Control of Melt Structures on Cu-Au Mineralization in Basic-Ultrabasic Complexes of Northern China

Based on systematic analyses of 72 samples of different basic-ultrabasic rocks, the present paper discusses the relationship between melt structure and Cu and Au mineralization. It is found that if the NBO/T, NBO, M2+, FeO and MgO values are relatively high and the T, M3+, Fe2O3 and CaO values are low the basic-ultrabasic melt will be favourable to Cu (Ni) mineralization, but if the former are low and the latter are high it is favourable to Au metallization. Cu ions occupy dominantly octahedra in basic-ultrabasic melt and the higher the NBO/T, NBO and M2+ values, the more the octahedra in the melt. Au element mainly takes the form of Au+ ions in basic-ultrabasic melt and the Au+ ions constitute tetrahedral sites together with Fe3+ ions. Therefore, low M2+ and high Fe3+, i.e. high oxygen fu-gacity, can promote the enrichment of Au+ ions and Au mineralization. Components NT (other than Au+), Al2O3 and SiO2 in basic-ultrabasic melt have no effect on metallogenetic species. As mentioned above, in relevant diagrams distribution areas of the characteristic values of ore-free melt and those of ore-forming melt are overlapped in different degrees, which possibly indicates that not all the magmas have mineralizing ability. It can be well distinguished whether basic-ultrabasic rocks are favourable to Cu or Au mineralization or they are just ore-free rocks by analysing integrated diagrams of the characteristic values of the magmatic melt structure.

COMPUTER SIMULATION OF STRUCTURE OF La-LaCl_3-KCl MELT

The structure of the La-LaCl_3-KCl molten system at 1223K has been investigated by computer simulation using Monte Carlo method.The partial radial distribution functions of some ion pair as well as the potential and internal energy of the system at 1223K have been calculated.The results implies that about 50% of La(Ⅲ)is six coordinated and LaCl_4^(2-) tetrahedron is the predominant configuration for La(Ⅱ). It is also concluded that the distribution of free space in the molten system is not uniform.There exist many fissures and empty holes in the molten salt.

Structure and property of metal melt Ⅱ—Evolution of atomic clusters in the not high temperature range above liquidus

Based on the theory of micro-inhomogeneity of liquid metal,a calculation model is established for the quantitative description of the structural information of metal melts.Only by thermophysical property parameters and basic structural parameters of solid metal,can this model produce the main information of melt structure,including the relative concentration of active atoms,size of atomic clusters and number of short-range order atoms.Based on this model,the main structural information of Al and Ni melts in the not high range above the liquidus is calculated,with results in good agreement with experimental values.Besides,analyzed is the influence of superheating temperature and atomic number on the melt structural information of the first (IA) and second main group (IIA) elements.With temperature increasing,melt structural information regularly changes for both IA and IIA elements.With the atomic number increasing,melt structural information of IA elements changes regularly,for the crystal structures of the IA elements are all of bcc lattice type.However,no notable regular change of melt structural information for IIA elements has been found,mainly because the lattice type of IIA elements is of hcp-fcc-bcc transition.The present work presents an effective way for better understanding metal melt structure and for forecasting the change of the physical property of metal melts.

Wetting behavior of CaO-Al_(2)O_(3)-based mold flux with various BaO and MgO contents on the steel substrate

The Interfacial phenomena in mold have a great impact on the smooth operation of continuous casting process and the quality of the casting product.In this paper,the wetting behavior of CaO-Al_(2)O_(3)-based mold flux with different BaO and MgO contents was studied.The results showed that the contact angle between molten flux and interstitial free(IF)steel substrate increased from 62.4°to 74.5°with the increase of BaO content from 3 wt%to 7 wt%,while it decreased from 62.4°to 51.3°with the increase of MgO content from 3 wt%to 7 wt%.The interfacial tension also increased from 1630.3 to 1740.8 mN/m when the BaO content increased,but it reduced from 1630.3 to 1539.7 mN/m with the addition of MgO.The changes of contact angle and interfacial tension were mainly due to the fact that the bridging oxygen(O^(0)) at the interface was broken into non-bridging oxygen(O^(-)) and free oxygen(O_(2-)) by MgO.However,more O^(-) and O_(2-) connected into O^(0) when BaO was added,since the charge compensation effect of BaO was so stronger that it offset the effect of providing O_(2-).

