University-industry relationships and open innovation: Towards a research agenda

Accepted versio

In Vitro Bioactivity Study of Pure Wollastonite Prepared from Local Raw Materials

CaSiO₃ ceramics have been proposed as a medical material for artificial bone and dental root, since they proved to be bioactive and biocompatible. In this study, CaSiO₃ powders were synthesized by mixing of Calcium oxide (CaO) and (SiO₂) for 3 h, and subsequent calcination of the mixture at 710°C for 2 h. The compacts were conventionally sintered at 1150°C for 2 h. Moreover, the in vitro bioactivity of wollastonite was investigated by soaking the powders in simulated body fluid (SBF) for various time periods to analyze the nucleation and growth of hydroxyapatite (HA) on the surface of the powders. The obtained results showed that hydroxy-carbonate-apatite (HCA) can be formed on the surface of α-CaSiO₃ particles soaked in SBF solution for 3 days, and a continuous layer of dense deposits of HCA covered the surface of α-CaSiO₃ powders after 15 days of soaking in SBF solution. Besides this, α-CaSiO₃ showed strong hydration when soaked in SBF solution and the hydration was favorable for formation of HCA. Finally, obtained results indicate that α-CaSiO₃ showed to be highly bioactive through the formation of homogeneous apatite layer

Grain Growth in Sintered Natural Hydroxyapatite

Hydroxyapatite (HA: Ca10(PO4)6(OH)2) can be synthesized using several methods or manufactured from natural materials such as coral or bone after removal of the organic matter by heating (denoted as NHA). The in vitro and in vivo studies showed that the natural apatite was well tolerated and has better osteoconductive properties than synthetic HA. In addition, the exploitation of natural source represents an economical way of synthesizing NHA by means of sintering, rather than by sol-gel techniques. For these reasons, the NHA was manufactured from cortical bovine bones in all our studies. Moreover, there has been much effort to improve the mechanical properties of HA by introducing foreign oxides or finding out other alternative processes such as grain growth control. Indeed, encouraging lower AGS instead of exaggerated grain growth may be jugged useful for many applications. Since the works carried out on the correlation between AGS and physico-chemical properties of NHA were very limited, the present study was mainly focused on its grain growth. A carful combination between the main parameters controlling NHA production such as milling techniques, compacting pressure, sintering temperature and holding time may lead to an interesting NHA based bio-ceramics. In this way, a simple and energetically vibratory multidirectional milling system using bimodal distribution of highly resistant ceramics has been used for obtaining sub-micron sized NHA powders. For example, the AGS was ranged between 0.75 and 1.40 µm (using intercept method) when NHA samples were sintered at 1250 C for 15 and 480 min, respectively

Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

Abstract In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide extracted from CaCO3 is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm3). Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy

Mechanical properties of anorthite based ceramics prepared from kaolin DD2 and calcite

Abstract Good quality ceramics costs a lot that has limited their use in developing countries. This work was devoted to prepare low-cost and good quality anorthite based ceramics. The proposed composition was 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide (CaO). The choice of these raw materials was dictated by their natural abundance coupled with a modified milling system, as another interesting advantage. Previous studies have shown that a simple vibratory multidirectional milling system using bimodal distribution of highly resistant ceramic milling elements has been successfully applied for obtaining fine powders. The influence of the relatively lower sintering temperature, ranging from 800 to 1100 °C, on the porosity and the average pore size (APS) have been investigated. The APS and the porosity values of samples sintered at 950 °C were about 1 μm and 4%, respectively. The best Vickers microhardness and 3-point bending strength values for these sintered samples, using this proposed milling system, were 7.1 GPa and 203 MPa, respectively. Finally, the crystalline phase evolution during heat treatment was investigated by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques