Effect of ta additions on the microstructure, damping, and shape memory behaviour of prealloyed Cu-Al-Ni shape memory alloys

The influence of Ta additions on the microstructure and properties of Cu-Al-Ni shapememory alloys was investigated in this paper. The addition of Ta significantly affects the green and porosity densities; the minimum percentage of porosity was observed with the modified prealloyed Cu-Al-Ni-2.0wt.% Ta. The phase transformation temperatures were shifted towards the highest values after Ta was added. Based on the damping capacity results, the alloy of Cu-Al-Ni-3.0 wt.% Ta has very high internal friction with the maximum equivalent internal friction value twice as high as that of the prealloyed Cu-Al-Ni SMA. Moreover, the prealloyed Cu-Al-Ni SMAs with the addition of 2.0wt.% Ta exhibited the highest shape recovery ratio in the first cycle (i.e., 100% recovery), and when the number of cycles is increased, this ratio tends to decrease. On the other hand, the modified alloys with 1.0 and 3.0 wt.% Ta implied a linear increment in the shape recovery ratio with increasing number of cycles. Polarization tests in NaCl solution showed that the corrosion resistance of Cu-Al-Ni-Ta SMA improved with escalating Ta concentration as shown by lower corrosion current densities, higher corrosion potential, and formation of stable passive film

Electrospun Nano-fibers for biomedical and tissue engineering applications: A comprehensive review

Pharmaceutical nano-fibers have attracted widespread attention fromresearchers for reasons such as adaptability of the electro-spinning process and ease of production. As a flexible method for fabricating nano-fibers, electro-spinning is extensively used. An electro-spinning unit is composed of a pump or syringe, a high voltage current supplier, a metal plate collector and a spinneret. Optimization of the attained nano-fibers is undertaken through manipulation of the variables of the process and formulation, including concentration, viscosity, molecular mass, and physical phenomenon, as well as the environmental parameters including temperature and humidity. The nano-fibers achieved by electro-spinning can be utilized for drug loading. The mixing of two or more medicines can be performed via electro-spinning. Facilitation or inhibition of the burst release of a drug can be achieved by the use of the electro-spinning approach. This potential is anticipated to facilitate progression in applications of drug release modification and tissue engineering (TE). The present review aims to focus on electro-spinning, optimization parameters, pharmacological applications, biological characteristics, and in vivo analyses of the electro-spun nano-fibers. Furthermore, current developments and upcoming investigation directions are outlined for the advancement of electro-spun nano-fibers for TE. Moreover, the possible applications, complications and future developments of these nano-fibers are summarized in detail. © 2020 by the authors

Drug release, cytocompatibility, bioactivity, and antibacterial activity of doxycycline loaded Mg-Ca-TiO2 composite scaffold

Mg-Ca-TiO2 (MCT) composite scaffolds loaded with different concentrations of doxycycline (DC) with a network of interconnected pores with good compressive strength (5 ± 0.1 MPa) were fabricated via space holder method for the first time. The results showed that MCT-DC scaffolds possess a porosity and pore size in the range of 65–67% and 600–800 μm respectively. The bioactivity results exhibited the apatite formation on the MCT-DC scaffold surface, indicating that DC did not obstruct the bioactivity of MCT. The MCT-DC scaffolds drug release profiles show the initial burst and sustained drug release (55–75%) and the release rate could be adjusted via altering the DC concentration. The MCT loaded with 1 and 5% DC did not indicate cytotoxic behavior against MG63 cells while further DC loading resulted in some toxicity. Antimicrobial properties of MCT-DC scaffolds against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria were examined and the results reveal oblivious inhibition zone around each MCT-DC scaffold whereas no obvious inhibition is observed around the MCT scaffold. Therefore, MCT-DC composite scaffolds with low concentration of DC could be alternative candidates for infection prevention and bone tissue engineering

