PC及PC/ABS共混物的疲劳裂纹扩展研究

研究了聚碳酸酯(PC)和PC/ABS高分子材料的疲劳裂纹扩展规律,利用改进柔度法测量其裂纹扩展速率,采用扫描电子显微镜(SEM)观察其断口形貌,分析疲劳裂纹扩展机理.在较大裂纹扩展速率(10-6～10-3mm/cycle)范围内,PC/ABS的疲劳裂纹扩展速率可以用Paris公式da/dN=9·5587×10-5(ΔK)2·88381来描述.高分子材料PC的疲劳裂纹扩展速率约为高分子材料PC/ABS的3倍.高分子材料PC/ABS疲劳裂纹面上的特征以韧窝为主,较低裂纹扩展速率对应较小的韧窝,较高裂纹扩展速率对应较大的韧窝.高分子材料PC疲劳裂纹面有明显的不连续裂纹扩展带,其裂纹面相对较平.     

金属应变电化学研究进展

从宏观应变电化学现象，到微观层次的局部裂纹环境测量与模拟、裂纹扩展预测模型化、再钝化法确立裂纹扩展速率以及应变电化学过程控制等方面，综述了金属应变电化学的发展历程和主要的研究进展。     

连续碳纤维增强的聚芳醚酮在Ⅰ型循环载荷下的层间破坏

用双悬臂梁(DCB)试件研究了连续碳纤维增强的聚芳醚酮复合材料(CF/PEK-C),在Ⅰ型循环载荷作用下的层间裂纹扩展行为.循环载荷采用载荷控制模式,最小载荷与最大载荷之比为0.5.在疲劳试验中,仍然发现有“阻力曲线”现象存在.层间裂纹扩展速率用指数定律与相应的应变能释放速率联系起来,并对结果进行了讨论.     

预制裂纹304SS试样慢拉伸过程EN和SKP表征

应用电化学噪声技术(EN)研究了慢应变速率拉伸(SSRT)条件下预制疲劳裂纹的304SS试样在4mol/LNaCl+0.01 mol/LNa2S2O3溶液中的腐蚀行为,EN的时域与频域谱图显示实验后裂纹发生了扩展.扫描Kelvin探针(SKP)分析也证实了裂纹试样经慢拉伸实验后裂纹出现扩展.     

连续碳纤维增强的聚芳醚酮在Ⅰ型循环载荷下的层间破坏

 用双悬臂梁(DCB)试件研究了连续碳纤维增强的聚芳醚酮复合材料(CF/PEK-C),在Ⅰ型循环载荷作用下的层间裂纹扩展行为.循环载荷采用载荷控制模式,最小载荷与最大载荷之比为0.5.在疲劳试验中,仍然发现有“阻力曲线”现象存在.层间裂纹扩展速率用指数定律与相应的应变能释放速率联系起来,并对结果进行了讨论.     

不同应变速率下纳米橡胶颗粒对环氧树脂的增韧特性与机理分析

为了解释不同应变速率下纳米橡胶颗粒对环氧树脂基体的增韧机理,制备了质量分数为6%的纳米橡胶颗粒/环氧树脂复合材料,分别测试了该材料在3种低应变速率(5×10-4s-1,1×10-1s-1,2.5×10-1s-1)和高应变速率下(90 s-1)的I型平面断裂韧性.结果表明,纳米橡胶颗粒在3种低应变速率下可以显著提高环氧树脂的断裂韧性,提高幅度分别为158%,283%和309%.在高应变速率下,纯环氧树脂的断裂韧性由于动态效应而显著升高,然而纳米橡胶颗粒对环氧基体的增韧效果却不明显,增韧幅度仅为2%.由光学显微镜照片可知,随着应变速率的提高,纳米橡胶颗粒/环氧树脂复合材料断口表面的应力发白区域逐渐较少,甚至在高应变速率(90 s-1)下消失.偏光显微镜照片表明,纯环氧树脂与纳米橡胶颗粒/环氧树脂复合材料的裂纹尖端塑性形变尺寸随着应变速率的升高而减小.通过扫描电子显微镜对断口形貌进行分析可知,不同应变速率下纳米橡胶颗粒在环氧基体中空穴增长程度不同,进而导致纳米橡胶颗粒对环氧基体的增韧效果的不同.     

超临界二氧化碳中卟啉与钴(II)、镍(II)、锌(II)配合物反应动力学

用紫外-可见光谱研究了钴(II)、镍(II)、锌(II)的1,1,1,5,5,5-六氟-2,4-戊二酮-二水配合物[M(hfac)2(H2O)2,M=Co、Ni、Zn]与5,10,15,20-四(五氟苯基)卟啉[H2tpfpp]在超临界二氧化碳中反应生成金属卟啉[M(tpfpp)]的反应动力学.在金属配合物大大过量时,反应对卟啉为一级.其表观一级速率常数随钴(II)、镍(II)配合物的浓度增加先增加、而后趋于稳定,而表观一级速率常数随锌(II)配合物的浓度增加线形增加.根据实验事实,讨论了反应的机理,得到了相应的热力学和动力学参数.     

