International Journal of Minerals, Metallurgy and Materials

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Rate Equation of Small Particle-Air Bubble Attachment in Turbulent Flow of Flotation Cells

1998, 5(4): 185-191.

中文摘要(232) PDF(10) SpringerLink

摘要:
A rate equation of small particle-air bubble attachment in the turbulent now of flotation cells has been derived. The equation, integrating both the collision probability and adhesion probability together, represents the probability of attachment between particle and bubble in the turbulent flow. “Capture efficiency” f(α) is introduced into the rate equation to reflect the influence of energy hairier on the attachment rate. Three typical situations of particle-bubble interaction in flotation process have been discussed. For a completely hydrophobic particle-bubble system,f(α) = 1. This means that all collision leads to attachment. Whereas for hydrophilic particle-bubble systems,.f(α) = 0. Thus no adhesion of particle on bubble occurs at all. In real notation circumstances, however, there always exists a certain energy barrier between the particle and the bubble. Therefore, f(α) = 0~1. In such cases, not all collisions result in particle-bubble attachment.

Metallurgy

Production of High Carbon Ferrochromium Using Melt Circulation

Yulong Ding, A J Merchant

1998, 5(4): 192-202.

中文摘要(245) PDF(14) SpringerLink

摘要:
Some fundamental studies related to the production of high carbon ferrochromium were summarized using melt circulation technology carried out in the School of Chemical Engineering at the University of Birmingham. These studies focused on the kinetics of chromite reduction in Fe-C(-Cr-Si) melts. The effects of feed mode,fluxes, amount and particle size of reductant, particle size of chromite, melt composition and the reduction temperature were investigated. The reduction mechanisms were discussed. The results showed that (1) the reduction rates of sintered chromite Pellets and non-compacted chromite powder in Fe-C(-Cr-Si) melts was generally very low,(2) addition of carbon in the non-compacted chromite feed greatly improved the reduction kinetics, (3) compaction of the carbon-chromite mixtures into composite Pellets further improved the reduction kinetics and (4) addition of lime in the composite Pellets increased the reduction rate, while the addition of silica may suppress the posihve effect of lime. It can be concluded that solid-state reduction, smelting reduction and dissolution proceed simultaneously during the reduction of compacted compostite pellets or non-compacted composite mixtures in Fe-C(-Cr-Si) melts,and the early stage of reduction is very likely to be controlled by either or both solid-state and/or gas diffusion through the oxide phases and/or the product layers.

Metallurgy

Mechanism of Cathode Process of B(Ⅲ) in LiF-NaF-KBF₄ Melt by Electrochemical Titration Technique

Qingrong Shi, Xindong Wang, Lianyu Yuan, Shuzhen Duan

1998, 5(4): 203-207.

中文摘要(183) PDF(9) SpringerLink

摘要:
The mechanism of cathode process of B(Ⅲ) at molybdenum and platinum electrodes in LiF-NaF-KBF₄ melt was studied and the transferred electron number of the reaction was calculated by means of cyclic voltammetry.The effect of adsorption of electroactive component on the electrochemical response (e.g., the voltammetric i─E curves) was analyzed and discussed. The "electrochemical spectra" for linear sweep voltammetry was used to elucidate the electrode reaction accompanied by a following transform process. The results show that the reduction of B(Ⅲ) to B(0) proceeds in reversible one step three-electron reaction and the cathode process of B(Ⅲ) is affected by product adsorbed strongly at the electrode surface. It is assumed that the reduction and deposition of B(Ⅲ) at molybdenum and platinum electrodes proceed in two kinds of mechanism: (1) B(Ⅲ)+ 3e = B_ads→ B (surface diffusion deposition mechanism) and (2) B(Ⅲ) + 3e = B (direct deposition mechanism).

Metallurgy

Calculating Model of Mass Action Concentrations for Mn-C Melts and Optimization of Thermodynamic Parameters

Jian Zhang

1998, 5(4): 208-211.

中文摘要(183) PDF(7) SpringerLink

摘要:
Based on the phase diagram, the coexistence theory of the metallic melt structure involving compound formation and the regularity of melts containing saturated phase, a calculating model of mass action concentrations for Mn-C melts was formulated. According to the activities (or activity coefficients γ_Mn and γ_C), obtained by the Unified Interaction Parameter Model (UIPM), the thermodynamic parameters △G_Mn₃C^⊝ and △G_Mn₅C₂^⊝ at higher temperatures (1628~1873 K) were optimized by the repeated try and error method. It is testified that △G_{Mn₂₃C_n}^⊝, △G_Mn₁₅C₄^⊝(873~1273 K) and △G_Mn₇C₃^⊝ (298~1623 K), obtained at lower temperatures, can also be used at the above-mentioned higher temperatures. The calculated N_Mn and N_C agree well with α_Mn and α_C obtained by UIPM. This result shows that the deduced model can reflect the structural reality of Mn-C melts.

Metallurgy

Re-assessment and Optimization of the Ga-M (M = In, Sb,Pb) Systems with Chemsage

Xianran Xing, Thiyu Qiao, Herbert IPser

1998, 5(4): 212-218.

中文摘要(261) PDF(9) SpringerLink

摘要:
The thermodynamic properties and the phase diagrams of the systems Ga-M (M = In, Sb, Ph) were critically re-assessed and optimized employing the software package ChemSage for the calculation of thermodynamic equilibria. The Redlich-Kister/Margules formalism was employed for all solution phases and sets of self-consistent thermodynamic parameters were obtained. The results of re-assessment and optimization are compared with previous work, they are in excellent agreement with most experimental data.

