New droplet removal polishing method for diamond-like carbon with carbon fiber brush

Motoyuki Murashima, Yusuke Imaizumi, Noritsugu Umehara, Takayuki Tokoroyama

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


In this paper, we propose a new polishing method for diamond-like carbon (DLC) coatings using a carbon fiber brush (CFB). Surface finishing is an important process for DLC coating applications. A lapping process is widely used for attaining tetrahedral amorphous carbon (ta-C) coatings, which are a type of DLC coating containing many droplets, to obtain fine flat surfaces. The lapping process removes protuberant parts of droplets rather than the entire droplet. In this paper, we propose a new polish brush material made of carbon fiber, called CFB. Carbon fiber has both mechanical strength due to its hard carbonaceous material and flexibility due to its fiber structure. In polishing tests, CFB removed droplets from ta-C coatings and the removal effect increased with the shortening of the brush length. The surface profiles of the polished surfaces indicated that a shorter brush length yielded deep scratch marks on ta-C surfaces. Consequently, the arithmetic average surface roughness of the polished ta-C surfaces, Sa, had almost the same value as that of a non-polished surface. Here, we show the ability of CFB to remove the droplets without an increase in the surface roughness. The CFB with the longest brush length in the present study (12 mm) showed a ten-point average roughness SZJI S = 75 nm and Sa = 4.7 nm, which were 59% and 22% lower than those of the non-polished surface, respectively. Furthermore, the longest CFB removed the entire droplets whereas a shorter CFB merely removed the protuberant part of the droplets. The result indicates that CFB polishing can remove entire droplets, which result in abrasive wear or deterioration. From other polishing tests, the optimum polishing distance was determined. Shorter polishing distances could not remove droplets sufficiently whereas longer polishing distances caused deep scratches on ta-C surfaces due to the material transferred to the CFB. Accordingly, the polishing distance of 600 m showed the best surface finishing with SZJI N = 25 nm and Ra = 0.43 nm, which were 86% lower than and similar to those of the non-polished ta-C surface, respectively.

Original languageEnglish
Pages (from-to)190-199
Number of pages10
JournalInternational Journal of Automation Technology
Issue number2
Publication statusPublished - 2020
Externally publishedYes


  • Carbon fiber brush
  • Diamond-like carbon
  • Droplet
  • Polishing
  • Tetrahedral amorphous carbon

ASJC Scopus subject areas

  • Mechanical Engineering
  • Industrial and Manufacturing Engineering


Dive into the research topics of 'New droplet removal polishing method for diamond-like carbon with carbon fiber brush'. Together they form a unique fingerprint.

Cite this