Modelling powders

Important problems ia coUoid scieace remain to be addressed if the poteatial of coUoids is to be fuUy exploited, amoag them, exteasioa of understanding to more coaceatrated suspeasioas, testiag of predictioas usiag model powders, and examination of relaxation phenomena ia ordered coUoids. Much is known about coUoids and their formation and behavior, but considerably more remains unknown. Thus the fuU potential to control coUoids is not presently realized. 

For dissolution of solid particles, the Hixson-Crowell cube-root law (Eq. 5.3) assumes that the thickness of the diffusion layer h is constant during dissolution. However, this is not necessarily true. In addition, most drug particles are nonspherical and nonuniform in size. Therefore, very often the dissolution mechanism of solid drug particles is actually much more complicated. Nevertheless, the Hixson-Crowell cube-root law provides the first approximation to model powder dissolution. 

Wardlaw, N.C. and McKellar, M. (1981) Mercury Porosimetry and the Interpretation of Pore Geometry in Sedimentary Rocks and Artificial Models. Powder Technology 29, 127-143... 

Diemer RB, et al. 2005. Interpretation of size reduction data via moment models. Powder Technol. 156 83-94. 

Arastoopour, H., and Gidaspow, D. Analysis of IGT pneumatic conveying data and fast fluidization using a thermohydrodynamic model, Powder Technology 22, 77 (1979). 

Sacks, M., and Tseng, T., Eheparation of SiOj glass from model powder compacts ... 

In other disciplines, the FE method has been used to model powder compression for a relatively long time, but the first FE analysis of pharmaceutical powder compression appeared in 2002 (56). Since then, the method has been used by a number of researchers... 

Sinka IC, Cunningham JC, Zavaliangos A. The effect of wall friction in the compaction of pharmaceutical tablets with curved faces a validation study of the Dracker-Prager Cap model. Powder Technol 2003 133 33-43. 

M. Alden, P. Torkington, and A.C.R. Strutt, Control and instrumentation of a fluidized-bed drier using the temperature difference technique I. Development of a working model, Powder Tech., 54 15-25,1988. 

Figure 8.5 SAXS patterns of oriented hexagonal morphologies in the system SI52QE516/D4 at 58°C (a) Azimuthally averaged scattering intensity, after background correction for (poA = 0.20 and 0.30 (with factor 10) (b) modeled powder structure factors (2" more likely).

Olmos L, Martin CL, Bouvard D (2009) Sintering of mixtures of powders experiments and modelling. Powder Technol 190 134—140... 

Dry dusts and powders Fine rubber dust, Bakelite modeling powder dust, jute lint, cotton dust, shavings (light), soap dust, leather shavings 2500-3500... 

Benyahia S, Sundaresan S Do we need sub-grid scale corrections for both continuum and discrete gas-particle flow models Powder Technol 220 2-6, 2012. 

Packed-bed micro-reactor model (powdered catalyst)—For both the SCR and the PGM components of the ASC, experimental data collected over the powdered catalysts have been analyzed according to a heterogeneous one-dimensional plug-flow dynamic reactor model that assumes the catalytic bed to be isothermal and isobaric [22]. 

Sanders CFW, Willemse AW, Salman AD, Hounslow MJ. Development of a predictive high-shear granulation model. Powder Technology 2003 138 18-24. 

Kimura T, Horiuchi K, Watanabe T, Matsukata M, Kojima T. Experimental study of gas and particle behavior in the grid zone of a jetting fluidized bed cold model. Powder Technol 82 135-143, 1995. 

Bai DR, Zhu JX, Jin Y, Yu ZQ. Internal recirculation flow structure in vertical upward flowing gas-solid suspensions I, a core/annular model. Powder Technol 85 171-178, 1995. 

Michael D. Sacks and Tseung-Yuen Tseng Preparation of SiO2 glass from model powder compacts. I. Formation and characterization of powders, suspensions, and green compacts, J. Am. Ceram. Soc., 67 (8) (1984) 526-532... 

Dry, R.J. and M.R. Judd, Fluidized Beds of Fine Dense Powders Scale-up and Reactor Modelling. Powder Technol. 

Table 1 Some flexible line-profile funotions Ofx) used to model powder diffraction line profiles (L and G denote the Lorentzian and Gaussian funotions, respectively)...

In low-humidity tetragonal crystal with the partial density of lysozyme of about 0.80 g/cm, approximately 120 water molecules are in the first hydration shell of lysozyme molecule. In order to explore a wide range of hydration level up to monolayer coverage (about 300 water molecules), partial density of lysozyme in powder should be < 0.80 g/cm. In Ref. [401], two models for protein powder were studied densely packed powder with the density of dry protein 0.66 g/cm and loosely packed powder with a density 0.44 g/cm. In loosely packed powder, the percolation transition of water was noticeably (by a factor of two) shifted to higher hydration levels compared with experiment. The fractal dimension of the water network at the percolation threshold as well as other properties evidenced that the percolation transition of water in this model was not two dimensional. The spanning water network consists of the 2D sheets at the protein surface as well as of the 3D water domains, formed due to the capiUaiy condensation of water in hydrophilic cavities. The latter effect causes essential distortion of various distribution functions of water clusters in loosely packed powder. Therefore, below we present an overview of the results obtained for the densely packed model powder. 

P. Hirunsit, Z. Huang, T. Srinophakun, M. Charoenchaitrakool, S. Kawi, Particle formation of ibuprofen-supercritical C02 system from rapid expansion of supercritical solutions (RESS) A mathematical model. Powder Technology 154 (2005), p. 83-94. 

Tsuji Y, Tanaka T, Yonemura S Cluster patterns in circulating fluidized beds predicted by numerical simulation discrete particle model versus two-fluid model. Powder Technol 95 254-264, 1998. http //dx.doi.org/10.1016/S0032-5910(97)03349-4. 

Sacks, M.D. and Tseng, T.Y. Preparation of Silica from Model Powder Compacts I, Formation and Characterization of Powders, Suspensions and Green Compacts, and II Sintering. 0. Amer. Ceram. Soc. 67 [8] 526-637 (1984). 

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