Wet Precipitation Method Research Articles

Microwave-Assisted Fabrication of Mesoporous Silica-Calcium Phosphate Composites for Dental Application.

Herein, the microwave-assisted wet precipitation method was used to obtain materials consisting of mesoporous silica (SBA-15) and calcium orthophosphates (CaP). Composites were prepared through immersion of mesoporous silica in different calcification coating solutions and then exposed to microwave radiation. The composites were characterized in terms of molecular structure, crystallinity, morphology, chemical composition, and mineralization potential by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). The application of microwave irradiation resulted in the formation of different types of calcium orthophosphates such as calcium deficient hydroxyapatite (CDHA), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP) on the SBA-15 surface, depending on the type of coating solution. The composites for which the progressive formation of hydroxyapatite during incubation in simulated body fluid was observed were further used in the production of final pharmaceutical forms: membranes, granules, and pellets. All of the obtained pharmaceutical forms preserved mineralization properties.

Radiological evaluations of low cost wollastonite nano-ceramics graft doped with iron oxide in the treatment of induced defects in canine mandible.

Wollastonite with/without maghemite [(Fe2O3), 0, 3 and 10 wt%] was prepared by facile wet precipitation method. Effect of Fe2O3 presence in the obtained nano-ceramics on physical structure, morphology, size and the mechanical features was evaluated using X-ray diffraction, transmission electron microscope, and universal testing machine. Moreover, the in vitro biomineralization was examined using simulated body fluid (SBF) by means of scanning electron microscope/energy dispersive X-ray, Fourier transform infrared, and inductively coupled plasma. An in vivo study was conducted on 24 adult male mongrel dogs to test the biosafety of fabricated samples in the reconstruction of experimentally induced mandibular bone defects. Bone density was measured through cone beam computed tomography analysis conducted at 1 and 3 months following surgery. Wollastonite was the main phase in all the prepared samples however little maghemite was developed in Fe-containing samples. No remarkable changes were recognized for physical structure of obtained microcrystalline structures, however, a decrease in particle size was noted in the existence of Fe2O3 (10-15 nm) when compared to the pure wollastonite (30-50 nm). Mechanical features were dependent on the included Fe2O3 concentration within the wollastonite ceramic matrix. The degree of biomineralization of the samples immersed in SBF was elevated with the increase in Fe2O3 percentage. Clinically, the reconstruction of bone defects was uneventful without any adverse toxic effect. Bone density was significantly increased at 1 and 3 months (p < .001) in grafted defects compared to control ones. Increasing the doping concentrations of iron oxide was associated with significant increase (p < .001) of bone density in all induced defects. Due to the impressive healing effect of current fabricated nano-ceramics, they are recommended to be utilized as low cost bone graft alternatives.

Synthesis and characterization of poly(vinyl alcohol)/chondroitin sulfate composite hydrogels containing strontium-doped hydroxyapatite as promising biomaterials.

Novel poly(vinyl alcohol)/chondroitin sulfate (PVA/CS) composite hydrogels containing hydroxyapatite (HA) or Sr-doped HA (HASr) particles were synthesized by a freeze/thaw method and characterized aiming towards biomedical applications. HA and HASr were synthesized by a wet-precipitation method and added to the composite hydrogels in fractions up to 15 wt%. Physical-chemical characterizations of particles and hydrogels included scanning electron microscopy, energy-dispersive spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetry, porosity, compressive strength/elastic modulus, swelling degree, and cell viability. Particles were irregular in shape and appeared to have narrow size variation. The thermal behavior of composite hydrogels was altered compared to the control (bare) hydrogel. All hydrogels exhibited high porosity. HA/HASr particles reduced total porosity without reducing pore size. The mechanical strength was improved as the fraction of HA or HASr was increased. HASr particles led to a faster water uptake but did not interfere with the total hydrogel swelling capacity. In cell viability essay, increased cell growth (above 120%) was observed in all groups including the control hydrogel, suggesting a bioactive effect. In conclusion, PVA/CS hydrogels containing HA or HASr particles were successfully synthesized and showed promising morphological, mechanical, and swelling properties, which are particularly required for scaffolding.

