Journal of the Australian Ceramic Society最新文献

Ln₂(MO₄)₃ (Ln = La and Sm; M = W and Mo) nanomaterials are synthesized by auto ignited combustion method. The synthesized materials are characterized by X-ray diffraction, vibrational spectroscopy, transmission electron microscopy, scanning electron microscopy and impedance spectroscopy. The structural analysis established monoclinic structure for the synthesised nanoparticles. The average crystallite size estimated using Debye–Scherrer formula is obtained in the range 27 to 35 nm. Raman and FTIR studies revealed two types of WO₄ and MoO₄ tetrahedrons in tungstate and molybdate compounds, respectively. TEM micrographs show that the nanoparticles are spherical in shape with narrow size distribution. SEM micrographs of bulk ceramics showed high densification, low porosity and grain distribution of distinct dimensions. EDS analysis confirmed the chemical composition of the materials and agreed with their actual stoichiometry. The presence of grain, grain boundary and electrode contribution to impedance spectra of bulk ceramics was analysed using complex impedance plot. Arrhenius plots of all the prepared materials show almost a linear behaviour with a small deviation noticed at particular temperatures. The conductivity studies of prepared materials showed oxide ion and mixed electron-proton conduction.

The perovskite Ce_1-xK_xMoO₃, where x = 0.0, 0.2, and 0.4, was prepared using sol–gel technique. Samples were characterized by X-ray diffraction (XRD), differential scanning calorimetry DSC, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, impedance spectroscopy UV–VIS, diffuse reflectance spectroscopic, and photoluminescence (PL). Besides, the XRD and Raman spectroscopy revealed an orthorhombic phase with a Pnma space group for Ce_1-xK_xMoO₃ samples. XPS analysis proved the existence of Mo³⁺ and Mo⁴⁺ ions. On the other hand, Raman spectroscopy has particularly shown the existence of the B_1g mode associated to the MoO₆ octahedron. And the DSC curves mark the absence of inflections which qualitatively shows the thermal stability of Ce_1-xK_xMoO₃. Moreover, impedance spectroscopy confirmed that DC conductivity can be justified by the Arrhenius law at 475–600 K temperature range; the activation energy (≈0.314 eV) decreased with the potassium amount and by Mott’s VRH model for T < 445 K. In addition, the density’s greatest value of Fermi states, N(E_F) values 1.07 10²³ eV⁻¹ cm⁻³, and a low relaxation time τ_rel≈0.5 μs were obtained with CKMO04 sample. In the end, the Tauc curves revealed that the bandgap decreased from 3.10 to 2.77 eV with K⁺ amount; the PL measurements exhibited intense emission of visible and near-infrared light under UV light excitation. In conclusion, all results found allow Ce_1-xK_xMoO₃ to be too useful in the field of optoelectronics.

The influence of different dispersants on the dispersion of Y₂O₃ sintering aid in B₄C powder and the microstructure and performance of the subsequently hot-pressed ceramics were studied in this paper. The results indicated that ammonium polycarboxylate (APC) could effectively enhance the distribution of Y₂O₃ in B₄C powder, and further improve the distribution homogeneity of the formed second phase YB₄ in the fabricated ceramics. Polyethyleneglycol (PEG) 600 was beneficial to breaking the Y₂O₃ agglomeration in B₄C powder and improving the distribution of YB₄. The remaining PEG 600 in the mixed powder would react with B₄C and Y₂O₃ particles to form the dendritic-structure second phase in the sintering process, which comprised some whisker-like branches and a layer of film. The distribution of YB₄ in the fabricated ceramics was slightly improved by adding sodium citrate (SC) dispersant. Y₂O₃ reacted with B₄C to form the intergranular and intragranular YB₄, and liquid phase was formed in the sintering process, facilitating the rearrangement of B₄C grains and improving the densification. The dispersant APC could improve the homogeneity of YB₄, promoting the densification and strength of the ceramics.

