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Improving the Mechanical Properties of Nano-Hydroxyapatite
Title
Improving the Mechanical Properties of Nano-Hydroxyapatite.
Creator
Khanal, Suraj P., Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description
Hydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and...
Show moreHydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and polymerized ɛ-caprolactam (nylon) is studied. The fracture toughness, tensile strength, Young’s modulus, stiffness and fracture energy were studied for a series of HAp samples with CfSWCNT concentrations varying from 0 to 1.5 wt. % without, and with nylon addition. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were used to characterize the samples. The fracture toughness and tensile test was performed under the standard protocol of ASTM D5045 and ASTM D638-02a respectively. Reproducible maximum values of (3.60 ± 0.3) MPa.m1/2 for fracture toughness and 65.38 MPa for tensile strength were measured for samples containing 1 wt. % CfSWCNT and nylon. The Young’s modulus, stiffness and fracture energy of the samples are 10.65 GPa, 1482.12 N/mm, and 644 J/m2 respectively. These values are comparable to those of the cortical bone. Further increase of the CfSWCNT content results to a decreased fracture toughness and tensile strength and formation of a secondary phase.
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Date Issued
2016
PURL
http://purl.flvc.org/fau/fd/FA00004675, http://purl.flvc.org/fau/fd/FA00004675
Subject Headings
Biomedical engineering -- Materials, Biomedical materials -- Mechanical properties, Nanostructured materials -- Mechanical properties
Format
Document (PDF)
Simultaneous x-ray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite
Title
Simultaneous x-ray and neutron diffraction Rietveld refinements of nanophase Fe substituted hydroxyapatite.
Creator
Kyriacou, Andreas, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description
The effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0
Show moreThe effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0< x < 0.3 were prepared. Single phase HAp was identified in x-ray diffraction patterns (XRD) of samples with x < 0.1 inferring that the solubility limits are less than 0.1. Hematite ((Sa(B-Fe2O3) is identified as a secondary phase for higher Fe content. The refined parameters show that Fe is incorporated in the HAp structure by replacing Ca in the two crystallographic sites with a preference at the Ca2 site. This preference explains the small effect of the Fe substitution on the lattice constants of HAp. The overall decrease of the lattice constants is explained by the ionic vi size difference of Ca and Fe. The increasing trend of the a-lattice constant with x in the Fe substituted samples is attributed to a lattice relaxation caused by the substitution of the 4- and 6-fold Fe at the 7- and 9-fold Ca1 and Ca2 sites. This Ca local geometry reduction is indicated by a slight increase of the Ca1-O3 and Ca2-O1 bond lengths. Above the solubility limit x = 0.05, the Fe is partitioned in and out of the HAp structure with increasing nominal Fe content x. The excess Fe is oxidized to hematite. The TEM analysis and magnetic measurements support the results of the simultaneous Rietveld refinements. The TEM images show no significant effect on the morphology and size of the HAp particles upon Fe incorporation. The particles are either spheres or short rods of dimensions 20-60 nm. Hematite particles are imaged in the samples with x exceeding the solubility limit. These particles
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Date Issued
Florida Atlantic University
PURL
http://purl.flvc.org/FAU/3342204
Subject Headings
X-rays, Diffraction, Rietveld method, Nanostructured materials, Biomedical materials
Format
Document (PDF)
Effect of Processing Temperature on the Properties of Nanophase Fe-substituted Hydroxypatite
Title
Effect of Processing Temperature on the Properties of Nanophase Fe-substituted Hydroxypatite.
Creator
Kathriarachchi, Vindu, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description
The effect of processing temperature on the crystal structure properties of the Fe-substituted Hydroxyapatite (Fe-HAp) was studied by using the Rietveld refinement method of powder x-ray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and x-ray fluorescence spectroscopy (XRF) were used to study the magnetic properties, particle morphology and chemical composition of the prepared samples. Two...
