1,720,967 research outputs found
Preparation and characterization of a Novel mesoporous bioactive glass/calcium sulfate cement for vertebroplasty application
No full textVertebral compression fractures (VCFs) are deformities of the vertebral body that usually do not require an open surgical approach and are often due to osteoporosis or low energy trauma. They may be healed by themselves with a conservative management: brace support and bed rest, combined with the administration of analgesics and bisphosphonates. When the non-surgical approach is not effective, VCFs usually lead to untreatable pain, spine deformity and disability with a proven increase of mortality, especially in patients with poor conditions. Vertebroplasty and kyphoplasty are known as alternative minimal invasive approaches to VCFs. They are two percutaneous spine interventions which are performed with the goal of back pain relief and, when possible, restoring of the vertebral height. Vertebroplasty involves the injection of a bone cement through the trabeculae of the fractured vertebral body. In this procedure, cement injection is performed under continuous radiological control through a needle inserted in the vertebra by a transpedicular percutaneous approach. In kyphoplasty, a balloon tamp is inserted through a vertebroplasty needle in the fractured vertebral body and then is inflated/deflated and the created cavity is filled with the bone cement injected through a needle. In randomized trials it was found that VP and KP are equally safe and significantly superior to conservative treatment. Injectable bone cements play a critical role in the effectiveness of vertebroplasty and kyphoplasty. Regarding the bone replacement, several investigations have been focused on the materials exhibiting good bioactivity, biodegradability and biocompatibility. Injectable bone cements can be divided into various categories. The first group is polymer based cements which show unique properties due to their flexibility of composition. However, their poor mechanical strength limits their applications. Metals are considered as the second group that has high wear resistance, strength and ductility. However, their high rate of corrosion and low biocompatibility make them undesirable for living tissue. In addition, allergic reactions can occur due to the high diffusion of metal ions. Another group of materials are ceramics which possess generally good biocompatibility. Although these materials have resistance to corrosion and compression, they are brittle with low fracture strength. Calcium phosphate and calcium sulphate cements could be applicable as biomaterials for vertebral stabilization and augmentation. Nevertheless, their clinical applications have been limited due to some shortcomings. Currently, the number of commercial calcium sulphate-based cements is limited. Therefore, in recent years, several approaches have been proposed to develop the synthetic calcium-based bone cements. The aim of the present research was the synthesis of a mesoporous bioactive glass (MBG) by spray-drying a mild acidic aqueous synthesis solution. These particles are able to chemically bond to the bone and can be also utilized for targeted drug delivery. In order to synthesis the MBG particles, the classical methods are time-consuming due to the additional steps to obtain the final powders. Moreover, these methods are usually performed with ethanol-based solution which is flammable and expensive. Spray-drying can be considered as a single step production technique to transform a fluid feed to a dried solid powder. In fact, the spray-drying approach can be used as an effective alternative to the standard routes with faster kinetics which allows to produce the particles with controlled size and morphology. It is reported that the spray-dried mesoporous bioactive glasses or functionalized silica have been already produced by spraying synthesis solutions based on flammable solvents (mostly ethanol) under an inert atmosphere. In general, the effective procedures involve both safety and economic constraints for a future manufacturing scale-up. In this study, MBG particles were produced by the combination of sol-gel synthesis in an aqueous medium and spray-drying technique, which can be a further improvement in terms of safety, cost and environment. The second aim of this study was to develop an innovative injectable and bioresorbable composite cements based on alpha calcium sulphate hemihydrate as a resorbable matrix, enriched with mesoporous glass particles (to impart bioactivity) and a glass-ceramic radiopaque phase. The present work was in the frame of the European Union Seventh Framework Program (FP7/2007- 2013) under grant agreement no. [280575]-Restoration. During this study, the developed injectable cements were characterized in terms of physical and mechanical properties such as setting time, injectability and compressive strength. Moreover, in vitro bioactivity and degradability of prepared composite cements were assessed in simulated body fluid (SBF). Biological tests using rat bone marrow stromal cells were also carried out in vitro. In addition, further investigations were carried out in vivo by using large animal model (sheep)
A comprehensive overview of conventional and bio-based fillers for rubber formulations sustainability
Full text linkIn recent years, there has been a significant increase in literature regarding the development of sustainable rubber composites. This is due to the widespread use of rubber and the need to transition towards a circular economy, which addresses environmental concerns such as global warming and pollution. Extensive research has been conducted to replace conventional fillers like silica and petroleum-based fillers in rubber composites with eco-friendly and sustainable alternatives, namely bio-based fillers. These biofillers present diverse fundamental characteristics, making them promising substitutes for carbon black or inorganic mineral-based fillers, reducing reliance on petroleum. They possess biodegradable properties, resulting in a reduced environmental footprint, as well as lower density and cost compared to conventional counterparts. Furthermore, their unique properties, such as high specific strength and stiffness, render them well-suited for various rubber applications. The performance of reinforced rubber composites is influenced by factors including the matrix polymer, as well as the source, size, shape, chemical composition, and volume fraction of fillers. Rubber composites incorporating biofillers offer the dual advantages of economic efficiency and environmental sustainability. This article provides a comprehensive review of recent research in rubber composite development, with a specific focus on utilizing various fillers. Additionally, it examines the characterization of both conventional and bio-based fillers and their effects on the behaviour and performance of rubber composites, including morphology, thermal properties, and mechanical properties
