Calculation of non－mono chromatic reflectance of Co／Sb multilayer

It is well known that the structure defects, such as the interfacial roughness, interdiffusion and chemical reaction at interface, can degrade the optical properties for soft X-ray multilayer[1—5]. For example, the interfacial rough-ness can lead to a loss of spectral reflectance, which has been investigated for many years, and number theories for the scattering of electromagnetic radiation by interfacial roughness have been formulated[6,7]. In addition, the fluc-tuation of the period can als…     

Study on delayed cracking of conductive notch under electric field in PZT-5H ferroelectric ceramics

Internal electrodes have widely been adopted in electronic and electromechanical devices made of ferroelectric ceramics. There embedded electrodes naturally function as a pre-conductive notch, which lead to the failure of the devices under electric and/or…     

H_2SO_4－NaCl溶液中奥氏体不锈钢应力腐蚀开裂

在室温下研究了奥氏体不锈钢在Ｈ＿２ＳＯ＿４－ＮａＣｌ溶液中的应力腐蚀开裂敏感性．结果表明，应力腐蚀受外加电位和氯化物浓度的影响．在２．５（Ｈ＿２ＳＯ＿４）－０．２～０．６ｍｏｌ·ｄｍ￣（－３）（ＮａＣｌ）溶液中发生穿晶型应力腐蚀开裂，在极化曲线的活化。钝化过渡区电位区间发生腐蚀开裂。应力腐蚀开裂可归因于位错的滑移台阶出现而导致钝化膜的破裂，再经过选择性电化学溶解而产生．     

二氧化硫复合盐雾环境下2024-T351铝合金应力腐蚀开裂

通过SO2复合盐雾试验模拟工业污染海洋大气环境,结合有限元模拟分析、扫描电镜/能谱仪、光电子能谱分析等技术研究2024-T351铝合金在弹性应力区间的应力腐蚀开裂行为.结果表明:应力腐蚀开裂行为优先发生在2024-T351铝合金C型环的顶部应力集中区域;疏松的腐蚀产物层的形貌经历了由细棒状、团絮状到板块状的变化;试验6h就可以监测到裂纹,进行到480h的时候有贯穿裂纹形成,720h的时候试样完全断裂;裂纹为穿晶和沿晶混合机制,主裂纹以穿晶机制沿C型环法线扩展,二次裂纹沿晶界扩展.     

硫化氢环境下两种不锈钢的应力腐蚀开裂行为

用U形弯试样浸泡和慢应变速率拉伸实验研究了3Cr17Ni7Mo2SiN和00Cr22Ni5Mo3N(2205)不锈钢在硫化氢介质中的应力腐蚀开裂(SCC)行为.2205不锈钢的SCC萌生孕育期较长,在pH较低的饱和H2S溶液中具有明显的SCC敏感性,其SCC敏感性随溶液pH值的升高或H2S含量的降低而迅速降低.3Cr17Ni7Mo2SiN的SCC孕育期均低于2205不锈钢,在pH≤4.5、H2S的质量浓度≥103mg·L-1的H2S介质中均具有明显的SCC敏感性,其SCC敏感性受pH值和H2S含量变化影响较小.3Cr17Ni7Mo2SiN的SCC以沿晶裂纹萌生,扩展后转变为穿晶应力腐蚀开裂;2205不锈钢近表面处首先发生奥氏体-铁素体相间氢致开裂,并促进SCC萌生,其SCC为穿晶应力腐蚀开裂.     

300M超高强度钢电化学性能及应力腐蚀开裂

采用动电位扫描技术和慢应变速率拉伸试验研究了超高强度钢300M在3.5%NaCl溶液中的应力腐蚀行为,并利用扫描电镜观察了不同外加电位下的断口形貌.300M钢在3.5%NaCl溶液中开路电位下的应力腐蚀开裂机制为阳极溶解型,Cl-的存在明显地增加了材料的应力腐蚀开裂敏感性.阳极电位-600 mV下300M钢溶解速率加快,表现出较高的应力腐蚀开裂敏感性,断面收缩率损失由开路电路下的52.6%升高至99.5%,裂纹起源于表面点蚀坑处,应力腐蚀开裂为阳极溶解型机制.阴极电位-800 mV下材料处于阴极保护电位范围,表现出较低的应力腐蚀开裂敏感性,强度和韧度与空气中拉伸的数值相近,开裂机制为阳极溶解和氢致开裂协同作用.在更低电位(低于-950 mV)下,300M钢的应力腐蚀开裂机制为氢致开裂,在氢和拉应力的共同作用下表现出很大的应力腐蚀开裂敏感性.     

