Development Of Crystalline Phase Research Articles

Crystalline structure and phase development in ZrxTi1-xO2 (x=0.9–0.2) ceramic nanofibers from electrospun precursors

Nanofibrous ZrxTi1-xO2 (x = 0.9–0.2) ceramic materials were produced using a high-yield, free surface alternating field electrospinning (AFES) process (a.k.a. AC-electrospinning) from metal alkoxide precursor solutions. Depending on the precursor composition, the production rates of 4.8–6.4 g/h in terms of the resulting ceramic nanofibers were demonstrated with a single-electrode AFES system. The average diameter of ZrxTi1-xO2 fibers varied in the range of 190–435 nm, depending on the alkoxide/polymer mass ratio in the precursor and annealing temperature. Zr/Ti molar ratio is a key factor that determines the crystallization temperature and phase composition of ZrxTi1-xO2 nanofibers after thermal processing between 600 and 1200 °C, but it has a moderate effect on textural properties of the resulting nanofibers. When the molar fraction of zirconia is > 0.7, the nanofibers are composed primarily of a nanocrystalline titania-rich TiO2–ZrO2 solid solution without the formation of separate TiO2 phase. At zirconia molar fraction of 0.5, stable orthorhombic Zr0.5Ti0.5O2 zirconium titanate structure forms above 680 °C. TiO2 (anatase or rutile) forms as a separate phase in addition to ZrxTi1-xO2 phases when Zr molar fraction is 0.2, depending on the annealing temperature. The results of this study demonstrate that a large variety of nanofibrous ZrO2–TiO2 ceramic materials with tailored compositions can be efficiently prepared for targeted applications by using free-surface AFES and appropriate thermal processing.

Characterization, thermal behaviour and firing properties of clay materials from Cap Bon Basin, north-east Tunisia, for ceramic applications

AbstractThis study focuses on the characterization, thermal behaviour and firing properties of clays from Cap Bon Basin, Tunisia. Chemical (inductively coupled plasma atomic emission spectroscopy) and mineralogical (X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy) characterization of the clays was carried out. Physical properties were identified using particle-size distribution and Atterberg limits tests. Differential thermal analysis/thermogravimetry, dilatometry, XRD and FTIR analyses were conducted to assess the thermal behaviour, transformations and crystalline phase development during firing. The clays studied show large proportions of silt and clay fractions. They are rich in SiO2, Al2O3 and Fe2O3 and mostly consist of illite, kaolinite, smectite and minor mixed-layer illite-smectite. Associated minerals are mainly quartz, calcite and feldspar. To monitor the firing properties, three clay mixtures referred to as M1, M2 and M3 were prepared according to the physicochemical and mineralogical characteristics of the raw clays. These were sintered at 900°C, 1000°C and 1100°C and tested for firing shrinkage, flexural strength and water absorption. As a result, various mineralogical transformations occurred at 900–1100°C associated with the crystallization of new phases. The main transformations identified at >1000°C resulted in the formation of anorthite and mullite, causing significant densification of the fired ceramic materials. Sintering at 1100°C increased the densification and thus improved the flexural strength. At this temperature, the sintered ceramic tiles exhibited excellent properties, namely water absorption of 2–3% and flexural strength of 30–41 MPa, indicating that these studied clays might be used as raw materials for the production of stoneware tile ceramics.

La0.75Sr0.25Cr0.5Mn0.5O3 perovskite developed for supercapacitor applications

This study reports effect of pH of precursor solution on structure, morphology, and electrochemical properties of La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) perovskite which is a potential electrode material for supercapacitors. Nanopowder of LSCM was synthesized using metal nitrates and citric acid by solution-combustion method. Development of crystalline phase in as-synthesized powder after calcination was monitored by X-ray diffraction. Particle sizes of as-synthesized powders were analysed by transmission electron microscopy. Synthesized active material (LSCM) along with carbon black and polyvinylidene fluoride was coated on porous Ni foams by vacuum centrifuge mixing to prepare electrodes. Electrochemical characterization of the electrodes was carried out by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge discharge (GCD) in 3 M KOH using saturated calomel electrode as reference electrode. These tests revealed that the electrodes prepared from LSCM powder synthesized at pH 4 (LSCM-(pH4)) displayed the highest specific capacitance of 751 F/g at 1 mV/s and an Aerial capacitance of 2.9 F/cm2 with ca. 5 mg mass loading of the active material. LSCM-(pH4) showed the lowest charge transfer resistance as determined by EIS and 79 % charge retention after 5000 CV cycles at 50 mV/s. Furthermore, LSCM-(pH4) electrodes were tested using Hg/HgO as reference electrode which showed stability of electrodes in a wider potential window of about 0.8 V. LSCM-(pH4) electrode showed maximum SC of 752 F/g at 1 mV/s. Symmetric supercapacitor developed with LSCM (pH4) displayed SC of 179 F/g at 1 mV/s and charge retention of ca. 92 %.

