نشریه علم و مهندسی سرامیک
سال چهارم شماره 1 (پیاپی 12، بهار 1394)

In the present study، structural، physico-chemical and mechanical properties of pure calcium phosphate bone cement and effect of adding bioactive glass fibers (BGf) on it were evaluated. The sol-gel derived bioactive glass fibers were composed of ternary system of silicon oxide، calcium oxide and phosphorus oxide that were prepared by electrospinning method. Scanning electron microscopy (SEM) and X-ray analyses were performed to assess morphology and phase composition of fibers، respectively. Afterwards، different weight ratios of the fibers were added into the calcium sulphate cement (CS) matrix and the mechanical properties were studied. The results showed that optimum mechanical properties were related to 15% BGf reinforced CS as the compressive strength، Young’s modulus and fracture toughness were about 31/54 MPa، 965 MPa and 0/566 kJ/cm2، respectively. Initial and final setting times of the composite were 6 min and 21 min، respectively. For comparison، structural and bioactivity properties of pure CS (as a control sample) and nanocomposite were then investigated. The results showed that adding BGf into the CS matrix not only had appropriate effect on pure CS but also improved mechanical properties، apatite formation and human MG-64 cell attachment.

Among the candidate semiconductors in photovoltaic applications، CuInS2 (CIS) is under intense investigation due to its direct band gap (1. 5eV)، high absorption coefficient and good stability. One of the limiting parameters in the mass production of these solar cells is that Indium is a rare metal which has to be substituted with other metallic elements. On the other hand، the maximum photovoltaic conversion efficiency is attained on devices with the absorber bandgap energy of approximately 1-1. 3 eV. So in this study، CIS synthesis and substitution of trace element of indium with abundant element of Iron were investigated. The solid solution compounds of CuIn1-xFexS2 were synthesised using one pot Polyol route. The synthesized powders were characterized using X-ray diffraction (XRD)، Scanning electron microscopy (SEM) and Scanning tunneling Spectroscopy (STS) techniques. As the amount of Iron increases up to x=0. 15، the crystallinity of particles is inhanced and their unit cell dimensions are reduced. Further increasing of iron content results in the formation of FeS and FeS2 as impurity phases were observed with further increasing the iron content، while the crystalinity is reduced. The density of states investigation confirmed that increasing the amount of Iron resulted in enhancing the density of carriers، p-type conductivity and formation of the intermediate band in the forbidden band of host material

In this research، the effect of Fe3+ dopant on the thermal stability and physical properties of hydroxyapatite (HA) nanoparticles were investigated. Phase evolution، thermal stability، morphology and magnetic properties of synthesized HA nanoparticle were characterized by X-ray diffraction (XRD)، Fourier transform infrared spectroscopy (FT-IR)، field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). The results showed substitutionFe3+ions in the HA crystal structure lead to decrement crystallinity and thermal stability of HA. Nanoparticles of HA without Fe ion will be stable up to 900C while HA nanoparticles containing 9% Fe ion is stable up to 700C. VSM results were confirmed paramagnetic behavior of Fe3+ substituted HA nanoparticles.

One of the ways to increase the efficiency of solar thermal collector، create an antireflective coating on the glass surface of sun receivers. In this study، preparation of single layer، multilayer and composite silica-titania coatings for antireflective application was investigated. For investigation، Field-emission scanning electron microscope (FE-SEM)، Fourier-transformed infrared spectrophotometer (FT-IR) and UV–visible spectrophotometer was used. Results revealed، although، composite coatings don’t improve transmittance of glass substrate، but single silica-layer، tree-layer and six-layer sol–gel TiO2-SiO2 coatings showedthe maximumtransmittance about 99% which isapproximately 8% higher than uncoatedglass. The transmittance increased due tothe application ofcoatingswithgoodrefraction indices anddesirablelayer structures onthe glass surface. Theeconomicantireflectivecoatingsfor solar collectorswillhelptogenerate moreelectricity.

Spark Plasma Sintering (SPS) is a new technique which was used for sintering of Ultra High Temperature Ceramics (UHTCs) recently. In this study، ZrB2-based ceramics was prepared with different HfB2 content (0، 5، 10، 15 vol%) by SPS in different temperatures، times and pressures. Microstructure evaluation and phases were done by SEM and EDAX. Effect of SPS conditions (temperature، time and pressure) on microstructure was investigated. The results showed that Hf and Zr diffuses in each other and (Zr،Hf) B2 solid solution will be formed. In addition، it was concluded that by increasing temperature and time، solid solution formation increases. Pressure has little effect on diffusion. MoSi2 improves diffusion by liquid phase formation. Finally it is cleared that HfB2 increases open porosity percent slightly.

Bioactive glasses containing ZrO2 have radiopaque property. Radiopacity is an essential feature of bioactive materials that allows easy follow-up of the treated patient under radiographic control. In this research، we synthesized 61. 2SiO2-24. 3CaO-4P2O5-10ZrO2 (mol%) via a simple sol-gel route. The sufficient heat treatment for converting dried gels into the glasses was determined using thermo-gravimetric and differential thermal analysis (TG/DTA) and X-ray diffraction (XRD). The structure of dried gels and glasses were investigated by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Specific surface area، pore volume، pore size and pore size distribution were evaluated by N2 adsorption/desorption technique and employing multipoint Brumauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods. Differential scanning calorimetry (DSC) results were used to calculate the overall crystallization activation energy. Sol-gel process consisted of hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS)، triethyl phosphate (TEP)، Ca (NO3) 2. 4H2O and ZrO (NO3) 2. XH2O. Nitric acid was used to accelerate the hydrolysis step. The optimum H2O/TEOS+TEP ratio and nitric acid concentration were 15 and 0. 1 M، respectively. Structural analysis by NMR and FTIR revealed that glasses containing ZrO2 presents an amorphous structure in which Zr acts as a glass former and retards the crystallization of apatite. N2 absorption/desorption analysis exposed that the synthesized glasses are mesoporouse with average surface area and pore size of 133-160 m2/g and 2-4 nm، respectively. Additionally، upon adequate heat treatment at 1000 °C، the gel-glass containing ZrO2 converted into an apatite-wollastonite-zirconia glass-ceramic. Finally، ZrO2 addition increased the activation energy for apatite crystallization from 198 kJ/mol to 835 kJ/mol.

Plasticity as an important property in clay-water systems is identified as a permanent deformation with no rupture of the material under a consistent، defined، and external force greater than its critical tolerance، which remains in force even after removal or lessening the applied force. In spite of the introduction of various methods to measure the plasticity and determine the optimum water content in a clayey ceramic body، there is not a general procedure for all the ceramic bodies containing low or high plasticity materials. In this paper، physical properties of ceramic bodies consist of two raw materials، high plasticity Soravejin Bentonite (B-S) and low plasticity Zenouz clayey quartz (Z-Q) in a weight ratio of 100:0، 67:33، 33:67، and 0:100 were investigated. According to the dried strength data as a function of die-pressing pressure، an index named as “plasticity exponent” was defined in order to compare the plasticity of ceramic bodies. This new method، which can simulate actual conditions of processing and production in the wall/floor tile and pressed-ceramic factories، is an easy test route، and obtains the authentic results.