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.

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.

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.

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.

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.

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.

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.

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.

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.

Adsorptive Stripping Voltammetry of Ultra Trace Lanthanum（Ⅲ） Using an Alizarin S as Complexing Agent and Carbon Paste as Working Electrode

Ultra trace determination of lantanum（Ⅲ） has been studied by adsorptive stripping voltammetry methods using an alizarin S as complexing agent and carbon paste electrode as working electrode. The electrode was made from mixed of carbon powder and paraffin in micropipette tip with diameter of 4 ram. This method consists of two steps. The first step is the formation and adsorptive accumulation of metal ion with chelator at the electrode surface. The second step is stripping the complex from the electrode surface into the solution. The stripping step generates current which is recorded as voltammogram. The optimum conditions of instrumental parameter obtained were accumulation potential of 600 mV, accumulation time of 120 seconds, and pH of solution of 5.5. In this research, the limit detection obtained was 2.3348 × 10^-12 M （3.24× 10^-11μg/L） with sensitivity of 16.52 （nA/10u M） and the precision of standard solution of La3＋ with concentration of 2 × 10^-12 M, 4× 10^-12 M, 6 × 10^-12 M, 8 × 10^-12 M, and 10 × 10^-12M were 3.50%, 9.88%, 7.19%, 7.48% and 1.85% respectively. The linierity of this method is very good with correlation coefficient is 0.9780. Recovery percentage from La3＋ with concentration of 6× 10^-12 M and 10 × 10^-12 M are 108.84% and 91.51%, respectively.

Adsorptive Stripping Voltammetric Study of the Enhancement of Copper(Ⅱ) in Phosphate and Carbonate media and in the Presence of Silicate

Adsorptive enhancements of several inorganic salts on copper(II) were studied by adsorptive stripping voltammetry with a hanging mercury drop electrode Increase in peak curren of cu(II) were observed in alkaline phosphate or media owing to adsorption Silicate can also enhance the peak current of Cu(II). The enhancing power phosphate,carbonate, and silicate is 33, 26, and 8.9 times, respectively.

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.

环境湿度对浸金属碳滑板磨损及温升的影响

为探究环境湿度对弓网摩擦副载流滑动过程中电弧放电能量、浸金属碳滑板温升及滑板磨损量的影响,采用环-块式高速载流摩擦磨损试验台,对比不同湿度条件下,电弧能量、滑板温升及滑板磨损量随滑动速度、电流强度、法向力的变化情况。试验结果表明:不同环境湿度下,滑动速度和电流强度的增大均会导致电弧能量及滑板温升急剧增大;电弧热是导致温升的主要热源;增大法向力对于抑制电弧放电、降低滑板温升均有显著效果,而对于滑板磨损量变化的影响,不同湿度情况则截然相反;高湿度环境下接触副附着的水膜改善了接触状况和散热情况,电弧能量及滑板温升都小于低湿度环境;低湿度环境下滑板表面受到更严重的机械摩擦,其表面状态相比高湿度更差;在平均湿度较高的夏季适当增加升弓压力,在平均湿度较低的冬季适当降低列车行驶速度可以减少浸金属碳滑板磨损。

带状采伐初期对华西雨屏区杉木人工林土壤碳组分及稳定性的影响

【目的】旨在相同采伐强度下确定不同带宽采伐带和保留带对土壤碳组分及其稳定性的影响。【方法】在华西雨屏区洪雅林场人工林生态系统研究长期科研基地内,以集水区为功能单元,对23 a生的杉木人工林进行40%相同强度不同带宽的3种带状采伐处理,分别是S1(10 m采伐+15 m保留)、S2(20 m采伐+30 m保留)和S3(30 m采伐+45 m保留),在采伐1 a后进行土壤样品采集。【结果】(1)与未采伐杉木纯林相比,采伐带0~20 cm土层土壤有机碳含量均显著降低;(2)夏季0~40 cm土层的S2采伐带有机碳稳定性显著高于其他两个带宽,而S2保留带显著低于其他两个带宽;冬季表现为S1显著高于其他2个带宽;(3)冗余分析表明,微生物生物量碳与土壤有机碳各组分具有明显的协同作用;(4)土壤碳稳定性与可溶性有机碳含量呈显著正相关,与活性有机碳组分呈显著负相关。【结论】在40%采伐强度下,适宜选择S1带状采伐组合更有利于保持土壤有机碳含量和稳定性。研究结果为杉木人工林的近自然改造和指导林业碳汇经营提供了理论依据。

基于碳系材料的标准应变传感条应用研究

针对传统电阻应变测量过程中,电阻应变片只能适应局部应变的点测,不能进行全域性测量且粘贴工艺复杂的特点,本文提出了采用价格低廉的碳系材料,利用改进凹版印刷技术制备标准长度传感条,采用裁剪及拼接的方法,实现传感条测试区域的任意调整,介绍了基于电阻变化率的传感条应变测试基本原理,通过等截面悬臂梁静载实验考核了标准传感条的各项性能指标,并通过钢筋混凝土弯曲梁实验评价了标准应变传感条针对混凝土梁小应变时全域性的测量效果,实验结果表明:该标准应变传感条具有制备方法简单、组合方式多样、小应变响应跟随性好、适用于户外现场测量的特点,可推广应用于混凝土结构的健康监测领域。

