Bo on ni ide nanoshee s as an e ec i e s a egy agains he slow c ack
g ow h and hyd o he mal ageing in zi conia composi es
C. Mu˜
noz-Fe ei o
a,b,c
, A. Mo ales-Rod íguez
a
, H. Re e on
b
, E. Guisado-A enas
a
, S. Co ino
b
,
P. Mo eno
d
, J. P ada-Rod igo
d
, J. Che alie
b
, ´
A. Galla do-L´
opez
a
, R. Poya o
c,*
a
Dp o. de Física de la Ma e ia Condensada, ICMS, CSIC-Uni e sidad de Se illa, Apdo. 1065, 41080 Se illa, Spain
b
CNRS, INSA Lyon, Uni e si ´
e Claude Be na d Lyon 1, MATEIS, UMR5510, 69621 Villeu banne, F ance
c
Ins i u o de Ciencia de Ma e iales de Se illa, ICMS, CSIC-Uni e sidad de Se illa, A da. Am´
e ico Vespucio 49, 41092 Se illa, Spain
d
G upo de Aplicaciones del L´
ase y Fo ´
onica (ALF-USAL), Unidad de Excelencia en Luz y Ma e ia Es uc u adas (LUMES), Uni e sidad de Salamanca, Pl. de la Me ced,
s/n, 37008 Salamanca, Spain
ARTICLE INFO
Keywo ds:
Bo on ni ide nanoshee s
Y ia s abilized zi conia
Low empe a u e deg ada ion
ABSTRACT
This pape explo es he e ec i eness o bo on ni ide nanoshee s in p e en ing he p ema u e ailu e o y ia-
s abilized e agonal zi conia ce amics, pa icula ly in humid en i onmen s. A simple, low-cos and scalable
echnique -shea ex olia ion in a ki chen blende - was used o p epa e BNNS, and pu e zi conia and composi es
wi h 1, 2.5 and 5 ol. % BNNS we e spa k plasma sin e ed. Accele a ed hyd o he mal ageing expe imen s in
au ocla e e ealed a ema kable imp o emen o low empe a u e deg ada ion esis ance in all he composi es.
F ac u e oughness and slow c ack g ow h o he composi es wi h 1 and 2.5 ol. % BNNS we e e alua ed by
bending es s pe o med in no ched specimens. Al hough he composi es p esen ed ac u e oughness alues
simila o hose o he e e ence zi conia, an inc ease o ~18 % on c ack- ip oughness was achie ed. Simila R-
cu es e alua ed in ai and in oil-imp egna ed 2.5 ol. % BNNS composi es e ealed a limi a ion o s ess-assis ed
co osion by wa e in zi conia, hanks o he BNNS inco po a ion.
1. In oduc ion
Y ia-s abilized e agonal zi conia polyc ys als (YTZP) a e ech-
nical ce amics widely used in s uc u al and biomedical applica ions due
o hei supe io ac u e esis ance esul ing om a phase ans-
o ma ion oughening mechanism. In pa icula , he bes known TZP
bioce amic con ains 3 mol. % o y ia (Y
2
O
3
; 3YTZP) and leads o
s eng h alues abo e 1000 MPa, excellen biocompa ibili y, high
ha dness and wea esis ance. Howe e , in YTZP ce amics, mechanical
p ope ies can de e io a e in humid o aqueous en i onmen s. The
in e ac ion o wa e molecules wi h s ained Z -O-Z bonds a any p e-
exis ing c acks ini ia es i s p opaga ion unde ensile loading a a
s ess in ensi y (K
I
) alue below he c i ical s ess in ensi y ac o o
ac u e oughness (K
IC
). This p ocess de e io a ing he bonding a he
c ack ip, e e ed o as “subc i ical c ack g ow h” o “slow c ack
g ow h” (SCG), esul s in a delayed ailu e ha signi ican ly limi s he
long- e m pe o mance o zi conia componen s [1,2]. On he o he
hand, he wa e molecules can also p omo e he p ocess o spon aneous
nuclea ion and g ow h o monoclinic g ains, om he su ace o he
bulk, esul ing in g ain pull-ou , mic oc acks and su ace oughening.
This spon aneous ans o ma ion om he e agonal ( ) o he mono-
clinic (m) phase, which occu s a low empe a u e, in he absence o
s ess bu in he p esence o wa e has been e e ed o as
low- empe a u e hyd o he mal deg ada ion (LTD) o ageing [3].
