CA1139827A - Oxide cathode and method of manufacturing powder metallurgical nickel for such a cathode - Google Patents
Oxide cathode and method of manufacturing powder metallurgical nickel for such a cathodeInfo
- Publication number
- CA1139827A CA1139827A CA000317186A CA317186A CA1139827A CA 1139827 A CA1139827 A CA 1139827A CA 000317186 A CA000317186 A CA 000317186A CA 317186 A CA317186 A CA 317186A CA 1139827 A CA1139827 A CA 1139827A
- Authority
- CA
- Canada
- Prior art keywords
- nickel
- cathode
- support
- powder
- strip
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/0433—Nickel- or cobalt-based alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/13—Solid thermionic cathodes
- H01J1/14—Solid thermionic cathodes characterised by the material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
- H01J9/042—Manufacture, activation of the emissive part
Abstract
ABSTRACT
By manufacturing the support of an oxide cathode consisting of powder metallurgical nickel in such manner that the reductor for the emissive coating consisting at least of one alkaline earth metal and oxygen is distributed inhomogeneously through the nickel and forms islands having a high reductor concentration in the surface of the support, an oxide cathode is obtained having a low sensitivity to poisoning of the cathode at the beginning of the operation thereof, and electric discharge tubes rapidly having good emissive properties can be manufactured with said cathodes.
By manufacturing the support of an oxide cathode consisting of powder metallurgical nickel in such manner that the reductor for the emissive coating consisting at least of one alkaline earth metal and oxygen is distributed inhomogeneously through the nickel and forms islands having a high reductor concentration in the surface of the support, an oxide cathode is obtained having a low sensitivity to poisoning of the cathode at the beginning of the operation thereof, and electric discharge tubes rapidly having good emissive properties can be manufactured with said cathodes.
Description
:~398~7 3-10-78 1 PH~ 77-012 Oxide cathode and method of manufacturing powder mel.allur-gical nickel for such a cathode.
The invention relates to ~ oxi~7e cathode comp.Lisin~
a cathode support which consists substantial~y of po~der metall.urg;.cal ni.ckeI which nic~el comprises a reductor :rOr the emissive coatlng which coati~.~ is provided on the support and which consists of ~ compound of at ].east one ~lkal:ine earth metal and oxygen, in ~hich support a heating element is provided : The in~ention also relates to an electric discharge tube ~taving such an oxide c.athode al~d to a method of ~nanufact~ring ~owde:r metallur~rical nickel for the ~support of such an o~ide cathode.
Such oxide cathodes have a very wi.de fiel(l of ap~lic~tion. They may be used, for e~-ample, ;n elect.roll tubes, di.spl.ay tubes, T.V. oamera. tubes, transttlittin~r tu~es, klys~on~, ma~netrons, and the like.
Such an oxide cathode :is known from Pbllip* ReseclrL^h : ~eports 26, 519-531~ 1971. The oxide la-yer descr:i.be~ :i.n I saic. reports comprises in-ter alla BaO (bari.um o~i~e). T}~e reductol used consists of one or ~cre oi` the elements .~l, C, Mgr, Si. or Zr, whleh el.ements reduce a part of the 13~.0 to Ba. Th~ reductlon of the BaO takes pl.ace :in t.llat t:~.te ~educto:r ~i~fuses from tht-.~ nick.el S11~0:1'~ stril~ in th.
l~yer o~ B~O on the ~upport u:nder ,'he inf`~ence c~f tlle thexltla1. eneI~ry of tlle hecater elemell.', and re~llce~ $1~ere 2S th~ B~O to free ~ rhic3l d.:ifru~3 to the ~1rf~ee oi` the , ' q~
.
3-'l0-'7~ ~ P~Q 77-~lZ
, layer of Ba0 and f`orn]s -cherQ a l~onoat.om:ic surface layer o.t`
¦ low work function.
¦ Cathode support stri.p consistin~ of nicke~. containingr an acti~ator element such as Al, C, Mg, Si or Zr, has bee made by a powder r~etallurgy method in ~rhich ~I mixture o~`
the consti.tuent powders is compressed to form a blocl~, the ~ compressed block is sintered, ~nd the sinccred :Lllgot i5 f rolled. 'l`his method recluiros a. po~rerful press, ~rhich is ¦ expensive, and the centre of tlle ingot is rclatively porou.s.
'~ l0 It i5 necessary to si.Il1;er ]~rge in.gots at :relati~rely higl temperatures :~or a lon~ -timeS Por examplo at 1300C ~or 48 hour~, in order -to recluce the porosity of the cellcre of the ingot. However, such a process is not suitable h-ithout taking troublesome precautions .such as encaps~ .t;:ing the ingQt when the activator element i~s ~agllc~ium, ~rhich i~
volatile and has a bolling ~oint o:f 1'l00C.