Fe/Al (hydr)oxides engineered biochar for reducing phosphorus leaching from a fertile calcareous soil

Excessive input of phosphate fertilizer into agricultural soils has caused critical environmental concerns due to high phosphorus (P) accumulation in farmland and P leaching into subsurface drainage. In this study, an Fe/Al (hydr)oxides modified biochar (FA-BC) was fabricated from corn straw via a wet-precipitation method and utilized to reduce P leaching from a fertile calcareous soil. Spectroscopic techniques demonstrated that the FA-BC exhibited a higher oxidation resistance than the raw BC due to oxide impregnation on the BC surface. The maximum Langmuir P adsorption capacities (393 and 528 mg kg−1) of the BC (4%, w/w) and FA-BC (4%, w/w) treated soils demonstrated a more efficient P adsorption capacity of the FA-BC. Application of the 2% (w/w) FA-BC also significantly reduced the leaching of total P (81.3%) from the soil column, while maintained an appropriate level of bioavailable P in the soil for sustaining plant growth. The chemical sequestration test and in-situ P k-edge XANES analyses of the FA-BC incubated soils revealed that the labile Ca–P fractions were transformed into stabilized Fe/Al–P complexes. The increased soil pH, a higher degree of soil P saturation, and intensive interaction between P and Fe/Al (hydr)oxides also contributed to the superior ability of the FA-BC amended soils towards P retention. This study provided field-relevant implications for the design and application of engineered biochar for green and sustainable improvement of agricultural soils.

Electrospun Scaffolds Containing Silver-Doped Hydroxyapatite with Antimicrobial Properties for Applications in Orthopedic and Dental Bone Surgery.

Preventing the development of osteomyelitis while enhancing bone regeneration is challenging, with relatively little progress to date in translating promising technologies to the clinic. Nanoscale hydroxyapatite (nHA) has been employed as a bone graft substitute, and recent work has shown that it may be modified with silver to introduce antimicrobial activity against known pathogens. The aim of this study was to incorporate silver-doped nHA into electrospun scaffolds for applications in bone repair. Silver-doped nHA was produced using a modified, rapid mixing, wet precipitation method at 2, 5, 10 mol.% silver. The silver-doped nHA was added at 20 wt.% to a polycaprolactone solution for electrospinning. Bacteria studies demonstrated reduced bacterial presence, with Escherichia coli and Staphylococcus aureus undetectable after 96 h of exposure. Mesenchymal stem cells (MSCs) were used to study both toxicity and osteogenicity of the scaffolds using PrestoBlue® and alkaline phosphatase (ALP) assays. Innovative silver nHA scaffolds significantly reduced E. coli and S. aureus bacterial populations while maintaining cytocompatibility with mammalian cells and enhancing the differentiation of MSCs into osteoblasts. It was concluded that silver-doped nHA containing scaffolds have the potential to act as an antimicrobial device while supporting bone tissue healing for applications in orthopedic and dental bone surgery.

Green hydrothermal synthesis of high aspect ratio wollastonite nanofibers: Effects of reaction medium, temperature and time

Wollastonite 1D nanostructures have attracted widespread concern for their wide applications in biomedical, constructions and many more, which however have been synthesized via high temperature solid state method or wet precipitation method which required organic template. Herein, a controllable green hydrothermal route is used to produce high aspect ratio wollastonite nanofibers. The effect of hydrothermal synthesis parameters on the aspect ratio of synthetic wollastonite nanofibers (SWN) were investigated and the hydrothermal formation mechanism was proposed. The formation of nanofiber starts from the nuclei formation in supersaturated solution then followed by the crystal growth. The synthesis reactions were conducted under different conditions with reaction medium containing different ethanol composition and temperature from 160 °C to 240 °C for 8 h to 32 h. The SWN produced was characterized using XRD, FTIR, TGA and FESEM analysis techniques. It is proven that all wollastonite produced were in nanofiber form with the average aspect ratio ranging from 10 to 20, except for those synthesized at 160 °C which mainly has irregular grain shape. The reaction medium consisting of 80% water and 20% ethanol, which was heated at 200 °C for 16 h, resulted in SWN with the highest aspect ratio of 20.15. The study demonstrated that the hydrothermal synthesis parameters can be manipulated to produce SWN with various aspect ratios to meet its demand in different applications.