Show moreThe effect of processing temperature on the crystal structure properties of the Fe-substituted Hydroxyapatite (Fe-HAp) was studied by using the Rietveld refinement method of powder x-ray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and x-ray fluorescence spectroscopy (XRF) were used to study the magnetic properties, particle morphology and chemical composition of the prepared samples. Two sets of samples of chemical formula Ca5-xFex(PO4)3OH were prepared with x = 0, 0.05, 0.1, 0.2 and 0.3 by using processing temperatures of 37°C and 80°C, following a two-step co-precipitation method. A single phase HAp was identified in samples with x = 0 and 0.05. Processing temperature affects the type and percentage of secondary phases: hematite was detected in samples prepared at 37°C with x ≥ 0.1, hematite and maghemite were detected in samples prepared at 80°C with x = 0.2 and 0.3. Rietveld refinements of NPD and XRD patterns showed that the a lattice constants are greater in Fe-substituted samples prepared at 37°C, whereas the c lattice constants are greater in the 80°C samples for x ≥ 0.05. Fe preferentially substitutes at the Ca2 site in the 80°C samples, whereas Ca1 is the preferred substitution site in the 37°C samples. Fe substitution results to a decrease of the lattice constants at both preparation temperatures. The ratios Fe/(Fe + Ca) of the refined atomic fractions of the samples prepared at 80°C are greater than those of the 37°C samples. Further, more secondary phases form in samples prepared at 37°C compared to 80°C samples. The magnetic measurements reveal that pure HAp is diamagnetic, whereas samples with x = 0.05 and 0.1 are paramagnetic. Samples with x = 0.3 showed superparamagnetic behavior based on ZFC and FC measurements. Similar hysteresis loops in samples x = 0.2 and 0.3 indicate that the samples with x = 0.2 may show superparamagnetic properties. For x = 0.2 and 0.3, the samples prepared at 80°C showed higher magnetization compared to the 37°C samples, because of the maghemite secondary phase. Based on the TEM images, Fe substituted HAp nanoparticles prepared at 37°C are mainly spherically shaped, and the 80°C particles are mainly elongated. Increase of the Fe concentration favors formation of elongated particles and larger spherical particles. The XRF measurements confirm the Fe for Ca substitution in the HAp structure based on the decrease of the Ca/P and the increase of the Fe/(Fe + Ca) atomic ratios with the Fe concentration.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00004512, http://purl.flvc.org/fau/fd/FA00004512
Subject Headings
Biomedical materials, Nanostructured materials -- Environmental aspects, Nanostructured materials -- Mechanical properties, Pharmaceutical biotechnology, Rietveld method
Format
Document (PDF)
Finite element analysis and modeling of the anterior cruciate ligament in the human knee
Title
Finite element analysis and modeling of the anterior cruciate ligament in the human knee.
Creator
Savage, Tabatha Jordan, Hashemi, Javad, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
The Anterior Cruciate Ligament (ACL) resists excessive anterior translation and internal rotation of the tibia during athletic activities and stabilizes the knee. In the US, annually, over 200,000 cases of ACL disruption are reported. The impact on the quality of life of the subject and its cost to healthcare is tremendous. The objectives of this study were to determine any significant associations between the size of the tibial eminence and ACL injury and to develop a finite element model...
Show moreThe Anterior Cruciate Ligament (ACL) resists excessive anterior translation and internal rotation of the tibia during athletic activities and stabilizes the knee. In the US, annually, over 200,000 cases of ACL disruption are reported. The impact on the quality of life of the subject and its cost to healthcare is tremendous. The objectives of this study were to determine any significant associations between the size of the tibial eminence and ACL injury and to develop a finite element model for structural analysis. The results suggest that the size of the tibial eminence plays a role in loading the ACL and is therefore a risk factor. In addition to the epidemiological analysis, a finite element model of the knee was developed that with added modifications can be used for complex knee loading situations. The results in this thesis may be used to develop strategies for ACL injury prevention and rehabilitation.
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Date Issued
2014
PURL
http://purl.flvc.org/fau/fd/FA00004327, http://purl.flvc.org/fau/fd/FA00004327
Subject Headings
Arthroscopy, Athletic injuries -- Prevention, Biomedical materials, First aid in illness and injury, Human mechanics, Joints -- Pathophysiology, Sports -- Physiological aspects, Sports medicine
Format
Document (PDF)
The expression and analysis of a lysine-rich wound-response protein in tomato plants.
Title
The expression and analysis of a lysine-rich wound-response protein in tomato plants.
Creator
Kaplan, Noah, Zhang, Xing-Hai, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
Understanding the genetic regulation of the response to wounding and wound healing in fruiting plants is imperative to maintaining agricultural sustainability, preserving the quality of food supplies, and ensuring the economic viability of agriculture. Many genes are known to be induced by wounding, providing both structural repair and defense. The KED gene in tobacco (Nicotiana tabacum) has been shown to be induced by wounding. We have identified its homologue gene in tomato (Solanum...
Show moreUnderstanding the genetic regulation of the response to wounding and wound healing in fruiting plants is imperative to maintaining agricultural sustainability, preserving the quality of food supplies, and ensuring the economic viability of agriculture. Many genes are known to be induced by wounding, providing both structural repair and defense. The KED gene in tobacco (Nicotiana tabacum) has been shown to be induced by wounding. We have identified its homologue gene in tomato (Solanum lycopersicum) that we named SlKED. We have analyzed gene expression pattern of SlKED through tomato growth and development and in response to wounding as well as hormonal and inhibitor treatments. We found that the plant hormone ethylene played a major role in the expression of SlKED. To further identify evidence for physiological and transductional functions of KED and SlKED, the tobacco KED gene was introduced to tomato and overexpressed by the fruit tissue-active PUN1 promoter from pepper (Capsicum annuum,). The expression of this gene was compared to the expression of the native SlKED gene and other known wound response genes in both the wild-type and transgenic tomato plants. The upregulation of the native SlKED gene by wounding was significantly muted in the tobacco KED-expressing transgenic plants. The expression of other genes known to be associated with wound response transduction pathways was also altered. Our studies implicate the KED gene in defense mechanisms for mechanical stress in tomato plants.
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Date Issued
2016
PURL
http://purl.flvc.org/fau/fd/FA00004773, http://purl.flvc.org/fau/fd/FA00004773
Subject Headings
Wound healing., Wounds and injuries--Genetic aspects., Plant gene expression., Plant genetic regulation., Nanostructured materials--Physiological effect., Biomedical engineering.
Format
Document (PDF)