Helium Pycnometer Research Articles

Ni-Zn Ferrite Nanoparticles Prepared by Combustion Reaction

The combustion reaction is an important powder preparation process by which several hundred compounds may be prepared. Ni-Zn ferrite nanoparticles (Ni 1-x Zn x Fe 2 O 4 , x = 0,3; 0,5 and 0,7 mol) have been prepared by a single step solution combustion reaction using nitrates and urea as fuel. XRD, BET, SEM, and helium pycnometer characterized the as-prepared powders. Ni-Zn ferrite nanoparticles prepared by the present method can easily form the well-crystallized particles with a large surface area in the range of 42-64 m 2 /g. The resulting powders showed extensive XRD line broadening and the crystallite sizes calculated from the XRD line broadening were in the nanometer range (19-25 nm). The results evidenced the influence of different compositional variables on the powders characteristic.

Gas flow through highly porous graphite matrices

Highly porous graphite matrices with 20–200 kg m −3 of bulk densities have been characterized using helium pycnometer, mercury porosimeter, and fluid flow methods, i.e. both gas permeation and diffusion measurements. The gas permeability is ranging from 10 −12 to 10 −15 m 2 and decreases as the bulk density of the graphite matrix increases. According to the Carman–Kozeny correlation, the evolution of the gas permeability with respect to the bulk density is very well correlate with, on the one hand, the increase of the tortuosity, and on the other hand, the decrease of the porosity as well as the pore diameter with the bulk density of the graphite matrix.

Synthesis, microstructure and magnetic properties of Ni–Zn ferrites

Ni–Zn ferrite powders with a nominal composition of Ni 0.5Zn 0.5Fe 2O 4 were prepared by combustion synthesis, using urea as fuel. The large quantity of gas that developed inhibited particle aggregation and yielded soft powders suitable for dispersion and use. The as-prepared combustion products, helium pycnometer and BET, which were characterized by XRD, showed a high specific surface area (44.26 m 2/g) and a very small particle and crystalline phase with atomic level homogeneity. The samples were uniaxially compacted by dry pressing and sintered at 1100°C, 1200°C, 1300°C and 1400°C for 2 h. The samples were characterized by bulk density, SEM, and B– H loop measurements. Optimum properties were obtained for samples sintered at 1200°C. The Ni–Zn ferrite presented a uniform microstructure with small grain size (2.0 μm), high density (95% TD) and significant hysteresis parameter values.

Organic–inorganic hybrids derived from 2-hydroxyethylmethacrylate and (3-methacryloyloxypropyl)trimethoxysilane

Composites based on (3-methacryloyloxypropyl)trimethoxysilane and 2-hydroxyethylmethacrylate have been prepared and their properties are studied. Chemical structure of the materials made by a range of synthetic approaches was defined using nuclear magnetic resonance spectroscopy and gel permeation chromatography. Thermal properties such as glass transition temperature of the systems were determined. The inorganic phase content was measured after the samples were decomposed at high temperatures in the furnace. The small angle X-ray scattering technique was used in an attempt to describe the possible morphologies of the systems. Density was measured using a Helium Pycnometer and hardness was determined using a Vickers hardness tester. Resistance of the surface to an abrasive material was studied by following weight and transmission loss during erosion testing.

Dispersivity and Phase Composition of Zirconia-Based Powders

Results of an electron microscopic and x-ray diffraction study and data on dispersivity (obtained using a microanalyzer) and density (obtained using a helium pycnometer) of powders in the ZrO2 – Al2O3 system containing 93.54 – 100 wt.% ZrO2 are presented. The powders are prepared by a chemical co-precipitation method. Crystalline and morphological structural features of powder particles are considered and compared to those of powder particles of close composition obtained by a plasma-assisted chemical method. Effects of morphology and structure of the particles on the processability of powders are discussed.

