AD-751 287

ELECTRON QUENCHANT LITERATURE

W. G. i_.rowne, et al

General Electric Company

II~

Prepared for:

Space and Missile Systems Organization

September 1971

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" " III

%I

SAMSO TR-71-309

I-

ELECTRON QUENCHANT LITERATURE

W.G. BrowneG.R. Smookler

General Electric CompanyEnvironmental Sciences Laboratory

Re-Entry and Environmental Systems Divisiot,

TECHNICAL REPORT SAMSO TR-71-309September 1971

Approved for public release; distribution unlimited

Prepared for

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Genera I Electric Company URe-entry & Environmental Systems Division 2b. GROUP iPhiladelphie. Pennsylvania 19101

3. REPORT TITLE

ELECTRON QUENCHANT LITERATURE i

4. OCSCRIPTIV.n NOTES f(ypo of teporand *"rclualive dates)

Final Report3 AIJ T•n1"tSI (eitel fllf.. middle initial, leaf nvmeo -

Browne, W. G. jSmookler, G. R.

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1 ,ABSTRACT L.. ;Mgeles, Cail'ornla 90009"Data on the high tempeiatuze behavior of nolecules which have been previously

identified as effective electron quenchants has been collected. Attention has beendirected to the physical, chemical, .thermodynamic and kinetic data on the oxids/acids oi rl~enium, molybdenum, tungsten and boron. Tae electron affinities of theseacids, 4.I00 kcal/gmrol, are the highest values of any gaseous species in theliterature. An important mode of electron capture involves the process of dissocia-tive-attachment. The existence of two negative 4.,Pns in H/O/metal systems appears Ito be common.

The vapor Prressure of HBt•, n.b.p. 1390 0 K, is too low to volatilize sufficient iboric acid incu a reentry bcunu*.ry layer at high altitudes. It is suggested thatmore volatile bo:on-containing materials, such as cyclic B-N-H compotmds, can beincorporated as an integral part o'f the structure of a Icn temperature ablatorby a process of co-polym2rization. j

FORIAT.- u-

- - -f ~ -- - ' ~ I -- -~ C - - - - -- -1

Security Classification

a'. LINK A L iL.INK CKILY Won)*n ,

ROLC[ WT MOLl[ WT ROLtE WT

1I. Electron QuenchanteS2. Electron Affinities of oxides/acids of

RRe, Mo, W and B33. Thermochemistry of oxides/acids of Re, Mo,

Wi and B4. Vapor Pressures cf oxides/acids of Re, Mo,

~W and BW5. Rheniua compounds

6. MolybCenum compounds7. Tungsten compoumds8. Boron compounds

S2

•ecunty Classification

= L.~-

SAMSO TR-71-309

ELECTRON OUENCHANT LITERATURE

W.G. BrowneG.R. Smookler

General Electric CompanyEnvironmental Sciences Lah;.:atory

Re-Entry and Environmental Systems Division

I F

"TECHNICAL R:POf.AT SAMSO TR-71-309S• September 1971

Approved for puhlc release; distribution unlimited

Prepared forSWpce & Missile Systems Organization

Air Force Systems CommandP.O. Box 92960

Worldway Postal CenterLos Angeles, Califcmia 90009

$I

GENERAL * ELECTRIC*-mu ry& o__•- -"-O 011115

- -"- . . . . . .- . • -l - . -,J l II , • I • i i 6 I

FOREWORD

This report summarizes the work performed on the Strategic Re-EntryI

Technology (STREET-G) Study, Task 4.10 conducted from January 1971 to September 11971 and is prepared under Contract. No. F04701-70-C-0179. The prime contractor

is the General Electric Company, Re-Entry and Environmental Systems Division,

Philadelphia, Pennsylvania. This work was monitored by RISE, Space and Missile

Systems Organization, Los Angeles, California.

This report is approved for public release, distribution unlimited.

This technical report has been reviewed and is approved.

Lt. Col. D. Shover, ESSESpace & M-ssile Systems OrganizationAir Force Systems CommandP.O. Box 92960Worldway Postal CenterLos Angeles, California 90009

I

ii I

Is • -=••••• •. -=.-r/ ••"

TABLE OF CONTENTS

PaeNo.Abstract

I. INTRODUCTION=1 1

II. LITERATURE REVIEW

lRhenium Compounds 3

Molybdenum Compounds 5tTungsten Compounds

6TABEIBoron Compounds

6TABLES

I. Electron Affinities 9

Bond Strengths 10

Equilibrium Constants 10

Vapor Pressure of MoO3(S) itV. Vapor Composition of W03 System

12

VVI. Bf'll'brium Composition Computations 13for Boror Quenchant + Ablation Products

'VIl. React'on Scheme for H/B/O System 14

VIII. Volatxle Boronr-containing Carriers 15

'F

iv

..

