Journal of the Australian Ceramic Society最新文献

A set of glasses of composition, (ZnO)_0.3-(V₂O₅)_0.6 − x-(B₂O₃)_0.1-(MnO)_x, where x = 0.05 to 2, was synthesized by melt quenching method. The powder XRD studies revealed nanocrystalline phase of the samples. Room temperature density is found to increase and molar volume to decrease with MnO concentration. Conductivity of the glasses has been measured for the temperature range 303–523 K. The conduction mechanism at high temperature is found to be consistent with Mott’s small polaron hopping and Greaves variable range hopping at low temperature. Gamma ray shielding characteristics were evaluated using Phy-X/PSD software for the energy range 0.005–15 MeV. Mass attenuation coefficient (MAC) and linear attenuation coefficient (LAC) were found to be maximum at 0.005 MeV for all the samples. Observed variations of all the shielding characteristics showed evidence for photoelectric dominance at low energy and pair production at high energy levels. Half value layer (HVL), tenth value layer (TVL) and mean free path (MFP) increased with an increase in energy. MFP decreased with an increase of MnO content. Electron density (N_eff) decreased with an increase of energy. Equivalent atomic number (Z_eq) of the samples is found to be higher than the marbles of different colours and black granite. These results indicate that the present glasses are the suitable candidates for nuclear radiation (gamma rays) shielding at lower energy.

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Biodegradable polymers exhibit great potential to be a critical part of the global sustainability solution; however, their application areas are limited due to their inadequate properties for some applications. Although nano metal oxide powders are often used to improve the properties, they exhibit toxicity, phytotoxicity and uncontrolled agglomeration. Recently, designed, micron size, hexagonal platelet particles, which constitute fine primary particles (MicNo®), have been manufactured to exploit advantages of both micron and nano size, while abating the adverse effects of nanoparticles. Accordingly, the research goal of this study was to appraise effects of MicNo® ZnO and Ag-doped MicNo® ZnO particles on structure development and hence properties of chitosan/PVA films. The results show that MicNo® particles improve UV-resistance, mechanical and antibacterial properties of the films much more effectively with respect to nanoparticles due to their novel morphology and demonstrate great potential as new generation additive systems for biodegradable polymers to extend their application areas.

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This in vitro study aimed to evaluate shear bond strength (SBS) between CAD/CAM blocks with different compositions and orthodontic metal brackets, following various surface treatments and bonding procedure. Specimens were prepared from Vita Enamic, CeraSmart, Tetric CAD and Vita Mark II CAD/CAM blocks and were subjected to thermocycling for 5000 cycles. Then, the specimens were allocated into 6 groups according to the surface treatment (n = 12): control (no surface treatment); hydrofluoric acid etching (HF); air-borne particle abrasion with aluminium-oxide; tribochemical silica coating; bur abrasion; and Monobond Etch and Prime application (MEP). The surface morphology of the CAD/CAM blocks was characterized using scanning electron microscope. Then, specimens were silanized and brackets were bonded with adhesive resin. After thermocycling, the SBS test was performed until failure, and failure types were noted according to the adhesive remnant index (ARI). Data were analysed using two-way ANOVA and Tukey tests to perform pairwise analyses. The significance level was taken as α = 0.05. Both the CAD/CAM block type and the surface treatment significantly influenced SBS. Control groups of all CAD/CAM blocks demonstrated significantly the lowest SBS values. The highest SBS values were observed for Vita Mark II specimens treated with HF among all groups. Control groups showed exclusively ARI score 5, whereas surface treated groups had lower and similar scores. All groups, except the control, had reliable SBS values (above 6 MPa). Therefore, clinicians can use MEP, novel self-etching single-component ceramic primer, safely besides other surface treatments while bonding orthodontic brackets.

Drug delivery systems are systems that reduce the dose of a drug, extend the dosing interval, eliminate side effects, and ensure that the drug reaches the target tissue in a safe, controlled, and effective manner. Hydroxyapatite (HAP) is an inorganic material based on calcium phosphate and is an effective adsorbent with excellent biocompatibility and bioactivity due to its similarity to the mineral components of human bone. In this study, the adsorption and desorption behaviors of acetylsalicylic acid (ASA) from aqueous solutions were investigated on template-modified hydroxyapatite. Hydroxyapatite (HAP) was synthesized by the chemical precipitation method and modified with various templates such as cetyltrimethylammonium bromide (CTAB), Pluronic® P-123 (P123), and Pluronic® F-127 (F127). X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were used to characterize the synthesized HAP samples. Equilibrium adsorption isotherms and kinetics for ASA-HAP adsorption were studied and best represented by the Langmuir isotherm. The results suggest that HAP is suitable as an alternative carrier for the adsorption and controlled release of ASA. Maximum ASA loading conditions were selected as 35 °C, 60 min. 0.5 mg/mL ASA solution, and 3 mg adsorbent. The adsorption capacity of HAP was improved from 237.02 mg g⁻¹ to 280.27 mg g⁻¹ using CTAB as a template. The release amount was decreased from 82.99 to 68.03% in the modified samples of HAP and exhibits a more controlled release profile than the untreated samples of HAP.

Radiation is now used extensively for a variety of industrial, agricultural, and radiation therapy objectives, as well as other uses, thanks to the advancement of technology. Due to the destructive effects of radiation, radiation protection is so necessary. Although lead and lead-based composites are conventional materials for radiation shielding, their toxic nature restricted the use of them as proper shields. Therefore, the shielding properties of a series of lead-free relaxor ceramics, namely (1 − x)K_0.5Na_0.5NbO₃–xLa(Mn0.5Ni0.5)O₃ ceramics are investigated in this study. In order to obtain the neutron and gamma-ray shielding characteristics, the linear attenuation coefficient (LAC, cm⁻¹) and related parameters for (1 − x)K_0.5Na_0.5NbO₃–xLa(Mn_0.5Ni_0.5)O₃ (where x = 0.01, 0.05, 0.07, 0.10, 0.15, and 0.20) ceramic are estimated (abbreviated as (1 − x)KNN–xLMN)). Using FLUKA simulating code and Phy-X:PSD software, the shielding performance of neutrons and gamma rays is evaluated for wide energy ranges. Findings show that the S6 sample possesses the lowest mean free path (MFP) and half value layer (HVL), while the S1 sample owns the highest MFP and HVL. At an energy range between 0.001 and 0.1 MeV, sudden jumps are observed for Z_eff and N_eff graphs, which may be due to the K-edge absorption of elements such as K, Na, Nb, La, Mn, and Ni. Moreover, the fast neutron removal cross-section (FNRCS) varies between 0.060 and 0.106 cm⁻¹ from the S1 to S6 samples.

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