فهرست مطالب

Advanced Ceramics Progress - Volume:6 Issue: 2, 2020
  • Volume:6 Issue: 2, 2020
  • تاریخ انتشار: 1399/04/30
  • تعداد عناوین: 6
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  • L. Farahinia, M. Rezvani *, M. Rezazadeh Pages 1-6
    Amorphous semiconductors are materials with a brilliant prospect for a wide range of optical applications like solar cells, optical sensors, optical devices, and memories. The purpose of the present research was to study the semiconducting optical properties of SiO2-Al2O3-CaF2 and SiO2-Al2O3-BaF2 oxyfluoride glassy systems, which has been rarely studied from this point of view. The suitable compositions in the mentioned systems were chosen and melted in covered alumina crucibles at 1450˚C. Afterward, preheated stainless steel molds were used to shape the molten glasses. The absence of any crystallization peak in the XRD results indicated that the samples were amorphous. DTA patterns showed that the crystallization temperature of the fluoride phase is 693˚C for the glass containing BaF2 (SAB), which is higher than the peak temperature (684˚C) for the glass with CaF2 (SAC). DTA results were in accordance with density measurements, i. e., the density of the glass SAB (3.85 g.cm-3) was higher than the glass SAC (2.70g.cm-3). That is to say, BaF2 presented a more continuous structure with lower amounts of dangling bonds. According to the UV- Vis spectra, sample SAB had higher absorption and smaller bandgap of the glass SAB (with a direct bandgap of 2.90 eV and indirect bandgap of 3.40 eV) indicated that it has better semiconducting behavior than sample SAC (with a direct bandgap of 3.07 eV and indirect bandgap of 3.60 eV). This increment of the semiconducting behavior is attributed to the more continuous structure of the glass SAB. Urbach energy, which is an indicator of disorder degree of structure, was 0.20 and 0.32eV for SAB and SAC, respectively. Therefore, the lower Urbach energy of SAB glass confirmed the higher structure order of it.
    Keywords: Bandgap, Semiconductor Glass, Oxyfluoride
  • S. M. Nahvi * Pages 7-16
    The purpose of this research was to investigate the abrasive wear behavior of WC–NiMoCrFeCo (WC-N) and WC–FeCrAl (WC-F) coatings deposited by high-velocity oxygen fuel (HVOF) spraying. The abrasive wear resistance was evaluated by a dry sand rubber wheel (DSRW) test rig using abrasives silica 70 and alumina 60, and the values were then compared to those of conventional WC-Co (WC-C) coatings. The abrasive wear with silica 70 indicated the “soft abrasion” regime, while alumina 60 abrasive caused a “hard abrasion” for all coatings. Moreover, the wear rate of the coatings abraded by alumina 60 was around 1.2-7.8 times greater than that of silica 70. WC-F exhibited the greatest wear resistance compared to other coatings tested by silica 70 due to its lower mean free path and higher hardness compared to other coatings. WC-C coating revealed the cobalt matrix removal followed by WC fracture and pullout using abrasive silica 70, while WC-F and WC-N coatings represented a combination of subsurface cracking, WC pullout, and fracture. Abraded by alumina 60, WC-C, WC-F, and WC-N coatings showed the evidence of grooving, pitting, and cutting. Moreover, WC-C coating had the highest wear resistance due to its high fracture toughness and low porosity, protecting WC-C coating against severe cracking and grooving, respectively. Cross-sectional images of the wear scars revealed a significant sub-surface cracking for WC-F and WC-N coatings while no significant cracking could be detected for WC-C coating.
    Keywords: abrasive wear, WC–FeCrAl, WC–NiMoCrFeCo, HVOF
  • N. Rahimi, V. Dalouji *, A. Souri Pages 17-23
    In this paper, CAZO and CZO thin films were deposited on quartz substrates by radio frequency magnetic sputtering and annealed at different temperatures of 400, 500, and 600°C. One of the most structural studies of thin-film materials is the analysis of the results that are obtained from AFM images. The most variations in optical density of CZO and CAZO thin films were at energy points to about 3eV and 4eV, respectively. Fractal dimensions and structural properties of films, as well as the optical density of CZO and CAZO thin films, were investigated. The AFM images were used to estimate the lateral size of the nanoparticles on the surface of the films. Annealed films at 500°Chad the maximum values for the lateral size of the nanoparticles. These values for the as-deposited films and annealed films at different temperatures of 400, 500, and 600°C were about 7.9,8.1, 6.5, and 7.75nm for CZO thin films, respectively. In addition, the lateral size of CAZO thin films was about 6.8, 6.27, 6.04, and 6.71, respectively. Films that annealed at 500°Chad the minimum value of fractal dimensions. The power spectral density of all films reflects the inverse power low variations, especially in the high spatial frequency region, indicating the presence of fractal components in prominent topographies. The maximum variations in the bearing area were as much as 0.015μm and 0.01μm for CZO thin films and CAZO thin films, respectively.