Signi ican esea ch e o s a e cu en ly unde way o de elop
oughe and s onge zi conia-based composi es o ensu e he long- e m
eliabili y o hese oxide ce amics. Zi conia- oughened alumina com-
posi es, as well as ce ia- and magnesia-doped zi conia, a e he mos
p omising choices o o e coming ageing/SCG issues discussed abo e
and ela ed o wa e -biased ac u ing p ocesses in YTZP [4]. The
mic os uc u al e inemen o highly ans o mable Ce-TZP-based com-
posi es h ough he addi ion o di e en oxides esul ed in an
imp o emen o hei esis ance o SCG [5]. The addi ion o La
2
O
3
was
bene icial in imp o ing he ageing s abili y o 2YTZP (i.e. 2 mol. %
Y
2
O
3
) ma ix alumina oughened zi conia (ATZ) composi es, wi h a
supe io balance be ween ageing and c ack g ow h esis ance compa ed
o con en ional 3YTZP and ATZ composi es wi hou La
2
O
3
doping [2].
Since me al ansi ion ca bides and ni ides a e almos insensi i e o
* Co esponding au ho .
E-mail add ess: [email p o ec ed] (R. Poya o).
Con en s lis s a ailable a ScienceDi ec
Open Ce amics
jou nal homepage: www.sciencedi ec .com/jou nal/open-ce amics
h ps://doi.o g/10.1016/j.oce am.2025.100816
Recei ed 23 Ap il 2025; Recei ed in e ised o m 10 June 2025; Accep ed 10 June 2025
Open Ce amics 23 (2025) 100816
A ailable online 10 June 2025
2666-5395/© 2025 The Au ho s. Published by Else ie L d on behal o Eu opean Ce amic Socie y. This is an open access a icle unde he CC BY-NC-ND license
(
h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/ ).
SCG, Zhang e al. [1] ha e shown ha he ein o cemen o zi conia wi h
co alen ce amics also esul ed in composi es wi h p omising esis ance
o subc i ical c ack p opaga ion assis ed by wa e molecules.
In he las decade, p e en ing he wa e -induced ac u e o zi conia
composi es by inco po a ing low-dimensional ca bon nanos uc u es
has ecei ed inc easing a en ion [6–11]. The inco po a ion o a low
olume ac ion o ca bon nano ubes (CNT) ad an ageously balances
he ageing and c ack p opaga ion esis ance o 3YTZP composi es hanks
o he small g ain size o he sin e ed zi conia ma ix, which impedes he
-m phase ans o ma ion ha cha ac e izes he ageing, and he inco -
po a ion o new oughening mechanisms ela ed o CNT [6]. The
educed mic o–c acking and he subs an ially inc eased esis ance o
ageing in 3YTZP composi es wi h 0.5–2.5 ol. % CNT ha e been ela ed
o he modi ica ion o he ce amic g ain bounda ies due o he nano ubes
inco po a ion and o he abili y o CNT o abso b he elas ic ene gy
ela ed o he ma ensi ic -m ans o ma ion, by means o nano ube
bending and in e –bundle sliding [8]. G aphene-based nanoma e ials
(GBN) ha e also been success ully used o p e en hyd o he mal ageing
o zi conia-based ma e ials [7,9]. Al hough some au ho s [7] ha e
ela ed he inhibi ion o he -m phase ans o ma ion in zi conia com-
posi es con aining g aphene pla ele s (GPL) o he g ain e inemen
p omo ed by he in oduc ion o GPL, mo e ecen s udies [9] ha e also
co ela ed he enhanced esis ance o hyd o he mal ageing in
zi conia-GBN composi es o he g aphene’s impe meabili y o mois u e
[12].
In ecen yea s, se e al s udies ha e epo ed he enhanced me-
chanical p ope ies and ailo ed he mal and elec ical p ope ies o
ce amic o polyme composi es when inco po a ing ino ganic nano-
s uc u ed ille s, including hyb id o modi ied ille s as bo on ni ide
(BN) o alumina [10,11,13–15]. These composi es a e p oposed o hei
use in s uc u al and unc ional applica ions. Speci ically, a ew wo ks
[10,11] ha e s udied he inco po a ion o 2D bo on ni ide (BN) o
zi conia o p e en he deg ada ion o mechanical p ope ies in humid
en i onmen s. This 2D nanoma e ial has p ope ies as excep ional as
hose o g aphene –high mechanical s eng h, excellen he mal con-
duc i i y and impe meabili y o mois u e and o he gases [16]– and also
o e comes some o g aphene’s disad an ages, such as he isk o cy o-
oxici y, which could hampe he use o ce amic composi es wi h g a-
phene as bioma e ials [10]. P e ious s udies ha e e ealed he high
biocompa ibili y o BN [17,18] and 3YTZP composi es wi h bo on
ni ide nanopla ele s (BNNP) ha e been p oposed o applica ion as
den al ma e ials [10]. In his sense, he s udy o he low- empe a u e
deg ada ion (LTD) o hese composi es akes an eno mous ele ance.
