Powder mixtures components

Liquid-Ph se Sintering. Sintering ia the Hquid state refers to the sintering of a powder mixture of two or more components, of which at least one has a melting temperature lower than the others. The sintering temperature is then selected ia such a manner that a Hquid phase is formed ia which the soHd powder particles of the other components rearrange. A high density powder compact is the result. 

The preferred method for synthesis of complex carbides is the powder metallurgy technique. Hot-pressed powder mixtures must be subjected to prolonged annealing treatments. If low melting or volatile components are present, autoclaves are used. 

In a DTA study [1193] of decomposition reactions in Ag2C03 + CaC03 mixtures, the presence of a response peak, absent on heating the silver salt alone, resulted in the identification of the double salt Ag2C03 2 CaC03, stable at <420 K. One important general consideration which arises from this observation is that the formation of a new phase, by direct interaction between the components of a powder mixture, could easily be overlooked and, in the absence of such information, serious errors could be introduced into attempts to formulate a reaction mechanism from observed kinetic characteristics. Due allowance for this possibility must be included in the interpretation of experimental data. 

The value of p, the linear attenuation coefficient, depends on the substance, its density, and on the wavelength of the x-rays [2]. The mass attenuation coefficient, p., is obtained by dividing p, by the density of the substance. Although a powder mixture may be composed of several components, it can be regarded as being composed of just two components component J (which is the unknown), and the sum of the other components (which is designated as the matrix). The intensity of line i of component J in a powder mixture is given as... 

A.D. Patel, P.E. Luner and M.S. Kemper, Quantitative analysis of polymorphs in binary and multi-component powder mixtures by near-infrared reflectance spectroscopy, Int. J. Pharm. 206, 63-74. Erratum in Int. J. Pharm., 212, 295 (2000). 

Wurster DE, Majuru S, Oh E. Prediction of the Hiestand bonding indices of binary powder mixtures from single-component bonding indices. Pharma Dev Technol 1999 4 65-70. 

The effective medium theory consists in considering the real medium, which is quite complex, as a fictitious model medium (the effective medium) of identical properties. Bruggeman [29] had proposed a relation linking the dielectric permittivity of the medium to the volumetric proportions of each component of the medium, including the air through the porosity of the powder mixture. This formula has been rearranged under a symmetrical form by Landauer (see Eq. (8), where e, is the permittivity of powder / at a dense state, em is the permittivity of the mixture and Pi the volumetric proportion of powder / ) and cited by Guillot [30] as one of the most powerful model. 

In addition to conventional sintering, reactive powder processing, also called combustion synthesis or self-propagating high-temperature synthesis (SHS), can be used if the target compounds can be synthezised from the starting powder mixture (Stangle and Miyamoto, 1995). This process comprises a rapid and exothermic chemical reaction to simultaneously synthesize some or all of the constituent phases in the FGM and density the component. 

Ointments are prepared by melting together the active ingredient with a base, such as petroleum derivative or wax. The powdered drug components are added while stirring and the mixture is cooled. The product then is passed through a roller mill to achieve the particle size range desired for the dispersed solid. 

Podczeck, F. Sharma, M. The influence of particle size and shape of components of binary powder mixtures on the... 

The mixing homogeneity of an interactive mixture is not better compared with a random one, but it leads to an interaction between a fine component and a coarse carrier and then to a higher stability of the system. Pharmaceutical powder mixtures are quite often between a random and an interactive mixture, and... 

Alexander and Klug developed the theoretical basis of the quantitative analyses of powder mixtures. Although a powder mixture may be composed of several components, it can be regarded as being composed... 

Podczeck F. Miah Y. The influence of particle size and sh on the angle of internal friction and the flow factor of unlubricated and lubricated powders. Int J Riarm 1996 144(2) 187-94. Podczeck F, Sharma M. The influence of particle size and shape of components of binary powder mixtures on the maximum volume reduction due to packing. Int J Pharm 1996 137(1 ) 41-7. 

Quantitative XRPD was used to determine the relative component amounts of carbamazepine anhydrate and its dihydrate phase in powdered mixtures of these.22 Each form was characterized by a unique d-spacing (6.78 A or 13.05 degrees 2-0 for the anhydrate, and 9.93 A or 8.90 degrees 2-6 for the dihydrate), as shown in Figure 1, and the ratio of the integrated intensities of these scattering peaks could be correlated to the amount of Form-I in the mixture. In this work, the effects on the results that could be caused by preferred orientation, extinction, and particle size were discussed. 

Duplicate solutions of the pure components and of the powdered mixtures were quickly cooled in liquid air, followed by freeze-drying in a HETO, ED 2.5 for 72 h at 0.07 mbar pressure, at room temperature, and — 40°C condenser temperature to obtain an amorphous state. 

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