Jin-Shuang Guo

The effect of nanoscale SiC particles on the microstructure of Al2O3 ceramics

Abstract The hot-pressing temperature, matrix grain size, fracture mode and the distribution of SiC were studied to reveal the effect of SiC inclusions on the microstructure of Al 2 O 3 . Al 2 O 3 –SiC composite powder was prepared by the precipitation method. Nanoscale SiC particles were coated with Al 2 O 3 . After hot pressing, most of nanoscale SiC particles were randomly located within the Al 2 O 3 grains. SiC inclusions raised the hot-pressing temperature, decreased Al 2 O 3 grain size, and inhibited the abnormal grain growth of Al 2 O 3 . The intergranular fracture for Al 2 O 3 was transformed to the intragranular fracture for Al 2 O 3 –SiC nanocomposites because of the addition of SiC. All those microstructure changes increased the mechanical properties of Al 2 O 3 -composites by 40%.

Different effects of a cotemplate and [(transition-metal)(1,10-phenanthroline)(m)]2+ (m = 1-3) complex cations on the self-assembly of a series of hybrid selenidostannates showing combined optical properties of organic and inorganic components.

1,10-Phenanthroline (phen) and monoprotonated methylamine molecules were used as a novel cotemplate to direct the formation of a new inorganic-organic hybrid selenidostannate, (CH(3)NH(3))(4)(Sn(2)Se(6))·6phen (1); while the utilization of three types of transition-metal (TM) phen complex cations with the TM/phen ration of 1:1, 1:2, and 1:3 as structure directors affords {[Mn(phen)(2)](2)(μ(2)-Sn(2)Se(6))}·H(2)O (2a), {[Fe(phen)(2)](2)(μ(2)-Sn(2)Se(6))} (2b), {[Mn(phen)](2)(μ(4)-Sn(2)Se(6))}(n) (3), {[Mn(phen)(2)](Sn(2)Se(5))}(n) (4), and [Fe(phen)(3)](n)(Sn(3)Se(7))(n)·1.25nH(2)O (5). These compounds show diverse structures with the selenidostannate anions varying from discrete, μ(2)- and μ(4)- (Sn(2)Se(6))(4-) anions, to one-dimensional (1-D) (1)(∞)(Sn(2)Se(5)(2-)) anionic chains, and two-dimensional (2-D) extended (2)(∞)(Sn(3)Se(7)(2-)) anionic layers, demonstrating different structure-directing abilities of the cotemplate and the three types of TM phen complex cations. This work clearly indicates that the approach of modifying the number of the free coordination sites of unsaturated TM phen complex cations is very exciting as a way to synthesize novel hybrid chalcogenidometalates. Of particular interest, the present compounds exhibit interesting optical properties that reflect the combined effects of both photoluminescence-active organic components and semiconducting inorganic chalcogenidometalate anionic networks.

A highly stable 3D acentric zinc metal-organic framework based on two symmetrical flexible ligands: high second-harmonic-generation efficiency and tunable photoluminescence.

A 3D metal-organic framework (MOF), [Zn(BPHY)(SA)]n (1; BPHY = 1,2-bis(4-pyridyl)hydrazine, H2SA = succinic acid), which crystallizes in a noncentrosysmmetric space group (Cc), has been solvothermally obtained and testified to be a good nonlinear-optical material with the largest second-harmonic-generation response among the known MOFs based on sysmmetric ligands and high stability. Ultraviolet-to-visible tunable emission for 1 is observed.