High Pressure and High Temperature Equation-of-State of Gamma and Liquid Iron

Chen, George Q.; Ahrens, Thomas J.

doi:10.1557/proc-499-41

Cited by 7 publications

(12 citation statements)

References 26 publications

(38 reference statements)

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“…Using the Ruoff [1967] relations, an isentropic bulk modulus K s of 124.7 (1.1) GPa and pressure derivative of the isentropic modulus of 5.44 (0.06) was obtained. The high‐temperature equation‐of‐state is given in detail in Chen and Ahrens [1998a].…”

Section: Experimental Methods and Resultsmentioning

confidence: 99%

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Phase diagram of iron, revised‐core temperatures

Ahrens

Holland

Chen

2002

Geophysical Research Letters

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Shock‐wave experiments on iron preheated to 1573 K from 14 to 73 GPa, yield sound velocities of the γ‐ and liquid‐phases. Melting is observed in the highest pressure (∼71 ± 2 GPa) experiments at calculated shock temperatures of 2775 ± 160 K. This single crossing of the γ‐liquid boundary agrees with the γ‐iron melting line of Boehler [1993], Saxena et al. [1993], and Jephcoat and Besedin [1997]. This γ‐iron melting curve is ∼300°C lower than that of Shen et al. [1998] at 80 GPa. In agreement with Brown [2001] the discrepancy between the diamond cell melting data and the iron shock temperatures require the occurrence of yet another sub‐solidus phase along the principal Hugoniot at ∼200 GPa. This would reconcile the static and dynamic data for iron's melting curve. Upward pressure and temperature extrapolation of the γ‐iron melting curve to 330 GPa yields 5300 ± 400 K for the inner core‐outer core boundary temperature.

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Section: Experimental Methods and Resultsmentioning

confidence: 99%

“…We believe that this velocity as measured in the 210 GPa to 243 GPa range may represent β‐iron phase. Abbreviations: B & H: Barker and Hollenbach [1974]; B & M: Brown and McQueen [1986] (modified from Chen and Ahrens [1998a]).…”

Section: Resultsmentioning

confidence: 99%

Phase diagram of iron, revised‐core temperatures

Ahrens

Holland

Chen

2002

Geophysical Research Letters

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“…In addition, there is experimental evidence that liquids will move more rapidly than solids during the passage of a shock wave. For example, in a Hugoniot state for a shock wave moving at ~5-6 km/s, molten komatiite (Miller et al 1991), molten fayalite (Chen et al 2003), and molten diopside and molten anorthite (Rigdin et al 1989) travel at speeds of ~1.2-1.6 km/s, whereas solid dunite (Dick et al 1973), solid fayalite (Chen et al 2003), and pure hot γ iron (taenite) (Chen et al 2004) travel at speeds of ~0.2-0.65 km/s. This suggests that there is a fundamental difference between how liquids and solids respond to hypervelocity impacts.…”

Section: Implications For the Iva Parent Bodymentioning

confidence: 99%

Differentiation and evolution of the IVA meteorite parent body: Clues from pyroxene geochemistry in the Steinbach stony-iron meteorite

Ruzicka

Hutson

2006

Meteoritics &Amp; Planetary Science

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Abstract-We analyzed the Steinbach IVA stony-iron meteorite using scanning electron microscopy (SEM), electron microprobe analysis (EMPA), laser ablation inductively-coupled-plasma mass spectroscopy (LA-ICP-MS), and modeling techniques. Different and sometimes adjacent low-Ca pyroxene grains have distinct compositions and evidently crystallized at different stages in a chemically evolving system prior to the solidification of metal and troilite. Early crystallizing pyroxene shows evidence for disequilibrium and formation under conditions of rapid cooling, producing clinobronzite and type 1 pyroxene rich in troilite and other inclusions. Subsequently, type 2 pyroxene crystallized over an extensive fractionation interval. Steinbach probably formed as a cumulate produced by extensive crystal fractionation (~60-70% fractional crystallization) from a high-temperature (~1450-1490 °C) silicate-metallic magma. The inferred composition of the precursor magma is best modeled as having formed by ≥30-50% silicate partial melting of a chondritic protolith. If this protolith was similar to an LL chondrite (as implied by O-isotopic data), then olivine must have separated from the partial melt, and a substantial amount (~53-56%) of FeO must have been reduced in the silicate magma. A model of simultaneous endogenic heating and collisional disruption appears best able to explain the data for Steinbach and other IVA meteorites. Impact disruption occurred while the parent body was substantially molten, causing liquids to separate from solids and oxygen-bearing gas to vent to space, leading to a molten metal-rich body that was smaller than the original parent body and that solidified from the outside in. This model can simultaneously explain the characteristics of both stony-iron and iron IVA meteorites, including the apparent correlation between metal composition and metallographic cooling rate observed for metal.

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“…It was found that the original coil design [2] (using 6 mm (1/4 inch) outer-diameter copper tubing, coil, inner diameter, ~50 mm) was not suitable for high temperature iron experiments in which the sample is 13 mm in diameter and 4 mm thick [1].…”

Section: Coil Designmentioning

confidence: 99%

“…Heating uniformity at high temperature was more critical to the Chen and Ahrens [1] study of the preheated iron equation of state and high pressure and high temperature sound velocity measurement experiments than previous studies [2]. This is because it was necessary to heat solid targets to as close to the melting point as possible in order to lower the shock pressure required to achieve melting.…”

Section: Introductionmentioning

confidence: 98%

Radio Frequency Heating Coils for Shock Wave Experiments

Chen

Ahrens

1997

MRS Proc.

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Radio-frequency eddy current heating of metallic samples in shock wave, ultrasonic and diamond anvil apparatus provides a methodology for obtaining hot samples or hot metallic gaskets (containing a sample) and yet not heating the entire target, ultrasonic assembly or diamond cell. Analysis of a previous design of a radio-frequency (~0.5 MHz) coil demonstrated that the center of 13 mm diameter shock wave experiment sample discs were underheated and the experimental temperatures achieved resulted from conduction of heat from the overheated sample edges relative to the center of the sample. We show, using the Biot-Savant law, that the ratio of magnetic field in the center to that at the edge of the sample, f, can be maximized to a value of f=1.8, by decreasing the radius of the heater coil, relative to the 13 mm diameter of sample. A simple analysis provides the thermal gradient across the sample thickness. An electric skin depth for iron of ~1 mm for the 0.45 MHz frequency of the heater power supply of our system is obtained. This leads to a maximum temperature gradient of ~52 K over the 4 mm thickness of the shock wave sample discs.

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High Pressure and High Temperature Equation-of-State of Gamma and Liquid Iron

Cited by 7 publications

References 26 publications

Phase diagram of iron, revised‐core temperatures

Phase diagram of iron, revised‐core temperatures

Differentiation and evolution of the IVA meteorite parent body: Clues from pyroxene geochemistry in the Steinbach stony-iron meteorite

Radio Frequency Heating Coils for Shock Wave Experiments

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