Phase diagram of the Fe-rich portion of R-Fe-Al pseudoternary system(R=Dy_(0.65)Tb_(0.25)Pr_(0.1))

The 1000℃ isothermal section of the Fe-rich portion of R-Fe-Al(R=Dy0.65Tb0.25Pr0.1) pseudoternary system has been investigated using optical microscopy,X-ray diffraction,EPMA and DTA techniques.The 1000℃ isothermal section consists of 9 single-phase regions,14 two-phase regions and 6 three-phase regions.In the R-Fe pseudobinary system,except the R2Fe17 compound,the homogeneity regions of other compounds are shifted towards the stoichiometric rare earth-rich side.With Fe partially substituted by Al,the homogeneity region of R(Fe1-xAlx)2 is shifted back to the stoichiometric composition when x=0.15 and remains little changed with 0.15≤x≤0.30.The homogeneity regions of R(Fe1-xAlx)3 and R6(Fe1-xAlx)23 are slightly shifted to the stoichiometric rare earth-rich side with increasing Al content.A vertical section along R=33.33 atomic percentage is also investigated.It consists of 2 single-phase regions,4 two-phase regions and 2 three-phase regions.     

Effect of Different Kinds of Zinc (Ⅱ) on Early Hydration of Calcium Aluminate Cement

The early hydration of calcium aluminate cement (CAC) with different kinds of zinc (II),such as ZnSO_4g7H_2O,ZnO,Zn(NO_3)_2·6H_2O and ZnCl_2,was analyzed.Changes in consistency,setting time,hydration heat flow,hydration heat amount,ion concentration in solution,and hydration products were found upon the addition of different Zn~(2+).The water consumption of standard consistency of CAC is decreased with different Zn~(2+).Zn~(2+) can delay the initial hydration of CAC.The induction period of cement with Zn~(2+) is longer than that of CAC,especially the reaction time of the acceleration period is extended.Zn~(2+) can promote hydration hydrate of CAC at 24 h.The characteristic diffraction peaks of CA and CA_2 in CAC with different Zn~(2+) are significantly reduced.It can inhibit the formation of CAH_(10 )and promote the formation C_3AH_6 and AH_3 in hydration products at 24 h.     

Time-Temperature-Transformation (TTT) Diagram of Epoxy-terminated Poly(Phenylene ether ketone)

1IntroductionTheprocessingofathermosettingpolymerisnotonlyaph}'sicalprocess.TheincreaseinviscosityastheresinistransformedintocrosslinkednetWorksisamaincharacter,hencetheviscosityvariationbeconflesmorecomplex.Generally,thecompletionofcureiscarriedoutunderaconstanttemperature.Thetransformationsoccurringintheisoth,ermalcureofthermosettingresinsmayleadtotWodistinCttransitions:gelationandvitrification.Gelationcorrespondstotheincipientformationofanabatenetworkofcrosslinkedpolymermolecules.Vitrific…     

Self-assembling Synthesis of Vanadium Oxide Nanotubes and Simple Determination of the Content of V(IV)

1　IntroductionInrecentyears ,nanoscaleone dimensionalmaterialsattractmuchattentionduetotheirremarkablephysico chemicalpropertiesandagreatpotentialfornanodevices [1] .Theoutstandingstructuralversatilityofvanadiumox idesandderivedcompoundsisreceivingsignificantatten tionespeciallywithrespecttoapplicationsincatalysisandaselectrochemicaldevices[2 -4] .Recently ,Nesperandco workershavesynthesizedthenovelvanadiumoxidenano tubeinasol gelreactionfollowedbyhydrothermaltreat mentfromvanadiumalkoxidepre…     

Synthesis and Characterization of Poly(L-lactide-co-glycolide)

1Introduction Poly(lactide co glycolides)(PLGA)isawidelyin vestigatedbiodegradablecopolymer.Thebiocompatible andbiodegradablepolymersaresafeinthebodyandare hydrolyzedintometabolicby products.Recentlythese polyestermaterialshavebeenextensivelyusedinbiomate…     

