Beryllium Oxide Powder Research Articles

Digitalization of the thermoplastic beryllium oxide slurry forming process using ultrasonic activation

This paper presents the results of the digitalization of the thermoplastic beryllium oxide slurry forming process using ultrasonic activation. Ceramics made from beryllium oxide (BeO) using ultrasound-assisted forming exhibit more intense sintering and, in comparison to ceramics formed without ultrasound, have reduced shrinkage (by 2.4-4.3%) and sintering temperature (by 50-180°C). The forming processes occurring during ultrasonic treatment resulted in the homogenization of the thermoplastic suspension and dense packing of BeO powders in the casting. Ultrasound activation alters the rheology of the thermoplastic slurries. These changes are attributed to processes of slurry mass dispersion and mass exchange at the phase boundary of the suspension. Ultrasound activation also enhances casting properties. During the cooling-solidification process under the influence of ultrasound, the density and strength of the castings increase due to the effective compensation of shrinkage. Shrinkage compensation is carried out according to the classical scheme by supplying a liquid suspension. For hot casting with ultrasound of thermoplastic beryllium oxide slurries, it is advisable to use compositions with a binder content of 11.0-11.7% by weight since these compositions provide better shrinkage compensation and, consequently, a denser casting.

Beryllium Oxide Powder Microstructure During Production Processing

Beryllium carbonate and hydroxide powders are studied during production processing in order to prepare pure BeO powder. Powders are supplied by the Ul’binsk Metallurgical Plant (Kazakhstan Republic). It is established that beryllium oxide powder crystallinity and morphology depend to a considerable extent on production treatment type and regimes. Microphotographs of different powder batches point to a genetic connection of their morphology with type of starting raw material, which in turn may have a marked effect on slip and press-mix preparation, on molding, and also on sintering of ceramic objects and their properties.

Experimental and calculated data of the beryllium oxide slurry solidification

Results of experiments and calculations of the mathematical model of the motion and heat exchange of the beryllium oxide slurry in the annular cavity are presented. The slurry is a highly concentrated structured system where the mineral phase is beryllium oxide powder and the liquid phase is an organic binder (paraffin, oleic acid and beeswax). The results of experiments and calculations show the process of molding of the slurry in the annular cavity. The obtained temperature field determines the transition of the slurry from liquid (viscous–plastic) to solid–plastic state. Calculated data of the isotherms of solidification zone of the thermoplastic slurry are in agreement with the experimental results.

Cs3Zn6B9O21: A Chemically Benign Member of the KBBF Family Exhibiting the Largest Second Harmonic Generation Response

Nonlinear optical (NLO) crystals are essential materials for generation of coherent UV light in solid state lasers. KBBF is the only material that can achieve coherent light below 200 nm by direct second harmonic generation (SHG). However, its strong layer habits and the high toxicity of the beryllium oxide powders required for synthesis limit its application. By substituting Be with Zn and connecting adjacent [Zn2BO3O2]∞ layers by B3O6 groups, a new UV nonlinear optical material, Cs3Zn6B9O21, was synthesized. It overcomes the processing limitations of KBBF and exhibits the largest SHG response in the KBBF family.

Designing a Deep-Ultraviolet Nonlinear Optical Material with a Large Second Harmonic Generation Response

The generation of intense coherent deep-UV light from nonlinear optical materials is crucial to applications ranging from semiconductor photolithography and laser micromachining to photochemical synthesis. However, few materials with large second harmonic generation (SHG) and a short UV-cutoff edge are effective down to 200 nm. A notable exception is KBe2BO3F2, which is obtained from a solid-state reaction of highly toxic beryllium oxide powders. We designed and synthesized a benign polar material, Ba4B11O20F, that satisfies these requirements and exhibits the largest SHG response in known borates containing neither lone-pair-active anions nor second-order Jahn-Teller-active transition metals. We developed a microscopic model to explain the enhancement, which is unexpected on the basis of conventional anionic group theory arguments. Crystal engineering of atomic displacements along the polar axis, which are difficult to attribute to or identify within unique anionic moieties, and greater cation polarizabilities are critical to the design of next-generation SHG materials.

