Band 36, Heft 9 -

The temperature dependences of the spontaneous polarization and the dielectric constant (susceptibility) are calculated using the mean field model for the ferroelectric N(CH 3 ) 4 HSO 4 . Expressions derived from the mean field model for the spontaneous polarization and the inverse susceptibility are fitted to the experimental data from the literature. The fitting parameters in the expansion of the free energy in terms of the spontaneous polarization are determined within the temperature intervals in the ferroelectric and paraelectric phases of N(CH 3 ) 4 HSO 4 . Our results show that the temperature dependences of the spontaneous polarization and the dielectric constant as predicted from our mean field model, describe adequately the observed behavior of N(CH 3 ) 4 HSO 4 in the ferroelectric and paraelectric phases.

The structural properties of molten CaO–SiO 2 –P 2 O 5 –FeO slag system with varying slag basicity have been investigated by molecular dynamic (MD) simulations using the pairwise potential model. The result shows that more than 95 % Si and 98 % P are four coordinated and form tetrahedral structures. Non-bridging oxygen occupies a predominant position in the system. With basicity increasing from 0.6 to 1.5, the proportion of non-bridging oxygen increases from 66.3 % to 77.3 %, whilst the bridging oxygen decreases from 30.1 % to 10.2 %. Both the result of MD simulations and Raman spectroscopic analysis show the proportion of Q 0 increases with increasing slag basicity, whilst Q 2 and Q 3 decrease. The degree of polymerization of CaO–SiO 2 –P 2 O 5 –FeO system decreases with increasing slag basicity.

This paper focused on optimizing the process conditions of direct acid leaching process to enhance the leaching efficiency of leaching vanadium from the stone coal. Orthogonal experiments and single factor experiments were conducted to investigate the effect of the influential factors of direct acid leaching on vanadium leaching ratio. The results showed that the vanadium leaching ratio reached the maximum value of 89.22 % under the optimal process conditions of CaF 2 dosage 5 mass%, H 2 SO 4 dosage 40 mass%, leaching temperature 95 °C and leaching time 10 h. Furthermore, the reaction mechanisms of the main influencing factors were analyzed. Finally, the two-stage counter-current leaching process was adopted to decrease the consumption of sulfuric acid and neutralizer, and the results indicated that the consumption of sulfuric acid decreased 12.50 % as well as neutralizer decreased 35.80 %.

In this study, a Cu/Al composite ingot was prepared by casting aluminum method, and the effects of the Cu concentration distribution in the transition layer on the solidification microstructure were examined during the recombination process of solid Cu and liquid Al. The results show that the Cu content is about 60 % at the Cu/Al binding interface in the transition layer, while the Cu concentration first drops sharply and then decreases slowly in the direction away from the pure Cu. The concentration gradient of Cu reaches 1 %/μm close to the Cu/Al binding surface. The Cu distribution in the transition layer does not change the microstructure species, but changes the proportions of various microstructures. The smaller the Cu concentration gradient is, the less the proportion of the hypoeutectic microstructure in transition layer is.

High voltage electric discharge (HVED) in disperse system “hydrocarbon liquid – powder” due to impact of plasma discharge channel, electromagnetic fields, shock waves mechanical impact, hydro flows and volume microcavitation leads to synthesis of nanocarbon, metal powders dispersion and synthesis of micro- (from 10 −6 to 10 −7 m) and nanosized (from 10 −7 to 10 −9 m) composite powders of hardening phases. Spark plasma sintering (SPS) of powder mixtures allows targeted control of grain growth rate and thus allows obtainment of multifunctional composite materials dispersion hardened by nanoparticles. Processes of HVED synthesis of micro- and nanosized powders of new compositions from elemental metal powders and their mixtures with the subsequent application of high-speed SPS of obtained powders create conditions for increase of strength (by 10–20 %), hardness and wear-resistance (by 30–60 %) of obtained materials.

The diffusion and fracture behaviors of Mg/Al joints are investigated in this paper. The concentration distribution equations at each phase are calculated using Matlab, the predominant processing parameters that control the diffusion behaviors are discussed. The result indicates that the intermetallic compounds (IMCs) at the bonded interface of Mg/Al joint consist of Al 3 Mg 2 layer (β) and Al 12 Mg 17 layer (γ). Based on the Fick’s second law, the error function equations calculated by Matlab is in well accordance with the experiment of diffusion in Mg/Al diffusion bonding process. In addition, elements distribution and thickness of IMCs at the joint interface can be simulated by the error function equations. The microstructures of shear fracture surface show that cleavage steps occur at both fractures.

