Robert Farla1, Shrikant Bhat1, Eleonora Kulik1, Nico Gaida2

1 DESY, Hamburg, Germany 2 Kiel University, Germany

The 6-ram LVP

Graphite into diamond Pressure generation in sample

Modes of

pressurisation

15 MN Large Volume Press with 6

independently operating rams Company: Max Voggenreiter GmbH Max. oil pressure: 600 bar Max. ram stroke: 100 mm First stage anvils: 60 mm truncation Hardened tool steel or WC core

Assembly configurations – second stage

Anvil materials

In situ X-ray studies at Extreme Conditions using the Large Volume Press.

Cemented Tungsten

Carbide (Tm = 2870 °C) Different fractions of binding elements (Co, Ni) and grain size determines material properties (hardness, toughness, strength, …)

E.g. 6% Co and grain size < 1 µm has a HV of 2040.

6-8 Octahedron

6-6 Cube

Assembly components

Pressure media Heaters Refractory materials

Sample capsule Pt, Re, Mo, Ni, Ta, …

Sample

10 mm (Cr-MgO)

14 mm (Cr-MgO)

18 mm (Cr-MgO)

25 mm (Co-MgO)

20 mm Al2Si4O10(OH)2

Preformed

gaskets Al2Si4O10(OH)2

LaCrO3 Graphite ZrO2 MgO h-BN

Resistive heating

~20 Ohm ~0.03 Ohm

Melting point (At room pressure)

2715 °C 2852 °C 2973 °C

1-5

mm

1-3 mm

Diffracted

X-rays

Typical OCT/TEL ratios:

(in mm)

6-8 geometry – pressure range

25/15, 25/17 0.3 – 5, – 10 GPa

18/11, 18/10 1 – 12 GPa

14/7, 14/8 9 – 16 GPa

10/5, 10/4 14 – 22 GPa

8/3, 7/3 16 – 25 GPa

6/2 up to 35 Gpa

5.7/1.5 up to 45 Gpa

6-6 geometry Pressure generation above 15 GPa has been achieved but very challenging! Less massive support, must rely on compressive strength of anvils alone.

Diamond synthesis in the LVP Typically, diamonds are synthesized at 5 GPa and 1500 °C in a LVP using primary anvils (44 mm TEL) and large cubic assemblies (55 mm) to make cm-sized diamonds!

A possible recipe… High purity graphite powder is used as carbon source. Fe90Ni10 alloy powder (75 µm grain size) is used a solvent/catalyst, containing nitrogen impurity atoms. Mix both at 1:1 ratio by weight for several hours. Then press into a cylindrical disc and boil in a mixture of H2SO4 and HNO3. The sample is ready for diamond synthesis at HP and HT. (Source: Han et al., J. Crystal Growth, 2015)

Sintered and nano-crystalline diamond

anvils Novel anvils for LVP to reach 100 GPa!! But! Extremely brittle, dissipates heat quickly, not electrically conductive, and VERY expensive…

1 cm 1 cm

“HIME-DIA”, GRC, Japan

Thermocouple Type-C W-5%Re – W-26%Re (up to 2300 °C) Type-B Pt-30%Rh – Pt-6%Rh (up to 1700 °C)

Diffracted

X-rays

Before

compression

After

compression

Based on the work of J.M. Zazula, On Graphite Transformations at High Temperature and

Pressure Induced by Absorption of the LHC Beam, 1997