AVS 47th International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeP

Paper VT-WeP5
Hydrogen Outgassing from Titanium Modified Layers with Various Surface Treatments

Wednesday, October 4, 2000, 11:00 am, Room Exhibit Hall C & D

Session: Poster Session
Presenter: Y. Mizuno, Nippon Valqua Industries, Ltd, Japan
Authors: Y. Mizuno, Nippon Valqua Industries, Ltd, Japan
A. Tanaka, ULVAC-PHI, Inc., Japan
K. Takahiro, Tohoku University, Japan
T. Takano, Chiba Institute of Technology, Japan
Y. Yamauchi, Chiba Institute of Technology, Japan
T. Okada, Chiba Institute of Technology, Japan
S. Yamaguchi, Chiba Institute of Technology, Japan
T. Homma, Chiba Institute of Technology, Japan
Correspondent: Click to Email
In an extreme high vacuum (XHV) system, hydrogen outgassing is the most important factor to obtain vacuum pressure below 1.0x10@super -10@Pa. Titanium is an interesting material for applications in XHV construction. This work aims to be clear about a correlation between hydrogen outgassing and surface structures of pure titanium in vacuum technology. The titanium surfaces were prepared following treatments such as chemical (CP), electrical (EP), buffing (BP) and mechano-chemical polishing (MCP). Characterization of oxide layers has been carried out using Auger electron spectroscopy and angle-resolved x-ray photoelectron spectroscopy, and a cross section of modified layer has been observed with transmission electron microscopy and an optical microscope for metal/scale. The hydrogen distribution in a surface region was measured by using elastic recoil detection analysis. The oxide thicknesses were from 20 to 50 nm, although the finished titanium surfaces were covered with TiO@sub 2@ for CP, EP, BP and MCP, and also TiO was formed under the top layer for MCP. The thick modified layers (about 1µm) on surfaces were made in BP and MCP processing, and the modified layers had extremely high-density distribution of hydrogen (H/Ti about 1-2). Thermal desorption spectroscopy measurements indicated that the desorption behavior of hydrogen was not strongly depending on the thickness of oxide layer, and the hydrogen outgassing rates were less than 4.0x10@super -7@Pa.m.s@super -1@ at room temperature. We will report the results of the relation between the quantities of desorbed hydrogen gas and the structure of modified layers on titanium polished surfaces.