Hydroxyapatite nanoparticles derived from mussel shells for in vitro cytotoxicity test and cell viability

Hydroxyapatite (HA) nanoparticles derived from mussel shells were prepared using the wet precipitation method and were tested on human mesenchymal and epithelial cells. Shells and HA powder were characterized via X-ray diffraction analysis (XRD) and scanning electron microscopy along with energy dispersive X-ray spectroscopy (SEM/EDX), high resolution transmission electron microscopy (HR-TEM) and Fourier transform infrared spectroscopy (FTIR). The in vitro cytotoxic properties of HA and mussel shells were determined using sulphorhodamine B (SRB) assays for MCF-7 cells (HepG2) and colon (Caco-2) cells. Cell viability tests confirmed the nontoxic effects of synthesized HA and mussel shells on human mesenchymal stem cells (h-MSCs) and epithelial cells. Toxicity values were less than 50% of the cell's validity ratio based on analyses using different concentrations (from 0.01 to 1,000 μg). The results indicate that MSC and epithelial cell attachment and proliferation in the presence of both HA and shell occurred.The proliferation capability was established after 3 and 7 days. SEM images revealed that stem cells and epithelial cells attached to the scaffold indicated full and complete integration between the cells and the material. It seems that due to the ion exchange between bovine serum albumin solutions (BSA) and HA, the FTIR data confirmed an increase in the amide I and amide II bands, which indicates the compatibility of the BSA helix structure. This study sheds light on the importance of merging stem cells and nanomaterials that may lead to improvements in tissue engineering to develop novel treatments for various diseases.

Preparation of Poly(DL-Lactide/ε-Caprolactone)– β -TCP Compozites for Bone Tissue Repair

Poly-D,L-Lactide/ε-caprolactone (PDLLA-ε-CL) and β-tri-calcium phosphate (β-TCP) composites were prepared for the development of a degradable material as an alternative for injectable filling material in bone tissue repair. For this purpose, β-TCP was synthesized by wet precipitation method. β-TCP was characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffractometer (XRD), Zeta-SIZER and Brunauer–Emmett–Teller (BET) analyser. PDLLA-ε-CL co-polymer was synthesized under nitrogen (N2) atmosphere using ring-opening polymerization using stannous octoate as catalyst. Chemical structures of copolymers were determined by FTIR and Proton Nuclear Magnetic Resonance (H-NMR) analysis. Average molecular weight of copolymers were identified with Gel Permeation Chromatography (GPC). (PDLLA-ε-CL)-β-TCP composites were prepared by loading differing amounts of β-TCP to the co-polymer. The resulting composites were easily shaped by hand. The degradation profiles of the composites were determined by monitoring the changes in the molecular weight of the co-polymers over a period of 49 days. Degradation rate of the composites decreased as the percentage of β-TCP in the structure increased

Structural and Biological Analysis of Mesoporous Lanthanum Doped βTCP For Potential Use as Bone Graft Material

In this study, mesoporous particles of β-tricalcium phosphate (βTCP, βCa3(PO4)2) and lanthanum (La) doped βTCP were synthesized using wet precipitation method attached with microwave refluxing system. The obtained materials were characterized and analysed using different sort of techniques such; X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), Inductively coupled plasma optical emission spectroscopy (ICP-OES), Brunauer–Emmett–Teller (BET) and helium pycnometer. With incorporation of La3+ ions, relevant expansion in lattice parameters of βTCP crystal was observed along with inhibition growth rate was observed. βTCP and La- βTCP materials were mesoporous in nature, pore diameter and pore volume were expanded with incorporation of La3+ ions. The loading /release on βTCP and La- βTCP particles surfaces were evaluated using fetal bovine serum (FBS) proteins. In vitro cell culture studies were performed with human osteosarcoma cell line (Saos-2). The outcomes approved that all La-βTCP materials were cytocompatible and strict dose dependent effect of La3+ ions was observed on cell viability and alkaline phosphatase (ALP) activity. These results strongly suggest that La-βTCP materials have a potential application in bone tissue engineering.

New Chemicals and Routes for the Preparation of Gelatin/HA Composites using the Wet Precipitation Method

Hydroxyapatite (HA) is a material that has many uses in a wide variety of applications such as bone repair, bone implants, and bone drug delivery systems. However, the main weakness of this material is its mechanical strength, which HA is not enough to be directly applied. Gelatin addition is used to improve the mechanical properties that can support material properties for the load-bearing application. This research aimed to obtain gelatin/HA composites with high mechanical strength. This goal is achieved by finding the optimum composite composition (addition of 20, 30, and 40% w/w gelatin), CaO precursors from chicken eggshells, and gradual composite preparation. The preparation of gelatin/HA composites was carried out using the wet precipitation method. The chemical bonding, the compressive strength of HA and gelatin/HA composites, and also morphologies were analyzed by Fourier Transform Infra-Red (FTIR), Universal Testing Machine, and Scanning Electron Microscopy (SEM) respectively. The FTIR spectra show there are chemical bonds between amide and carboxyl in gelatin and Ca2+ in HA. The best compressive strength obtained at the composition of 20% gelatin/HA composite is 99.3 MPa (meanwhile HA is 81.5 MPa). The addition of gelatin to HA increases the particle density; this contributes to the increase in mechanical strength.

