**7. References**

248 Sintering of Ceramics – New Emerging Techniques

fibroblasts. Analogously, as for fibroblasts, the doubling time was determined for osteoblasts (fig. 20 b). Also in that case, its value showed a relationship with the number of cells on a composite's surfaces, pointing out the best growing conditions in case of W1ssc

• prolonged milling of submicrocrystalline sintered corundum effectively increased the specific surface area of grains from 0.1 m2/g for the sample which was not milled to the value 16.4 m2/g for the sample milled for 30 hours. Particle size distribution after milling for 10, 15, 20, 25 and 30 hours of populative and cumulative curves indicated the multimodal shape with two distinctive ranges of particle size depending on the time of milling. Agglomerated particles were observed after 25 and 30 hours of milling. • X – ray studies revealed the presence of phases α, kappa, δ and Al2O3 and non – stoichiometric composition of magnesium aluminum oxide (Mg0.63Al0.35) (Al1.68Mg0.30)O4 in initial sample. Additionally, in milling samples the silicon dioxide (quartz) coming

from the used agate balls from the planetary mill Pulverisette 6 type appeared. • in the case of glass of calcium – silicon phosphate system prolonged mechanochemical treatment neither had a significant effect on the increase specific surface area (it was only twice after 20 hours milling from 0.9159 m2/g in the starting glass system to 1.9241 m2/g after 20 hours milling), nor on the change of size of glass system grains (from 2.47

• it was found that the phase composition of w1ssc samples (with or without isostatic densification) was identical regardless of the method of manufacturing. It have been identified for w1, w2, w3ssc samples alfa and kappa aluminum oxide and at w1ssc

• observations of biocomposites substrates for scanning electron microscope showed increased porosity in the samples without densification with large number of small pores. Isostatically densified samples had more compact structure, with a small amount

• the difference between total porosity in the samples after isostatic densification and without densification was evident. The samples without densification have a higher porosity with increasing bioglass system A similar trend is maintained in case of isostatically densified composites; with increasing glass content increases the total porosity, apparent and real density decreases. It may be found that the most common

• the analysis of parameters, diagrams and distributions showed significant asymmetry of the distribution in the negative value direction of unevenness for the both cases. It

• the studied composite's surfaces (W1ssc, W2ssc, W3ssc) were characterized by distinct biocompatible properties. The growth of two cell types i.e. fibroblasts and osteoblasts revealed cell – type dependent behaviour.. All substrates without densification seemed to provide better growing conditions for fibroblasts and preosteoblasts while isostatic

surfaces.

**5. Conclusions** 

of larger pores;

Based on studies conducted so far can be stated that:

µm after 5 hours to 1.17 µm after 20 hours).:

anorthit CaAl2 (Si04)2, at w2ssc, w3ssc NaAlSi206 additionally;

pores in all the substrates is far greater than 0,1 micron;

densification induced worser surface properties for cell growth

was bigger for not densified sample.


**12** 

*Pakistan* 

**Synthesis and Sintering Studies of** 

Shahid-Khan Durrani\*, Muhammad-Ashraf Hussain,

**Magnesium Aluminum Silicate Glass Ceramic** 

Khalid Saeed, Syed-Zahid Hussain, Muhammad Arif and Ather Saeed *Materials Division, Directorate of Technology, PINSTECH, P. O. Nilore, Islamabad,* 

Ceramic materials are complex compounds and containing both metallic and non-metallic elements. Typically, ceramics are very hard, brittle, high melting point materials with low electrical and thermal conductivity, good chemical and thermal stability, and high compressive strengths (Barsoum, 1997; Minh et al., 1995). Ceramics are of tremendous interest primarily because of their wide range of applications in high temperature environments; they are also extensively used in fuel technology (Koshiro et al, 1995), oxygen sensor (Ciacchi, et al. 1994), magnets ceramics (Valenzuela,2005) , all electronic equipments including integrated-chips, capacitors and digital alarms (Miller,& M. R. Miller (2002), telecommunication (Bhargava, A.K. 2005), abrasives (Callister, 2007) , ceramic crystal-glass (Carter, & Norton. (2007), ceramic insulators are widely used in the electrical power transmission system (Chowdhury, 2010), ceramic superconductors (David E. C.&, Brece

K.Zoitos, 1992) and other pharmaceuticals industries (Rice, & R. W. Rice, (2002) etc.

ii. Crystalline ceramics**,** which are single phase materials like alumina, or mixtures of such

iii. Bonded ceramics**,** where individual crystals are bonded together by a glassy matrix,

• Simple crystal structures: containing ionic or covalent bonds, or a mixture of the two. Examples are magnesium oxide, which is an ionic compound with cubic structure, and silicon carbide, with covalent bonds and a tetrahedral structure like diamond. Alumina has a close packed hexagonal structure, with a mixture of covalent and ionic bonds,

Ceramic materials can be classified into four main groups (Rajendran, V. 2004):

i. The amorphous ceramics, which are generally referred to as "glasses".

iv. Cements**,** these are crystalline, and also amorphous materials.

The structures of ceramics fall into two main groups:

**1. Introduction** 

materials.

Corresponding Author

 \*

such as clay products.

**1.1 Ceramic materials** 