Page No.

FIGURES

I. Vapor Pressure of Rhenium Compounds ,.

2. Vapor Pressure of Wake Quenchants 173. Vapor Pressure of Tungsten Compounds 18

4. Vapox Pressure of Boron C-mpounds 19

REFERENCES 20

IV

r

'. ITRODUCTION

The objective of this work was to characterize the behavior of molecules

which have been ideatified as effective wake electron quenchants. A wake quench

candidate is deemed to be effective if it efficiently attaches free electrons to

produce negative ions when .1-e candidate is added in small quantities to a high

temperature plasma centainLa heat shield ablation products. T, interest in

wake electron quenchants stems from their ute in applications related to the

obfuscat-lon ol" reentry o-servaoles. jIn -der to attach rapidly free electrons in a reentry a'latior. environment

a quench ,hould io-'ess all of the fllowing attributes:

1. ,,e cL.t. 2 Vnity,

3. ReA!stance to chemical attack by NW 0 and OHR

4. Large electron attachment coss-section,

5. Be compatibl, with heat shield material with regard thermal,

mechanical, ablative and V & H characteristics.

Experimental electron suppression studies in atmospheric 112 /air ind H2 /N2 0

flames in the ?Aeker burner-microwave cavity apparatus by Dr. R. Carabetta have

identified the oxides/acids of rhenium, molybdenum, tungsten, boron, chromium,

I van.dium, titanium and iron as effectively lowering the free electron concentration iby the processes of either electron ittachment and/or compound formation. e

|I'

I

-I

IT. LITERATURE REVIEW

Chemical abstracts has been searched from 1965 to 1971 for physical,

chemical, thermodynamic and kinetic data on the oxides/acids/ions/fragments con-

taining Re, Mo, W, B, Cr, V, Ti and Fe. The list of electron affinities for the

various quenchants compiled from the chemical literature is cited in Table I.

Several features are noteworthy. First, the electron affinities of the acids,

.100 kcal (4.3 ev), are the highest valaes of any gaseous species in the liiera-

ture. Second, the existence of two negative lons in an elemental system appears

to be co mon. Electron affinities for H2 Mo0 4 and H2 WO4 reported by Dr. W. Miller,

Aerochem, are dependent upon an ac:3ued bonl dissociation energy for H-HMoO 4 and

H-HWO4 of 110 kcal/gmol. The identirication of the negative ions in the chromiUM

and vanadium systems is tentative at this time. The bond strengths of the acids

and alkali salts of quenchants are listed in Table II.

The equilibrium constants Keq, where

A + e~ B + C()

Keq ______c (2)

LA] Le U

and L 3 represents the concentration of the individual species, for electron

attactnment and alkali salt formation are listed in Table III. Dissociative -

attachment and charge transfer are the modes for electron capture. The mc.chanism

- ; for rhenium oxide quenching is thought to be as follows:

Re207 + H2 0 - 2HReO4

HReO 4 + e -- H + ReO4 - (4)

2

= •'"• ... ,•. • . • •--•- , •N • •. • -'-• •~t• • I • '• m • ••;'' • •' ':• • '' -- • ••"- " • -'al-•

It has been suggested by Zavitsanosl that dissociative attachment to Re 2 0 7 ?

occurs at low electron energies, jRe207 + e -- ReO 3 + ReO4 % (5)

At 2800°K and one atmosphere pressure in a fuel lean (R = 0.635) H2 /N2 0

flare the electron suppression effectiveness (by either electron attachment and/or

compound formation) for the candidates on a per atom basis was reported by

Dr. Carabetta to be in the progression Re> Mo> W>B. On a mass basis, the greatest

electron reduction occurred with boron compounds. Particular attention has beenfocused on compounds of Re, Mo, W and B in reviewing the chemical literature.Rhenium Compounds

The pertin -.t species in the H/Re/O system appear to include the following

molecules: HReO 4 , ReO 4 , Re 2 07 , ReO4 , Re0 2 , ReO3 , and ReO. The vapor pressures

2-4of HReO 4 , Re 2 O7 , ReO3 , and ReO 2 are shown in Figure 1. The normal boiling point

