Particule size effects

Various works of literature aim to prepare titanium oxide nanosized or nanostructured to improve performance in power. 

It seems then two options are available to reach high-power density electrode on negative side for Li4Ti50i2 nanowires or bi-modal distribution of nano- and micro-sized compounds. 

Porous rutile Ti02 nanorod micospheres performances are illustrated Fig. 11.21. 

Discharge capacity with respect to cycle number for the hierarchical porous rutile nanorod microsphere electrodes at different charge/discharge rate. 

Nevertheless, all these data are provided on electrodes with low specific capacities per surface area and lots of work is needed to obtain similar results on denser electrode. We can suspect the same behaviour as the one for Li4Ti50i2 meaning nanowires or nanorods will be preferable than spherical nanosized particules. 

---

EPA will closely examine particulate size distribution in particulate emission trades because finer particulates disperse more widely, remain in the air longer, and frequently are associated with more adverse health effects. 

Shaw, P. J. 1994. The effect of pH, dissolved humic substances, and ionic composition on the transfer of iron and phosphate to particulate size fractions in epilimnetic lake water. Limnology and Oceanography 39 1734—1743. 

Each is discussed in Sec. 17 of this handbook under Gas-Solids Separations. The effectiveness of conventional air-pollution-control equipment for particulate removal is compared in Fig. 22-25. These fractional efficiency curves indicate that the equipment is least efficient in removing particulates in the 0.1- to 1.0-pm range. For wet scrubbers and fabric filters, the very small particulates (0.1 pm) can be efficiently removed by brownian diffusion. The smaller the particulates, the more intense their brownian motion and the easier their collection by diffusion forces. Larger particulates (>1 pm) are collected principally by impaction, and removal efficiency increases with particulate size. The minimum in the fractional efficiency curve for scrubbers and filters occurs in the transition range between removal by brownian diffusion and removal by impaction. 

J.F. Kriz, J. Monnier, and M. Ternan, Nickel - molybdenum - alumina catalysts Effects of doping with fluoride and lithium and changes in particulate size when applied to bitumen hydroproceasing, Preprints, llth Can. Symp. Catal 11 (1990) 201 210 ... 

The mechanism of carbon oxidation is very difficult to investigate for several reasons i) the higli exothennicity of the reaction provides a difference of temperature between the solid surface and the gas ii) the existence of several varying parameters during reaction due to mass transfer effects (pore structure and particulate size modifications, swelling, cenosphere formation). 

For HA, at low pH (3.5), particulates were measured in the absence and presence of calcium. Calcium increased the measured particulate size, indicating aggregation of organic colloids. At pH 8 particles formed in the absence of calcium, which shows that there may be some undissolved HA. At pH 10, no particulates were measured and the HA was fully dissolved. Once calcium was added at pH 10, particulates were measured, possibly confirming the co-precipitation of organics with calcite. In the presence of 25 mM calcium, particles are smallest at pH 8 and largest at pH 3.5. Organic concentration did not have a measurable effect on the size of the colloids, and at 25 mM CaCl 2 particles formed at 25, 50, and 75 mgL" HA as DOC. 

Quenching of Products of Direct UFe Decomposition in Thermal Plasma. Integrating kinetic equation (7-48), derive formula (7-49) for the mass decrease of uranium-containing product particles due to their gasification by fluorine. Analyze the effect of initial particulate size on the rate and characteristic time of the heterogeneous reverse reactions. Compare the efficiencies of quenching of UF4 and metallic uranium. 

Burnett RT, Cakmak S, Brook JR, Krewski D (1997) The role of particulate size and chemistry in the association between summertime ambient air pollution and hospitalization for cardiorespiratory diseases. Environ Health Perspect 105 614-620 Burnett RT, Smith-Doiron M, Stieb D, Cakmak S, Brook JR (1999) Effects of particulate and gaseous air pollution on cardiorespiratory hospitalizations. Arch Environ Health 54 130-139 Burnett RT, Brook J, Dann T, Delocla C, Philips O, Cakmak S et al (2000) Association between particulate- and gas-phase components of urban air pollution and daily mortality in eight Canadian cities. Inhal Toxicol 12 15-39... 

Step 3—Granulation. In the third step, binder and lubricants are added and mixed with the ceramic materials, as a result the particulate size is effectively larger than 100 pm. The larger size is required produces flowable materials for pressing. It should be noted that water could be used as part of the binder and lubricants. 

Emission of fly ash into the atmosphere may cause a number of environmental and human health problans. Particles emitted are mainly in the <1 pm diameter range since larger size particulates are effectively ranoved by control devices. Such small particles can be inhaled by humans and deposited in various regions of the respiratory system. This may lead to health complications. Airborne particles can diminish visibility and the dispersion and deposition of particles could have adverse effects on soil and water. Leaching of particles may lead to unacceptable and even dangerous contamination levels of groundwater. 

Honga, S.J., Juna, H., Boisea, P.H., Lee, J.S. Size effects of WO3 nanocrystals for photooxidation of water in particulate suspension and photoelectrochemical film systems. Int. J. Hydrogen Energy 34, 3234-3242 (2009)... 

Also pore sizes effects the smallest particule azes collected by the ma. ... 

The measurement of the NMR shift of a metal in small particulate form addresses quite directly the important question of at what size a metal particle begins to develop metdlic properties. Particles of copper (less than 8 nm) have been observed to have a diminished Cu NMR Kni t shift at low temperature [235] as a result of quantum size effects (i. e. the loss of the metallic band structure). This will have a clear relevance to the study of colloidal metal partides. 

The solubility of terephthalic acid in the above-mentioned solvents is very low, which means that the acid must diffuse continuously from the solid particules to the solution where the reaction takes place. In such a case, the first question which arises is does the diffusion control the kinetics of the overall process In all cases, the authors claimed that the reaction rate is never affected by the amount of undissolved terephthalic acid and that the reaction proceeds through a chemical kinetic control. Under the experimental conditions used by Bhatia et al. the diffusion rate of terephthalic acid from the solid particles to the solution is 9.5x 10 mol cm" s at 100 °C and that of ethylene oxide from the gas phase to the liquid is 19.4 x 10" mol cm" s" . These values are far above the rate of formation of the diester(bishydroxy-ethylterephthalate), as this is only 5.84 x 10" mol cm" s" . Moreover, the independence of the reaction rate on the mass transfer effects was shown by varying the values of some parameters (e.g., ethylene oxide flow-rate, stirrer-speed, particule size, terephthalic acid charge) in a large range. 

Nanocrystalline particulate films, which exhibit pronounced quantum size effects in three dimensions, are of great interest due to applications in solar cell (108-112) and sensor (57, 113-115) applications. They exhibit novel properties due to not only the SQE manifested by individual nanoparticles but also the total surface area. Unlike MBE and MOCVD methods used to prepare quantum well electrodes, these electrodes can be prepared by conventional chemical routes described in Section 9.5.2.2. For example, II-VI semiconductor particulate films were prepared by using low concentrations of precursors and by controlling the temperature of the deposition bath. Nodes demonstrated the SQE for CdSe thin films deposited by an electroless method (98). The blue shift in the spectra of CdSe films has been demonstrated to be a function of bath temperature. As described in Section 9.5.2.1, electrodeposition of semiconductors in non-aqueous solvents leads to the formation of size-quantized semiconductor particles. On a single-crystal substrate, electrodeposition methods result in epitaxial growth (116, 117), and danonstrate quantum well properties. 

---