Preparation, certification and interlaboratory analysis of workplace air filters spiked with high-fired beryllium oxide

Occupational sampling and analysis for multiple elements is generally approached using various approved methods from authoritative government sources such as the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA), as well as consensus standards bodies such as ASTM International. The constituents of a sample can exist as unidentified compounds requiring sample preparation to be chosen appropriately, as in the case of beryllium in the form of beryllium oxide (BeO). An interlaboratory study was performed to collect analytical data from volunteer laboratories to examine the effectiveness of methods currently in use for preparation and analysis of samples containing calcined BeO powder. NIST SRM(®) 1877 high-fired BeO powder (1100 to 1200 °C calcining temperature; count median primary particle diameter 0.12 μm) was used to spike air filter media as a representative form of beryllium particulate matter present in workplace sampling that is known to be resistant to dissolution. The BeO powder standard reference material was gravimetrically prepared in a suspension and deposited onto 37 mm mixed cellulose ester air filters at five different levels between 0.5 μg and 25 μg of Be (as BeO). Sample sets consisting of five BeO-spiked filters (in duplicate) and two blank filters, for a total of twelve unique air filter samples per set, were submitted as blind samples to each of 27 participating laboratories. Participants were instructed to follow their current process for sample preparation and utilize their normal analytical methods for processing samples containing substances of this nature. Laboratories using more than one sample preparation and analysis method were provided with more than one sample set. Results from 34 data sets ultimately received from the 27 volunteer laboratories were subjected to applicable statistical analyses. The observed performance data show that sample preparations using nitric acid alone, or combinations of nitric and hydrochloric acids, are not effective for complete extraction of Be from the SRM 1877 refractory BeO particulate matter spiked on air filters; but that effective recovery can be achieved by using sample preparation procedures utilizing either sulfuric or hydrofluoric acid, or by using methodologies involving ammonium bifluoride with heating. Laboratories responsible for quantitative determination of Be in workplace samples that may contain high-fired BeO should use quality assurance schemes that include BeO-spiked sampling media, rather than solely media spiked with soluble Be compounds, and should ensure that methods capable of quantitative digestion of Be from the actual material present are used.

Certification of Beryllium Mass Fraction in SRM 1877 Beryllium Oxide Powder Using High-Performance Inductively Coupled Plasma Optical Emission Spectrometry with Exact Matching

High-performance inductively coupled plasma optical emission spectrometry (HP-ICP-OES) was used to certify the Be mass fraction in National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1877 Beryllium Oxide Powder. The certified value and expanded uncertainty expressed at a 95% confidence level is (0.3576 +/- 0.0024) g/g. To obtain best results, the Be mass fractions, Mn (internal standard) mass fractions, and matrix compositions of the calibration solutions were carefully matched to those of the sample solutions for each individual HP-ICP-OES analysis. This "exact matching" approach was used because experience at NIST has shown that it often affords improved accuracy and precision in HP-ICP-OES analysis. NIST has never published these observations. Due to the toxicity of BeO and the difficulty of containing the very fine powder material, sets of solutions for HP-ICP-OES analysis were prepared by laboratories collaborating with NIST who have the experience and equipment needed to work with the material safely. Each laboratory utilized a unique digestion protocol(s). After preparing the sets of solutions, the collaborating laboratories shipped them to NIST for HP-ICP-OES analysis. NIST provided the collaborating laboratories with solution preparation kits and spreadsheets to help establish traceability of the HP-ICP-OES results to the International System of Units (SI) and to allow exact matching to be accomplished. The agreement observed among the four individual Be mass fraction values determined from the sets of solutions prepared by the collaborating laboratories was 0.074% relative (1s of mean). The excellent agreement provides a measure of confidence in the robustness of each of the digestion procedures, as well as in the certified Be mass fraction value. The analytical benefits of using exact matching for this particular certification were investigated. Results show that exactly matching the matrix compositions of the standards to the samples for each HP-ICP-OES analysis was critical to obtaining the excellent agreement observed among the individual Be mass fraction values and also helped to minimize bias and uncertainty in the certified value. Unlike previous NIST studies, exactly matching the Be and Mn mass fractions of the standards to the samples for this particular certification appears to have had little effect on the data.

A theoretical framework for evaluating analytical digestion methods for poorly soluble particulate beryllium

Complete digestion of all chemical forms and sizes of particulate analytes in environmental samples is usually necessary to obtain accurate results with atomic spectroscopy. In the current study, we investigate the physicochemical properties of beryllium particles likely to be encountered in samples collected from different occupational environments and present a hypothesis that a dissolution theory can be used as a conceptual framework to guide development of strategies for digestion procedures. For monodisperse single-chemical constituent primary particles, such as those encountered when handling some types of beryllium oxide (BeO) powder, theory predicts that a digestion procedure is sufficient when it completely dissolves all primary particles, independent of cluster size. For polydisperse single-chemical constituent particles, such as those encountered during the handling of some types of beryllium metal powder, theory predicts that a digestion procedure is sufficient only when it completely dissolves the largest particle in the sample. For samples with unknown or multi-chemical constituent particles and with particles having undefined sizes, e.g., fume emissions from a copper-beryllium alloy furnace operation or dust from a beryl ore crushing operation, a surface area-limited and single-constituent-dependent dissolution theory may not predict complete dissolution, thereby requiring non-routine robust treatment procedures with post-digestion filtration, followed by examination of residual particulate material. Additionally, for beryllium, and likely other poorly soluble materials, particulate reference materials of various chemical forms and size distributions are needed to better evaluate and harmonize analytical digestion procedures. Figure Generation of aerosol particles during machining of beryllium oxide.

