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Sol–Gel Processing
Published in M. N. Rahaman, Ceramic Processing and Sintering, 2017
The chemistry of silica in aqueous systems (e.g., sodium silicate) is discussed in detail by Iler (10). Silicon is hydrolyzed even in dilute acid and as shown in Fig. 5.4, silicic acid [Si(OH)4], often referred to as monosilicic acid, orthosilicic acid, or soluble silica, is the dominant mononuclear species in solution below pH values of ˜7 (11). The Si-OH group is called a silanol group, indicating that Si(OH)4 contains four silanol groups. Above pH ≈ 7, further hydrolysis produces anionic species:
Incorporation and structural arrangement of microemulsion droplets in cylindrical pores of mesoporous silica
Published in Molecular Physics, 2021
Albert Prause, Anja Hörmann, Viviana Cristiglio, Glen J. Smales, Andreas F. Thünemann, Michael Gradzielski, Gerhard H. Findenegg
The interaction of microemulsions with solid surfaces, or their immobilisation in porous substrates is often relevant for many of their potential applications, for instance for soil decontamination [14] or tertiary oil recovery [15]. For the purpose of having a simple model system ordered mesoporous silica materials are attractive, due to their structural well-defined pore structure that allows for detailed studies. They are nano-structured SiO2 based materials with a structure size in the range of 2–50 nm [16]. Typically, they are synthesised via a bottom up approach, starting from a self-assembled template by condensation of orthosilicic acid, which is produced in situ from a molecular precursor such as tetraethyl orthosilcate (TEOS). From this a highly ordered mesoporous silica (OMS) can be obtained with a high specific surface area and pore volume. Two representative materials are Mobil Composition of Matter-41 (MCM-41) [17] and Santa Barbara Amorphous-15 (SBA-15) [18]. Both materials were largely studied in literature for example as a support material for catalysts [19–21], template material for synthesis of rod-like nanoparticles [22,23], delivery or host system for guest molecules such as drugs or enzymes [24,25], or for fundamental research on fluids/solids under confinement [26–28].
Amphiphilic peptide binding on crystalline vs. amorphous silica from molecular dynamics simulations
Published in Molecular Physics, 2019
Janani Sampath, Jim Pfaendtner
Biomineralization in diatoms has been widely studied, and it is documented that the silaffin protein consisting of seven analogs R1–R7 catalyses orthosilicic acid to precipitate nano silica [5–7]. The 19-residue domain of silaffin, R5, has been shown to precipitate silica in vitro similar to the parent protein, in neutral pH. Unlike silaffin, R5 does not require any post-translational modifications in the form of phosphorylation or aminenation to precipitate silica, however, it does require the presence of a phosphate buffer [8,9]. The relative ease of R5 synthesis prompted many studies to understand the process of biomineralization using R5 as a template [10–12]. Additionally, other small peptide motifs containing long chain polyamines, and poly-L-lysine groups have also been used to perform in vitro studies to provide insight into the driving forces behind peptide mediated biomineralization [13–15].
Comprehensive utilisation of blast furnace slag
Published in Canadian Metallurgical Quarterly, 2023
Jinyu Zou, Zihan Liu, Qiang Guo
Available silicon plays an important role in rice growth and development, photosynthesis, transpiration, disease prevention, and metal ion toxicity [23]. The main components of silica fertiliser are calcium silicate (CaSiO3) and dicalcium silicate (Ca2SiO4), and its silicate structure is easier to convert into effective silicon. The main mineral phase of granulating slag presents the structure of dicalcium silicate by quenching remote cooling, when external force or external chemical reaction is involved, it is easy to make [SiO4]4+ free, and OH- to form orthosilicic acid (available silicon), which can be used as silicon fertiliser after activation of blast furnace water quenching slag.