Ceramics International最新文献

This study investigates the magnetic response of Ho³⁺ doped Ni_0.4Cu_0.6Ho_yFe_2-yO₄ (y = 0.0, 0.02, 0.04, 0.06, and 0.08) spinel ferrites (SFs) and their correlation with crystallite size. The synthesis was achieved using a sol-gel auto-combustion (SGAC) route and performed different characterizations, including X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive x-ray (EDX), Inductively coupled plasma atomic emission spectroscopy (ICP-AES), and vibrating sample magnetometer (VSM) analysis. The cubic spinel phase was verified via XRD in pure NCF and Ho³⁺ doped NCF samples. The lattice constant (a) was improved from 8.344 Å to 8.378 Å. The substitution of Ho³⁺ ions led to a decrease in porosity from 42.22% to 39.54%. The introduction of Ho³⁺ ions also reduced the crystallite size (D) from 37.05 nm to 27.72 nm. The specific surface area (S) was increased from 27.44 g/cm² to 36.14 g/cm² with the doping of Ho³⁺. The average particle size (D_S) was decreased from 54 nm to 35 nm. The EDX and ICP-AES analyses confirmed the good agreement with the theoretical composition. The VSM measurements provided insights into their magnetic properties. Furthermore, the doping of Ho³⁺ ions enhanced coercivity (H_C), while reducing saturation magnetization (M_S) from 64.35 emu/g to 16.22 emu/g. The decrease in crystalline anisotropy (K) observed at higher concentrations of Ho³⁺ may result from the increase in coercivity, potentially attributable to the smaller crystallite size of the single-domain SFs particles. The single-phase matrix and their magnetic behaviour showed that the Ho³⁺ doped Ni-Cu SFs samples are suitable for high-frequency applications.

This research offers a comprehensive exploration of the effects of In-doping on the characteristics of CdS nanopowders (NPs). The structural and morphological properties of In-doped CdS nanostructures were investigated, revealing significant changes induced by In-doping. X-ray diffraction (XRD) analysis verified the formation of CdS phase. Determination of crystallite size (D) demonstrated a decrease from 27.0 nm for undoped CdS to 23.0 nm for CdS doped with 12% In-doped. Field-emission scanning electron microscopy (FESEM) imaging showed grain-like structures with sizes of 20 – 35 nm, showing variations in particle size distribution with increasing In-dopant concentration. Photoluminescence (PL) analysis illustrated changes in PL intensity and emission peak wavelengths due to In-doping. PL intensity decreased after In-doping. Additionally, a blue-shift in emission peak wavelengths indicated changes in the bandgap energy of CdS induced by In-doping. UV-Vis spectroscopy assessed the optical properties, revealing shifts in absorption and transmission spectra du to In-doping. In-doping enhanced absorption within the 400 – 500 nm range while decreasing absorption within 600 – 1000 nm. Transmission spectra displayed increased transparency after In-doping, attributed to modifications in band structure and morphology. Reflectance spectra initially increased with In-dopant concentration within 400 – 500 nm, followed by a decrease, suggesting alterations in electronic and structural properties. Estimation of band gap energy (E_g) unveiled an increase in E_g for In-doped CdS nanostructures compared to undoped CdS, likely due to reduced crystallite size and the Burstein-Moss effect induced by In-dopant ions. Raman analysis revealed a shift in peak positions and changes in intensity after In-doping, with a decrease in the 2LO/LO ratio indicating a deterioration in crystalline quality after In-doping. Overall, this comprehensive investigation provides valuable insights into the structural, morphological, optical, and electrical properties of In-doped CdS nanostructures, pivotal for their promising applications in optoelectronic devices and photovoltaics.

The durability of thermal barrier coatings (TBCs) is significantly influenced both by the ceramic top coat and the bond coat. In this study, novel YbGdZrO ceramic coats were deposited on the surfaces of three types of Cr-modified (Ni, Pt)Al bond coats via electron beam physical vapor deposition (EB-PVD) technique. These Cr-modified (Ni, Pt)Al bond coats were fabricated by magnetic sputtering Cr onto the (Ni, Pt)Al bond coats with varying sputtering times of 30, 60, and 90 minutes. The results indicates that the thickness of the Cr-modified layer increases with the extension of sputtering time. A short deposition time of 30 min is adequate for achieving an appropriate Cr content in the (Ni, Pt)Al bond coats, which ensures selective oxidation of Al element within the bond coat and further enhances the metallurgical interfacial bonding strength with the ceramic coat by adapting to the concentration gradient diffusion. However, as the sputtering time is extended to 60 and 90 minutes, α-Cr begins to form in the Cr-modified (Ni, Pt)Al bond coats, which negatively affects the oxidation resistance of the bond coat. Consequently, the thermal shock life of the TBCs samples is significantly reduced with increasing sputtering time. The longest thermal shock lifetime is obtained on the bond coat with Cr plating time of 30 minutes owing to a differing thermally grown oxide formation and failure mechanism.

