FY2000 Ground -
based Research
Announcement for
Space Utilization
Research Report

Research Categories
Phase IB Research
Research Fields
Space Utilization Technology Development
Theme
The lubricating properties of graphite fluoride composites under both atmosphere and high vacuum condition
Name
Watanabe Nobuatsu
Organization
Research Institute For Applied Science
Research Term
FY1999`2000
Japanese@


 
The lubricating properties of graphite fluoride composites under both atmosphere and high vacuum condition
 
Watanabe N.P, Hayakawa H.Q, Yoshimoto O.Q, Tojo T.Q,

PResearch Institute For Applied Science
QToyo Tanso co.Ltd.
 
Summary of Research
1)Purpose of Research
It is considered that the properties of solid lubricant of graphite depends on the functional group such as -OH or C=O which exist on the surface of the graphite gallery. In high vacuum such as in space, the water and oxygen does not exist and those groups cannot be existed, the graphite can easily be destroyed by the mechanical friction force, because remaining force for resisting from wear would be only Van der Waals force. On the other hand, graphite fluoride ((CF)n) has fluorine (F) on all carbon bond of the graphite structure and even if the layers are destroyed by friction force, new layers with C-F junction are always developed, and smooth lubrication characteristics would be performed. The binding force of layers of (CF) n is about the half of that of graphite layers, so the (CF) n has better properties for solid lubricant than that of graphite. NASA group was interested in (CF) n, performed various experiments of solid lubricants using (CF) n, graphite, and molybdenum disulfide (MoS2) comparing coefficient of friction under several circumstances and found that (CF) n has the best properties in every conditions. If the graphite fluoride is attached with metal (a reducing agent) in long term, the corrosion will occures. To avoid this corrosion, we found that lithium hydroxide (LiOH) would be the most effective inhibitor to control these phenomena1) and we decided to use LiOH with graphite fluoride. In this research, we tried to find that graphite fluoride composite would be the superior solid lubricant to be used in both in atmosphere and in high vacuum.
2)Experiment Procedure
The test materials are made by adding some amount of solid lubricant such as (CF) n and MoS2 in conventional carbon-graphite solid lubricant composite. The composition of the mixture for test materials and mechanical properties are shown in Tables 1 and 2 respectively.
Table 1 Component of Test Materials Table 2 Mechanical Properties of Test Materials
NAME
Mat' Name
Mixture ratio (%)
(CF)n LiOH MoS2 W1500
2%(CF)n 2 2 |
2%(MoS) | | 2
5%(CF)n 5 5 | 100
5%(MoS) | | 5
2% MIX 2 2 2
5% MIX 5 5 5
cf. W1500:artificial graphite 35%,natural graphite 35%,resin 30%
Mwch.Prop Mat'Name Density(Mg/m3) Hardness(shore D) Bend.Str'th.(MPa) Comp.Str'th(MPa)
W1500 1.77 70 75 175
2%(CF)n 1.77 66 63 138
2%(MoS) 1.8 65 69 167
5%(CF)n 1.74 62 44 124
5%(MoS) 1.83 65 70 160
2% MIX 1.79 65 59 140
5% MIX 1.8 65 54 119
Testing machine for wear and friction under vacuum conditions such as 10-5Pa is designed and fabricated. The schematic drawing is shown in Figure 1. The PV test is performed under the conditions that speed is constant(1750rpm/5.5m/sec)and the load is changed.
3)Test results
@The results of the wear test both in atmosphere and in high vacuum are shown in Figures 1 and 2.
Figure1. Schematic Drawing of Test Machine

In atmosphere the composite which contains(CF) n only has alittle wear loss compared with W1500 without (CF) n, and there is little difference in wear loss compared 2% and 5% content, so the 2% cintent of (CF) n is enough. In other hand MoS2 have small influence to the wear loss. In vacuum, the compounds which contains(CF) n have a lowest wear loss when the amount of content become higher, the wear loss become smaller.

It may be noticed that(CF) n looks excellent soloid lubricant in high vacuum conditions.

4)Publication List:
Tojo,T.,Arai,M.,Miyatani,T.,and Watanabe,N. "Application of Graphite Fluoride"@