Comparative investigations of ternary thermite Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3) from pyrolytic,kinetics and combustion behaviors

To develop new energy enhancement energetic materials with great combustion performance and thermal stability,two kinds of ternary thermite,Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3),were prepared and analyzed via mechanical ball milling.The samples were characterized by SEM,XRD,TG-DSC,constant volume and constant pressure combustion experiments.The first exothermic peaks of Al/Fe_(2)O_(3)/CuO and Al/Fe_(2)O_(3)/Bi_(2)O_(3) appear at 579°C and 564.5°C,respectively.The corresponding activation energies are similar.The corresponding mechanism functions are set as G(a) = [-ln(1-a)]^(3/4) and G(a) =[-ln(1-a)]2/3,respectively,which belong to the Avrami-Erofeev equation.Al/Fe_(2)O_(3)/CuO has better thermal safety.For small dose samples,its critical temperature of thermal explosion is 121.05°C higher than that of Al/Fe_(2)O_(3)/Bi_(2)O_(3).During combustion,the flame of Al/Fe_(2)O_(3)/CuO is spherical,and the main products are FeAl_(2)O_(4) and Cu.The flame of Al/Fe_(2)O_(3)/Bi_(2)O_(3)is jet-like,and the main products are Al_(2)O_(3),Bi and Fe.Al/Fe_(2)O_(3)/Bi_(2)O_(3)has better ignition and gas production performance.Its average ignition energy is 4.2 J lower than that of Al/Fe_(2)O_(3)/CuO.Its average step-up rate is 28.29 MPa/s,which is much higher than 6.84 MPa/s of Al/Fe_(2)O_(3)/CuO.This paper provides a reference for studying the thermal safety and combustion performance of ternary thermite.

Poly[2]catenane Gels Based on Sequential Assembly of Small Molecules

Comprehensive Summary Polycatenane gels have attracted extensive attention due to their high degree of freedom and mobility.However,the syntheses of poly[2]catenane gels reported to date all rely on the polymer as the backbone.Herein,we prepared poly[2]catenane gels based on entirely sequential assembly of small molecules.Monomer M1 with two unclosed rings was first prepared,which self-assembled to form supramolecular polymers(SPs)via hydrogen bonding andπ-πinteractions.Upon adding small molecule monomers M2 and M3 with aldehyde groups,ring closing of SPs occurred because the amino groups in the SPs reacted with M2 to form imine bonds.In addition,M3,which had twice the number of aldehyde groups as M2,enabled SPs to ring-close,causing the proceeding of crosslinking process at the same time.Thus linear SPs were transformed into poly[2]catenane gel networks.Due to the presence of hydrogen bonds in the poly[2]catenane gel,the gel also possessed stimulus responsiveness and self-healing properties.

Mechanical Properties and Fracture Behavior of Laminated Heterostructured Composites Under Different Current Densities

The mechanical properties and fracture morphologies of Cu/Nb multilayer composites under electric-assisted tension(EAT)were investigated.Results show that the generated Joule-heat leads to obvious stress softening with the increase in current density.However,the elongation decreases,which is closely related to the characteristic fracture behavior of Cu/Nb multilayer composites during EAT.The fracture pattern is gradually transformed from ductile fracture to melt fracture with the increase in current density.

Reinforcement size effect on thermal conductivity in Cu-B/diamond composite

With the miniaturization and integration of microelectronic components,power density of electronic devices such as integrated circuits,light emitting diodes(LEDs),and semiconductor lasers increases dramatically[1].Traditional thermal management materials are difficult to maintain the safety and reliability of the highpower devices.