Microstructure and mechanical properties of Ti6Al4V alloy and sapphire joint brazed with graphene-AgCuTi
MATERIALS RESEARCH EXPRESS
Authors: Fan, Zhou; Zhang, Kun; Liu, Jian-yi; Hu, Min; Yang, Chun-feng
Abstract
The sapphire (alpha-Al2O3) and Ti6Al4V (TC4) alloy was successfully brazed with GNSs (Graphene)-AgCuTi composite filler. The effects of different GNSs content and different brazing temperatures on the interface and mechanical properties of brazed joints were studied. The typical interfacial microstructure of the brazed joint was: Ti6Al4V/Ti2Cu/TiCu/Ti3Cu4/Ag(s.s)/TiC + GNSs /TiCu/Ag(s.s)/Ti3Cu3O/sapphire. The result shows the diffusion layer (I) and Ti-Cu layer (II) got thickened gradually as the brazing temperature rose. At the same time, the thickness of Ti3Cu3O reaction layer increased from 1.9 m to 4.7 m when the brazing temperature increased from 810 degrees C to 870 degrees C. The thermal expansion coefficient of the composite filler and the mechanical properties of the joint were calculated and analyzed. The addition of GNS can reduce the mismatch of thermal expansion coefficient between the brazing joint and Ti3Cu3O reaction layer. When the 0.1 wt% GNSs-AgCuTi composite filler was put into use, the shear strength of the joint reached 29.1 MPa. However, the agglomeration of excess graphene hindered the diffusion of the elements, making the Ti3Cu3O layer discontinuous and causing a mismatch in the coefficient of thermal expansion among the materials, thus reducing the shear strength of the joint.
Preparation of liposomal doxorubicin-graphene nanosheet and evaluation of its in vitro anti-cancer effects
JOURNAL OF LIPOSOME RESEARCH
Authors: Tajvar, Samira; Mohammadi, Soheila; Askari, Alireza; Janfaza, Sajjad; Nikkhah, Maryam; Tamjid, Elnaz; Hosseinkhani, Saman
Abstract
In recent years there has been much interest in development of multifunctional drug delivery systems. In this work, liposomes that contain doxorubicin (Dox), a potent anticancer drug, and graphene nanosheets (GNS) were prepared. The GNSs have excellent optical properties, such as photoluminescence which enables tracking of the liposomes, high absorption in ultra violet region of electromagnetic spectrum which can be exploited in photodynamic and photothermal therapy, and low toxicity to mammalian cells. Nanoliposomes were prepared using the thin film hydration method. Dox and GNSs were loaded to the liposomes during the hydration of the lipid film. Liposomes were characterized and the profile of in vitro drug release, cellular uptake, and cytotoxicity of the prepared liposomes on MCF-7 cells were determined. Despite the earlier reports, the liposomes have kept their spherical structures in the presence of GNSs. The cytotoxicity of liposomal Dox and GNSs were shown to be higher than the free forms of them. Novel nanoliposomes that contain GNSs have provided a multi-functional system with the potential of tracking, photodynamic and photothermal therapy. Further improvements of this versatile nanosystem would be promising for treatment of cancer.