Antioxidant, antimicrobial and antiviral properties of herbal materials

Recently, increasing public concern about hygiene has been driving many studies to investigate antimicrobial and antiviral agents. However, the use of any antimicrobial agents must be limited due to their possible toxic or harmful effects. In recent years, due to previous antibiotics’ lesser side effects, the use of herbal materials instead of synthetic or chemical drugs is increasing. Herbal materials are found in medicines. Herbs can be used in the form of plant extracts or as their active components. Furthermore, most of the world’s populations used herbal materials due to their strong antimicrobial properties and primary healthcare benefits. For example, herbs are an excellent material to replace nanosilver as an antibiotic and antiviral agent. The use of nanosilver involves an ROS-mediated mechanism that might lead to oxidative stress-related cancer, cytotoxicity, and heart diseases. Oxidative stress further leads to increased ROS production and also delays the cellular processes involved in wound healing. Therefore, existing antibiotic drugs can be replaced with biomaterials such as herbal medicine with high antimicrobial, antiviral, and antioxidant activity. This review paper highlights the antibacterial, antiviral, and radical scavenger (antioxidant) properties of herbal materials. Antimicrobial activity, radical scavenger ability, the potential for antimicrobial, antiviral, and anticancer agents, and efficacy in eliminating bacteria and viruses and scavenging free radicals in herbal materials are discussed in this review. The presented herbal antimicrobial agents in this review include clove, portulaca, tribulus, eryngium, cinnamon, turmeric, ginger, thyme, pennyroyal, mint, fennel, chamomile, burdock, eucalyptus, primrose, lemon balm, mallow, and garlic, which are all summarized. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

In vitro and in vivo evaluation of chitosan-alginate/gentamicin wound dressing nanofibrous with high antibacterial performance

Wound dressings based on nanofiber polymer scaffolds with good antimicrobial performance and skin reconstruction ability are promising options to thwart wound infection and accelerate wound healing. This paper reports on the synthesis via electrospinning of chitosan-alginate (CS-Alg) nanofiber dressings with various amounts of gentamicin (Gn; 0–10 wt%) as a drug delivery system. Smooth and continuous nanofibers with no obvious beads were created, with increases in the amount of Gn resulting in reduced fiber diameter. Antimicrobial tests showed the Gn-loaded nanofibers had good antibacterial performance as indicated by the inhibition of bacterial growth. CS-Alg nanofibers loaded with higher Gn concentrations exhibited greater antibacterial performance than those with lower Gn concentrations. In vitro cell culture studies demonstrated that CS-Alg wound dressings with 1–3% Gn improved L929 cell attachment and proliferation more than wound dressings with higher Gn concentrations. In vivo experiments revealed that Cs-Alg nanofibers loaded with 3% Gn significantly enhanced skin regeneration in a Balb/C mice model by stimulating the formation of a thicker dermis, increasing collagen deposition, and increasing the formation of new blood vessels and hair follicles. Collectively, Gn-loaded CS-Alg wound dressings can be considered a good candidate for drug delivery systems and skin regeneration applications. © 2019 Elsevier Lt

Magnesium-based nanocomposites: A review from mechanical, creep and fatigue properties

The addition of nanoscale additions to magnesium (Mg) based alloys can boost mechanical characteristics without noticeably decreasing ductility. Since Mg is the lightest structural material, the Mg-based nanocomposites (NCs) with improved mechanical properties are appealing materials for lightweight structural applications. In contrast to conventional Mg-based composites, the incorporation of nano-sized reinforcing particles noticeably boosts the strength of Mg-based nanocomposites without significantly reducing the formability. The present article reviews Mg-based metal matrix nanocomposites (MMNCs) with metallic and ceramic additions, fabricated via both solid-based (sintering and powder metallurgy) and liquid-based (disintegrated melt deposition) technologies. It also reviews strengthening models and mechanisms that have been proposed to explain the improved mechanical characteristics of Mg-based alloys and nanocomposites. Further, synergistic strengthening mechanisms in Mg matrix nanocomposites and the dominant equations for quantitatively predicting mechanical properties are provided. Furthermore, this study offers an overview of the creep and fatigue behavior of Mg-based alloys and nanocomposites using both traditional (uniaxial) and depth-sensing indentation techniques. The potential applications of magnesium-based alloys and nanocomposites are also surveyed

Relationship between the corrosion behavior and the thermal characteristics and microstructure of Mg-0.5Ca-Xzn alloys

