Solidification Structure of Low Carbon Steel Strips with Different Phosphorus Contents Produced by Strip Casting

In the present paper, low carbon steel strips with different phosphorus contents were produced using a twin roll strip casting process. The solidification structure was studied and its features were analyzed in detail. It was found that the strips possessed a fine microstructure compared with the mould cast steels. With increasing phosphorus content more ferrite has been formed with finer grains.

Carbon Diffusion in Hot Strips of Low Carbon Steel Produced by CSP Line under Different Thermal Histories

Two experiments were carried out on the same compact strip production (CSP) line, which differs in that one of them experienced γ→α→γ thermal history. The differences in microstructure, precipitation, misorientation etc between two experiments were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back-scattered diffraction (EBSD) and positron annihilation technique (PAT). The carbon concentration in matrix is more inhomogeneous in the experiment than that with γ→α→γ7 thermal history. The specific precipitation characteristic in the experiment without γ→α→γ thermal history is discussed on the basis of different carbon diffusion behavior and interaction between dislocation and excess carbon.

Carbon Paste Electrode Modified by Surfactant for Anodic Stripping Voltammetric Determination of Sulphadiazine

he present paper covers the construction and behaviour of a mixed binder car-bon paste electrode modified by surfactant system appropriate for the anodic strip-ping voltammetric quantitation of sulphadiazine. The mixed binder consisted ofglycerol and liquid paraffin. On this electrode in a PH 8. 20 buffer solution sulpha-diazine yields a sensitive anodic stripping voltammetric wave at 0. 82 V. It can beused for the determination of trace amounts of drug, the linear range of the peakcurrent to the sulphadiazine concentration being from 1. 0 x 10-7 to 5. 0 x 10-5mol/L, and the detection limit being 6. 6 x 10-9 mol/L with a relative standard de-viation of 2. 6% (n= 15).The proposed method was used to determine the drug inurine samples.

Thermodynamic Research on Precipitates in Low Carbon Nb-Microalloyed Steels Produced by Compact Strip Production

Microalloying element Nb in low carbon steels produced by compact strip production （CSP） process plays an important role in inhibiting recrystallization, decreasing the transformation temperature and grain refinement.With decreasing the rolling temperature, dislocations can be pinned by carbonitrides and the strength is increased. Based on the two sublattice model, with metal atom sublattice and interstitial atom sublattice,a thermodynamic model for carbonitride was established to calculate the equilibrium between matrix and carbonitride. In the steel produced by CSP, the calculation results showed that the starting temperature of precipitation of Ti and Nb are 1340℃ and 1040℃, respectively. In the range of 890-950℃, Nb rapidly precipitated. And the maximum of the atomic fraction of Nb in carbonitride was about 0.68. The morphologies and energy spectrum of the precipitates showed that （NbTi） （CN） precipitated near the dislocations. The experiment results show that Nb rapidly precipitated when the temperature was lower than 970℃, and the atomic fraction of Nb in carbonitride was about 60%-80%. The calculation results are in agreement with the experiment data. Therefore the thermodynamic model can be a useful assistant tool in the research on the precipitates in the low carbon steels produced by CSP.

Analysis of surface microcracks in low-carbon steel produced via twin-roll strip casting

In this study,morphological and microstructural analyses were conducted on net-shaped microcracks appearing on the surface of low-carbon steel manufactured via twin-roll strip casting. The fractograph and microscale distribution of elements in the cracked region were also analyzed. Results revealed that the cracked surfaces were characterized by slight pits,along with inclusions composed of manganese and silicon oxide distributed along both the sides of the cracks. Fractograph analysis revealed that the crack and smooth dendrite surfaces were oxidized. These phenomena indicate that microcracks on the cast strip surface form at the hightemperature stage of the solidification process during twin-roll casting and rolling. Microcracks were present in each region with pits in the cast strip and extended along the dendrite interface because of the combined effects of phasechange stress,thermal stress,mechanical stress,and fractional crystallization during the solidification process.

