Aluminate base

CeMgAljjOjgi. The first triphosphor lamps were made possible with the discovery of this phosphor and the class of aluminate-based... 

Granulation. Before alumination — based on a selective sedimentation test, the phosphorus shall contain a max of 3% of particles of less than 10 microns in diameter. After alumination the powder shall pass thru the following sieves ... 

The aluminate-based admixtures undoubtedly provide the best wet-mix shotcrete, making it possible to build thick linings even in overhead work. The high alkali content and the consequent health hazard are the main constraints to their more widespread use. Furthermore, there is concern that the admixture may promote the alkali-aggregate reaction in concretes containing reactive aggregates, as well as sulfate attack [117]. 

The chemical composition of these accelerators is neither described in the pertinent bibliography nor divulged by their producers. They have a pH between 3 and 5.5 and an alkali content of less than 0.3% and are used in amounts between 3 and 10% by weight of cement. When used in adequate amounts, they allow overhead buildup in linings of up to 300 mm thick. An important characteristic of these accelerators is that the latter-age strengths are not reduced when compared with a reference material (without accelerator) [108], For example, in the construction of the tunnels of the south freeway (Via Express Sul) in Florianopolis, Brazil, comparative tests were made with an alkali-free liquid accelerator and the sodium-aluminate-based accelerator. The aluminate-based accelerator was added in an amount... 

Fig. 6.21 Comparison between the performance of shotcrete with alkali-free and sodium-aluminate-based accelerators (Prudencio [108]).

Figure 7.25 Backscattcrcd electron image. General view of a Zn aluminate-based catalyst.

E.V. Uhlmann, et al., Spectroscopic properties of rare-earth-doped calcium-aluminate-based... 

Y.W. Lee, et al., Study on the mechanical properties and thermal conductivity of silicon carbide-, zirconia- and magnesia aluminate-based simulated inert matrix nuclear fuel materials after cyclic thermal shock../. Nucl. Mater. 319, 15-23 (2003). 

The main drawback with the use of perovskites is the poor thermal stability of the materials compared with hexa-aluminate based catalysts. Zwinkels et al. have compared the thermal stability of two different hexa-aluminates with a SrZr03-perovskite, a pyrochlore, see Section 3.2.4, and two spinels, see Section 3.2.3. The perovskite, as well as the pyrochlore and one of the spinels decreased in their surface area significantly. One of the explanations of the much lower stability of the perovskites compared with the hexa-aluminates is that the crystal growth will take place in three dimensions and thereby yield a material with a low surface area. Lowe et al. have studied several different perovskites and their thermal stability and conclude that the surface area of the perovskites is not sufficient for use in high temperature catalytic combustion. Similar results have been shown by Cristiani et al. ... 

A totally different activity trend with respect to catalyst ligation is observed when the sterically encumbered aluminate-based activator PhsC PBA ... 

High alumina cements are calcium-aluminate based materials, without free lime. 

The CBBCs including Ca-aluminate based biomaterials can be produced at low temperatures in-situ, in vivo. The chemistry of these systems is similar to that of hard tissue in living organisms. The CBBCs easily form nanostructures with crystal sizes similar to those found in hard tissue. Both stable and resorbable CBBCs can be produced. The stable phases are found within the Ca0-Al203-H2O and Ca0-Si02-H20 systems, while resoibable phases are seen within the Ca0-P205-H20 system and within sulphate systems. 

Due to a low solubility product of the phases formed, nanocrystals are easily formed, and it is difficult to avoid the nanostmctural features. The nanocrystal size is often in the range 10-40 nm with an open porosity with a nano-channel width in the range 1-3 nm [2, 9]. General properties of Ca-aluminate based biomaterials due to the nanostructures developed deal mainly with... 

General properties for Ca-aluminate based biomaterials are presented as [2],... 

The Ca-aluminate based biomaterials include apatite, the main chemical constituent in hard tissue... 

The thermal and electrical properties of Ca-aluminate based biomaterialss are close to those of hard tissue. 

Additives for chemically bonded bioceramics, CBBCs, including Ca-aluminate based materials [10-12] are introduced to promote ... 

The CBBCs can be divided into two main groups resoibable and stable biomaterials. Ca-aluminate based biomaterials and to some extent Ca-sihcates are stable materials after hydration, and can favorably be used for load-bearing applications. The Ca-phosphates, Ca-sulphates and Ca-carbonates are known to be resorbable or slowly resorbable when inserted in the body, and their main applications are within bone void filUng with low mechanical stress upon the biomaterial. The resorbable materials are after various time depending on the specific chemical composition replaced by new bone tissue. This can start immediately after injection and the material can be completely dissolved after months and in some cases after a few years. 

The nanostmetures observed in Ca-aluminate and Ca-silicate system confirm a typical size in the interval 10-40 run. Even the tooth structure in details reveals the individual crystals of the size of approximately 20 run [1,16], Bone ingrowth towards the apatite formed in Ca-aluminate biomaterials allows the new bone structure to come in integrated contact with the biomaterial. The transition from tissue to the biomaterial is smooth and intricate [17], For an experimental Ca-aluminate based system the ingrowth is shown in Figure 3. 

Figure 5. Nanostmcmral integration of Ca-aluminate based hiomaterial with dentine (gray particles in the hiomaterial are glass particles)...

Table II. Mechanical property data of an experimental dental Ca-aluminate based material...

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