超临界二氧化碳中卟啉与钴(II)、镍(II)、锌(II)配合物反应动力学

用紫外-可见光谱研究了钴(II)、镍(II)、锌(II)的1, 1, 1, 5, 5, 5-六氟-2, 4-戊二酮-二水配合物[M(hfac)2(H₂O)₂, M=Co、Ni、Zn]与5, 10, 15, 20-四(五氟苯基)卟啉[H2tpfpp]在超临界二氧化碳中反应生成金属卟啉[M(tpfpp)]的反应动力学. 在金属配合物大大过量时, 反应对卟啉为一级. 其表观一级速率常数随钴(II)、镍(II)配合物的浓度增加先增加、而后趋于稳定, 而表观一级速率常数随锌(II)配合物的浓度增加线形增加. 根据实验事实, 讨论了反应的机理, 得到了相应的热力学和动力学参数.     

N’-苄基酰腙分子的氮-氮键旋转位阻及分子构象

采用动态核磁共振波谱(DNMR)和密度泛函理论(DFT)对N'-苄基酰腙化合物进行构象研究. 实验和理论计算表明, 1H NMR图谱中三组不同质子的双峰裂分是由N—N键旋转位阻造成的, 而这三个双峰裂分的化学位移差异随温度升高而减小. 通过模拟化学位移差异与温度的关系, 得到了交换速率常数, 采用Eyring方程计算出N—N键旋转位阻. 提出顺式和反式共存的模型来分析酰胺质子信号分裂的原因, 并利用DFT计算得出优化的异构体构象及其最低能量. 端甲基质子和次甲基质子信号裂分也来源于N—N键旋转受阻. N'-苄基酰腙通过缩合反应转变成1,3,4-二唑化合物, 消除了甲基空间取向的差异, 其信号变为单峰.     

拉伸取向尼龙1010样品的抗张回复

研究了拉伸取向尼龙 10 10的抗张回复现象 .残存应变ε′表征了由链滑移而产生的永久形变 ,回复应变(ε -ε′)表征了键角变化和链段取向产生的形变 .当拉伸温度T=18℃ (T 相似文献   

Effect of Potential Perturbation Polarization on the Stress Corrosion Cracking of Type 321 Stainless Steel

Ithasbeenwidelyacceptedthatelectrochemicalcorrosionreactionsareinvolvedinthe.stresscorrosioncrackingprocessesofmostmetaljaqueoussolutionsystems'.Accordingtothecharacteristicsofdynamicstrainatthecracktipofmetal,itisofgreatimportancetostudytheinfluenceofvariedpotentialsonthedynamicstrainprocessatcracktipbydifferentpotentialpertllrbationsbetweenanodicandcathodicpotCntials.SmoothcylindricaltensilespecimenwasusedinSSRT(strainrate4.l6x's-').Allexperimentswereperformedino.75molILHCl O.25molILNa…     

双相不锈钢在水溶液中之腐蚀疲劳与动态应变时效

本研究主要探讨 2 2 %Cr双相不锈钢在含氯离子水溶液中之腐蚀疲劳裂缝成长行为 ,以及在慢应变速率拉伸试验过程中所发生的动态应变时效现象 .同时以 31 6L沃斯田体系不锈钢及4 30肥粒体系不锈钢作为比较 ,藉以探讨不同晶体结构对腐蚀疲劳及动态应变时效行为的影响 .实验结果显示 ,在 80℃ ,3.5wt%NaCl水溶液中 ,3种不锈钢并未发生应力腐蚀破裂 ,但其中 31 6L沃斯田体系不锈钢及 2 2 %Cr双相不锈钢却发生动态应变时效 ,且动态应变时效的发生与温度 ,应变速率及沃斯田体相的组织有关 .在NaCl水溶液中 ,采用预裂试片量测疲劳裂缝生长速率 ,其结果表明 ,4 30肥粒体系不锈钢之疲劳裂缝生长速率最快 ,而氢脆是加快裂缝生长速率的主因 ,就双相不锈钢而言 ,腐蚀疲劳裂缝的生长主要与该不锈钢所含之肥粒体相的氢脆现象有关     

亚稳态304不锈钢应力腐蚀影响因素探讨

30 4不锈钢通过低温拉伸制得含有不同马氏体相变量的试样 ,由于冷加工将不可避免地导致位错密度大幅度增加 ,利用铁素体测量仪和透射电镜 (TEM )检测并分析 30 4不锈钢位错形态 .上述试样在 4 2 %MgCl2 沸腾溶液中用慢应变速率法 (SSRT) ,结合金相显微镜 ,扫描电子显微镜等表面分析手段 ,探讨了微观组织变化对 30 4不锈钢应力腐蚀的影响 .结果表明 :由于马氏体相和位错缺陷的交互作用 ,影响了 30 4不锈钢在沸腾MgCl2 溶液中应力腐蚀敏感性 ,且在不同变形量范围内 ,影响的主导因素不同     

Etude phenomenologique de l'amorçage et de la propagation de fissures de corrosion sous contrainte. Application a l'acier inoxydable z 2 cn 18.10 dans le chlorure de magnesium

A purely phenomenological study of Stress Corrosion Craking (SCC) was performed using the couple AISI 304L austenitic stainless steel / boiling magnesium chloride aqueous solution. The exploitation of the morphological information (shape of the cracks and size distribution) available after constant elongation rate tests led to the apparent initiation of the cracks and to their growth rate. A law for the real initiation is proposed too and the elongation rate effect is quantitatively characterized.     

