Influence of shock waves on structural and morphological properties of copper oxide NPs for aerospace applications
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The present work is focused on stability of shock wave-exposed copper oxide (CuO) nanoparticles. CuO nanoparticles are synthesized by chemical reduction method and exposed to 100 shock pulses having Mach number 2.4. The table top semiautomatic pressure-driven shock tube is used to generate shock waves for the present experiment. The influence of shock waves on the treated and untreated CuO nanoparticles are explored and characterized by a variety of properties like structural, molecular and morphological details observed using powder XRD, FTIR and SEM, respectively. The powder XRD profile confirmed that there are no lattice defects or any deformation except negligible changes in grain size. SEM images established that the shock wave-loaded CuO nanoparticles have good structural and morphological stability. The obtained results showed that CuO nanoparticles can be used in aerospace, nuclear reactors and high-pressure applications which undergo extreme conditions. The details are presented intensely in the following sections.
KeywordsCuO nanoparticles Shock wave Shock tube Structural stability Grain size
In recent years, metal oxide nanoparticles (NPs) like copper oxide, titanium oxide, zinc oxide, etc., are most abundantly used in numerous potential applications, viz., catalysts, solar cell technology, batteries, drug delivery, anti bacterial activity and electronic devices due to their spectacular structural and optical properties [1, 2]. Copper oxide is a P-type semiconductor material which can be effortlessly obtained by the oxidation of Cu and extensively used for many applications [3, 4]. Though metal oxides have very good physical properties in the ambient condition, the mechanical stability and structural stability of the materials are uncertain when they are used in aerospace and nuclear reactor which undergo extreme environmental conditions such as high dynamic pressure and temperature. Thus, the investigations on properties of materials under intense circumstances are very much essential for the device fabrication of such applications . Shock wave is a nonlinear high-pressure phenomena and it has high dynamic pressure and temperature. Producing this sort of shock waves is possible in the laboratory by using shock tubes. When materials are exposed to shock waves, it provides uniaxial stress and makes significant changes in the material properties. The changes occurred in the materials are mainly associated with the structural and crystalline nature of the material. In the last decade, shock wave recovery experiments get significant attractions in material science and structural engineering applications. Shock wave recovery study is very simple and efficient method to examine the material properties in extreme conditions such as dynamic high pressure and temperature. Many of the recent publications show the significant importance of the shock wave recovery experiments in material science branch especially in nano-sized particles [6, 7, 8]. To show the significance of shock recovery experiments, few examples of recent reports are listed below. Brontvein et al.  utilized shock waves as a growth promoter to synthesize two-step MoS2 nano-tubes with argon as driver gas and phase transformation was demonstrated in fluorite CeO5CrO·5O2+x under shock wave-loaded conditions . Cubic zirconia showed unstable electronic structure and crystalline structure and CeO2 showed the stable physical properties in shock wave-loaded conditions [11, 12]. In shock wave-loaded conditions, lot of pores and cracks were developed in diverse sizes on the surface of CeO2 and the formation of CeO2−xNx are confirmed when strong shock waves interacted with CeO2 ceramic material in the presence of O2 and N2 gases . Nano-crystalline SiC ceramics showed a distinct change on elastic nature and also transitional plastic structural phase transformation was observed while plane shock wave loaded on it . Cu foams with open cell nanoporus showed remarkable effects of relative mass density and specific surface area by the expose of temperature shock . High shock absorptions and negligible changes in density distribution of particles were observed in silica aerogel under shock compressions . The overview of literature studies showed that shock waves can alter the structural, electrical, morphological and optical properties of materials. The present investigation is aimed to understand the stability of the structure and morphology of prepared CuO NPs under shock wave-exposed conditions. The interesting aspects of the behaviour of shock wave treated and untreated CuO NPs are discussed in the following sections.
Synthesis of CuO NPs
Loading of shock waves
Results and discussion
FTIR spectroscopic analysis
No significant changes seen in FTIR spectra of shock wave treated and untreated CuO NPs by the influence of shock waves. The reproducibility of the characteristic bends at 622 cm−1 and 513 cm−1 shows the spectacular molecular structure stability of the CuO NPs. Hence, we could confirm that CuO NPs have higher molecular stability against the impact of shock waves.
Powder X-ray diffraction
Structural parameters of the shock wave treated and untreated CuO NPs
Predominant peak (404) position (2θ)
Grain size (nm)
Dislocation density (× 1015 lines/m2)
Lattice strain (%)
Untreated CuO NPs
Treated CuO NPs
Also XRD profile reveals that the applied shock waves do not introduce any deformation, lattice distortion and lattice defects in the CuO NPs crystalline system. It confirms that CuO NPs are more stable material as compared to few metal oxide NPs such as TiO2, ZrO2 [11, 18, 19]. The lattice stress and stress hardening are also calculated from standard Williamson–Hall method  and the calculated structural parameters of the shock wave treated and untreated CuO NPs are listed in Table 1. The insignificant changes in lattice strain and strain hardening due to the plastic deformation of CuO NPs show the sustainability of the crystalline system of the CuO NPs on loadings of shock waves. The advanced structural stability of the CuO NPs may be due to the lower bond length and higher ionic bond attraction between Cu2+ and O2−. The results suggest that the prepared CuO NPs are well appropriate material for extreme surroundings like dynamic high temperature and pressure so as to be used in the aerospace and nuclear reactor applications.
Nanoparticles of copper oxide have been effectively synthesized using chemical reduction method and then the synthesized copper oxide nanoparticles were treated with 100 shock pulses having Mach number of 2.4. FTIR spectral analysis confirms the vibration modes of CuO NPs. The powder XRD analysis confirmed that synthesized CuO NPs belong to orthorhombic crystalline system and proved its impressive structural and mechanical stability under shock wave-loaded conditions. SEM images clearly show that there is no significant morphological changes occurred in the shock-exposed sample except some negligible differences in surface area of the CuO NPs. Hence, with these results one can conclude that the synthesized CuO NPs have greater structural stability and highly stable morphology. From these investigations, authors suggest that CuO NPs can be used in extreme conditions such as high dynamic pressure and temperature, nuclear reactors and aerospace applications.
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