This work evaluates the effects of manganese (Mn) doping on the morpho-structural features, mechanical performance, and in vitro biological response of beta-tricalcium phosphate (β-TCP) derived bioceramics for bone tissue engineering applications. Five different Mn doping levels (i.e., 0.01%, 0.05%, 0.1%, 0.5%, and 1 wt.%) were investigated, with the β-TCP-based bioceramics being sintered at four temperatures (i.e., 1000, 1100, 1200, and 1300 °C). A densification improvement was induced when using Mn in excess of 0.05 wt.%; the densification remained stationary in the sintering temperature range of 1200 − 1300 °C. The structural analyses evidenced that all samples sintered at 1000 and 1100 °C were composed of β-TCP as major phase and hydroxyapatite (HA) as a minor constituent (~ 4–6 wt.%). At the higher temperatures (1200 and 1300 °C), the formation of α-TCP was signalled at the expense of both β-TCP and HA. The Mn doping was evidenced by lattice parameters changes. The evolution of the phase weights is linked to a complex inter-play between the capacity of the compounds to incorporate Mn and the thermal decomposition kinetics. The Mn doping induced a reduction in the mechanical performance (in terms of compressive strength, Vickers hardness and elastic modulus) of the β-TCP-based ceramics. The metabolic activity and viability of osteoblastic cells (MC3T3-E1) for the ceramics were studied in both powder and compacted pellet form. Ceramics with Mn doping levels lower than 0.1 wt.% yielded a more favorable microenvironment for the osteoblast cells with respect to the undoped β-TCP. No cytotoxic effects were recorded up to 21 days. The Mn-doped β-TCPs showed a significant increase (p < 0.01) in alkaline phosphatase activity with respect to pure β-TCP.

The electrospinning technique is used to synthesize several types of mesoporous manganese oxides, namely Mn₂O₃, Mn₃O₄, and hybrid manganese oxides. The as-spun nanofibers are heated at different temperatures from 500 to 1000 °C for 2 h. XRD analysis reveals that the Mn₂O₃ phase starts to form at 500 °C, whereas at 900 °C, Mn₂O₃ and Mn₃O₄ are co-existent and at 1000 °C, Mn₃O₄ is the sole phase. The mesoporous material’s behavior can be seen in all isotherms of the prepared manganese oxide nanofibers. The maximum surface area of 1306.98 m²/g is achieved for the sample calcined at 500 °C, which is one of the highest surface areas recorded for Mn₂O₃ as compared with the literature.

A series of new Nd_(1-x)Sr_xZrO_(3.5–0.5x) (0 ≤ x ≤ 1) multiphase ceramic waste forms, which can simultaneously immobilize An and Sr (with Nd³⁺ simulating An³⁺), were synthesized in situ by a sol-spray pyrolysis method. These multiphase ceramics are composed of a cubic pyrochlore phase Nd₂Zr₂O₇(NZO) and an orthogonal perovskite phase SrZrO₃(SZO) without any impurities. The content of the two phases can change regularly with the change of x. Nd and Sr can occupy the ceramics’ most stable lattice sites. The measured density of multiphase ceramics can reach more than 88% of the theoretical density. At the same time, the leaching rates of target Nd, Sr and Zr elements reached ~ 10⁻⁵ g·m⁻²·d⁻¹, ~ 10⁻³ g·m⁻²·d⁻¹, and ~ 10⁻⁷ g·m⁻²·d⁻¹ at 90 ℃ and deionized water for 72 days, respectively, which shows that the multiphase ceramics had strong leaching resistance. The experimental results confirm that the new multiphase ceramics can immobilize An and Sr simultaneously and separately, and they have high chemical stability and strong adaptability to waste components. The multiphase ceramics is expected to be an ideal candidate waste form for An and Sr.

Ferrite polymer composites, a seamless fusion of magnetic and polymeric properties, embody both strength and flexibility, paving the way for a new era of innovative applications. Composite nanomaterials of BaFe₂O₄/polypyrrole were synthesized by combining spinel ferrites and polypyrrole (PPy) by standard ceramic method. The X-ray diffraction (XRD) measurements revealed that the spinel ferrites were uniformly distributed throughout the single-phase PPy-matrix. Because PPy is amorphous, the size of the crystallites in nanocomposites grew as the amount of spinel ferrite in the matrix went up. At higher frequencies, the dielectric loss of the composites decreases due to reduced polarization effects. The addition of nanoparticles to the PPy matrix made the conduction channel narrower, leading to increased activation energy and resistivity. The magnetic properties of the composites were enhanced by adding ferrite components. The obtained results indicate that the prepared composites may be a potential candidate for EMI shielding applications.

