Effects of strain-induced melt activation treatment on the microstructure and properties of Zn sacrificial anodes

The microstructural properties and electrochemical performance of zinc(Zn)sacrificial anodes during strain-induced melt activation(SIMA)were investigated in this study.The samples were subjected to a compressive ratio of 20%-50% at various temperatures(425-435℃)and durations(5-30 min).Short-term electrochemical tests(anode tests)based on DNV-RP-B401 and potentiodynamic polarization tests were performed in 3.5wt%NaCl solution to evaluate the electrochemical efficiency and corrosion behavior of the samples,respectively.The electrochemical test results for the optimum sample confirmed that the corrosion current density declined by 90% and the anode efficiency slightly decreased relative to that of the raw sample.Energy-dispersive X-ray spectroscopy,scanning electron microscopy,metallographic images,and microhardness profiles showed the accumulation of alloying elements on the boundary and the conversion of uniform corrosion into localized corrosion,hence the decrease of the Zn sacrificial anode’s efficiency after the SIMA process.

Effects of pre-deformation on microstructure and tensile properties of Al-Zn-Mg-Cu alloy produced by modified strain induced melt activation

The effects of Al-8B grain refiner on microstructure and tensile properties of an Al-12Zn-3Mg-2.5Cu alloy produced by modified strain induced melt activation process were investigated. Pre-deformation of 60% was used by hot working at 300 ℃. After pre-deformation, the samples were heated to a temperature above the solidus and below the liquidus point and maintained in the isothermal conditions at three different temperatures（500, 550 and 590 ℃） for varying time（10, 20 and 40 min）. It was observed that strain induced melt activation has caused the globular morphology of α（Al） grains. Microstructural study was carried out on the alloy by using optical microscope and scanning electron microscope in both unrefined and B-refined conditions. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 550 ℃ and 10 min, respectively. After the T6 heat treatment, the average tensile strengths increased from 278 to 585 MPa and 252 to 560 MPa for samples refined with 3.75% Al-8B before and after SIMA process, respectively. The ultimate strength of SIMA specimens is lower than that of B-refined specimens.

Electro-deposition tangsten coating on low activation steel substrates from Na_2WO_4-ZnO-WO_3 melt salt

Tungsten coating is considered as a promising alternative material for plasma facing materials(PFC) in future fusion devices.The electro-deposition of tungsten in Na_2WO_4-ZnO-WO_3 melt at 1173 K on low activation steel substrates was studied in this work.Adherent and smooth tungsten films were deposited under various pulsed current conditions.The crystal structure and microstructure of tungsten deposits were characterized by XRD,SEM and EDX techniques.The results show that pulsed current density and duty cycle have a significant influence on tungsten nucleation and electro-crystallization phenomena.Uniform and smooth tungsten coating with high purity and high adherence is obtained on low active steel substrates as cathodic current density ranges from 35 to 25 mA·cm_(-2).

Equivalent conductivity and its activation energy of NaF-AlF_3 melts

Electrical conductivity of NaF-AlF3 melts was measured by continuously varying cell constant(CVCC) technique. Relationships between equivalent conductivity at 990-1 030 ℃ and temperature and composition, and relationship between equivalent conductivity activation energy and composition of the melts were then studied on the basis of two-step decomposition mechanism of AlF63-. According to the changes of molar fractions of different anions in NaF-AlF3 melts, courses of dependence of equivalent conductivity and its activation energy on composition were analyzed. The results show that the influence of temperature on equivalent conductivity of the melts is small in the researched temperature range, and equivalent conductivity increases with increasing the molar fraction of AlF3; there is a minimum point in the activation energy—composition curve when molar fraction of AlF3 is 0.29.

Preparation of AZ91D magnesium alloy semi-solid billet by new strain induced melt activated method

New strain induced melt activated (new SIMA) method for preparing AZ91D magnesium alloy semi-solid billet is introduced by applying equal channel angular extrusion into strain induced step in SIMA method, by which semi-solid billet with fine spheroidal grains and average grain size of 18 μm can be prepared. Furthermore, average grain size of semi-solid billet is reduced with increasing extrusion pass of AZ91D magnesium alloy obtained in ECAE process. By using semi-solid billet prepared by new SIMA, thixoforged magazine plates component with high mechanical properties such as yield strength of 201.4 MPa, ultimate tensile strength of 321.8 MPa and elongation of 15.3%, can be obtained.

