Materials Today Chemistry
Impact of shock waves on the physical and chemical properties of aligned zinc oxide structures grown over metal-sheets
Graphical abstract
Slantly overlapped zinc oxide nanorods structures developed on flexible stainless steel sheets exhibited excellent stability under dynamically generated high temperature and pressure shock waves. At the same time, the physical and chemical properties of these nanorods are more significant than that of the structures grown over glass substrates.
Introduction
Materials science is one of the crucial branches in space engineering technology where the materials have been synthesized, processed, and tested for different applications [1,2]. The reduction of weight and cost of the materials along with the enhancement of specific device functionalities are a few key issues that have received great focus today [[3], [4], [5]]. State-of-the-art in space engineering reports suggests that most of these bottleneck problems can be handled by developing new class materials [6]. Noticeably, the primary selection of materials is determined by their mechanical and physical properties along with chemical characteristics [[7], [8], [9]]. In this direction, the combination of various kinds of materials has been adapted for different space engineering applications including electrical and electronics, sensors, controllers, detectors, protection, and energy conversion and storage devices since it is impossible to achieve all these applications by using a single material [10]. Though there are plenty of high-temperature materials with melting temperatures higher than 2000 °C including carbides, refractory metals, oxides, nitrides, and borides, the ceramic materials have received considerable attention due to their multifunctional characteristics along with considerable sustainability even under extreme temperatures or harsh operating conditions [11]. At the same time, these compound materials possess significant mechanical strength along with suitable optical and electrical properties. As a result, different kinds of devices have been developed and tested for various space applications including leak detection, temperature monitoring, emissions monitoring, and fluctuations in the surrounding environment.
In recent years, the development of materials with nanoscale dimensions by adopting advanced processing methodologies allows scientists to realize efficient and eco-friendly devices not only for day-to-day applications but also for space engineering and medical applications [12]. As a result, various semiconductor materials-based devices have been projected as potential candidates for different space engineering applications [11]. In this direction, zinc oxide (ZnO), a ceramic material, has received great attention as a suitable material for high-temperature and high power electronic devices [13,14]. Basically, ZnO is a highly transparent wide bandgap semiconductor material and possesses multifunctional characteristics [15] and a high melting temperature (∼2000 °C) [16], which is comparable to or higher than that of other materials (like Ti, SiN, AlN, etc.) presently adopted in space applications. As a result, ZnO nanostructures have been well developed with different morphologies by adopting various low-temperature techniques. For instance, ZnO nanowires were obtained by hydrothermal growth [[17], [18], [19], [20]], whereas nanoparticles like structures were produced by the same approach at lower temperatures [[21], [22], [23]]. On the other hand, the same methodology has been adopted to realize other types of nanostructures as well [[24], [25], [26], [27]]. In this regard, multifunctional applications of ZnO nanorods and their unique characteristics motivated us to shed light on the synthesis of ZnO nanorods by a simple and cost-effective process and study their thermal stability characteristics under dynamically created harsh environments.
Herein, the ZnO nanorods were developed over the glass as well stainless steel (SS) substrates, and their physical and chemical characteristics were investigated and comparatively explored. Then, the sustainability of ZnO nanorods was investigated by exposing them to dynamically generated shock waves in a free piston-driven shock tube (FPST), as reported elsewhere in detail [28]. From these studies, it is demonstrated that the structures grown over stainless sheet substrates exhibited excellent stability for the shock waves generated with a temperature and pressure of ∼20,000 K and ∼6 MPa. A key point for the sustainable characteristics of ZnO nanorods is their slantly overlapped morphology.
Section snippets
Chemicals and materials
In these studies, glass and SS sheets (1.25 mm thickness) were used as substrates. Zinc nitrate hexahydrate (Zn(NO3)2·6H2O, Sigma-Aldrich), Hexamethylenetetramine (C6H12N4, Sigma-Aldrich), and deionized water (Milli-Q grade) were used without any further purification.
Growth of ZnO nanorods
ZnO nanorods were grown in two steps: i) Seeding of glass and SS substrates by spray pyrolysis (SP) and ii) Growth of ZnO nanorods by chemical bath deposition (CBD) method, which is schematically presented in Fig. 1. Initially,
Results and discussion
The surface morphology of the as-grown ZnO nanorods over the glass and SS substrates studied by FESEM is shown in Fig. 2. The structures grown over both substrates possess hexagonal-shaped nanorods structures. However, the nanorods grown over glass possess uniform dimensions, whereas the structures on SS have varied dimensions. At the same time, the nanorods grown on glass substrates are vertically aligned, whereas the structures on SS are slantly oriented and also cross-linked (or overlapped),
Conclusions
In view of the multifunctional characteristics of ZnO, we have developed ZnO nanorods on SS sheets and compared their physical and chemical properties with the structures developed on glass substrates. Finally, the sustainability of ZnO nanorods developed SS substrates were studied by exposing them to high energy shock waves produced with a temperature and pressure of ∼20, 000 K and ∼6 MPa for the duration of 2–3 ms. As compared to the structures grown on the glass substrates, the structures
CRediT authorship contribution statement
DM and KRN designed, planned, and executed the project. Summarizing the results and script-writing are done by KRN, DM, and RMRL. KPJR and SL provided constructive suggestions by editing and reviewing the manuscript.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
SWL acknowledges the financial support of the National Research Foundation of Korea with grant number 2018R1A5A1025511.
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