Promotion effect of KOH on preparation of dissolved Fe(Ⅵ)

In order to improve the yield and stability of ferrate in solution, dissolved Fe(Ⅵ) prepared with NaOH and KOH respectively was compared in this study. The results showed that KOH is more suitable than NaOH for the preparation of dissolved Fe(Ⅵ) at temperature over 50 ℃. It is found that the dissolved Fe(Ⅵ) prepared with KOH increases quickly at first, and then slowly with the increasing concentrations of OH-and ClO-, while it increases rapidly at first and then decreases rapidly with the increasing dosage of Fe(NO3)3·9H2O. These results are different from that prepared with NaOH. It can be explained that solid K2FeO4 salts can be formed in KOH solution, and it will lower the Fe(Ⅵ) concentration, counteract the decomposition of Fe(Ⅵ), and improve the yield of Fe(Ⅵ). The maximum ferrate concentration is 0.163 mol/L obtained by 100 g/L Fe(NO3)3·9H2O and 6.16 mol/L KOH at 65 ℃. The stability of Fe(VI) is greatly improved due to the hypochlorite existed in the dissolved ferrate, and only 24% Fe(Ⅵ) has been decomposed after 16 d for 1 mmol/L Fe(Ⅵ) at 25 ℃.     

Journal of University of Science and Technology Beijing (English Edition)

Vol.14(2007), No.1-6Mineral GIS-based 3D limit equilibrium analysis for design optimization of a 600 m high slope in an open pit mine Meifeng Cai, Mowen Xie, and Chunlei Li .............................................................................................................. (1) Application of a microseismic monitoring system in deep mining Chengxiang Yang, Zhouquan Luo, Guobin Hu, and Xiaoming Liu........................................................................ (6) A ne…     

Retention of clay-solidified grouting curtain to Cd~(2 ), Pb~(2 ) and Hg~(2 ) in landfill of municipal solid waste

1　INTRODUCTIONIntheseyears ,innocuitytreatmentofmunicipalsolidwaste (MSW )hasincreasedgreatlyand 95 %isattributedtosanitaryandsemi sanitarylandfillswiththelandfillsbeingconstructedinarapidprogressinChina.Itisveryimportantforlandfillsto preventseepageofleachateincludingheavymetalsfromlandfillsintotheenvironment.Manyresearchershavestudiedtheanti seepagetechnology .Forexample ,Philip[1 ] investigatedcontaminationtransportprocessthroughsingle phasecement bentoniteslurrywallbytriaxialcelle…     

From the Journal of University of Science and Technology Beijing (in Chinese)

Evaluation on Structure Damage Due to Heavy Rain in Hard Composite Rock-mass in Subsidence Area Based on the displacement.stree and energy coupled monitoring technique.the trends of subsi     

Effect of Cu~(2+) concentration on hydrogen fermentation

0　INTRODUCTIONHydrogenisconsideredtobeanidealsourceofener gyforthefuturebecauseitiseasilyconvertedtoelectricityandiscleanlycombustible .Whetherfromeconomicoren vironmentalstandpoints ,biologicalhydrogenproductionwasmostpromising .Biologicalhydrogenproductionhasbeenwidelyin vestigated .Microorganismsforhydrogenproductioncanbedividedintotwogroups :photosyntheticanaerobicbacteriaandanaerobicfermentativebacteria[1] .Thelatterdiges tiononlyrequiresalowenergyanddoesnotrequirephotoenergy .Ther…     

Chemial Bond and Stability of Adsorption of [Au（ AsS3 ）]^2- on the Surface of Kaolinite

Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au( AsS3 )]^2- on the surface of kaolinite. The correlation among structure, chemical bond and stability was discussed. Several models were selected with [ Au( AsS3)]^2- in different directions and sites. The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au - 0 covalent bond, so these models are more stable than those with gold above or under the layer. The models with gold near to [ AlO2(OH)4] octahedra are more stable than those with gold near to the vacancy withont aluminium. These two stable tendencies in kaolinite- [ Au( AsS3)]^2- are stronger than that in kaolinite-Au systems. The interaction between [ Au( AsS3 )]^2- and kaolinite is stronger than that between gold and kaolinite, and this interaction is strong enough to form the surface complexes.     