Development of Triphasic Hydroxyapatite/(α and β)-Tricalcium Phosphate Based Composites by Sintering Powder of Calcium-Apatite in the Presence of Montmorillonite

In recent years, the development of calcium phosphate/clay composites for bone tissue engineering attracted a lot of interest. In this study, novel bio-composites composed of hydroxyapatite (HAP), α and β-tricalcium phosphate (α, β-TCP) and sodium-montmorillonite (MNa) were developed. The composites were prepared by sintering at 900 °C of calcium-apatite powders in the presence of various amounts of MNa. The calcium-apatite precursors were prepared by the wet precipitation method with two desired Ca/P molar ratios (1.660 and 1.623). Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to characterize the prepared composites. The results showed that during the sintering process, a surface interaction apatite/MNa led to the incorporation of clay ions into the apatite structure resulting in its decomposition and formation of composite ceramics comprising HAP, β and α-TCP. The decomposition of apatite increased with increasing MNa content and with decreasing Ca/P ratio. The decomposition of stoichiometric HAP led to triphasic ceramics with substituted-HAP as the major phase while the decomposition of calcium-deficient HAP led to triphasic ceramics with substituted-α-TCP as the major phase. Combination of MNa–clay phase and substituted-α-TCP can improve both mechanical and biological properties of the prepared composites.

Preparation of anti-bacterial biocomposite nanofibers fabricated by electrospinning method

Developing technology and increasing the number of living creatures on earth increase the demand for biomaterials each passing day. Recently, biocomposite and biodegradable biomaterials have begun to attract attention in many areas of usage. Electrospinning technique is preferred as a quite consolidated technique in the production of outstanding polymer and/or nanofiber matrixes. However, obtained biocomposite nanofibers can cause microbiological infections during or after their usage. Therefore, it is very important that such materials have controlled antibacterial properties. In this study, Hydroxyapatite (HAp), known as biocompatible and bioactive, was firstly synthesized by wet precipitation method. Molecular structure of obtained HAp particles was researched by Fourier Transform Infrared Spectroscopy (FT-IR), its crystal structure was analyzed by X-ray Diffraction analysis (XRD) and its morphology was investigated by Scanning Electron Microscopy (SEM). HAp particles were combined with a mixture of biodegradable polylactic acid (or polylactide, PLA) and polycaprolactone (PCL) and biocomposite nanofibers were prepared by electrospinning method by loading chitosan and /or silver-based inorganic antimicrobial agent in different proportions to this composite structure. Molecular structure of PLA-PCL polymer matrix was investigated by FT-IR analysis. The morphology of the obtained biocomposite nanofibers was examined by SEM. The anti-bacterial efficiency of biocomposite nanofibers containing chitosan and/or Ag+ in different proportions was investigated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. Biocomposite nanofiber samples containing 1% chitosan and 0.25% Ag+ were found to have ≥4.78 log reduction and ≥99.99% reduction in the bacterial population against the tested bacterial species and showed strong antibacterial properties. It was also observed that the combination of Ag+ and chitosan may show synergistic effects. The results of the study confirm the great potential of biodegradable, biocompatible and bioactive fibers for antibacterial application.

Synthesis and characterization of antibacterial drug loaded β-tricalcium phosphate powders for bone engineering applications.

Powders of β-tricalcium phosphate [β-TCP, β-Ca3(PO4)2] and composite powders of β-TCP and polyvinyl alcohol (PVA) were synthesized by using wet precipitation methods. First, the conditions for the preparation of single phase β-TCP have been delineated. In the co-precipitation procedure, calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphorous precursors, respectively. The pH of the system was varied in the range 7-11 by adding designed amounts of ammonia solution. The filtered cakes were desiccated at 80 °C and subsequently calcined at different temperatures in the range between 700-1100 °C. Later on, rifampicin form II was used to produce drug-loaded β-TCP and PVA/β-TCP powders. All the synthesized materials have been characterized from morphological (by scanning electron microscopy) and structural-chemical (by X-ray diffraction and Fourier transform infrared spectroscopy) point of view. The drug loading capacity of the selected pure β-TCP powder has been assessed. The biological performance (cytocompatibility in fibroblast cell culture and antibacterial efficacy against Escherichia coli and Staphylococcus aureus) has been tested with promising results. Application perspectives of the designed drug-bioceramic-polymer blends are advanced and discussed.