Evaluation of surface water–groundwater interaction using environmental isotopes (D, 18O and 222Rn) in Chongli Area,China

Predicting the electrical corrosion potential (ECP) of type 304 stainless steel, the structural material of recirculation pipes in fusion power plants, is important because the growth rate of intergranular stress corrosion crack (IGSCC) of 304 stainless steel is closely related to ECP. In this work, a new model has been developed, by modifying existing models, to calculate the ECP of recirculation pipes in future fusion power plant. The calculation results indicate that merely injecting hydrogen cannot reduce ECP below E_IGSCC if the dose rate exceeds a threshold, other assisted water chemistry controlling method is necessary.

     

An Electrochemical Study on the Corrosion Inhibition of Stainless Steel by Polyaniline Film

Polyaniline(PANI)film was electrosynthesized on 304 stainless steel by cyclic voltammetry using aqueous oxalic acid as supporting electrolyte.The potential sweep rates were changed to achieve the PANI film with different thickness and structures.Protective properties of the PANI film for corrosion of stainless steel in 3% NaC1 aqueous solution were investigated by monitoring potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS).The results showed that the PANI film which was formed with lower sweep rate led to more positive shift of corrosion potential and greater charge transfer resistance,reflecting higher inhibition for corrosion of the stainless steel.     

Effect of thermal annealing of poly(3-octylthiophene) films covered stainless steel on corrosion properties

The effect of thermal annealing of poly(3-octylthiophene) (P3OT) coatings on the corrosion inhibition of stainless steel in an NaCl solution was investigated. P3OT was synthesized by direct oxidation of the 3-octylthiophene monomer with ferric chloride (FeCl₃) as oxidant. P3OT films were deposited by drop-casting technique onto 304 stainless steel electrode (304SS). 304SS coated with P3OT films were thermally annealed during 30 h at different temperatures (55°C, 80°C, and 100°C). The corrosion resistance of stainless steel coated with P3OT in 0.5 M NaCl aqueous solution at room temperature was investigated by using potentiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy. The results indicated that the thermal treatment at 80°C and 100°C of P3OT films improved the corrosion resistance of the stainless steel in NaCl solution; the speed of corrosion diminished in an order of magnitude with regard to the 304SS. In order to study the temperature effect in the morphology of the coatings before and after the corrosive environment and correlate it with corrosion protection, atomic force microscopy and scanning electron microscopy were used. Morphological study showed that when the films are heated, the grain size increased and a denser surface was obtained, which benefited the barrier properties of the film.     

A study on the electrochemical polymerization, characterization, and corrosion protection of o-toluidine on steel

Poly(o-toluidine) (POT) coatings were electrochemically synthesized on 304 stainless steel using cyclic voltammetric method. These coatings were characterized by Fourier transform infrared spectroscopy, UV–vis absorption spectroscopy, and cyclic voltammetry. The corrosion performance of POT coating in aqueous 3 wt% sodium chloride was assessed by the electrochemical techniques such as open circuit potential measurements, potentiodynamic polarization technique, cyclic potentiodynamic polarization measurements, and electrochemical impedance spectroscopy. The results reveal that POT coating on 304 stainless steel prevents general and localized corrosion, and reduces the exchange current density almost by a factor of 45 than bare 304 stainless steel.     

Corrosion behaviors of materials in aluminum chloride–1-ethyl-3-methylimidazolium chloride ionic liquid

The corrosion properties of carbon steel (CS), 304 stainless steel (304 SS), and pure titanium (Ti) are first studied in aluminum chloride–1-ethyl-3-methylimidazolium chloride ionic liquid (IL). An active-to-passive transition behavior was clearly observed for CS. The 304 SS exhibited the best stability among the materials; no considerable corrosion was recognized even in this high-chloride environment. In contrast, although Ti resists corrosion in ambient environments, it was not passivated in the IL and became severely corroded under an anodic applied potential. The material corrosion behaviors and mechanisms in the non-aqueous, low-oxygen, and high-halogen-containing IL are completely different from those in traditional aqueous solutions.     

Study on the Corrosion Resistance of 304L Stainless Steel

304L is an austenitic stainless steel with very low carbon content, and is served as the application to the oxidizing media, however, its corrosion resistance is not satisfactory in reducing media. For example, the pitting corrosion occurred on 304L stainless steel tube, which had been mounted for one year, somewhere at the power station in die seashore of China. For this reason we have studied the corrosion behavior of 304L in some media and invented a novel surface treatment technique of stainless steel for extremely improving the corrosion resistance of 304L. The characteristics of the modified passive film on the steel were examined in this paper, and the corrosion resistance of treated 304L stainless steel was tested in our laboratory and the testing ground. The results are satisfactory.