The only wo k a ailable up o da e on LTD o ce amic composi es wi h
bo on ni ide 2D nanoma e ials showed no iceable enhancemen o he
esis ance o LTD in ATZ nanocomposi es. The inc eased ageing esis-
ance was a ibu ed o he homogeneously dispe sed, andomly o i-
en ed BN nanopla ele s, which p e en ed mois u e pene a ion a he
su ace o he polyc ys alline ce amic ma e ial [10]. Recen ly,
Mu˜
noz-Fe ei o e al. [11] showed ha he inco po a ion o 2.5 ol. %
hyd oxyla ed BN nanoshee s (BNNS) in o 3YTZP composi es success-
ully inhibi ed slow c ack g ow h, inc easing he c ack g ow h esis ance
o he composi e by ~30 %. The nanoshee s we e dis ibu ed h oughou
he 3YTZP ma ix wi h he ab plane pe pendicula o he c ack on , and
he au ho s ela ed he enhancemen in slow c ack g ow h esis ance o
he blocking by he BNNS o any wa e molecule a emp ing o each
deep in he composi e. Howe e , despi e hese p omising esul s, o he
bes o ou knowledge, o da e he e a e no publica ions on he hyd o-
he mal deg ada ion o BNNS/YTZP composi es.
The common syn hesis app oaches o ob ain BNNS include bo om-
up echniques such as chemical apo deposi ion o solid-phase eac-
ion and op-down ou ines such as liquid phase ex olia ion o hexagonal
h-BN powde by ul asonica ion o ball milling [11,13,19,20]. Howe e ,
he sea ch o en i onmen ally iendly p ocedu es wi h high p oduc-
ion a e and easiness o scale up ha use common sol en s and mini-
mize pollu an chemical agen s is s ill ongoing. I has been demons a ed
ha de ec - ee ew-laye g aphene (FLG) can be ob ained om g aphi e
lakes using a ki chen blende [21,22], e en wi h household de e gen as
su ac an [23]. The domina ing la e al o ces in he mixe lead o
simple sel -ex olia ion o he pa icles. Fu he mo e, Va la e al. [23]
cha ac e ized he scaling o bo h FLG concen a ion and p oduc ion a e
wi h he mixing pa ame e s - mixing ime, ini ial g aphi e concen a-
ion, o o speed and liquid olume- and ound ha he FLG p oduc ion
a e inc eased wi h he blended olume, meaning ha i can be scaled up
o indus y le els, con a y o ul asonic agi a ion me hods in which he
p oduc ion a e s uck a a ce ain olume. Coleman e al. [24] had
al eady op imized he liquid ex olia ion o a ious laye ed ma e ials,
including h-BN, when Pa on e al. [22] managed o ex olia e la ge
quan i ies o de ec - ee ew-laye g aphene wi h a ki chen blende as a
p oo o concep , sugges ing ha his me hod could be applied o ex o-
lia e BN, MoS
2
and a ange o o he laye ed c ys als. In his s udy, he
scaling beha io o he g aphene p oduc ion a e was ully cha ac e -
ized, e ealing ha ex olia ion could be achie ed in liquid olumes om
hund eds o millili e s up o hund eds o li e s and beyond.
The objec i e o his s udy is o e alua e he e ec i eness o BNNS in
p e en ing he p ema u e ailu e o zi conia ce amics in humid en i-
onmen s. To ha end, BNNS we e ex olia ed wi h a simple, low-cos
and scalable echnique and inco po a ed in o a 3YTZP ma ix. The hy-
d o he mal ageing esponse o zi conia composi es con aining 1, 2.5,
and 5 ol. % BNNS was in es iga ed by pe o ming accele a ed au o-
cla e ageing es s. The ac u e oughness (K
IC
) and slow c ack g ow h
(SCG) beha io o he composi es wi h 1 and 2.5 ol % BNNS we e
e alua ed in bending es s and compa ed wi h he e e ence zi conia
ce amic o cla i y he e ec o BNNS inco po a ion on he ac u e
beha io and slow c ack g ow h sensi i i y o wa e en i onmen .
