Powders density

The effective density of a particle is the particle mass divided by the volume of liquid it displaces (Archimedes density). Its true density is the particle mass divided by the volume it would occupy if it were compressed so as to eliminate all the pores and surface fissures. Its apparent density is its mass divided by its volume, excluding open pores but including closed pores. 

Quoted density values in standard reference works are of the materials true density. If density is determined using a gas pyknometer, the volume measured would include closed pores but exclude open pores i.e. the measured density would be the apparent density. If the suspending liquid penetrates all the cracks and fissures on the particle surface, the measured volume would be the same as that determined by gas pyknometry but the total mass would be greater due to the included liquid that will remain with the particle as it falls in the liquid, hence its sedimentation density will be intermediate between the apparent density and the true density and greater than the effective density. These differences are usually not highly significant for coarse particles unless they are highly porous. 

In density determination the volume of fluid, displaced by a known weight of powder, is determined. Since weight can be measured accurately, the problem is that of accurate determination of volume. With pyknometers (or density bottles) the fluid is a liquid, usually water with surfactant, unless the powder is water miscible. With gas pyknometers the fluid is usually dry air or helium. 

Wilkes and Allen [115] found that using this procedure with BCR 66 quartz gave a density of 2630 kg nr reproducible to 20 kg nr.  

If liquids other than water are used they should have a low evaporation rate under vacuum and a high boiling point ( 170°C) aromatic or aliphatic compounds are suitable. The use of oil presents a particular problem in that it is difficult to ensure that the outside of the bottle is completely oil free. 

Porosity can be an advantage or a disadvantage in ceramic powders, depending upon the processing and final application. Tailoring of the pore size distribution is very important for catalytic substrates, because access to the catalytic sites depends on these diflusional pathways. 

---

Nickel Hydroxides. Nickel hydroxide [12054-48-7], Ni(OH)2, is a light-green, microcrystaUine powder, density 4.15 g/cirr . It decomposes... 

Nickel Arsenate. Nickel arsenate [7784-48-7] Ni2(As0 2 8H20, is a yellowish green powder, density 4.98 g/cm. It is highly iasoluble ia water but is soluble ia acids, and decomposes on heating to form As20 and nickel oxide. Nickel arsenate is formed by the reaction of a water solution of arsenic anhydride and nickel carbonate. Nickel arsenate is a selective hydrogenation catalyst for iaedible fats and oils (59). 

Potassium Methylate. Potassium methoxide [865-33-8] KOCH, mol wt 70.13, is a fine, free-flowing, yellowish-white, caustic, hygroscopic powder purity 96.5—99% powder density after loose shaking, 0.75 g/mL apparent density (packing weight), 1.00 g/mL medium grain size, 0.05 —0.8 mm easily soluble in alcohols (33% in methanol at 20°C), insoluble in hydrocarbons. 

Magnesium Methylate. Magnesium methoxide [109-88-6] Mg(OCH2)2, mol wt, 86.3, is an almost white powder powder density 0.5 g/mL ... 

Bismuth Trifluoride. Bismuth(III) duoride is a white to grey-white powder, density 8.3 g/mL, that is essentially isomorphous with orthorhombic YF, requiring nine-coordination about the bismuth (11). It has been suggested that BiF is best considered an eight-coordinate stmcture with the deviation from the YF stmcture resulting from stereochemical activity of the bismuth lone-pair electrons. In accord with its stmcture, the compound is the most ionic of the bismuth haUdes. It is almost insoluble in water (5.03 0.05 x 10 M at pH 1.15) and dissolves only to the extent of 0.010 g per 100 g of anhydrous HF at 12.4°C. 

Typical polarization curves for alkaline fuel cells are shown in Fig, 27-63, It is apparent that the all aline fuel cell can operate at about 0,9 and 5()() rnA/cnr current density. This corresponds to an energy conversion efficiency of about 60 percent IIII, The space shuttle orbiter powder module consists of three separate units, each measuring 0,35 by 0,38 by I rn (14 by 15 by 40 in), weighing 119 kg (262 lb), and generating 15 kW of powder. The powder density is about 100 W/L and the specific powder, 100 W/kg,... 

The bulk factor (i.e. ratio of the density of the moulding to the apparent powder density) of powder is usually about 2-3 but the high-shock grades may have bulk factors of 10-14 when loo.se, and still as high as 4-6 when packed in the mould. Powder grades are quite easy to pellet, but this is difficult with the fabric-filled grades. 

Control tests on the moulding powder include measurement of water content, flow, powder density and rate of cure. 

As shown in Fig. 6.6, the peak pressures are little affected by the density of the powder. This behavior is characteristic of a reverberation process to achieve peak pressure. On the other hand, the mean bulk temperature is strongly affected by the powder density, representing the volume compression to achieve solid density. 

The synthesis effort was initiated by the Horie group on mechanically blended powder mixtures of 3 parts nickel with 1 part aluminum in molar proportions and a similar sample composed of a composite particle of nickel plated on aluminum in similar proportions. The powders were a 44 74 m nickel powder and a 5-15- m micron aluminum powder, a coarse fine mixture. The powder mixtures were shock loaded to peak pressures of 7.5 and 22 GPa with starting powder densities of 60% of solid density. 

