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Survey of Nanomaterials Synthesis, Fabrication, and Growth
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2019
Xuefeng Song, Kai Tao, Shuai Wang, Xiaofeng Zhao, Jijin Xu
Compared with all other synthetic methods, the hydrothermal method based on a water system has its unique advantages such as simple, easy control, homogeneous resultant, low energy cost, and lower pollution. Hydrothermal synthesis can be considered as a method of synthesis material by solubility changes or chemical reactions of the reactant under a high temperature and pressure atmosphere. By precisely controlling the reaction condition of the liquid or the environment, such as pH value, pressure, temperature, time, concentration, templates, and additives, the chemical composition, size, structure and morphology of the nanostructures can be modulated. Based on the presence or absence of additives and templates in the reaction conditions, the hydrothermal method can be mostly divided into three categories: template-assisted, organic additive-assisted, organic additive- and template-free.9 We will have a brief discussion based on the categories in the following text.
Hybrid Manganese Spinel Ferrite Nanostructures: Synthesis, Functionalization and Biomedical Applications
Published in Surender Kumar Sharma, Nanohybrids in Environmental & Biomedical Applications, 2019
S. Del Sol Fernández, Oscar F. Odio, E. Ramón-Gallegos, Edilso Reguera
Hydrothermal synthesis is based on the high-pressure reaction of metal precursors in water or water–alcoholic solutions, which is often performed in reactors or autoclaves. Particle size and shape can be effectively tuned by varying metal concentration, solvent composition, temperature and reaction time (Wu et al., 2016, Odio and Reguera, 2017). Besides, the addition of biocompatible polymers as surfactants like polyethylene glycol (PEG), dextran (D) and chitosan (CH) can change the shape of NPs, aid in controlling growth and avoid particle agglomeration and the onset of magnetic interactions (Zahraei et al., 2016). Another paper describes the synthesis of MnFe2O4 using a gelatinous medium at 175°C; the resulting NPs display one of the best reported heating efficiency for manganese ferrite with values comparable to those of commercial magnetic NPs (Cruz et al., 2017).
2 for Energy-Efficient Windows
Published in Yi Long, Yanfeng Gao, Vanadium Dioxide-Based Thermochromic Smart Windows, 2021
The principle of hydrothermal synthesis involves a process of dissolution-supersaturation and subsequent crystallization in which the temperature, pressure, and time are the three most common parameters to be considered. Temperature plays an important role in the kinetics of product formation as well as on the thermodynamic stability of the resultant phase. Pressure is essential for the solubility, the supersaturation range directing the crystallization process, as well as the thermodynamic stability of the resulting phase. Time is also an important parameter because the synthesis of kinetically stable phases is favored in a short-term process while the thermodynamically stable phases are generally formed in long-term experiments within a given temperature-pressure regime [4]. Rational design of a hydrothermal product requires understanding of the nucleation and crystal growth process under isothermal and isobar conditions [5, 6]. The fluid consisting only of water with solid precursor materials at the beginning of the hydrothermal reaction (point I in Fig. 7.2) will become denser with time and even above the solubility limit of the precursor materials (point II, supersaturation). A glassy precursor can be dissolved at a faster rate than a crystalline material with the same composition. The supersaturation zone is wider with a glassy starting material than that with a crystalline one, which is pressure dependent. At a certain level of supersaturation (marked as point III), spontaneous crystallization will finally take place, leading to a decrease in the concentration of the hydrothermal fluid as the experiment continues [4]. The hydrothermal technique has been popularly utilized for the crystallization of nanomaterials, and the growth mechanism follows either Ostwald ripening (OR) or oriented attachment (OA) or both. The OR mechanism describes the growth of large particles at the expense of smaller ones due to the lowering of the surface energy. On the other hand, for the OA mechanism, as the surface energy is low or the solubility of the material is weak, the adjacent primary particles spontaneously self-organize into chains of nanoparticles (NPs) with a common crystallographic orientation, followed by joining of these particles via the fusion process. It is worth noting that the OA mechanism was first found in the synthesis of TiO2 particles by using the hydrothermal process [7].
