EQUILIBRIUM PHASE DIAGRAMS IN SYSTEM CuO-PbO-Ag

Phase equilibrium in the ternary CuO-PbO-Ag system has been investigated using differential thermal analysis(DTA),thermogravimetry(TG),scanning electron microscopy(SEM) and X-ray diffraction(XRD) techniques.In the ternary CuO-PbO-Ag system,there is a eutectic reaction CuO+PbO+Ag=L at 750℃ and a composition of 12.04 mol.% Ag,16.35 mol.% CuO and 71.61 mol.% PbO.Two miscibility gaps near the two binary tie lines PbO-Ag and CuO-Ag were detected. No binary or ternary compound was detected in the ternary system.SEM and energy dispersive spectroscopy(EDS) confirm the presence of two liquid phases and the eutectic point.

The fouling properties of SiO2-CaO-P2O5 system in high-temperature rotary kiln phosphoric acid process

Kiln phosphoric acid(KPA)technology could produce P2O5 with high purity and has been applied in thermal phosphoric acid industry;however the formation of fouling in the high-temperature rotary kiln restricts the stable and long-term operation.In this paper,the reaction of phosphate ores with gaseous P2O5 was investigated in a high-temperature reactor,and the Ca O-SiO2-P2O5 ternary phase diagram was analyzed to understand the fouling formation mechanism.The results showed that the low-melting-point products,such as Ca(PO3)2and Ca2P2O7,are responsible for the fouling in the KPA process.In addition,a small amount of impurities,e.g.,aluminum and iron,could facilitate the generation of the low-melting-point products and cause serious fouling.Based on the high-temperature SiO2-P2O5 and CaO-SiO2-P2O5 phase diagram analysis,the control of Si/Ca molar ratio(e.g.,Si/Ca=2.0)was found to avoid fouling formation in the kiln.These results could provide the operation parameters of reaction temperature and feeds composition to suppress the fouling in the kiln reactor for the phosphoric acid production in industry.

网络环境下信息计量应用实证分析

本文以布拉德福定律为理论基础对CNKI数据库中信息科学专辑的期刊进行Web下载总频次分布规律实证研究,采用区域分析法得到布拉德福曲线,分析后指出在网络信息计量中期刊Web下载总频次分布规律基本符合布拉德福定律。

Sedimentology,provenance and geochronology of the Miocene Qiuwu Formation:Implication for the uplift history of Southern Tibet

Located on the south of the Gangdese,the Qiuwu Formation has traditionally been considered as Eocene coal-bearing clastic sediments consisting of sandstone,mudstone and conglomerate,unconformably on top of Gangdese batholith.However,its precise age and depositional environment remain ambiguous.Here,we present a newly measured stratigraphic section near the Ngamring County,western Xigaze.Detrital zircon U-Pb ages were also applied to trace the provenance of sediments and to constrain the maximum depositional age of the Qiuwu Formation.Sedimentary facies analyses indicate subaqueous fan and alluvial fan depositional environments.Clast composition of the conglomerate is dominated by magmatic rocks at the lower part,while chert and mafic detritus occur in the upper part,suggesting a southern source.Sandstone modal analyses indicate that the compositions of quartz,feldspar and lithic grains changed from transitional arc to dissected arc,implying the unroofing of the Gangdese arc.Detrital zircon U-Pb ages of the Qiuwu Formation are compared with those from Gangdese magmatic rocks and Yarlung-Zangbo ophiolites,suggesting that the Gangdese arc is a main source of the Qiuwu detritus and that the southern source played a role during the later stage.The major peak of detrital zircon ages is at 45-55 Ma,which corresponds to Linzizong volcanic rocks in southern Gangdese arc.The weighted mean age of the five youngest zircons from the lower part of the section is 21.0 ± 2.2 Ma,suggesting that the Qiuwu Formation was deposited in early Miocene,coeval with other conglomerates exposed along the southern margin of Gangdese.Combining new observations with previously published data,we propose that the provenance of the Qiuwu Formation had shifted from a single northern source to double sources from both the north and the south.Activities of Great Counter Thrust were primarily responsible for the shift by making the south area a high elevation to provide sediments for the Qiuwu Formation.

Prediction of Forming Limit Diagrams for Materials with HCP Structure

The forming limit diagram（FLD） is an important tool to be used when characterizing the formability of metallic sheets used in metal forming processes. Experimental measurement and determination of the FLD is timeconsuming and therefore the analytical prediction based on theory of plasticity and instability criteria allows a direct and efficient methodology to obtain critical values at different loading paths, thus carrying significant practical importance.However, the accuracy of the plastic instability prediction is strongly dependent on the choice of the material constitutive model [1–3]. Particularly for materials with hexagonal close packed（HCP） crystallographic structure, they have a very limited number of active slip systems at room temperature and demonstrate a strong asymmetry between yielding in tension and compression [4, 5]. Not only the magnitude of the yield locus changes, but also the shape of the yield surface is evolving during the plastic deformation [4]. Conventional phenomenological constitutive models of plasticity fail to capture this unconventional mechanical behavior [4, 6]. Cazacu and Plunkett [6] have proposed generic yield criteria, by using the transformed principal stress, to account for the initial plastic anisotropy and strength differential（SD） effect simultaneously. In this contribution, a generic FLD MATLAB script was developed based on Marciniak–Kuczynski analytical theory and applied to predict the localized necking. The influence of asymmetrical effect on the FLD was evaluated. Several yield functions such as von Mises, Hill, Barlat89, and Cazacu06 were incorporated into analysis. The paper also presents and discusses the influence of different hardening laws on the formability of materials with HCP crystal structures. The findings indicate that the plastic instability theory coupled with Cazacu model can adequately predict the onset of localized necking for HCP materials under different strain paths.