Liquid/powder ratio

Critical Binder Liquid/Powder Ratio. When a liquid is mixed into a bulk powder made of fine particles, the liquid distributes itself first into small spaces between particles forming liquid bridges as can be seen in Fig. 12a. For very small amounts of liquid, these bridges are randomly spaced and do not influence the bulk properties of the powder. Upon introduction of larger... 

The liquid/powder ratio (L/P) is an important aspect of the cement that affects the workability and the injectability of the paste. Generally, low L/P ratio s cause flowable and viscous pastes, while liquid deprivation reduces the injectability of the paste. On the other hand, excess aqueous solution is often associated with the phenomenon of filter-pressing, which implies that the liquid flows faster than the ceramic particles (Bohner et al. 2010). Although liquid films surrounding the particles keep the particles separated, improve the fluidity and allow injection by minimally invasive techniques, the final setting time of the cement increases due to delayed crystallization, which causes a weaker structure due to a high micro and nanoporosity in the final cement (Ginebra et al. 2004 Espanol et al. 2009). 

Concrete nominally contains 1 part phosphate solution, 1 part magnesia and 4 parts dolomite. Setting usually occurs in less than 30 minutes and up to 50 MPa compressive strength is developed within 4 hours. Factors affecting strength development are the particle size of the wollastonite, the P2O5 content of the liquid, and the liquid/powder ratio. 

Table 3. Critical Binder/Powder Ratios for Some Selected Powder-Liquid Systems...

It will be assumed for the present considerations that sufficient binder is present in the granulator as determined by the binder/powder ratio and that the binder is appropriately spread on enough granular surfaces so as to ensure that most random collisions between particles will occur on binder-covered areas. It will also be assumed that the particles are more or less spherical having a characteristic dimension, a. The simplified system of two colliding particles is schematically shown in Fig. 21. The thickness of the liquid layer is taken to be h, while the liquid is characterized by its surface tension yand its viscosity /x. The relative velocity U0 is taken to be only the normal component between particles while the tangential component is neglected. 

Rotary wheel atomizers require 0.8 to 1.0 kWh/1000 L. The lateral throw of a spray wheel requires a large diameter to prevent accumulation on the wall the ratio of length to diameter of 0.5 to 1.0 is in use in such cases. The downward throw of spray nozzles permits smaller diameters but greater depths LID ratios of 4 to 5 or more are used. Spray vessel diameters of 15 m (50 ft) or more are known. Liquid/gas ratios are 0.2 to 0.3 gal/MSCF. Flue gas enters at 149°C (300°F) at a velocity of 2.44 m/s (8 ft/s). Utilization of 80 percent of the solid reagent may be approached. Residence times are 10 to 12 s. At the outlet the particles are made just dry enough to keep from sticking to the wall, and the gas is within 11 to 28°C (20 to 50°F) of saturation. The fine powder is recovered with fabric filters. In one test facility, a gas with 4000 ppm S02 had 95 percent removal with lime and 75 percent removal with limestone. 

Europe the use of sludge hardeners of type 2 above is fairly common too. When using a powder hardener in adhesives of types 1, 2, and 3, they are mixed before use in a mass/ mass ratio of liquid adhesive resin (50-60% solid content) to powder hardener of 5 1. The powder hardener is generally a mixture of 10 parts paraformaldehyde and 10% fillers. It is comprised of 200-mesh wood flour or a mixture of wood flour and nutshell flour, also 200 mesh. Adhesives of types 4 and 5 have a liquid resin to liquid hardener ratio of 1 1 by mass. This is so because the hardener is also a resin. Adhesives of types 4 and 5 have been used quite extensively in the past in certain markets but have now been superseded by adhesives of type 2 which have several handling advantages. 

The dissolution behavior of HA in an aqueous medium and subsequent biological reactions also depend on the chemical composition of the crystal. Ion exchange occurring at the apatite surface depends on (1) the rate of formation and dissolution of the various phases, (2) the powder-weight-to-liquid-volume ratio, (3) pH, (4) specific surface area, (5) crystal defects, impurities, and vacancies, and (6) substitutional ions. 

