Electron Beam-Induced Atomic Migration in the Formation of Nd(OH)3 Nanostructures

Neodymium hydroxide (Nd(OH)3) has emerged as a groundbreaking compound with a wide range of applications across various industries, including catalysts, glass manufacturing, metal alloys, advanced batteries, ceramics, and more. Its unique capabilities and the significant role it plays in enhancing the performance and functionality of these products have attracted considerable interest worldwide. This is especially true due to the remarkable properties that are exhibited by nanoparticles of Nd(OH)3, which can drastically influence the efficiency and quality of the final products. The preparation methods and the significance of its applications have been the subject of extensive research and discussion. Various synthesis techniques have been developed to produce Nd(OH)3 nanoparticles, each with its own set of advantages and limitations. Among these methods are electron-beam evaporation, thermal evaporation, sol-gel auto-combustion, and hydrothermal synthesis. These methods offer different pathways to achieve nanoparticles with desired sizes, shapes, and distributions, thereby tailoring their properties for specific applications. In this study, we delve into a novel aspect of Nd(OH)3 by examining its behavior under an electron beam during in situ transmission electron microscopy (TEM) characterization [1-3]. Utilizing the innovative approach of mechanochemical methods, this study successfully synthesized neodymium hydroxide (Nd(OH)3) nanoparticles through the strategic combination of neodymium chloride (NdCl3) and sodium chloride (NaCl). This blend was carefully chosen to ensure the preservation of the Nd(OH)3 structure by conducting the process under a nitrogen atmosphere, effectively preventing any potential oxidation that could compromise the integrity of the nanoparticles. The addition of sodium served as a crucial precursor in this chemical reaction, facilitating the formation of Nd(OH)3 nanoparticles with desired properties. To ensure the purity and avoid any possible contamination of the final product, the blend underwent milling in a high-quality stainless-steel container, which was lined with Teflon. This choice of materials was deliberate, aiming to minimize the risk of introducing impurities into the nanoparticles. The milling process was executed using a SPEX 8000D Mixer/Mill®, a device renowned for its efficiency and reliability in such applications. This process extended over a period of 12 hours, during which sodium chloride also played the role of an anti-caking agent in a 5:1 ratio by weight to the blend, aiding in preventing the aggregation of particles. Following the milling process, the samples underwent a meticulous cleaning procedure. This involved washing the samples in deionized water multiple times to effectively remove any residual NaCl byproducts, a byproduct of the mechanochemical synthesis. To further ensure the cleanliness of the nanoparticles, the samples were ultrasonicated for 15 minutes, enhancing the removal of any remaining impurities. Centrifugation at 8,000 RPM for 20 minutes was then performed to separate the nanoparticles. This washing process was repeated until the pH of the solution stabilized at 7, indicating the successful removal of byproducts. An additional rinse with ethanol was conducted to prepare the samples for drying. Drying of the nanoparticles was carried out under a controlled nitrogen flow of 20 L/h, a step that ensures the removal of any remaining solvents without introducing oxidation. The samples were then stored at a temperature of -20°C to preserve their structural integrity until further analysis. To meticulously examine the morphology and structure of the synthesized Nd(OH)3 nanoparticles, transmission electron microscopy (TEM) was employed. This analysis was conducted in both low and high-resolution modes (HR-TEM) using a JEOL ARM200F microscope. This instrument, set at an acceleration voltage of 200 keV, allowed for an in-depth investigation into the nanostructures, providing valuable insights into their size, shape, and crystalline structure. This detailed characterization is essential for understanding the properties of the nanoparticles and their potential applications in various fields. The results derived from electron microscopy studies provide compelling evidence of the successful synthesis of neodymium hydroxide (Nd(OH)3) nanoparticles, forming distinctive clusters as illustrated in Figure 1a. The bright-field transmission electron microscopy (TEM) micrograph showcased in Figure 1 vividly captures the Nd(OH)3 clusters post the thorough cleaning procedure. This imagery reveals that the clusters exhibit an average length of 40 ± 5 nm, highlighting the uniformity and precision achieved through the synthesis process. Subsequently, Figure 1b marks a significant observation in the study, detailing a notable change in the morphology of the Nd(OH)3 clusters following a brief 10-second exposure to the electron beam. This transformation suggests an intriguing process of atomic reordering within the nanoparticles, potentially proceeding through two distinct phases: an initial loss of crystallinity, paving the way for a phase of recrystallization. This hypothesis gains further support from the morphological changes documented after extended exposure times of 20 and 30 seconds, as depicted in Figures 1c and 1d, respectively. These stages reveal the clusters undergoing a transformation into larger particles, a process culminating in the final stage that evidently showcases the stabilization of the crystal lattice. This progression underscores a fascinating dynamic response of the Nd(OH)3 nanoparticles to electron beam exposure, hinting at the inherent adaptability and reactivity of these particles under specific conditions. The observed morphological changes, starting from discrete clusters and evolving into larger, more stable particles, reflect a complex interplay of atomic forces and structural reconfiguration. This behavior not only sheds light on the fundamental properties of Nd(OH)3 nanoparticles but also opens up possibilities for exploring novel approaches to manipulating nanoparticle morphology and structure through controlled exposure to electron beams. Such insights are invaluable for advancing our understanding of the mechanisms driving the formation and transformation of nanomaterials [4]. Results obtained from electron microscopy demonstrate that the synthesis of Nd(OH)3 achieve clusters of nanoparticles (Figure 1a) The bright-field TEM micrograph in Figure 1 illustrates the Nd(OH)3 following the cleaning process, reavealing and average length of 40 ± 5 nm of the clusters. After, figure 1b shows a change in the morphology of the Nd(OH)3 after 10 seconds of exposure under the Electron Beam. This atomic reordering may occur through two stages: the loss of crystallinity followed by recrystallization. This idea is supported by the change in morpholofy after 20 and 30 s (figura 1c and 1d) in which the clusters transformed into a bigger particle, resulting in the final stage that demonstrates the stabilization of the crystal lattice. Additionally, the electron diffraction (ED) pattern of neodymium hydroxide (Nd(OH)3), as showcased in the insets of Figure 2a, reveals a highly organized lattice structure, indicating the well-defined crystallinity of the material. The ED pattern serves as a microscopic fingerprint of the material's crystallographic structure, displaying distinct diffraction spots that correspond to the specific crystallographic planes of Nd(OH)3. This clear depiction underscores the material's inherent structural order and symmetry. As the exposure time under the electron beam extends beyond 30 seconds, as illustrated in Figure 2b, there is a noticeable transformation in the material's crystallographic structure. This change is evidenced by alterations in the diffraction spots within the ED pattern, which signify adjustments in the arrangement, orientation, and degree of crystallinity of Nd(OH)3. Such modifications are indicative of a re-arrangement within the crystal structure, potentially due to dislocations in the crystal lattice. These dislocations can act as sites of strain within the crystal, prompting a re-organization of atoms to minimize energy and achieve stability under the continued influence of the electron beam [5]. TEM image of a cluster of Nd(OH)3 nanostructures recorded after (a) 0 s, (b) 10 s, (c) 20s and (d) 30 s of electron beam exposition. HRTEM Image of Nd(OH)3 nanostructures recorded after (a) 0 s, (b) 30 s, (c) 60s and (d) 120 s of electron beam exposition. Note that insert show the computed FFT of the corresponding images.