ESR Detection of X-Ray-Induced Free Radicals in Crosslinked Silica Aerogels

MRS Advances ◽  
2017 ◽  
Vol 2 (57) ◽  
pp. 3521-3529
Author(s):  
Benjamin M. Walters ◽  
Ramón V. León ◽  
Muhammad S. Jahan ◽  
Firouzeh Sabri
Keyword(s):  
Free Radicals ◽  
Storage Conditions ◽  
X Ray ◽  
Aerospace Applications ◽  
Polyether Ether Ketone ◽  
Spin Resonance ◽  
Radiation Resistant ◽  
X Irradiation ◽  
Ether Ketone ◽  
Ultra High Molecular Weight

ABSTRACTAerogels are a promising material for aerospace applications and have recently been explored for biomedical applications also. In both environments, exposure to radiation is inevitable, such as from radiation in space or, radiation-based sterilization and tracking of implants. X-ray radiation, in particular, is of a concern. Here, polyurea-crosslinked silica aerogel (PCSA) samples were exposed to approximately 170- and 500-Gy X-irradiation at room temperature under varying environmental conditions and characterized using electron spin resonance (ESR) technique. Results obtained for PCSA were compared with those from polyether-ether ketone (PEEK) and ultra-high molecular weight polyethylene (UHMWPE) which served as benchmarks for this study. PEEK is known to be very radiation resistant, while UHMWPE is known to be less radiation resistant. All materials (PCSA, PEEK, and UHMWPE) were exposed to the same treatments and exposure conditions. Two exposure times were tested: 10 min and 30 min which corresponded to “low” and “high” conditions, as well as comparisons of nitrogen vs. air environments during exposure and post-exposure storage. Results showed significant quantities of free radicals produced in PCSA after exposure to X-irradiation which scaled with radiation dosage; quantities were in-between those produced in PEEK and UHMWPE. The storage conditions (air vs. nitrogen) also played an important role in the free radical levels detected and are reported in this study.

Thermal Expansion of Polyether Ether Ketone Bearing Components

2019 ◽  
Vol 64 (4) ◽  
pp. 1-5 ◽  
Author(s):  
Bryan D. Allison ◽  
Connor M. Vanderwiel
Keyword(s):  
Thermal Expansion ◽  
Elevated Temperatures ◽  
Coefficient Of Thermal Expansion ◽  
Aerospace Applications ◽  
Polyether Ether Ketone ◽  
Molded Parts ◽  
Injection Molded ◽  
Ether Ketone ◽  
Bearing Design ◽  
Strong Candidate

Carbon fiber–reinforced polyether ether ketone (PEEK) is a strong candidate for aerospace bearing cages due to its low density and good mechanical properties. However, there are still concerns regarding its performance at the elevated temperatures seen in aerospace applications. In particular, an accurate measurement of PEEK's coefficient of thermal expansion (CTE) is critical to proper bearing design. In this paper, the CTE of as-manufactured PEEK cages was measured to determine the range of CTE that can be expected for production parts. A range of cage sizes and designs were considered in this study. Components that were manufactured from stock shapes through subtractive methods were studied in addition to components made via injection molding. The CTE of machined PEEK was found to be significantly higher than that of injection-molded PEEK and also varied significantly from part to part. In contrast, the CTE of molded PEEK cages was found to be fairly consistent between parts. Finally, the CTE of PEEK was found to increase above the glass transition temperature of 143 °C, but it was demonstrated that this increase is relatively small for injection-molded parts.

Über die Radikalkonzentration von Rattenleber-Mitochondrien in Abhängigkeit von verschiedenen Faktoren

1968 ◽  
Vol 23 (6) ◽  
pp. 798-803 ◽  
Author(s):  
M. Waldschmidt ◽  
H. Mönig ◽  
J. Schole
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Mitochondrial Protein ◽  
Yeast Cells ◽  
Whole Body ◽  
Resonance Spectroscopy ◽  
Control Value ◽  
Spin Resonance ◽  
X Irradiation