Immobilization of crystalline Fe2O3 nanoparticles over SiO2 for creating an active and stable catalyst: A demand for high temperature sulfuric acid decomposition

To address the issues of catalytic activity and stability of the promising Fe2O3/SiO2 catalyst for sulfuric acid decomposition, Fe2O3 was immobilized on SiO2 support by polyol, solvothermal and wet-impregnation methods and examined. The different methods yielded catalysts with varying crystal structure, porosity, morphology and redox properties which were investigated by XRD, Mössbauer spectroscopy, N2-BET surface area, SAXS, ED-XRF, HR-TEM, TPR/O and XPS techniques. The effect of the properties on the activity and stability was evaluated in a fixed-bed reactor and a structure-activity correlation was established. Above 750 °C the catalytic activity followed the order polyol > wet impregnation ∼ solvothermal. Stability of the sample prepared by polyol method was ascertained by 100 h experimental run at 800 °C. The higher activity and stability of the Fe2O3/SiO2 catalyst (polyol) is ascribed to the development of crystalline α-Fe2O3 dispersed phase, higher pore confinement, better support-active phase interactions and higher degree of reduction.

Effect of heat transfer coefficient, draw ratio, and die exit temperature on the production of flat polypropylene membranes

In this work, a stable numerical scheme has been developed for the 1.5-dimensional film casting model of Silagy et al. [Polym. Eng. Sci. 36, “Study of the stability of the film casting process,” 2614–2625 (1996)] utilizing the viscoelastic modified Leonov model as the constitutive equation and energy equation coupled with the crystallization kinetics of semicrystalline polymers taking into account actual temperature as well as cooling rate. The model has been successfully validated on the experimental data for linear isotactic polypropylene taken from the open literature. Drawing distance, draw ratio, heat transfer coefficient, and die exit melt temperature were systematically varied in the utilized model in order to understand the role of process conditions in the neck-in phenomenon (unwanted film width shrinkage during stretching in the post die area) and crystalline phase development during flat film production. It is believed that the utilized numerical model together with the suggested stable numerical scheme as well as obtained research results can help to understand a processing window for the production of flat porous membranes from linear polypropylene considerably.

PZT/PZT and PZT/BiT Composite Piezo-Sensors in Aerospace SHM Applications: Photochemical Metal Organic + Infiltration Deposition and Characterization.

The composition of fine-ground lead zirconate-titanate powder Pb(Zr0.52Ti0.48)O3, suspended in PZT and bismuth titanate (BiT) solutions, is deposited on the curved surface of IN718 and IN738 nickel-based supper alloy substrates up to 100 µm thickness. Photochemical metal organic and infiltration techniques are implemented to produce smooth, semi-dense, and crack-free random orientated thick piezoelectric films as piezo-sensors, free of any dopants or thickening polymers. Every single layer of the deposited films is heated at 200 °C with 10 wt.% excess PbO, irradiated by ultraviolet lamp (365 nm, 6 watt) for 10 min, pyrolyzed at 400 °C, and subsequently annealed at 700 °C for one hour. This process is repeated successively until reaching the desired thickness. Au and Pt thin films are deposited as the bottom and top electrodes using evaporation and sputtering methods, respectively. PZT/PZT and PZT/BiT composite films are then characterized and compared to similar PZT and BiT thick films deposited on the similar substrates. The effect of the composition and deposition process is also investigated on the crystalline phase development and microstructure morphology as well as the dielectric, ferroelectric, and piezoelectric properties of piezo-films. The maximum remnant polarization of Pr = 22.37 ± 0.01, 30.01 ± 0.01 µC/cm2, the permittivity of εr = 298 ± 3, 566 ± 5, and piezoelectric charge coefficient of d33 = 126, 148 m/V were measured versus the minimum coercive field of Ec = 50, 20 kV/cm for the PZT/PZT and PZT/BiT thick films, respectively. The thick film piezo-sensors are developed to be potentially used at frequency bandwidth of 1–5 MHz for rotary structural health monitoring and also in other industrial or medical applications as a transceiver.