~ isadvan.tagre of kn.own ox;de cathoclcs UsiIlg known .~ catllode supr~ort nickel strip is that the quan-tity of` free ba:riun~ available when the cathocle is first operated i.5 20 reduced consi.d.erably by ga3 residue~ in the electrQn tube' in which the cathocle is used,'~hich residues form c0l1lpouuds.
' w:it'h the free bariun~. Thl3 is terrlled tlle poisoi~lr!g of thc cathodeO Such poisoni.n.g gas r~sidue~s are :formed not only as a result of i.nsuffic:ient evaCuati.Qn Or or leaks in the 25 elect.ron tube ( a ~rood vacuum of` 10 7 mm llg still meanC
10~9 mol o~ ~as I)er cm3) 'lut ~llso Qs a re~u'lt of hoati~
i and evvlutio.rl o~ ga.~e~s I':rom componotlts ill tlj.e tube. More-.3 over, the cat'hode~poisoning gases can be ~ormed UpO-l im~act of electrvlls ~ith materials and thc g~s may b~ rcleased 30 from the glass ~ra.ll o~ the electron lub~ A3 already said, ~ ca-thode poisoni.ng occurs i.n particular at the begir~ning of it the opcration of the cal.hode so t~ t the tl~bc i.n which sai~
, cathode ic;ll.sec' i.nitially shows a pOOI Operati.Orl as a j resul.t o~ a poGr cathode em-ission.
J 35 :C-I ;.s the-leroré~ the o~ject'o:~ the in~rention to pro~r:ide an oxicle cat~lode whlc~rl at the~ beë~inn:i.r~ of` the . operatio~l of said caihocle i.s cc~ls:iclerabl~r les_ xe.ls:iti.-~-c to poisonirlg ~ncl which, whe:n used i.n a tubc, ra~ y ~chic~re~
, . ~ .
:1~39827 ¦: 3-10-78 3 PHQ 77-012 I
j ' a good emiss:ion.
i ~ccording to ~he invention, such a cathode of the kind descrlbed in the I`irst ~aragraph is characterized in ! that the reductor i 5 distribut~3d i.nhonlogeneou~ly through the nickel ol` t~le ~upport a.nd Iorms islailds ha.~-.r;g a high reductor concentration ill th.e surface of the support.
The activator element diPfuses from th.e intelior of the cathode support as a reslllt of a conc~ntratlon gra~ient ~ of the aGti~ating elemt3nt being set u~ between the oxide-T 1U bearlng sur*ace o~ the cathode .support arld tlle inte:rlor of ¦ the cathode s~pport as a result of a reaction between bari~
oxide and the activati~lg element at the surface o~` the cathode support. Thus free barium -which was lost by reacticn with gas residues in the electron tube is replaced.
~ 15 Diffusion occurs at acceptable~ rates as a result of` the i high temperature of -the ca-thode support duriIlg oparation of the cathode. The nickel coating surroundj.ng the i particles oP an allo~r of` ni.ckel and an activator element ma~.es it possible to si.nter the compacted strip at high 20- speeds and low temperatures, and makes the sintoring process casier to control.
When magnesium is used as an activator el~3ment, it is introduced into tne powder mixture in the form of nickel-~: control particles of` a ni.ckel-magnesium alloy, for example 25 containing '15~, b~ wei~ht of magnesi.um co-tecl w:;tll ~uch a th.icklless of lliolcc~l t'hat the m~gne,s:Lum ~ontent. of tho l eoated partlo:L~ , 2$ hy we:L.~,rht,. B~r lntroducing the ¦ magnesium ln this manller, the ni.ckel-mag-.resium alloy i3 protected Prom oxi.dation by traces oi` o~rgen which are 30 inevitab~.y present in the si.nterlng ~1,mos~here. I~ is oon~en.:i.enl; to i.ncorporate al.umini,urn when used in tho nlix-tu~
in the ~o-Lm oP a nlccl~,ol--aluminlu.n al3.oy contai.nin~, f`or ex~mple 5~ ~y weight c.P .~luminill~. When the .lc~i~r~to:r el.ement i..s ma~n~sium, -the magnesium contenl o~ e n.cliol.
3~ .strip m~y b~ f'rom 0.03 to 0015,~'. by weightO kT~len tlle nic~e:L
st,r:ip i;lClU~ alumlni.~in-l, t~e alu:nir.iulTI c:ontent o~` the nicl~.el strip ma.y be f':rom 0~01 t~ 0.10G~ we~
3-10-78 4 P~IQ 77-012 Comn1ercially available carbonyl nickel powder consists of more than 99% by weight,of` nickel, together with trace impurities. Small quantities o~ other elements, such as tungsten, may be included in the mixture in order to improve the n1echanica:L properties of the nic1~elst.:rip.
