rapid heating synthesis technologies such as microwave synthesis, the combination of artificial intelligence control technology and synthesis equipment, the advancement of multi index observation in-situ experimental technology, and the precise observation and control of synthesis heating rate, temperature field, and concentration field are effective ways to achieve precise synthesis of hydrotalcite and precise control of interlayer spacing. And it is expected to achieve precise control of the types, quantities, and layout of interlayer objects according to demand. The influences of interlayer object types, quantities, arrangement attitudes, and pores on the electrolyte ion transport, and the related mechanism on the interlayer active site electrochemical reactions, and the related mechanism on the interlayer spacing and layer structure evolution can be investigated more accurately. The combination of multi-index observation in-situ synthesis experimental technology with the first-principles, molecular dynamics, and machine learning simulation methods can be ultilized to analyze the microstructure, electrochemical reactions, and other processes.

Al₂O₃-C refractories are one of the important categories of refractory materials in steel smelting. Improving their service life has a great application value. The service life of Al₂O₃-C refractories is closely related to their mechanical properties. Therefore, an effective approach to improve the mechanical properties of Al₂O₃-C refractories and further enhance their service life is to introduce a structural reinforcement such as carbon fibers. However, using commercial carbon fibers directly as a structural reinforcement cannot bind with other components of the material tightly at various temperatures due to its smooth surface and low reactivity, thus restricting the reinforcing effect of carbon fibers. Therefore, surface treatment such as thermal oxidation on carbon fibers is an effective way to improve the reinforcement effect of carbon fibers and improve the mechanical properties of carbon fibers reinforced Al₂O₃-C refractories. In this paper, short carbon fibers were treated by a thermal oxidation method, and Al₂O₃-C refractories were then prepared using the treated carbon fibers as a reinforcement. The structural evolution of short carbon fibers with different degrees of oxidation in Al₂O₃-C refractories, as well as the effect of adding thermal oxidation short carbon fibers on the mechanical and thermal shock resistance properties of Al₂O₃-C refractories were investigated.

White corundum, active alumina powder, silicon powder, boron carbide, flake graphite, nano carbon black, and short carbon fiber were used as raw materials, and thermosetting phenolic resin was used as a binder. In addition, some commercial carbon fibers were heated in air at 400, 500 ℃, and 600 ℃ for 0.5 h to prepare thermal oxidation carbon fibers in order to investigate the effect of thermal oxidation treatment of carbon fibers on their structural evolution and service performance in Al₂O₃-C refractories.

The Al₂O₃-C samples without carbon fibers and with untreated carbon fibers, as well as thermal oxidation carbon fibers at different temperatures (i.e., 400, 500 ℃, and 600 ℃) were numbered as sample BK, sample F, sample FT4, sample FT5, and sample FT6, respectively. The raw materials were mixed evenly and then shaped into 25 mm×25 mm×140 mm at 120 MPa. Each sample was cured at 200 ℃ for 24 h, and then heated in a saggar filled with coke grit at 1 200, 1 300 ℃, and 1 400 ℃ for 5 h, respectively.

The micromorphology of samples was determined by a field emission scanning electron microscope (TESEM). The apparent porosity and bulk density of samples were measured based on the Archimedes principle. The CMOR and HMOR of samples were measured by a three-point bending method. The CCS of samples were measured by a uniaxial compression method. The thermal shock resistance of the samples was evaluated according to the residual strength ratio of the CMOR (CMORrsr). The elastic modulus (E) of samples was analyzed by a resonance frequency and damping analyzer. The fracture-related parameters of samples were detected by a single-edge notched beam (SENB) method.

Based on the TESEM images, the surface of the untreated carbon fibers are relatively smooth without obvious defects. After thermal oxidation at 400 ℃, the morphology of carbon fibers does not change much and still have a relatively smooth and intact surface. After thermal oxidation at 500 ℃ and 600 ℃, however, visible structural changes occur on the surface of carbon fibers, becoming rough in some areas. Also, the reaction between carbon fibers and Si heat-treated at 1200 ℃ occurs slightly, leading to that the surface morphology of carbon fibers is similar to their initial state. After heat treatment at ≥1300 ℃, some structures in the form of whiskers and particles appear on the surface of carbon fibers. In addition, for carbon fibers after thermal oxidation treatment, in addition to growing the structures outside the surface of fiber like the original carbon fibers, it is also possible to further react in fiber surface defects to generate new structures inside the fibers. This reaction process will continuously increase the defect size of the fibers and damage the structural integrity of the fibers.

Although the addition of short carbon fibers reduces the compactness of Al₂O₃-C refractories, their introduction can still play a positive role in improving the mechanical properties. For instance, for Al₂O₃-C refractories containing carbon fibers treated at 500 ℃, after being heat treated at 1 400 ℃, their CMOR, CCS HMOR are increased by 28.2%, 22.4%, and 87.2%, respectively, compared with the control material. This can be due to the high-temperature chemical reaction between carbon fibers and other components of refractories, as well as the additional energy dissipation mechanism introduced by fibers, which greatly increases the energy required for crack propagation, thereby hindering crack propagation and improving the mechanical properties of refractories.

