Calcium titanate effects

MacNevin and Ogle (87) investigated the effects of impurities on the photochromism of barium and calcium titanates as shown in Table V. Pure samples of barium and calcium titanate were not photochromic and doping with Ag+1, Cu+2, Sb+3, Sn+4, Zn+4, and Co+2 produced no enhancement of photochromism. However, increases in the concentrations of impurities such as Fe+3, Zn+2, Sb+5, and V+6 promote photochromic activity. MacNevin and Ogle concluded that the photochromism in these systems depends on the insertion into the lattice of an impurity ion having, (a) an ionic radius near that of Ti+4, and (b) an oxidation number other than 4 to make electron transfer possible. 

The authors [46] investigated the effect of mechanical activation on the synthesis of calcium titanate starting from anhydrous and hydrated calcium and titanium oxides. 

Compounds that have been proposed to react by this mechanism include barium titanate, calcium titanate, calcium carbonate, strontium titanate and magnesium oxides[8,9,10]. All these basic compounds should theoretically react with vanadic acid and bind it in the trap and have proved effective in laboratory evaluations. However, sulfur competition negatively affects the performance of these traps in commercial units[8,l 1],... 

To increase the mixing effects and interaction with the hydroxyl groups, the PEG polymer may be replaced by its monomer, ethylene glycol (EG, 0H(CH2)0H). The EG method also has the advantage of the use of alcohol soluble source chemical such as titanium isopropoxide. Nano-sized titania, calcium titanate [17,18] and barium titanate [9] have been synthesized by the EG method at relatively low organic weight percentages. 

The data shown in Table 2 have been extracted from experimental results of e and as a function of the frequency with typical variations shown in Figures 8 and 9 for various ceramics. In Figure 8 pronounced dipolar relaxations occur for the titanate ceramics such as barium or barium/strontium titanate in the frequency range 10 MHz - 100 GHz. The effective loss factors of these two ceramics at 2.45 GHz are 0.2 and 0.3 respectively indicating that both these materials will readily absorb microwave radiation at this industrial allocated frequency. Lime alumina silicate, steatite and calcium titanate on the other hand have loss factors below 0.02 and as such are not obvious candidates for microwave heating. Figure 10 shows the material properties of a family of ferrites, some types can have extremely high loss factors. 

Various investigations have considered the effects of titanate treatments on melt rheology of filled thermoplastics [17,41]. Figure 10, for example, shows that with polypropylene filled with 50% by weight of calcium carbonate, the inclusion of isopropyl triisostearoyl titanate dispersion aid decreases melt viscosity but increases first normal stress difference. This suggests that the shear flow of the polymer is promoted by the presence of titanate treatment, and is consistent with the view that these additives provide ineffective coupling between filler particles and polymer matrix [42]. 

A synergistic effect on the determination of magnesium is exerted by calcium. Although calcium itself gives no colour reaction with Titan Yellow, its presence with the magnesium causes increased absorbance. Since no further increase occurs above a certain concentration of calcium, the increased absorbance is exploited by adding excess of calcium to the sample and the standard solutions. 

Figure 3.44. Effect of calcium carbonate surface treatment on tensile strength of its composite with PVC containing 25 wt% of calcium carbonate. ST - sodium stearate treated, T - titanate treated. [Data from Sun, S. Li, C. Zhang, L. Du, H. L. ]3umell-Gray, J. S.,Polym. Intern., 55,2,158-164,2006.1...

PP TTS. calcium stearate Titanates proved more effective in improving flow properties and impact strength [46]... 

Surface modifiers can be added to the talc by the talc supplier to improve or reduce various talc-polymer interactions. The choice and concentration of the modifier depends on the desired benefit in the talc composite. Silanes and titanates are used to improve the bond between the talc surface and the polymer. Other surface modifiers, such a glycols and sorbates, are used to improve dispersion of the talc in the polymer. Stearates, such as zinc or calcium stearate, are added to the talc or mixed into the compound to reduce die drool and lubricate die surfaces. Epoxies can be used to minimize interactions between talc and certain stabilizers or metal impurities. These surface-modified talc products are generally more expensive than untreated talc. The decision to use a surface-treated talc is based on cost-performance balance. Sometimes it is more cost-effective to add any additives during the compounding operation than have them added to the talc by the talc supplier. 

Calcium Silicate Bricks. The approved term (replacing sand-lime brick and flint-lime brick) for bricks made by autoclaving a mixture of sand (or crushed siliceous rock) and lime. Requirements and qualities are specified in B.S. 187, and in the USA, in ASTM C73 for calcium silicate facing bricks. Dimensions are specified in BS 4729. Calcium Stannate. CaSn03 sometimes used as an additive to barium titanate bodies, one effect being to lower the Curie temperature. 

The most studied anti-wear material modified by whiskers is PEEK. Wang et al." compared the performances of PEEK before and after modification with potassium titanate whiskers. The friction and wear performances of the latter showed obvious improvement over the former. Under 300 N, the wear resistance of the latter increases 2.64 and 2.11 times than the former, respectively. In addition, calcium carbonate whiskers have an excellent anti-friction effect on PEEK composite material. When the whisker content is less than 15%, the wear rate of the material decreases dramatically. The wear rate of the... 

In addition, different coupling agents have different effects when calcium carbonate whiskers are processed. The impact strength of the composites filled by stearic acid modified calcium carbonate whiskers is better than that of the composite material filled by titanate coupling agent modified whiskers. ... 

Sharma, Y.N., Patel, R.D., Dhimmar, I.H. and Bhardwaj, I.S. (1982) Studies of the effect of titanate coupling agent on the performance of polypropylene-calcium carbonate composite, /. Appl. Polym. Sci., 27, 97-104. 

The wide range of filler types amenable to surface treatment by titanates is of interest. Reaction with fillers containing hydroxyl groups would be anticipated, but their effective application to calcium carbonate is more surprising. It has been suggested that free acid, present in the titanates as impurity, or produced by hydrolysis, may contribute to the reaction. 

A fourfold increase in notched Izod impact strength has been reported with 1.5% titanate used as a coating for calcium carbonate in linear low density polyethylene, as shown in Figure 5, which illustrates the effect of two different proprietary titanate coatings. 

Because of the instability of titanium to carbon bonds, any reactive functionality has to be attached through oxygen and even then, stability cannot be guaranteed. Many of the products available have long-chain hydrocarbon functionalities, and while they produce useful effects, these are more likely to arise from dispersion rather than coupling in the sense used in this chapter. The titanates appear to be effective with fillers such as calcium carbonate and carbon black, where it is difficult to envisage surface reaction mechanisms and weaker, dispersant-type interactions are more likely. 

Titanium dioxide is by far the most effective white pigment a compounder can use in a rubber compound. It has superior opacity, brightness, and hiding power over all other white pigments or fillers. However, it is also more expensive than other white fillers such as special water-washed clays, calcium carbonate, and talcs. Occasionally, organo-titanates are used in rubber formulations to improve filler dispersion, that is, the compound s rheology. 

All other conditions being fixed, the only way of increasing the ceramic resistivity is to use substitutions. Chilton has substituted uranium into calcium-doped lead titanate to produce an increase in resistivity by approximately one order of magnitude (Fig. 6.9). It can be seen that the resistivity increases, with a maximum around 1.0 mol%. This variation is explained by considering the ceramic as a p-type semiconductor. The uranium will act as a donor of electrons, and as the amount of uranium increases, the initial effect is to cancel out the majority carriers (holes). 

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