1-Methyl-3-octylimidazolium Polyoxomolybdate Ionic Liquid with Low Melting Point and High Stability:Preparation and Photocatalytic Activity

The polyoxometalate（POM）-imidazole ionic liquid（IL） [C8mim]2[Mo6O19]（C8mim=1-methyl-3-octylimi- dazolium） with a low melting point of 82.6 °C was successfully prepared and characterized by FTIR, XPS, NMR, TG and so on. The polyoxomolybdate-based IL has high stability, and its decomposing temperature reaches 321 °C, which is higher than that of 1-alkyl-3-methylimidazolium halides IL. Further photocatalytic performances of the IL were measured via degrading dye rhodamine B（RB） in aqueous solution under the UV light irradiation. The experiments show that the conversion of RB reaches 80.5% after 90 min under UV-light and the degradation efficiency depends on the pH value of the solution, irradiation time and the dosage of the IL and so on.

Activity Interaction Coefficients of Si in Cu-Ti-Si Melts at 1550℃

Activitibs of Si in binary Cu-Si and ternary Cu-Ti-Si melts were measured at 1 550℃ by using a method of chemical equilIbrium between gas and liquid. The activity interaction coefficients of Si in the melts have been determined from the experimental data (lny = -5.69. s = 6.69. P2: = -26.22. E; =-43.96) and activity interaction coefficients of Ti in binary Cu-Ti melt at 1550℃ has been estimated from Sommer's data based on the regular solution model (lny =-1 .10. : = 2.95.p:=-2.10).

寒区道路桥梁融雪除冰技术研究综述

道路桥面的融雪除冰对车辆行驶安全至关重要,但是目前对于融雪除冰技术的研究主要集中在工程效果及技术评价上,尚未从除冰工作机理进行对比分析和系统阐述。该文基于融雪除冰机理将融雪除冰技术分为被动式除冰技术、主动融雪除冰技术以及能量利用型融雪除冰技术3类,并对其进行归纳总结。系统评价了融雪剂除冰法、机械除冰法两项传统除冰手段的优缺点;探讨了抑制类冻结铺装路面、相变材料路面两项主动融雪除冰技术,并提出相变材料用于路面融雪除冰具有绿色环保价值;介绍了不同能量利用型融雪除冰技术的应用机理。深入分析现有的道路除雪技术及其实际应用效果和存在的问题,以期对寒区道路桥梁冬季融雪除冰研究提供基础性支撑。

斑岩-矽卡岩型钼矿成矿控制因素

本文从成钼矿岩浆的化学组分和物理化学性质,以及成钼矿流体的出溶和金属堆积过程两个层次,探讨了斑岩-矽卡岩型钼矿的成矿控制因素。研究揭示,不同构造环境中的斑岩-矽卡岩型钼矿的成矿岩浆均不富集钼,氧化性富水岩浆是形成斑岩-矽卡岩型钼矿的基础,成矿流体沿岩浆房顶部衍生的小岩株高度聚集是成钼矿之关键环节。研究还揭示,大型-超大型斑岩-矽卡岩型钼矿均具有多期岩浆-热液活动叠加成矿的特点,成矿岩体与大岩浆房相连,并且成矿岩浆能多期侵位与成矿,是形成大型-超大型钼矿的关键因素。综合来看,斑岩-矽卡岩型钼矿是岩浆体量、岩浆氧逸度和水含量、流体聚集程度以及多期岩浆-热液活动叠加成矿多因素耦合的产物。岩浆体量、岩浆氧逸度和岩浆水含量是基础,流体聚集程度是关键,要形成大型-超大型斑岩-矽卡岩型钼矿,还需要多期岩浆-热液活动的叠加成矿。研究提出,寻找斑岩-矽卡岩型钼矿,在关注岩体地球化学属性的同时,还应关注岩体的空间结构属性以及多期岩浆-热液活动叠加成矿特征的识别。

中国活火山喷发物对航空安全的影响评估

火山活动对航空安全有着重要的影响。爆炸性火山喷发产生的火山灰可通过物理磨蚀和化学腐蚀的方式破坏飞机发动机的热障涂层,从而降低其服役寿命,影响飞行安全。我国分布有多座活火山,尤其是长白山、五大连池和腾冲火山区,地球物理和水热活动资料都显示其具有再次喷发的潜力。随着航空运输业在我国扮演着越来越重要的角色,这些火山一旦喷发将对我国空域范围内的飞行安全产生举足轻重的影响,因此评估这些火山对航空安全可能的影响具有重要的现实意义。本文利用收集和测试的共2275组地球化学数据,借助硅酸盐熔体黏度模型计算了发动机燃烧室最低运行温度1200℃下不同火山区不同时期的火山喷发物的黏度,评估了长白山、五大连池、镜泊湖、龙岗、双辽、腾冲和环太平洋火山区不同阶段的火山活动对飞行安全可能的影响。研究结果表明微量元素Co、V、Ni和Cr的含量与体系黏度呈负相关关系,而Rb含量则与体系黏度呈正相关关系。东北地区火山区(包括长白山、五大连池、镜泊湖、龙岗和双辽)和西南地区腾冲火山区黏度分别自0.52Ma和1.05Ma开始具有明显下降的趋势,环太平洋火山区黏度在10^(0.70)~10^(5.90)Pa·s范围内周期性波动,自18Ma以来,呈现波动下降的趋势。黏度的下降意味着喷发物被发动机摄取之后更容易铺展,从而增大与热障涂层间的接触面积,加大破坏涂层的可能性,这表明位于我国密集航线上的东北地区、西南地区以及环太平洋火山区的火山活动对航空安全的威胁都呈上升趋势。本文为不同区域、不同年龄的火山喷发物对航空安全影响的评估提供了定性比较的参数,同时也为国际航空安全决策提供了来自中国火山区数据的参考。