Effects of secondary phases on corrosion behaviour of the Mg-0.5Ca-xZn alloys were investigated by polarization, immersion and hydrogen evolution tests. The Mg 2Ca phase nucleated at 520°C while, Ca 2Mg 6Zn 3 and Mg 51Zn 20 phases were formed at 420°C and 330°C respectively. The corrosion resistance of Mg-0.5Ca alloy was enhanced with the addition of Zn up to 1%, while further addition reversed the effect. The Mg-0.5Ca-1Zn alloys with (α-Mg+Ca 2Mg 6Zn 3+Mg 2Ca) phase showed lower corrosion rate than the alloys with (α-Mg+Ca 2Mg 6Zn 3) and (α-Mg+Ca 2Mg 6Zn 3+Mg 51Ca 20) phases. The amount of corrosion product, composed of Mg(OH) 2 and hydroxyapatite on the surface of the alloy, increased with increasing Zn content

Relationship between the microstructure and the heat treatment and creep behavior of fe-33ni-19cr alloy

In the present study, the relationship between heat treatment, grain size, and the creep rupture properties of Fe–33Ni–19Cr alloy was investigated. The microstructure analysis showed that Fe–33Ni–19Cr alloy consists of the austenite phase matrix and a small number of precipitates such as titanium nitride and titanium carbides. Fe–33Ni–19Cr alloy shows an increase in steady-state creep rate with increased grain size from 94 to 381 μm, due to the grain boundary sliding mechanism. The result also exhibited that the alloy that was subjected to creep test failed in ductile mode and cavitation at the grain boundaries. The fracture surface shows a transgranular fracture but an intergranular fracture at the recrystallized grains at the fracture area. Taken together, the result exhibited that the Fe–33Ni–19Cr alloy subjected lower heat treatment temperature possess a smaller grain size, which led to better creep property along with more excellent service life during operation

Functionalized carbon nanotube-encapsulated magnesium-based nanocomposites with outstanding mechanical and biological properties as load-bearing bone implants

Magnesium (Mg)-based composites have recently been studied as biodegradable material for the fabrication of orthopedic implants. Nevertheless, in physiological environments, proper mechanical properties and sufficient degradation rate are needed. In this paper, zinc (Zn) was uniformly distributed in the magnesium matrix using a ball milling process, and then the composite of Mg-3Zn/xfCNTs (x = 0, 0.2, 0.4, and 0.8 wt%) was successfully fabricated using a combination of semi-powder metallurgy, sintering and extrusion processes for use as a biodegradable load-bearing implant. The influence of functionalized carbon nanotubes (fCNTs) content on compressive strength, corrosion behavior and in vitro bioactivity (apatite formation ability and cytocompatibility) of the composite was investigated. The key toughening mechanisms that resist crack propagation include fCNTs pull-out, grain bridging by fCNTs, Crack branching and crack deflection. Furthermore, electrochemical and in-vitro immersion studies demonstrated that the corrosion behavior of Mg-3Zn composite under high concertation encapsulation was slightly reversed by fCNTs. Furthermore, cell culture investigations revealed that MG-63 cells present high level of cell viability and proliferate, implying that Mg-3Zn/0.4fCNTs composites are cytocompatible. All the findings suggest that the Mg-3Zn/0.4fCNTs composite with outstanding mechanical properties and appropriate corrosion resistance and biocompatibility may be a potential candidate for biodegradable implant application. © 2021 The Author

Microstructure and corrosion behaviour of Cu-Al-Ni shape memory alloys with Ag nanoparticles

In this study, the effect of silver nanoparticles on the transformation temperatures, microstructural and corrosion characteristics of the ternary Cu-Al-Ni shape memory alloys (SMA) was investigated. It was subsequently observed that the addition of Ag nanoparticles controlled the phase morphology and orientations of the parent phases, along with the formation of the Ag-rich precipitates. Furthermore, it was shown that the addition of Ag nanoparticles can affect the martensitic transformation temperature, due to the microstructure changes that are associated with the formation of intermetallic compounds and/or precipitates. The corrosion behaviour of the Cu-Al-Ni shape memory alloy with and without nano-Ag addition were investigated using electrochemical tests in a NaCl solution, and their results showed that the corrosion potential of Cu-Al-Ni-Ag (nanoparticles) SMA (-277.1 mVSCE) was nobler than the Cu-Al-Ni SMA. It was also shown that there is a decline in corrosion current density from 6.93 to 5.61 μA/cm2 after the addition of nano-Ag to Cu-Al-Ni SMA. The combination of SEM, together with EDX and XRD, also showed that the formation of the corrosion products silver chloride, cuprous oxide, aluminium oxide/hydroxide and silver oxide act as a protective layer and improve the corrosion resistance of Cu-Al-Ni-Ag SMA