N235从高碳石煤脱碳渣酸浸液中萃取钒的工艺研究

以某地高碳石煤脱碳渣经空白焙烧-酸浸后的浸出液为原料,采用萃取剂N235和反萃剂Na_(2)CO_(3)对钒萃取工艺和反萃取工艺进行了研究。结果表明,最佳萃取工艺参数为:萃原液pH值2.3、有机相组成为15%N235+5%仲辛醇+80%磺化煤油、相比(O/A)1∶4、萃取时间4 min、氧化剂氯酸钠用量为萃原液V_(2)O_(5)质量的0.05倍、萃取级数五级,钒萃取率达99%;最佳反萃工艺参数为:反萃剂Na_(2)CO_(3)溶液浓度8%、反萃相比(O/A)4∶1、反萃时间10 min、反萃级数三级,钒反萃取率可达99.50%。在最佳萃取和反萃取工艺条件下,钒浓度由4.25 g/L富集到68.50 g/L,且pH值为8.5,无需中和处理。对富钒液进一步沉钒、煅烧得到的最终产品V_(2)O_(5)品位为98.95%,且杂质含量低,满足行业标准YB/T 5304—2017中98级V_(2)O_(5)的要求。

不同表面形貌的接触线对浸金属碳滑板载流摩擦磨损性能的影响

在受电弓-接触网载流摩擦磨损过程中,接触线会产生不同的横截面形状,而接触线形貌的改变可能会影响弓网间的接触关系,进而影响弓网间的载流摩擦磨损性能。为研究不同表面形貌的接触线对浸金属碳滑板载流摩擦磨损性能的影响,利用环-块式高速载流摩擦磨损试验机,研究载流条件下常规形貌、麻点形貌、斜切形貌的接触线与浸金属碳滑板的摩擦磨损性能,比较采用不同形貌接触线时的摩擦因数、电弧能量和浸金属碳滑板的磨损量、表面形貌。试验结果表明:在直流电情况下,常规接触线与浸金属碳滑板组成的摩擦副的摩擦因数最小,滑板磨损量最低;采用斜切形貌接触线时的摩擦因数最大,滑板磨损量最大。通过SEM电镜观测浸金属碳滑板表面的磨损形貌,发现接触线为常规形貌时,滑板以氧化磨损为主,有较多的氧化物产生;接触线为麻点形貌时,滑板以电弧烧蚀和磨粒磨损为主,产生了细小裂纹和烧蚀坑,有较多的磨屑和剥落层出现;接触线为斜切形貌时,滑板以电弧烧蚀为主,有大裂纹和犁沟产生,并且烧蚀区域出现了较多的白色小球。研究表明,当接触线的形貌发生改变时,会导致滑板磨耗增加并加剧接触副电弧放电,从而恶化接触副的状态。因此,当接触线磨损变形严重时,应及时进行更换。

天津地铁6号线弓网异常磨耗问题研究

地铁运行期间刚性接触网线路往往会产生弓网异常磨耗现象,这给地铁列车的正常运行带来巨大安全隐患。文章针对天津地铁6号线存在的弓网异常磨耗现象,首先对其刚性接触网线路中弓网关系进行研究,提出弓网异常磨耗状态在检修、应用与研究过程中的评价标准;然后以此标准为重点,跟踪分析2021年—2022年冬季期间天津地铁6号线弓网异常磨耗状态随环境湿度的变化情况,分析影响弓网异常磨耗状态的关键因素。研究结果表明:冬季隧道内湿度为引发弓网异常磨耗问题的主要原因,控制隧道湿度在35%~65%区间内,同时优化弓网跟随性、行车模式并定期开展碳滑板、网线维护作业,有利于缓解冬季弓网异常磨耗问题。该研究工作可为解决地铁刚性接触网条件下的弓网异常磨耗问题提供理论参考。

中国旅游业碳排放时空特征及影响因素分解

综合运用碳排放系数估算法与旅游剥离系数法,估算2011-2021年中国省级旅游交通、旅游住宿、旅游餐饮零售邮电业与旅游活动的碳排放量,并运用对数平均迪式指数(LMDI)分解模型解析旅游碳排放影响因素。结果表明:旅游业碳排放总体呈下降趋势,空间分布上呈现东南多、西北少的特征;旅游交通碳排放与旅游活动碳排放是旅游碳排放主要来源;旅游消费水平与游客规模是旅游碳排放产生的主要因素;旅游能源结构与旅游能源强度对旅游碳排放起抑制作用。

不同覆盖措施对旱区春小麦产量及碳效率的影响

为实现旱区春小麦种植生产环境效益和经济效益双赢,依托大田试验,研究不同覆盖措施秸秆带状覆盖、地膜覆盖、秸秆碎秆覆盖和对照露地平作对旱区春小麦产量及碳效率的影响,并对经济效益进行了评价。结果表明,与露地平作相比,地膜覆盖显著提高了生育期春小麦干物质积累量,增幅为37.58%;秸秆带状覆盖提高了小麦开花期和收获期干物质积累量,增幅分别为32.65%和9.83%。秸秆碎秆覆盖、地膜覆盖千粒重较露地平作分别提高了15.55%、21.91%。地膜覆盖碳投入总量增幅最大,较露地平作增加1223.07 kg C/hm^(2)。秸秆碎秆覆盖较露地平作籽粒碳和植株碳产出量分别提高了38.41%和23.34%。秸秆带状覆盖提高了碳生产效率、碳经济效率、碳生态效率,增幅分别为0.58%、0.45%、0.24%。秸秆碎秆覆盖经济效益为3882.69元,较露地平作增加22.7%。综合表明,各覆盖措施均能提高春小麦产量和经济效益,其中秸秆带状覆盖显著提高了碳生产效率、碳经济效率和碳生态效率。