The nickel-coated particles of the alloy of nickel with an acti.va1;or element a.re thorou~hly mixed with carbo- -nyl nicl~el powder and any ot'her ingredients of the mixture~
A strip i.s -then rolled from the mixture, the th:icknr3ss of`
th.e compact,od .strip bei11g ~roverned by the apparatus avallable. Thc compact~d st,rip is the~ sintered, and the sin-tered strip is then rolled so as to reduce the thickness of the stri.p to a desired value~ l`he rolled strip ma)r be a3lnealed ii` desired.
- l5 An embodiment of the invention ~ill now be described with reference to the drawin.g in ~hich Fig~lre 1 is a sectional clevat:ion of an oxide cathode, I~`igur~ 2 is a sectional elevation of a kno~rn cathode support bc3aring a bariulr.-calcium-stron1;ium oxide layer, ~igure 3 is a sectio3lal elevation of a cal,hode support nickel strip made by a method a~cording to thr_ invention bcaring a barium-calcium-strorti1lm o~ide layer, Fi.gure 4 is a plan ~rie~ of a disc of a cathode support. ~ickel strip made 'by a method according to the invention.
'Fi~ure 5 is a. schemal;ic slde cl.evl.tion of an ~p1~ara tllS usc3d to makQ a sintered compncted strlp by ~ m~thoc~
a~cording to the inventlon, and Figure 6 is a plan vie~ of the rollers of t'.he apparatu~ sh.o~n in Fi.~ure 5.
Fi~,r~lre 1 shows an oxide~ cathode consistin~ of a support 1 made of the strip made by the metr.od described w:itll rcfereJ;ce -to Figrures 5 and ~ ~ecllred -to cl cathode s'ha.~ 2. A heatcr ele-rllen~ ~ i.s sit:uate~i below t,he suppor~
1. The s~ ort. 1 bears a laye- ~ ol` (BaCaSr~0. This layer 4 is o1~taiil~d ~ spra.yl~g .1 suspens:ion oi' b~rium-ralciu~
: st.rontium carl~onat~ onto the support 'I and con.verti11g t'he CarbO31ate il~CO (~aCa~r)0 by hea,.tir~
1~398Z7 i 1 3-10--7~ 5 ~HQ 77-012 i l~igure 2 sllows a part of a p.rior art support 1 I bearing an emissive layer 4. This prior art support was produced from a casting of an or a high temperature sintere~
powder metallurgy alloy of nickel ancl an ac-tivator element 5 which is shown as dots homogeneous1y distributed in t~le nickel of` the support and the activator e]ement diffllses into the emissive la~er 4 durin.g ope:ration of the ca~nc,de.
en the emissi~re layer 4 ha.s been F~olsonec1~ the I~aO i.n this cathod~ is not reduced suffi.c.i.ently ral~idly so that th~ emission of the cathode cont;inues at a lower level than was t~le case before poisoning.
Fi~ure 3 shows a part of the support 1 according to the i.n~entlon bearing the emissi.~Te layer 4. Th~ activator elemel1ts 6 Mg and Al are present in the n~ckel of the sup-i l~ port and at the surface of the support in a loca].l.y ~
conceIltrated form so that the supporting consisting of po-~der raetallurgical nicke]. colnprises I.i. 0.05 to o.oc~
by weigllt of Mg an.d from 0.01 to 0.05~ by we~ hi; of A.l~
~ A.s a :esult of thls being localiy concentrated it initially :~ 1 20 di.. ff1lses con.siderably more rapidly i.n-to the emissive layer4 a.nd can rapidly replenish the Ba which has been lost ;-lS
a result of poisoning.
Figure 4 is a plan view of ~.he support 1 according to tlle irl~cntion in which the islands 6 havin~ a high con.c~ntrati.oIl of activa1;or elemen-t are si1.uated. l~
be ob~i.ous that the cat;llode n.iclcel may also be used in other cath.od.e oonstrllctio.ns, and ~cl;i~at()r olcrncnts an~l 1' a.lka].i.. ne earth motal oxidos other than those de~cribsd may b~ usedO
Now a method for mallllfactuLin~ n1etal].l.lr~ical nic1~l i for su.ch a cathode wi1l be describ6d.
A magn~sl-ml-nickel a.lloy corl1;a:inin~ 15,~, by wei.gh1; o:t`
j ma~lles:L~ Ti in the .forl~ of lu.nps was crushed9 ~round and 1 s-ie~Je~ I;he matsri.al p~s~in~ a 350 mesh (mcshe~s pcr illCI' )3~ s:ievc beir~l~ coll.ected. ~rhi.5 minu~ ~50 mesn IriatcriLtl ~.~as coated w:ith a t.~ic.n~s.s of ni.ckel suc1~. tha~ t~e Inclg-rl~s1.u~
content Or t~;le coace~ particles 1~a; 2~o ~y ~Tei~ht. Thc part-~c.~os w~re coat;ed ~i.th nic~;~l in an autoc1ave by tlle .