Thermal oxidation treatment could create defects on the surface of carbon fibers, thereby affecting their reactivity and mechanical properties. Adding them to Al₂O₃-C refractories could promote the formation of in-situ ceramic phases due to the surface defects, having positive impacts on the improvement of mechanical properties. However, the temperature of thermal oxidation treatment should be appropriate. If the temperature was too low or too high, it could not fully exert the reinforcing effect of carbon fibers. In addition, although the addition of thermal oxidation carbon fibers had a positive impact on the performance improvement of refractories in some cases, there were still weaknesses in the performance.

Environmental pollution caused by personal care products and synthetic substances become worse. Bisphenol A (BPA) as a type of endocrine disrupting chemical is detected in water, soil, air, urban waste and food. BPA is difficult to be removed from water body due to its strong biological toxicity and environmental persistence, so it is beneficial to designing the related efficient treatments. At present, main methods removing BPA include adsorption, nanofiltration, photochemical oxidation and electrochemical oxidation, in which photocatalytic oxidation technology has received much attention. TiO₂ is extensively investigated due to its advantages. Although TiO₂ has an excellent photocatalytic performance, it has significant drawbacks, such as low visible light utilization and easy recombination of photo generated carriers. Loading is an effective method to improve photocatalytic capability. In this paper, Fe³⁺/CDs-TiO₂ composite photocatalyst was prepared by a sol-gel method.

For the preparation of Fe³⁺/CDs-TiO₂ catalyst, Ti(OBu)₄, anhydrous ethanol and acetic acid were mixed under stirring to obtain a transparent solution. CDs and Fe(NO₃)₃·9H₂O were added into the solution under stirring until forming a gel. The gel was heated in an oven at 70 ℃ to obtain yellow particles. The particles were ground into the finer particles and calcined in a muffle furnace at 300 ℃ for 4.5 h, hence obtaining Fe³⁺/CDs-TiO₂. The photocatalytic performance of Fe³⁺/CDs-TiO₂ was analyzed with BPA as a target pollutant. Fe³⁺/CDs-TiO₂ was added into BPA aqueous solution, stirred in a dark environment for 20 min to achieve adsorption equilibrium. The photocatalytic reaction occurred after turning on an Xenon lamp. The concentrations of samples taken at regular intervals were determined by the HPLC method. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet visible diffuse reflection spectroscopy (UV-Vis DRS) and electrochemical method.

Compared with TiO₂, the absorption spectra of Fe³⁺/CDs-TiO₂ range to visible light zone and photoinduced electrons transfer quickly through interface chemical bonds, indicating that the co-doping of Fe³⁺/CDs boosts a photocatalytic efficiency. The degradation efficiency of BPA can be 92.8% after 120 min with Fe³⁺/CDs-TiO₂ at a loading ratio of Fe³⁺/CDs of 0.5% or 1.5%. Fe³⁺/CDs-TiO₂ has a satisfied stable and reusable performance for 86% BPA, which is still degraded after 7 cycles. The photocatalytic degradation process of BPA with Fe³⁺/CDs-TiO₂ follows the first-order kinetic equation, and the reaction rate constant is 0.022 16 min^-1. Based on the results of free radical capture experiments, the holes are the dominant species for BPA degradation, and the toxicity of the intermediates decreases, which is simulated by Toxicity Estimation Software Tool (T.E.S.T). The mechanism of Fe³⁺/CDs-TiO₂ photocatalytic degradation of BPA was analyzed based on main degradation substances and dominant intermediates. There is an electron coupling phenomenon between the orbital and the conduction band of TiO₂, forming Ti—O—C bonds. Electrons can quickly transfer from the TiO₂ conduction band through Ti—O—C bonds at the interface to the surface of the composite catalyst, and react with dissolved oxygen to generate ·O₂^-. The holes on the valence band can directly react with organic molecules or form hydroxyl radicals, which almost decompose organic molecules. In addition, the photogenerated electrons on the conduction band also reduce the loaded Fe³⁺ in-situ to Fe²⁺, which reacts with dissolved oxygen to generate Fe³⁺ and ·O₂^-. The Fe³⁺→Fe²⁺→Fe³⁺ microcirculation effectively transfers photogenerated electrons.

The co-modification of Fe³⁺ and CDs widened the spectral response range of TiO₂, and formed interface chemical bonds that provided channels for photoelectron transfer, suppressing carrier recombination and improving photocatalytic efficiency. When the loading amounts of Fe³⁺ and CDs were 0.5% and 1.5%, respectively, the composite material had the optimum degradation performance. In the presence of visible light, the degradation efficiency of BPA could reach 92.8% after 120 min. After 7 cycles, Fe³⁺/CDs-TiO₂ still performed well and degradation efficiency was 86%. Fe³⁺/CDs-TiO₂ photocatalytic reaction of BPA followed the first-order reaction kinetic equation, with a reaction rate constant of 0.022 16 min^-1. According to the results of free radical capture experiments, the holes were the main species for the degradation of BPA, and the toxicity of the photocatalytic degradation products gradually decreased.