Square-Wave Adsorptive Cathodic Stripping Voltammeteric Determination of Manganese (II) Using a Carbon Paste Electrode Modified with Montmorillonite Clay

Manganese is an essential micronutrient for all organisms;however at high concentrations it has a toxic effect. Manganese toxicity is a serious constraint to crop cultivation since it is taken-up by plants and can easily be passed into the food chain again causing symptoms of Parkinson’s disease. A fully validated square-wave adsorptive cathodic stripping voltammetry method has been developed for determination of Mn (II) as a complex with 2-(5’-bromo-2’-pyridylazo) 5-diethylaminophenol in aqueous solutions using a carbon paste electrode (CPE) modified with montmorillonite-Na clay. The results showed that the modified CPE (90% (w/w) graphite powder and 10% (w/w) montmorillonite-Na clay) exhibited excellent electrochemical activity towards the investigated Mn (II) complex in acetate buffer of pH = 5.0. Factors affecting the performance of the modified carbon paste electrode and the sensitivity of the described square- wave stripping voltammetry method, including the electrode composition, concentration of ligand, pulse parameters and preconcentration conditions were examined. A detection limit (S/N = 3) of 0.015μg·L-1 (2.73 × 10-10 mol·L-1) Mn (II) was achieved when a preconcentration time of 240 s was applied. Insignificant interferences from various inorganic and organic species were estimated. The described square-wave adsorptive cathodic stripping voltammetry method coupled with the modified carbon paste electrode has been successfully applied to Mn (II) analysis in different water samples.

Adsorptive Stripping Voltammetric Determination of Mangiferin Using an Activated Chitosan Modified Carbon Paste Electrode

A medium molecular weight powdered chitosan modified carbon paste electrode was used to investigate the electrochemical behaviour by cyclic voltammetry of the pharmacologically-active ingredient mangiferin (MG). An irreversible system was observed, with a peak at ﹢0.55 V (vs Ag/AgCl). The peak current increases about fourfold, at the modified electrode in comparison with that recorded at the chitosan free carbon paste electrode. This allowed the use of adsorptive stripping voltammetry to develop a simple and sensitive electroanalytical method for the determination of MG. The influence of key parameters was investigated, including the electrolysis potential, the preconcentration time, the pH of supporting electrolyte and MG concentration. Upon optimisation of these parameters, the electrode response was found to be directly proportional to the concentration of MG in the range from 2.06 × 10﹣6 M to 6.74 × 10﹣5 M, leading to a detection limit of 1.84 μM for 240 s preconcentration at ﹣0.1 V. A mechanism was also proposed for the electrochemical oxidation of MG.

Anodic Stripping Voltammetric Determination of Nitrite Using Carbon Paste Electrode Modified with Chitosan

A simple method for anodic stripping voltammetric determination of nitrite using carbon paste electrode modified with biomolecular chitosan, is described. In this method, the electrode is activated electrochemically by scanning 5 replicates over the potential range from +500 to +1400 mV immersing in 0.5 M HCl solution. Following this step, the nitrite sample containing 0.1 M KCl is preconcentrated on the activated electrode at +500 mV for 30 s. The deposited anions are then oxidized by different modes of sweep in the oxidation direction. Chemical and electrical parameters affecting the voltammetric measurements are optimized. The peak current is linear proportional to the NO2- concentration within the range 0.41 - 4.1 μg/ml, with detection limit 0.187 μg/m using differential pulse mode. The relative standard deviation is 0.285% for 2.46 μg/ml (five replicates). No interference is observed due to oxygen dissolved in the sample so that nitrogen purging is not needed in this case. The result obtained by the modified electrode is more accurate and selective than the unmodified electrode.

Determination of Lead in Water by Linear Sweep Anodic Stripping Voltammetry (LSASV) at Unmodified Carbon Paste Electrode: Optimization of Operating Parameters

This study presents the elaboration of a simple and cheap electrode made by carbon paste introduced into a cavity of electrode body, and used for the lead traces determination in tap water. A potentiostatic pre-electrolysis at constant voltage enables the reduction of the lead (Pb2+) and the accumulation of the metallic lead at and into the carbon paste;the reoxidation of the Pb (Linear sweep voltammetry) leads to the anodic striping peak. The effect of the main operating parameters on the shape of the peak and the magnitude of the current was examined and their optimal values were determined. Then calibration was achieved and the method was successfully applied (using all the optimized parameters) to the determination of lead in water, with a detection limit of 0.138 μg·L-1. Compared to other methods (ICP-AES for example), the proposed method offers a satisfactory detection limit of the Pb2+ (0.138 μg·L-1) because of the important specific area of the carbon paste electrode, for a significantly lower cost. Besides, there is no observed loss in the electrode answer in terms of peak current, which means that there is no any irreversible steps nor deactivation of the electrode, even after ten successive measurements;only reduction of the lead followed by the deposit oxidation was observed at the electrode.