Quantum Chemistry Calculations on the Interaction Between Kaolinite and Gold

The density function and discrete variation method ( DFT - DVM) is used to study the interaction between kaolinite and gold. The correlation among the structure, chemical bond and stability is discussed. Several models are selected without gold and with gold in different directions and sites . The results show that the models with gold on the edge of kaolinite basal layer are more stable than those with gold above or under the layer, the models ivith gold near to [ A1O2 ( OH)4 ] octahedra are more stable than those with gold near to the vacancy without aluminium. The interaction between gold and the surface ions of kaolinite is strong enough to form the surface complexes.     

Interface Characteristics Between Colloidal Gold and Kaolinite Surface by XPS

The distribution of gold colloids in kaolinite and the interaction between gold and kaolinite surface were investigated by transmission electron mieroscotgy （TEM） and X-ray photoelectron spectroscopy （ XPS ）. There is strong interaction between the gold particles and the edge surfaces of kaolinite, in low pH solution, the edge surface of kaolinite is positively charged and electrostutic attrcactive force between colloide gold panicles and the positive edge surface of kaolinite woald facilitate the adsorption of colloidal gold particles onto the suface. TEM observation shows that the aggregate morphology of gold particles was dominated by particle-particle interaction and gold particles were adsorbed on the edge surface of kaolinite crystals , resulting from the electrostatic attractive force between colloidal gold particles and the positice surfaces of kaolinite. XPS data show that in Au4 f electron spectra there are four energy peaks related to gold, 83.8 eV, 85.7 eV, 87.5 eV, and 89.4 eV, respectively, which suggests that in chemical states there are metallic gold and Au bonded to O, similar to the form of Au2O3 , and composite Au2O3 is formed between the edge surface of kaolinite and colloidal gold surface.     

高岭石矿物表面化学的量子化学研究

用量子化学的理论和计算方法，研究高岭石表面的化学状态、表面化学活性位置及其成键特征、结果表明，高岭石分子簇的最高占据轨道基本上是由上、下表面的一些氧原子组成的，且具有较高的能态，说明这些位置具有较高的化学活性，易于与获得电子能力较强的物质形成化学键。而其最低空轨道则主要由硅、铝和少量的侧面O原子组成．相对而言，能级较低，易于与提供电子的体系作用，其化学反应活性较大。因此，当高岭石与带负电荷的离子或离子基团作用时，可能在侧面的位置形成表面化合物。Al和Si都是组成LUMO分子轨道的主要成分，但Al原子的化学活性要大于Si原子，因此，当高岭石表面与提供电子的体系发生化学作用时，最可能的位置应该是八面体的Al原子。     

Aun Y(n=1-5)团簇的结构与稳定性研究

用相对论有效原子实势(RECP)和密度泛函(B3LYP)理论,选择LANL2DZ基组研究了AunY(n=1-5)团簇的各种几何结构及稳定性.结果表明AuY、Au2Y和Au3Y团簇的基态几何构型是平面结构,Au4Y和Au5Y的基态构型是三维结构.通过计算原子平均结合能、二阶差分能量、破碎能量及能级间隙判断AunY(n=1...     