This work reports the wear and high-temperature stability of TiCN-WC-Co-Cr₃C₂-HfC-Si₃N₄ cermets developed by spark plasma sintering (SPS). The addition of Si₃N₄ in the range of 5 wt. % to 15 wt. % in TiCN-WC-Co-Cr₃C₂-HfC cermet composition showed hardness of the cermets in the range of 10.2±0.05 to 11.7±0.05 GPa. Among the three cermets developed, 60TiCN-15WC-10Co-5Cr₃C₂-5HfC-5Si₃N₄ possessed a hardness value of 11.7±0.05 GPa and fracture toughness value of 15.1±3.5 MPa√m. The wear behaviour of the cermets was studied using a pin-on-disc machine with cermets as a pin on EN 31 steel counter disc material with three different sliding velocities in the range of 0.23–0.35 m/s, at a constant normal load of 20 N for a duration of 5 min. 60TiCN-15WC-10Co-5Cr₃C₂-5HfC-5Si₃N₄ cermet showed a high wear resistance at all the three sliding velocities compared to the other cermet composition. High-temperature stability of the cermets was assessed by heating the cermet samples to 600 °C, 800 °C and 1000 °C and holding them for about 4 h followed by cooling within the furnace itself. All the three cermets were stable up to 800 °C. Cermet 60TiCN-15WC-10Co-5Cr₃C₂-5HfC-5Si₃N₄ showed less affinity for oxidation after heating, and hence, it has good thermal stability than other cermet compositions.

Hierarchical porous ZrO₂/Al₂O₃ ceramics with controllable pore structure were fabricated by gel-foaming method using nontoxic sodium alginate as gelling agent. Both the rheological property of ceramic slurry and the curing mechanism of gelatin system were studied. The effects of ZrO₂ content and sintering temperature on the pore structure and properties were also investigated. The three-dimensional net structure forms between calcium ion and sodium alginate molecule; then, the ceramic powder can realize in situ solidification. The porosity changes from 33 to 74% with different ZrO₂ content and sintering temperature. The macropores can be controlled through adjusting the foaming agent and ZrO₂ contents. The mesopores are mainly regulated by sintering temperature. The porosity and pore structure can be tailored through optimizing the gel-foaming and sintering process parameters. The sintering temperature has important influence on the mechanical properties. The porous ceramics with 25% ZrO₂ content sintered at 1550°C shows the highest compressive strength of 130MPa. The mechanical properties are improved with the micro-crack toughening and phase transformation mechanisms of ZrO₂ phases. Hierarchical porous ceramics with more inter-connective pores, high specific surface area, and suitable strength are promising for filtration and catalyst support applications.

ZrO₂ is widely used. However, surface hydrophilicity is harmful to waterproof devices. In this work, epoxy-based polyhedral oligomeric silsesquioxane (POSS) was chemically bonded to ZrO₂ sheet surface for weather-resistant hydrophobicity and anti-adherence property. First, ZrO₂ sheet was modified with hydroxyls, followed by amino modification. Then, surface POSS modification was performed via ring-opening addition. Next, composition and micro-morphology of POSS-treated sheet were clarified. Ultimately, the dependence of water contact angle of POSS-modified sheet on POSS solution treating time was researched, and the highest contact angle of 132.6° was gained by 24-h treating. Acid corrosion, alkali corrosion, and ultraviolet radiation for 48 h were employed to verify good weather resistance with contact angles over 120°. POSS-modified sheet had good anti-adherence capacity. Cooperation of POSS and ZrO₂ was utilized to obtain low surface energy and high surface roughness. This work might help to obtain hydrophobic ceramics as catalyst supports for oil-phase reactions.