Strengthening mechanisms of a new 700 MPa hot rolled Ti-microalloyed steel produced by compact strip production

A new hot rolled titanium-microalloyed steel with yield strength of 700 MPa has been developed by CSP (compact strip production) process based on commercial weather resistant steel. EBSD results showed that the average size of its grains with high angle boundaries (>15°) was 3.3 μm. High-density dislocations and large number of nanometer particles were observed in the steel product by TEM. X-ray analysis on the electrolytically extracted phase from the steel indicated that fraction of MX phase was 0.0793 wt%, in which the particles smaller than 10 nm accounted for 33.7%. The contribution of precipitation hardening resulting from nanometer particles was calculated as approximate 158 MPa. The commercial weather resistant steel, reference steel for comparison with 450 MPa yield strength, was also prepared and investigated. It can be concluded that grain refinement is still a major strengthening mechanism in this high strength steel, but precipitation hardening of nanometer TiC precipitates is the dominant factor to increasing the yield strength in new developed steel compared with the reference steel.     

Supercritical Antisolvent Particle Precipitation: In Situ Optical Investigations

The manner in which the presence of a solute can affect the mixing behavior of a solute, solvent and antisolvent in a supercritical antisolvent (SAS) micronization process is demonstrated. The mixing behavior was analyzed by applying a two‐dimensional (2D) Raman scattering technique. Mole fraction and partial density distributions were measured for the CO₂ antisolvent. The results originating from the optical investigations were correlated with the particle results. The experiments cover the variation of the solute concentration at fixed operating conditions of 10 MPa and 40 °C.     

Preparation of layered nickel aluminium double hydroxide from waste solution of nickel

The separation of nickel has been carried out from a waste solution containing 3.18 g/L Ni with other impurities such as Fe, Zn, Cu and As. Iron was removed by precipitation and Cu and Zn were removed by solvent extraction using LIX 622N and NaTOPS-99, respectively. After removal of all these impurities nickel was extracted by 1.5 M NaTOPS-99 in two counter-current stages at A:O ratio of 3:1 and the loaded organic was stripped with 30 g/L H₂SO₄ at phase ratio of unity. The strip solution of nickel was treated with Al₂(NO)₃ · 9H₂O for co-precipitation by increasing the pH of solution with 1 M NaOH up to 10. The Ni–Al layered double hydroxide was confirmed through XRD characterization.     

MULTIPLICITY AND STABILITY ANALYSIS OF AGGLOMERATION CONTROLLED PRECIPITATION

The possibility of multiplicity in continuous isothermal MSMPR precipitators has been explored for agglomeration controlled conditions and general criteria, independent of nucleation kinetics, are developed for stability and multiplicity of the steady states. For the Volmer model of primary nucleation and the magma dependent power law model of secondary nucleation, parameter regions are determined in which multiple steady states exist, and their linear stability is analyzed. The analysis holds in general for all types of agglomeration kernel. For the Volmer nucleation kinetics three steady states exist in the region of multiplicity with the “middle” one always being unstable. The analysis for magma dependent power law model showed multiplicity regions having as many as four steady states, the number depending on magma and kinetic order. Unlike the case of molecular growth control, limit cycle behaviour is not possible, and the approach to the steady state is always asymptotic     

Magnetic properties of Ni(II)–Mn(III) LDHs

The synthesis of Ni_1−xMn_x(OH)₂(CO₃)_x/2·nH₂O Layered Double Hydroxides (LDHs) for x = 0.2, 0.25 and 0.33, their characterisation by electron microscopy, X-ray diffraction and their magnetic properties are reported in this study. When x increases, the crystallinity of the nanoparticles is improved. The low temperature magnetic behaviour of these compounds is characteristic of the competition between in plane ferromagnetic and interlayer antiferromagnetic interactions. The ferromagnetism is due to in plane Ni cations interaction and decreases when manganese content increases (Tc decreases from 26 to 15 K when x increases from 0.2 to 0.33). It was found that the substitution of Ni by Mn ions favours the in plane antiferromagnetic order. This study demonstrates that magnetic interactions occur in LDH with non magnetic interlayer anions.     