A review on multifunctional nanotechnological aspects in modern textile
Published in The Journal of The Textile Institute, 2022
Prashant D. Sarvalkar, Shubham D. Barawkar, Omkar S. Karvekar, Pandurang D. Patil, Saurabh R. Prasad, Kiran Kumar Sharma, Neeraj R. Prasad, Rajiv S. Vhatkar
In hydrothermal synthesis, there are numerous ways of producing crystalline material from aqueous solutions at high temperatures and pressures. A stainless-steel autoclave with a Teflon liner can be used to accomplish a simple hydrothermal reaction (illustrated in Figure 4). In general, hydrothermal methods are inert to acidic and basic environments. Hydrothermal setups may also be simply assembled and disassembled. The extreme (supercritical) reaction conditions required for producing single crystals have restricted the significant investigation and commercialization of several materials. Due to a growing variety of materials such as metal oxides, composites, ceramics, and others, commercial and scientific interest in hydrothermal synthesis has returned in recent decades (Yang & Park, 2019).
Preparation and characterization of Sb-doped SnO2 (ATO) nanoparticles with NIR shielding by an oxidation coprecipitation hydrothermal method
Published in Journal of Dispersion Science and Technology, 2020
Meng Li, Zi Cai, Yun Yang, Yuanhao Wang, Hong Zhong, Tao Li
There are a few methods to prepare ATO nanoparticles, including hydrothermal synthesis,[17–19] solvothermal synthesis,[20,21] coprecipitation method,[17] sol-gel synthesis,[22] nanoparticle deposition system,[15] heterogeneous nucleation method,[23] nebulized spray pyrolysis,[24] solid-state reaction[25] and Pechini method[25] etc. Among these methods, hydrothermal synthesis has been widely studied and used because of its simple operation, mild reaction conditions, small particle size and not easy to aggregate. Additionally, Terrier et al.[26] synthesized Sb:SnO2 thin film using C2H5OH as solvent, An et al.[27] synthesized ATO using NH3·H2O as precipitant and Zhang et al.[28] synthesized ATO using H2O2 as oxidant, indicating that these solvents could be efficiently used in the preparation of ATO. However, to our knowledge, the effect of the coexistence of three solvents on the preparation of ATO is not investigated. Thus, in this work, the effect of the simultaneous existence of C2H5OH, NH3·H2O and H2O2 on the preparation of ATO is evaluated.
Geopolymerization enhanced hydrothermal synthesis of analcime from steel slag and CFBC fly ash and heavy metal adsorption on analcime
Published in Environmental Technology, 2020
Ze Liu, Li Li, Ningning Shao, Tao Hu, Le Han, Dongmin Wang
Zeolite is an aluminosilicate-type microporous material with large surface area and exchangeable cations in its structure, consisting of SiO4 and AlO4 tetrahedral structures, which exhibits many excellent features, including high hydrothermal stability, high selectivity, and good ion exchange capacity [9]. In recent years, several types of zeolites from the PFA, such as NaA zeolite, analcime, faujasite (zeolite X, Y), gismondine (zeolite P) and so on [10]. A hydroxyapatite–zeolite composite material and FAU zeolite was successfully synthesized from steel slag by Kuwahara et al. [6, 11]. But there is a little research on the synthesis of zeolite from SS and CFA. Generally, the fabrication methods of zeolite include hydrothermal synthesis, microwave synthesis, gel transformation, and so on [12, 13]. Hydrothermal synthesis is favoured by researchers for its simple process and low costs. The traditional single-step hydrothermal method also has some disadvantages, such as long reaction time, high energy consumption, and low conversion rate, which seriously affect the crystallinity of zeolite products [14]. Some previous studies [15-18] tried to enhance the hydrothermal synthesis via geopolymerization process. Geopolymerization is a process with non-crystalline and crystalline phase transition. In general, geopolymerization products are prepared from natural minerals or solid wastes through the polymerization of silicon–oxygen tetrahedra and aluminium–oxygen tetrahedra [15, 19]. The intermediate product is amorphous nano hydrated sodium aluminosilicate (N-A-S-H) gels after geopolymerization process. Geopolymerization would provide high activity precursors for the hydrothermal synthesis of zeolites and shorten the hydrothermal synthesis time [18].