The concentration of free radicals in freshly prepared ratliver-mitochondria was investigated under different conditions with the aid of electron spin resonance spectroscopy. The electron spin resonance signal at g=2.004 was measured at 77 °K and related to the weight in milligrams of mitochondrial protein. The concentration of free radicals increases with rising body weight or, in other words, with decreasing growth rate of the animals. A plateau is reached with about 1013 radicalcenters per mg protein for grown animals. The concentration of free radicals is 150% of the control value after fasting for 24 hours, whereas it is below the detectable level in cells of ascites hepatoma. We conclude that the concentration of free radicals determined at g = 2.004 is a function of mitochondrial activity. After whole body x-irradiation with a dose of 900 R, a significant decrease of 20% of the signal amplitude was measured. Increasing the dose to 1800 R did not decrease the radical concentration further. These results might be connected with the diminished activity of some flavin enzymes observed in liver mitochondria after x-irradiation in vivo. In further experiments we have incubated the mitochondria in vitro with various inhibitors of flavin enzymes. The individual inhibitors (ammonium-ions, KCN, acetonitrile, glucose) and also malonate reduce the concentration of free radicals to 80% of the control value in the mean if the particles are incubated at 37 °C for 5 minutes. The effect of malonate adds to the effects of the other inhibitors. The inhibitory effect of 2,4-dinitrophenol develops only after a longer incubation time. These results are discussed in connection with the influence of the same inhibitors on the Pasteureffect of yeast cells. Some specific inhibitors of the respiratory chain (Amytal, antimycin A, oligomycin) also diminish the concentration of free radicals.

Studying Mechanical Properties Specially Fatigue Behavior of (Polyether Ether Ketone)/Glass Fiber Composites in Aerospace Applications

2014 ◽  
Vol 666 ◽  
pp. 8-16
Author(s):  
A. Saad Najim ◽  
Mohammed Adwaa
Keyword(s):  
Mechanical Properties ◽  
Glass Fiber ◽  
High Performance ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Glass Fiber Composites ◽  
Aerospace Applications ◽  
Polyether Ether Ketone ◽  
High Performance Composite ◽  
Ether Ketone

This work deals with studying the mechanical properties specially fatigue behavior for high performance composite materials of poly ether ether ketone (PEEK)/glass fiber, which are used in Aircraft Industry. Two materials have been used: (PEEK natural) and (PEEK+30% glass fiber).To identify the type of (PEEK), infrared (FTIR) test has been conducted. X-ray test has been used to measure the (PEEK) crystalline ,also the tensile properties, impact strength and the fatigue test are performed.The results show that FTIR test peaks are for standard PEEK polymer and that GFRP increases the crystalline of (PEEK) material , while the tensile , impact and fatigue properties of (PEEK) decreases by adding GF to PEEK .

scholarly journals PEEK based cranial reconstruction using thermal assisted incremental sheet forming

2021 ◽  
pp. 095440542110459
Author(s):  
Lin-feng Chen ◽  
Fei Chen ◽  
Shakir Gatea ◽  
Hengan Ou
Keyword(s):  
Manufacturing System ◽  
Sheet Forming ◽  
Incremental Sheet Forming ◽  
Localized Deformation ◽  
Temperature Dependent ◽  
X Ray ◽  
Polyether Ether Ketone ◽  
Desktop Manufacturing ◽  
Ether Ketone ◽  
Orthopedic Applications

Compared to conventional sheet forming operations, incremental sheet forming (ISF) is a flexible forming technique that can achieve higher formability in terms of localized deformation. Due to excellent mechanical properties and X-ray penetration, polyether-ether-ketone (PEEK) is an ideal alternative to titanium alloy and stainless steel in orthopedic applications. In this study, a 3-axis desktop manufacturing system has been fabricated to investigate the temperature-dependent formability of PEEK in terms of manufacturing the cranial plate by using the ISF technique. Meanwhile, the forming force, temperature distribution, geometrical accuracy, and thermal properties were obtained and analyzed. The findings indicate that the ISF technique provides technological and economic advantages in cranial reconstruction by using PEEK.

scholarly journals Electrochemical Detection of Dopamine at Fe3O4/SPEEK Modified Electrode

