Particles needle-shaped

Particle shape, as indicated in figure under 100X magnification shall be free from hair shape or needle shape particles... 

Non-spherical filler particles are also of considerable interest [50,69]. Prolate (needle-shaped) particles can be thought of as a bridge between the roughly spherical particles used to reinforce elastomers and the long fibers frequently... 

A highly water-soluble drug was incorporated at 35% into hard gelatin capsules. The active drug substance characteristics were described as small needle-shaped particles, low bulk density, 0.1 g/cm, extremely poor flow, sticky, and highly compressible. 

Nonspherical particles. Little is known about the fall velocity of nonspherical particles. It would be expected that needle-shaped particles would feel less air resistance per unit mass and fall faster but that irregularly shaped particles would, in general, feel more resistance and fall more slowly. The net effect depends upon the distribution of particle shapes, which is also uncertain. 

In an alternative process, the starting material consists of needle-shaped particles of a-Fe203 instead of FeOOH pigments [5.9], [5.10]. The synthesis is carried out in a hydrothermal reactor, starting from a suspension of Fe(OH)3, and crystal growth is controlled by means of organic modifiers. 

Crystal habit modification. Several crystal habits have been reported in the open and patent literature for zeolite omega. Elongated hexagonal rods (15,16) or fibres (17) have been reported when the zeolite resulted from the recrystallization of another zeolite, Y (15) or S (17), or of clays (16). Moreover the natural counterpart of zeolite omega, mazzite, appears as bundles of needle-shaped particles (18). All these solids have been grown at low supersaturation levels, hence under conditions in which our results show that the growth in the direction <001> prevails on the growth normal to the c-axis (Fig.8). 

Kaye and Yousufzai [115] discuss the use of trapped particles, i.e. the particles blinding the sieve mesh at the completion of sieving, for determination of elongation ratio. A general formula was developed [116] on the probability of particles of different shape passing through a sieve and the formula has been applied to spherical and needle shaped particles. 

Iron oxide— Tiny, needle-shaped particles that can be easily magnetized, coating one side of the plastic cassette tape. 

Note, many of these diameters assume a random particle orientation relative to the ocular scale or graticule. This is important for sample preparation because anything that biases the orientation of the particles on the microscope slide will bias the results. For example, to uniformly cover a microscope slide with particles one could usually swipe a spatula over the slide which could potentially induce a preferred orientation to the particles, especially for needle shaped particles. 

Particle shape can also affect blending processes. Spherical and cubic shaped particles typically exhibit good flow properties and therefore promote blending. However, readily flowing materials may also be more prone to segregation. Plates and needle shaped particles have poor flow properties, are harder to dilate/expand, and are more likely to agglomerate. As a result, it may be more difficult to achieve uniformity when blending plate and needle shaped particles. Conversely, a benefit to this decreased mobility is that once blended, these are more likely to stay blended. 

In(OH)3 nanopowder was prepared via the sonication of an aqueous solution of InCl3 at room temperature and at 0 °C. At these temperatures, nonsonicated hydrolysis does not occur. The role of the ultrasound radiation and the mechanism of the reaction are discussed. The proposed mechanism is based on the sonohydrolysis of In (III) ions in the outer ring, and the liquid shell, of the collapsing bubble. The product, In(OH)3, was obtained as needle-shaped particles. 

The analgesic paracetamol has been processed in a pilot plant from dimethylformamide (DMF), ethanol, and acetone. The plant used had the capacity of 30kg/hr of CO2 and 0.6m /hr solution and included an 8 L precipitation vessel. The operating temperature was fixed at 45° C while the pressure was varied between 100 and 200 bar. Particle size and morphology varied mostly with the nature of the solvent. Spherical particles were obtained from DMF and acetone, while needle-shaped particles could be produced from ethanol and acetone. Rhombic particles were produced only from ethanol. Particle size varied between 1 and 10 pm depending on the operating pressure. ... 

The fibrous structure of sepiolite is composed of talc-like ribbons with two sheets of tetrahedral silica units linked by oxygen atoms to a central octahedral sheet of magnesium. It has needle-shaped particles with chaimels oriented along the fibers which can absorb liquids. Sepiolite has three kinds of water hygroscopic water, crystallization water, and constitution water. The ciystallization water is removed at 500°C and constitution water is removed at 850°C at which point physical properties change brought about by ciystal folding of sepiolite. ... 

All three dimensions need not be in the colloidal range fibers or needle-shaped particles in which only two dimensions are in this range and thin films or disk-shaped particles in which only one dimension is in this range may also be treated as colloidal (7). Nor must the units of a colloidal... 

Fig. 10.9 Circles (defining particle diameter) with the same area as the projections of a needle shaped particle. The situations on the right represent various positions in space (viewed in directions x and y) of the same particle...

Fig. 10.10 Micrographs of needle-shaped particles (crystallites) featuring large aspect ratios...

The particle size affects the value of the active surface, as is clearly shown in Table 7.1. The surface area also depends on the particle s shape — the smallest specific surface is encountered with spherical particles, the largest specific surface being characteristic for particles of plate shapes in the given fraction. In the more coarse fractions, spherical particles are prevalent. In colloidal dispersions flat and needle-shaped particles are predominant, this is connected with the stratified character of the crystal lattice of clay minerals forming the major portion of the colloidal fraction. 

When the isotropic melt is cooled, the smectic phase often makes its appearance in the form of needle-shaped particles showing evidence of focal conic structure. Examples of such needles, termed bdtonnets, can be seen in fig. 2.. 5 b). 

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