Relativity between corrosion-induced stress and stress corrosion cracking of brass in an ammonia solution

The susceptibility to stress corrosion cracking (SCC) of brass in an ammonia solution with various pH values or under various applied potentials was measured at slow strain rate tests. The additive stress in the same solution was measured using two methods. The results indicate that the variation of the susceptibility to SCC with pH value or with potential is in an excellent agreement with the corrosion (passive film or dezincification layer)-induced stress. When pH? 7, the corrosion-induced tensile stress and the susceptibility to SCC have maximum values and hardly change with increasing the pH value. However, when pH<7, both the corrosion-induced tensile stress and the susceptibility to SCC reduce rapidly with decreasing the pH value. Both the corrosion-induced tensile stress and the susceptibility to SCC have maximum values at the open-circuit potential, decrease slightly under the anodic polarization, and reduce gradually to zero under the cathodic polarization.     

混凝土梁的应力腐蚀断裂实验研究

本文研究了带裂纹混凝土梁的应力腐蚀断裂问题。首先确定了混凝土材料在五种腐蚀介质作用下的腐蚀度;然后,在1％盐酸溶液和荷载应力共同作用下,进行了四点弯曲混凝土梁的应力腐蚀断裂实验研究,给出了应力强度因子K_1与腐蚀断裂时间t的关系式,并进行了若干讨论。     

Electrochemical investigation on the hydrogen permeation behavior of 7075-T6 Al alloy and its influence on stress corrosion cracking

The hydrogen permeation behavior and stress corrosion cracking (SCC) susceptibility of precharged 7075-T6 Al alloy were investigated in this paper. Devanthan–Stachurski (D-S) cell tests were used to measure the apparent hydrogen diffusivity and hydrogen permeation current density of specimens immersed in 3.5wt% NaCl solution. Electrochemical experiment results show that the SCC susceptibility is low during anodic polarization. Both corrosion pits and hydrogen-induced cracking are evident in scanning electron microscope images after the specimens have been charging for 24 h.     

钢板梁桥腹板加劲肋焊缝疲劳开裂后的应力特征

通过建立钢板梁桥节段有限元模型分析了主梁腹板与加劲肋连接焊缝部位的开裂特征,基于最不利车辆荷载位置分析了腹板间隙不同横向荷载位置下的正应力与剪应力特征,以及裂纹长度的变化对腹板面外变形的影响;通过对比不同裂纹长度时裂纹尖端和裂纹最深点的应力强度因子值,分析了裂纹长度对裂纹前缘的受力特征以及扩展速率的影响.研究结果表明:...     

pH值对高温高压水中304L不锈钢应力腐蚀开裂的影响

在高温高压水环境中,采用慢应变速率拉伸试验方法,研究了不同pH值对304L不锈钢应力腐蚀开裂行为的影响规律,并通过扫描电镜对试样断口形貌进行观察与分析.结果表明:在300℃时,304L不锈钢在弱酸性和弱碱性溶液中的应力腐蚀开裂敏感性较大,且酸性越强,敏感性越大.在中性溶液中,304L不锈钢的强度和塑性损失较小,应力腐蚀敏感性较小,断口分析与之吻合.     

冷变形316 L不锈钢在高温高压水中的应力腐蚀

采用恒应力强度因子K=33 MPa·m1/2的加载方法,利用直流电压降方法在线监测核辅管道316L不锈钢在高纯水中应力腐蚀裂纹扩展速率。对比200、250、280和325℃温度下,氩气除氧和含有2 mg·L-1溶解氧的水化学环境中材料的裂纹扩展速率发现：溶解氧为2 mg·L-1时的裂纹扩展速率明显比氩气除氧时的裂纹扩展速率高。氩气除氧时,裂纹扩展速率在250℃时有一个最高点;溶解氧为2 mg·L-1的条件下,裂纹扩展速率随温度的升高而升高。     

Spectroscopic study on the photophysical properties of chlorine substituted tetraphenylporphyrin-histidine and its zinc(Ⅱ)complexes