Structural and optical investigations of Nd3+doped Y2O3-SiO2 nanopowder

The present investigation deals with the synthesis of Nd3+ doped Y2O3:SiO2 nanopowder around moderate annealing temperatures (450 °C & 850 °C) using sol gel technique. The X-ray diffraction technique was used for phase identification, structural analysis and grain size determination. FTIR spectra of the prepared powder were taken at room temperature in the range 400–4000 cm−1. The morphology of nanoparticles and particle size was confirmed by Transmission Electron Microscope. From structural investigations, initial development of crystalline phase of yttium oxide was obtained in sample S2 annealed at 450 °C. While in sample S3 due to high annealing temperature (850 °C), agglomeration occurred. In this agglomerated sample temperature quenching results thus suppress the luminescence. Therefore, we have reported the optical investigations of sample S2 only. It is also demonstrated that the addition of SiO2 as sintering agent could improve both the optical and structural properties.The optical absorption spectrum has been observed in the 200–600 nm range. The absorption spectrum of Nd3+ doped Y2O3-SiO2 powder depicts absorption edge in ultra-violet region (310 nm) with prominent peaks of neodymium ion (808 nm) in IR region. The band edge absorption wavelength has been used to estimate the band-gap energy of the prepared nanocomposite by Tauc's plot. The emission spectrum has been obtained using two different excitation wavelength (λex = 310 & 808 nm) in UV and NIR regions, respectively. Using λex = 310 nm, strong emission bands have observed in 500–600 nm correspond to Si-O/Y-O or may be due to composite formation. However, the photoluminescence emission corresponding to λex = 808 nm have been centered at 890, 1042 and 1275 nm was attributed to neodymium ion. The structural and optical investigations of Nd3+ doped Y2O3:SiO2 is of basic importance for better utilization of such nanopowder in the fabrication of photonic devices, catalytic systems, solid state lasers, opto-and micro-electronics, nanophosphours and optical fiber amplifiers etc.

Phase transition mechanisms involved in the formation of structurally stable β-Ca3(PO4)2-α-Al2O3 composites

Composite powders comprising various proportions of β-Tricalcium phosphate [β-Ca3(PO4)2] and α-Alumina (α-Al2O3) were synthesized by wet precipitation and then heat treated for drying and crystalline phase development. The phase formation mechanism was assessed through a set of characterization techniques including XRD, FT-IR and Raman spectra, and quantitative Rietveld refinement analysis. Al2O3 additions delayed the transformation kinetics from calcium deficient apatite to β-Ca3(PO4)2 and preserved the thermal stability of β-Ca3(PO4)2−α-Al2O3 composites till 1400°C. Such enhancement of thermal stability was due to the occupancy of Al3+ at both Ca2+(4) and Ca2+(5) lattice sites of β-Ca3(PO4)2. Beyond the occupancy saturation limit for Al3+, the excess of aluminium crystallized as α-Al2O3. Morphological analysis revealed the growth of rod-like α-Al2O3 platelets on the surface of micron sized β-Ca3(PO4)2 grains. The mechanical data obtained from indentation of bulk composites displayed enhanced hardness and Young’s modulus with increasing α-Al2O3 content in the composites.

The Effects of Water Addition on the Color and Crystalline Phase of Y2O3 Coatings Fabricated by Plasma Suspension Spray

The effects of water addition on Y₂O₃ coatings or thick films prepared by plasma suspension spray (SPS) have been investigated. Water addition in suspension media was found to be effective to control the color of a Y₂O₃ coating prepared by SPS. The color changed with water addition at the shortest stand-off distance of 50 mm even if samples had the same crystalline phase. Change was not correlated with fragmentation behavior of liquid suspension inside the plasma jet. Water content over 50 vol% was found to produce unmelted particles, indicating that water suppressed heat transfer to the particles. However, plasma jet temperature was not affected. Instead, the coating fabricated with water addition has higher oxygen and lower carbon content compared to these characteristics of the coating without water addition. This was attributed to the retarded complete evaporation of liquid media from the suspension droplet, resulting in inhibition of excessive heating and evaporation of the molten Y₂O₃ droplet. In this regard, crystalline phase development with respect to stand-off distance and water addition was discussed.