Twin-roll strip casters for near-net-shape manufacture of steels have received increased attention in the steel industry. Although negative segregation of phosphorus occurred in twin-roll strip casting (TRSC) steels in our prior work, its mechanism is still unclear. In this work, V-shaped molds were designed and used to simulate a meta-rapid solidification process without roll separating force during twin roll casting of carbon steels. Experimental results show that no obvious phosphorus segregation exist in the V-shaped mold casting (VMC) steels. By comparing TRSC and the VMC, it is proposed that the negative phosphorus segregation during TRSC results from phosphorus redistribution driven by recirculating and vortex flow in the molten pool. Meanwhile, solute atoms near the advancing interface are overtaken and incorporated into the solid because of the high solidification speed. The high rolling force could promote the negative segregation of alloying elements in TRSC.

A series of uniaxial tensile tests were carried out at different strain rate and different temperatures to investigate the effects of temperature and strain rate on tensile deformation behavior of P92 steel. In the temperature range of 30–700 °C, the variations of flow stress, average work-hardening rate, tensile strength and ductility with temperature all show three temperature regimes. At intermediate temperature, the material exhibited the serrated flow behavior, the peak in flow stress, the maximum in average work-hardening rate, and the abnormal variations in tensile strength and ductility indicates the occurrence of DSA, whereas the sharp decrease in flow stress, average work-hardening rate as well as strength values, and the remarkable increase in ductility values with increasing temperature from 450 to 700 °C imply that dynamic recovery plays a dominant role in this regime. Additionally, for the temperature ranging from 550 to 650 °C, a significant decrease in flow stress values is observed with decreasing in strain rate. This phenomenon suggests the strain rate has a strong influence on flow stress. Based on the experimental results above, an Arrhenius-type constitutive equation is proposed to predict the flow stress.

Hexagonal Zn 1–x Cd x O microtubes with CdO contents (x = 0, 1, 3 and 5 %) have been successfully synthesized via direct microwave irradiation. Field emission scanning electron microscopy (FE-SEM), UV–vis spectroscopy, photoluminescence (PL), and energy-dispersive spectrometer (EDS) were employed to characterize the Zn 1–x Cd x O microtubes. Zn 1–x Cd x O microtubes have an average diameter of 140 µm, wall thickness of 2~4 µm and length of about 250 µm. UV–vis studies showed that the optical band gap of ZnO microtube (3.27 eV) was reduced to 3.20 eV for Zn 0.97 Cd 0.03 O microtube. The PL spectra showed a strong emission peak in the visible region centered at 562.88 nm with a weak UV emission has been detected for Zn 0.97 Cd 0.03 O microtube. EDS confirms the presence of Zn and O in ZnO microtube and the absence of Cd as a doping material for CdO-doped ZnO microtubes due to the small amounts of CdO concentration.

The spallation behavior of oxide scale on the surface of low carbon microalloyed steel (510L) is investigated during the laminar cooling of hot rolling strip. Surface, cross-section morphology and phase composition of oxide scale in different laminar cooling rate are observed by scanning electron microscopy (SEM) and X-Ray Diffraction (XRD). Moreover, a spallation mathematic model is established based on empirical formula to predict the critical thickness of oxide scale and the test of high temperature oxidation kinetics at different temperatures between 500 °C to 900 °C provides oxidation rate constant for the model calculation. The results of heat-treatment test and model calculation reveal that laminar cooling rate plays an important role in controlling the thickness of oxide scale and suppressing spallation behavior.

Application of low-nickel laterite ore containing chromium as charging material for ironmaking can reduce raw material costs, but result in an increase of chromium content in the hot metal and hence, Cr 2 O 3 content in the steelmaking slag, which subsequently causes many problems related to lime dissolution for the steelmaking operation. In this work, a rotating cylinder method was employed to study the effect of Cr 2 O 3 on lime dissolution in steelmaking slag. The lime dissolution mechanism, rate control step and affecting factors, including slag basicity, FeO x and B 2 O 3 content, and the formation of phases at reacted layer, were discussed. It was found that mass transfer was the rate control step in slag phase, increase of Cr 2 O 3 and slag basicity delayed lime dissolution due to the formation of high-melting temperature phases of FeO · Cr 2 O 3 spinel and 2CaO · SiO 2 at the slag/lime reacted interface. Addition of B 2 O 3 promoted lime dissolution and suppressed formation of FeO · Cr 2 O 3 spinel.