Influence of the metakaolin on porous structure of matrixes based in mk/cement

The incorporation of pozzolanic materials in the manufacturing of blended cement has a positive effect on the improvement of blended mortar and concretes performances. These active additions modify porous structure, impeding or delaying the access of aggressive solutions and, therefore materials more durable are possible of obtaining. An increase or decrease on the durability of blended pastes, mortars and concretes will depend on chemical and mineralogical compositions, fineness and reaction kinetics of these pozzolans. The current work shows the results of a research carried out in blended pastes to know the effect of activated material (metakaolin) on the microporosity of pastes elaborated with different amounts of mk (0-25%). A water/ binder ratio of 0,55 was used. Samples were cured at 20oC for 360 days. The evolution of total, capilary and gel porosity as well as average pore size were carried out through mercury intrusion porosimeter (MIP). Also, the helium pycnometer as alternative method to obtain additional information about porosity above 1,4 A was used. A good correlation between both methods has been obtained. In addition, it is proposed the best mk content for the elaboration of mk-blended pastes.

Molecular Weight and Specific Gravity Distributions for Athabasca and Cold Lake Bitumens and Their Saturate, Aromatic, Resin, and Asphaltene Fractions

Molecular weight and specific gravity distribution data are required for characterizing oils containing complex mixtures, and this characterization information is very essential for the computation of thermodynamic properties and phase equilibria. The accuracy of these computations will be enhanced if molecular weight and specific gravity data of fractions containing similar groups/structures or common solubility properties are used. This is because the critical properties normally correlate better for a single fraction than for the whole oil. Data in this work is relevant to the phase equilibrium calculations and predictions of asphaltene precipitation from representative Canadian bitumens. Athabasca and Cold Lake bitumen samples were used and divided into asphaltene and deasphalted oil fractions by adding 40 volumes of n-heptane. The deasphalted oils were divided into saturate, aromatic, and resin fractions using a modified ASTM D2007 procedure. The average molecular weights of these SARA fractions were measured using vapor pressure osmometry (VPO), and the molecular weight distributions of the SARA fractions were measured using gel permeation chromatography (GPC) calibrated with polystyrene standards. Results were verified using VPO measurements, and the correction factors for the GPC distributions were calculated. The specific gravities of saturate and aromatic fractions were measured using an Anton-Paar densitometer, and resin fraction values were obtained using a water pycnometer and those of asphaltenes using a helium pycnometer. Specific gravity distributions were computed using the measured data and the correlation reported in the literature.

99/00869 Effect of particle size in swelling ratio for a bituminous coal : Krzesinska, M. Erdoel, Erdgas, Kohle, 1998, 114, (7/8), 388–389

Swelling ratio in pyridine has been measured for a selected bituminous coal of particles sizes ranging from 10 μm to 5 mm. The density of samples after action of pyridine has been determined using a helium pycnometer. The dependences of swelling ratio and density on the size of particles have also been determined. Saturation of dependences for particles sizes of about 0.2 mm has been observed. A model explaining the dependence of swelling ratio on particle size is presented.

Synthesis and Sintering of BaTiO3 Powders by the Glycine-Nitrate Process Using Metal Carbonate and Alkoxide.

BaTiO3 powders were synthesized by glycine-nitrate process, using BaCO3 and Ti[OCH(CH3)2]4 as starting materials. Nitric acid was used as a solvent for the starting materials as well as an oxidant for self-combustion. The physical and chemical properties of as-prepared and calcined powders were characterized by helium pycnometer, X-ray diffraction, BET method and SEM. Single cubic phase of BaTiO3 was obtained at 1000°C. When the glycine/cation molar ratio was 1.2, the reactivity of self-combustion was the highest and the degree of aggregates after calcination was very low. Relative density of 95% was obtained at 1400°C when the molar ratio of 1.2 for glycine/cation was applied. The dielectric constant of the sintered body was about 2000 at 1400°C.

