Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Improvement in corrosion resistance and biocompatibility of AZ31
  magnesium alloy by NH+2 ions   Magnesium alloys have been considered to be favorable biodegradable metallic
materials used in orthopedic and cardiovascular applications. We introduce NH+2
to the AZ31 Mg alloy surface by ion implantation at the energy of 50 KeV with
doses ranging from 1e16 ions/cm2 to 1e17 ions/cm2 to improve its corrosion
resistance and biocompatibility. Surface morphology, mechanical properties,
corrosion behavior and biocompatibility are studied in the experiments. The
analysis confirms that the modified surface with smoothness and hydrophobicity
significantly improves the corrosion resistance and biocompatibility while
maintaining the mechanical property of the alloy.

20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