Kinetic and rheological properties ofEarth and planetary materials studied bytime-resolved X-ray diffraction
放射光Ｘ線回折時分割測定を用いた
高温高圧下における地球惑星物質の多結晶カイネティクスとレオロジーの研究
久保友明 、加藤工、西真之、下宿彰
土井菜保子、富永愛子（九州大理）
亀卦川卓美（KEK-PF）
091118

Research interest

極限環境下で様々な時間スケールにおよぶ地球惑星のダイナミックな現象を物質科学（特にカイネティクスとレオロジー）から制約する

Topics• 衝撃隕石中の高温高圧非平衡反応（15-30GPa, 1000-2500K,~0.01-1 secスケール）と衝撃のP-T-t条件の制約• ダイアモンド包有物中の高温高圧非平衡反応（5-15GPa,1000-1500K, 数時間スケール）とダイアモンド上昇履歴• 岩石や氷の高圧相転移と塑性流動特性：地球（ ~ 15-35GPa,1000-3000K）や氷天体（ ~ 2-3GPa, 200-400K）のマントル対流運動（数百万年スケール）の理解
実験手法
高圧実験：（変形）マルチアンビル型装置、DAC
放射光Ｘ線回折時分割測定：エネルギー分散、角度分散２topics（１）Plagioclase breakdown in shocked meteorites
斜長石の非晶質化と高圧相結晶化のカイネティクス
マルチアンビル装置と白色Ｘ線エネルギー分散法によるＸ
線回折時分割測定 (Kubo et al., Nature geoscience, in press)（２）Time-resolved 2D-XRD observations of grain
nucleation and growth during high-pressuretransformations
個々の結晶粒挙動に着目した高圧相転移の核生成ー成長のカイネティクス研究マルチアンビル装置と単色Ｘ線角度分散法によるＸ線回折時分割測定 (久保他, 高圧力の科学と技術 2009; Kubo et al., JPCS in press)

（２）Time-resolved 2D-XRD observations ofgrain nucleation and growthduring high-pressure transformations
The number and intensity of diffracion spots on 2D
detector are used to observe nucleation and growth
kinetics of high-pressure transformations.
Preliminary model experiments on
1.Ice VI-VII and VI-VIII transformations using DAC
2.Coesite-stishovite transformation using the KAWAItype MA apparatus

放射光Ｘ線回折時分割測定による高圧カイネティクス研究
これまでの半導体検出器を用いたエネルギー分散法による相転移カイネティクス時分割測定

圧媒体

２次元検出器を用いた角度分散法による結晶粒カイネティクス時分割測定の試み• 簡便に時分割観察• 多結晶体中の非常に限られた結晶粒の平均情報しか得られない• 細粒多結晶体しか観察できない、高温アニールできない• 核生成律速の相転移の観察などに不向き• 回折に寄与する結晶粒が大幅に増加• 回折斑点に着目することで個々の結晶粒の情報が得られる• 相同定の他に、結晶粒数、結晶粒体積、選択配向、方位関係、応力などの情報を得ることも可能

Kinetic study using time-resolved 2D-XRD method
The number of diffraction spots Ns is proportional to the number of grains Ng(Watching nucleation of new grains)

N s = N g pΔθ cosθ B / 2(cos θ B ≈ 1)
N s ≈ N g pΔθ / 2p

multiplicity factorΔθ angle over which crystal reflects due tovarious factors such as divergence ofbeam
θB Bragg angle(e.g., Hirsch, 1955)

Calibration of the Δθ value ⇒ estimates of the number of nucleated grainsfrom the number of newly appeared spot
The intensity of each spot is proportional to the volume of the grain(Watching growth of individual grains)
Need to make sure “valid reflections”
whether the Bragg reflection is completely recorded on 2D detector

2D-XRD pattern and its azimuthal projection of the intensity
4along Debye ring
3 10(021)

olivine (021) p=4
grain size: 100μm
thickness: 770μm
IP (exp. time 15 min)PF BL14C2 (40 keV)olivine(Mg,Fe)2SiO4incident beam size
500x500 micron
300x300 micron

4intensity

2 1041 10

When increasing the beam size,
1. Newly appeared spots
2. Increases of the intensity
3. No changes (arrowed)
valid reflections
久保他, 高圧力の科学と技術 2009

0050

100

150200azimuth angle

250300Grains corresponding to the arrowed spots
lie completely within the radiated area(300x300).

350

2D-XRD patterns with the sample oscillation
central exposure
from -1° to +1°

8 105
oscillation angle (degree)• The arrowed spots have nointensity left in the additional
exposure.
valid reflectionsintensity

6 105

additional exposure
from -2° to -1°
from +1° to +2°

from -1 to +1
from -2 to -1
from +1 to +2

4 105• The integrated intensity of thearrowed spots is completely
recorded in the central
exposure.

2 105

0050

100

150 200 250
azimuth angle

久保他, 高圧力の科学と技術 2009

300350olivine (130)
grain size: ∼100 μm
thickness: 770 μm
beam size 100 μm
X-ray CCD (exp. time 100sec)
SP-8 BL10XU (35 keV)

2D-XRD observations of partially transformed sample
Fine-grained clinopyroxene (cpx) precipitated at grain boundaries ofparental majoritic garnet (mjgt). These textures are reflected in theazimuthal intensity profiles.
about 20-μm parental majoriticgarnet(p=6)

a few-micron precipitatedclinopyroxene
weak but many peaks(p=4)

Beam size: 100 μm, sample thickness: 120 μm, IP15min@PF-BL14C2 (45 keV)
久保他, 高圧力の科学と技術 2009

Relationships between the number of spots Ns and grains Ng
Preliminary calibration of the Δθ value

N s ≈ N g pΔθ / 2PF BL13A
multipole wiggler
with focusing optics
4.6x10-2• The intercept of each line
indicates the Δθ value.
• The Δθ values are different
among beamlines probably
depending on the light source
SP8 BL04B1
bending magne and focusing optics.

Ns102

2.2x10-3
PF BL14C2
vertical wiggler
3.7x10-3Δθ values (radian)

110102

103

104

Ng p

105

106

standard samples
wadsleyite (ortho.) and alumina (hex.)
Average grain size: 9 and 16 μm
Thickness: 169 and 255 μm
p: 4-12
Incident X-ray
Beam size: 30-300 μm
Energy: 29-50 keV
IP (exp. time 10-15 min)
久保他, 高圧力の科学と技術 2009

Summary (topic 2)• Time-resolved 2D-XRD method has been applied toobserve grain nucleation and growth in high-pressuretransformations using MA and DAC.
• The Δθ values for the relationship between Ng and Ns
were preliminarily determined in some beamlines. We
should consider “valid diffraction spots” in future study.
• We could directly observe the grain nucleation process inthe coesite-stishovite transformation from time evolutionof diffraction spots, which is consistent with the analysisof the bulk transformation rate based on the Avramiequation.