formaldehyde, phenol formaldehyde, silicone, vinyl ester, cyanate ester, unsaturated polyester resin, etc. The properties of thermoset materials can be further improved by reinforcing them with fi llers, most commonly used being clays, carbon nanotubes, and graphene nanoplatelets. GrapheneGraphene is a fundamental building block of all graphitic forms of carbon and consists of a single layer of sp 2 -hybridized carbon atoms arranged in a honeycomb structure. A single defect-free graphene layer has Young's modulus of 1.0 TPa, intrinsic strength 42 N m −1 , thermal conductivity 4840-5300 W (m K) −1 , electron mobility exceeding 25 000 cm 2 V −1 s −1 , excellent gas impermeability and specifi c surface area of 2630 m 2 g −1 . [3][4][5][6][7][8][9][10][11] On incorporation into polymers, the mechanical, thermal, as well as electrical properties of the polymeric materials are significantly improved. [ 3,[12][13][14][15] The geometry differs with size and number of atomic layers, which determines the aspect ratio and the specifi c surface area. Generally speaking, GNSs have higher specifi c surface area than CNTs, thus, having higher potential of property enhancement in Graphene has resulted in signifi cant research effort to generate polymer nanocomposites with improved mechanical, thermal as electrical properties as compared to pure polymers. A large number of studies have been undertaken using different graphene derivatives, fi ller loadings, synthesis methods, and so on to obtain optimum fi ller dispersion as well as fi ller-matrix interactions, which are crucial for achieving signifi cant enhancement in the properties, especially at low fi ller fraction. This review summarizes the mechanical and thermal properties of numerous studies carried out for the property enhancements of commercially relevant thermosetting materials such as epoxy, polyurethane, natural rubber, melamine formaldehyde, phenol formaldehyde, silicones, vinyl ester, cyanate ester, and unsaturated polyester resin.
It was proposed that incorporation of nitrogen groups on mesoporous silica pores would enhance its surface polarity and improve adsorption of gaseous BTX (benzene, toluene, and m-xylene). Among the popular list of mesoporous silica adsorbents, KIT-6 and SBA-15 were selected as a result of their superior textural properties, as well as because they are being widely reported in literature. After preliminary screening using toluene test, KIT-6 was chosen to have better affinity and therefore selected for Aptes (3-aminopropyl triethoxysilane) surface modification. Aptes modification was performed through the grafting method utilizing factorial design of experimental techniques to identify the effective process variable covering the parameters: Aptes concentration, reaction temperature, and reaction duration. The results of a statistical design of experiments using Minitab-15 showed that Aptes concentration was the only significant factor which affects the silica adsorbent BET surface area. Benzene adsorption was found to be highest on KIT-6 adsorbent, while m-xylene and toluene had their highest values on 0.006% Aptes adsorbent (KIT-6 modified with 0.006% v/v Aptes) relative to other adsorbents. m-Xylene had the highest adsorption relative to toluene and benzene on all modified silica adsorbents (0.006% Aptes, 0.33% Aptes, and 0.66% Aptes) except for 8% Aptes adsorbent. 0.006% Aptes adsorbent was selected as the best adsorbent for BTX adsorption.
The conventional process of lithium extraction from α-spodumene (LiAlSi 2 O 6 ) is energy-intensive and associated with high byproduct management cost. Here, we investigate an alternative process route that uses potassium sulfate (K 2 SO 4 ) to extract lithium while producing leucite (KAlSi 2 O 6 ), a slow release fertilizer. Presenting the first-ever in situ record of the reaction of α-spodumene with potassium sulfate, we use synchrotron X-ray diffraction (XRD) and differential scanning calorimetry (DSC) to document the reaction sequence during prograde heating. From 780 °C, we observe a broad endothermic DSC peak, abnormal expansion of the α-spodumene structure, and an increase in α-(Li, K)-spodumene peak intensity during heating with potassium sulfate, indicative of the exchange between lithium and potassium in the spodumene structure. When 11 ± 1% K occupancy in the M2 site of α-(Li, K)-spodumene is reached, the mechanism changes from ion exchange to a reconstructive transformation of α-(Li, K)-spodumene into leucite, evidenced by a decrease in α-spodumene and potassium sulfate abundance concurring with formation of leucite over a narrow temperature range between 850 and 890 °C. The increasing background intensity in synchrotron XRD above 870 °C suggests that a lithium sulfate-bearing melt starts to form once >90% of α-spodumene has been converted during the reaction. This fundamental understanding of the reaction between α-spodumene and potassium sulfate will enable future development of lithium extraction routes using additives to significantly decrease energy intensity and to produce marketable byproducts from α-spodumene.
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