The photophysical properties of ortho-CI,meta-CI and para-CI substituted tetraphenylporphy-rin-histidine and their zinc (II) complexes have been studied by means of steady-state absorption and fluo-rescence spectroscopies, as well as time-resolved fluo-rescence spectroscopy. For the cases of both free-base and zinc complexes, it was found that the ortho-chlorine substitution onto the phenyl rings significantly altered the fluorescence quantum yield, thefluorescence lifetime and the ratio between radiative and nonradiative deactivation rates of the porphyrin chromophore, i.e. the photophysical parameters were quite different from those of meta- and para-substituted compounds. On the other hand, however, the introduction of covalently-linked histidine did not exert much effects on the photophysical behavior of the porphyrin chromophore. The results are interpreted interms of the steric effect and the heavy-atom effect from the chlorine atoms substituted onto the phenyl rings.     

Aligning DNA on Si surface and cutting off by tips of atomic force microscope

DNA is a kind of promising molecule as nano-lead to build or connect nano-devices due to its stable linear structure and certain conductivity. Many methods have been applied to constructing nano-patterns by using DNA molecule. In this report it is presented that λ-DNA was aligned on Si substrate by using the free-flowing method and then imaged by an atomic force microscope (AFM). After the second liquid flow, a catenary-like pattern and a crossed network of λ-DNA were formed. In addition, the aligned λ-DNA was successfully cut off by tips of AFM.     

Changes in the content of eolian iron during the past 900 ka and the implications

In this study, total Fe2O3 content (Fet) in two parallel sections from the central Loess Plateau (Xifeng and Changwu) is analyzed to address the variations of eolian iron in the past 900 ka. The obtained timeseries indicate that Fet Vvalues in some glacial intervals are comparable to that of interglacial periods and its oscillations do not generally correspond to the long-term glacial-interglacial changes. Rather,it exhibits higher frequency fluctuations without detectable 100 ka period, but with a strong 20 ka period and a clear 40ka period. The combination of 20 ka and 40 ka periods suggest that eolian iron content was relatively independent of glacial-interglacial changes, but more strongly influenced by the insolation changes in the northern hemisphere. Higher iron content was observed for the S5-1 soil that is correlative to marine δ^18O stage 13. In marine records, this stage is characterized by higher δ^13C values, suggesting that the event is of global significance.     

氢致脆化区开裂模型应用于计算门楹值应力强度因子

依据氢进入裂纹尖端区促进局部塑性流动的认识，本建议并发展了一个氢致脆化区开裂模型。首次推导出了确定氢致裂纹扩展门楹值应力强度因子以及环境氢压与门楹值应力强度因子关系的理论公式，定性和定量的分析相符于ＡＩＳＩ４３４０超高强钢的实验结果。     

Effects of applied potential on the stress corrosion cracking behavior of 7003 aluminum alloy in acid and alkaline chloride solutions

Potentiodynamic polarization tests and slow strain rate test (SSRT) in combination with fracture morphology observations were conducted to investigate the stress corrosion cracking (SCC) behavior of 7003 aluminum alloy (AA7003) in acid and alkaline chloride solutions under various applied potentials (E_a). The results show that AA7003 is to a certain extent susceptible to SCC via anodic dissolution (AD) at open-circuit potential (OCP) and is highly susceptible to hydrogen embrittlement (HE) at high negative E_a in the solutions with pH levels of 4 and 11. The susceptibility increases with negative shift in the potential when E_a is less than -1000 mV vs. SCE. However, the susceptibility distinctly decreases because of the inhibition of AD when E_a is equal to -1000 mV vs. SCE. In addition, the SCC susceptibility of AA7003 in the acid chloride solution is higher than that in the alkaline solution at each potential. Moreover, the effect of hydrogen on SCC increases with increasing hydrogen ion concentration.     

Fluorescence study on the interactions of PAMAM dendrimers and their derivatives with bovine serum albumin

The interactions of amino-terminated, and ethylenediamine core poly（amidoamine） （PAMAM） dendrimers and their derivatives with bovine serum albumin （BSA） were investigated by fluorescence spectroscopy. Experimental results showed that the fluorescence intensity of BSA decreased after the addition of different modified dendrimers, and the extent of the fluorescence quenching caused by various modified dendrimers strongly depends upon the different functional groups on their surfaces. We also investigated the influence of pH and ionic strength on the interaction between various modified dendrimers and BSA. Circular dichroism （CD） spectroscopic measurements showed that the content of α-helix structure of BSA decreased after the addition of different modified dendrimers, which indicated that dendrimers induced changes in the secondary structure of BSA.