The mechanical behavior of ceramic composite armor is related to the type of projectile and the material properties of each component under high-speed impact. There exists a coupling effect between the ceramic, backing material, and the projectile during the impact process. Especially for brittle projectiles, there is a clear correlation between the damage evolution and the backing material. This study investigates the mechanical behavior and ballistic response of B₄C ceramic composite armor resisting T12A steel projectiles using three different backing materials: Q235 steel, Kevlar, and UHMWPE laminates. Experiments and numerical simulations were conducted. The results show that the Rosin-Rammler distribution model can well describe the mass distribution of fragments of the brittle T12A steel projectile. The protective performance of ceramics against the T12A steel projectile depends on the dwell time, where the Q235 steel backing plate can prolong the interaction time between the projectile and the ceramic, leading to more erosion and fracture of the projectile. The fiber laminate primarily absorbs the remaining kinetic energy of the projectile through its own tensile and shear failure, without causing damage to the projectile. Due to its lower shear strength, the Kevlar laminate is quickly penetrated by the residual projectile, while the UHMWPE laminate undergoes more tensile deformation at the sublayer interface due to its higher tensile strength, absorbing more kinetic energy from the projectile. Furthermore, both the projectile and B₄C ceramics fail due to the complex stress caused by compression waves and tensile waves. When the backing plate is Q235 steel, the peak stress inside the projectile is higher, resulting in more severe fragmentation of the projectile. However, the peak stress inside the ceramic remains relatively similar regardless of the different backing materials.

Photosensitive glass-ceramics exhibit significant potential to replace silicon materials in the microfabrication of micro-electro-mechanical-system (MEMS) devices. However, they are constrained by the limitations of a conventional 320-nm photolithography process. Therefore, developing an ideal industrial i-line (365 nm) photolithography for Li₂O-Al₂O₃-SiO₂ photosensitive glass-ceramics is urgently needed. This study initially explores the impact of a facile i-line photolithography on the structure and physicochemical properties of photosensitive glass ceramics. We experimentally showcase a direct, scalable, and straightforward i-line photolithography technique for Li₂O-Al₂O₃-SiO₂ photosensitive glass ceramics. Our research concentrates on how the exposure time affects the properties of Li₂O-Al₂O₃-SiO₂ photosensitive glass ceramics, particularly regarding nucleation and crystallization. This is achieved by adjusting the exposure time parameter and utilizing XRD, etching experiments, SEM, TEM, and other tests under a i-line light source. By optimizing the exposure process parameters, we also modify the annealing process parameters affecting the crystallization of lithium metasilicate in the exposed areas. Under a treatment process involving an exposure time of 20 minutes, a nucleation temperature of 500°C, a crystallization temperature of 630°C, and a nucleation/crystallization duration of 2 hours, the sample achieves the highest crystal quantity and the optimal thickness-etching rate ratio.

Alumina toughened zirconia (ATZ) ceramics combine high biocompatibility with remarkable mechanical properties, making them suitable for dental and orthopedic implant applications. Producing these ATZ ceramics using slurry-based additive manufacturing necessitates homogeneous, stable suspensions with controlled particle sizes. Stabilizing such systems with the appropriate type and amount of dispersant is challenging, particularly since multi-component systems are prone to hetero-coagulation. In this study, ATZ powders with different surface areas were investigated to determine the optimum concentration of three commercially available dispersants: Darvan CN, Darvan 821A, and Dolapix CE64, which have been successfully used to stabilize Al₂O₃ and 3Y-TZP suspensions. Based on zeta potential (0.01 vol% suspensions), agglomerate size (0.01 vol% suspensions), sedimentation (10 vol% slurries), and rheological (40 vol% slurries) characterization, the optimum dispersant concentrations were found to be 0.50 mg/m² for Dolapix CE64, 0.75 mg/m² for Darvan 821A, and 1.50 mg/m² for Darvan CN. Among the studied dispersants, Dolapix CE64 was the most effective in terms of reduced sedimentation, smaller agglomerate size (0.70 μm), flow behavior, and low resistance to structure breakdown. The rheological assessment showed that slurries prepared with ATZ powder featuring a smaller specific surface area (7.3 m²/g) resulted in lower viscosity, critical stress, and equilibrium storage and loss moduli compared to those prepared with higher specific surface area (13.3 m²/g) starting powder. The sedimentation analysis however revealed that the larger specific surface area ATZ powder exhibited higher slurry stability. While 38 vol% ATZ pastes without dispersant showed inhomogeneous extrusion and the presence of aggregates, the filaments extruded from 45 vol% paste with 0.50 mg/m² Dolapix CE64 had a homogeneous and smooth structure and were free of aggregates, highlighting the importance of the dispersant addition for DIW.