稀土Gd对Ni-Cr-Mo合金热变形行为的影响

含Gd镍铬钼合金作为乏燃料贮运用中子屏蔽材料具有广阔的应用前景,却在热加工时极易发生开裂,为了优化合金热变形工艺参数,本文以Ni-Cr-Mo合金为研究对象,研究了Gd加入后引起的组织变化。在变形温度为1 000~1 200℃、应变速率为0.01~5 s^(-1)条件下进行等温热压缩实验,计算合金相关材料常数及热变形激活能,构建热加工图并确定热加工窗口,结合微观组织进行分析,研究Gd对合金热变形行为的影响。结果表明,Ni-Cr-Mo合金中加入了1.2%的Gd,合金的变形激活能从472.15 kJ/mol降至422.9 kJ/mol,在热变形时合金的能量消耗效率更高,组织演变更充分,塑性失稳区域由高温向低温逐渐转移,并且增大了合金在1 000~1 060℃,0.01~0.32 s^(-1)低温低应变速率下安全区的面积。合金最佳热加工区间为:0.5真应变量,温度(T)为1 113~1 164℃,应变速率(ε)为0.01~0.2 s^(-1)。Gd在晶界或枝晶间以金属间化合物GdNi_(5)析出,GdNi_(5)相作为硬脆相,在热变形过程中其周围产生较大应变,导致组织中畸变能更高,从而促进周围变形晶粒发生再结晶,降低组织中的残余应变。

相变材料在冬季沥青路面中的应用分析

沥青路面在冬季低温雨雪气候下易发生结霜、结冰现象,致使路面抗滑性能降低,从而导致事故发生率上升,给行车安全及路面使用性能带来严重影响。传统的被动式除雪法效率低,且须占用行车道影响道路正常运行,化学融雪剂还会造成土壤和水污染。本文通过文献调研,总结常见的主动融雪化冰路面类型,分析相变材料在沥青路面中的应用研究重点,提出将相变材料掺入沥青路面中,以预防或减少冬季沥青路面冰冻病害。

Changes of Terrestrial Water Storage in the Yellow River Basin Under Global Warming

The increasing temperature in the Yellow River Basin has led to a rapid rise in the melting level height,at a rate of 5.98 m yr^(-1)during the cold season,which further contributes to the transition from snowfall to rainfall patterns.Between 1979 and 2020,there has been a decrease in snowfall in the Yellow River Basin at a rate of-3.03 mm dec^(-1),while rainfall has been increasing at a rate of 1.00 mm dec^(-1).Consequently,the snowfall-to-rainfall ratio(SRR)has decreased.Snowfall directly replenishes terrestrial water storage(TWS)in solid form until it melts,while rainfall is rapidly lost through runoff and evaporation,in addition to infiltrating underground or remaining on the surface.Therefore,the decreasing SRR accelerates the depletion of water resources.According to the surface water balance equation,the reduction in precipitation and runoff,along with an increase in evaporation,results in a decrease in TWS during the cold season within the Yellow River Basin.In addition to climate change,human activities,considering the region's dense population and extensive agricultural land,also accelerate the decline of TWS.Notably,irrigation accounts for the largest proportion of water withdrawals in the Yellow River Basin(71.8%)and primarily occurs during the warm season(especially from June to August).The impact of human activities and climate change on the water cycle requires further in-depth research.

