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@ARTICLE{Hryha:281358,
      author       = {Hryha, Eduard and Shvab, Ruslan and Bram, Martin and
                      Bitzer, Martin and Nyborg, Lars},
      title        = {{S}urface chemical state of {T}i powders and its alloys:
                      {E}ffect of storage conditions and alloy composition},
      journal      = {Applied surface science},
      volume       = {388},
      number       = {Part A},
      issn         = {0169-4332},
      address      = {Amsterdam},
      publisher    = {Elsevier},
      reportid     = {FZJ-2016-01055},
      pages        = {294},
      year         = {2016},
      abstract     = {High affinity of titanium to oxygen in combination with the
                      high surface area of the powder results in tremendous powder
                      reactivity and almost inevitable presence of passivation
                      oxide film on the powder surface. Oxide film is formed
                      during the short exposure of the powder to the environment
                      at even a trace amount of oxygen. Hence, surface state of
                      the powder determines its usefulness for powder metallurgy
                      processing. Present study is focused on the evaluation of
                      the surface oxide state of the Ti, NiTi and Ti6Al4V powders
                      in as-atomized state and after storage under air or Ar for
                      up to eight years.Powder surface oxide state was studied by
                      X-ray photoelectron spectroscopy (XPS) and high resolution
                      scanning electron microscopy (HR SEM). Results indicate that
                      powder in as-atomized state is covered by homogeneous
                      Ti-oxide layer with the thickness of ∼2.9 nm for Ti,
                      ∼3.2 nm and ∼4.2 nm in case of Ti6Al4V and NiTi powders,
                      respectively. Exposure to the air results in oxide growth of
                      about $30\%$ in case of Ti and only about $10\%$ in case of
                      NiTi and Ti6Al4V. After the storage under the dry air for
                      two years oxide growth of only about $3-4\%$ was detected in
                      case of both, Ti and NiTi powders. NiTi powder, stored under
                      the dry air for eight years, indicates oxide thickness of
                      about 5.3 nm, which is about $30\%$ thicker in comparison
                      with the as-atomized powder. Oxide thickness increase of
                      only $∼15\%$ during the storage for eight years in
                      comparison with the powder, shortly exposed to the air after
                      manufacturing, was detected.Results indicate a high
                      passivation of the Ti, Ti6Al4V and NiTi powder surface by
                      homogeneous layer of Ti-oxide formed even during short
                      exposure of the powder to the air.},
      cin          = {IEK-1},
      ddc          = {670},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000384573100043},
      doi          = {10.1016/j.apsusc.2016.01.046},
      url          = {https://juser.fz-juelich.de/record/281358},
}