STATEMENT OF WORK.pdf

STATEMENT OF WORK

Fabrication and Characterization of Samples of (Gd0.6 Er0.4)NiAl

PR: __4200868156__

Background

NASA/Goddard Space Flight Center is investigating the feasibility of cooling from temperatures as high a 50 K using adiabatic demagnetization. The adiabatic demagnetization refrigerator contains no moving parts as is currently in use to produce temperatures well below 1 K when starting from 4.5 K. Starting from 40 K allows use of radiation to deep space for many missions, removing the vibration of moving parts common to traditional mechanical refrigerators. A high temperature ADR would also eliminate a complete subsystem (the 4.5 K mechanical cryocooler) simplifying and lowering the cost of cryogenic systems for future astrophysics, Earth science, and planetary missions. To demonstrate this at a component level NASA will demonstrate the 4 upper stages of the system using samples of (Gd0.6Er0.4)NiAl.

The compounds of (Gd0.6Er0.4)NiAl has been shown to have favorable properties for providing magnetic refrigeration in this temperature regime. Professor Hadimani at Virginia Commonwealth University has experience producing this material and has the facilities to produce, purify, and measure its magnetocaloric properties.

Please see the detailed proposal from Professor Hadimani attached.

Scope

1. The contractor shall fabricate samples of (Gd1-xErx)NiAl according to the details in the attachment.

2. The contractor shall purify the samples according to the details in the attachment.

3. The contractor shall measure the magnetic properties of a sample as detailed in the attachment.

Requirements

1. The contractor shall provide monthly progress updates over the course of the work via powerpoint slides and remote meetings.

2. The contractor shall deliver the samples and measurement data by the end of the period of performance.

Deliverables or Delivery Schedule

1. Monthly progress reports in the form of a viewgraph package and virtual meetings.

2. Final report include the sample magnetic, magnetocaloric, and optionally resistivity properties of the samples

Government-Furnished Equipment and Government-Furnished Information

No GFE or GFI is provided for this work.

Place of Performance

This work shall be performed at Virginia Commonwealth University

Period of Performance

The period of performance is approximately 6-12 months.

Fabrication and characterization of Gd0.6Er0.4NiAl samples for cooling applications, Duration – 6 months extendable to 12 months.

1. Fabrication of (Gd1-xErx)NiAl samples Twelve polycrystalline samples of Gd0.6Er0.4NiAl with dimensions 20mm diameter and 9mm height will be prepared by drop casting using a water-cooled copper crucible under a Zr-gettered argon atmosphere similar to reported literature [1]. A stoichiometric mass of 99.95% pure Gd and Er, 99.99999% pure Ni, and 99.99999% pure Al will be obtained commercially. Gd, Er, Ni, and Al are put into the crucible together and purged with argon gas several times in order to vent out all the oxygen present in the crucible. The arc is used first to melt gadolinium metal, and the molten metal is allowed to surround erbium, nickel, and aluminum pieces. Once all the constituents are melted, the molten liquid is turned upside down (stirred) several times to ensure the homogeneity of the material. Since the vapor pressure of aluminum and nickel is higher than gadolinium and slightly higher than erbium, a small amount of aluminum is vaporized during the process. In order to account for this loss, 2% more aluminum and nickel will be added. The compositions will be examined using the powder X-ray diffraction (XRD) measurement to ensure the material forms the (Gd1-xErx)NiAl phase. A quick magnetic measurement will be made to confirm the transition temperature between 40-50K.

2. Heat treatment to obtain phase pure samples The as-cast sample will be sealed in an evacuated quartz tube, and annealing will be performed at 800 °C for one week. Microstructure and composition analyses will be carried out using SEM and EDS, respectively. Secondary Electron (SE) detectors and Back Scattered Electron (BSE) detectors will be used during SEM imaging. The composition was determined by energy-dispersive spectroscopy (EDS). XRD will carried out in the PANanalytical equipment with a Cu X-ray tube. The XRD data will be analyzed using X’PERT HIGHSCORE software. The Rietveld diffraction profile fitting technique will be employed to refine the crystal structure by using the Rietica software.

3. Magnetic properties measurements Magnetization measurements will be carried out on a VersaLab Vibrating Sample Magnetometer.

Magnetization vs. temperature will be initially measured at an applied field of 100 Oe (7.9 kA/m) to determine the transition temperature and compare with the published literature. The magnetization and magnetic field at various temperature close to transition temperature will also be measured at an interval of 5K. These MH isotherms may be further used to calculate adiabatic entropy change and compared with adiabatic entropy change calculated from heat capacity measurements.

4. Heat capacity measurements Quantum Design, Dyncool™ Physical Properties Measurement System (PPMS) can perform various physical properties measurements such as heat capacity, electrical resistivity, etc., vs.

magnetic field and temperature. It has a magnetic field range of 9 Tesla, a temperature range of 5 to 400K, and a vacuum of 10-8 Torr can be achieved in the sample chamber, which is necessary for heat capacity measurement. For a detailed description of the system, see reference [2].

In order to measure the heat capacity, the PPMS inputs a certain amount of heat using the platform heating coil in a high vacuum to avoid all the modes of heat transfer processes. It then measures the rise in the temperature of the sample using two platform resistive thermometers. PPMS uses a cryopump to obtain a high vacuum of the order of 10-8 Torr.

Fig. 1 shows the construction of a heat capacity puck. The sample is mounted on a suspended platform in a heat capacity puck using Apiezon grease. The suspension is made of thin wires of platinum gold alloy so that it offers good electrical and poor thermal conduction, as shown in Fig. 1. It can be noted that the platform is suspended from the printed circuit board, which is electrically connected to the pins at the bottom of the puck. The heat capacity puck has a metallic cover to shield the sample from any radiation noise. Heat capacity is measured for the puck alone, and the data is saved as addendum data, after which the heat capacity is recorded by mounting the sample on the platform using Apiezon grease. The heat capacity of the sample is calculated by subtracting the addendum data from the total heat capacity data. Heat capacity is measured first for zero fields and then for various applied magnet fields in the range of 0 to 9 Tesla with an interval of 1 Tesla. For a detailed description of the measurement technique, see reference [3].

Deliverables: 12 polycrystalline samples of Gd0.6Er0.4NiAl having a transition temperature of 40K will be fabricated and delivered to NASA Goddard Space Flight Center by August 31, 2024. The samples’ crystal structure, and magnetic properties will be characterized, including heat capacity from 4.5K to 400K at various applied magnetic fields and data will be provided to the NASA Goddard Space Flight Center.

References:

[1] B. J. Korte, V. K. Pecharsky, and K. A. Gschneidner Jr., “The correlation of the magnetic properties and the magnetocaloric effect in (Gd1−xErx)NiAl alloys,” Journal of Applied Physics, vol. 84, no. 10, pp. 5677–5685, Nov. 1998, doi: 10.1063/1.368830.

[2] Quantum Design, “Dynacool PPMS brochure”, pp. 1-4, https://www.qdusa.com/siteDocs/productBrochures/1307-010.pdf , retrieved, March 2022.

[3] Quantum Design, “PPMS-Advanced Heat Capacity with Helium 3”, retrieved, March 2022, https://www.qdusa.com/siteDocs/productBrochures/1084-500_PPMS_Heat%20Capacity.pdf .

Fig. 1 (a) and (b) Heat capacity pucks showing a suspended platform and the shield. (c) Schematic diagram showing assembly of heat capacity puck [3].