Synthesis of hydroxyapatite from meti shells (batissa violecea l. Von Lamark 1818) by wet precipitation method

Hydroxyapatite (Ca10(PO4)6(OH)2 has been synthesized from Meti shells (Batissa violecea L. Von Lamark 1818) by using wet precipitation method. The purposes of hydroxyapatite synthesis from Meti shells are to determine the effect of sintering temperature and acidity (pH) on yield and IR spectrum. The sintering temperatures used for synthesis were 800, 900, 1000, and 1100°C, while the pH of the synthesis included 8, 9, 10, and 11. The hydroxyapatite compound was characterized by using XRD and SEM. The result showed that the sintering temperature of 1100°C and pH 9 resulted in the best hydroxyapatite with a yield of 60.10%. The IR spectrum showed that utilizing of 1100°C and pH 9 was the result of the low impurity absorption of CO32- group at the wavelength of 1641.42 cm-1 and 1415.5 cm-1. The diffractogram of hydroxyapatite showed a high intensity at 2ϴ angle of 31.74°, 39.74°, and 46.64°. Morphological analysis of hydroxyapatite showed that particles were agglomerated with a particle diameter of 0.77 μm.

Application of Statistical Experimental Design and Surface Plot Technique to Optimize Oxygenated Apatite Synthesis

This work deals with oxygenated apatite synthesis from calcium chloride and phosphoric acid using a wet precipitation method. An experimental design is applied to precise the influence of the synthesis parameters (pH of the reaction medium, atomic ratio Ca/P of the reagents, concentration of the calcium solution (Ca2+), temperature of the reaction medium (T), and duration of the reaction (D)) on the chemical composition (Ca/P molar ratio, % O2, and ). An empirical model was developed and validated by applying the ANOVA analysis incorporating the interaction effects of all parameters and optimized using the response surface methodology. A reproducible synthesis of more oxygenated apatite with speed of dissolution adaptable to that of the osseous neoformation and allowing a progressive diffusion of oxygenated species (Ca/P = 1.575) is attained.

Influence of doping chromium ions on the electrical properties of hydroxyapatite

ABSTRACT Hydroxyapatite Ca10[PO4]6[OH] is a biocompatible widely used in medicine and dentistry. Its applications depend greatly upon lattice substitution of Calcium sites in its structure by varies cations such as Na, Mg, Sr, Ag etc. Chromium plays an important role in reducing blood sugar level and improving insulin ability to convert glucose in cells to gain energy. In this paper we studied the effect of doping hydroxyapatite with chromium ions on its crystal dielectric properties. Pure hydroxyapatite and chromium loaded hydroxyapatite of chromium concentrations of 0.5, 1.0, 2.0, and 3.0 wt % forming samples S1, S2, S3 and S4 respectively were prepared by wet precipitation method. The dielectric parameters, permittivity ἐ, dielectric loss ἕ, conductivity σ, relaxation time ts and dielectric modulus M’ and M’’ were calculated at frequency of 20 Hz to 10 MHz. Results showed increase of ἐ, and ἕ, values of chromium loaded samples compared to pure hydroxyapatite. The conductivity of the doped samples was increased with chromium concentration increase. The relaxation times (ts) chromium loaded samples showed increase of ts as chromium concentration increase. The dielectric properties showed that as chromium concentration increase, ἐ, ἕ, and σ of substance increase compared to the pure HA.

Evaluation of Mesenchymal Stem Cells and Osteoblasts’ Adhesion and Proliferation in the Presence of HA-AL Biomaterials

There is an increased interest in developing biocomposite implants with high biocompatibility in order to be used as grafts or prostheses in orthopedic surgery. The purpose of the study was to determine the biocompatibility of titanium implants coated with synthesized hydroxyapatite-alendronate composites. The implants were obtained using Matrix Assisted Pulsed Laser Evaporation technique (MAPLE). The hydroxyapatite-alendronate composites were synthesized using the wet precipitation method. Immunofluorescence microscopy showed that composites support mesenchymal stem cells (MSCs) adhesion. Bone cells as well as human MSCs adhere to hydroxyapatite (HA)-based thin films obtained by matrix assisted laser deposition onto titanium. Alendronate doping into the films increased the number of cell-biomaterial focal points as compared to HA only. Thus, the synthesis of hydroxyapatite-alendronate composite (HA-AL) may be considered a viable solution for including the bisphosphonate on the surface of metallic prosthetic components used in orthopedics.