Hydrogen-induced amorphization of Zr-Cu-Ni-Al alloy

Arc melting was utilized in this study to produce Zr_(55)Cu_(30)Ni_5Al_(10) alloys under mixed atmospheres with various ratios of high-purity hydrogen to argon. The influences of hydrogen addition on the solidification structure and glass-forming ability of Zr_(55)Cu_(30)Ni_5Al_(10) alloy were determined by examining microstructures in different parts of the cast ingots. The results showed that different degrees of crystallization structures were obtained in the ascast button ingots after arc melting in high-purity Ar, and the cross-sectional solidification morphology of arcmelted ingots was found to consist of crystals with varying from the bottom up. By contrast, there were completely amorphous structures in the middle and upper areas of the as-cast button ingots fabricated by adding 10% H_2 to the high-purity Ar atmosphere. A clear solidification interface was found between the crystal and glass in the ascast button ingots, which indicates that hydrogen addition can enhance the Zr_(55)Cu_(30)Ni_5Al_(10) alloy's glass-forming ability. The precise mechanism responsible for this was also investigated.

Effect of AI_(2)O_(3)and MgO on crystallization and structure of Ca0-Si0_(2)-B_(2)0_(3)-based fluorine-free mold flux

The crytallization behavior and melt structure of the CaO-Si0^(2-)B20_(3)-based fluorine-free mold fux were investigated.The results show that the crytallization of the mold fux was first inhibited and then promoted with the increase in Al_(2)0_(3) content from 4 to 12 wt.%.However,it was enhanced by MgO in the range of 2-10 wt.%.The results of Fourier transform infrared spectroscopy and Raman spectroscopy showed that Al_(2)0_(3) worked as a network former in the mold flux melt when its content was in the range of 4-8 wt.%,whereas it worked as the network breaker to provide 0^(2-)when its content was in the range of 8-12 wt.%.In addition,the combined efects from the charge compensation by Mg^(2+)and the network broken by 0^(2-)led to the increase in some typicalT-O-T(AI-O-A1,B-O-B,etc.,)and simpler structural units(Q^(2)(Si),B_^(O-)in the[B0_(2)0^(-)],.etc.)when the MgO content was in the range of 2-6 wt.%.The continuous increase in 0^(2-)provided by the addition of MgO from 6 to 10 wt.%further depolymerized the network of the melt and fnally caused fast crystallizationo.

Structural behavior of F-in mould flux melt of CaO-SiO2-Al2 O3-Na2O-CaF2 system

The influence of fluorine on the structure of CaO Si（）e-Al2Oa Na2O-CaF2 continuous-casting-type slag was measured by Raman spectroscopy, and the degree of polymerization of mould flux and the structural behavior of F- in the melt were investigated by classifying and quantifying the structural species of F ions. The results exhibit that the main structural units of Si O tetrahedra are Q1, Q1 and Q2, and the actual measured number of non bridging oxygen ions in the [SiO4 ]-tetrahedra （denoted by NBO/T） in creases from 2. 73 to 3.44 with increasing the molar ratio of F to （F＋O） （denoted by XF/X（F-O ） from 0.06 to 0. 19. It means that the degree of polymerization o1 meh structure decreases with an increase in XE/X（F＋O）. In addition, most of F- ions were distributed in Si-O tetrahedra and Al-O tetrahedra. With increasing XF/X（F＋O）, the complex structural units Al-Otetrahedra are gradually replaced hy discrete structural units A1F4 because of the breakage of Al-O bonds in Al-Otetrahedra by F ions, and the SiO （bridging oxygen） bonds of SiO tetrahedra are broken to form [SiOnF1-n]-tetrahedra by F ions coordinating with Si4 ＋ .

Electrochemical Performance of Nanocrystalline and Amorphous Mg–Nd–Ni–Cu-Based Mg_2Ni-type Alloy Electrodes Used in Ni-MH Batteries

Nanocrystalline and amorphous Mg2Ni-type（Mg24Ni10Cu2）100–xNdx（x = 0, 5, 10, 15, 20） alloys were prepared by melt-spinning technology. The structures of as-cast and spun alloys were characterised by X-ray diffraction,scanning electron microscopy and transmission electron microscopy. Electrochemical performance of the alloy electrodes was measured using an automatic galvanostatic system. The electrochemical impedance spectra and Tafel polarisation curves of the alloy electrodes were plotted using an electrochemical work station. The hydrogen diffusion coefficients were calculated using the potential step method. Results indicate that all the as-cast alloys present a multiphase structure with Mg2 Ni type as the major phase with Mg6 Ni, Nd5Mg41 and Nd Ni as secondary phases. The secondary phases increased with the increasing Nd content. The as-spun Nd-free alloy exhibited nanocrystalline structure, whereas the as-spun Nd-doped alloys exhibited nanocrystalline and amorphous structures. These results suggest that adding Nd facilitates glass formation of Mg2Ni-type alloys. Melt spinning and Nd addition improved alloy electrochemical performance, which includes discharge potential characteristics, discharge capacity, electrochemical cycle stability and high-rate discharge ability.