Kyushu Synchrotron Light Research Center（ Form: No.5）

Experiment Report for Prefectural Beamline
Proposal no. :1406056P
Beamline no.: BL15
Report date : 10/21/2014

Investigation of the Thermal Stability of Graphene in Aluminum
Matrix by In-situ Synchrotron Radiation Diffraction
Ding-Bang Xiong 1 and Di Zhang 1
Shanghai Jiao Tong University, China
Katsuhiko Saito 2 and Qixin Guo 2
Saga University, Japan※１Long term users of Advanced Research User Proposal s are requested to submit thisreport corresponding to each research term (I), (II), or (III), specifying each researchterm at the end of the Report Title.

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1. Summary
The thermal stabilities of graphene oxide (GrO) in both aluminum
matrix composites with and without alumina interfacial layer,
Al-Al 2 O 3 -GrO and Al-GrO, have been characterized by using in-situ
synchrotron radiation diffraction. The results show that GrO is thermallystable in the composite Al-Al 2 O 3 -GrO in which only the crystallization ofamorphous Al 2 O 3 was observed, while aluminum was gradually depleted in
the composite Al-GrO. The depletion of aluminum might be due to thereaction between aluminium and GrO, but phases are complex and no
expected Al 4 C 3 phase can be identified.

２．Purpose of experiment and background
Aluminum and its alloys are one of the most widely used materials as the matrix
in metal matrix composites (MMCs), both in research and development and inindustrial applications.[1] This is mainly due to the low density of aluminum alloys(the first requirement in most applications). Moreover, they are cheap if comparedwith other low density alloys (such as Mg or Ti). Their excellent behaviour, fromdifferent points of view (strength, ductility, corrosion), is very well known and can be
modified in order to satisfy different applications. A major shortcoming of aluminumand its alloy is their low Young’s modulus (~70 GPa), required in most engineering
applications, which could be surmounted by introducing reinforcement.
Graphene, a perfect 2D lattice of sp2-bonded carbon atoms, has recently attracted
tremendous attention in the electronic and composite fields due to its excellent
properties, such as high Young’s modulus (1100 GPa) and high fracture strength (125GPa), extremely high thermal conductivity (5000 W/m·K), super charge-carriers
mobility (200000 cm2/V·s) and so on.[2] The research and development ofgraphene-based composites is an important factor in the practical application ofgraphene. In the past decade, great efforts had been made in graphene/polymer fields(usually graphene oxide (GrO) is used because of its easy preparation), which
immensely improved the mechanical and functional properties of polymer based
composites by incorporating only a small amount of GrO. Recently, our results on GrO
reinforced metal matrix composites have shown notable reinforcement effect ofGrO.[3-4]In the carbon-Al system, an important issue is the chemical stability of carbon in
the Al matrix in fabricating composites at elevated temperatures.[5] In conventional
carbon fiber/Al composites, Al carbide (such as Al4C3) grows on the prism plane of thecarbon fiber. This reaction is serious because the formation of a sharp notch on thefiber by attack of growing Al4C3 needles results in a drastic decrease in the composite
strength. However, the chemical reaction of the newly reported graphene and Al israrely reported before. Therefore, study on the reaction condition and mechanism ofgraphene-Al will provide theoretical guideline for the future researches on thepromising graphene reinforced Al matrix composites.
３．Experimental（Note: Description of sample，method of experiment and analysis,etc.）
The composite of Al-Al2O3-GrO was with a plate-like shape, and was prepared byabsorbing graphene oxide (by Hummers method) onto the surface of Al nano-flakes
with Al2O3 skins, followed by densifying the mixture powder[3-4], while the compositeof Al-GrO was prepared by sputtering Al into the aerogel of GrO. The microstructuresof the two composites are shown in Figure 1.