Inorganic cements (inorganic binders) are powdered materials that, if allowed to react with a suitable liquid phase (usually water or a water solution of an appropriate reactant), undergo chemical reactions associated— at an appropriate liquid/solid ratio— with the formation of a firm solid stracture. 

Pina, S., Olhero, S. M., Gheduzzi, S., Miles, A. Q., and Ferreira, J. M. F. 2009. Influence of setting Uquid composition and liquid-to-powder ratio on properties of a Mg-substituted calcium phosphate cement. Acta Biomaterialia 5 1233-40. 

Amount of material required. It is convenient to employ an arbitrary ratio of 0 10 g. of solid or 0 20 ml. of liquid for 3 0 ml. of solvent. Weigh out 0 10 g. of the finely-powdered solid to the nearest 0 01 g. after some experience, subsequent tests with the same compound may be estimated by eye. Measure out 0-20 ml. of the liquid either with a calibrated dropper (Fig. 11,27, 1) or a small graduated pipette. Use either a calibrated dropper or a graduated pipette to deliver 3 0 ml. of solvent. Rinse the delivery pipette with alcohol, followed by ether each time that it is used. 

The hydrocarbon can be in either the liquid or vapour phase and the silicon is finely divided. The inclusion of certain solid catalysts in the reactive mass may in some instances greatly facilitate the reaction. A mixture of powdered silicon and copper in the ratio 90 10 is used in the manufacture of alkyl chlorosilanes. 

For the n-Cq reforming and n-C[2 isomerization reactions the catalysts were run in a fixed bed micro reactor equipped with on-line GC analysis. The catalyst, together with a quartz powder diluent, was added to a 6 inch reactor bed. A thermocouple was inserted into the center of the bed. The catalysts were calcined at 350-500°C immediately prior to use and reduced in H2 at 350-500°C for 1 hour. n-Heptane or dodecane (Fluka, puriss grade) were introduced via a liquid feed pump. The mns were made at 100-175 psi with a H2/n-heptane (or n-Ci2) feed ratio of 7 and a weight hourly space velocity of 6-11. 

An unfortunate characteristic of early zinc polycarboxylate cements was the early development of elastomeric characteristics- cobwebbing -in the cement pastes as they aged, thus shortening working time (McLean, 1972). Improvements in cement formulation, the addition of stannous fluoride to the oxide powder (Foster Dovey, 1974, 1976) and modifications in the polyacid have eliminated this defect. However, the cements have to be mixed at quite a low powder/liquid ratio, 1 -5 1 0 by mass, when used for luting. 

Attempts have been made to improve the mechanical properties of these cements by adding reinforcing fillers (Lawrence Smith, 1973 Brown Combe, 1973 Barton et al, 1975). Lawrence Smith (1973) examined alumina, stainless steel fibre, zinc silicate and zinc phosphate. The most effective filler was found to be alumina powder. When added to zinc oxide powder in a 3 2 ratio, compressive strength was increased by 80 % and tensile strength by 100 % (cements were mixed at a powder/liquid ratio of 2 1). Because of the dilution of the zinc oxide, setting time (at 37 °C) was increased by about 100%. As far as is known, this invention has not been exploited commercially. 

The effect on cement C is particularly dramatic and the flexural strength of cement C is exceptionally high. In part, this is to be attributed to the high powder/liquid ratio. These results are to be compared with the flexural strengths of early polyalkenoate cements which were c. 10 MPa. 

Cook, W. D. (1983a). Dental polyelectrolyte cements. II. Effect of powder/liquid ratio on their rheology. Biomaterials, 4, 21-4. 

Crisp, S., Lewis, B. G. Wilson, A. D. (1976c). Characterization of glass-ionomer cements. 2. Effect of powder liquid ratio on the physical properties. Journal of Dentistry, 4, 287-90. 

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