徐乃欣
,
J.L.Dawson
,
G.E.Thompson
,
G.C.Wood
中国腐蚀与防护学报
利用富里叶级数展开作谐波数据处理同样可以同时测定腐蚀体系的瞬时腐蚀速度和塔菲尔斜率。富里叶级数的系数可以用计算机算出。这一方法对于激励正弦波信号的幅值大小没有任何限制。富里叶级数展开法的优点是,在较大的交流激励信号之下,相应的二次和三次谐波成份容易被精确地测出。利用适当的计算机程序,把富里叶级数展开和多元联立方程求解两个子程序结合起来,可以根据实验测得的最初三个谐波成份计算出腐蚀系统的腐蚀电流、阳极塔菲尔斜率和阴极塔菲尔斜率。这些理论考虑用0.5NH_2SO_4中的碳钢作了实验验证。
关键词:
徐乃欣
,
J.L.Dawson
,
G.E.Thopson
,
G.C.Wood
中国腐蚀与防护学报
本文研究了带有阻挡型阳极氧化膜或空气中生成的氧化膜的纯铝浸泡在中性1MNa_2CrO_4/Na_2Cr_2O_7溶液中时的交流阻抗行为。高频下的阻抗数据主要跟膜的介电性质有关,而1Hz以下低频的数据反映了膜上进行的电化学过程。对于空气氧化膜,电化学反应速度逐步变慢,直至达到相应于稳定钝态的恒定值,同时电位向正移动,表明膜中的微裂纹不断得到修补。阳极氧化膜的情况较为复杂。开始时氧化膜比较厚,电化学反应主要局限在微裂纹内,由于阴极反应受抑止,电位变负;随着氧化膜减薄,电位变正,电化学反应速度加快,最后进入稳定钝态。
关键词:
徐乃欣
,
G.E.Thompson
,
J.L.Diwson
,
G.C.Wood
中国腐蚀与防护学报
铝上的阻挡型阳极氧化膜浸泡在不同 pH 的铬酸盐/重铬酸盐溶液中时,膜的电容会不断增大,通常都把这一现象归因于阳极氧化膜的单纯的均匀减薄。然而,本研究表明,在经过这样浸泡的膜的截面超薄切片的透射电镜照片上,膜厚度的减小比由电容数据算出的结果小得多。由这两种方法获得的膜厚数据的明显差异,用膜的简单溶解是无法解释的。它很可能跟铬酸根离子在阳极氧化膜中较复杂的渗透过程有关,渗透了的膜到最终才变得松散而溶解。这一结论得到了俄歇电子能谱分析的佐证,因为在浸泡过的膜的外层发现有铬的存在。
关键词:
徐乃欣
,
J.L.Dawson
,
G.E.Thompson
,
G.C.Wood
中国腐蚀与防护学报
一般的电化学交流阻抗技术只提供跟腐蚀过度成反比的极化电阻,其比例常数须在另外的实验中测定。而交流阻抗测量中同时出现的高次谐波,反映了被测体系的非线性的极化特性。通过谐波分析可以直接求得腐蚀电汽及塔菲尔斜率。本文讨论了通过幂级数展开处理谐波数据的基本关系式。然后选择0.5NH_2SO_4中的碳钢作了实验验证。用带有谐波选择开关的频率响应分析仪测量了前三个谐波成份。测得的数据都修正了溶液的IR降,并从一次谐波中扣去了电容电流。着重讨论了交流信号的频率和幅值的影响。结果表明,谐波分析得到的腐蚀速度跟交流阻抗和失重测量的结果相当符合,同时获得的塔菲尔斜率跟极化曲线塔菲尔区的结果也基本一致。
关键词:
徐源
,
G.E.Thompson
,
G.C.Wood
中国腐蚀与防护学报
用透射电镜、标记原子及等离子体发射光谱定量分析等技术,研究了铝阳极氧化膜生长过程中离子迁移分数及其对膜形态的影响。实验发现,在膜形成过程中,铝和含氧离子沿相反方向漂移穿过膜。在同一电解质溶液中,铝离子的真实迁移分数基本恒定。当电流密度超过某一临界值时,部份铝离子在膜与溶液界面处形成新膜物质,膜的形态为壁垒型。而当电流密度小于临界电流密度时,全部铝离子均进入溶液。这时膜完全由含氧离子在膜与基体界面处形成,由于溶液对膜外表面的侵蚀,形成的膜为多孔型。推导了膜生长效率的理论表达式;表观迁移分数的关系式.用溶解—沉积理论解释了铝离子在膜与溶液界面处形成新膜物质的机理。
关键词:
徐源
,
G.E.Thompson
,
G.C.Wood
中国腐蚀与防护学报
用超薄切片配合透射电子显微镜观察研究了多孔型铝阳极氧化膜孔洞产生及发展的全过程。据此提出孔洞发展过程的几何模型及膜内电场分布的准静电场数学模型。用有限元方法计算了在二维近似条件下孔洞形成各阶段膜内电场的分布,从而确定了电场在孔洞发展过程中的主导作用。讨论了电场作用的机理。
关键词:
International Biodeterioration & Biodegradation
Termites are world-wide pests causing significant losses to annual and perennial crops, as well as damages to wooden components in buildings. Although various chemical, physical, and biological methods have been explored to prevent termite attack on wooden structures, new guiding principles are still needed for environmental protection. In this study, by combining the effective chemical control of bifenthrin and photo-immobilization technique of biomolecules, we developed chitosan as a carrier to embed bifenthrin, which was then immobilized by ultraviolet treatment on the surface of wood (Cunninghamia lanceolata). The