Determination of Epinephrine Using Poly(Neutral Red)Modified Carbon Fibre Microelectrodes by Anodic Stripping Voltammetry

Poly(neutral red) film modified carbon fibre microelectrodes offer substantial improvement in voltammetric sensitivity and selectivity towards epinephrine (EP). The poly(neutral red) film was electropolymerized by cycling the potential between -0.8 V and +0.8 V. The anodic stripping voltammetric response for EP was found to be dependent on accumulation time and potential. By using a poly(neutral red) film modified carbon fibre microelectrode with a 1 min preconcentration at -1.2 V in biological phosphate buffer solution (pH=7.4), a good linear relationship between the anodic stripping peak currents and EP concentrations was obtained in the range of 2.0×10 -7 ￣ 2.0×10 -5 mol/L. The detection limit was up to 9.0 ×10 -8 mol/L. Moreover, 400 times higher concentrations of vitamin C did not interfere with the measurement of EP. This method was used for determining EP concentrations in epinephrine hydrochloride injection solution with satisfactory results.

不同数量碳纤维布条带约束煤样的轴压蠕变特性细观模拟研究

为探究不同数量碳纤维增强复合材料(carbon fiber reinforced polymer,CFRP)条带对轴压煤样蠕变力学特性的影响,耦合PFC3D软件与FLAC3D软件,结合伯格斯(Burger’s)模型与平行黏结(Linearpbond)模型,建立混合接触的细观数值模型。根据未约束煤与6条带CFRP约束煤样单轴压缩蠕变室内试验,验证了数值模型的可靠性。研究了2~7条带CFRP约束煤样在单轴压缩蠕变下的力学特性及能量演化。研究表明:随着条带数的增加,煤样在初始阶段的轴向应变整体呈现增大趋势,加速蠕变阶段轴向应变明显增大;混合接触模型内部接触的最大力整体呈现增大趋势;伯格斯模型接触数量与平行黏结模型接触数量的比值约为1∶9时,数值模拟模型能够反映出煤样蠕变的力学特性;增加CFRP条带数,煤样的径向变形受到限制,产生的剪切微裂纹增多,煤样内部的剪切破坏更加严重,煤样的破坏形态由张拉破坏逐渐向剪切破坏转变;随着碳纤维布条带数量的增加,煤样的总能量、弹性能、耗散能均增加,在煤样发生蠕变失稳前,弹性能的变化与总能量的变化较为相似。

Preparation of active carbons from corn stalk for butanol vapor adsorption

Active carbons(ACs) were prepared through chemical activation of biochar from whole corn stalk(WCS)and corn stalk pith(CSP) at varying temperatures using potassium hydroxide as the activating agent. ACs were characterized via pore structural analysis and scanning electron microscopy(SEM). These adsorbents were then assessed for their adsorption capacity for butanol vapor. It was found that WCS activated at900 °C for 1 h(WCS-900) had optimal butanol adsorption characteristics. The BET surface area and total pore volume of the WCS-900 were 2330 m2/g and 1.29 cm3/g, respectively. The dynamic adsorption capacity of butanol vapor was 410.0 mg/g, a 185.1% increase compared to charcoal-based commercial AC(143.8 mg/g).

Grain refinement of low carbon steel produced by CSP process

In comparison with conventional production for hot strips, compact strip production (CSP) brings about some new micro-structural phenomena. Investigations were carried out to clarify the grain refinement mechanism of low carbon steel strips produced by the EAF-CSP process. Samples, obtained from the same rolling stock during continuous rolling, were examined through SEM, TEM and XEDS. Thin slabs have a dominant columnar structure and the spacing of the secondary dendrite arms ranges from 90 to -125 μm. The average grain sizes for the central area of the samples from the 1st to 6th pass are 41.6, 25.2, 21.4, 20.2, 13.1, 6.7 μm, respectively. Large number of nanometer oxide and sulfide have been found in the low carbon steel produced by the CSP process. The grain refinement mechanism can be summarized as follows: finer solidification structure of the thin slab; austenite recrystalliza-tion at higher temperature and stain accumulation at lower temperature caused by the great reduction of single rolling pass during continuous rolling; nano-scaled precipitates of sulfide and oxide which drag grain boundaries of austenite or ferrite to prevent the grain coarsening.