Mechanism of gold dissolving in alkaline thiourea solution

Reaction mechanism of gold dissolving in alkaline thiourea solution was studied by electrochemical methods,such as cyclic voltammetry,chronopotentiometry,AC impedance,linear sweep voltammetry.Apparent activation energy of anodic process of gold electrode dissolving in alkaline thiourea solution is 14.91 kJ/mol.Rate determining step is the process of gold thiourea complex diffusing away from electrode surface to solution.The results of AC impedance and chronopotentiometry indicate that thiourea adsorbs on gold electrode surface before dissolving in solution.There does not exist proceeding chemical reactions.Formamidine disulfide,the decomposed product of thiourea,does not participate the process of gold dissolution and thiourea complex.Species with electro-activity produced in the process of electrode reaction adsorbs on the electrode surface.In alkaline thiourea solution,gold dissolving mechanism undergoes the following courses:adsorption of thiourea on electrode surface;charge transfer from gold atom to thiourea molecule;Au[SC(NH2)2]ads receiving a thiourea molecule and forming stable Au[SC(NH2)2]2 ;and then Au[SC(NH2)2]2 diffusing away from the electrode surface to solution,the last step is the rate-determining one.     

Electronic Structure and Chemical Bond of Ti3SiC2 and Adding Al Element

The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation （ DFT- DVM） method. When Al element is added into Ti3 SiC2 , there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3 SiC2 , adding a proper quantity of Al can promote the formation of Ti3 SiC2 . The density of stnte shows that there is a mixed conductor character in both of Ti3 SiC2 and adding Al element. Ti3 SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.     

Reaction Activity of Kaolinite Surfaces：Quantum Chemistry Calculations

The anion-kaolinite surface infractions and AuS - adsorption onto the surfaces of kaolinite were studied using the self-consistent-field discrete variation ( SCF - Xα - DV) method. Electronic structure and energies of the system of anion AuS- adsorbed on an atomic cluster of kaolinite were calculated. The results show that the systems with lower total energy are those AuS- adsorbed on the edge surfaces, which indicates that the systems of adsorption of AuS- on the edges are more stable relative to those adsorbed on the basal plane. On the other hand, bond order data suggest that significant shifting of atomic charge and the overlapping of electronic cloud between Au ( Ⅰ ) of the AuS- and the surface ions of kaolinite would take place in the systems with AuS - being adsorbed on the edges, especially at the she near A1 octahedra. Therqrore, it can be concluded that edge sites will dominate the complexation reactions of the surfaces of kaolinite, with negligible contributions from other fimctional groups on the basal plane, which are dominated by either siloxane sites in silica layers or aluminol sites in gibbsite layers.     

Electron bandstructure of kaolinite and its mechanism of flotation using dodecylamine as collector

The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the structure of kaolinite bulk and slab models. The results show that Fermi energy of kaolinite (001) plane is 3.05 eV, and the band gap is 4.52 eV. The partial density of states (PDOS) of kaolinite (001) plane indicates that Al—O and Si—O bonds on the mineral surface are highly polar. The oxygen atoms of hydroxyl groups in surface layer are capable of forming hydrogen bond with the head group of cationic collectors. The properties of dodecylamine (DDA) cation were also calculated by density function theory (DFT) method at B3LYP/6-31G (d) level for illuminating the flotation processes of kaolinite. Besides the electrostatic attraction, the mechanism between kaolinite and DDA is found to be hydrogen bonds under acidic condition. Foundation item: Project(2005CB623701) supported by the Major State Basic Research and Development Program of China; Project(50874118) supported by the National Nature Science Foundation of China; Project(2007B52) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China     

STUDY ON SELECTIVE DISSOLUTION OF GOLD IN ALKALINE THIOUREA MEDIA

Manyresearches[1-3)ondissolutionofgoldinacidicsolutionsofthioureahavebeenreportedsincePlaksin.Generally,itwasconsideredthatthereaction(1)resultsindissolutionofgoldinthioureasolution.An[CS(NH,)sj' e~An ZCS(NH,)2E'~0.38V(1)NH,(NH)CSSC(NH)NH, ZH Ze~ZCS(NH,),E0-0.42V(2)CharleyWRetalthoughtthatthereaction(2)occurredfastly,theproductformamidinedisulfidewasanactiveoxidantandwasveryimportantduringthedissolutionofgold@@['j.However,theconclusionswerelimitedonlyinacidicthioureadissolutio…