immobilized bifenthrin embedded in the photoactive chitosan was characterized by Fourier transform infrared spectroscopy (FTIR), C.H.N analysis, ultraviolet, and fluorescence measurements. The surface structures and biological activity were examined by scanning electron microscopy (SEM), atomic force microscope (AFM), electron spectroscopy for chemical analysis (ESCA), and bioassays. The results indicated that the immobilized bifenthrin can be well protected from free and non-controlled releasing, and has a long-term stability allowing high efficiency against the termite at a dose of 2.5 mu g/cm(2). This study provides a novel and environmentally-benign technique for the termite control by photo-immobilizing the bifenthrin-embedded chitosan on the surface of C. lanceolata. This technique may be used in combination with the traditional methods for effective termite control. (C) 2011 Elsevier Ltd. All rights reserved.
关键词:
Bifenthrin;Chitosan;Immobilize;Cunninghamia lanceolata;Termite;control;surface modification;growth-factor;cell-growth;stem-cells;chitosan;polymer;enantioselectivity;insecticides;cytotoxicity;toxicity
Journal of Porous Materials
Wood and bamboo ceramics are newly developed porous carbon materials from wood and bamboo impregnated with resin, and they possess some special properties and can be expected to be used as electromagnetic materials, absorbents, catalyst carrier materials, etc. In this work, the graphitization behavior of wood and bamboo ceramics was investigated by X-ray diffraction. Experimental results show that the d(002) spacing of the bamboo carbon, wood and bamboo ceramics decreased and the apparent graphite crystallite size Lc((002)) increased with the increase of graphitization temperature. However, even after heat treatment at 3273 K, the d(002) and Lc((002)) value was only about 0.341 and 9 nm, respectively. These results indicate that all of the bamboo carbon, wood and bamboo ceramics investigated are typical non-graphitizable carbon or hard carbon.
关键词:
wood ceramics;bamboo ceramics;graphitization behavior;high;temperature treatment
周光明
,
梁中全
,
赵谦
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2004.05.005
研究了C/G(碳/玻)层内混杂单向复合材料的力学性能,对其拉伸、弯曲、层间剪切、振动阻尼等性能进行了实验研究,并与同样铺层的纯C、G复合材料进行了对比分析.研究表明:C/G层内混杂复合材料可充分利用C、G纤维的各自优点,改善单一材料的模量、强度、断裂韧性、振动阻尼特性等力学性能,模量预测值与实验值较为接近,强度因影响因素较多,二者存在一定的差异,力学性能随C、G体积分数的变化符合混合律,说明了实验方法的合理性.通过C、G相对体积分数的合理设计可满足结构的实际要求.
关键词:
层内混杂
,
复合材料
,
力学性能
,
实验