EFFECT OF DIFFERENT PREPARATION ROUTES ON COLOR METALLOGRAPHY OF ZIRCONIUM ALLOYS BY HEAT TINTING
No full textSo as to investigate the color metallography of Zirconium alloys via heat tinting method, different grades of this alloy such as Zircaloy-4, Zr-1% Nb, Zr-2.5% Nb has been applied as a base metal. For this purpose, each sample was prepared by different preparation routes such as polishing, polishing and etching, electropolishing. On the other hand, two important parameters (temperature and time) which play a significant role in the surface quality of specimens are considered in such a way that the surface of each sample is thermally etched at temperatures of 300 and 400ºC for 15 - 30 minutes. Results show that the best route for sample preparation is polishing and etching by using an electro-polishing apparatus. Outcomes show that the best temperature of heat tinting for different samples is about 400ºC and the best time is between 15 - 20 minutes. By comparison the optical microscopic images, it can be found that the heat tinting method is not suitable for samples with superplastic deformation microstructure while for annealed samples with equiaxed microstructure shows distinct image
Green Synthesis of Metal Oxides Semiconductors for Gas Sensing Applications
Full text linkDuring recent decades, metal oxide semiconductors (MOS) have sparked more attention in various applications and industries due to their excellent sensing characteristics, thermal stability, abundance, and ease of synthesis. They are reliable and accurate for measuring and monitoring environmentally important toxic gases, such as NO(2), NO, N(2)O, H(2)S, CO, NH(3), CH(4), SO(2), and CO(2). Compared to other sensing technologies, MOS sensors are lightweight, relatively inexpensive, robust, and have high material sensitivity with fast response times. Green nanotechnology is a developing branch of nanotechnology and aims to decrease the negative effects of the production and application of nanomaterials. For this purpose, organic solvents and chemical reagents are not used to prepare metal nanoparticles. On the contrary, the synthesis of metal or metal oxide nanoparticles is done by microorganisms, either from plant extracts or fungi, yeast, algae, and bacteria. Thus, this review aims at illustrating the possible green synthesis of different metal oxides such as ZnO, TiO(2), CeO(2), SnO(2), In(2)O(3), CuO, NiO, WO(3,) and Fe(3)O(4), as well as metallic nanoparticles doping
A Comprehensive Overview on the Latest Progress in the Additive Manufacturing of Metal Matrix Composites: Potential, Challenges, and Feasible Solutions
Full text linkNowadays, as an emerging technology, additive manufacturing (AM) has received numerous attentions from researchers
around the world. The method comprises layer-by-layer manufacturing of products according to the 3D CAD models of the
objects. Among other things, AM is capable of producing metal matrix composites (MMCs). Hence, plenty of works in the
literature are dedicated to developing different types of MMCs through AM processes. Hence, this paper provides a comprehensive
overview on the latest research that has been carried out on the development of the powder-based AM manufactured
MMCs from a scientific and technological viewpoint, aimed at highlighting the opportunities and challenges of this innovative
manufacturing process. For instance, it is documented that AM is not only able to resolve the reinforcement/matrix bonding
issues usually faced with during conventional manufacturing of MMCs, but also it is capable of producing functionally
graded composites and geometrically complex objects. Furthermore, it provides the opportunity for a uniform distribution
of the reinforcing phase in the metallic matrix and is able to produce composites using refractory metals thanks to the local
heat source employed in the method. Despite the aforementioned advantages, there are still some challenges needing more
attention from the researchers. Rapid cooling nature of the process, significantly different coefficient of expansion of the
matrix and reinforcement, processability, and the lack of suitable parameters and standards for the production of defect-free
AM MMCs seem to be among the most important issues to deal with in future works
An Overview of the Recent Developments in Metal Matrix Nanocomposites Reinforced by Graphene
Full text linkTwo-dimensional graphene plateletes with unique mechanical, electrical and
thermo-physical properties could attract more attention for their employed as reinforcements
in the production of new metal matrix nanocomposites (MMNCs), due to superior characteristics,
such as being lightweight, high strength and high performance. Over the last years, due to the
rapid advances of nanotechnology, increasing demand for the development of advanced MMNCs
for various applications, such as structural engineering and functional device applications, has been
generated. The purpose of this work is to review recent research into the development in the
powder-based production, property characterization and application of magnesium, aluminum,
copper, nickel, titanium and iron matrix nanocomposites reinforced with graphene. These include a
comparison between the properties of graphene and another well-known carbonaceous reinforcement
(carbon nanotube), following by powder-based processing strategies of MMNCs above, their
mechanical and tribological properties and their electrical and thermal conductivities. The effects of
graphene distribution in the metal matrices and the types of interfacial bonding are also discussed.