: .
,, :, .. ~ .. .. . .. . . .. .. . ........ , .. ~ .. ... .
1~39827 3- iO-1 ~)7~ 6 PHQ 77-012 reductiLon of an aqueous ar~nonlaea . solution eol~taining n.~ekel. sll~phate and amrllonium slllpha.t~ heated to 175C, the au ,;oealve eontai.ning an over-pressure of 350 lbs/in2 o:f h-~7drogGn.
1~ master Dlixt;ure consis ting oI` equal weigh.ts of tungsten powder and carbonyl. nick~al powder having average particle ~sizes of 3/um was prepared. All alunl-lniun~-nlcke].
(52/~l~3 by weight) ~:~owrlGr was sleved through a I-()O mesh sieve and t.he rni.l~us IIOC mesh :fraetion w~s use-l.
A m~ tu~e \~as pri3parod consistilng of 80 g o:f thc3 ll:icke~ l-coa ted magne~sillm-lli.cke:l. alloy parti.cles 1 . (:'j g C!:~ th~a n1intl.s 1loo mesh alumillium-nic3~el. alloy powder 80 ~ o:L` th~ tungsten arid ea-.rborl~_ niekel master mix-l;ure 1 ælTO g o:E` earbonyl nickel po~del .
This mi:~ture eor~a:Lns 0.08 ~ llg, 0,04 % by woig~nt Al arl.d 2 G~ y we igh t W .
Re:ferring -to l?igures 5 and 6 o:L` the dr~3wings, po~rder mixture 1 0 was fed i~to a h.opper 11 I`rc,m l~Thi.Ch the powder pQ,ssed i.lltO a o.6 rr!rn wide gap 12 bet~eerl t~-To 15G mn~
~liameter rollers 13, 14 xu.nning in th(3 hori~,ontal plan~.
The eoJrpacted stri.p 15 l~as.sed over suppor-t rollers 16, 1 ~
and læ b~3fc-re enterLn~ a mu:Erle tube 19 o:f a muI:E:le furn~ce ZO l.n whieh the strip 15 l~as si.nte:led. .Puret dry h5~clrogre wa~ passed throuT~r~h th.e muf:fle ttub~3 1~3 ~llcl t.h~ st;r.ip passed l;hl ou~r,h t;he lu:r]lace at ~ueh a r at.c~ t llat: a peak tenll~t3ral:uro o:~ 1050~C wa~s appli.ed :Eor 3 m:L~ .tos, Thc s-lntc3r~ed s~tr.:ip 21 em~r~in~ rrorn ~t~ e n~ f.fle tUb? 1~3 w~
J;~ 011~ 1 Go(,) Itlm d:~arl~et~ SpO~ I 2'> ~ ~rll~3 sillte c`e~' s~ i ~as 0. 7 ~ t~li.C~:' arld ~ra~; SUbs(?r~L~:(37:ltLs~ I`OLleCi to ~i~e a fll,xl thlcl~ne~ of 100/u~n~ Thi.~; 100/un; strip I a~ nsi3c~ lo rnali.f3 t~ 3 oxi.~r2 Cat'rlOQ'3 suppox~t~
., . ~ . ~
The invention relates to ~ oxi~7e cathode comp.Lisin~
a cathode support which consists substantial~y of po~der metall.urg;.cal ni.ckeI which nic~el comprises a reductor :rOr the emissive coatlng which coati~.~ is provided on the support and which consists of ~ compound of at ].east one ~lkal:ine earth metal and oxygen, in ~hich support a heating element is provided : The in~ention also relates to an electric discharge tube ~taving such an oxide c.athode al~d to a method of ~nanufact~ring ~owde:r metallur~rical nickel for the ~support of such an o~ide cathode.
Such oxide cathodes have a very wi.de fiel(l of ap~lic~tion. They may be used, for e~-ample, ;n elect.roll tubes, di.spl.ay tubes, T.V. oamera. tubes, transttlittin~r tu~es, klys~on~, ma~netrons, and the like.
Such an oxide cathode :is known from Pbllip* ReseclrL^h : ~eports 26, 519-531~ 1971. The oxide la-yer descr:i.be~ :i.n I saic. reports comprises in-ter alla BaO (bari.um o~i~e). T}~e reductol used consists of one or ~cre oi` the elements .~l, C, Mgr, Si. or Zr, whleh el.ements reduce a part of the 13~.0 to Ba. Th~ reductlon of the BaO takes pl.ace :in t.llat t:~.te ~educto:r ~i~fuses from tht-.~ nick.el S11~0:1'~ stril~ in th.
l~yer o~ B~O on the ~upport u:nder ,'he inf`~ence c~f tlle thexltla1. eneI~ry of tlle hecater elemell.', and re~llce~ $1~ere 2S th~ B~O to free ~ rhic3l d.:ifru~3 to the ~1rf~ee oi` the , ' q~
.