Characteristics of Beryllium Oxide and Beryllium Metal Powders for Use as Reference Materials

Abstract Laboratory evaluations of commercially available powders of beryllium oxide (BeO) and beryllium metal, with special emphasis on type UOX-125 BeO and type I-400 beryllium metal, are ongoing to develop reference materials for evaluating analytical chemistry digestion methods and facilitating occupational health studies. Measured properties of the powders include morphology, size, density, specific surface area (SSA); crystalline and elemental composition, surface chemistry, and in vitro dissolution in hydrochloric acid (HCl) (pH 1), phagolysosomal simulant fluid (PSF) (pH 4.5), and serum ultrafiltrate (pH 7.3). The powders were also used to evaluate the digestion and recovery efficiencies for commonly used U.S. Environmental Protection Agency (EPA), National Institute for Occupational Safety and Health (NIOSH), and Occupational Safety and Health Administration (OSHA) standard analytical methods. UOX-125 BeO powder has high-purity and aggregate cluster morphology with SSA independent of aerodynamic particle cluster size, which results in dissolution kinetics that are independent of cluster size. I-400 beryllium metal powder has high-purity and compact particle morphology with SSA that increases as particle size decreases, which causes size-dependent dissolution kinetics (i.e., smaller particles dissolve more quickly than larger particles). The PSF and HCl chemical dissolution rate constants (g·cm−2·day−1) for the BeO powder were a factor of 10 lower than for the metal powder. Concomitantly, the EPA and NIOSH analytical methods, which used aggressive digestion procedures (e.g., microwave-assisted sample digestion or perchloric acid), gave more complete recovery of beryllium from BeO compared to the OSHA analytical method. Our characterization data suggest that these BeO and metal powders hold promise for use as analytical reference materials. We recommend continued laboratory collaborations to evaluate and apply these BeO and beryllium metal powders as analytical reference materials.

Differences in dissolution behavior in a phagolysosomal simulant fluid for single-constituent and multi-constituent materials associated with beryllium sensitization and chronic beryllium disease

Particle dissolution within macrophage phagolysosomes is hypothesized to be an important source of dissolved beryllium for input to the cell-mediated immune reaction associated with development of beryllium sensitization and chronic beryllium disease (CBD). To better understand the dissolution of beryllium materials associated with elevated prevalence of sensitization and CBD, single-constituent (beryllium oxide (BeO) particles sampled from a screener operation, finished product BeO powder, finish product beryllium metal powder) and multi-constituent (particles sampled from an arc furnace during processing of copper–beryllium alloy) aerosol materials were studied. Dissolution rates were measured using phagolysosomal simulant fluid (PSF) in a static dissolution technique and then normalized to measured values of specific surface area to calculate a chemical dissolution rate constant (k) for each material. Values of k, in g/(cm2day), for screener BeO particles (1.3±1.9×10−8) and for BeO powder (1.1±0.5×10−8) were similar (p=0.45). The value of k observed for beryllium metal powder (1.1±1.4×10−7) was significantly greater than observed for the BeO materials (p<0.0003). For arc furnace particles, k (1.6±0.6×10−7) was significantly greater than observed for the BeO materials (p<0.00001), despite the fact that the chemical form of beryllium in the aerosol was BeO. These results suggest that dissolution of beryllium differs among physicochemical forms of beryllium and direct measurement of dissolution is needed for multi-constituent aerosol. Additional studies of the dissolution behavior of beryllium materials in a variety of mixture configurations will aid in developing exposure–response models to improve understanding of the risk of beryllium sensitization and CBD.

Surface area of respirable beryllium metal, oxide, and copper alloy aerosols and implications for assessment of exposure risk of chronic beryllium disease.

