Showing papers by "Cabot Corporation published in 1987"

Method for deoxidizing tantalum material

Abstract: Disclosed is a process for the reduction of oxygen content in tantalum and/or columbium-containing material comprising heating the material under a hydrogen atmosphere in the presence of an oxygen-active metal.

Tantalum powder process

Abstract: A reduction process for producing tantalum powder wherein a tantalum compound is introduced, in a continuous or incremental manner, to a reactor, during the course of the reduction reaction.

Effects of Nitrogen on the Selective Dissolution of a Duplex Stainless Steel

Abstract: Nitrogen (N) has been shown to exert a beneficial influence on localized corrosion resistance of austenitic stainless steels. With duplex stainless steels (SSs), N plays a dual role of controlling the austenite to ferrite ratio and increasing corrosion resistance. In addition, on rapid cooling from high temperatures, N can form deleterious precipitates in the ferrite reducing corrosion resistance. The corrosion resistance and corrosion modes are quite different in N and non-N duplex SSs. These differences are illustrated for a 25%Cr duplex SS.

Experimental observations of transient phases during long‐range ordering to Ni4Mo in a NiMoFeCr alloy

Abstract: Experimental observations are reported of transient phases which form during long-range ordering to Ni4Mo (f.c.c. Dla superlattice) in the quaternary alloy Ni–19.2 at% Mo–1.2 at% Fe–1.06 at% Cr using electron diffraction. In the early stages of ordering during isothermal annealing, diffuse intensity maxima centered at the short-range order reflections {1 1/2 0}f.c.c. and along 〈100〉f.c.c. directions are observed. Subsequently, a DO22 superlattice is generated from the short-range order state. The coexistence of the DO22, Pt2Mo-type, and Dla superlattices is observed in this alloy system which indicates that these three superlattices have similar energy. With continued annealing, both the DO22 and Pt2Mo-type superlattices disappear, indicating that they are transient phases. These results are not inconsistent with the theoretical treatments of ordered alloys which are based on an Ising model with pairwise atomic interactions. Es werden mittels Elektronenbeugung die nichtstationaren Phasen experimentell untersucht, die sich wahrend des Prozesses der Fernordnung zu Ni4Mo (k.f.z. Dla-Supergitter) in der quaternaren Legierung Ni–19,2 At% Mo–1,2 At% Fe–1,06 At% Cr bilden. In den fruhen Zustanden der Ordnung wahrend des isothermen Temperns, werden diffuse Intensitatsmaxima beobachtet, die den Nahordnungsreflexionen {1 1/2 0}k.f.z. und in 〈100〉k.f.z.-Richtungen zentriert sind. Darauffolgend wird ein DO22-Supergitter aus dem Nahordnungszustand gebildet. Die Koexistenz der DO22-, Pt2Mo- und Dla-Ubergitter wird in diesem Legierungssystem beobachtet, was zeigt, das diese drei Ubergitter ahnliche Energie besitzen. Bei fortgesetzter Temperung, verschwinden sowohl das DO22-als auch das Pt2Mo-Supergitter. Das zeigt, das sie nichtstationare Phasen sind. Diese Ergebnisse sind nicht inkonsistent mit den theoretischen Behandlungen von geordneten Legierungen, die auf dem Ising-Modell mit paarweiser atomarer Wechselwirkung beruhen.

The contribution of personal radios to the noise exposure of employees at one industrial facility.

Abstract: An investigation of the contribution made to an employee's noise dose from the output of personal radios was performed at a North Carolina textile manufacturing facility where the daily time-weighted average sound level (TWA) was approximately 87 dB, A-weighted sound pressure level [dB(A)]. The measured mean equivalent diffuse field output level of the personal radios was determined to be 83 dB(A) with a range from 70 to 98 dB(A). The daily TWA of a typical employee who did not use a personal radio was determined to be 86.6 dB(A), whereas the exposure of personal radio users was 88.5 dB(A)—an increase of 1.9 dB(A). This increase in exposure was estimated to result in 4 dB of additional permanent noise-induced hearing loss at 4 kHz for the 5th percentile (most sensitive portion) of the population after 20 years of exposure beginning at age 20. The study concluded that the additional contribution of the personal radios to the employee's daily TWA did not pose a significant additional threat to their hearing...

On the Origin of EL2 Intracenter Absorption Band in GaAs

Abstract: An alternative interpretation of optical absorption spectra due to intracenter transition within EL2 defect in GaAs is provided. The arguments are presented that states originating from the L-valley of the conduction band can account for the presence of the wide absorption band, the no-phonon line and the observed uniaxial stress splittings. Using the analogy to the DX center, this model presents an explanation for the existence of the metastable state of EL2.

Cosynthetisierte zusammensetzungen auf der basis von bariumtitanat

Abstract: Barium titanate based dielectric compositions having the general formula xx'x''Ti(1-y-y'-y'')yy'Hfy''3' wherein x, x', x'' and y, y', y'' represent mole fractions of the divalent and tetravalent cations and have independent values between zero and less than 0.3, such that the sums (x+x'+x'') and (y+y'+y'') are between zero and 0.4, have a mean primary particle size in the range of 0.05 to 0.4 microns with a very narrow particle size distribution. The products are dispersible so that the mean particle size determined by image analysis and by sedimentation are comparable. The mole ratio of the divalent to tetravalent cations of the coforms is 1.000+/- 0.015 notwithstanding the number nor mole percent of the divalent and tetravalent cation substitutions.

Divalent cation perovskite-type cpds. with controlled particle size

Abstract: Divalent cation perovskite-type cpds. are produced by introducing at least one of the divalent cation hydroxides or oxides Ba(OH)2, Sr(OH)2, Ca(OH)2, PbO or Pb(OH)2 into a slurry of at least one of the hydrous tetravalent oxides TiO2, SnO2, ZrO2 or HfO2 at a temp. sufficient to effect formation of the particular divalent cation perovzkite based co-form. The invention relates particularly to barium titanate and barium titanate compsns..