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Its high thermal stability is derived from the lamellar structure, which consists of stacked spinel blocks separated by a monolayer of oxides.
The ionic radius and valency of the A-site cation determine the type of the crystal structure of hexaaluminate (β-alumina or magnetoplumbite).
In order to obtain AAl12O19 hexaaluminate with structure of magnetoplumbite, the theoretic charge of mirror layer cation A must be positive 2.4.
With the increase of Fe3+ ions, α-A12O3 phase was obviously shown in the structure of samples.
That may be due to the broken of structure by introducing much Fe3+.

Popovi� 3 1 Division of Materials Chemistry, Ru#er Boškovi� Institute, P.O.
Introduction Most marine invertebrates build their skeletons of calcium carbonate, adopting a crystalline structure such as calcite or aragonite [1].
We performed a study of chemical composition and structure of sea urchin skeletons in order to gain a better insight into the process of biomineralization.
The Rietveld structure refinement for samples A1-A5 was performed using the structure of calcite reported for the single crystal by Effenberger et al. [11] as a starting model.
The results confirm the calcitetype structure of the samples.

China 2 Department of Chemistry and Engineering Materials, Guilin University of Technology, Guilin 541004, P.
The composition distribution, micro- structure and microhardness of the FGM were analyzed.
The structure of the FGM has graded changes with continuous variation of the composition from one side to the other [2].
The interconnected network structure can be observed and it becomes a matrix phase (Fig.3.d).
The microstructure changes from a network structure into a dispersion composite structure as the content of mullite increases from 5% to 95%.

China 3 Center for Composite Materials and Structures, Science Park of Harbin Institute of Technology, P.O.
A SMP can be a thermo-set with chemically cross-linked structure, or a thermo-plastic with a physically cross-linked network structure.
One major advantage of SMP is that the glass transition temperature can be easily tailored though the control of chemistry and structure, which can meet with various practical requirements[3-4].
Recently, substantial research efforts on SMP are emerging in the areas of biomedical devices, deployable space structures, and micro-systems[5].
Yoon: Smart Materials and Structures Vol.15 (2006), p.1967

In addition, their conduction and valence band potentials are S LaO4 Figure 1 Crystal structure of La2O2S2.
The structure of La2O2S2 is a two-dimensional-like crystal built from layers of squares that are connected by edges.
This layered structure is expected to be advantageous for electron-hole separation.
The XRD pattern of the sample did not change during water splitting, suggesting that water splitting did not affect La2O2S2 crystal structure.
The crystal structure shows short S-S distances in La2O2S2, consistent with the presence of S22− anions [11,12].

The porous materials have attracted considerable interest as an enzyme-immobilization support due to their well ordered structures, large surface areas (up to 1000 m2 g-1), narrow pore size distributions, large pore diameters, and pore volumes [3, 4].
The porous structure allows for higher enzyme loading and creates a protective environment where the enzymes can tolerate more extreme pH, enhanced thermal and environmental stability during catalysis [5, 6].
Briefly; this technique most commonly conducted by intercalation of positive and negative polyelectrolytes, is a powerful, versatile, and simple method for assembling molecular structures [10, 11].
Results and discussion Characterization.A top view of the microspheres with SEM clearly displays the open surface structure of the polymer film with the porous structure (Fig.1).
It can be seen that the as-synthesized PGMA/EDMA-coated chitosan/Fe3O4 microspheres possess porous structure with diameter of 3-3.5 µm.

As we mentioned above, the metamaterial’s EM property could be easily and precisely controlled by changing the geometrical parameters of the periodical structure.
The results indicate that a periodical structure has been formed in the C/SiO2 composite and the EM property of C/SiO2 could be adjusted by controlling the content of carbon.
Compared with the sample prepared by pressure molding, microspheres tightly pack in hexagonal stacking without any damage to form a periodic structure.
Due to the rough surface of the container, however, the structure exist a large number of defects.
Fan, Microwave absorption properties of Fe@Al2O3 nanoembedments prepared by mechanosynthesis, Materials Chemistry and Physics, 130 (2011) 615-618

It can be produced in wide range of densities, crosslink densities and stiffnesses, from very soft to very hard structure.
Cellular Solids: Structure & Properties 2nd Edition,UK, Cambridge University Press
[4] Ionescu, M. 2005.Chemistry and technology of polyols for polyurethane,Rapra Tech Limited, UK
J Composite Structures, Vol 60, pp 385 – 390 [6] Hosur, M.
The low velocity impact response of foam-based sandwich structures.

Synthesis of Straight Rod-Shaped Mesoporous Silica Templated with Polyvinylpyrrolidone and P123 for Controlled Ibuprofen Release Jinyu Zhang1,a, Bin Jiang2,b and Guowei Zhou*1,c 1Key Laboratory of Fine Chemicals in Universities of Shandong, School of Chemistry and Pharmaceutical Engineering, Qilu University of Technology, Jinan 250353, P.
The results indicated that SRMS was straight rod-shaped mesoporous silica with a hexagonal symmetry structure (p6mm) and the structure did not change after functionalization.
Mesoporous silica size, morphology, and structure have been investigated, which significantly influenced its physical and chemical properties.
SRMS was prepared by two structure-directing agents of P123 and PVP with the molar ratio of 1: 0.058.
The result indicated that the hexagonal symmetry structure did not change after functionalization [9], but the structural ordering of NH-SRMS was reduced to a certain extent.

In this context, it is known that the scientific works in this area which are aiming to minimize this spoilage effect, focus on the yogurt structure and packaging of yoghurt.
The reason of this is that the microbial contaminations due to various effects and the factors within its structure.
In line of this consideration, the studies aiming to minimize or remove these effects concentrate on yoghurt structure and its packaging.
Shortly the physical structure of yoghurt is like a network formed by coagulating proteins.
Accordingly, development of current yoghurt packs and PP based materials has been initiated in labs with the help of food, chemistry and material science.