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5357
Author(s):  
Mogomotsi N. Ranku ◽  
Gloria E. Uwaya ◽  
Omolola E. Fayemi
Keyword(s):  
Modified Electrode ◽  
Square Wave Voltammetry ◽  
Electrochemical Behaviour ◽  
Phosphate Buffer Solution ◽  
Buffer Solution ◽  
X Ray ◽  
Polyether Ether Ketone ◽  
Wave Voltammetry ◽  
Ether Ketone ◽  
Screen Print

Reported here is the design of an electrochemical sensor for dopamine (DA) based on a screen print carbon electrode modified with a sulphonated polyether ether ketone-iron (III) oxide composite (SPCE-Fe3O4/SPEEK). L. serica leaf extract was used in the synthesis of iron (III) oxide nanoparticles (Fe3O4NPs). Successful synthesis of Fe3O4NP was confirmed through characterization using Fourier transform infrared (FTIR), ultraviolet–visible light (UV–VIS), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). Cyclic voltammetry (CV) was used to investigate the electrochemical behaviour of Fe3O4/SPEEK in 0.1 M of phosphate buffer solution (PBS) containing 5 mM of potassium ferricyanide (III) solution (K3[Fe(CN)6]). An increase in peak current was observed at the nanocomposite modified electrode SPCE-Fe3O4/SPEEK) but not SPCE and SPCE-Fe3O4, which could be ascribed to the presence of SPEEK. CV and square wave voltammetry (SWV) were employed in the electroxidation of dopamine (0.1 mM DA). The detection limit (LoD) of 7.1 μM and 0.005 μA/μM sensitivity was obtained for DA at the SPCE-Fe3O4/SPEEK electrode with concentrations ranging from 5–50 μM. LOD competes well with other electrodes reported in the literature. The developed sensor demonstrated good practical applicability for DA in a DA injection with good resultant recovery percentages and RSDs values.

scholarly journals Surface Morphology and Mechanical Properties of Polyether Ether Ketone (PEEK) Nanocomposites Reinforced by Nano-Sized Silica (SiO2) for Prosthodontics and Restorative Dentistry

Polymers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 3006
Author(s):  
Ahmed Abd El-Fattah ◽  
Heba Youssef ◽  
Mohamed Abdel Hady Gepreel ◽  
Rafik Abbas ◽  
Sherif Kandil
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Flexural Strength ◽  
Suitable Alternative ◽  
X Ray ◽  
Nano Sio2 ◽  
Polyether Ether Ketone ◽  
Uniform Dispersion ◽  
Sio2 Nanocomposites ◽  
Ether Ketone

In the field of orthopedics and traumatology, polyether ether ketone (PEEK) serves a significant role as a suitable alternative to traditional metal-based implants like titanium. PEEK is being used more commonly to replace traditional dental products. For bonding with various adhesive agents and preserved teeth, the surface alteration of PEEK was investigated. The aim of this research was to understand how different types and contents of nano-sized silica (SiO2) fillers influenced the surface and mechanical properties of PEEK nanocomposites used in prosthodontics. In this work, PEEK based nanocomposites containing hydrophilic or hydrophobic nano-silica were prepared by a compression molding technique. The influence of nano-SiO2 type and content (10, 20 and 30% wt) on surface properties of the resultant nanocomposites was investigated by the use of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), surface roughness analysis, and contact angle measurement. The crystalline structures of PEEK/SiO2 nanocomposites were examined by X-ray diffraction (XRD) spectroscopy. Mechanical properties were measured by microhardness, elastic compression modulus, and flexural strength. All nanocomposites showed increased surface roughness compared to pure PEEK. SEM images revealed that nanocomposites filled with low content hydrophobic nano-SiO2 showed uniform dispersion within the PEEK matrix. The introduction of 10 wt% of hydrophobic nano-SiO2 to the PEEK matrix improved elastic modulus, flexural strength, and microhardness, according to the findings. The addition of nano-SiO2 fillers in a higher weight percentage, over 10%, significantly damages the mechanical characteristics of the resultant nanocomposite. On the basis of the obtained results, PEEK/SiO2 nanocomposites loaded with low content hydrophobic nano-SiO2 are recommended as promising candidates for orthopedic and prosthodontics materials.

scholarly journals Graphene Reinforced Polyether Ether Ketone Nanocomposites for Bone Repair Applications