Figure 1. The microstrues of the composites (Left) Al-Al2O3-GrO (the inset shows a Al2O3-GrO-Al2O3
sandwiched layer) and (Middle) Al-GrO. (Right) The furnace used for heating up in in-situ
experiments

The in-situ synchrotron radiation diffraction experiments were carried out on thebeam line BL15 at Kyushu Synchrotron Light Research Center. The spectra wererecorded in the 2θ range from 15 to 70o at room temperature and then in the range
from 573 to 873 K with an interval of 15 or 20 K (heating rate = 10 K/min). The
averaged time for data collecting is about 150 seconds) and time to heating up is about3~4 min for each spectrum. An Anton Paar DHS 900 furnace was used to heat up thesamples in a vacuumed atmosphere.
４．Results and Discussions

Figure 2. The spectra collected from the in-situ diffraction experiments for the composites of (Left)
Al-Al2O3-GrO and (Right) Al-GrO.

The whole patterns at all elevated temperatures for the composites Al-Al2O3-GrO
and Al-GrO are shown in Figure 2. Four broad peaks located in the 2θ range from 20 to35o were observed in both samples and kept unchanged at all the elevatedtemperature. These peaks could not be indexed by possible phases in the Al-C-Osystem. In the composite Al-Al2O3-GrO, three most strong peaks from right to left canbe attributed to (111), (200) and (220) of aluminum, and their intensities almost kept
unchanged. As shown in the left image of Figure 3, close observation on the peak (111)showed that some small peaks exist on the shoulder, which can be attributed to (311)
and (222) of the gamma-Al2O3 phase. The intensities of these weak peaks increased
with increasing temperature, indicating the gradual crystallization of the amorphous
Al2O3 in the composite. No any new peak appears in the patterns of the composite
Al-Al2O3-GrO at all the elevated temperatures, indicating that GrO separated fromaluminum matrix by the interfacial layer Al2O3 is thermally stable in the composite,at least during the period of two hours for heating up.

Figure 3. The characterized 2θ range reflecting the phases changes in the composites of (Left)
Al-Al2O3-GrO and (Right) Al-GrO.

While the case is completely different in the composite Al-Gr prepared bysputtering. The patterns are more complex than that of Al-Al2O3-GrO. Except for themain peaks from Al, other unidentified peaks also exist. The reason is not so clear
now. One possible reason is the great difference between the amounts of GrO in thetwo composites. GrO is dispersed in aluminum matrix as reinforcement in composite
Al-Al2O3-GrO, while aluminum is sputtered on the surface of GrO aerogel incomposite Al-GrO. However, as shown in the right image of Figure 3, aluminum wasgradually depleted in the composite of Al-GrO. The depletion of aluminum might bedue to the reaction between aluminum and GrO, but the phases of products iscomplex and no expected Al4C3 phase can be identified.
In conclusion, GrO is thermally stable in the composite Al-Al2O3-GrO because of
the existence of Al2O3 barrier layer, but interfacial reaction took place in thecomposite Al-GrO and no Al4C3 phase was observed.
５． Future issues
1.
2.

The unidentified peaks are needed to be confirmed whether from the samples orfrom the measuring system;
Analysis by transmission electron microscope (TEM) is needed to be identified
the interfacial microstructures before and after reaction.

６．References[1]. D.B. Miracle, Composites Science and Technology, 2005, 65, 2526-2540;[2]. K.S. Novoselov, et al, Nature, 2012, 490, 192-200;[3]. J.Y. Wang, Z.Q. Li, et al, Scripta Materialia, 2012, 66, 594–597;[4]. Z. Li, G.L. Fan, et al, Nanotechnology, 2014, 25, 325601;[5]. L.J. Ci, et al, Acta Materialia, 2006, 54, 5367-5375;
７．Publications, patents（Note: Typical deliverables related to this proposal．）

The experimental data obtained in this work will be submitted to an international
scientific journal.
８．Keywords（Note: 2-3 words about samples and experimental methods．）
Aluminum matrix composites; Graphene oxide; Interfacial reaction.
９．About the publication of research results
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