Non-conducting Powders Research Articles

A technique for the preparation of powders for examination by transmission electron microscopy

Several techniques exist for preparing thin foils from powders that have been incorporated in a nickel matrix by electroplating or electroless plating. The yield and quality of foils are, however, generally inadequate for analyses requiring large numbers of thinned powders. A new technique has been developed that utilizes a plating chemistry that results in an electroless nickel (EN) matrix. Because the technique does not require a conductive substrate, it is applicable to non-conductive powders as well as to metal powders. For metal powders to be thinned electrochemically the technique produces a matrix that will thin uniformly along with the metal powders using standard electropolishing techniques. The EN matrix produced is non-magnetic and the uniformity of the electrochemical thinning of foils prepared by this method allows surface features on the powders such as splat caps to be easily observed. Also, because the technique produces a high yield of thin foils, it is useful in transmission electron microscopy studies that require large numbers of powders to be examined. The technique is illustrated along with the results of transmission electron microscopy studies characterizing the microstructure of nickel-base superalloy powders and plasma spray coating powders as a function of powder size. The powders thinned in these studies include René 95, low carbon Astroloy, AF-115, IN-100, Merl-76, as well as NiCoCrAlY, vacuum-plasma-sprayed coating alloy powders.

Glow Discharge Sputter Atomization for Atomic Absorption Analysis of Nonconducting Powder Samples

A methodology has been developed for the analysis of nonconducting (oxide) powder samples by glow discharge atomization-atomic absorption spectrometry (GDA-AAS). The mixing of an oxide powder with a copper host matrix (1:9) allows pressing of a disk sample for glow discharge sputtering. Sample-to-sample precisions are on the order of 3–4% for iron in a geological specimen. The ability to generate analytical working curves is demonstrated for the analysis of iron by mixing Fe (III) and Al (III) oxides in the copper matrix material. The possible utility of the methodology is illustrated by the analysis of iron in an NBS geological reference material. The ability to perform analyses of these sample types suggests its applicability to such matrices as ceramics, glasses, and refractory-based catalysts.

State of the art of glow discharge lamp spectrometry. Plenary lecture

The development of glow discharge sources for atomic spectroscopy is traced. The electrical characteristics of the analytically relevant sources, sample volatilisation and the predominant excitation and ionisation processes are discussed. The possibilities of using the Grimm-type glow discharge lamp with a flat cathode for the spectral emission analysis of compact metallic samples, for non-conducting powders, after mixing with metal powder and making into pellets and for in-depth profiling are described. New types of lamps and the features of glow discharges with hollow cathodes are evaluated. The use of glow discharges as atom reservoirs for atomic absorption and fluorescence spectrometry and recent advances in glow discharge mass spectrometry are also covered.

A study of direct analysis of solid samples using spark ablation combined with excitation in an inductively coupled plasma

A medium-voltage spark was used for the direct nebulization of compact metallic samples and non-conducting powders and the elutriated material was excited in a high-power argon/nitrogen inductively coupled plasma (ICP). After optimization of the spark parameters (voltage: 1 kV, capacity: 6 μF, repetition rate: 25 s −1), the carrier gas flow (1.71 argon min ) and the operating power of the ICP (3 kW), detection limits for magnesium, copper and iron in aluminium were found to be 1, 26 and 29 μ g respectively. The length of the transport tube may be increased from 0.5 to 6 m without deteriorating the power of detection by more than a factor of 2. From a characterization of the aerosol, it was found that the power of detection limitations were due to the low number of small particles arriving in the ICP. The method was applied to the direct analysis of various types of aluminium samples. For Al, AIMn, AlMgSi, AlSiCuNi and AlSiCu alloys the same calibration curves could be used. In the case of non-conducting powders pellets are briquetted after mixing the sample 1+4 with copper powder. The detection limits for a series of elements in Al 2O 3 (Fe, Mg, Mn, Pb, Si, Sr, V and Zn) range from 0.6 to 265 sm g and are of the same range as would be obtained with ICP-OES of the dissolved samples (5 g 1 ). The standard error of estimate ( s r( c X)) at a concentration level of 50 mg g is 0.05 when a copper line is taken as reference. However, as shown at the example of Al 2O 3 and CaCO 3 also then calibration curves differ from one matrix to another.

Nodulation of electrodeposited copper due to suspended particulate

Cathode nodulation was studied by electrodepositing copper at 38 mA cm−2 from acid sulphate baths which contained 0.5 g dm−3 of various suspended particulate. The conductive particulates, such as copper and graphite, produced dense nodulation at temperatures of 50° C and less. Antimony and silver powders caused pitting as well as nodulation. Non-conducting powders such as lead sulphate, lead dioxide, and gypsum produced no nodulation, and correspondingly were occluded only to a very small extent. Once formed, the nodules occluded very large concentrations of any particulate present. The nodulation decreased markedly with an increase in temperature, particularly from 50° to 70° C. With increasing Cu2+ ion concentration, the nodulation decreased nominally. These effects and characteristics of the nodulated deposits are discussed.

