In an attempt to develop medical
materials, a new design of ester-free
poly(trimethylene carbonate) (PTMC) derivatives incorporating an aromatic
pendant and urea moiety is explored. The aim of the present research
study was to assess whether a flexible, elastic, and degradable PTMC
film can promote the mechanical properties and perform better than
commercially available PTMC. To tune the mechanical and thermal properties,
two kinds of ratio with a cross-linker and a monomer were investigated,
as well as the introduction of urea moieties. Both vinyl benzyl- and
urea-based films showed thermal degradation with 10% weight loss (T
10) of over 200 °C, which suggests the
potential widespread use of the materials at a highly elevated temperature,
such as in sterilization. The chemically modified PTMC films also
have an improved glass transition temperature (T
g) up to 21 °C. Moreover, the incorporation of vinyl benzyl
and the cross-linker markedly enhanced the elongation, tensile strength,
and hydrolysis stability after 90 days. Although the materials showed
slight deformation and stiffness, the urea-functionalized film has
significant effects on the swelling degree. The present research demonstrates
a facile modification approach for the development of ester-free TMC
derivatives.
In this study, microstructural and mechanical properties of the extruded and heat-treated TiNi alloys by sintering the mixture of TiNi pre-mixed powder with titanium dioxide (TiO 2) particles were investigated. Pure Ti and pure Ni powder with TiO 2 particles were mixed and consolidated by spark plasma sintering (SPS). SPSed TiNi alloy compacts were extruded and heat-treated subsequently. SPSed TiNi alloy compacts had TiNi matrix and Ti 4 Ni 2 O phase. Ti 4 Ni 2 O phase was formed during SPS by reaction between TiNi matrix and oxygen atoms originated from additive TiO 2 particles. Consequently, the heat-treated Ti-50.5 at.%Ni alloy using pre-mixed powder with 1.0 vol.% TiO 2 particles showed a high plateau stress of 630 MPa and a good shape recovery of 79.7% in 8% strain applied. The heat-treated TiNi alloy with 1.0 vol.% TiO 2 particles revealed the high strength and good shape memory properties. The high strengthening mechanism of the TiNi alloy using pre-mixed powder with TiO 2 particles was mainly due to a decrease martensitic transformation temperature by an increase soluted Ni content in TiNi matrix after reaction between TiNi and TiO 2 .
In this study, microstructural and mechanical properties of the extruded and heat-treated TiNi alloys by sintering the mixture of TiNi pre-mixed powder with titanium dioxide (TiO 2) particles were investigated. Pure Ti and pure Ni powder with TiO 2 particles were mixed and consolidated by spark plasma sintering (SPS). SPSed TiNi alloy compacts were extruded and heat-treated subsequently. SPSed TiNi alloy compacts had TiNi matrix and Ti 4 Ni 2 O phase. Ti 4 Ni 2 O phase was formed during SPS by reaction between TiNi matrix and oxygen atoms originated from additive TiO 2 particles. Consequently, the heat-treated Ti-50.5 at%Ni alloy using pre-mixed powder with 1.0 vol% TiO 2 particles showed a high plateau stress of 630 MPa and a good shape recovery of 79.7% in 8% strain applied. The heat-treated TiNi alloy with 1.0 vol% TiO 2 particles revealed the high strength and good shape memory properties. The high strengthening mechanism of the TiNi alloy using pre-mixed powder with TiO 2 particles was mainly due to a decrease martensitic transformation temperature by an increase solute Ni content in TiNi matrix after reaction between TiNi and TiO 2 .
The shape memory heat treatment effects on the microstructures and the mechanical properties of TiNi shape memory alloys fabricated by powder metallurgy (PM) process were investigated in this study. Through the optimization of the shape memory heat treatment conditions, PM TiNi alloy showed a high plateau stress of 454 MPa and a good shape recovery of 96.4% in 8% strain applied via the heat treatment at 773 K for 10 min. A longtime heat treatment applied to PM TiNi alloys caused an increase of the amount of Ti 3 Ni 4 precipitates in the TiNi matrix, and led to the relative decrease of Ni solid solution in the matrix which resulted in the decrease of the plateau stress.
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