    Keywords: The CAZO Thin Films, Fractal dimensions, Topography, Optical Density, Bearing Area
  • R. Hayati *, M. A. Razavian Pages 24-29
    Lead-free (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 piezoceramics with nano SiO2 additive were prepared by conventional solid oxide sintering method. The samples were fabricated by means of cold isostatic pressing and sintering was performed at 1350 °C for 4 h in the air. The phase structure and microstructure were studied via X-ray diffraction technique and field emission scanning electron microscopy. The room-temperature dielectric properties and the variations in the temperature ranging from 23 to 160 °C were measured using a high-precision LCR meter. The mechanical properties such as Vickers hardness and compressive strength were investigated. The obtained results showed that nano SiO2 addition produced dense and uniform microstructures with larger grains than pure BCZT. The Curie temperature of undoped BCZT increased to about 25 °C through the incorporation of 0.75 mol% SiO2 and then, the mechanical properties considerably improved. Accordingly, BCZT piezoceramic with nano SiO2 additive enjoys viable properties, which makes it widely applicable.
    Keywords: Piezoceramic, (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3, Nano SiO2, Dielectric, Mechanical Property
  • M. Hosseinifard *, H. Goldooz, A. Badiei, A. Kazemzadeh Pages 30-34
    Y3A5O12:Cr3+ nanophosphor was synthesized by cathodic electrodeposition method. During the preparation procedure, hydroxide precursors were deposited on the surface of cathode via electrochemical reaction and then the final product was achieved by heat treatment of obtained powder at 1100 °C for 4 h. The structure and properties of the obtained product were investigated by various analysis methods such as X-Ray Diffraction (XRD), Fourier Transform InfraRed (FTIR) Spectroscopy, Photoluminescence Spectroscopy (PL), Scanning Electron Microscopy (SEM) and N2 adsorption-desorption analysis. The XRD patterns of the synthesized YAG: Cr product, were in good match with the pure Y3Al5O12 phase and the absence of any other impurities indicates the transformation of Cr3+ ions into the host matrix (YAG). In the emission spectrum of prepared material, a broad emission containing four pronounced bands at 685, 695, 710 and 725 nm was observed that indicates the presence of Cr3+ ions in the final product and further confirmed the formation of desired oxide product (YAG: Cr). The results of our studies showed that cathodic electrodeposition is a practical and highly efficient method for preparation of Y3A5O12:Cr3+ nanophosphor compound.
    Keywords: YAG: Cr, Hydroxide precursors, Electrodeposition, Emission
  • Synthesis of FAp, Forsterite, and FAp/Forsterite Nanocomposites by Sol-gel Method
    S. Manafi *, F. Mirjalili, S. Joughehdoust Pages 35-42

    The present study aims to investigate the preparation and evaluation of phase and morphological properties of a nano biocomposite ceramic. In this regard, the synthesis of fluorapatite (FAp) as the first phase and forsterite considered as the second phase by the sol-gel method was taken into account. Then, nanocomposites with the base of fluorapatite with 15, 25, and 35 wt% of forsterite were synthesized using the sol-gel method. The synthesized nanoparticles and nanocomposites were characterized by using different techniques, Field Emission Scanning Electron Microscope (FESEM), X-Ray Powder Diffraction (XRD), and Fourier-Transform Infrared (FT-IR) Spectroscopy. X-ray diffraction test results as well as infrared spectroscopy indicated that fluorapatite, forsterite, and fluorapatite/forsterite nanocomposites were produced without impurity. FESEM result showed that the particle sizes of the produced nanocomposites with 15, 25, and 35 wt% of forsterite ranged approximately between 25 and 80 nm. The result of the MTT assay proved the nontoxicity of samples for 7 days.

    Keywords: Fluorapatite, Forsterite, Nanocomposite, Biomaterials