Study on Nontraditional Processing Utilizing Microbiogenic Functions

本研究的最终目的是开发利用微生物功能的非传统材料加工。作为研究的第一步，通过对多种金属的腐蚀试验，对海水中微生物腐蚀的一般特征进行了实验研究，并尝试了几种微生物处理方法。研究结果如下：一、微生物腐蚀的一般特征研究(1)证实了大量微生物定向聚集在所有受试金属上，并对其表面和腐蚀产物进行了抑制。(2)阐明了微生物对无氧高纯铜(OFHC)腐蚀的影响；好氧细菌促进了氧化铜的水化；凹坑是由硫酸盐还原细菌(SRB)等厌氧细菌的作用引起的；生成的富氧细胞促进了它们的形成。(3)与无菌条件下的腐蚀相比，在镇静钢的情况下，微生物更倾向于将晶内腐蚀到晶界，从而显著促进腐蚀。II.微生物加工的尝试(1)提出了一种在厌氧细菌作用下在金属表面产生凹形细节的方法，称为MBM凹形工艺，该方法通过制造人工厌氧环境来实现，并被证明是有效的。(2)尝试了一种利用缝隙和微生物腐蚀的联合作用在金属表面产生凸面细节的原理，称为MBM凸面工艺。OFHC表面印有小字，尽管目前还不能令人满意。(3)提出了一种在经过生物处理的衬底上沉积生长金属晶体的工艺，称为MBD工艺。这些结果已在日本中小企业东海分会夏季会议(1992年)上发表，并将在1993年举行的国际研讨会(IMM‘93 Mie)上报告。

A final purpose of the present research is to develop nontraditional materials processing utilizing microbiogenic functions. As the first step for the purpose, general characteristics of microbial corrosion in the seawater were examined experimentally by the corrosion test for various metals, and from the results a few microbiogenic processings were attempted. Results obtained are as follows:I. Study on General Characteristics of Microbial Corrosion (1) It was confirmed that a number of microorganisms gathered orientatively to all the tested metals, and inhavited their surfaces and corrosion products. (2) Microbiological effects on the corrosion of oxygen-free high-purity copper (OFHC) were clarified; aerobic bacteria acted to promote hydration of Cu oxide; pits were caused by action of anaerobic bacteria such as sulfate-reducing bacteria (SRB); resultant oxygen concentration cells assisted their formation. (3) Microoganisms preferred to corrode in-grain to grain boundary in the case of killed steels, and thus promotes markedly corrosion, compared with corrosion under a sterile condition.II. Attempt of Microbiogenic Processing (1) A method to produce concave details on metal surface with the action of anaerobic bacterium, referred to as MBM concave process, was proposed by making artificial anaerobic environment, and was shown to be valid. (2) A principle to produce covex details on metal surface, referred to as MBM convex process, was attempted utilizing the combined action of crevice and microbial corrosions. Small letters were printed on the OFHC surface, although not satisfactory at present. (3) A process to make a metal crystal deposit and grow on the substrate, which was bioprocessed in advance, was presented, and called MBD process. Its validity was confermed by making copper crystals.These results were presented at The JSME Tokai Branch Summer Conference (1992), and are to be reported at the International Seminar (IMM'93 Mie) held in 1993.