Casting Octahedra for Reproducible Multi-Anvil Experiments by 3D-Printed Molds

Yingxin Liu,Bin Chen,Robert P Rapp,Haijian Li,Xiaojing Lai,Feng Zhu

doi:10.3390/min10010004

Abstract

Making consistent and precise octahedral pressure media is crucial for reproducible high-pressure experiments in the multi-anvil press. Here we report a new approach of casting octahedra using 3D-printed molds, and pressure calibrations for octahedra both with and without pre-existing gaskets (“fins”). The 3D-printed molds for casting octahedra from either Ceramacast 584-OF or 646 cement improve the reproducibility of the octahedra and allow for a pre-existing central hole (for the high-pressure cell assembly) in the final cast product. Pressure and temperature calibrations of the octahedra have been performed based on phase transitions in bismuth (Bi) and silica (SiO2), respectively, in order to determine the efficiency and reproducibility of pressure generation and thermal insulation for cast octahedra designed for use with 18/12, 14/8, and 10/5 multi-anvil assemblies. The pressure-generating efficiency of the 14/8 and 10/5 octahedra with pre-existing gaskets, cast from the 584-OF cement, is similar to that of the corresponding COMPRES (Consortium for Materials Properties Research in Earth Sciences) octahedra, and more efficient than pre-cast octahedra made from the same material but lacking pre-existing gaskets. The efficiency of pre-gasketed 18/12 octahedra made of the 646 cement is markedly lower than those of the 584 cement. However, the 18/12 large-volume octahedra, cast (with fins) from the ZrO2-based 646 cement, also provides efficient thermal insulation. Casting octahedral solid pressure media for multi-anvil experiments using 3D-printed “injection” molds is a low-cost and low failure-rate alternative for conducting reproducible experiments at high pressure in the multi-anvil apparatus.

Highlights

In an effort to replicate in experimental laboratories the often-extreme conditions known to exist within deep interiors of the Earth, other planets, and moons, earth scientists have pioneered many technical developments in the simultaneous generation of high-pressure and high-temperature conditions using various high-pressure devices
One of the most important practical developments was made by Walker [3], who designed and built a removable cylindrical containment ring housing all six of the first-stage anvils as well as the eight carbide cubes of the second stage that enclose the octahedron-shaped pressure medium
We describe a new, low-cost method for casting octahedral pressure-media for multi-anvil experiments from commercially available ceramic cement that makes use of “semi-injection”

Summary

Introduction

In an effort to replicate in experimental laboratories the often-extreme conditions known to exist within deep interiors of the Earth, other planets, and moons, earth scientists have pioneered many technical developments in the simultaneous generation of high-pressure and high-temperature conditions using various high-pressure devices. These efforts have been directed in general towards studying the behavior and chemical and physical properties of planetary materials under appropriate conditions. In addition to dynamic compression techniques, static high-pressure equipment such as the diamond anvil cell (DAC) and the multi-anvil press (MAP) have been used to compress samples to study variations in material properties and polymorphous phase transitions as a function of pressure and temperature. In order to accommodate a larger sample volume, larger carbide cubes (54 and 75 mm) have been used at Bayerisches Geoinstitut [4]

Methods

Results

Conclusion