3-'l0-'7~ ~ P~Q 77-~lZ
, layer of Ba0 and f`orn]s -cherQ a l~onoat.om:ic surface layer o.t`
¦ low work function.
¦ Cathode support stri.p consistin~ of nicke~. containingr an acti~ator element such as Al, C, Mg, Si or Zr, has bee made by a powder r~etallurgy method in ~rhich ~I mixture o~`
the consti.tuent powders is compressed to form a blocl~, the ~ compressed block is sintered, ~nd the sinccred :Lllgot i5 f rolled. 'l`his method recluiros a. po~rerful press, ~rhich is ¦ expensive, and the centre of tlle ingot is rclatively porou.s.
'~ l0 It i5 necessary to si.Il1;er ]~rge in.gots at :relati~rely higl temperatures :~or a lon~ -timeS Por examplo at 1300C ~or 48 hour~, in order -to recluce the porosity of the cellcre of the ingot. However, such a process is not suitable h-ithout taking troublesome precautions .such as encaps~ .t;:ing the ingQt when the activator element i~s ~agllc~ium, ~rhich i~
volatile and has a bolling ~oint o:f 1'l00C.
~ isadvan.tagre of kn.own ox;de cathoclcs UsiIlg known .~ catllode supr~ort nickel strip is that the quan-tity of` free ba:riun~ available when the cathocle is first operated i.5 20 reduced consi.d.erably by ga3 residue~ in the electrQn tube' in which the cathocle is used,'~hich residues form c0l1lpouuds.
' w:it'h the free bariun~. Thl3 is terrlled tlle poisoi~lr!g of thc cathodeO Such poisoni.n.g gas r~sidue~s are :formed not only as a result of i.nsuffic:ient evaCuati.Qn Or or leaks in the 25 elect.ron tube ( a ~rood vacuum of` 10 7 mm llg still meanC
10~9 mol o~ ~as I)er cm3) 'lut ~llso Qs a re~u'lt of hoati~
i and evvlutio.rl o~ ga.~e~s I':rom componotlts ill tlj.e tube. More-.3 over, the cat'hode~poisoning gases can be ~ormed UpO-l im~act of electrvlls ~ith materials and thc g~s may b~ rcleased 30 from the glass ~ra.ll o~ the electron lub~ A3 already said, ~ ca-thode poisoni.ng occurs i.n particular at the begir~ning of it the opcration of the cal.hode so t~ t the tl~bc i.n which sai~
, cathode ic;ll.sec' i.nitially shows a pOOI Operati.Orl as a j resul.t o~ a poGr cathode em-ission.
J 35 :C-I ;.s the-leroré~ the o~ject'o:~ the in~rention to pro~r:ide an oxicle cat~lode whlc~rl at the~ beë~inn:i.r~ of` the . operatio~l of said caihocle i.s cc~ls:iclerabl~r les_ xe.ls:iti.-~-c to poisonirlg ~ncl which, whe:n used i.n a tubc, ra~ y ~chic~re~
, . ~ .
:1~39827 ¦: 3-10-78 3 PHQ 77-012 I
j ' a good emiss:ion.
i ~ccording to ~he invention, such a cathode of the kind descrlbed in the I`irst ~aragraph is characterized in ! that the reductor i 5 distribut~3d i.nhonlogeneou~ly through the nickel ol` t~le ~upport a.nd Iorms islailds ha.~-.r;g a high reductor concentration ill th.e surface of the support.
The activator element diPfuses from th.e intelior of the cathode support as a reslllt of a conc~ntratlon gra~ient ~ of the aGti~ating elemt3nt being set u~ between the oxide-T 1U bearlng sur*ace o~ the cathode .support arld tlle inte:rlor of ¦ the cathode s~pport as a result of a reaction between bari~
oxide and the activati~lg element at the surface o~` the cathode support. Thus free barium -which was lost by reacticn with gas residues in the electron tube is replaced.
~ 15 Diffusion occurs at acceptable~ rates as a result of` the i high temperature of -the ca-thode support duriIlg oparation of the cathode. The nickel coating surroundj.ng the i particles oP an allo~r of` ni.ckel and an activator element ma~.es it possible to si.nter the compacted strip at high 20- speeds and low temperatures, and makes the sintoring process casier to control.
