|Return To Program Contents Page|
Room: Salon 6
Location: Clarion Plaza Hotel
Session Chairs: Beverly Aikin, CWRU-NASA LeRC, 21000 Brookpark Road, MS 106-5, Cleveland, OH 44135; Thomas Battle, DuPont White Pigments and Mineral Products, Edge Moor Plant, Edge Moor, DE 19809
SYNTHESIS AND PROPERTIES OF POTASSIUM HEXATITANATE WHISKERS: Zuomei Jin, Lisheng Wang, Jifen Huang, Dept. of Metal Materials, Chengdu University of Science and Technology, Chengdu, P.O. Box 610065, Sichuan China
The optimum conditions for synthesizing potassium hexatitanate whiskers (hereinafter called as PHW) were systematically examined using fast-cooling melt method. The intermediate and final products were determined by x-ray diffraction analysis, SEM and differential thermal analysis. A synthetic mechanism of PHW by melt method was proposed. The physical properties of obtained PHW were measured. A ratio of whisker length to whisker diameter is preferably 50 to 200. A PVC resinous composition containing 10-30% of obtained PHW is believed to show that the mechanical properties, heat resistance and abrasion resistance are much improved. For example, the tensile strength is 1.9 times larger than that of PVC resinous matrix and thermal deforming temperature is raised from 84°C to 120°C.
SYNTHESIS OF TI(N1-xCx) WHISKERS: Niklas Ahlen, Mats Johnsson and Mats Nygren, Department of Inorganic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden
A route for synthesis of Ti(N1-xCx) whiskers (0 ¾ x ¾ 1), in a yield of 70-90 vol% has been established. The whiskers are ¾ 1 µm in diameter and 10-30 µm in length. They are straight and have smooth surfaces. The Ti(N1-xCx) whiskers have been synthesized carbothermally via a Vapour-Liquid-Solid (VLS) growth mechanism in the temperature region 1200-1600°C. The starting materials consisted of TiO2, C, an Ni-catalyst, and NaCl used as precursor for Cl. The synthesis of TiC whiskers are made in an Ar (g) atmosphere while the Ti(N1-xCx) whiskers are prepared in N2 (g) which besides preventing oxidation also acts as nitrogen source for the whiskers. The main impurities in the whisker product are minor amounts of unreacted carbon, oxygen and remnants of the Ni-catalyst. The VLS-mechanism is complex and involve formation of gaseous TiClx species, which are transported to the catalyst. However, the overall reaction is a straightforward carbothermal reduction/nitridation reaction.
RECEPTION OF CERAMIC FIBERS FROM JOINTLY PRECIPITATED HYDROXIDES: Maximilian N. Kopylovich, Alexey K. Baev, and Alexander A. Chernik. Department of Analytical Chemistry, Byelorussian State Technological University, 13a Sverdlov Street, Minsk, 220630 Republic of Belarus
The coprecipitation method is perspective for reception of ceramic fibers. The essence of the method consists of a joint precipitation of hydroxides or salts with the subsequent branch, washing, drying and heating of a precipitate. The joint precipitation of hydroxides has a number of features. The hydroxides of metals can interact at the moment of a joint precipitation that results in occurrence of solid solutions. It was proven that in many systems containing by 2 and more hydrolyzed metal ions under certain conditions the formation of heteronuclear hydroxocomplexes occurs in solutions. The further interaction of specified hydroxopolymers causes formation of complex polynuclear structures reach the size of colloidal particles. The latters are X-ray amorphous and they are a prestructure of the future material. Such prestructure can be transformed into a final crystal product at lower temperature and smaller duration of heat treatment in comparison with oxide technology accepted in manufacture of ceramic fibers at present. It will allow to expand a palette of ceramic fibers and to lower their cost price.
MEASUREMENT AND MONITORING OF AIRBORNE PARTICLES--TECHNIQUES AND REGULATIONS: Martin Harper, PhD, SKC, Inc., 863 Valley View Road, Eighty Four, PA 15330
Measurement of the nature and number of suspended particles in breathing air is used in health effect studies and to demonstrate compliance with government (OSHA, MSHA, EPA) regulations. The characteristics of the aerosol (e.g. fibrous, biological, metaliferous) and the requirements of the regulations govern the choice of technique. Three health-based size distributions are recognized (inhalable, thoracic, and respirable), but the definition of the fractions has varied over time. Current size separation and sampling equipment for aerosols includes impingers, elutriators, filters, impactors, cyclones, and various direct-reading instruments based on, for example, light scattering, or particle motions. Factors which influence the choice include sensitivity, accuracy, portability and ease of use, calibration requirements, cost, and government regulations. Some instruments are well matched to the health-based size fractions, and others less so. The history and current state of regulations will be reviewed, and the types of instruments will be described.
DUST EXPLOSIBILITY PARAMETERS FOR METAL POWDERS: C. James Dahn, Safety Consulting Engineers, Inc., 2131 Hammond Drive, Schaumburg, IL 60173
The processing, manufacture and handling of powdered metals can employ widely varying process conditions which affect the potential for ignition, the explosion output and resultant collateral damages. This paper presents an overview of the factors (i.e., particle size distribution, particle cloud density, degree of turbulence, oxygen content and ambient temperature) which impact the minimum ignition energy requirement and explosive output of metallic powders. Processing conditions which strongly affect the output of an explosion, as measured in terms of maximum pressure achieved and maximum rate of pressure rise, are presented. Parameters influencing the energy requirements for ignition of an explosion will be emphasized. Dust cloud characterization under controlled conditions can be utilized to predict and, when necessary, to minimize powdered metal processing hazards.
CONTROL OF BERYLLIUM POWDER AT A DOE FACILITY: Gerald C. Langner, K.L. Creek, R.G. Castro, Industrial Hygiene Section, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545
Although only a small percentage of the general population and work force will face exposure to airborne beryllium, the effects of this exposure to the individual can be permanent and devastating. One effect, chronic beryllium disease (CBD), a granuloma and fibrotic lung disease with latency, can be developed after inhalation exposures to beryllium. In this study, the principal investigators conducted a hazard characterization of the beryllium powder plasma spray operation at Los Alamos National Laboratory using side-by-side, laser-induced breakdown spectroscopy (LIBS) sampling with conventional industrial hygiene techniques. We used results of the sampling data to reevaluate work practices and engineering controls associated with the plasma spray operation. As a consequence, work practices have changed, and new engineering controls and facility design changes will be implemented. These revised engineering controls include modifications to the beryllium spray chamber and design of auxiliary equipment used during routine spray chamber maintenance.
|Search||Technical Program Contents||1997 Annual Meeting Page||TMS Meetings Page||TMS OnLine|