Large Particle Composites

Particle-Reinforced Composites—Large-Particle Composites 559... 

Solid particles have a distinct form, which can strongly affect their appearance, product quality and processing behaviour. Thus, in addition to chemical composition, particulate solids have to be additionally characterized by particle size and shape. Furthermore, particles can be generated at any point within the process. For example, nucleation occurs within a crystallization process and large particles are broken down to numerous smaller ones in a comminution process or within a drier. 

The effect of liquid loading was also studied by varying the V content at constant melt composition, i.e. constant ratios of K/V, Na/V, and Cs/V. An example of 1-2 mm large particles depicted in Fig. 11 shows an optimum vanadium content of about 3 wt% for this particular carrier and melt composition. 

One of the most striking lipoprotein abnormalities of familial LCAT deficiency is the presence in the LDL fraction of abnormally large particles, containing variable but unusually great proportions of unesteri-fied cholesterol and lecithin (F6, G14, N5). Recently, an abnormal LDL lipoprotein, identical to cholestatic lipoprotein, LP-X (see Section 8.1) was demonstrated in plasma from patients with familial LCAT deficiency (Ml, T2). Identity of the abnormal LDL lipoprotein and LP-X was shown by electron microscopy, composition, and immunological techniques (T2). The amount of LP-X in plasma of patients with obstructive jaundice ranged from 40 to 1200 mg/100 ml (M3) whereas plasma from patients with familial LCAT deficiency contained 49 to 152 mg/100 ml (T2). 

A "pinwheel" set piece, reflected over water. Cardboard tubes are loaded with spark-producing pyrotechnic composition. The "pin-wheel," attached to a pole, revolves about its axis as hot gases are vented out the end of a "driver" tube to provide thrust. Sparks are produced by the burning of large particles of charcoal or aluminum. (Zambelli Internationale)... 

Only a small fraction of these particles is included in the impactor sample because the cyclone separator removed most particles larger than about 2 urn. The composition of those large particles which were collected by the impactor is that expected for the ash residue. The major species are the oxides of Si,... 

Although a number of filler characteristics influence composite properties, particle size, specific surface area, and surface energetics must again be mentioned here. All three also influence interfacial interactions. In the case of large particles and weak adhesion, the separation of the matrix/ filler interface is easy, debonding takes place under the effect of a small external load. Small particles form aggregates which cause a deterioration in the mechanical properties of the composites. Specific surface area, which depends on the particle size distribution of the filler, determines the size of the contact surface between the polymer and the filler. The size of this surface plays a crucial role in interfacial interactions and the formation of the interphase. 

The data show that the specific activity is generally not a simple function of particle size, confirming the composite nature of the samples. The sharp decrease of the 147Pm specific activities in coral burst samples toward large particle sizes is particularly significant. Systematic differences as a function of yield or soil type between refractory 147Pm behavior and semivolatile 90Sr behavior are not apparent. Uranium behaves very much like "Sr. 

Other approaches have been taken for on-line analysis of individual aerosol particles as well. Laser spark spectroscopy (33) vaporizes individual particles in the breakdown plasma created by a pulsed laser. Atomic emission spectra can then be used to deduce the elemental composition of the particle that was vaporized. The timing of the laser pulse is critical because the particle must be caught in the focal volume of the pulsed laser, so a second laser is used to detect the particle and trigger the pulsed laser. To date the technique has been applied to large particles, that is, coal particles on the order of 60 to 70 xm in diameter in combustion studies. The use of inductively coupled plasma would eliminate the complex triggering and might allow on-line analysis of smaller particles spectroscopically. 

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