When magnesium is used as an activator el~3ment, it is introduced into tne powder mixture in the form of nickel-~: control particles of` a ni.ckel-magnesium alloy, for example 25 containing '15~, b~ wei~ht of magnesi.um co-tecl w:;tll ~uch a th.icklless of lliolcc~l t'hat the m~gne,s:Lum ~ontent. of tho l eoated partlo:L~ , 2$ hy we:L.~,rht,. B~r lntroducing the ¦ magnesium ln this manller, the ni.ckel-mag-.resium alloy i3 protected Prom oxi.dation by traces oi` o~rgen which are 30 inevitab~.y present in the si.nterlng ~1,mos~here. I~ is oon~en.:i.enl; to i.ncorporate al.umini,urn when used in tho nlix-tu~
in the ~o-Lm oP a nlccl~,ol--aluminlu.n al3.oy contai.nin~, f`or ex~mple 5~ ~y weight c.P .~luminill~. When the .lc~i~r~to:r el.ement i..s ma~n~sium, -the magnesium contenl o~ e n.cliol.
3~ .strip m~y b~ f'rom 0.03 to 0015,~'. by weightO kT~len tlle nic~e:L
st,r:ip i;lClU~ alumlni.~in-l, t~e alu:nir.iulTI c:ontent o~` the nicl~.el strip ma.y be f':rom 0~01 t~ 0.10G~ we~
3-10-78 4 P~IQ 77-012 Comn1ercially available carbonyl nickel powder consists of more than 99% by weight,of` nickel, together with trace impurities. Small quantities o~ other elements, such as tungsten, may be included in the mixture in order to improve the n1echanica:L properties of the nic1~elst.:rip.
The nickel-coated particles of the alloy of nickel with an acti.va1;or element a.re thorou~hly mixed with carbo- -nyl nicl~el powder and any ot'her ingredients of the mixture~
A strip i.s -then rolled from the mixture, the th:icknr3ss of`
th.e compact,od .strip bei11g ~roverned by the apparatus avallable. Thc compact~d st,rip is the~ sintered, and the sin-tered strip is then rolled so as to reduce the thickness of the stri.p to a desired value~ l`he rolled strip ma)r be a3lnealed ii` desired.
- l5 An embodiment of the invention ~ill now be described with reference to the drawin.g in ~hich Fig~lre 1 is a sectional clevat:ion of an oxide cathode, I~`igur~ 2 is a sectional elevation of a kno~rn cathode support bc3aring a bariulr.-calcium-stron1;ium oxide layer, ~igure 3 is a sectio3lal elevation of a cal,hode support nickel strip made by a method a~cording to thr_ invention bcaring a barium-calcium-strorti1lm o~ide layer, Fi.gure 4 is a plan ~rie~ of a disc of a cathode support. ~ickel strip made 'by a method according to the invention.
'Fi~ure 5 is a. schemal;ic slde cl.evl.tion of an ~p1~ara tllS usc3d to makQ a sintered compncted strlp by ~ m~thoc~
a~cording to the inventlon, and Figure 6 is a plan vie~ of the rollers of t'.he apparatu~ sh.o~n in Fi.~ure 5.
Fi~,r~lre 1 shows an oxide~ cathode consistin~ of a support 1 made of the strip made by the metr.od described w:itll rcfereJ;ce -to Figrures 5 and ~ ~ecllred -to cl cathode s'ha.~ 2. A heatcr ele-rllen~ ~ i.s sit:uate~i below t,he suppor~
1. The s~ ort. 1 bears a laye- ~ ol` (BaCaSr~0. This layer 4 is o1~taiil~d ~ spra.yl~g .1 suspens:ion oi' b~rium-ralciu~
: st.rontium carl~onat~ onto the support 'I and con.verti11g t'he CarbO31ate il~CO (~aCa~r)0 by hea,.tir~
1~398Z7 i 1 3-10--7~ 5 ~HQ 77-012 i l~igure 2 sllows a part of a p.rior art support 1 I bearing an emissive layer 4. This prior art support was produced from a casting of an or a high temperature sintere~
powder metallurgy alloy of nickel ancl an ac-tivator element 5 which is shown as dots homogeneous1y distributed in t~le nickel of` the support and the activator e]ement diffllses into the emissive la~er 4 durin.g ope:ration of the ca~nc,de.
en the emissi~re layer 4 ha.s been F~olsonec1~ the I~aO i.n this cathod~ is not reduced suffi.c.i.ently ral~idly so that th~ emission of the cathode cont;inues at a lower level than was t~le case before poisoning.
Fi~ure 3 shows a part of the support 1 according to the i.n~entlon bearing the emissi.~Te layer 4. Th~ activator elemel1ts 6 Mg and Al are present in the n~ckel of the sup-i l~ port and at the surface of the support in a loca].l.y ~
conceIltrated form so that the supporting consisting of po-~der raetallurgical nicke]. colnprises I.i. 0.05 to o.oc~
by weigllt of Mg an.d from 0.01 to 0.05~ by we~ hi; of A.l~
~ A.s a :esult of thls being localiy concentrated it initially :~ 1 20 di.. ff1lses con.siderably more rapidly i.n-to the emissive layer4 a.nd can rapidly replenish the Ba which has been lost ;-lS
a result of poisoning.