Metallurgy

Thermodynamic Assessment of Reactions between Yttrium and Tramp Elements in Petroleum Pipe Steel

Aixue Sha, Lüren Dong, Shangyi Li

1998, 5(4): 219-222.

中文摘要(237) PDF(7) SpringerLink

摘要:
In the thermodynamic evaluation Y was selected as a typical heavy rare earth metal for reducing the detrmental effects of tramp elements in the petroleum pipe steel. The possibilities of reactions between Y and tramp elements such as Sn, Sb, As, etc. after deoxidation and desulphurization were estimated by calculating the Gibbs free energies of formation. The equilibrium content of Y for eliminating the detrimental effects of tramp elements in the steel was recommended from the results of thermodynamic calculation.

Materials

Redistribution of Boron during Ferrite Reaction in Nb-B Microalloyed Steel

Shanwu Yang, Xinlai He

1998, 5(4): 223-227.

中文摘要(211) PDF(9) SpringerLink

摘要:
By contrast of microstructure and boron distribution in the same area of samples, the behavior of boron during ferrite reaction in Nb-B microalloyed steel was studied. Boron atoms have segregated to original austenite boundaries betfore ferrite reaction starts during isothermal treatment. The concentration of boron in small Pieces of ferrite foming along austenite boundaries may be remarkably higher than that in austenite matrix, but it will reduce gradually when the ferrite continuously grows. There is no obvious boron segregation on interface of γ/α and α/α.These facts indicate that ferrite growth is not controlled by diffusion of boron in austenite.

Materials

Nonclassical Plane-crystallographic Groups and Their Applications IV

Lequan Min, Xaodan Zhang

1998, 5(4): 228-232.

中文摘要(269) PDF(7) SpringerLink

摘要:
Eight kinds of nonclasslcal periodic lattices with locally 8-fold rotational symmetries are introduced.They can be described via nonclassical Planc-crystallographic groups. The periodic lattices may be interpreted by the projections on the plane of the corresponding unit cells consisting of embedding polyhedrons, respectively. The Fourier-transform patterns of the Periodic lattices have striking approximate "8-fold rotational symmetries", some of which are similar to those displaying in the electrton-diffraction patterns of so-called quasicrystals.

Materials

Reaction Sintering of Fe-Al Powder Mechanically Activated

Chengchang jia, Xiaosen Lü, Jun Zhao, Zizhang Xie

1998, 5(4): 233-236.

中文摘要(252) PDF(8) SpringerLink

摘要:
The mixture of Fe and Al powder was mechanically activated and sintered to study a non-melting method of producing the intermetallics Fe₃Al. High-energy ball milling was used as an activation method, X-ray diffraction and SEM were chosen to analyze the materials variation before and after activation and sintering, and hot press of Fe-Al powder was inveshgated to compare mechanical activation with sintering. The results show that combining mechanical activation with reaction sintering can complete the transformation from pure Fe and Al powder to intermetallics. It is difficult to do the transformation by either mechanical activation or hot press.

Materials

Prediction and Control of Both Wrinkle Limit and Fracture Limit on Cylindrical Cup Deep-Drawing

Junxiang Lei

1998, 5(4): 237-240,250.

中文摘要(274) PDF(8) SpringerLink

摘要:
hased on both the wrinkle model and fracturc model, the wrinkle critical tangent pressure and the fracture on critical radial tensile stress are calculated respectively. The maximum tangent pressure formula in the flange deformation zone and the maximum radial tensile stress formula in the cylinder-wall pass force zone are given, and both the no-wrinkle limitl criterion and no-fracture limit criterion are put froward. The prediction and control criterion and diagram of both the wrinkle limit and fracture limit on cylindrical cup deep-drawing, the most suitable forming zone and the limit deep-drawing coefficient are obtained. Comparing with present experience formulae and actual product's production, this prediction and control are quite accurate.

Materials

Preparation and Application of C60 High Performance Concrete

Jizhong Li

1998, 5(4): 241-244.

中文摘要(253) PDF(9) SpringerLink

摘要:
C60 High Performance Concrete (HPC) was prepared by limiting cement content and adopting composite superplasticizer, low-alkalinity expansive agent and high-quality line mixture. The results showed that the performance of the prepared C60 HPC was excellent. By adopting some advanced construction techniques such as using secondary vibration and secondary face compaction, controlling temperature difference and paying special attention to early curing in the construction process, the prepared C60 HPC had been successfully applied in the monolithic structure of huge building.

Automation

Algorithm for Computation of Unstructured Real Stability Radius and Its Applications

Xiaodan Zhang, Lequan Min

1998, 5(4): 245-250.

中文摘要(258) PDF(7) SpringerLink

摘要:
An algorithm for the computation of the unstructured real stability radius of high dimensional linear system is presented. Using the accurate formula of the real stability radius of 2-dimensional system linear system checks the algorithm. The result shows that the algorithm is reliable and efficient. As applications, the unstructured real stability radii of 2-dimensional Chua's circuit and 3-dimensional piecewise-linear system are calculated, the dynamical orbits of the corresponding perturbed systems are simulated.

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1998年第5卷第4期