Effect of Silicon Content on Thermodynamics of Austenite Decomposition in C-Si-Mn TRIP Steels

Some numerical models such as central atoms model （CAM） and superelement model were used to simulate the thermodynamics of austenite decomposition in the Fe-C-Mn-Si TRIP （transformation induced plasticity） steels. Thermodynamic calculations were carried out under a para-equilibrium （PE） condition. The results show that certain silicon content can accelerate the polygonal ferritic transformation and increase the volume fraction and stability of retained austenite by retarding the precipitation of carbides during the bainitic transformation.     

Iron Oxide Enhanced Chlorine Decay and Disinfection By-Product Formation

This study investigates the interaction of natural organic matter with iron oxide (goethite) on chlorine decay, disinfection by-product (DBP) formation, and DBP compound speciation [total trihalomethanes (TTHM4) and haloacetic acids (HAA5)]. Batch experiments were conducted with goethite, multiple finished drinking waters, variable chlorine dose, and fixed pH 8. The overall objective was to assess natural organic matter (NOM) adsorption onto goethite and its effect on chlorine decay and DBP formation. Chlorine consumption always increased in the presence of goethite and is attributed to an increase in the reactivity and/or modification of adsorbed NOM. Adsorbed NOM also led to an overall increase in TTHM4, however, HAA5 formation was suppressed during the first 2?h. Chloroform was identified as the increasing species and dichloracetic acid was identified as the suppressed species. This study clearly shows that goethite, which is the predominant iron oxide of pipe deposits, alters both chlorine decay and DBP formation and should be considered when assessing water treatment plant operations and DBP monitoring site selection.     

卤素原子在化学气相淀积金刚石薄膜过程中的作用

根据非平衡热力学耦合模型计算得到了碳氢氟和碳氢氯体低压金刚石生长的非平衡定态相图，计算与大量实验事实符合良好。     

Electronic passivation of silicon surfaces by halogens

We report the electronic passivation of a silicon surface by iodine termination. The resulting surface recombination velocity on Si(100) is less than 1 cm/s which is better than that obtained in concentrated hydrofluoric acid (HF). We have produced a surface recombination velocity of 20 cm/s using bromine. We present a simple model for these phenomena of a surface coverage of Si-X where X is a monovalently bonded halogen atom. The effectiveness of the passivation by halogens is shown to be limited by the oxidation of halogens by dissolved oxygen in solution. We demonstrate the use of halogen:methanol solutions as an alternative to HF for the control of silicon surface chemistry.     

Surface X-ray scattering of high index plane of platinum containing kink atoms in solid-liquid interface: Pt(3 1 0) = 3(1 0 0)-(1 1 0)

Surface structure of Pt(3 1 0) = 3(1 0 0)-(1 1 0), which contains kink atoms in the step, has been determined with the use of in situ surface X-ray scattering (SXS) in the double layer region (0.50 V(RHE)) in 0.1 M HClO₄. Clean Pt(3 1 0) surface has pseudo (1 × 1) structure on which lateral displacements of 2-9% and 0.3-1% are found along a and b directions, respectively, whereas the surfaces of Pt(1 1 0) = 2(1 1 1)-(1 1 1) and Pt(3 1 1) = 2(1 0 0)-(1 1 1) are reconstructed to (1 × 2) according to previous reports. Interlayer spacing between the first and the second layers d₁₂ is contracted about 5% compared with the bulk spacing, whereas those between underlying layers are expanded down to fourth layer. Fully adsorbed CO has no effect on the surface structure of Pt(3 1 0). This result differs from that on Pt(1 1 1), where d₁₂ is expanded after CO adsorption.     

Effect of catalysts in the quality of syngas and by-products obtained by co-gasification of coal and wastes. 2: Heavy metals, sulphur and halogen compounds abatement

This paper analyses the formation of sulphur and halogens compounds during co-gasification of low grade coals with different types of wastes that include: pine, petcoke and polyethylene (PE) with the aim of taking profit of waste energy value with the smallest possible impact on the environment. The influence of different types of catalysts or sorbents was studied: calcined dolomite, dolomite enriched with nickel, olivine, nickel and magnesium oxides, zinc oxide and cobalt and molybdenum oxides. The presence of dolomite led to the lowest HCl, HF and H₂S concentrations in the syngas produced. ZnO also gave rise to significant decrease in H₂S concentration, though higher concentrations were obtained than those with dolomite. It was found that when catalysts or sorbents were used, a significant fraction of sulphur, halogens and heavy metals were trapped in the solid residue left behind in the bed and cyclone. Higher temperatures increased the volatility of some metals and sulphur. Leachability assays of solids showed that small quantities of and Cl⁻ could be released and most metals were not leachable, although the use of dolomite slightly increased metals leachability, because of the higher alkaline nature of residual solids produced.     

The Influence of Halide Anions on the Anodic Behavior of Nickel in Borate Solutions

The anodic behavior of nickel in Na₂B₄O₇ solutions containing various concentrations of NaCl, NaBr, or NaI as pitting corrosion agents was studied using the potentiodynamic technique. In absence of the halide anions, the E/i curves exhibit active and passive regions prior to oxygen evolution. The passivity is due to the formation of nickel oxides on the electrode surface. The presence of low concentrations of the halide anions has no effect on the mechanism of nickel passivity. High aggressive anion concentrations stimulate the active region and tend to break down the passive film, leading to pitting corrosion. The susceptibility of the nickel anode to pitting corrosion is enhanced with increasing halide anion concentration and is decreased with increasing pH of solution. The aggressiveness of the halide anions towards the stability of the passive film decreases in the order: Cl^– > Br^– > I^–. The addition of increasing concentrations of tungstate, chromate, or molybdate anions causes a shift of the breakdown potential in the noble direction, indicating the inhibitive action of the added anions. The inhibiting tendency of these anions decreases in the order: WO₄^2– > CrO₄^2– > MoO₄^2–.     

The predicaments and expectations in development of magnetic semiconductors

Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room temperature magnetic semiconductors with strong and controllable s, p-d exchange interaction. With this s, p-d exchange interaction, one can utilize the spin degree of freedom to design applicable spintronics devices with very attractive functions that are not available in conventional semiconductors. Here, we first review the progress in understanding of this particular material and the dilemma to prepare a room temperature magnetic semiconductor. Then we discuss recent experimental progresses to pursue strong s, p-d interaction to realize room temperature magnetic semiconductors, which are achieved by introducing a very high concentration of magnetic atoms by means of low-temperature nonequilibrium growth.     

Improving the hydrogen storage capacity of metal organic framework by chemical functionalization

The hydrogen storage capacity of transition metal decorated terphenyl linkers was investigated using density functional theory based M05-2X, M06 and wB97XD methods. The –OH and –SH groups are used as anchors to bind various transition metals such as Sc, Ti, V, and Cr on terphenyl linker. It has been found that each transition metal can bind four hydrogen molecules through Kubas interaction. The correlation between electron density at the bond critical point corresponding to H–H bond and concomitant intermolecular distances between transition metal and hydrogen molecules has been used to illustrate the Kubas mechanism. Further, to estimate the bulk storage capacity, 42 hydrogen molecules are allowed to interact with the new metal organic framework fragment in all possible binding sites. The calculated interaction energy per hydrogen molecule is found to be −3.38 kcal/mol. Comparison of this value with previous reports shows that this energy is suitable for room temperature hydrogen storage applications.