Figure 4 is a plan view of ~.he support 1 according to tlle irl~cntion in which the islands 6 havin~ a high con.c~ntrati.oIl of activa1;or elemen-t are si1.uated. l~
be ob~i.ous that the cat;llode n.iclcel may also be used in other cath.od.e oonstrllctio.ns, and ~cl;i~at()r olcrncnts an~l 1' a.lka].i.. ne earth motal oxidos other than those de~cribsd may b~ usedO
Now a method for mallllfactuLin~ n1etal].l.lr~ical nic1~l i for su.ch a cathode wi1l be describ6d.
A magn~sl-ml-nickel a.lloy corl1;a:inin~ 15,~, by wei.gh1; o:t`
j ma~lles:L~ Ti in the .forl~ of lu.nps was crushed9 ~round and 1 s-ie~Je~ I;he matsri.al p~s~in~ a 350 mesh (mcshe~s pcr illCI' )3~ s:ievc beir~l~ coll.ected. ~rhi.5 minu~ ~50 mesn IriatcriLtl ~.~as coated w:ith a t.~ic.n~s.s of ni.ckel suc1~. tha~ t~e Inclg-rl~s1.u~
content Or t~;le coace~ particles 1~a; 2~o ~y ~Tei~ht. Thc part-~c.~os w~re coat;ed ~i.th nic~;~l in an autoc1ave by tlle .
: .
,, :, .. ~ .. .. . .. . . .. .. . ........ , .. ~ .. ... .
1~39827 3- iO-1 ~)7~ 6 PHQ 77-012 reductiLon of an aqueous ar~nonlaea . solution eol~taining n.~ekel. sll~phate and amrllonium slllpha.t~ heated to 175C, the au ,;oealve eontai.ning an over-pressure of 350 lbs/in2 o:f h-~7drogGn.
1~ master Dlixt;ure consis ting oI` equal weigh.ts of tungsten powder and carbonyl. nick~al powder having average particle ~sizes of 3/um was prepared. All alunl-lniun~-nlcke].
(52/~l~3 by weight) ~:~owrlGr was sleved through a I-()O mesh sieve and t.he rni.l~us IIOC mesh :fraetion w~s use-l.
A m~ tu~e \~as pri3parod consistilng of 80 g o:f thc3 ll:icke~ l-coa ted magne~sillm-lli.cke:l. alloy parti.cles 1 . (:'j g C!:~ th~a n1intl.s 1loo mesh alumillium-nic3~el. alloy powder 80 ~ o:L` th~ tungsten arid ea-.rborl~_ niekel master mix-l;ure 1 ælTO g o:E` earbonyl nickel po~del .
This mi:~ture eor~a:Lns 0.08 ~ llg, 0,04 % by woig~nt Al arl.d 2 G~ y we igh t W .
Re:ferring -to l?igures 5 and 6 o:L` the dr~3wings, po~rder mixture 1 0 was fed i~to a h.opper 11 I`rc,m l~Thi.Ch the powder pQ,ssed i.lltO a o.6 rr!rn wide gap 12 bet~eerl t~-To 15G mn~
~liameter rollers 13, 14 xu.nning in th(3 hori~,ontal plan~.
The eoJrpacted stri.p 15 l~as.sed over suppor-t rollers 16, 1 ~
and læ b~3fc-re enterLn~ a mu:Erle tube 19 o:f a muI:E:le furn~ce ZO l.n whieh the strip 15 l~as si.nte:led. .Puret dry h5~clrogre wa~ passed throuT~r~h th.e muf:fle ttub~3 1~3 ~llcl t.h~ st;r.ip passed l;hl ou~r,h t;he lu:r]lace at ~ueh a r at.c~ t llat: a peak tenll~t3ral:uro o:~ 1050~C wa~s appli.ed :Eor 3 m:L~ .tos, Thc s-lntc3r~ed s~tr.:ip 21 em~r~in~ rrorn ~t~ e n~ f.fle tUb? 1~3 w~
J;~ 011~ 1 Go(,) Itlm d:~arl~et~ SpO~ I 2'> ~ ~rll~3 sillte c`e~' s~ i ~as 0. 7 ~ t~li.C~:' arld ~ra~; SUbs(?r~L~:(37:ltLs~ I`OLleCi to ~i~e a fll,xl thlcl~ne~ of 100/u~n~ Thi.~; 100/un; strip I a~ nsi3c~ lo rnali.f3 t~ 3 oxi.~r2 Cat'rlOQ'3 suppox~t~
., . ~ . ~
Claims (9)
- PHQ. 77-012.
