Magnesium alloys take a special place among the hydrogen storage materials, mainly due to their high gravimetric (7.6 mass %) and volumetric (110 kg m−3) hydrogen storage capacity. Unfortunately, the ...kinetics of hydrogenation and hydrogen release are rather slow, which limits practical use of magnesium-based materials for hydrogen and heat storage. Refining the microstructure of magnesium alloys, ideally down to nanoscale, is known to accelerate the hydrogenation/dehydrogenation kinetics. A possible way to achieve that is by severe plastic deformation. Our first demonstration of this effect through processing of a Mg alloy (ZK60) by equal-channel angular pressing prompted a stream of further studies employing severe plastic deformation techniques to improve the hydrogen storage-relevant properties of Mg alloys. The present article provides an overview of the literature on the subject, with a natural focus on our own data.
The increase in awareness of the damage caused by synthetic materials on the environment has led to the development of eco-friendly materials. The researchers have shown a lot of interest in ...developing such materials which can replace the synthetic materials. As a result, there is an increase in demand for commercial use of the natural fiber-based composites in recent years for various industrial sectors. Natural fibers are sustainable materials which are easily available in nature and have advantages like low-cost, lightweight, renewability, biodegradability, and high specific properties. The sustainability of the natural fiber-based composite materials has led to upsurge its applications in various manufacturing sectors. In this paper, we have reviewed the different sources of natural fibers, their properties, modification of natural fibers, the effect of treatments on natural fibers, etc. We also summarize the major applications of natural fibers and their effective use as reinforcement for polymer composite materials.
Machine learning tools represent key enablers for empowering material scientists and engineers to accelerate the development of novel materials, processes and techniques. One of the aims of using ...such approaches in the field of materials science is to achieve high-throughput identification and quantification of essential features along the process-structure-property-performance chain. In this contribution, machine learning and statistical learning approaches are reviewed in terms of their successful application to specific problems in the field of continuum materials mechanics. They are categorized with respect to their type of task designated to be either descriptive, predictive or prescriptive; thus to ultimately achieve identification, prediction or even optimization of essential characteristics. The respective choice of the most appropriate machine learning approach highly depends on the specific use-case, type of material, kind of data involved, spatial and temporal scales, formats, and desired knowledge gain as well as affordable computational costs. Different examples are reviewed involving case-by-case dependent application of different types of artificial neural networks and other data-driven approaches such as support vector machines, decision trees and random forests as well as Bayesian learning, and model order reduction procedures such as principal component analysis, among others. These techniques are applied to accelerate the identification of material parameters or salient features for materials characterization, to support rapid design and optimization of novel materials or manufacturing methods, to improve and correct complex measurement devices, or to better understand and predict fatigue behavior, among other examples. Besides experimentally obtained datasets, numerous studies draw required information from simulation-based data mining. Altogether, it is shown that experiment- and simulation-based data mining in combination with machine leaning tools provide exceptional opportunities to enable highly reliant identification of fundamental interrelations within materials for characterization and optimization in a scale-bridging manner. Potentials of further utilizing applied machine learning in materials science and empowering significant acceleration of knowledge output are pointed out.
In this review, we discuss microbiological and molecular concepts of Microbially Induced Calcium Carbonate Precipitation (MICP) and their role in bioconcrete. MICP is a widespread biochemical process ...in soils, caves, freshwater, marine sediments, and hypersaline habitats. MICP is an outcome of metabolic interactions between diverse microbial communities with organic and/or inorganic compounds present in the environment. Some of the major metabolic processes involved in MICP at different levels are urea hydrolysis, denitrification, dissimilatory sulfate reduction, and photosynthesis. Currently, MICP directed by urea hydrolysis, denitrification, and dissimilatory sulfate reduction has been reported to aid in the development of bioconcrete and has demonstrated an improvement in the mechanical and durability properties of concrete. Bioconcrete is a promising sustainable technology which reduces negative environmental impact caused by CO2 emissions from the construction sector, as well as in terms of economic benefits by way of promoting a self-healing process of concrete structures. Among the metabolic processes mentioned above, urea hydrolysis is the most applied in concrete repair mechanisms. MICP by urea hydrolysis is induced by a series of reactions driven by urease (Ur) and carbonic anhydrase (CA). Catalytic activity of these two enzymes depends on diverse parameters, which are currently being studied under laboratory conditions to better understand the biochemical mechanisms involved and their regulation in microorganisms. It is clearly evident that microbiological and molecular components are essential to improving the process and performance of bioconcrete.
Substances at nanoscale, commonly known as “nanomaterials,” have always grabbed the attention of researchers for hundreds of years. Among these different types of nanomaterials, magnetic ...nanomaterials have been the focus of considerable attention during the last two decades as evidenced by an unprecedented increase in the number of research papers focusing these materials. Iron oxide magnetic nanoparticles have occupied a vital position in imaging phenomena; as drug vehicles, controlled/sustained release phenomena and hyperthermia; atherosclerosis diagnosis; prostate cancer. In fact, these are wonderful “theranostic” agents with some under clinical trials for human use. In this review, we have attempted to highlight the advances taking place in the field of magnetic nanoparticles as theranostic agents. Extensive progress has been made in the two most important parameters, namely, control over the size and shape which decide the importance of iron oxide magnetic nanoparticles by developing suitable procedures like precipitation, co-precipitation, thermal decomposition, hydrothermal synthesis, microemulsion synthesis and plant mediated synthesis. After using a suitable synthetic route, workers encounter the most daunting task linked with the materials at nanoscale i.e., the protection against corrosion. Only properly protected iron oxide magnetic nanoparticles can be further connected to different functional systems to make building blocks for application in catalysis, biology and medicines. Finally, “theranostics” which is a combined application of imaging and drug delivery has been discussed. With all the potential uses, toxicity of the of iron oxide magnetic nanoparticles has been discussed.
