author = "Oliveira, Aline Capella de and Reis, Joares Lidovino dos and 
                         Oliveira, Rogerio Moraes and Reis, Danieli Aparecida Pereira",
          affiliation = "{Universidade Federal de S{\~a}o Paulo (UNIFESP)} and 
                         {Universidade Federal de S{\~a}o Paulo (UNIFESP)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Universidade Federal 
                         de S{\~a}o Paulo (UNIFESP)}",
                title = "The Influence of high-temperature nitrogen plasma-based ion 
                         implantation on niobium creep behavior",
              journal = "Advances in Materials Science and Engineering",
                 year = "2020",
               volume = "2020",
                pages = "e9745082",
             abstract = "Niobium has been considered for applications in the aerospace 
                         sector, but its use at high temperatures is restricted, due to the 
                         great affinity of refractory metals with oxygen, which results in 
                         the formation of oxide layers and a decrease in their mechanical 
                         resistances. In the present work, Nb samples were submitted to 
                         High-Temperature Nitrogen Plasma-Based Ion Implantation 
                         (HT-NPBII). The process runs at a working pressure between 3 and 4 
                         mbar and negative high voltage pulses of 7 kV/30 mu s/300 Hz were 
                         applied to samples heated to 1000 degrees C, at treatment times of 
                         1 h, 4 h, and 8 h, respectively. Microstructural and mechanical 
                         characterizations of the treated samples revealed the formation of 
                         a layer of Nb2N, with 3.0 mu m thickness and increase in the 
                         surface hardness from 225 HV for the untreated material up to 
                         about 2498 HV, for samples treated during 8 h. Creep tests were 
                         performed at 500 degrees C and with loads varying from 25 to 40 
                         MPa. Results indicated a decrease in the secondary creep rate for 
                         treated specimens when compared to the untreated ones. This 
                         behavior can be attributed to the formation of a nitride layer on 
                         the surface of Nb that acts as barrier to avoid the oxygen 
                         diffusion into the material under high temperature conditions.",
                  doi = "10.1155/2020/9745082",
                  url = "http://dx.doi.org/10.1155/2020/9745082",
             language = "en",
           targetfile = "oliveira_influence.pdf",
        urlaccessdate = "18 set. 2020"