Fundamentals and the structure–property relationship of such novel nanocomposites have also been
discussed and reported
An Overview of Metal Matrix Nanocomposites Reinforced with Graphene Nanoplatelets; Mechanical, Electrical and Thermophysical Properties
Full text linkTwo-dimensional graphene nanoplatelets with unique electrical, mechanical and thermophysical characteristics are considered as an interesting reinforcement to develop new lightweight, high-strength, and high-performance metal matrix nanocomposites. On the other hand, by the rapid progress of technology in recent years, development of advanced materials like new metal matrix nanocomposites for structural engineering and functional device applications is a priority for various industries. This article provides an overview of research efforts with an emphasis on the fabrication and characterization of different metal matrix nanocomposites reinforced by graphene nanoplatelets (GNPs). Particular attention is devoted to find the role of GNPs on the final electrical and thermal conductivity, the coefficient of thermal expansion, and mechanical responses of aluminum, magnesium and copper matrix nanocomposites. In sum, this review pays specific attention to the structure-property relationship of these novel nanocomposites
An aerosol-spray-assisted approach to produce mesoporous bioactive glass microspheres under mild acidic aqueous conditions
No full textA mesoporous bioactive glass in the SiO2-CaO system was obtained for the first time by spray-drying an aqueous synthesis solution under mild acidic conditions. The obtained spherical particles showed high surface area and accessible porosity. They also showed a very high bioactivity, leading to the formation of hydroxyapatite and calcite after only 24 h in simulated body fluid. The in vitro cell culture results proved that the mesoporous particles are cytocompatible and might enhance the osteogenic differentiationof bone marrow stromal cells as they increased the alkaline phosphatase activity. The final bioactive mesoporous microspheres can be dispersed in composites in order to impart a high bioactivity and may be used as targeted drug delivery system
Preparation and characterisation of an innovative injectable calcium sulphate based bone cement for vertebroplasty application
No full textAn Overview of Key Challenges in the Fabrication of Metal Matrix Nanocomposites Reinforced by Graphene Nanoplatelets
Full text linkThis article provides an overview of research efforts with an emphasis on the fabrication of metal matrix nanocomposites (MMNCs) reinforced by graphene nanoplatelets (GNPs). Particular attention is devoted to finding the challenges in the production of MMNCs through the powder metallurgy techniques. The main technical challenges can be listed as: (I) reinforcement selection; (II) dispersion of reinforcement within the matrix; (III) reactivity between the reinforcement and matrix; (IV) interfacial bonding; (V) preferred orientation of reinforcement. It is found that some of these difficulties can be attributed to the nature of the materials involved, while the others are related to the preparation routes. It is reported that the challenges related to the process can often be addressed by changing the production process or by using post-processing techniques. More challenging issues instead are related to the composition of the matrix and reinforcement, their reactivity and the dispersion of reinforcement. These topics still bring significant challenges to the materials scientists, and it would be worth mentioning that the fabrication of MMNCs with a uniform dispersion of reinforcement, strong interfacial bonding, without detrimental reactions and improved isotropic properties is still a puzzling issue
- …
