Quantitative x-ray photoelectron spectroscopy analysis of alkali ions / zirconia systems

Zirconia-supported alkali ions, containing Na, from 0.74 to 3.61 wt.%, and K, from 0.91 to 4.76 wt.%, have been studied by X-Ray Photoelectron Spectroscopy, X-ray diffraction and chemical analyses. The results show that the alkali ions remain dispersed on the zirconia surface. After treatment at 773 K in air, 5h, the Na containing samples maintain a good dispersion at low Na content, whereas for the more concentrated samples, agglomeration and incorporation in solid solution have been detected. The K based system shows neither agglomeration nor incorporation in solid solution of potassium ions. The XPS intensity ratios are compared with calculated values, according to different models, to account for the changes in surface morphology.     

Volume effects and associations in liquid alloys

The regular associated solution model for binary systems has been modified by incorporating the size of the complex as an explicit variable. The thermodynamic properties of the liquid alloy and the interactions between theA _μB type of complex and the unassociated atoms in anA-B binary have been evaluated as a function of relative size of the complex using the activity coefficients at infinite dilution and activity data at one other composition in the binary. The computational procedure adopted for determining the concentration of clusters and interaction energies in the associated liquid is similar to that proposed by Lele and Rao. The analysis has been applied to the thermodynamic mixing functions of liquid Al-Ca alloys believed to contain Al₂Ca associates. It is found that the size of the cluster significantly affects the interaction energies between the complex and the unassociated atoms, while the equilibrium constant and enthalpy change for the association reaction exhibit only minor variation, when the equations are fitted to experimental data. The interaction energy between unassociated free atoms remains virtually unaltered as the size of the complex is varied between extreme values. Accurate data on free energy, enthalpy, and volume of mixing at the same temperature on alloy systems with compound forming tendency would permit a rigorous test of the proposed model.     

High temperature thermodynamics of the Cr-Cr2N-N2 system

The high-temperature thermodynamic behavior of the Cr-Cr₂N-N₂ system has been investigated in the temperature range 1450 to 1850 K by measuring the equilibrium pressure of nitrogen gas over pure chromium metal and chromium nitride Cr₂N. From the experimental data, the standard free energy and enthalpy of formation of Cr₂N have been determined to be: ΔH° = −104. ± 10 (KJ. mol⁻¹ Cr₂N) ΔG° = −104. + 0.04987 ± 3.8 (KJ. mol⁻¹ Cr₂N)     

RE／S值对控轧低碳Mn－Nb－RE钢硫化物成分和形貌的影响

用扫描电镜测定了含０．０４１％～０．０７６％ＲＥ的低碳Ｍｎ－Ｎｂ－ＲＥ钢中硫化物的成分、大小和形貌。ＲＥ／Ｓ值为２．８～３．０时，钢中的硫化物充分变质。     

Study by SEM-EDS of the in situ dynamic leaching of mercury ores

The present work studies the surface evolution of cinnabar, when it is leached with HBr acid for different conditions. The dynamicin situ test has been studied by scanning electron microscopy and EDS techniques. According to the acid condition, time, and temperature, the HgS presents different mechanisms of dissolution, and the results prove that the cinnabar does not present “memory effect”, as proposed by other authors.¹⁶     

The Lazy Cook Problem, or Scheduling Two Parallel Machines to Optimize Vehicle Utilization

A cook has to prepare n cakes using an oven with two racks. According to the recipe, the i-th cake has to be baked for exactly a _i minutes. Cakes to be cooked are taken from a table and carried to the oven, and once cooked are carried back to the table by means of a trolley that can carry two cakes at a time. What is the minimum number q ^* of round trips required of the cook? This problem has application to the operation scheduling of transportation systems and to material cutting. A different problem arises according to whether the cook accepts or not to stay near the oven for awhile with the trolley. If the trolley cannot be idle at the oven, an optimum schedule with no oven idle-time always exists: consequently, the trolley schedule is trivial, and the problem is transformed into a set packing. For this case, we propose and test a heuristic method which generates all of the promising columns of the set packing, and solves the resulting problem by branch-and-bound. Instead, if the trolley can be idle at the oven for a limited amount of time, a problem arises to find an optimal schedule of the trolley: in this case we show how to use a scaling technique in order to obtain a very good feasible solution by the method above.     

Quilone试剂改性脲醛树脂——新型防水涂料的制备

叙述了Quilone试剂的合成,改性脲醛树脂的原理、实验方法、改性后脲醛树脂的抗水性、抗渗透性、耐化学药品性及其影响因素。     

Creep and stress-rupture strength of rolled sheet and welded joints of niobium alloy of the system Nb-W-Mo-Zr at high temperatures

High-temperature strength characteristics of rolled sheet, welded joints, and weld metal of niobium alloy 5VMTs of the system Nb-W-Mo-Zr at 1520–2020 K and stresses comprising 0.4–1.0 of the material ultimate strength are given. It is shown that welded joints and cast weld metal under high-temperature prolonged loading conditions are the same as the basic metal, and in a number of cases they surpass it in high-temperature strength characteristics. Empirical dependences are obtained connecting the short-term material strength with its creep resistance characteristics and stress-rupture strength at temperatures above the start of dynamic recrystallization.Translated from Problemy Prochnosti, No. 12, pp. 24–32, December, 1993.     

高强度钢的Zn—Ti合金新镀层

本文研究了一种Ｚｎ－Ｔｉ合金新镀层，经盐水浸泡、中性盐雾和大气暴露试验结果试验，其耐蚀明显超过镀Ｚｎ层，并与镀Ｃｄ层相近，用缺口持久拉伸试验检验氢脆性，拉伸持续时间超过２００ｈ，达到原航空部部颁标准（ＨＢ５０６７－８５），该镀层适用于高强度钢防护。