PREPARATION, SOLID STATE CHARACTERISATION OF PACLITAXEL AND NARINGEN COCRYSTALS WITH IMPROVED SOLUBILITY

Objective : The objective of the present study is to prepare a better form of paclitaxel cocrystal with improved solubility. Paclitaxel (PTX) is a class-4 drug; this drug has low aqueous solubility and high affinity for P-gp. Available formulation are IV based and using our research work with advantages of co-crystal technology towards the enhancement of paclitaxel solubility and thereby its bioavailability (1) and also to improve the patient compliance. Methods: Naringen was selected based on their chemical nature and its ability to inhibit P-gp, solvent assisted grinding method used to prepare the cocrystals, and prepared cocrystals were subjected to solid state characterization to determine the crystal structure of the cocrystals, as this can provide significant new insights into how the drug and coformer interact, and thereby provide an excellent crystal engineering guide to new cocrystals, potentially with improved properties. Instruments like Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry, X-ray powder diffraction will be used to determine their stability and any phase transformations (including decomposition) which they might undergo as a function of temperature. Results : Principle involved in the formation of cocrystal is hydrogen bonding between C=O and N-H group of drug and COOH groups of coformers, which is confirmed by FTIR data and DSC experiments were carried out to study the melting point and heat of enthalpy of the cocrystals. Results clearly shows that the melting point of the cocrystals was increased which confirms the formation of cocrystals. The drug and formation of cocrystals are explained by the X-ray powder diffraction patterns. The PXRD patterns of the pure drug showed sharp, well-defined peaks(spectrum attached) and cocrystals PXRD patterns shows that there is a significant difference in the entire diffraction pattern, changes in peak locations with respect to pure drug indicates a change in the arrangement of molecules, hence confirms the development of new crystalline phase. Conclusion: The results obtained from the above experiments clearly shows the formation of cocrystals with improved solubility.

Reversible phase–structure modification of photostructurable glass ceramic by CO2 laser irradiation

Structural changes and phase transformations of the photostructurable glass (PhG) surfaces under the impact of 10.6-μm wavelength laser radiation are examined. The regimes initiating the formation and development of crystalline phase and its reversible (secondary) amorphization are determined. In addition, the kinetic of crystalline phase formation and its melting on the surface of PhG are investigated. The characteristics of multiple reversible phase–structure transformations in the temperature range of 470–800 °C are investigated.

Comparative Influence of Surface Tungstate Species and Bulk Amorphous WO3 Particles on the Acidity and Catalytic Activity of Tungsten Oxide Supported on Silica

Catalysts based on tungsten oxide supported on silica and containing up to 2.5 W atoms nm–2 were studied for the purpose of establishing quantitative relationships between the nature and abundance of surface species, acidity, and catalytic activity. Synthesis conditions that maximize the formation of amorphous WO3 were adopted to assess its influence on the overall acidity and activity. The results were compared to those of conventionally prepared catalysts. The catalysts’ structure was characterized by FTIR, Raman, and UV spectroscopies. The acidity of the solids was monitored by adsorption of 2,6-dimethylpyridine followed by FTIR, and their catalytic activity was tested for the reaction of propan-2-ol dehydration. A methodology for quantitation of W species (WOx surface species, amorphous or crystalline WO3 particles) detected following calcination at 673 or 773 K was developed. For both calcination temperatures, surface W species were first formed with initial W addition. Their abundance increased with increasing W content up to ca. 0.7 atom W nm–2 and levels off for higher W surface densities. The leveling off was concomitant with the detection and rapid development of amorphous or crystalline WO3 phase (catalysts calcined respectively at 673 or 773 K). The comparison of W speciation in both series indicated that amorphous WO3 phase is quantitatively transformed to crystalline WO3 on increasing the calcination temperature from 673 to 773 K. The observed development of Brønsted acidity of the solids was associated with W deposition. The abundance of these acid sites correlated directly with the catalytic activity. The study of structure–activity relationship showed that all W species were active. Modeling of the results permitted an estimation of the intrinsic activity of each W species. The values thus obtained suggest that amorphous WO3 particles exhibit the highest activity per surface W atom.

Selective Magnetic Evolution of MnxFe1–xO Nanoplates

Iron–manganese oxide (MnxFe1–xO) nanoplates were prepared by the thermal decomposition method. Irregular development of crystalline phases was observed with the increase of annealing temperature. Magnetic properties are in accordance with their respective crystalline phases, and the selective magnetic evolution from their rich magnetism of MnxFe1–xO and MnFe2O4 is achieved by controlling the annealing conditions. Rock-salt structure of MnxFe1–xO (space group Fm3m) is observed in as-synthesized nanoplates, while MnFe2O4 and MnxFe1–xO with significant magnetic interactions between them are observed at 380 °C. In nanoplates annealed at 450 °C, soft ferrites of Mn0.48Fe2.52O4 with MnxFe1–xO are observed. It is assumed that the differential and early development of crystalline phase of MnxFe1–xO and the inhomogeneous cation mixing between Mn and Fe cause this rather extraordinary magnetic development. In particular, the prone nature of divalent metal oxides to cation vacancy and the prolonged annealing time o...