Sof Re 2.0; is-6350 K. Skinner has recently studied the major vapor species pre-

sent in the Re-O system using Knudsen cell-mass spectrometry. The sublimation of

Re 2 O7 (s) yields Re 2 07 according to the vapor pressure relation log PRe 2 0 7

- (7.437 + 0.081) 1000 + (12.350 + 0.209) over the temperature range 327-4630 KT

where the pressure is in atmospheres. Mass spectrometry of the vapors from the

Re-ZnO reaction revealed evidence of ReO3 and Re2 06 . Measurements as a fumction

of temperature yielded values for the enthalpies of formation at 298°K of ReO3

and Re206 of -67.0 + 3.5 and -209 + 20 kcal/gmole, respectively. Similar MgO-Re

measurements permitted upper limits to the dissociation energies of ReO and ReO 2

to be established. At 1980 0 K the following values pertain: ReO2 Hf > -5.5 + 5.00|

kcl and Re 0 AHŽ 51.8 + 5.0 kcal/gmol. For ReC, the upper dissociation limit |ginol

is 155 kcal, which is higher than the average bond energy of ReO3 , 144 kcal/bond.,mole

S~3

LS

Brewer and Rosenblatt 6 estimated the free energy function from 298-30000 K

for Re02. 7hey evaluated the electronic partition function, where possible, by

calculating the electronic partition function for the Re 4 + ion or, lacking this,

to calculate the electronic partition function for an isoelectronic ion. The

free energy function of ReO as a function of temperature has also been estimated

by Brewer and Rosenblatt 7 . The electron partition function of the gaseous diatomic

oxide was taken to be the same as the electronic partition function of the iso-

electronic ion V+ as calculated from electronic levels listed by Moores.

King, et al 9 . reported the heats of formation at 2980 K for ReO2(s), ReO3(s)

and Re207 (,) as -107.3 + 0.8, -140.8.+ 0.9 and -301.9 + 1.8 kcal/gmole respectively.

IKazenas, et al 0 , measured mass spectrometrically the vapor phases above ReO3(s)

at 6200K and ReO2(s) at 1030 0 K. They identified the species ReZ07, Pe03 and HReO4

(ostensibly formed from water vapor). Foster has measured the free energy

of formation of ReO2 (s) from 9500-11000 K. The entropy of ReO4" has been calculated

by Krestov 1 2 over a wide range of temperature. Yatsimirskii's rule is invoked,

"the entropy of gaseous species with the same steric configuration and the same

number of electrons but differing from one another by their charge is approximately

the same (to within 0.5 e.v.)". Consequently, the entropy of ReO4" should be

similar to OsO4 . Raman spectra and force constants for OsO4 have been reported

recently13 . McDowell and Goldblatt14 have computed thermal ftinction for Os04

from 273-6000 K. Semenov and Skolkova 1 5 in a mass spectrometric study of the Re-O

system at 1300-1800°K report 4H ' (15000 K) of ReO = -3 + 0.7 kcal/mole. In the

4

reaction of ReO3 and Re207 with s.eam at 370-70 0 °K HReO4 molecules were observed

in the gas phase.

Infra-red and Raman spectra for Na ReO4(s) 1 6 ' 1 8 HReO41 7 (crystalline),

Re20718 have been measured. For HReO4 crystalline

(A) 999 & 990 cm-

(A) 996 & 955 cm"1

(E) 905 & 901 cm"1

HOReO3 has C3 v sy.metry. In Re2 07 the arrangement appears to O3 Re-O-ReO3 with

the Re-O-Re stretch frequencies being 870 & 690 cm-I1 . All alkali perihenates have

broadbands.at 900 cm" Jue probably to monomers and dimers. Drowart, et a1 1 9 have

reported a thermochemical study of the vaporization of sodium perrhenate using a

mass spectrometer. The vapor contains comparable amounts of monomer anti dimer

molecules.

An interesting organo-metallic compound containing rhenium has been synthe-

sized by Sinitsyn, et al20 by extraction of HReO4 with tri-n-octylamine. Tri-n-

octylammonium perrhenate is a colorless, viscous product insoluble in water but

quite soluble in benzene, alcohol and acetone. It decomposed exothermically,

0beginning at.:. u C; first eliminating 3 octyl radicals, second, splitting off

ammonia. This compound may have value for passive quench applications where a

water insoluble, but organic soluble, rhenium compouno is desired. Conceivably,

it could be incorporated as an integral part of the heat shield by the process of

copolymerization with a low temperature ablator.

