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16 Paraffins and Cycloparaffins over a Mesoporous Zeolite — Unstacked H-MCM-22
Published in Chunshan Song, Chang S. Hsu, Isao Mochida, Chemistry of Diesel Fuels, 2020
Isao Mochida, Teruyuki Nagayoshi, Seiichiro Eguchi, Kinya Sakanishi, D. Duayne Whitehurst
Commercial grade reagents of NaAlO2 (Na/Al=0.75), NaOH (96%, K=0.2), and hexamethyleneimine (HMI, 98%) were obtained from Wako Chemical. The silica source supplied by Nissan Kagaku. was colloidal silica (40–41% aqueous SiO2), in which the colloid size and pH values were 10–20 μm and 9–10.5, respectively.
Biomaterials and Bioprocesses of Construction Biotechnology
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
If carbohydrates are added to soil, fermenting anaerobic bacteria can diminish the pH due to the formation of organic acids during the fermentation of carbohydrates. This could be potentially used in bioclogging and biocementation to precipitate silicates from colloidal silica suspension. It is known that the stability of colloidal silica suspension is reduced at acidic pH levels. Thus, inorganic acids are added in this type of chemical grouting.
Silica Nanoparticles for Diagnosis, Imaging and Theranostics
Published in Vladimir Torchilin, Handbook of Materials for Nanomedicine, 2020
Jessica Rosenholm, Tuomas Näreoja
Silicon (Si) is the second most abundant element in the earth’s crust preceded only by oxygen, making Si the most abundant metallic element. Their combination (SiO2), i.e., silica, makes up about 60% of the crust in the form of, e.g., quartzite and sandstone [1]. These are crystalline forms of silica, whereas the amorphous form is well known to, e.g., the pharmaceutical, cosmetic and food industries since decades, usually in the form of colloidal (or fumed) silica. As a pharmaceutical excipient, colloidal silica is used as an adsorbent, anticaking agent, emulsion stabilizing agent, glidant, suspending agent, tablet and capsule disintegrant, and viscosity-increasing agent [2]. Silica is also the main constituent of bioglass, where its relative amount dictates the bioactive properties [3]. In the SiO2–CaO-Na2O-P2O5 system that constitutes bioglass, bonding to both bone and soft tissue is possible at 52 wt% SiO2, whereas 52–60% SiO2 bonds only to bone.
Plastic shrinkage cracking properties of high-performance shotcrete with supplementary cementitious materials
Published in European Journal of Environmental and Civil Engineering, 2023
Kyong-Ku Yun, Valerii Panov, Seungwon Kim, Seungyeon Han
Colloidal silica has been proposed as an admixture for reducing the occurrence of initial shrinkage cracks. Colloidal silica provides silica particles in a well-dispersed state, without significant agglomeration compared to silica fume or nanosilica powder. These discrete particles have hydroxylated surfaces and achieve stability by possessing a net negative charge on the surface, strong enough to repulse the van der Waals attractive forces (Hendrix et al., 2019). The physical and chemical properties of colloidal silica with a particle size of 10 nm are summarized in Table 1. To assess the effect of CS on the crack resistance of shotcrete, the addition of fly ash and silica fume in combination with CS at different ratios. Fly ash is the most widely used supplementary cementitious material in concrete. The chemical and physical properties of the ultra-fine fly ash (UFFA) used in this study, a finely dispersed fly ash produced by grinding, are shown in Table 1. SF is often used as an admixture in concrete to improve its physical structure, but the high water absorbency of this material can impair the ability of concrete to resist cracking. The properties of the SF used in this study are shown in Table 1. An effective air-entraining (AE) water-reducing (WR) agent containing 0.2% AE agent was used as an admixture to achieve the required slump and air volume in the shotcrete. The amount of AE WR used was in the range of 0.5–2.5% by weight of the binder.
Drained shear strength parameters of silty sand grouted by colloidal silica
Published in International Journal of Geotechnical Engineering, 2020
Iman Nouri Delavar, Reza Noorzad
Colloidal silica is a series of microscopic solid particles dispersed in water and produced through a saturated solution of silicic acid. The particle size is generally between 7 and 22 nm. Chemically and biologically, this solution is non-toxic and neutral, and its specifications are stable (Gallagher, Pamuk, and Abdoun 2007). This material turned into a gel by reducing the repulsive force between particles in a controlled situation. According to Gallagher and Lin (2009), colloidal silica particles primarily turn into a chain structure during gelation. Thereafter, it is converted into uniform three-dimensional networks and finally into solid grains. As mentioned by Diaz-Rodriguez et al. (2008), cementation increases resistance. Colloidal silica grout may have an effect on soil strength, which is similar to cementation, by creating artificial bonds among sand grains. In this paper, the effects of colloidal silica were studied on the mechanical behavior of silty sand using different amounts of silt.
Nanosilica composite asphalt mixtures performance-based design and optimisation using response surface methodology
Published in International Journal of Pavement Engineering, 2020
Nura Bala, Madzlan Napiah, Ibrahim Kamaruddin
Silica is one of the abundant compounds deposited worldwide which is largely used by industries to produce colloidal silica, silica gels and fumed silica. Nanosilica is used by industries producing medicines, in cement and concrete mixtures and in industries to reinforce elastomers as rheological solutes (Yusoff et al.2014). The specifications of nanosilica used in this research are presented in Table 3.