Morphologies of nanomaterials

The alternation of temperature in a hydrothermal reaction was demonstrated to be crucial in changing the crystal phases or morphologies of nanomaterials. In the case of K2Cr207, when the reaction temperature was increased to 180 °C, K-OMS-2 microspheres consisting of nanoneedles were synthesized in contrast to the nanoduster arrays composed of tetragonal prism nanorods synthesized at 120 °C (Figure 8.1a-c). In the case of Na2Cr207, when the reaction temperature was 100 °C, Na-OMS-2 phase was formed. However, when the reaction temperature was... 

Tailoring block copolymers with three or more distinct type of blocks creates more exciting possibilities of exquisite self-assembly. The possible combination of block sequence, composition, and block molecular weight provides an enormous space for the creation of new morphologies. In multiblock copolymer with selective solvents, the dramatic expansion of parameter space poses both experimental and theoretical challenges. However, there has been very limited systematic research on the phase behavior of triblock copolymers and triblock copolymer-containing selective solvents. In the future an important aspect in the fabrication of nanomaterials by bottom-up approach would be to understand, control, and manipulate the self-assembly of phase-segregated system and to know how the selective solvent present affects the phase behavior and structure offered by amphiphilic block copolymers. 

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

Hydrothermal synthesis is a powerful method used for the fabrication of nanophase materials due to the relatively low temperature during synthesis, facile separation of nanopartides in the product, and ready availability of apparatus for such syntheses. Versatile physical and chemical properties of nanomaterials can be obtained with the use of this method that involves various techniques (e.g., control of reaction time, temperature and choice of oxidant and its concentration). Several extensive reviews are available that discuss the fundamental properties and applications of this method [2, 3]. These reviews cover the synthesis of nanomaterials with different pore textures, different types of composition [2, 4—6], and different dimensionalities in terms of morphology [6-8]. 

Well-defined Quantum Dots and Morphological Control of Nanomaterials... 

It was also found that the presence of some metal ions and borates can effectively accelerate the hydrothermal carbonization of starch, which shortens the reaction time to some hours. Thus, iron ions and iron oxide nanoparticles were shown to effectively catalyze the hydrothermal carbonization of starch (< 200 °C) and also had a significant influence on the morphology of the formed carbon nanomaterials [10]. In the presence of Fe2+ ions, both hollow and massive carbon microspheres could be obtained. In contrast, the presence of Fe203 nanoparticles leads to very fine, rope-like carbon nanostructures, reminding one of disordered carbon nanotubes. 

Amorphous silicas play an important role in many different fields, since siliceous materials are used as adsorbents, catalysts, nanomaterial supports, chromatographic stationary phases, in ultrafiltration membrane synthesis, and other large-surface, and porosity-related applications [16,150-156], The common factor linking the different forms of silica are the tetrahedral silicon-oxygen blocks if the tetrahedra are randomly packed, with a nonperiodic structure, various forms of amorphous silica result [16]. This random association of tetrahedra shapes the complexity of the nanoscale and mesoscale morphologies of amorphous silica pore systems. Any porous medium can be described as a three-dimensional arrangement of matter and empty space where matter and empty space are divided by an interface, which in the case of amorphous silica have a virtually unlimited complexity [158],... 

Furthermore, the values of the activation energies depend on the analysis method used. In addition, concentration of defects, homogeneity, and morphology of the sample, presence of catalyst particles, and other synthesis-related factors must be taken into consideration during the analysis of the measured data and interpretation of the results. Therefore, literature data on activation energies of carbon nanomaterials vary widely. 

One of the most important issues of nanomaterial growth is the control of the morphology. This can be done by varying different process parameters. The effect of the growth temperature on the structure of the Si nanowires has been studied systematically [32, 33]. 

In case the properties of nanomaterials of various structure, shape, surface, morphology, etc., differ significantly from each other and, a registration of the nanomaterial as a distinct substance would be justified. [19]... 

Recently, an alternative strategy has been adopted to synthesize metal or semiconductor nanomaterials by exposing precursor metal-organic frameworks (MOFs) to an electron beam. Jacobs et al. (2011) demonstrated the formation for ZnO particles with narrow and tunable size distributions using different Zn-based MOFs. They showed that the composition, size, and morphology of the nanoparticles are determined by the chemistry and structure of the MOF, as well as the electron beam properties. 

Different drying methods were selected by different researchers to produce various nanoparticles or nanostructure materials. Different drying methods have strong effects on the properties of nanomaterials, including particle size, particle morphology, porous structure, specific surface area, etc. Here we compare the results obtained by some researchers who employed different drying methods to prepare nanomaterials. 

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