Molybdenum Compounds

Considerable thermochemical data 2 1 is available on molybdenum oxides/acids.

The aaturated vapor of solid MoO3 , consists cf Mo3 C9, Mo4012 and 1o5015 molecules.

The partial pressures have beeL determined in the temperature range 8000 -IO00°K

5

by Kazenas and Tsvetkov2 2 . These data are shown in Table IV. The formative

equilibrium for molybdic acid is as follows:

Y003(c) + H20 a" e 2 McO4 (6)

The vapor pressure of H2 MoO4 is shown as a function of temperature in Figure 2.

The original work on the bond strength of MoO, MoO2 , MoO3 and the oxidation char-

23 24acteristics of Mo were reported by Drowart, et al and Berkrwitz-Mattuck, et al

Porter 2 5 has measured the vapor phase In equilibrium with Na 2MoO4 by the mass

0spectrometry - Knudsen effusion technique in the temperature range 1200-1800 K.

Tungsten Compounds

The 4ANAF tables21 have a rather complete thermochemical description of the

species W, WO, W02 , W03 , (003)2, (W03 )3 , W3 08 , (W•03 )4 and H2 WO4 . The vapor

pressures of W03 , (iJO3j where n is 2-4, and H2 WO4 are shown in Figure 3. We have

performed vapor composition calculations at 10 2 and 10- atmospheres for the W03

system. These computations at various temperatures are presented in Table V. The

prevalence of the dimer, trimer and tetramer at high temperatures is characteristic

ef the W-0 and Mo-O systems as noted previously2 6 ,27. Porter 2 5 has examined the

thermochemical behavior of Na 2 WO4 at 1200-1800°K.

Boron Compounds

Unider the impetus of the high energy fuels program in the 1950's the neutral

thetmochemistry of species in the B-H-0 system has been investigated thoroughly.

The JANAF tables2 1 contain a complete thermochemical description of the following

gaseous boron-containing species: B, BO, B20, B02, B203, HDO2, H3BO3. Finch and

0srdner 2 8 have recently reviewed the status of the thermochemistry of boron com-

pounds.

6

W!

Measurements in flame system by Jensen2 9 , 3 0 reveal that the two significant

negative ion: in H-B-O mixture are B02 and BO'. Ostensibly, the important nego-

tive ion reactions include the followin6:

B2 03 + H20 W 2HDO2 (7)

HB02 +e - H+ BO2 (8)

EB02 +e OH+BO- (9)

B02- + H OH+B0" (10)

B0 2 " + 0 02 + BO-. (11)

Thermodynamic properties have been generated for BO" using A• Hf* 5 cl

Sgmole, D(B-d) = 215 kcal/gmol; ground state; Be = 1.85 cm-1; 01ý. 0.017 cm-1;

' •)We =f 2000 cm-1;4)eXe = 13.

Equilibrium composition computations have been performed for a boron quen-

chant in the presence .;f ablation products. The conditions examined and the con-

clusions drawn are shown in Table VI. In examining the probable reactions in-

volving the important boron-containing species HB02, B0 2 , BO and B oe posit the

mechanism cited in Table VII.

Figure 4 depicts the vapor pressure of HB02 and B203 as a function of

temperature. It is noteworthy that the vapor pressure of HB02, normal boiling

point of 1390°K, is too low to vaporize sufficient boric scid into the boundary

layer at high altitudes. A survey of more volatile boron-containing compounds

reveals that cyclic B-N-H compounds appear to be attractive, see Table VIII.

Conceivably, an organically substituted borazine can be incor-

porated as an integral part of the structure of a low-temperature ablator, such

as epoxy, by a process of copolymerization starting with a halogenated borazine.

7

Seshadri et al 3 1 have examined spectroscopically the structure of sodium

metaborate. The propensity to form NaBO2 in sodium-contamLnated systems is

quite pronounced since D(Na-BO2 ) is 114 kcal/gmol.

Zavitsanos' has reported an attachment cross section for HBO2 (reaction 8)

of 3 x 10i17 cm2 . Combining the cross section with the mean thermal speed of the

electron yields a rate coefficient k8 = 3.7 x 1014 cm3 /gmol sec at 1373 0 K.

