Powder loading

Sayama, K., Arakawa, H. 1992b. Remarkable effect of Na CO, addition on photodecomposition of liquid water into H, and O, from suspension of semiconductor powder loaded with various metals. Chem Lett 2 253-256. 

Generally, the preparation of washcoated structured catalysts is governed by several parameters, such as the nature and particle size of the precursor powder, loading of powder, nature and concentration of dispersants, temperature of the slurry, use of binders in the slurry and deposition of a primer layer on the monolith. 

Loading An operator, working with the minimum quantity of bulk powder, loads the composition into tubes or other containers, or produces pellets for later use in finished items. The making of "stars" - small pieces of color-producing composition used in aerial fireworks - is an example of this pelleting operation. 

Several variants of the biosensor in Scheme 5 have been proposed. One is a CPE containing at its tip a paste of graphite powder loaded with HRP and ferrocene ([Cp Fe(II) Cp]) mediator, which is further covered with a cellulose acetate film coated with Nafion. The biosensor is mounted on a FIA system in a three-electrode setup, as working electrode at a potential of 4-100 mV vs. SCSE and a Pt counterelectrode. The LOD (SNR 6) for H2O2 is 200 fmol (20 p,L injection of 10 nM solution), with linearity up to 25 In... 

Table III summarizes the results of a laboratory-scale investigation of these various powder-loading techniques. Except for simple pouring, the differences between various filling techniques may be relatively minor. In practice, the method selected depends upon the casting powder type and the geometry of the charge to be manufactured.

The response time had again been cut in half. Nineteen inches of black powder were consumed in the test. In order to get the water on the fire a little faster, the line pressure (approximately 75 psi) was increased to 100 psi and the system was retested. This time, only six inches of powder were consumed. This system is considered highly effective and is in use today at our black powder loading operation. 

The charges generated from triboelectrification often lead to problems in industrial processing. The accumulation of charges in a silo during powder loading may... 

More detailed studies are required in order to check whether the above correlation, established on the basis of relatively rapid potential sweep measurements, holds also for the steady-state photocurrents, i.e., in the situation when the Ti02 surface becomes covered with the peroxo-titanate species. These should also include water photocleavage experiments onto titanium dioxide powders loaded with some of the catalysts investigated by Contractor and Bockris. The difficulty, associated with the fact that most of... 

Powders loaded into the single-pot processor are dry-mixed until appropriate uniformity is achieved after mixing, the binder solution is sfxayed in and wet massing ensues. Factors normally associated with the granulation process such as spray rate and volume, droplet size. 

On the basis of using only 0.0U m3 of titanate powder per month, approximately 180 kg (dry weight basis) of spent powder would be generated in one year. Titanate powder loaded with 241Am and plutonium could be dried, drummed, and stored as a retrievable transuranium waste. Alternatively, using technology... 

The bottle or jar method (see Fig. 5.28) requires a wide mouth polyethylene or polypropylene bottle for easy (low shear) powder loading. The jars must be sealed tightly to prevent the loss of the lubricant by evaporation. 

As the volume fraction of powder in a feedstock is increased, the viscosity of the feedstock rises exponentially until a critical volume fraction of powder is reached. Figure 2 shows the mixer torque (which is directly proportional to the viscosity of the feedstock) as a function of silicon carbide powder concentration in a polyethylene/wax binder system [Cle 05]. It is assume that by extrapolating the data to zero reciprocal torque, the maximum powder loading for the feedstock formulations can be determined. 

With this method, a maximum powder loading of 62% by volume was calculated for a SiC/polyethylene/wax-feedstock prepared with carbon black sintering additive. For the feedstocks without carbon black, a value of 57 vol% was calculated. This result corresponded with the fact that it was not possible to produce an extrudahle carbon black-free SiC feedstock with a powder loading higher than 52 vol%. The feedstocks prepared at 53 and 54 vol% were powdery, very brittle and did not exhibit any plastic behavior. 

Fig. 2 Reciprocal torque as a function of the binder SiC powder volume ratio. Extroplation to zero reciprocal torque (i.e. infinite torque) permits an estimate of the maximum powder loading for the feedstock to be made [Cle 05]...

Wegmann et. al. described the extrusion of polycrystalline ceramic fibers using different thermoplastic and water-based binder systems [Weg 98]. Invariably the highest powder loadings in the study were reached using the thermoplastic binder systems with all the ceramic powders considered. Furthermore, only a thermoplastic polyethylene/wax binder sys-... 

It is also possible to extrude ceramic nanopowders with thermoplastic binder systems. Scheying et. al., for example, investigated the extrusion of monoclinic zirconia nanopowder [Schey 04]. The powder loadings achieved in the feedstocks were 44 and 53 vol% when using powders with primary particle sizes of 9 and 25 nm, respectively. The binder system used consisted of either polyethylene-co-vinyl acetate or polyethylene as the major component and decanoic acid as a surfactant. 

Heiber at. al. investigated the extrusion of commercial silicon dioxide nanopower using a mixture of polyethylene and wax [Hei 04], With this thermoplastic binder system, powder loadings up to 58 vol% were achieved. With this very high powder loading it was possible to achieve dense glass fibers after sintering at 1100°C. 

Next to tubes and fibers, tbin ceramic sheets are also a very interesting subject for the development of thermoplastic ceramic extrusion systems. It has been shown that it is feasible to produce ceramic sheets and films with thicknesses under 200 pm. Figure 8 shows a picture of a ceramic sheet made of silicon dioxide nanoparticles. This technique could, for example, be used for the fabrication of multilayer ceramic bodies (e.g. multilayer capacitors, structural laminates) which currently are produced using the tape casting process. Big advantages relative to this conventional process would be the recycleability of the thermoplastic feedstocks and the higher achievable powder loading. 

Errors of sampling (the powder loaded to the stack is unrepresentative of the populations) ... 

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