Spark Plasma Sintering (SPS) to the Mullite –Zirconia Ceramics Development

This research is devoted on the investigation of effect of SPS (spark plasma sintering) by comparing with the conventional sintering on the mullite-ZrO2 ceramics development. Mullite-ZrO2 ceramics was produced from different time ball-milled powders. The effect of illite nanoparticles to one part of powder was investigated to promote the sintering process. The density and compressive strength as well as microstructure and crystalline phase development of ceramics were used to show the impact of SPS by comparing with conventional sintering. It was shown that sintered at 12500C by SPS samples achieved densities for up to 1.6-2.2 times times higher as by conventional sintering at 13000C. Together the compressive strength and Vicker's microhardness correlate with the changing of density. The microstructure of the SPS samples is dense and is formed from good textured mullite and cubic ZrO2 particles, but by conventionally sintered – there are formed mullite-corundum crystals with inclusion of tetragonal ZrO2. illite clay additive is effective on density and compressive strength increase only for conventionally sintered samples, but not for SPS. DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5501

Mullite-based cellular ceramics obtained by a combination of direct foaming and reaction bonding

Mullite-based cellular ceramics were prepared via the polymer precursor route using poly(silsesquioxane) in combination with particulate alumina or alumina/aluminum mixtures. The multi-functional preceramic polymer was used as pore-forming agent by employing a self-foaming process during the polymer cross-linking step, as well as a precursor for reactive silica, one of the reagents in mullite formation. The size of filler particulates was found to strongly affect foaming of the polymer/filler mixtures, with coarser particles facilitating an improved foaming performance. Thermal conversion in air at 1600°C resulted in the formation of cellular ceramics with high mullite contents. The partial substitution of alumina with aluminum in the initial mixtures resulted in improved mechanical properties at comparable porosities, resulting in compressive strengths of 0.3MPa at total porosities of 93%. A correlation between thermal analysis data and crystalline phase development during the thermal treatment allowed for the clarification of processes taking place during heat treatment, yielding information for a future process optimization approaches.

Thickness and thermal processing contribution on piezoelectric characteristics of Pb(Zr-Ti)O3 thick films deposited on curved IN738 using sol–gel technique

Lead zirconate-titanate (PZT) thick films of perovskite structure Pb(ZrxTi1-x)O3 were fabricated on the curved surface of IN738 nickel-based supper alloy substrate up to 15 µm thickness using sol–gel deposition technique without polyvinylpyrrolidone. The films were heated at 200℃ with 10 wt% excess PbO, pyrolyzed at 400℃, and subsequently annealed at 650℃, 700℃, and 800℃. Au and Pt thin films were deposited as bottom and top electrodes, respectively. PZT films of different thicknesses and thermal treatment conditions were characterized to investigate the effect of process on crystalline phase development, orientation, and microstructure morphology. Thereby, formation of fairly smooth, semi-dense, and crack-free random orientated thick films as well as an increase in the average grain size and stress relaxation was observed as the film thickness increased. Having optimized the coating process, intrinsic and extrinsic dielectric, ferroelectric and piezoelectric properties were measured as a function of the film thickness, orientation, grain size, and domain wall motions to evaluate the remnant polarization ( Pr = 7.6–17.5 µC/cm2), coercive field ( Ec = 2.5–4 kV/cm), permittivity ( ɛr = 276–326), dielectric loss (tan δ(%) = 2.7–3), and piezoelectric charge coefficient ( d33 = 71–145 pm/V) of the PZT thick films prepared potentially to be used as high bandwidth 1–5 MHz structural health monitoring transducers.

