Facile synthesis and thermal properties of waterglass-based silica xerogel nanocomposites containing reduced graphene oxide

Oikawa, K; Toyota, Kei; Sakatani, Shigeaki; Hayashi, Yamato; Takizawa, Hirotsugu

doi:10.1016/j.ceramint.2018.11.089

Cited by 11 publications

(4 citation statements)

References 28 publications

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“…It is considered that, in a diluted carbon concentration of approximately 0.5%, no heat conduction path is formed in the film thickness direction, because the carbon material is scattered in the silica xerogel, and, hence, the thermal conductivity is low. Table 3 also shows thermal conductivity data from previous studies on a 0.4% graphite-doped silica aerogel composite (SA-G-0.4) [12] and a glass fiber reinforced 0.5% reduced graphene oxide (rGO)-doped silica xerogel composite (GFR-SX-rGO-0.5) [22] for comparison with the present data. As with the present data, very low thermal conductivity of less than 0.02 W/(m • K) is realized in these composites.…”

Section: Combustion Behavior and Thermal Conductivitymentioning

confidence: 94%

“…Therefore, we examined the effect of adding various carbon materials to silica xerogel. As already reported in reduced graphene oxide (rGO) [22], we hypothesized that thermal decomposition of organic functional groups of silica xerogel can be delayed by utilizing the sublimation heat of a sublimating carbon material at high temperature. Simultaneously, as the carbon material undergoes a combustion reaction with O 2 molecules in a hightemperature atmosphere and produces CO 2 , it is considered to function as a flame retardant by diluting combustible gases.…”

Section: Introductionmentioning

confidence: 91%

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Enhancement of transient thermal stability and flame retardancy of hydrophobic silica xerogel composites via carbon family material doping

Oikawa

Toyota

Okazaki

et al. 2019

Journal of Asian Ceramic Societies

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In this study, we investigated the influence of the addition of carbon materials on the heat resistance and flame retardancy of silica xerogels. A mixed dispersion prepared by adding 0.1 to 2.5 wt% each of the carbon materials, graphene oxide (GO), poly (3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS), and carbon black (CB) to waterglass (SiO 2 6%) was used as the raw material. By adding acid to this dispersion, a sol-gel reaction was carried out and the hydrogel obtained was hydrophobized with hydrochloric acid and a mixed solution of siloxane/isopropylalcohol . Finally, novel carbon-silica xerogel composites (SX-Carbon-X) were prepared via ambient pressure drying. Similarly, glass-fiber-reinforced silica xerogel composite sheets (GFR-SX-Carbon-X) were prepared by impregnating glass fibers with sol. The bulk densities of the samples obtained ranged from 0.204 to 0.217 g/cm 3 , their thermal conductivities ranged from 0.0187 to 0.0203 W/(m • K). As the amount of carbon material added was increased, the thermal decomposition temperature of the SX-Carbon-X shifted to higher temperatures. In the cone calorimeter test of GFR-SX-Carbon-X, moreover, adding at least 0.5% of the carbon material significantly reduced the combustion time and the peak heat release rate (PHRR), and the flame retardancy improved remarkably.

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Section: Combustion Behavior and Thermal Conductivitymentioning

confidence: 94%

Section: Introductionmentioning

confidence: 91%

Enhancement of transient thermal stability and flame retardancy of hydrophobic silica xerogel composites via carbon family material doping

Oikawa

Toyota

Okazaki

et al. 2019

Journal of Asian Ceramic Societies

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“…After NaOH-impregnation of carbon allotropes, the shrunk and lower HRR curves are clearly examined for S7 and S8 compared with those of S3 and S4, as shown in Figure 2b, due to the impurities eliminated by NaOH, leading to a remarkable increase in FGI, which rose from 0.08 to 0.12 kW·m −2 ·s −1 for S3 (Table 1). However, the S6 exhibits a retarded T p with a decreased FGI compared with that of S2, due to the stable and inert structure of FG under the strong alkali-condition; it could have served as a heat dissipation filler, due to its high thermal conductivity [16].…”

Section: Hrr Of Ti Blended With Different Carbon Allotropesmentioning

confidence: 99%

Real-Time Measurement on the Heat Release Property of Titanium Blended with Different Carbon Allotropes, under Externally Constant Heat Flux

