Sharif Digital Repository

Due to the negative effects of conventional plastics on the enviroment, especially in the packaging sector, extensive efforts have been put to replace these polymers with biodegradable polymers. Starch is one of the biodegradable polymers which has attracted a lot of attentions because of low cost and good processability. Native starch has the form of granule and can be processed to a continuous phase after gelatinization in the presence of a plasticizer. The resulting material is a biodegradable plastic-like material called thermoplastic starch (TPS) which is processed using conventional technologies, but suffers from low mechanical properties and high hydrophilicity. Addition of natural... 

In this project ,it has been done different surface treatment on 6 samples of nitinol with 40 % prosity,three of them are anodized by H2SO4 ,Hf, Acetic acid, one of them is treated with plasma spray with TIO2 powder, one of them is putted in the furnace at 700 degrees for an hour, and the last one is bare ; Moreover, these treated samples are putted in Simulated body fluid for 16 days . After this period of time, we analyzed the results. Then the cell adhesion amount of osteo blast cells (MG 63) is measured to these samples by immersing them for 3 days in these cells.The results are investigated by SEM ,XRD(X pertpro produced by Panalitical), XRF(530-XRF-01), AAS( AA240), Roughness measuring... 

Shot peening is a cold-working process commonly used in industry to improve the fatigue performance, stress corrosion resistance and surface nano-crystallization of metallic parts. This process extends fatigue life via two mechanisms: Preventing the crack growth due to compressive residual stresses and, preventing the crack initiation because of increased material hardness. These mechanisms are the results of the bombardment of the component's surface with small spherical particles. In this research, an analytical model is developed for estimating the residual stress distribution induced by shot peening process. The modifications of the developed analytical model are related to... 

According to human needs and in line with the development of advanced technologies, different biomedical Engineering fields like hard tissue implants are growing rapidly. Despite significant biotechnology Developments in recent years, some problems to the recognition of implants related osseointegration phenomena persist. The deficient osseointegration and implant-associated infections are key issues for the long-term clinical success of titanium and titanium alloy implants, while development of multifunctional surfaces that can simultaneously overcome these problems remains highly challenging. Therefore, the ultimate goal of this paper was to improve bone cell attachment and simultaneously... 

Today, pure titanium and its alloys, including Ti-6Al-4V and Ti-6Al-7Nb, are widely used in medicine for manufacturing orthopedic and dental implants, screws and plates for bone fracture fixation, and heart valves. However, due to problems such as low hardness, low wear resistance compared to other alloys such as Co-Cr-Mo alloys, and lack of excellent biocompatibility, surface modification of these alloys is necessary. Also, pure titanium and its alloys are inert materials and after being placed in the body environment, a layer of fibrosis surrounds them and causes them to detach from the host tissue. Therefore, by using surface modification methods, the surface of these materials can be... 

In the preceding years, hydroxyapatite (HA)-based coatings and scaffolds have been known as the best biomaterials for dental and orthopedics applications. Biocompatible and bioactive hydroxyapatite-based Coatings on metallic implants is one of the best methods for reaching both suitable mechanical properties and appropriate bioactivity, leading to better osseointegration and osteoblast proliferation. The ultimate goal of this project is characterization as well as mechanical and electrochemical behavior investigation of Hydroxyapatite- Chitosan nanocomposite coating by electrophoretic deposition (EPD) method on Plasma Electrolyte Oxidation (PEO) treated titanium substrates and Magnesium (Mg)... 

Perovskite solar cells are the new generation of solar cells, and are mainly introduced in two types of structures.1) planer and 2) mesoscopic structure. The difference between these two structures derives from the absence of mesoporous layer in the planer structures. The mesoporous layer acts as an electron transporting layer, and is mainly a titanium dioxide semiconductor. To apply the mesoporous layer, the preparation of the TiO2 paste is needed.The synthesis of titanium dioxide nanopowder for the preparation of TiO2 paste requires high temperature heat treatment and is not desirable in terms of energy consumption.Another weakness of this layer is the presence of surface defects, which...