Crystalline composition

In general, hydrated borates of heavy metals ate prepared by mixing aqueous solutions or suspensions of the metal oxides, sulfates, or halides and boric acid or alkali metal borates such as borax. The precipitates formed from basic solutions are often sparingly-soluble amorphous soHds having variable compositions. Crystalline products are generally obtained from slightly acidic solutions. 

Making the flow rate higher or lower will change from stable to metastable the folded or the stretched state, respectively. The effects of hysteresis associated with this first-order discontinuous transition play an important role in the formation of composite crystalline structures. 

Laser ablation of TiC targets was studied by De Maria et al. (1997). TiC films were realized on oriented [111] silicon. During ablation the chamber was kept under a dynamic vacuum (1.5 10 4 Pa) the laser fluence was varied in the range 0-15 J/cm2. Different ablation mechanisms, corresponding to different film characteristics, were observed related to the laser fluence values. At low fluence values (0-3 J/cm2), a film of composition TiC2 was obtained. Films obtained at 3-8 J/cm2 showed a composition close to TiC they had the best characteristics of composition, crystallinity and compactness. 

It is well known that the electrical and optical properties and the performance of the electronic and optoelectronic devices based on inorganic nanostmctured materials critically depend on the composition, crystalline stmcture, and orientation hence, these parameters must be known for nanostmctures integrated into... 

Table 1 - Chemical composition, crystallinity and textural characteristics of zeolite beta samples.

Polymer Filler (%) Processing method Polymer crystallinity, % Composite crystallinity, % Reference... 

These alloys are further on representative for many other systems. The most stable state exists at 25-30 at. % Sn content or at Z = 1.8 e/a, stated above as the ideal amorphous phase. Below this composition, crystalline HR-phases are more favorable and above the ideal positions of the ions within the Friedel minima are lost more and more with consequences on stability. The noble metals have different influences which might be ascribed to the band-gap coefficients 21 v(K) and the structural weights S(Af) close to 2kF. Au-Sn has a compound at x = 50 and therefore a less stable amorphous state in this region [5.58]. 

Table 21.3. Qjmonomer composition, crystallinity, and heat of fusion for P(3HB-3HV) samples...

Variation in the solution pH values was only slight (Table I) the values did not appear to be affected significantly by the precipitation reaction. The precipitates were amorphous and dissolved in IN HCl almost instantaneously no gibbsite or any crystalline phase of aluminum phosphate was observed with x-ray diffraction or electron microscope. No change in composition, crystallinity, and morphology was noticed during aging up to at least six months. 

Chemical composition. Crystalline Structure, Surface Area and Acid-base Properties of MgyAlOx, MgO and AI2O3 Oxides. 

M. Jonoobi, J. Harun, A. Shakeri, M. Misra, and K. Oksmand Chemical composition, crystallinity, and thermal degradation of bleached and unbleached kenaf bast (Hibiscus canna-binus) pulp and nanofibers. BioResources 4,626-639 (2009). 

XRD is a fast and nondestructive test which is frequently used to characterise thermoset materials and their composites. Crystalline materials are characterised by sharp peaks, whereas amorphous materials show broad humps. Thus, the degree of crystallinity can be estimated. When a crystalline material such as clay is dispersed in a thermoset matrix, one can study the intercalation and exfoliation behaviour (see subsequent chapters). If the crystallites of the power are very small, the peaks of the pattern will be broadened. From this broadening one can determine an average crystallite size using the Debye-Scherrer equation ... 

Fracture surfaces, orientation phase composition, crystalline state... 

MOFs have emerged as a novel class of porous solid-state materials with hybrid chemical composition of organic molecules bearing a wide array of functional groups capable of metal coordination and/or chelation and metal ions/clusters. Several attributes of such materials have captured the interest of scientists in academia and industry because of the wide potential applications in current demanding technologies. MOF attributes are directly correlated to the tunable hybrid chemical composition, crystallinity, and modular nature. 

---