Interaction of highly dissociated low pressure hydrogen plasma with W-C thin film deposits

Thin film deposits of carbon and tungsten on stainless steel substrate were prepared by RF sputtering of a tungsten target in acetylene atmosphere. At the target bias of − 1700 V and the target current of 30 mA cm^− 2, a rather uniform film containing 50 at.% of C and 50 at.% of W was deposited. The thickness of the deposited film was about 1 μm. Samples were exposed to highly dissociated hydrogen plasma created by a microwave discharge at the power of 1000 W. Some samples were heated additionally by concentrated solar radiation. After plasma treatment, the samples were characterized by X-Ray Diffraction and Auger Electron Spectroscopy. The results showed that aggressive hydrogen plasma allows for the removal of carbon from the deposits at moderated temperatures. Prolonged treatment showed formation of highly crystalline pure tungsten, and finally the tungsten film interacted with the substrate forming a thin film rich of Fe₇W₆ compound. The range of temperature and/or treatment time for the removal of carbon from the W-C film was found very narrow.     

Bridge Pier Scour in Clay-Sand Mixed Sediments at Near-Threshold Velocity for Sand

Local scour at circular bridge piers embedded in a clay-sand-mixed bed was investigated in laboratory flume experiments. The effects of clay content, water content, and sand size on maximum equilibrium scour depth, equilibrium scour hole geometry, scouring process, and time variation of scour were studied at velocities close to the threshold velocities for the sand in the clay-sand mixture. It was observed that clay content and water content were the key parameters that effect the scouring process, scour hole geometry, and maximum equilibrium scour depth. The bridge pier scouring process in clay-sand mixtures involved different dominating modes for removal of sediment from scour hole: chunks-of-aggregates, aggregate-by-aggregate, and particle-by-particle. Regression-based equations for estimation of nondimensional maximum scour depth and scour hole diameter for piers embedded in clay-sand mixtures having clay content of <40% and water content of <40% were proposed as functions of pier Froude number, clay content, water content, and bed shear strength.     

伊宁凹陷构造沉降史与主控因素分析

利用伊宁凹陷多口钻/测井、模拟井及地震数据估算了侏罗纪末期地层剥蚀量,且在充分考虑多种因素基础上,应用回剥技术模拟分析了该区中二叠世以来构造沉降史。研究表明,伊宁凹陷中二叠世以来主要经历了3次快速沉降、2次缓慢沉降与2次区域性快速抬升剥蚀的过程。其中,中二叠世-早三叠世为最大构造沉降期,沉降中心位于中央凹陷带霍城地区,海西期火山裂谷后热沉降作用是造成此次沉降的直接因素;早侏罗世与新近纪以后沉降次之,构造运动形成的差异性升降规律是这2次快速沉降的主要成因;侏罗纪末期-白垩纪早期为主要剥蚀抬升期,伊宁凹陷西部剥蚀强度远远大于东部地区,具有明显的东西差异性。     

造气装置废热锅炉炉管泄漏分析

中国石油大庆石化公司化工二厂1503废热锅炉建于2008年初,于2008年7月安装投入使用。锅炉 建成后,进行了去应力处理,并分别于2008年1月31日和2月1日对壳程和管程进行了压力试验,最后经过探伤检 验,检测结果均合格。运行至2011年2月发生泄漏,通过对泄漏的炉管进行化学成分、金相、力学性能等一些列分 析,确认泄漏的直接原因是由于高温氧化造成炉管材质发生变化,强度等性能下降。通过对原料成分进行分析,最 终确认原料成分发生变化,导致在炉管内部结垢,热量不能及时带走,最终导致超温。     

浅埋深综放工作面过冲刷带时支架-围岩相互作用关系研究

 摘要：神东保德矿81304工作面过地表冲刷带时出现工作面液压支架被压死事件。本文根据工作面地质条件及现场情况,运用“支架-围岩”相互关系推演了支架被压死的过程,分析地质变化因素对“压架”事件的影响,建立综放工作面围岩-支架稳定性力学模型。通过分析可知,当综放工作面支架支护强度不足时,支架支护效率会急剧下降;工作面上覆基岩厚度陡增40m是导致保德矿支架被压死的主要因素。     

Erosion corrosion of low-alloy wear-resistant steels in alkaline slurry

Erosion corrosion causes significant problems in various industrial environments through a synergistic effect which results in much greater weight loss than the sum of the weight losses in the individual processes. The erosion-corrosion behavior of three low-alloy steels was investigated in a simulated concrete slurry using the rotation method. The key influencing factors and mechanism of material degradation were analyzed. The experimental results indicate that the weight loss increases with the linear velocity according to a nearly exponential relationship (W = KVⁿ), where n is 1. 40–2. 14. This weight loss is mainly caused by erosion in the alkaline slurry, and steels with higher tensile strengths show higher erosion-corrosion resistance. The formation of many platelets and ring cracks and their removal from the sample surface during erosion corrosion in the slurry are thought to constitute the mechanism responsible for this weight loss. These platelets and ring cracks are formed by solid particles striking the sample surface. Craters are initially produced and subsequently disappear as they grow and come in contact with each other. Fewer craters were observed on the surfaces of samples that exhibited higher weight loss. The surface of the material became work-hardened because of the effect of the particles striking and scratching, and a deformed layer was produced on the surface for steels of lower strengths, leading to deeper and more abundant gouges.     