Size Volume (mL) Fill weight (g) at powder density of 0.8 g/cm3... 

Bulk powder density must be distinguished clearly from the true density of parti-eles. Bulk powder density is simply the mass of a powder bed divided by its volume. The volume of the powder bed ineludes the spaces between agglomerates, between primary particles, and the volume of micropores within the partieles. These voids... 

Orange-yeUow or reddish amorphous powder density 4.12 g/cm decomposes at 75°C insoluble in water and alcohol soluble in hydrochloric acid, caustic alkalies and ammonium hydrosulfide. 

Monohydrate, Ba(0H)2 H20 is a white powder density 3.743 g/cm shght-ly soluble in water soluble in dilute mineral acids. Octahydrate, Ba(0H)2 8H20 is a colorless monoclinic crystal density 2.18 g/cm at 16°C refractive index 1.50 melts at 78°C vapor pressure 227 torr loses seven molecules of water of crystallization when its solution is boiled in the absence of atmospheric CO2 forming solid monohydrate further heating produces anhydrous Ba(OH)2 melting at 407°C readily dissolves in water (3.76 g/100 g at 20°C and 11.7 g/100 g at 50°C) aqueous solution highly aUtahne also soluble in methanol shghtly soluble in ethanol insoluble in acetone. 

Colorless cubic crystal or white yellowish powder density 5.72 g/cm melts at 2,013°C moderately soluble in water at ambient temperatures (3.48 g/100 g at 20°C), highly soluble in boding water (90.8 g/100 g at 100°C) aqueous solution highly alkaline also, soluble in ethanol, ddute mineral acids and alkalies insoluble in acetone and liquid ammonia. 

White amorphous powder density 3.02 g/cm hardness 9 Mohs melts at 2,507°C vaporizes at 3,900°C insoluble in water dissolves slowly and sparingly in concentrated acids and concentrated aqueous solutions of alkalies. 

Yellowish-white amorphous powder density 4.96 g/cm insoluble in water, soluble in acids Ksp 3.2 x lO- o... 

White powder density 4.93 g/cm decomposes at 260°C insoluble in water and ethanol dissolves in acids. 

Yellow monoclinic crystal or powder density 8.90 g/cm melts at 817°C vaporizes at 1,890°C insoluble in water soluble in acids. 

Colorless, transparent triclinic crystal or white granule or powder density 1.435 g/cm3 melts at 171°C under normal heating however, slow heating causes loss of water sparingly soluble in cold water (4.7% at 20°C) pH of 0. IM solution 5.1 readily dissolves in hot water (19.1% at 80°C and 27.5% at 100°C) also soluble in lower alcohols and moderately soluble in pyridine. 

White, cubic crystal or powder density 2.226 g/cm sparingly soluble in water 1.71g/100mL (at 15°C) slightly soluble in alcohol dissolves in alkah, metal cyanides, and hydroxides. 

Ddiydrate may occur as lumps or powder density 2.32 g/cm partially loses water on heating at 100°C slightly soluble in water (2.4 g/L at 25°C) Ksp =2.4x10 almost insoluble in organic solvents. 

The (3-modification is a yellow powder density 5.45 g/cm converts to the a-form when heated to 400°C absorbs moisture from air, the yellow powder becoming green droplets dissolves readily in water forming a colorless solution which turns pink on heating. 

The anhydrous salt is pale red powder density 2.49 g/cm decomposes around 100°C soluble in water. 

Grayish black powder density 5.18 g/cm decomposes at 895°C insoluble in water soluble in concentrated mineral acids. 

Black monoclinic or hexagonal crystals or powder density 4.6 g/cm refractive index 1.45 hardness 1.8 Mohs decomposes at 220°C insoluble in water, ethanol and aUtabs. Ksp 8.0xl(h34j soluble in nitric acid, ammonium hydroxide and potassium cyanide solutions also soluble in hot hydrochloric and sulfuric acids. 

Red-hrown amorphous powder density 3.40g/cm3 soluble in acids insoluble in water and alcohol. 

White amorphous powder density 6.51 g/cm melts at 2,305°C vaporizes at 4,200°C insoluble in water dissolves in dilute mineral acids. 

Colorless needles or white powder density 4.0 g/cm explodes on heating at 350°C shghtly soluble in water, 230 mg/L at 18°C and 900 mg/L at 70°C very soluble in acetic acid insoluble in ammonia solution. 

Red tetragonal crystals or brown powder density 9.64 g/cm decomposes on heating at 290°C practically insoluble in water also insoluble in alkalis moderately soluble in hydrochloric acid and also, in nitric acid-hydrogen peroxide mixture slowly dissolves in acetic acid. 

White amorphous powder density 7.41 g/cm dehydrates above 130°C and decomposes at 145°C shghtly soluble in water, 155 mg/L at 20°C Ksp 1.42xlCL2o at 25°C soluble in dilute acids and alkalies insoluble in acetone... 

---