Hydrogen pumps, crafted from proton-conductive ceramic electrolyte and paired with either oxide or metallic electrodes, have been designed for the extraction of hydrogen isotopes from helium gas mixtures containing 0.1% hydrogen isotopes, particularly within the context of TES for nuclear fusion reactors. This study presents the electrochemical hydrogen permeation research conducted on the perovskite proton conductor materials BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb) and BaZr_0.8Y_0.16Ni_0.04O_3-δ (BZYN) under these operational conditions. It was observed that nickel electrodes provided superior performance over SrFe_0.8Mo_0.2O_3-δ (SFM) electrodes in terms of hydrogen extraction efficiency. Hydrogen pumps that integrated BZCYYb as the electrolyte with nickel electrodes showed enhanced efficiency, while those utilizing BZYN as the electrolyte coupled with nickel electrodes demonstrated greater stability. Furthermore, the study explored the voltammetric nonlinearity at low hydrogen concentrations and the dependency of concentration polarization efficiency on both voltage and temperature, aiming to establish optimal conditions that balance stability and efficiency for both types of hydrogen pumps.

Ceramic industry consumes large amounts of raw materials, including costly and environmental impact iron based-pigments. Steel rolling (SR) and wire drawing (WD) waste, rich in iron (> 67 wt. %), present a viable alternative. This study aims to develop high value stoneware pastes for tableware products by substituting commercial pigments with SR and WD. The influence of incorporation content (3, 5 and 10 wt. %) and pre-treatments (sieving at 250, 150 and 63 μm, and grinding followed by sieving at 63 μm) on the samples properties was assessed including weight loss, firing shrinkage, apparent density, flexural resistance, and water absorption. The laboratory scale results revealed that darker hues, ranging from grey to reddish, were obtained when SR and WD were incorporated in the stoneware paste (beige colour). The smaller the particle size, more homogeneous is the developed colour, which is intensified as higher is the incorporation level.

The prototypes (plates) were characterized in terms of thermal shock, edge impact, cracking and microwaves resistance, water absorption, and leaching behaviour, demonstrating that they met the industrial requirements. Thermal shock resistance was enhanced and the levels of leached Fe, Pb, Cd, Ni, Cr, Mo, V, Zn, and Cu, were below permissible limits (EU Ceramic Directive 84/500/EEC, Decree-Law nº152/2017, Decree-Law nº236/98 and WHO Guidelines for Drinking-Water Quality) confirming their effective immobilization. Concluding, this work shows the viability of using mill scale waste as a valuable secondary raw material in stoneware pastes acting as a chromophore agent. Dark colours are obtained while preserving the product technical characteristics, promoting sustainable production and reducing landfilled waste.

In today's modern world, energy consumption continues to escalate. In such cases, smart windows play a crucial role in reducing energy consumption and enhancing the quality of life. Electrochromic devices (ECDs) -based smart windows rely profoundly on nickel oxide (NiO) thin films, which act as a counter electrode in ECDs. This work aims to fabricate NiO thin films, with the intention of achieving ultrafast ECD. Through the sputtering technique, energy- efficient ECD is obtained with the highest optical modulation of 60% at a rapid switching speed of 0.55s for bleaching and 0.95s for coloration. We have also investigated the structural, morphological, vibrational, and optical properties of NiO thin films. XRD analysis revealed the less crystalline or near amorphous nature of NiO thin film. XPS, PL, and Raman studies confirm the existence of defects in the film. The favourable, less crystalline nature, along with the presence of defects, facilitates ultra- fast ion intercalation and de-intercalation process. We believe that prepared NiO film can be used as a promising anodic colourant in electrochromic smart windows with applications in energy-efficient buildings.

A series of new x(yZnO/Al₂O₃)-(1-x)Ba_0.5Sr_0.5TiO₃ (x = 10, 20, 50 wt%, y = 1, 1.3, 1.5 mol) ceramics were prepared by solid-phase method. The effects of ion diffusion and compound effect on the lattice vibration and dielectric properties of Ba_0.5Sr_0.5TiO₃ were studied. When ZnO and Al₂O₃ are equimolar, the two react to form ZnAl₂O₄. Under the composite effect, the dielectric permittivity of Ba_0.5Sr_0.5TiO₃ is effectively reduced, T_c moves to high temperature, and the tunability gradually increases. When ZnO is in excess, T_c remains basically unchanged, proving the unique role of the spinel structure. Because ZnO can fully diffuse into Ba_0.5Sr_0.5TiO₃, extremely high tunability is achieved through defect engineering. 50 wt%(ZnO/Al₂O₃)-50 wt%Ba_0.5Sr_0.5TiO₃ achieved excellent microwave dielectric properties, with dielectric permittivity, tunability and Q value of 201, 23.6% and 368, respectively. In addition, ZnAl₂O₄-Ba_0.5Sr_0.5TiO₃ composite ceramics were successfully prepared by directly compounding Ba_0.5Sr_0.5TiO₃ with oxides, which greatly reduced energy loss.