沙钢2500m~3高炉炉缸侧壁三角形侵蚀的原因分析

沙钢宏发1#高炉(2 500 m3)在2011年年初大修,发现炉缸侧壁在竖直方向呈现出巨大的三角形侵蚀,侵蚀最大处位于炉壳拐点部位,不同于传统的"象脚型"侵蚀。为了调查炉缸部位三角形侵蚀的原因,对炉缸的热应力分布进行了分析,发现竖直方向的正应力对炉缸的侵蚀影响较大,热应力首先集中在炉缸侧壁靠近底部的地方,侵蚀逐渐向碳砖方向发展,当碳砖完全暴露于铁水中后,在残留陶瓷杯和碳砖交界处产生了一条裂纹,该裂纹逐渐向上发展至炉壳拐点上方,待裂纹停止后,随着铁水的流动和有害元素的破坏,炉缸部位逐渐形成了巨大的三角形侵蚀。     

Synthesis and characterization of a novel soil stabilizer based on biodegradable poly(aspartic acid) hydrogel

A novel soil stabilizer based on poly-amino acid - polyaspartic acid (PASP) and its copolymer which modified by xanthan gum (XG) was studied to increase soil particle compressive strength and resistance to wind erosion. Due to its unique property, the stabilizer aggregated individual soil particles and formed crust. The sample compressive strength increased from 0.175 to 0.612 MPa and the wind erosion modulus reduced from 22.43 to 10.56 g·m⁻²·min⁻¹ after the 1% PASP hydrogel was applied by 1.67 Lm⁻² (1 cm of crust). The soil water content was higher than the control due to the polymer’s excellent water-retaining property. The polymer had no negative influence on seed germination and growth. The biodegradability experiment showed that PASP was easy to biodegrade and therefore it was safe to apply in the field. This work was presented at 13 ^th YABEC symposium held at Seoul, Korea, October 20–22, 2007.     

Resuspension and settling of helminth eggs in water: Interactions with cohesive sediments

Helminth parasite eggs in low quality water represent main food safety and health hazards and are therefore important indicators used to determine whether such water can be used for irrigation. Through sedimentation helminth eggs accumulate in the sediment, however resuspension of deposited helminth eggs will lead to increased concentration of suspended eggs in the water. Our study aimed to determine the erodibility (erosion rate and erosion threshold) and settling velocity of Ascaris and Trichuris eggs as well as cohesive sediment at different time points after incorporation into the sediment. Cohesive sediment collected from a freshwater stream was used to prepare a sediment bed onto which helminth eggs were allowed to settle. The erodibility of both sediment and helminth eggs was found to decrease over time indicating that the eggs were incorporated into the surface material of the bed and that this material was stabilized through time. This interaction between eggs and bulk sediment was further manifested in an increased settling velocity of suspended eggs when sediment was present in the suspension as compared to a situation with settling in clean water. The incorporation into the sediment bed and the aggregation with sediment particles decrease the mobility of both helminth egg types. Our findings document that helminth eggs should not be viewed as single entities in water systems when modelling the distribution of eggs since both erodibility and settling velocity of eggs are determined by mobility of the sediment present in the water stream. Recalculation of the erosion threshold for helminth eggs and sediment showed that even at relatively low current velocities i.e. 0.07-0.12 m s⁻¹ newly deposited eggs will be mobile in open irrigation channels. These environmental factors affecting resuspension must be taken into account when developing models for sedimentation of helminth eggs in different water systems.     

Erosion–corrosion of carbon steel in simulated tailing slurries

This paper investigates the synergism of mechanical and electrochemical factors in erosion–corrosion. The fact that active corrosion in the tailing slurry donates a small portion of total material loss indicates that the synergism results mainly from corrosion-enhanced erosion. As theoretically predicted, the erosion rates in corroding slurry under same hydrodynamic condition is a linear function of logarithmic corrosion rate, suggesting that the corrosion-induced surface plasticity is the dominate mechanism of corrosion-enhanced erosion. The reduced resistance to plastic deformation in surface layer while exposed to corroding media is demonstrated by the in situ micro-hardness measurements. The erosion-enhanced corrosion in flowing slurry of steel is a result of dynamic plastic deformation caused by erodent impingement.