Aspects of microstructure in low carbon steels produced by the CSP process

The solidification structure, microstructure evolution during rolling andprecipitates with nanometers in dimension of the low carbon steels produced by CSP process with thinslabs have been studied in recent years. Important differences in microstructure and mechanicalproperties between the CSP products and the conventional one were observed. These differences mayarise from the much rapider solidification rate and cooling rate after casting of the thin slabs.Some aspects of the microstructure for the low carbon steels of the CSP thin slabs are summarizedand compared with the conventional one.

EUROSTRIP~不锈钢和带钢连铸技术

EU ROSTRIP○R技术在带钢连铸生产领域稳居领先地位。介绍了 EU ROSTRIP○R联合开发计划及相关欧洲网络。以所达到的产品质量结果为重点 ,描述了碳钢和不锈钢中间试验厂和预工业试验厂以及研究开发工作的经验。

Mixed Binder Carbon Paste Electrode for Quantitation of Isoniazid in Serum

This paper covers the construction and behaviour of a mixed binder carbon paste electrode system appropriate for the cathodic stripping voltammetric quantitation of iso-niazid. The mixed binder consisted of glycerol and liquid paraffin. At the mixed binder carbon paste electrodes in a pH 3.0 buffer solution, isoniazid showed two sensitive cathodic stripping voltammetric wave at-0. 75 V (p1) and-0. 88 V (p2) , respectively. The p2 can be used for the determination of trace amounts of isoniazid, the linear range of the peak current to the isoniazid concentration being from 5. 0×10-7 to 5.0×10-5 mol/L, and the limit of detection being 1. 0×10-7 mol/L with a relative standard deviation of 6. 0%(n=10). The proposed method was directly used to determine the drug in blood serum without the pretreatment of blood serum.

Voltammetric Detection of Nanomolar Levels of Hypoxanthine in the Presence of Copper(Ⅱ) at Glassy Carbon Electrode

Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper(Ⅱ) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine Cu + is shown to be adsorbed on the electrode surface in the presence of an excess of copper(Ⅱ). After accumulation period, hypoxanthine Cu + was stripped from the electrode surface and the anodic current coming near to the oxidation of Cu(Ⅰ) to Cu(Ⅱ) was measured. A linear calibration curve in the range of 5 nmol/L 1.5 mmol/L hypoxanthine, with a detection limit of 0.5 nmol/L hypoxanthine were obtained.

Multiwall Carbon Nanotube Modified Electrochemical Sensor for Reactive Black 5

Cyclic voltammograms of reactive black5 (RB5) at different pHs in the range 1.0 - 13.0 on multiwall carbon nanotube modified glassy carbon electrode revealed the presence of one well-defined irreversible anodic peak around 975 mV in acidic and neutral pHs. Adsorption controlled oxidation observed at acidic pH 1.0 resulted in the maximum peak current response in cyclic voltammograms. A systematic differential pulse stripping voltammetric studies were carried out using the modified electrode at pH 1.0. The accumulation parameters, accumulation potential and time were optimized for maximum adsorption of the dye which was ascertained from the SEM photographs and XRD results. The stripping parameters were optimized and calibration was made under optimum conditions. The range of study was from 0.5 ppm to 100 ppm and the lower limit of determination was 100 ppm. Five identical experiments were carried out and the RSD value obtained was 2.5% suggesting good reproducibility. The proposed method was successfully applied to determine the concentration of dye in the fabric and wastewater after dyeing.

The Electrochemical Behavior and the Determination of Bavistin on Glassy Carbon Electrode

In this paper, the electrochendcal behavior of bavistin (MBC) on glassy carbon electrode is reported. In a base solution of pH=9.0 NH3-NH4Cl, a sensitive anodic peak was found by cyclic voltammetry. Differential pulse stripping voltanunetry was applied for determing MBC in grains. The detection limit is 4×10-8mo/L.The recovery is from 91.3% to 95.7%. The method has advantages of simplicity and high sensitivity.