Use of SHS in Metal and Oxidizing Agent Dry Powder Mixes

Results are given for development of crystalline α-Al2O3 phase, crystal dimensions, degree of corundum phase crystallization microstructure, powder specific surface, and particle size distribution, obtained in the course of combustion of components in dry mixes using aluminum powder and different oxidizing agents. Aluminum powder combustion in the presence of oxidizing agents in the field from potassium nitrate to potassium perchlorate facilitates formation of broader, crystalline, and simultaneously intense diffraction maxima for α-Al2O3 phase. This is reflected in smaller crystal sizes and degree of corundum phase crystallization. Development of powder microstructure is governed by densely sintered particles, consisting of soft and hard agglomerates. It is relatively porous in the course of combustion with participation of strong oxidizing agents. This shows up as a less developed specific powder surface and wider particle size distribution, located in a field of coarse fractions in the range 5 – 54 μm, in contrast to powder prepared using potassium nitrate, whose particle sizes are located in the range 0.5 – 1.2 μm.

Molybdenum effect on the structure of SiO2–CaO–P2O5 bioactive xerogels and on their interface processes with simulated biofluids

AbstractThe study is focused on synthesis, investigation of the structural and morphological changes induced by MoO3 addition, and thermal treatment, as well as in vitro characterization of a new sol–gel derived SiO2–CaO–P2O5 bioactive materials. The obtained systems are composite materials consisting of nanocrystalline apatite, bioactive glass and CaMoO4 nanoparticles, which are of interest for both regenerative medicine and specific medical applications of the releasable molybdenum ions. The changes induced by the thermal treatments and MoO3 addition with respect to the structure and morphology were completed using differential thermal analysis\thermogravimetric analysis, X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance, and Brunauer–Emmett–Teller. The biological performance of these materials was evaluated in vitro by performing bioactivity and biocompatibility tests. The bioactive properties in terms of hydroxyapatite layer formation on the biomaterial surface after simulated body fluid immersion were studied by XRD and SEM. To establish their biocompatibility, the biomaterials surface was functionalized with protein and the resulted sample was investigated using SEM, FTIR, and XPS. The obtained results suggest that the addition of molybdenum oxide in proper concentration improves the biocompatibility in terms of enhancement of protein adherence on Si–Ca–P surface due to CaMoO4 crystalline phase development and does not inhibit bioactivity. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3177–3185, 2014.

Molybdenum effect on the structure of SiO2-CaO-P2O5bioactive xerogels and on their interface processes with simulated biofluids

The study is focused on synthesis, investigation of the structural and morphological changes induced by MoO3 addition, and thermal treatment, as well as in vitro characterization of a new sol–gel derived SiO2–CaO–P2O5 bioactive materials. The obtained systems are composite materials consisting of nanocrystalline apatite, bioactive glass and CaMoO4 nanoparticles, which are of interest for both regenerative medicine and specific medical applications of the releasable molybdenum ions. The changes induced by the thermal treatments and MoO3 addition with respect to the structure and morphology were completed using differential thermal analysis\thermogravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance, and Brunauer–Emmett–Teller. The biological performance of these materials was evaluated in vitro by performing bioactivity and biocompatibility tests. The bioactive properties in terms of hydroxyapatite layer formation on the biomaterial surface after simulated body fluid immersion were studied by XRD and SEM. To establish their biocompatibility, the biomaterials surface was functionalized with protein and the resulted sample was investigated using SEM, FTIR, and XPS. The obtained results suggest that the addition of molybdenum oxide in proper concentration improves the biocompatibility in terms of enhancement of protein adherence on Si–Ca–P surface due to CaMoO4 crystalline phase development and does not inhibit bioactivity. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3177–3185, 2014.

Characteristics of Nano-Sized Yttria Powder Synthesized by a Polyvinyl Alcohol Solution Route at Low Temperature

Nano-sized yttria (Y2O3) powders were successfully synthesized at a low temperature of 400 degrees C by a simple polymer solution route. PVA polymer, as an organic carrier, contributed to an atom-scale homogeneous precursor gel and it resulted in fully crystallized, nano-sized yttria powder with high specific surface area through the low temperature calcination. In this process, the content of PVA, calcination temperature and heating time affected the microstructure and crystallization behavior of the powders. The development of crystalline phase and the final particle size were strongly dependant on the oxidation reaction from the polymer burn-out step and the PVA content. In this paper, the PVA solution technique for the fabrication of nano-sized yttria powders is introduced. The effects of PVA content and holding time on the powder morphology and powder specific surface area are also studied. The characterization of the synthesized powders is examined by using XRD, DTA/TG, SEM, TEM and nitrogen gas adsorption. The yttria powder synthesized from the PVA content of 3:1 ratio and calcined at 400 degrees C had a crystallite size of about 20 nm or less with a high surface areas of 93.95-120.76 m2 g(-1).