Strontium substituted biomimetic calcium phosphate system derived from cuttlefish bone.

Biomimetic triphasic strontium-substituted calcium phosphate (CaP) powders were prepared by wet precipitation method at 50°C, using CaCO3 , (NH2 )2 COH3 PO4 , and Sr(NO3 )2 as reagents. Calcite was prepared from biogenic source (cuttlefish bone). The synthesized powders have been characterized by elemental analysis, Fourier transform infrared spectrometry, X-ray diffraction, Rietveld refinement studies and cell viability test. Phase transformation and ion release were analyzed during 7 days of incubation in simulated body fluid at 37°C. The raw precipitated powders were composed of calcium deficient carbonated hydroxyapatite (HA), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP). After heat treatment at 1200°C β-tricalcium phosphate (β-TCP) was detected. Strontium substitution for calcium results in an increase of lattice parameters in HA, OCP, and β-TCP. Sr2+ occupy the Ca(1) site in HA, Ca(3,4,7,8) sites in OCP and Ca(1,2,3,4) sites in β-TCP. Along with Sr2+ substitution, presence of Mg2+ and Na+ ions was detected as a result of using biogenic calcium carbonate. The culture of human embryonic kidney cells indicated noncytotoxicity of the prepared CaP powders with emphasis on the cell proliferation during 3 days of culture.

Optical and magnetic properties of wollastonite and its nanocomposite crystalline structure with hematite

It is important to develop novel, highly bioactive implants with suitable magnetic properties. Nanostructure wollastonites (calcium silicate) with various concentrations of hematite (Fe2O3) up to7% prepared by wet precipitation method and sintered up to (1273 K) were investigated. The developed phases were CaSiO3 of a monoclinic nanocrystalline structure and samples with Fe2O3 contents had both major monoclinic and minor rhombohedral nanocomposite. All samples were in the nano-size based on the XRD data, which was confirmed by HR-TEM analysis and FE-SEM micrographs. The optical diffused reflection spectra were measured at ambient atmosphere (300 K) as a function of wavelength. Optical properties exhibited semiconductor behavior with optical energy band gap of about 2.2 ± 0.07 eV, as a result of the presence of hematite, and the preparation conditions. Magnetic results showed different types of hysteresis at 300 K. Diamagnetic and paramagnetic behavior were observed for wollastonite and its nanocomposite of 1% hematite, while weak ferromagnetic behavior was elucidated for that with 3% hematite. Moreover, butterfly-shape with a bottleneck effect was predominant for nanocomposite of 5% and 7% hematite. The 7% hematite sample has higher values of magnetic parameters rather than the 5% one. The multifaceted magnetic behaviors are due to the Fe2O3 content. Coincided curves of zero field cooling (ZFC) and field cooling (FC) for the 7% hematite sample were verified in temperature range from 100 to 350 K. Advanced Fe2O3-wollastonite containing magnetic properties have triggered attention due to their possible application in bone filler and hyperthermia treatment.

Comparative studies for CO oxidation and hydrogenation over supported Pt catalysts prepared by different synthesis methods

Pt supported on TiO2 and ZrO2 catalysts were synthesized via wet impregnation and deposition precipitation methods. The catalysts were tested for CO removal from reformate gas following the water-gas shift reaction for on-board fuel processors. Tests included oxidation of CO to CO2, preferential oxidation of CO to CO2 in the presence of H2 (PROX), and hydrogenation of CO to CH4 (selective methanation, SMET). The Pt–ZrO2 catalysts showed better metal dispersions, particle sizes, lower degrees of reduction and higher oxygen storage capacities than the TiO2 supported catalysts. All catalysts showed low activity for the oxidation of CO in the PROX reaction, due to H2 and O2 spillover effects. ZrO2, with its high reducing properties and strong metal-support interactions, was found to be the best support for hydrogenation of CO. ZrO2 induced small well-dispersed Pt particles that were key parameters in this reaction. Both Pt–ZrO2 catalysts showed CO conversions over 99% above 350 °C with high CH4 selectivities (99%). The study shows advantageous effects of strong metal to support interactions, like participation of MOx (support) species in activating the CO molecule. The CO concentration was effectively reduced to the desired ppm levels (<10 ppm) required for optimum fuel cell operation.