The continued occurrence of chronic beryllium disease (CBD) suggests the current occupational exposure limit of 2 microg beryllium per cubic meter of air does not adequately protect workers. This study examined the morphology and measured the particle surface area of aerodynamically size-separated powders and process-sampled particles of beryllium metal, beryllium oxide, and copper-beryllium alloy. The beryllium metal powder consisted of compact particles, whereas the beryllium oxide powder and particles were clusters of smaller primary particles. Specific surface area (SSA) results for all samples (N=30) varied by a factor of 37, from 0.56 +/- 0.07 m(2)/g (for the 0.4-0.7 microm size fraction of the process-sampled reduction furnace particles) to 20.8 +/- 0.4 m(2)/g (for the </=0.4 microm size fraction of the metal powder). Large relative differences in SSA were observed as a function of particle size for the powder of beryllium metal, from 4.0 +/- 0.01 m(2)/g (for the particle size fraction >6 microm) to 20.8 +/- 0.44 m(2)/g (for the particle size fraction </=0.4 microm). In contrast, little relative difference in SSA (<25%) was observed as a function of particle size for the beryllium oxide powder and particles collected from the screening operation. The SSA of beryllium metal powder decreases with increasing particle size, as expected for compact particles, and the SSA of the beryllium oxide powders and particles remains constant as a function of particle size, which might be expected for clustered particles. These associations illustrate how process-related factors can influence the morphology and SSA of beryllium materials. To avoid errors in predicting bioavailability of beryllium and the associated risks for CBD, the mechanisms of particle formation should be understood and the SSA of beryllium particles should be measured directly.

Studies of Beryllium Dispersion and Toxicology in Fusion Systems

Beryllium particles generated in several industrial and research activities were characterized. The purpose of this investigation was to select appropriate aerosols for experiments designed to study the potential health hazards from using beryllium in fusion reactor systems. Aerosols of beryllium metal and beryllium oxide were obtained from an industrial machining operation, from laboratory studies using an electron beam and a laser beam, and from a research fusion device. Samples of stock beryllium metal and beryllium oxide powders were also examined. Respirable size particles were found in all cases. Beryllium particles from powder metallurgy and particles generated from machining beryllium metal were irregular in shape, typical of comminution processes. Particles produced at subatmospheric pressures in the electron beam and fusion devices were also irregular in shape and may have resulted from sputtering of beryllium by the plasma or the electron beam. Particles formed by laser vaporization at atmospheric pressure were branched-chain aggregates with individual particles appearing crystalline in shape.

Crystallite Growth of Beryllium Oxide Powders and Its Inhibition by Adsorbed Phosphate

Low-temperature sintering of beryllium oxide powders from 300° to 1000°C was studied by measuring crystallite growth and changes in specific surface. Sintering is enhanced by the presence of water vapor. Adsorbed phosphate almost completely inhibits sintering up to 850°C, even in water vapor at 10 torr.

Possible health risk from beryllium oxide ceramic rectifiers of 1000 H.P. rail motor coaches.

Beryllium oxide as a ceramic is much more stable than beryllium oxide powder and an unusual use in the form of cups in the rectifier part of the power supply for 1000 h.p. rail motor coaches is described. Its special properties for this particular use are high thermal conductivity and excellent electrical insulation. During trial runs a flashover occurred across one of the beryllia cups in which the temperature was probably in excess of 2000°C and 1·2 g of beryllium oxide was vapourised and lost from the lip of the cup. 18 hr after the incident the rectifier box was opened and although the smoky deposits had settled on the floor, sides and internal structures it is possible that the two engineers who opened and cleaned the box were subjected to an inhalation risk greater than the m.a.c. for beryllium (0·002 mg per m3). Serial clinical examinations, chest radiographs and respiratory function studies on these men have been normal. An experimental test rig was set up to simulate overload and arcing conditions; repeated beryllium air and smear samples on this and in rectifier boxes on trains after runs with peak loading have been taken. The box where the original flashover occurred has been particularly studied. The total amount of beryllium inhaled by either of the engineers most probably did not exceed a few µg but could have reached tens of µg. No harmful effects have been demonstrated.

Molecular size pores in beryllium oxide powders

BeO prepared by thermal decomposition of β-Be(OH)2in vacuo consists of porous aggregates of crystallites ∼30 A. The aggregates are relics of individual hydroxide crystals which undergo a volume shrinkage on decomposition of only ∼30 % of that theoretically possible, and have a density ∼50 % that of dense BeO. Of the intra-aggregate pore volume, only ∼20 % is available to CCl4 and ∼50 % available to N2 and hence there is a substantial volume of pores <∼6 A and <∼3 A. Such small pores render “surface area” measurement from gas adsorption meaningless, cause a small irreversibility in N2 adsorption at low pressures and exhibit measurable He adsorption even at 100°C. Although of comparable molecular size to N2, H2O is able to penetrate most or all of the pores (due to the higher interaction energy to H2O with the oxide surface) and after desorption some of these become accessible to N2. Similarly, H2O adsorption and desorption increases the pore volume accessible to CCl4, and various H2O treatments (including decomposition of the hydroxide in the presence of H2O vapour) lead to a microstructure in which pores <∼6 A are virtually absent.