Alcohol Precipitation of Xanthan Gum from Pure Solutions and Fermentation Broths

Abstract

Xanthan gum was precipitated from pure solutions and fermentation broths using either ethanol, isopropanol, or tert-butanol. The compositions of the precipitate and supernatant phases were determined as a function of alcohol concentration and used to construct binodal solubility curves with tie lines. Xanthan did not precipitate at bulk-mixture alcohol concentrations below 37.5% (wt) for ethanol, 35% for isopropanol, and 31% for tert-butanol. As the alcohol concentration increased beyond this point, the precipitates first were heavy gels with low xanthan concentrations. At higher alcohol concentrations, the precipitates were compact and fibrous. The maximum xanthan concentration in the precipitate was 14.5% at 60% ethanol, 23.5% at 50% isopropanol, and 33.5% at 40% tert-butanol in the pure solution precipitation experiments. At alcohol concentrations beyond 75%, the precipitates were brittle and needle-like, which made separation from the supernatant difficult. The results for the fermentation broth experiments were very similar to those of the pure solution experiments. Thus, precipitation using ethanol required the highest alcohol usage and resulted in the lowest xanthan concentration in the precipitate. Conversely, tert-butanol required the least alcohol for precipitation and formed the precipitates highest in xanthan concentration.     

用季铵型阳离子试剂PQ-100从含铀钼的硫酸溶液中沉淀钼

本文叙述了在含铀钼的硫酸溶液中,钼和PQ-100季铵型阳离子生成络合沉淀物的某些规律,提出了钼的主要沉淀条件。在钼的络合沉淀过程中,铀基本上不沉淀,沉淀物中α总放射性强度低于放射性标准。     

Effects of alteration on shear characteristics of compacted Ca-bentonite immersed in alkaline solutions

This study evaluated the shear characteristics of compacted Ca-bentonite immersed in 0.1 mol/L of NaOH, KOH, and KOH–NaOH and 0.005 mol/L of Ca(OH)₂ at 40℃ over a maximum period of 1710 days. Triaxial compression tests were performed on the immersed specimens, and the mineral composition, mean layer charge, leachable cations, and microstructure were investigated. The dissolution of cristobalite was significant at high pH levels, whereas phillipsite was precipitated in the specimens immersed in the NaOH and NaOH–KOH solutions. The amount of leachable cations increased substantially, indicating that soluble secondary products (non-crystalline phase) were present in the specimens, as was proven by the observation of gel-like products comprised of Ca and Si on the microphotograph. An increase and decrease in the maximum deviator stress occurred as a result of the dissolution and precipitation. A structural parameter was proposed in this study by assuming the contribution of the secondary products to the cementation of the soil skeleton. This provided a series state transition of the compacted bentonite, where the maximum deviator stress increased with the cementation of the non-crystalline secondary phase. However, the progressing dissolution of the primary minerals decreased the dry density, thereby loosening the cemented structure and reducing the maximum deviator stress.     

影响纳米羟基磷灰石溶胶在水介质中分散性能的因素

目的：探讨影响纳米羟基磷灰石溶胶分散性能的因素。方法：以水分散体系下，采用化学共沉淀法制备的纳米HAP，研究了反应介质pH值、稳定剂或表面改性剂等因素对纳米粒子粒径及分散稳定性的影响。结果：调节介质的pH值，使颗粒间处于较高的静电效应，在此条件下加入表面活性剂，使颗粒间又具有空间位阻稳定效应，空间位阻稳定效应可阻止颗粒间的团聚。结论：通过优化实验条件可制得高度均匀分数状态纳米羟基磷灰石溶胶。     

An integrated radiotracer approach for the laboratory evaluation of scale inhibitors performance in geological environments

The applicability of a newly developed radiotracer technique as a reliable laboratory procedure for the evaluation of scale inhibitors performance to prevent mineral precipitation is demonstrated. The performance of two new environmentally friendly inhibitors to prevent calcite and barite scale was evaluated experimentally in connection with a standard phosphonate-type scale inhibitor using the radioactive tracer technology. The radiotracers ⁴⁷Ca and ¹³¹Ba were employed in order to monitor at real-time calcite and barite scale formation, respectively. The results show that the developed radiotracer technique can be established as a novel method for the determination of the minimum inhibitor concentration (MIC) under dynamic, reservoir conditions. In addition, the radioactive tritiated water (HTO) was used as a reference water tracer to identify the inhibitors’ properties, such as adsorption/desorption characteristics, in sandpack-flooding tests. Further issues regarding the implementation of the radiotracer technology for the laboratory evaluation of scale inhibitors performance are also discussed.