The Utility of Nanocomposites in Fire Retardancy

Nanocomposites have been shown to significantly reduce the peak heat release rate, as measured by cone calorimetry, for many polymers but they typically have no effect on the oxygen index or the UL-94 classification. In this review, we will cover what is known about the processes by which nanocomposite formation may bring this about. Montmorillonite will be the focus in this paper but attention will also be devoted to other materials, including carbon nanotubes and layered double hydroxides. A second section will be devoted to combinations of nanocomposite formation with conventional (and unconventional) fire retardants. The paper will conclude with a section attempting to forecast the future

Inherent Ethyl Acetate Selectivity in a Trianglimine Molecular Solid

Ethyl acetate is an important chemical raw material and solvent. It is also a key volatile organic compound in the brewing industry and a marker for lung cancer. Materials that are highly selective toward ethyl acetate are needed for its separation and detection. Here, we report a trianglimine macrocycle (TAMC) that selectively adsorbs ethyl acetate by forming a solvate. Crystal structure prediction showed this to be the lowest energy solvate structure available. This solvate leaves a metastable, “templated” cavity after solvent removal. Adsorption and breakthrough experiments confirmed that TAMC has adequate adsorption kinetics to separate ethyl acetate from azeotropic mixtures with ethanol, which is a challenging and energy-intensive industrial separation

Reconstructed covalent organic frameworks

Covalent organic frameworks (COFs) are distinguished from other organic polymers by their crystallinity1–3, but it remains challenging to obtain robust, highly crystalline COFs because the framework-forming reactions are poorly reversible4,5. More reversible chemistry can improve crystallinity6–9, but this typically yields COFs with poor physicochemical stability and limited application scope5. Here we report a general and scalable protocol to prepare robust, highly crystalline imine COFs, based on an unexpected framework reconstruction. In contrast to standard approaches in which monomers are initially randomly aligned, our method involves the pre-organization of monomers using a reversible and removable covalent tether, followed by confined polymerization. This reconstruction route produces reconstructed COFs with greatly enhanced crystallinity and much higher porosity by means of a simple vacuum-free synthetic procedure. The increased crystallinity in the reconstructed COFs improves charge carrier transport, leading to sacrificial photocatalytic hydrogen evolution rates of up to 27.98 mmol h−1 g−1. This nanoconfinement-assisted reconstruction strategy is a step towards programming function in organic materials through atomistic structural control

Tool wear investigation in high-pressure jet coolant assisted machining Ti2AlNb intermetallic alloys based on FEM

The excellent mechanical properties of Ti2AlNb intermetallic compounds are beneficial to improve the performance of aero-engine. However, because of their high strength ratio especially at high temperature along with the low thermal conductivity of Ti2AlNb, the machinability of this material is poor. In this paper, high-pressure jet cooling technology is applied for the machining of Ti2AlNb intermetallic alloys to investigate the effects of high pressure jet cooling on the machinability of Ti2AlNb. The performance associated with the cutting force, the cutting temperature, the chip morphology and the tool wear have been discussed. The results showed that the high pressure jet cooling can enhance the heat dissipation by weakening the phenomenon of bubble adsorption in the cutting area based on the FEM simulations. The high pressure jet cooling can break the chip into C-type chip and improve the chip breakage capability. It also demonstrates that the crater wear and adhesive wear near the cutting edge can be significantly reduced with the high pressure jet cooling technology. When the jet pressure reaches 10 MPa, the cutting temperature reduced 22% and the tool life improved by 89%. Keywords: Intermetallic alloys, High pressure jet coolant, Tool wear, FEM, Chip breakage, Tool lif

Investigation on the delaminated-pillared structure of TiO2-PILC synthesized by TiCl4 hydrolysis method

TiO2-PILCs were synthesized by the reaction between montmorillonite and acidic solutions of hydrolyzed TiCl4. Unlike commonly reported microporous pillared structure, a meso-microporous delaminated structure containing pillared fragments was observed in the resulting TiO2-PILC, based on the combined analyses of powder X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, chemical analysis, thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. Air-drying after ethanol extraction (EAD) is shown to be more effective than air-drying (AD) in preserving the delaminated structure in the resultant Ti-clay. A broad XRD peak at low 2? angle with a high d-spacing of ca. 6.6 nm was firstly reported and it was proposed to be correlated with the mesoporous delaminated structure rather than the (001) reflection of intercalated/pillared periodic structure. The resulting TiO2-PILC exhibits a good thermal stability as indicated by its surface area after calcination at 600 degrees Celsius. Moreover, calcination above 300 degrees Celsius results in the formation of nanocrystalline anatase in the TiO2-PILC, and the grain size of anatase increases with the increment of calcination temperature. However, no phase transformation from anatase to rutile was observed even under calcination at 1000 degrees Celsius. These fundamental results provide new insights about the structure of TiO2-PILC synthesized by TiCl4 hydrolysis method

Effect of waste ceramic adsorbent on wastewater treatment

The preparation of porous ceramic with waste porcelain powder as aggregate research. The influence of the amount of Sesbania powder and the calcination temperature on the adsorption performance of porous ceramics was investigated. The effect of the amount of porous ceramic and the adsorption time on the removal rate of Cu in wastewater containing Cu was investigated.The results showed that the adsorption properties of porous ceramics were related to the calcination temperature and the amount of Sesbania powder. The suitable calcination temperature and the amount of Sesbania powder were 600 °Cand 4 wt%, respectively.The removal rate of Cu in water samples increases with the increase of the amount of porous ceramics and the increase of adsorption time. The suitable amount of porous ceramics is 10 g/L and the adsorption time is 35 min. XRD characterization showed that the crystal particles were grown by calcination, and the properties of porous ceramics were stable before and after adsorption