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PRO-PERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. An oxide cathode comprising a cathode support which consists substantially of powder metallurgical nickel, which nickel comprises an activator element capa-ble of reducing the emissive coating, which coating is provided on the support and which consists of a compound of at least one alkaline earth metal and oxygen, and a heater element disposed on the side of the cathode support remote from the emissive coating, characterized in that an activator element is present in the powder metallurgical nickel in the form of nickel-coated particles of an alloy of nickel with the activator element. - 2. An oxide cathode as claimed in Claim l, charac-terized in that the activator element is at least one of the elements Mg, Li, Ca and Al.
- 3. An oxide cathode as claimed in Claim 2, charac-terized in that the support consisting of powder metallur-gical nickel comprises from 0.05 to 0.09% by weight of Mg and from 0.01 to 0.05% by weight of Al.
- 4. A method of making a nickel strip, for a cathode as claimed in Claim 1, characterized in that the method comprises the steps of preparing a mixture compris-ing nickel-coated particles of an alloy of nickel with an activator element, and carbonyl nickel powder, rolling the mixture to form a compacted strip, sintering the compacted strip at a temperature of from 900 to 1100°C in a reducing atmosphere, and rolling the sintered strip so as to form a cathode support nickel strip of the desired thickness, wherein the activator element is capable of reducing barium oxide to barium at the operating temperature of an oxide cathode.
- 5. A method as claimed in Claim 4, characterized in that the mixture comprises nickel-coated particles of a magnesium-nickel alloy, and carbonyl nickel powder.
- 6. A method as claimed in Claim 4, characterized in that the mixture comprises nickel-coated particles of a magnesium-nickel alloy, an aluminium-nickel alloy and carbonyl nickel powder.
- 7. A method as claimed in Claim 5 or 6, charac-PHQ. 77-012.
terized in that the mixture contains from 0.03 to 0.15 %
by weight of magnesium. - 8. A method as claimed in Claim 6, characterized in that the mixture contains from 0.01 to 0.10 % by weight of aluminium.
- 9. A method as claimed in Claim 4, 5 or 6, char-acterized in that the reducing atmosphere consists of hydrogen.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB50723-77 | 1977-12-06 | ||
| GB5072377 | 1977-12-06 | ||
| GB44332/78 | 1978-11-14 | ||
| GB7844332A GB2012103B (en) | 1977-12-06 | 1978-11-14 | Oxide cathode |
| GB44331/78 | 1978-11-14 | ||
| GB7844331A GB2010911B (en) | 1977-12-06 | 1978-11-14 | Method of making cathode support nickle strip |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139827A true CA1139827A (en) | 1983-01-18 |
Family
ID=27260167
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000317186A Expired CA1139827A (en) | 1977-12-06 | 1978-11-30 | Oxide cathode and method of manufacturing powder metallurgical nickel for such a cathode |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS54100249A (en) |
| CA (1) | CA1139827A (en) |
| DE (1) | DE2852356C2 (en) |
| FR (1) | FR2411483A1 (en) |
| IT (1) | IT1101677B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0268259U (en) * | 1988-07-05 | 1990-05-23 | ||
| NL9000405A (en) * | 1990-02-20 | 1991-09-16 | Stichting Energie | POWDER-BASED STARTING MATERIAL FOR A NICKEL-BASED ALLOY FOR MANUFACTURING A POROUS ANODE FROM A FUEL CELL, METHOD FOR PREPARING SUCH MATERIAL, PROCESS FOR PRODUCING AN ANODY FOR A PURPOSE ANIMAL PROPERTIES, AND PROPERTIES. |
| JPH0850849A (en) | 1994-05-31 | 1996-02-20 | Nec Kansai Ltd | Cathode member and electronic tube using it |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE523271A (en) * | 1952-10-06 | |||
| DE1027801B (en) * | 1955-08-25 | 1958-04-10 | Lorenz C Ag | Carrier for oxide cathodes |
| NL101694C (en) * | 1959-03-06 | |||
| GB1076229A (en) * | 1963-10-08 | 1967-07-19 | Sylvania Electric Prod | Cathodes |
| NL6804720A (en) * | 1968-04-04 | 1969-10-07 | ||
| US4081713A (en) * | 1976-01-28 | 1978-03-28 | Hitachi, Ltd. | Directly heated oxide cathode |
-
1978
- 1978-11-30 CA CA000317186A patent/CA1139827A/en not_active Expired
- 1978-12-01 IT IT3047878A patent/IT1101677B/en active
- 1978-12-02 JP JP14959278A patent/JPS54100249A/en active Granted
- 1978-12-04 DE DE19782852356 patent/DE2852356C2/en not_active Expired
- 1978-12-06 FR FR7834363A patent/FR2411483A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2852356C2 (en) | 1985-07-04 |
| JPS54100249A (en) | 1979-08-07 |
| FR2411483B1 (en) | 1984-09-21 |
| DE2852356A1 (en) | 1979-06-07 |
| IT1101677B (en) | 1985-10-07 |
| FR2411483A1 (en) | 1979-07-06 |
| JPS613061B2 (en) | 1986-01-29 |
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