Development of a Mg-Based Alloy with a Hydrogen-Storage Capacity of 7 wt% by Adding a Polymer CMC via Transformation-Involving Milling

Song, Myoung Youp; Choi, Eunho; Kwak, Young Jun

doi:2018.56.5.392

Korean Journal of Metals and Materials > Volume 56(5); 2018 > Article

Research Paper

Korean Journal of Metals and Materials 2018;56(5): 392-399. doi: https://doi.org/10.3365/KJMM.2018.56.5.392

Development of a Mg-Based Alloy with a Hydrogen-Storage Capacity of 7 wt% by Adding a Polymer CMC via Transformation-Involving Milling

Myoung Youp Song¹, Eunho Choi², Young Jun Kwak¹

¹Division of Advanced Materials Engineering, Hydrogen & Fuel Cell Research Center, Engineering Research Institute, Chonbuk National University, 567 Baekje-daero Deokjin-gu Jeonju, 54896, Republic of Korea
²Department of Materials Engineering, Graduate School, Chonbuk National University, 567 Baekje-daero Deokjin-gu Jeonju, 54896, Republic of Korea

Correspondence

Myoung Youp Song ,Tel: +82-63-270-2379, Email: songmy@jbnu.ac.kr

Received: 22 January 2018; Accepted: 17 March 2018. Published online: 8 May 2018.

ABSTRACT

The addition of CMC (Carboxymethylcellulose, Sodium Salt) may improve the hydriding and dehydriding properties of Mg since it has a relatively low melting point and the melting of CMC during transformation-involving milling may put the milled samples in good states to absorb and release hydrogen rapidly. Samples with compositions of 95 wt% Mg + 5 wt% CMC (named Mg-5CMC) and 90 wt% Mg + 10 wt% CMC (named Mg-10CMC) were made using transformation-involving milling. Mg-5CMC was activated in about 3 hydriding-dehydriding cycles. After activation, Mg-5CMC had a larger amount of hydrogen absorbed in 60 min, H_a (60 min), than Mg-10CMC and milled Mg. At the fourth cycle (CN=4), Mg-5CMC had a very high beginning hydriding rate (1.45 wt% H/min) and H_a (60 min) (7.38 wt% H), showing that the activated Mg-5CMC has an effective hydrogen-storage capacity of about 7.4 wt% at 593 K in hydrogen of 12 bar at CN=4. Mg-5CMC after transformation-involving milling contained Mg and very small amounts of β-MgH₂ and MgO, and Mg-5CMC dehydrogenated at 593 K in hydrogen of 1.0 bar at the 4^th cycle contained Mg and tiny amounts of β-MgH₂ and MgO, with no evidence of the phases related to CMC. The milling of Mg with CMC in hydrogen is believed to introduce defects and cracks and lessen the particle size. To the best of our knowledge, this study is the first in which a polymer CMC is added to Mg by transformation-involving milling to improve the hydriding and dehydriding properties of Mg.

Keywords: hydrogen absorbing materials, mechanical milling scanning electron microscopy (SEM), X-ray diffraction, a polymer CMC (Carboxymethylcellulose, Sodium Salt) addition.