Reply to the critical comments on the paper: “the efficiency of universal techniques of atomic emission spectrography and spark source mass spectrography for analysis of non-conducting powders”

Reply to the critical comments on the paper: “the efficiency of universal techniques of atomic emission spectrography and spark source mass spectrography for analysis of non-conducting powders”

Applicability of a hollow cathode emission source for determining trace elements in electrically non-conducting powders

The applicability of the hollow cathode emission source for the determination of trace elements in mineral residues from ashing of biological materials is investigated. The method uses samples previously diluted with a 1:4 graphite-copper powder mixture to render them electrically conductive and subsequently pressed into the form of hollow cylinders. The procedure was tested with synthetic specimens; the latter contain Ag, Al, B, Cr, Mn, Ni, Pb, Sn, Ti and Zn, and a matrix similar to that of organic materials after mineralization. The use of Ga as an internal standard greatly improved the linearity of log I x vs log c x relationship. The precision of the measurements and the detection limits were also found to be entirely satisfactory.

The efficiency of universal techniques of atomic emission spectrography and spark source mass spectrography for the analysis of non-conducting powders

Two semi-quantitative universal techniques for the analysis of very different non-conducting powdered materials were compared with regard to matrix influences on the reliability of the analytical results. One of these techniques is based on atomic emission spectrography (AES) and was proposed by K roonen and V ader[4] several years ago. The other one is based on spark sources mass spectrograpny (SSMS) and has been developed in our laboratory more recently. To evaluate matrix effects objectively, a “total factor of variation”. V tot, was calculated as the antilogarithm of the standard deviation of the logarithms of analytical results over all matrices. The factor was compared by statistical analysis of variance to an analogous factor v rep, estimated in each case from a set of replicate determinations in one matrix and thus representing the precision of the technique. The results show that in the case of the SSMS technique v tot varies from 1.6 to 1.9 and only sometimes exceeds v rep slightly (probability P = 0.95). On the other hand for the AES procedure, v tot varies from 1.4 to 2.3 and always exceeds v rep, with a high significance ( P > 0.99). However, precision is higher in AES. From the results, the conclusion is drawn that SSMS is more suitable for elaboration of universal techniques, in the case of non-conducting powders just as in the case of compact metals.

The dispersion of powders by intense electrostatic fields. I. Experimental studies

Powder dispersion by electrostatic fields above 0.20 kV/mm has been studied at ambient temperature in a vacuum, air, sulphur dioxide, and insulating liquids, with both conducting and nonconducting powders. All the conducting powders examined were dispersible, but only some of the insulating materials (e.g., alumina) reacted to the field. Alumina was studied in some detail using different media and various electrode geometries. It was concluded that dispersion of insulating powders occurs as a result of a conducting surface film, indicating that charging of the particles is mostly by conduction electrons from the bed. Effects of the dispersing medium were also detected, especially through the use of current-voltage curves. When liquids were used instead of air, for example, pronounced hysteresis occurred, an effect ascribed to the increased settling rate of the particles. Differences in behavior were also demonstrated from one gaseous medium to another, e.g., particulate clouds, which normally show pronounced turbulence in high-voltage air dispersion, became much more uniform in pure sulphur dioxide. In addition, some powders such as lycopodium, which is unreactive to the field in air, dispersed well in sulphur dioxide. This was traced back to the corona-suppressing properties of this gas, demonstrating that production of gaseous ions at field concentrations (such as those produced by sharp electrodes or angular particles) is detrimental to electrodispersion, since ions tend to act as charge carriers in preference to the particles. Further evidence of this came from gamma ray attenuation studies used for measuring cloud densities as a function of the applied field.

A low-cost solids flowmeter for industrial use

An instrument is described for measuring the mass flow rate of dry conducting or non-conducting granular solids or powder. The capacitance-measuring electrode used offers no obstruction to the flow of the material and there are no moving parts to wear out. The principle employed is that of capacitance noise, by which the very small changes in capacitance which occur when particles move in a pipe or chute are detected. Applications to gravity-drop and pneumatic conveying and to measuring the output of short-blasting hoses are described. Materials measured include PVC chips, steel grit, aluminium oxide, glass beads and crushed walnut shell.

Determination of the temperature of a nonconducting powder in detonation deposition

1. A new method has been developed for measuring the temperature of nonconducting particles in the detonation deposition of coatings. 2. A study was made of the effects of explosive mixture composition and powder charging depth on the mean temperature of the powder particles.