Carbon quantum dots (CQDs) are a new type of nano-carbons that are currently favored over semiconductor quantum dots (QDs) because of their solubility, low toxicity, eco-friendliness, and cheap and ...facile synthesis giving desired optical characteristics. Moreover, their physiochemical properties can be controlled by their synthetic route. CQDs can emit fluorescence in the range from the UV to the near-infrared (NIR) region, making them suitable for biomedical applications. Fluorescence in these nano-carbon atoms can be tuned by varying the excitation wavelength. As of now, CQDs have been used in various applications such as in bioimaging, biosensing, electrochemical biosensing, drug delivery, gene delivery, photodynamic therapy in the treatment of cancers, pharmaceutical formulations, and treating inflammation. This article highlights the current progress and advancement of CQDs with focus on their synthetic routes, chemical and optical properties, and biomedical applications along with new perceptions in this interesting and promising field.
Chemically activated materials (often termed as geopolymer) have received attracting attentions in civil, material and environmental research fields as a toolkit alternative to traditional Portland ...cement in specific applications. This paper presents a comparative review on silico-aluminophosphate (SAP) geopolymers in terms of definition, chemistries involved during geopolymerization, mechanical performance, durability, environmental impacts, and their potentials in applications relative to conventional alkali-aluminosilicate (AAS) geopolymers. Recommendations for future applications are also highlighted. It is found that S-A-P gels with six-coordinated aluminum environment dominate in SAP geopolymers, while the aluminum in N-A-S-H gels formed in the AAS geopolymers is characterized by four-coordinated features. Besides, the slow performance development of SAP geopolymer matrix under ambient temperature curing can be compensated through incorporating additional countermeasures (e.g., metal sources) which allow the tailored design of such geopolymers for certain in-situ applications. Generally, the calcium-bearing C-(A)-S-H gels co-existing with N-A-S-H gels are dominant in AAS geopolymers, while the S-A-P gels enhanced by phosphate-containing crystalline/amorphous phases are the main products in SAP geopolymers. The SAP geopolymers show their environmental friendliness relative to the AAS geopolymers due to the utilization of phosphate activators that require lower production energy relative to silicate-containing activators. However, the higher cost of phosphate activators may confine the applications of SAP geopolymers in some exquisite or special fields.
Hydroxyapatite (HAp) has been considered for decades an ideal biomaterial for bone repair due to its compositional and crystallographic similarity to bioapatites in hard tissues. However, fabrication ...of porous HAp acting as a template (scaffold) for supporting bone regeneration and growth has been a challenge to biomaterials scientists. The introduction of additive manufacturing technologies, which provide the advantages of a relatively fast, precise, controllable, and potentially scalable fabrication process, has opened new horizons in the field of bioceramic scaffolds. This review focuses on three-dimensional-printed HAp scaffolds and related composite systems, where the calcium phosphate phase is combined with other ceramics or polymers improving the mechanical properties and/or imparting special extra-functionalities. The main applications of three-dimensional-printed HAp scaffolds in bone tissue engineering are presented and discussed; furthermore, this review also emphasizes the most recent achievements toward the development and testing of multifunctional HAp-based systems combining multiple properties for advanced therapy (e.g., bone regeneration, antibacterial effect, angiogenesis, and cancer treatment).
As a novel biodegradable material, poly (vinyl) alcohol (PVA)/starch (ST)/ glycerol (GL)/ halloysite nanotube (HNT) nanocomposite films were prepared by solution casting at the HNT contents of 0.25, ...0.5, 1, 3, and 5 wt%. Water absorption capacity and water solubility of nanocomposite films were decreased remarkably by 44.24 and 48.05%, respectively, with increasing the HNT content from 0 to 5 wt% when compared with those of biopolymer matrices. Moreover, the water contact angle of nanocomposite films increased by 21.36° with the incorporation of HNTs. The presence of HNTs appeared to reduce the overall migration rates for PVA/ST/GL/HNT nanocomposite films when interacting with either hydrophilic or lipophilic food simulants. However, the migration rates of HNTs alone were enhanced with increasing the HNT content in hydrophilic, lipophilic, and acidic food simulants. On the other hand, the biodegradation rate and light transmittance of nanocomposite films were reduced linearly by 18.56 and 26.90% with increasing the HNT content from 0 to 5 wt%. Overall, novel PVA/ST/GL/HNT nanocomposite films in this study offer highly competitive materials with excellent water resistance, good biodegradability, and acceptable transparency to be potentially used for sustainable food packaging particularly targeting lipophilic and acidic foodstuffs.
As an emerging energy storage device, the supercapacitor with high energy density, fast charging/discharging, and good cycle stability has aroused great interest. The performance of supercapacitors ...mainly depend on the electrode material. Manganese dioxide (MnO2) has emerged as one of the most promising electrode materials for high theoretical specific capacitance, wide potential range, high electrochemical activity, and environmental friendliness. However, its deteriorated volume expansion and inherently low conductivity limit its development and application in supercapacitors. To circumvent the mentioned issues, the porous, thin film, or layered composite materials were prepared to enhance the electrical conductivity and specific surface area of MnO2. Carbon materials are the ideal choice to compound with MnO2 owing to their low electrical resistance, significant thermal stability, large specific surface area, and porosity. Up to now, several kinds of MnO2/carbon composites as supercapacitor electrodes have been designed and fabricated. Herein, we give a concise review of the latest researches on MnO2/carbon supercapacitor electrodes, focusing on the fabrication strategies and analyzing the influencing factors of electrochemical performance of MnO2/carbon materials. An outlook on the possible development directions in future of designing high-performance MnO2/carbon materials for the current challenges is also provided.
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