This paper investigated the fire-retardant mechanism of the nano-LDHs in the intumescent system by the temperature programmed oxidation (TPO). Researches were also conducted to explore the function of the nano-LDHs in the composite fire-retardant agents in air and nitrogen atmosphere, respectively. The results indicated that the nano-LDHs species were responsible for the catalytic oxidation of the rich-carbon compound in oxygen atmosphere. In addition, the nano-LDHs species and their calcinated products at high temperature could increase the carbonaceous residue-shield of the carbon-rich materials, improve the quality and the graphitization degree of the formed char-layer, and accelerate the intumescence and expansion of the melting carbon-rich materials to a certain degree under the oxygen-free condition, leading to the carbonization and expansion of the intumescent layer.nanometer, layer double hydroxides (LDHs), fire-retardant mechanism, intumescent system Since the layered double hydroxides (LDHs) were firstly published to be used as precursors of new catalysts by Miyata S [1] in 1971, many issues on their potential applications were increased year after year. The interstitial layers of LDHs were analogous to the molecular sieve, leading to their direct application to a rigidity support framework for the intumescent coat of the fire-retardant coating with an increasing fire-retardant performance. Moreover, the complex metal oxides, formed by calcination of LDHs at different temperature, exhibited an improvement on the carbonization of intumescent layer of fire-retardant coating in fire. Therefore, the LDHs gradually became an ideal fire-retardant auxiliary agent. It should be noticed that the nanometer layered double hydroxides (nano-LDHs) had received considerable interests owing to their comprehensive applications as fire-retardants in recent years. The thermal stability and thermal degradation process of nano-LDHs were analyzed by Yang W et al. [2][3][4] , and their fire-retardant performance were also investigated by Xu Jianghua et al. [5][6][7] ; however, there were few studies on their fireretardant mechanism. The present work mainly purposed to firstly study the fire-retardant mechanism of nanoLDHs by the temperature programmed oxidation, and investigate their fire-retardant function in the intumescent fire-retardant system. Experimental Reagent and instrumentsThe preparation of the purposed products was carried out on the QM planet-style ball mill (Instrument Factory of Nanjing University). The self-manufactured temperature programmed oxidation (TPO) equipment, whose temperature control was carried out on an AI-708PA artificial intelligence industry adjuster (ÜGU Company), was recorded on the produced gas quantity (Figure 1).
The tempered glass is widely used in the buildings because of its good transparence and fire endurance under the protection of the sprinkler.The fire backdraft may occur under the good ventilation condition after the tempered glasses fall apart in fire, which can endanger the human evacuation and fire rescue. By the testing of the surface temperature of the tempered glass exposed to the building fire, the critical temperature of the glass fracture can be acquired and the basis for the prediction and prevention of the fracture of the tempered glass then can be provided, which is useful for the performance-based design of the fire safety. The infrared imaging equipment is firstly used in China for the research on the fire endurance of the tempered glass.
The coating process of a nano-scale SiO 2 film on the nanocrystalline Mg-Al layered double hydroxides via a sol-gel process was investigated. The uniform and dense SiO 2 film with a thickness of about 5 nm on the nano-LDHs particles was characterized by the solubility test in the dilute HNO 3 or HCl acid, TEM and FT-IR, XRD, TG and DSC. The chemical shifts of binding energies of Al 2p, Mg 2p, Si 2s and O 1s on the coated particles indicate that the coating of the SiO 2 nano-film on the surface of the nano-LDHs proceeds through the formation of Mg-O-Si and Al-O-Si bonds. The thermal analysis shows that both the SiO 2 -coated nano-LDHs and the nano-LDHs have a similar mass loss process, in which there are three obvious stages of mass loss in the temperature range of 40-700℃. Furthermore, the more the coated amount of SiO 2 on the surface of the nano-LDHs is, the less the mass loss of the samples is at 700℃.The nano-LDHs have two obvious endothermic peaks at 244.67℃ and 430.13℃, whose corresponding heat absorption capacities are 412.28 J/g and 336.30 J/g, respectively. In contrast, the coated nano-LDHs have only one endothermic peak at 243.60℃ with a heat absorption capacity of 221.25 J/g.
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