Emission Spectrometric Determination of the Main Components and the Trace Elements in Nonconducting Powders by Means of the Plastic-Bounded Electrode System

One of the methods most frequently used for the spectrochemical analysis of nonconducting powders is the excitation from the powder that has been loaded onto the electrode crater. The reproducibility in data obtained from this method can be increased if the nonconducting material is mixed with a conducting one and briquetted. The goal of this procedure is to obtain a more uniform material transport into the excitation source. Because of the disadvantages of the briquett method (i.e., the effect of the structure of the briquett, the dilution of the nonconducting material, and the great pressure that must be applied), the technique cannot be used for trace analysis purposes.

Sensitivity of laser-microspectrochemical method for non-conductive powders

The analytical sensitivities for various elements which were contained in electrically non-conductive powders have been determined with Laser-Microspectral-Analyser (VEB Carl Zeiss Jena, LMA-1 and Q-24. The maximum output energy is 1 Ws.11).A laser beam was focused onto a specimen at its microscopically small area, and the vapor thus produced was then excited by an auxiliary spark discharge. A slit image method was used for slit illumination. The laser beam from a Nd-doped glass laser was obtained with normal pulse.The standard non-conductive powder (Spex Mix, No. 1000) diluted with pure graphite powders was solidified with purified phenolic resin. Craters formed on the specimen were approximately 100 μ in their diameter and its half in depth (_??_10-7 g).

Laser-Microspectrochemical Analysis on Metals and Nonmetals

Spectrochemical analysis was studied with a Laser-microspectral-Analyser and a UV-Spectrograph. A Nd-doped glass laser (Output power was 1 Ws Max.) was used.The laser light was of normal pulse. BAM standard steels and some non-conducting powders (Spex Mix diluted with graphite powder, and SiO2) which were solidified with pure phenolic resin were then analysed.Electric discharge produced between auxiliary electrodes was used to strengthen the plasmas.Maximum sensitivity was determined for several elements and was found to be of the order of 10-13-14g.Plumes from metals, nonconducting materials and various other samples were photographed to know their location from the samples surface and the electrodes.The position of plumes from the sample surface in metallic samples was lower than in nonconducting samples.

Determination of bromine and iodine in powder samples by spectra in the vacuum region

Methods for the introduction of nonconducting powder samples containing halogens into the corona of a low-voltage pulsed discharge in a vacuum are considered. It is shown that the spectra of the halogens can be obtained by using double layer pellets. Using the resonance lines in the spark spectra of bromine and iodine in the analysis enabled one to determine contents of down to 0.5 microgram which in combination with a preliminary enrichment corresponds to a relative sensitivity of 5 · 10−5%.

An extended range thermistor gas pressure gauge

The upper limit of the thermistor pressure gauge has been extended (1 atm and higher is possible) by surrounding the thermistor bead with an electrically non-conducting powder.

Electrostatic Coater Sprays Dry Powders

RETURN TO ISSUEPREVNewsNEXTElectrostatic Coater Sprays Dry PowdersSAMES unit coats mildly conducting surfaces with relatively nonconducting powders; many powders and substrates can be handledCite this: Chem. Eng. News 1962, 40, 23, 42–45Publication Date (Print):June 4, 1962Publication History Published online6 November 2010Published inissue 4 June 1962https://doi.org/10.1021/cen-v040n023.p042Copyright © 1962 AMERICAN CHEMICAL SOCIETYArticle Views5Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (573 KB) SUBJECTS:Electrostatics,Granular materials Get e-Alerts

L'étincelle glissante dans le vide comme source pour l'analyse spectrochimique d'émission

The sliding sparks are produced in vacuo between two electrodes in contact with an insulating or semi-conducting support, and show several advantages as a light source in emission spectrochemical analysis. The excitation energies are very high and a spectrum of the highly ionized elements is obtained. Moreover, as the source is producing sparks in vacuo, it is possible to study the spectrum in the extreme ultra-violet. This is an essential property as in this region sensitive lines are emitted of elements which are otherwise very difficult to detect. Two mounting devices are proposed. Using a support of refractory material (as e.g. alumina) the spectrum almost exclusively consists of lines belonging to the electrodes. As analytical applications we have studied the detection and determination of sulphur, phosphorus and carbon in steel and the detection of these elements in aluminium. A special electrode assembly allows the study of non-conducting powders. In this respect we studied the detection and determination of sulphur, phosphorus and selenium in alumina and zirconium oxide. Several examples of qualitative analysis will be given. Sulphur in copper and silver, sulphur in fluorite, chlorine in certain powders. Generally the lines used (in the spectral region 800–1200 Å) are lines belonging to the spectrum of ions, having not more than one or two electrons in the outer shell left.