高活性聚苯硫醚树脂的制备及其性能研究

本文研究探讨了不同端基调节剂对聚苯硫醚(PPS)树脂实施端基处理后对其反应活性及熔融结晶温度(Tc2)的提升。通过对比分析,发现以含羟基芳香族硫醇化合物为端基调节剂时,PPS树脂的反应活性和Tc2提升更明显。后续洗涤纯化过程中增加酸洗步骤,可以进一步促进树脂反应活性与Tc2的提升,对于优化共混改性挤出过程中复合材料的整体性能尤为关键。

再生铅富氧侧吹熔炼SNCR干法脱硝工艺实践

再生铅富氧侧吹熔炼在再生铅领域占有突出地位。由于国家环境政策趋严,要求富氧侧吹熔炼进行脱硝处理。脱硝工艺主要有氧化法、SCR法及SNCR法。本文中,笔者介绍了再生铅富氧侧吹熔炼炉脱硝工艺,重点介绍了氧化法脱硝工艺和SNCR高温干法脱硝工艺,分析了这两种工艺的优、缺点。并且,详细讨论了SNCR高温干法脱硝工艺在生产实践中的应用。

预取向聚乳酸薄膜的力学性能

聚乳酸是一类可生物降解的环保型绿色高分子材料。通过熔体拉伸方法制备的聚乳酸薄膜有高模量、高韧性的特征,在包装领域有广泛的应用前景。研究预取向的聚乳酸薄膜的力学性能有重要的现实意义。本文采用基本断裂功法和埃林(Eyring)理论计算了样品的韧性和屈服活化能。结果发现,随着牵伸比的增加,薄膜的结晶度提升,屈服强度增加,拉伸硬化现象明显。采用基本断裂功方法研究了不同牵伸比PLA薄膜的韧性,随着牵伸比的增大,比基本断裂功逐渐增加,比非基本断裂功呈现先增加后减小的趋势。结晶度的增加抑制了内部缺陷的扩展,导致成颈-撕裂塑性功呈线性增加的趋势。慢速拉伸时,屈服破坏来自非晶区的塑性变形,屈服活化能约为13~14 kJ/mol,快速拉伸导致晶区-非晶区界面滑移,屈服活化能仅有7 kJ/mol。

铱的溶解造液技术研究现状

随着我国科技和经济水平的不断进步,铱在高精尖领域的需求量逐年增长。然而,铱的原生矿产资源极为稀缺,从二次资源中高效回收铱具有重要意义。其中,铱的高效溶解造液是行业一大难题,严重制约铱回收行业的发展。本文综述铱的溶解造液技术,包括金属活化法、碱熔法、加压消解法和电化学溶解法,系统剖析和对比各种溶解技术的优缺点。现有技术存在溶解效率低、返料多、能耗高等问题,开发绿色、高效、节能的溶解造液技术是未来铱溶解技术的研究方向。

玻璃熔体电导活化能和黏滞活化能的测量与计算

介绍玻璃熔体2种常见的电导活化能和黏滞活化能的应用与测试机理,并以无碱玻璃纤维配方的玻璃熔体为例测算其电导活化能和黏滞活化能。结果表明,无碱玻纤熔体的电导活化能为162.6~194.9 kJ/mol,黏滞活化能为247.3~257.2 kJ/mol。采用B_(2)O_(3)替代等质量分数的CaO后,虽然玻璃熔体的电阻率和黏度增加,但电导活化能和黏滞活化能都降低,表明玻璃熔体的活化能受组分变化影响,具体影响机理和程度有待进一步研究。

Unsteady state precipitation of M_(23)C_(6)carbides during thermal cycling in reduced activation steel manufactured by laser melting deposition

The temperature field distribution and thermal history of Fe-9Cr2WVTa reduced activation steel prepared by laser melting deposition(LMD)have been calculated with Gaussian and Ring laser beams,and the nucleation and growth behaviors of M_(23)C_(6)precipitates in the 1st,7th and 19th layers have been calculated using the modified classical nucleation theory and Svoboda Fischer Fratzl Kozeschnik model.The energy distribution shows W-shape with Ring laser beam while it shows V-shape with Gaussian laser beam,which results in the more uniform M_(23)C_(6)size in the same layer with Ring laser beam.Precipitates in the bottom(i.e.,the 1st layer)have the minimum size and the size increases with the layer number with Gaussian and Ring laser beams.The temperature history,the instantaneous nucleation rate and the size evolution of M_(23)C_(6)have been systematically discussed.The results indicate that the nucleation,growth and re-dissolution of precipitates in reduced activation steel depend on the amount of energy absorbed in the thermal cycle during LMD.The continuous accumulation of energy during the thermal cycle leads to larger M_(23)C_(6)at the top area.The unsteady state precipitation dynamics of M_(23)C_(6)carbides during thermal cycling are consistent with the simulation results.

Calculation Model for Surface Tension of Slag Melt

Based on the coexistence theory of slag melt structure and Butler’s equation,a new calculation model has been proposed for the calculation of surface tension of slag melt.This model establishes a specific correlation between surface tension and mass action concentrations(activities) in the melt and on its surface on the basis of inner and surficial structures of slag melt.Calculated surface tensions of CaO-SiOand MnO-SiOslag melts are consistent with those measured.Furthermore,iso-surface tension lines of CaO-MnO-SiOslag melt have also been calculated.