Porous graphite matrix for chemical heat pumps

Expanded graphite powders were prepared by rapid heating of expandable graphite powders intercalated with sulfuric acid at different heat treatment temperatures (HTT). Porous graphite matrices with 100–400 kg m −3 of bulk density were fabricated by pressing expanded graphite powders in order to use as heat conductive media. They were characterized using an C/S analyzer, inductively coupled plasma spectroscopy, X-ray diffraction, scanning electron microscopy, Fourier transform infrared (FTIR), nitrogen adsorption, optical microscopy and helium pycnometer before and after heat treatment. Gas permeability and thermal conductivity were measured for porous graphite matrices with different HTT and bulk densities. Chemical analysis and FTIR showed that as the HTT of expandable graphite powders increase, the residual sulfur content decreased remarkably. Nitrogen adsorption experiments for expanded graphite powders showed that specific surface area and total pore volume increased with HTT. Helium penetration results showed that porous graphite matrices with different HTT have noticeably different open porosities which were attributed to the different degrees of expansion of graphite layers. The gas permeability of porous graphite matrices was in the range of 10 −12–10 −15 m 2 and exhibited higher values with low HTT. Thermal conductivity values in the axial and the radial directions were in the range of 4.1–20.0 and 4.6–42.3 W mK −1, respectively. A semi-empirical model was developed that can be used to correlate with the thermal conductivity of graphite matrix on the basis of solid conductivity, bulk density and porosity.

Tailor‐made porous solid foods

A method of controlling the porosity of cellular solid foods and its dependence on solids content were investigated. Freeze‐dehydration of cold‐set alginate gels was used to produce tailor‐made porous solids. Gels were composed of sodium alginate, corn starch, oil and other additives necessary to induce gelation. Porosity values were derived from particle and bulk densities utilizing a helium pycnometer and a volumetric displacement method. To achieve a wider range of porosities, the gels were immersed in sucrose solutions of 10 to 60 8Bx. Gel porosity after drying decreased from 0.85 to 0.42 and 0.07 after immersion in the 30 and 60 8Bx solution for 183 and 158 h, respectively. Similarly, after immersing gels containing an additional 5% soy oil, porosity decreased to 0.36 and 0.04 after 165 and 158 h, in 30 and 60 8Bx solution, respectively. Preparation and formulation play a significant role in porosity, and they can both be utilized to control its value within the range 0.85–0.04. SEM micrographs revealed changes in the original cellular solid, characterized by numerous large void spaces, to a denser and more uniform appearance of the specimen after immersion in the 60 8Bx sucrose solution. The dry gel system with controlled porosity provides a novel tool for the production of tailor‐made cellular‐solid foods.

Methods for Characterization of Kernel Density and Aflatoxin Levels of Individual Peanuts1

Abstract A helium pycnometer, specific gravity bottle and a displacement method were evaluated for the determination of individual peanut (Arachis hypogaea L.) kernel densities. Three coating materials were tested to minimize water absorption with the latter two methods. The displacement technique with a coefficient of variation (CV) of less than 0.1% was found to be most reproducible and had a total variability of 0.002 g/cm3. Polyurethane was adopted as the coating material of choice. A reverse phase High Performance Liquid Chromatography (HPLC) assay was adapted for quantification of the aflatoxins in individual peanuts. Picogram levels of aflatoxin were quantified with an average recovery of 82%. Characterization of peanut kernel density distributions and relationships between kernel density and aflatoxin level are envisioned with data generated using this method.

Carbon having unique properties prepared from microcrystalline cellulose

Carbons possessing unique properties somewhat like those of glassy carbon have been prepared from structural microcrystalline cellulose precursors by prolonged pyrolysis up to 800°C in a nitrogen atmosphere. Samples of the dry microcrystalline cellulose powders were fabricated into various shapes in a high pressure mold or by slow drying of an aqueous suspensoid gel in a mold under ambient conditions. Pyrolysis gave objects of amorphous carbon about one-third the original size. Some of the carbons are about as hard as glass and have a density (helium pycnometer) of 2.01 g/cm 3 ( cf. graphite 2.265). As expected, the carbon resulting from the pressed microcrystalline cellulose dry powders had a lower density and more pores than carbons produced from structural forms, prepared from air dried, aqueous gels. Pore size and pore size distribution data and scanning electron photomicrographs are shown.