Wang

Zhao

2019

Metals

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Ti/C blended powder is commonly employed as an initiating combustion agent for preparing calcium aluminate; a dedicated test system is exploited for real-time examining of the heat release of Ti/C blended powder during combustion under atmosphere conditions with an externally constant heat flux of 973 K, which is comprised of cone calorimeter, thermal-gravimetry/differential scanning calorimetry, X-ray diffraction (XRD), scanning electron microscope/energy dispersive spectrometer, and a theoretical thermal calculation, with the aim of quantitatively illuminating its combustion mechanism in depth. Furthermore, a comparison of the heat release property of titanium powder blended with different carbon allotropes, including natural flaky graphite (FG), carbon black (CB), expandable graphite (EG), and vermicular graphite (VG) is preliminarily investigated, to clarify the effect of different carbon allotropes on the heat release property of Ti/C blended powder. It reveals that the oxidation reaction between Ti and O 2 initiates the subsequent combination of TiC through a thermal explosion reaction, using graphite (FG, VG, or EG) and Ti powder as the starting materials, respectively. Moreover, EG facilitates an accelerated (fire growth index of 0.42 kW·m −2 ·s −1 ) and enhanced peak heat release rate (pHRR) of 30.7 kW·m −2 at 73 s, while VG suppresses the heat release with the pHRR of 5.2 kW·m −2 at 64 s and fire growth index of 0.08 kW·m −2 ·s −1 , and FG favors the formation of TiC with a higher crystallinity from XRD. Additively, the prior NaOH-impregnation is favorable for the formation of TiC for Ti/CB blended powder, although the TiO 2 predominates final combustion production. It reveals the chemical evolution and mechanisms evolved in the formation of TiC during ignition.Metals 2019, 9, 981 2 of 16 contains expandable graphite (EG), vermicular graphite (VG), or expanded graphite after instantaneous expansion of EG, and natural flaky graphite (FG), which hold obviously different micro-structures and properties. Therefore, the various carbon sources affect the productions formed by SHS reaction [11]. It has been reported that the carbon nanotube and graphene as carbon sources impart enhanced tribological properties [12]; CB favors the formation of nano-metric TiC-carbon composite with a smaller particle size, as the most effective carbon allotrope for hindering the sintering of TiC under high temperature [13]. However, there is an interesting phenomenon-that the explosive reaction between graphite and titanium powder occurs under atmospheric pressure at 973 K with a transiently glaring flame, which inspired us to excavate its reaction mechanism, in order to explain the curious phenomenon.Consequently, the real-time measurement of heat release property involved in titanium blended with different carbon allotropes is preliminarily investigated, which is detected and recorded by cone calorimeter (CC) and thermal-gravimetry/differential scanning calorimetry (TG/DSC), respectively, using FG, CB, EG, and VG as different ...

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“…Public concern about fire triggers research activity that has already created effective fire-protective additives for polymers, [ 15 , 16 , 17 , 18 , 19 , 20 ] like hydrated compounds, for example, hydrated salts [ 21 ], oxides (e.g., alumina) and clays that undergo endothermic degradation, carbonates like huntite that decompose forming a CO 2 gas blanket, halogenated paraffins and polymers that emit free-radical suppressants, and chemicals that intumesce like the expandable ammonium phosphates [ 22 ], or still those that form a barrier between air and the substrate, e.g., silica [ 23 , 24 , 25 , 26 ] and clays [ 27 , 28 ], or char as, for example, organophosphorus compounds [ 16 , 29 , 30 , 31 ], polyols and melamine. Graphite (flakes, powder or expanded) has been used as an additive in intumescing coatings [ 19 , 20 , 32 , 33 , 34 , 35 ] and in polymer composites [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. Thus, existing fire-retardants explore different approaches and mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Environmentally Friendly, High-Performance Fire Retardant Made from Cellulose and Graphite

et al. 2021

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Many materials and additives perform well as fire retardants and suppressants, but there is an ever-growing list of unfulfilled demands requiring new developments. This work explores the outstanding dispersant and adhesive performances of cellulose to create a new effective fire-retardant: exfoliated and reassembled graphite (ERG). This is a new 2D polyfunctional material formed by drying aqueous dispersions of graphite and cellulose on wood, canvas, and other lignocellulosic materials, thus producing adherent layers that reduce the damage caused by a flame to the substrates. Visual observation, thermal images and surface temperature measurements reveal fast heat transfer away from the flamed spots, suppressing flare formation. Pinewood coated with ERG underwent standard flame resistance tests in an accredited laboratory, reaching the highest possible class for combustible substrates. The fire-retardant performance of ERG derives from its thermal stability in air and from its ability to transfer heat to the environment, by conduction and radiation. This new material may thus lead a new class of flame-retardant coatings based on a hitherto unexplored mechanism for fire retardation and showing several technical advantages: the precursor dispersions are water-based, the raw materials used are commodities, and the production process can be performed on commonly used equipment with minimal waste.

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Facile synthesis and thermal properties of waterglass-based silica xerogel nanocomposites containing reduced graphene oxide

Cited by 11 publications

References 28 publications

Enhancement of transient thermal stability and flame retardancy of hydrophobic silica xerogel composites via carbon family material doping

Enhancement of transient thermal stability and flame retardancy of hydrophobic silica xerogel composites via carbon family material doping

Real-Time Measurement on the Heat Release Property of Titanium Blended with Different Carbon Allotropes, under Externally Constant Heat Flux

Environmentally Friendly, High-Performance Fire Retardant Made from Cellulose and Graphite

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