8I

1*

TABLE I

ELECTRON AFFINITIES

-Electron AffinityIon Formed kcal/gmol Techniqu,'. Reference

B02- 94 ESP, microwave 298 mass spect. 3

BO" 58 mass spect. 3

MoO4- (98) mass spect., ESP 4

M003" 60 mass spect., ESP 4

SW0 4 (96) mass spect., ESP 1

W03- 73 mass spect., ESP 1

HCrO3 mass spect., ESP I

CrO2) ? mass spect., ESP 1

O? mass spect., ESP I

HV03- ?" mass spect., ESP I

REFERENCES

1. Dr. W. J. Miller (Aerochem), Wake Quench Technical Exchange Meeting, Aerospace/SAMSO, San Bernardino, Nove,-er 6, 1970.

2. Jenwcn, D. E., Tra.-s. Farakay Soc., 65, 2123 (1969).

3. Jensen, D. E., J. Chem. Phys., 52, 3305 (1970)..

4. Jensen, D. E. and Miller, W. J., Thirteen Symposium (International) onCombustion, U. Utah, August 23-29, 1970.

5. JANAF Thermochemical Tables.

9

TABLE II

-BDND STRENGTHS

Dissociation Energy (tO°KBond

kca 1 /lmol. Reference

Na-BO2 114 5H112 17 5

K-B02 114K-HM°04 421

H '-HM°04 1 O14

4TABLE III

EQUILIBRIUM CONSTATSReaction

K 'qK(eq)

0 2 + e = + O 21 5 0 0 e x p ( - 1 0 , 0 0 0 / T )

H2MO4 + e- f + H+oR4- 24 exp (S001T)lt2WO4 + e- - H + LV04- 25 exp (13001oT)K + HB02 = H: + 1K302

37 exp (-2500/T)K + ý2°°4 " + =404 3.5 exp (3500/T)K + !H25O4 =H +-M=W4

4•.0 exp (2900/T)

K(2000°K)ý2UzO3 + e' ,= CrOý3- + H 2.0

83VO4 + e- = H2v04- + H 1.8R + H2vo4- =Hvo3- + H2o 50"R + Hcro3- --cro2- + H20 10"H+ HW°4- w0•3- + H20 15R HMoO4- =MOO3" + H 20

040

•=• • •.•.... o.- ,. ..- = • • •••- fi•-••. • :_• ::•"•• ....... _ _. . ... ••_•....••-T • i - ,•2. ."

TABLE IV

VAPOR PRESSURE OF 03O(sO

800 < T < 1000 K

LOG P (To30 - 14.39 1M FIG

LOG P 0{o4012) 17300 16.88 HMHG

LOG P (Mo5015) 20240 19.47 M HGT

SATURATED VAPOR COMPOSITION, 7

T, °.0KMos9 Mo4012 14°5015

800 75.5 23.2 1.3

850 65.5 30.0 4.5

905 54.5 37.6 7.9

950 45.7 42.5 1 11.8

L600 36.0 44.5 19.5

IiTAKE VVAPOR COMPOSITION OF W03 SYSTEM

Press 1.0 x 10"2ATM. MOL FRACTIONST9K NO WO2 W03 W206 W309 W4012 02

1200 0 0 1.65-10 2.292-4 2.393-1 7.604-1 1.068-6

2000 2.68-10 1.527-6 4.992-4 5.137-1 4.350-1 3.349-2 5.749-3 j3000 6.184-3 1.273-1 1.186-1 6.611-1 3.081-3 7.255-6 7.446-2

S~Press fi1.0 x 10-4 ATM.