2020 ◽  
Author(s):  
Nan Jiang ◽  
Peijie Tan ◽  
Miaomiao He ◽  
dan Sun ◽  
Li Zhang ◽  
...  
Keyword(s):  
Mechanical Testing ◽  
Photoelectron Spectroscopy ◽  
Bone Repair ◽  
Early Stage ◽  
Angle Measurement ◽  
X Ray ◽  
Polyether Ether Ketone ◽  
Ether Ketone

To improve the performance of polyether ether ketone matrix (PEEK) in hard tissue repair and replacement applications, we fabricated graphene (G) reinforced PEEK with graded G concentrations (0.1%-5%) through injection molding. The mechanical properties, surface morphology, chemical composition and thermal stability of the composites have been characterized through universal mechanical testing, scanning electron microscopy, contact-angle measurement, transmission electron microscope, X-ray photoelectron spectroscopy, X-ray diffraction and thermal analysis system. The biocompatibility has been assessed in vitro and the bone repair function of the composite implant have been assessed in vivo using a rabbit mandibular bone defect model. Mechanical testing results suggest that the composite samples have compressive moduli similar to that of the natural bone. Although addition of G into PEEK does not significantly influence the composite tensile, flexural or compressive moduli, it can significantly enhance the ductility and toughness of the material. On the other hand, all G-reinforced PEEK implants demonstrated enhanced adhesion and differentiation of rat bone marrow stromal cells (BMSCs), with 5% G-PEEK showing the highest bioactivity among all samples. The in vivo osseointegration data further revealed that 5% G-PEEK has the best effect in promoting osseointegration and bone regeneration, in both early stage and late stage bone re-growth. Study shows that our G-reinforced PEEK-based implants provides a promising strategy for enhancing the performance of future regenerative bone implants.<br>

scholarly journals Insight Into Osseointegration of Nanohydroxyapatite/Polyamide 66 Based on the Radiolucent Gap: Comparison With Polyether-Ether-Ketone

2021 ◽  
Vol 8 ◽  
Author(s):  
Jianxiao Li ◽  
Haitao Peng ◽  
Zhiyu Chen ◽  
Chenbo Hu ◽  
Tao He ◽  
...  
Keyword(s):  
Spinal Fusion ◽  
Histological Analysis ◽  
Early Stage ◽  
Polyamide 66 ◽  
Implant Surface ◽  
Bone Implant ◽  
X Ray ◽  
Polyether Ether Ketone ◽  
Ether Ketone ◽  
Push Out

Spinal fusion cages have been used in spinal fusion surgery for over 20 years. Polyether-ether-ketone (PEEK) cages are one of the most widely used materials. However, an increasing number of clinical and preclinical studies have shown that as a bioinert material the PEEK cage causes implant failure owing to limited osseointegration. The most common complication is a radiolucent zone at the bone-implant interface. Nanohydroxyapatite/polyamide 66 (n-HA/PA66) is a bioactive composite with sufficient load-bearing properties and good osseointegration abilities. However, in the early stage after surgery, a radiolucent gap can also be observed at the margin of the bone-implant interface. To better assess osseointegration performance as a fusion cage and compare the radiolucent gaps between the two materials, PEEK and n-HA/PA66, implants were prepared and implanted into the femoral condyles of adult New Zealand white rabbits to create a line-to-line bone-implant interface model. The interfaces were systematically investigated using X-ray radiography, histological analysis, scanning electron microscopy (SEM), elemental mapping analysis, micro-computed tomography evaluation, and push-out tests at 4, 8, 12, 24, and 52 weeks. Analysis of X-ray films and histological sections indicated a radiolucent gap around the margin of n-HA/PA66 in the early weeks after implantation (4–8 weeks). The gap narrowed and decreased gradually at 24–52 weeks. Histological analysis and SEM suggested that the formed bone could integrate and adhere in some regions of the implant surface. In addition, a better bone-like apatite layer was formed between the bone and the n-HA/PA66 implant interface than with the PEEK implant. Push-out tests conducted at 24 and 52 weeks to evaluate integrated strength showed that the n-HA/PA66 implants have better bonding strength and sufficient stability, whereas PEEK implants possess poor integrated strength. Therefore, the n-HA/PA66 composite exhibits good osseointegration properties and an improved integrated bone-implant interface.

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