Particle Surface Characterisation

Strijckmans, K. (1997) Charged particle activation analysis. In Surface Characterisation A Practical Approach, Hellborg, R., Brune, D., Eds., Scandinavian Scientific Press VCH, Weinheim, Germany. 

CPAA measures the characteristic decay radiation of the radionuclides produced by the incident charged particles. The technique has been widely applied in the determination of trace elements concentrations in bulk samples, but it also has possibilities for surface characterisation, provided the thickness of the layer to be characterised is less than the range of the charged particles employed. 

FIGURE 10.11 lUPAC classification of physisorption isotherms. (Following Schoofs, T., Surface area analysis of finely divided and porous solids by gas adsorption measurements, in Particle and Surface Characterisation Methods, R.H. Muller and W. Mehnert, Eds., Medpharm GmbH Scientific, Stuttgart, 1997.)... 

Thorough colloidal/surface characterisation is fundamental to the success of research on polymer colloids. A wide range of complementary techniques are available for colloidal/surface characterisation of polymer colloids and access to several is necessary since no single technique can provide full characterisation. There is an ongoing need for experimental and theoretical work on improvements to existing methods and on development of new techniques to support the needs of research. Additionally, the necessary improvements in process modelling will naturally lead to a demand for advances in on-line analysis to support feedback loops for process control and manufacturing. Thus, further developments in on-line methods for measurement of particle... 

In Eq. (3) the initial reactivity is given by the parameter A . In Eqs. (3-5) the label o refers to the initial charcoal structure which is characterised by the reaction surface area per unit volume, S, the total length of the pore per unit solid volume, Lq, the particle radius, Rg, and the porosity, Cg. The surface reaction is characterised by the reaction rate constant K, and the reaction order n with respect to the reactant gas concentration C, Differentiating Eq. (2) with respect to t for o oo (i.e., the reaction on the outer particle surface is neglected) one obtains... 

NOx defonnation during secondary measures are much more complex dian those of the NOn formation. Not all ways of reactions are known by now. The reactions are di erentiated into two types, the homogeneous and the heterogeneous, which characterise the reactions in the gas phase and the reactions between the gas phase and the particle surfaces. 

The vibrational density of states was calculated for nickel slabs up to 50 layers thick [8], For the first and second layers, the vibrational density of states was different from that of the bulk reflecting their surface configuration. The calculated surface modes for the various surface planes were compared with experiment. The best agreement was for the (111) surface, see Fig. 7.4, evidence for predominant (111) faceting of the micro particles. Although by today s standards the spectra and the fits are poor, the work is of interest as an example of the use of INS in surface characterisation. 

Moaddeb and Koros (1997) described the deposition of silica on polymeric MF membranes as non-uniform. This means that cake characterisation is difficult as a cracks could vary the results. Meagher et al (1996) stated that attractive interaction between membranes and particles would cause a flux decline, even if the particles were aggregated. Aggregation reduced the flux decline if there was no attraction between the membranes and colloids. The authors outlined the restrictions of the gel polarisation model, as the porosity of the deposit is not accounted for in the model. It was also suggested that the resistance of the gel layer is more important than the particle-surface interaction (what is often referred to as adsorption). 

Muller, R.H. Mehnert, W. (1997) Particle and Surface Characterisation Methods (eds R.H. Muller, W. Mehnert G.E. Hildebrand), MedPharm Scientific Publishers, Stuttgart, Germany. 

The structure of the filler particle surfaces and of the polymer surface characterised hy their fractal dimensions, affects the interfacial adhesion in composites. To explain the structural effect let us introduce the concept of the accessibility of the sites on these surfaces to form adhesion joints (physical or chemical). As a first approximation the degree of such accessibility may be defined as a difference of the fractal dimensions of two surfaces. The higher is this difference the lower is the accessibility of the surface and the less is the adhesion [21]. Suppose that the filler particle has a very rough surface with dimensions which are close to the Euclidean dimension d = 3 (for example, AI2O3 particles) [33], whereas the polymer surface is very smooth, i.e., dp = d = 2. In this case the contact between two surfaces is possible only at the apexes of the rough surface of the filler and the result could be very low adhesion. In other words, the disparity of the dimensions determines the inaccessibility of the greater part of the filler particle for the formation of adhesion bonds [21]. 

Strijckmans K (1997) Charged-particle activation analysis. In Brune D, Hellborg R, Whitlow HJ, and Hunderi O (eds.) Surface Characterisation A User s Sourcebook, pp. 169-175. Weinheim Wiley-VCH. 

The objective of this work was to characterise the sodium dodecyl allyl sulphosuccinate (Eliminol JS-2) stabilised poly(butyl acrylate) (PBA) lattices produced in a semibatch reactor. The PBA latex particles were prepared using a semibatch pulsion polymerisation process. It was found that the concentration of JS-2 or sodium dodecyl sulphate present in the initial reactor charge is very important in determining the final latex particle size. The higher the particle size polarity is, the larger is the saturated particle surface area covered by one JS-2 molecule. It was also found that at a common surfactant concentration, the JS-2 stabilised latex displays reduced chemical stability than the sodium dodecyl sulphate stabilised latex. The results of such research should be useful to tape and label manufacturers. 3 refs. 

Important measurands for the characterisation of the EDL are the surface charge density and the electrokinetic potential or zeta-potential. The zeta-potential is the electric potential at a h3q)othetical shear plane, which separates the mobile solvent from solvent molecules that adhere to the particle surface. The zeta-potential can he probed by imposing a relative motion between bulk solvent and particle (Delgado et al. 2007). 

Many macroscopic phenomena of colloidal suspensions arc related to the light scattering and the Brownian motion of the single particles. Both properties depend largely on particle size they are, therefore, frequently employed for the characterisation of particle systems (cf. previous chapter). Additionally, the small size of colloids enhances the significance of the interface to the particles physical behaviour. The interfacial properties additionally affect the interaction between particles and are, thus, cmcial for the macroscopic suspension behaviour (e.g. stability). A particular characteristic of interfaces is the electric double layer (EDL), which camiot be ignored in most situations. Its formation and sttucture is closely related to dissolved ionic species and their interaction with the particle surface (e.g. adsorption, precipitation). Last but not least, the interfacial properties can be affected by the solubility behaviour of the particle phase. 

The correct interpretation of the reinforcing action of the used charges must also take into account their effect on the mobility of chain segments belonging to polymer network. The elastomer layer immobilised on the surface of the black carbon particles is characterised by a higher rigidity and vitreous temperature than that of non-reinforced elastomer. The existence of a such quasi-vitreous... 

While some types of carbon (graphite, diamond) are inert from chemical point of view, the black carbon is characterised by a pronounced reactivity. This one is not only caused by the high specific surface area of the black carbon, but especially by the presence on the particles surface of numerous oxygen containing functional groups of hydroxyl, carbonyl, carboxyl, hydroperoxy, phenol, and quinone type. Finally, the presence of some active hydrogen atoms also contributes to this effect [1203, 1204]. It is known that by... 

K. Strijckmans Charged Particle Activation Analysis", in D. Brune, R. Hellborg, H. J. Whitlow, O. Hun-deri (eds.) Surface Characterisation a User s Source-book. Wiley-VCH, Weinheim 1997, pp. 169-175,... 

Stanley-Wood, N. Sarrafi, M. (1988) Variations in, and relationships of surface area, internal angle of friction and compact diametral fracture strength with degree of compaction. Particle Particle Systems Characterisation, 5(4), 186-192. 

British Standards for Particle, Surface and Pore Characterisation... 

Particle Analysis Particle Size, Particle Shape and Structure and Surface Characterisation... 

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