Aluminosilicates conductivity

The two-layered laser flash method has been applied to some molten systems above 1000 K. In Fig. 30 an example of curve fitting is shown for molten calcium aluminosilicate at 1723 K. An analysis in which the radiative component is taken into account gives a good fit. The thermal conductivity and the radiative component parameter can be determined simultaneously by a curve-fitting procedure. 

Isard, J. O. (1959). Electrical conduction in aluminosilicate glasses. Journal of the Society of Glass Technology, 43, 113-23. 

In a study of dental silicate cements, Kent, Fletcher Wilson (1970) used electron probe analysis to study the fully set material. Their method of sample preparation varied slightly from the general one described above, in that they embedded their set cement in epoxy resin, polished the surface to flatness, and then coated it with a 2-nm carbon layer to provide electrical conductivity. They analysed the various areas of the cement for calcium, silicon, aluminium and phosphorus, and found that the cement comprised a matrix containing phosphorus, aluminium and calcium, but not silicon. The aluminosilicate glass was assumed to develop into a gel which was relatively depleted in calcium. 

Aldol condensation reactions have also been conducted. A good example is provided by Climent et al. (1998) for making a-n-amyl cinnamaldehyde (Jasmin aldehyde) by condensing benzaldehyde with n-heptaldehyde, in the presence of mesoporous MCM-41 aluminosilicates. Mesoporous silica-aluminas with a narrow range of pore diameter such as MCM-41 also... 

The aluminosilicate versions of SSZ-31 and NCL-1 have been prepared with Si/Al ratios from 20 to The borosilicate was most conveniently prepared by using zeolite boron Beta as the source of boron. Recently, it was shown that a sodium borate source could be used with boron Beta seeds if the crystallization was conducted in sealed quartz tubes (39). In related work, a high silica Beta was converted... 

Two methods for including explicit electrostatic interactions are proposed. In the first, and more difficult approach, one would need to conduct extensive quantum mechanical calculations of the potential energy variation between a model surface and one adjacent water molecule using thousands of different geometrical orientations. This approach has been used in a limited fashion to study the interaction potential between water and surface Si-OH groups on aluminosilicates, silicates and zeolites (37-39). 

Fig. 2. Thermal conductivity of refractories where ASF = aluminosilicate fiber and ZF = zirconia fiber. See Table 13 for group classifications (5,25).

Nb-containing MCM-41 sieves represent Lewis acidity proven by FTIR study conducted after pyridine adsorption [3,4], Hydrogen forms of niobium-containing MCM-41 materials exhibit lower Bransted acidity than that in hydrogen aluminosilicate mesoporous molecular sieves (see the band at 1549 cm 1 in Figure 6 [3]). The dehydroxylation of H-NbMCM-41 samples causes the formation of the following lattice species ... 

Organic and polymeric semiconductive materials also show a strong ER effect. They are generally electronic conductive materials with a rr-conjugated bond structure. It is believed that they have better dispersing ability compared to inorganic materials. However, the ER effect of organic and polymeric ER fluids is relatively weak compared to that of aluminosilicate materials. 

Zhang and co-workers reported partial conversion of a mesoporous starting material (SBA-15) into a mesoporous aluminosilicate with zeolitic characteristics in a so-called vapour phase transport method.[82] In this process, Al is firstly introduced onto the mesoporous surface, followed by a filling of the mesopores with a carbonaceous species, and finally a partial recrystallization of aluminosilicate in the vapour of the SDA is conducted. The advantage of this method, compared with the hydrothermal recrystallization method of Kloetstra et al., lies in the fact that the mesopore structure collapses to a lesser extent as the crystallization is limited to the surface of the mesoporous precursor. 

Aluminosilicate zeolites because of their structure, composition, and properties offer a superior ionic strength environment [172,173], Even though these materials are electronic insulators, when hydrated, they are solid solutions of high ionic mobility, and when dehydrated exhibit fair ionic conductivity (see Section 8.2.7) [38,112,119,172], The properties of aluminosilicate zeolites that are responsible for affecting the charge-transfer reactions in electrochemical systems are [172,174] ... 

The effect of intrazeolite protons on pyrrole polymerization in faujasite with ferric ions was examined, in order to distinguish the relative influence of acidity and the one-electron oxidant. If water was co-adsorbed with pyrrole, the authors could prepare materials with conductivities vaiying over a wide range. It is not clear to what extent the conductivity is due to surface-adsorbed polypyrrole, because similar simthetic methods also produced pol)mier coatings on amorphous aluminosilicates. 

A synthetic protocol for the formation of conducting filaments of polyaniline in the 3 nanometer wide channels of the aluminosilicate MCM-41 was developed (Figure 11).1°° Aniline vapor was allowed to diffuse into the dehydrated channels of the host at room temperature, followed by immersion into an aqueous solution of peroxydisulfate at 273 K. This reaction produced encapsulated polyaniline filaments. Spectroscopic evidence including UV-VIS and infrared data showed that the filaments are in the protonated emeraldine salt form (for example, Raman spectra exhibit modes indicative of the protonated quinone radical cation structure). A single, rather broad (8 G) electron spin resonance line (for an evacuated sample), at g = 2.0032 suggested slightly lower... 

Many of the important chemical reactions controlling arsenic partitioning between solid and liquid phases in aquifers occur at particle-water interfaces. Several spectroscopic methods exist to monitor the electronic, vibrational, and other properties of atoms or molecules localized in the interfacial region. These methods provide information on valence, local coordination, protonation, and other properties that is difficult to obtain by other means. This chapter synthesizes recent infrared, x-ray photoelectron, and x-ray absorption spectroscopic studies of arsenic speciation in natural and synthetic solid phases. The local coordination of arsenic in sulfide minerals, in arsenate and arsenite precipitates, in secondary sulfates and carbonates, adsorbed on iron, manganese, and aluminium hydrous oxides, and adsorbed on aluminosilicate clay minerals is summarized. The chapter concludes with a discussion of the implications of these studies (conducted primarily in model systems) for arsenic speciation in aquifer sediments. 

In the early 1980s, Dent Glasser et al. studied aluminosilicate systems with different cations by using 27Al- and 29Si-NMR, light-scattering, and electric-conductance techniques. [40]... 

Polyaniline filaments within the mesoporous channel host (aluminosilicate) have significant conductivity, and this demonstration of conjugated polymer with mobile charge carriers in nanometer channels represents a step toward the design of nanometer electronic devices. These composites have potential as stable molecular wires, which can be applied in the design of batteries and systems to accumulate electric charge. SBA-15 with polyaniline inside the pore channels was used as a dispersed phase in electro-rheological (ER) fluids. 

---