ST°K I#0 IWO? W03 W206 W/309 W4012 02

E1200 0 1.76-15 4.56-9 1.787-3 5.264-1 4.718-1 8.322-6

2000 1.977-7 1.487-4 6.407-3 8.669-1 9.651-2 9.767-4 9.749-3

3000 1.055- 4.619- 9.154 - 3.937- 1.':1-7 2.573-12 3.369-1

212

SNI

EQUILIBRIUM COMPOSITION O3MPUTATIONS FOR BORON QUENCRANT + ABLATION PRODUCTS

C2 H2 + 02 + 1% HB0 2 + TRACE CESIUM

0.5 44 R - 2.4 20000< T - 40000 K

0.025 < p t. 0.1 ATM

ICLUDED HB2, B02, BO, B203, B202, HBO, B, B02", BO_' i+, RB6+

GENERATED DATA FOR BO : £ STATE D(B-O0) = 215 KGAL

USED E.A.(DO2 ) = 94 KCALI'AOLI

E.A.(BO) = 57.5 KCAL/GOLE

CONCLUSIONS

1. HEO2 , B02 , BO AND B ARE THE IMPORTANT BORON-CONTAINING SPECIES.

2. B02- IS THE ONLY IMPC.TANT NEGATIVE ION.

1.1

TABLE VII

REACTION SCHEME FOR H/B/O SYSTEM

HBo2 + H--&H2 + Bo2

EDo2 + 0---OOH -f O2

HBO2 + OH- H20 + 0O2

BB02 + -- H + BO2 +M

B02 + M--OR + WO + M

B2+ H-01OH + DO

302 +M 0 BO+M

BO + H--OH + B

DO + M-O + B + M

14

-- -j-- . ,,,, -..... .- - w

TABLE VIII

VOLATILE BORON-CONTAINING CARRIERS

1. The vapor pressure of HBO2, b.p. 1390°K, is too low to volatilize sufficient

boric acid into the boundary layer at high altitudes.

2. A survey of known boron compounds reveals that cyclic B-N-H-X compounds have

boiling points, .v50-150°C.

H 0~p-N'8X-H m.p. -58°C

! iSH-8 8 -H b.p. 55°C

BORAZINES(BORAZOLE)J

3. B3H6N3 is thermally stable at 5000C. B3H6N3 reacts with 02.

Beat of Combustion Kcal/G

SB •H6 19 2B2 6

R H9 17.5

B0 16.7

B3H6N3 6.88

4. Cyclic B-N-H-X compounds polymerize to yield polycyclic molecules whose

melting points are 100°-2000C higher than the monomer.

m. p. 27-30 C I..2 -6.

15

momo

40

C) C40 C0

CC)

00

Co:

r44

0

00

I I

(w.tv) aufissaud uocivAa.o fXri

16 I

T (OK)

2000 1500 1000 5002 I

01390 1K o0 0 K 6 K

W -0SYSTEM '4< K-2 I %D< 4 R27

HB 2 H 7

i -s Re 02(•M\2S-40

-2 HBO2 2c 4B0

3�Re 3(s)

S-20 - ~ ~B2 03 (•20

Re 0 2(s

HO2W4

-10

>-12

"3(c) 2 2-0 BO14B

- 2I I0.0005 .01

10.002

•. {,Figure 2. Vapor Pressure of Wake Quenchants

i 17 .( +

7_/2 I

-1 1() s

a... ~~ ~M 0=-- H2---- -- --- --

0T (K)

2000 1500 1000 5002t

0W-0 SYSTEM.. 1320 °K

1 HW

24%

2 (W03O

-6 3 (WO)3

(W(WO)3E- -84

0 -12

0 -14

0 S~W-0 SYSTEM

-16 Ho""2W0 ( W04 2000 1500

-18 W0 3 (L) (W03 ) 2 (W03) 3 0.433 0.132-18 -- 3.2 W03 () (WO3) 32

4. 4 W03 ( (W 3 ) (W 3 3 0.512 0.790-20 5. WO )W0V3) 4 0. 0.078

-22 I ,0 0. 0005 0.001 0.002

l/T (K)

Figure 3. Vapor Pressure of Tungsten Compounds

18

I

0T (°K)

2000 1500 1000 5002

~1390 K

0HB 2

!V-22

-43

B2 0 1-620HBHB2

S -8 -

w-10

S-12

S-14

08-16 - . HB)O HB02

2 (c) 22. 1/2 B0 +)1/2 H0-B0

203 (t) f20 2-18 - 3. B 2% (t) !B203O

-20

-220 0.0005 0.001 0.002

1/T (oK)

Figure 4. Vapor Pressure of Boron Compounds

19

REFERENCES

1. Zavitsanos, P. D., "Electron Attachment and Thermodynamic Studies of Electro-philic Compounds," Technical Report SAMSO-TR-70-318, June 1971.

2. Glemser, 0., Muller, A., and Stocke, U., Zeit. Fur Anorg. and Allgem, Chem.,Band 333, 25 (1964).

3. Battles, J. E., Gundersen, G. E., and Edwards, R. K., J. Phys. Chem. 72,

3963 (1968).I 4. Smith, W. T., Line, Jr., L. E., and Bell, W. A., J. Amer. Chem. Soc. 74,4946 (1952).

5. Skinner, H. B., "Mass Spectrometric Studies of Gaseous Oxides of Rhenium andof the Lanthanum Trifluoride Dimer," U. California Radiation Laboratory Report19645, 1970.

6. Brewer, L., and Rosenblatt, G. M., "Dissociation Energies of Gaseous MetalDioxides," Chemical Review 61, 257 (1961).

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