The mechanism of extraction of gold by tetradecyldimethylbenzylammonium chloride (TDMBAC)/tri-n-butyl phosphate (TBP)/n-heptane solution from an aqueous alkaline cyanide solution was studied by means of extraction equilibrium, Karl Fischer titration, electrical conductivity, FTIR spectroscopy and dynamic laser scattering (DLS). When the gold concentration is lower than 3 g L À1 and the volume percentage of TBP is less than 10%, the plots of the extraction percentage of gold against the molar ratio of [TDMBA + ] to [Au(CN) 2 À ] and logD-log[TBP] (o) plot indicated that the stoichiometry of the extracted species is a 1 : 1 : 4 complex, TDMBA + : Au(CN) 2 À : TBP. Karl Fischer titration showed that 4 H 2 O molecules participate in the formation of such a species. Electrical conductivity measurements confirmed its ionic character. Fourier self-deconvolution of the O-H stretching bands revealed 4 different kinds of water molecules contained in the organic phase, some of which were bound to TBP via hydrogen bonding. A supramoleculefor the extracted species. Two TBP molecules are bound to [Au(CN) 2 À ] by two H 2 O bridges through hydrogen bonding, forming a [(RO) 3 P=OÁ Á ÁH-O-HÁ Á ÁN= =C-Au-CNÁ Á ÁH-O-HÁ Á ÁO ¼ P(OR) 3 ] À moiety. Two hydrated TBP molecules, (RO) 3 P=OÁ Á ÁH-O-H, surround [TDMBA + ] by ion-dipole interaction.The bulky anion and cation form a lipophilic supramolecule. The possible structure of the supramolecular anion was calculated with an ab initio molecular orbital (MO) method. The DLS study showed that mixing of TDMBAC and Au(CN) 2 À in the aqueous phase led to the formation of micelles. When an organic phase containing TBP was added to this aqueous phase, the complexes transferred into the organic phase and reversed micelles or a microemulsion (W/O) were formed when the gold concentration reached a certain limiting value.

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Ceramic-metal functionally graded materials (FGMs) have been extensively used in aerospace engineering where high strength and excellent heat insulation materials are desired. However, their performance depends highly on the internal residual stress, which is generated inevitably due to the thermal mismatch of ceramic and metal. In this paper, based on the nanoindentation test, the field distribution of the residual stress of porous ZrO2/(ZrO2+Ni) ceramic-metal FGMs is measured. The residual stress field measured by nanoindentation agrees qualitatively with the finite element simulation results. Then a constitutive relation is established to investigate the effects of residual stress on the macroscopic deformation behavior of porous ZrO2/(ZrO2+Ni) FGMs, which agrees well with the bending and compression experiments. It is found that residual stress can improve both the flexural strength and stiffness of the porous ZrO2/(ZrO2+Ni) FGMs, by densifying and compensating the tensile stress of the porous middle layer (ZrO2) during the bending process, respectively. However, it has no obvious influence on the ultimate compressive strength of the porous ZrO2/(ZrO2+Ni) FGMs, but mainly influences its initial stage of elastic deformation in the compressive behavior.

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