Paramagnetic Resonance of a Fluorine Centre in X‐Irradiated F19 Doped Beryllium Oxide Powder

AbstractElectron spin resonance of X‐irradiated, fluorine‐doped, BeO powder is studied. Two single resonances with g‐factors of 2.002 and 2.012, and a characteristic doublet resonance, are observed. The resonance doublet, which has a splitting of (760 ± 5) Oe, is presumed to be due to F2−and is absent in chemically pure BeO powder. These results can be explained on the basis of a model in which the magnetic electron is localized in the 3s orbital of F− and interacts with the adjacent Be nuclei. The possible environment of the fluorine atoms is discussed.

The diffusion of tritium from irradiated beryllium oxide powders

The release of tritium from irradiated beryllium oxide powders has been studied by the method of post-irradiation anneal. Over the temperature range 400–660° C, the release is a diffusion controlled process with an activation energy of 24 kcal. The diffusion coefficient of tritium in the two powders studied is given by D UOX = 6.6 × 10 −13 exp − 24 500 RT D MINOX = 7.6 × 10 −13 exp − 24 000 RT . The precautions necessary to obtain reliable results are described.

Fabrication and properties of commercial beryllia ceramics for nuclear applications

Processes and facilities for large-scale commercial fabrication of high purity, high strength beryllium oxide shapes for nuclear reactor and other purposes are described, as are the properties of the shapes so produced. Operating procedures required for ensuring high quality are outlined. As shown, the application of modern ceramic fabrication techniques and equipment, combined with the use of high purity sinterable UOX ∗ grade beryllium oxide powder, has yielded large quantities of beryllia shapes with improved properties at reduced cost. Modulus of rupture values averaging about 30 000 psi were obtained on pressed shapes for the EBOR program, and values of over 50 000 psi have been obtained on small-diameter extruded rods.

Applicability of Routine Methods of Crystallite Size Analysis*

AbstractSeveral methods for the routine determination of crystallite size by means of X-ray diffraction line-broadening have previously been reported. Although these techniques have proven useful and reliable when utilized with the single X-ray diffractometer and instrumental geometry used to originally develop the methods, it was not known whether other instruments would provide similar reliability. Therefore a study was performed to evaluate the applicability of routine methods of crystallite size analysis to other X-ray diffraction units. A series of six beryllium oxide powder specimens, whose average crystallite sizes ranged stepwise from about 35 to nearly 3000 Å, were used to test a number of X-ray diffractometers. By using a predetermined diffraction geometry for each instrument tested, measured crystallite sizes were found to be quite reproducible and well within the limits of experimental error. The testing procedure, instrumental conditions, and individual performance results are presented in this paper.

Fabrication and properties of dense beryllium oxide

Nuclear grade beryllium oxide powders from commercial suppliers may be pressed at temperatures of 1500° to 1900° C and under pressures from 2000 to 6000 psi in graphite dies into a variety of shapes having densities in the range 98 to 100 % of the theoretical value. Addition of 1 % MgO facilitates the process and improves the rate and uniformity of densification. The compaction of BeO as a function of pressure, temperature and time may be described by a flow relation involving a viscosity and a critical shear stress for grain boundary movement. Thermal expansion is isotropic to about 1700° C and is well described to 2000° C by a quadratic function of the temperature. The specific heat of BeO at 1500° C is 0.52 cal/g-°C, slightly above the Dulong and Petit value. From 500° to about 1800° C the thermal conductivity decreases as 1 T , from a high value at room temperature of about 0.50 cal/cm-°C for dense material. A decrease in density of 5 % diminished the thermal conductivity by approximately 13 %. Information given earlier on the creep, elastic and anelastic properties of dense material has been extended, and relations have been employed showing that significant fractions of thermal stresses encountered in practice may be relaxed if given time. Anelasticity due to grain boundaries also appears to confirm the view on flow during densiflcation in hot pressing. A preliminary estimate of rupture strength for completely dense material with grain size of approximately 35 μ is 36 000 psi at room temperature. Lowering the density 1 % reduces the strength about 4100 psi. The status of knowledge of other properties is reviewed briefly.