Particle composite design

Studies of useful size-dependent properties of nanomaterials are only possible when they are prepared and isolated in a monodisperse form. The synthesis, therefore, should address the need for a great degree of control over the structure, size, and also the composition of the particles. The design of successful synthetic strategies has enabled continuous exploration and exploitation of the unusual properties of nanomaterials that differ both from the single atom (molecule) and the bulk. This also suggests that the intended use of the nanomaterials will dictate the method that can be conveniently applied to obtain them. 

Zeng, Martin, and Marriot also used a central composite design to optimize an albumin microsphere formulation for delivery of tetrandine to the lungs (6). The variables were the pH and the concentrations of albumin and of tetrandine. The level of drug trapped in the microspheres and the diameter of the particles were the selected responses and a quadratic model was determined for each response. 

McLeod et al. optimized the conditions of synthesis of polyglutaraldehyde nanoparticies (7) in terms of 5 factors, monomer and surfactant concentrations, pH, oxygen level, and stirring rate. They used a central composite design, the factorial part of the design being a half fraction factorial of resolution V. Four responses were measured, the most important (the ones that we consider here) being the particle size and yield. 

The catalyst was the reaction product of a Ti compound and MgCl2 in the form of spherical particles with a diameter of 1-100 pm. The high-productivity gas-phase polymerization in MZCR gave multilayered particles with designed chemical composition and MWD... 

Numerous applications have been developed for a wide variety of compounds from different matrices, but surprisingly, only a few reviews dedicated to the extraction of medicinal plants have been pubhshed in the last few years [37-39]. ASE of cocaine and benzoylecgonine from coca leaves has been reported by Brachet et al. [40]. The influence of several extraction parameters such as the nature of the extracting solvent, the addition of alkaline substances, the pressure, the temperature, the extraction time, and the sample granulometry on cocaine recovery was systematically investigated. Methanol was fotmd to be the most suitable solvent. Critical parameters were found to be pressure, temperature, and extraction time. A central composite design has been used to optimize these 3 parameters and to assess the robustness of the extraction method. The optimal conditions for the quantitative extraction of cocaine from leaves were the following 20 MPa, 80 °C, 1 mL min , 10 min extraction time, with a particle size distribution between 90 and 150 pm. 

There are three basic types of engineered composites (1) laminates, (2) particle-reinforced composites, and (3) fiber-reinforced composites. In particle-reinforced composites, one can make the distinction between small (submicron) particle composites, where the particles are incorporated in the microstructure, vs. large particle composites, where the particles themselves actually do the work or carry the load. The reinforcing fibers can be discontinuous or continuous. The fibers in discontinuous fiber-reinforced composites can be randomly oriented to provide isotropic properties or aligned to enhance a specific property in a specific direction. Continuous fiber composites are generally designed for their unidirectional properties but can be crisscrossed to obtain multidirectional property enhancement such as in a filament-woimd pressure container. All possible permutations of metal, ceramic, and pol)uner are foimd in the laminated as well as in the reinforced composites. 

Analysis of a method of maximizing the usefiilness of smaH pilot units in achieving similitude is described in Reference 67. The pilot unit should be designed to produce fully developed large bubbles or slugs as rapidly as possible above the inlet. UsuaHy, the basic reaction conditions of feed composition, temperature, pressure, and catalyst activity are kept constant. Constant catalyst activity usuaHy requires use of the same particle size distribution and therefore constant minimum fluidization velocity which is usuaHy much less than the superficial gas velocity. Mass transport from the bubble by diffusion may be less than by convective exchange between the bubble and the surrounding emulsion phase. 

Saline waters, including seawater, contain, besides a variety of inorganic salts, also organic materials and various particles. They differ in composition from site to site, and also change with time as a result of both natural and human causes. Design and operation of desalination plants requires good knowledge of the saline water composition and properties (41,44). 

---