2. Expe imen al p ocedu e
2.1. Ma e ials p ocessing
2.1.1. Syn hesis and cha ac e iza ion o he BN nanoshee s
BNNS we e p oduced by he shea ex olia ion o a comme cial hex-
agonal h-BN powde (<44 µm pa icle size, 99.5 % pu i y;
Re . 11,078.18; Al a Aesa , Kandel, Ge many) using a ki chen blende
(KB). This me hod was selec ed due o i s high p oduc ion a e, ela i ely
low-cos , and easiness o scale up [21–23]. The liquid shea ex olia ion
o BNNS was pe o med using a Sil e c es ki chen blende (Lidl, Ge -
many) wi h a maximum powe o 600 W and a maximum capaci y o
1.75 L. The o a ional speed o he blades could no be con olled, as
only i e ixed eloci ies (named om 1 o 5) we e a ailable. The
op imal speed was selec ed by compa ing he esul ing BNNS a e hei
ex olia ion a low (1), medium (3) and high (5) eloci ies. Fo each
p ocedu e, 5 g o h-BN powde we e added o he blende jug illed wi h
500 ml o isop opyl alcohol (iP OH), and he blende ope a ed o 30
min. The suspension concen a ion and ex olia ion ime we e chosen
based on he s udies om Va la e al. [23] and Coleman e al. [24]. The
mixe was u ned o o a ew minu es e e y 3 min o ex olia ion un il
he o o and suspension had cooled down. The suspension was hen
collec ed, allowed o se le o one day and cen i uged a a ela i e
cen i ugal o ce RCF o 360 g (wi h g=Ea h’s g a i a ional ield) o 45
min in ei he a Ro o ix 32 A o an Alleg a X-12R equipmen (Beckman
Coul e , USA; a Cen o de In es igaci´
on, Tecnología e Inno aci´
on de la
Uni e sidad de Se illa, CITIUS). Finally, he uppe h ee qua e s o he
supe na an we e collec ed o a oid collec ing possible agglome a es
loca ed owa ds he bo om o he ube. This suspension o BNNS in
i
P OH was used di ec ly as he aw ma e ial o p epa e he composi e
zi conia powde s.
The pa icle size dis ibu ions a e he ex olia ion p ocesses we e
quan i ied by lase g anulome y (LG, Mas e size 2000, Mal e n Pan-
aly ical, UK; a CITIUS) and dynamic ligh sca e ing (DLS, Ze asize
Nano Z, Mal e n Panaly ical, UK; a CITIUS). The BNNS suspension
ob ained a e cen i uga ion was added d opwise o he Hyd o 2000S
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
2
accesso y (Mal e n Panaly ical, UK) illed wi h
i
P OH. The F aunho e
model, which assumes a sphe ical shape o pa icles in suspension, was
used o he LG calcula ions. The e o e, when analyzing 2D nano-
ma e ials, such as he BNNS in he p esen s udy, he pa icle size
de e mined by his echnique does no ep esen he eal pa icle size
dis ibu ion and should be conside ed only o quali a i e compa ison
be ween simila ma e ials. The LG pa icle size de ec ion anges om
0.02 o 2000
μ
m while DLS size measu emen s a e limi ed om 0.6 nm
o 6 µm. The BNNS suspension was dilu ed o a concen a ion o 1:10 in
i
P OH o p e en decan a ion du ing measu emen acquisi ion. Bo h
esul ing pa icle size dis ibu ions we e a e aged om a leas h ee
measu emen s.
In his wo k, he abso bance spec um in he en i e isible ange o
BNNS syn hesized in he ki chen blende was eco ded wi h a Ca y 5000
spec opho ome e (Agilen , USA; a Ins i u o de Ciencia de Ma e iales de
Se illa, ICMS). The BN nanoshee suspension was dilu ed en old and
placed in a 1 cm side glass cu e e o analysis. UV–Vis spec oscopy
esul s we e hen used o de e mine he concen a ion o he BNNS in he
suspensions. The abso bance a 300 nm was measu ed (Pha o 300
spec opho ome e , Me ck, Ge many; a CITIUS) and he ex inc ion co-
e icien was aken as
ε
300 =2367 ml mg
-1
m
-1
, acco ding o Coleman
e al. [24].
The mo phology and s uc u al in eg i y o he ex olia ed BNNS we e
cha ac e ized by ansmission elec on mic oscopy (TEM), high-
esolu ion ansmission elec on mic oscopy (HR-TEM) and Raman
spec oscopy. To ha end, a ew d ople s o he sonica ed BNNS sus-
pension in
i
P OH we e deposi ed on a Cu ansmission g id wi h C
coa ing ( o TEM and HR-TEM inspec ion) and on a glass slide ( o
Raman spec oscopy). The Raman spec a we e acqui ed using a
dispe si e mic oscope (Ho iba Jobin Y on LabRam HR800, Kyo o,
Japan; a ICMS), equipped wi h a He-Ne g een lase (532.14 nm) a 20
mW. The mic oscope used a 100x objec i e and a con ocal pinhole o
100
μ
m. The Raman spec ome e was calib a ed using a silicon wa e .
TEM and HR-TEM images we e acqui ed wi h a FEI Talos S200 ans-
mission elec on mic oscope (FEI, O egon, USA; a CITIUS).
2.1.2. P ocessing and sin e ing o 3YTZP-BNNS composi es
A comme cially a ailable 3YTZP powde wi h 40 nm pa icle size
was used as ma ix (TZ-3YB-E, Tosoh Co po a ions, Tokyo, Japan). The
as- ecei ed 3YTZP powde was annealed a 850 ◦C o 30 min o emo e
o ganic addi i es. Then, his powde was added di ec ly o he BNNS
suspension ob ained om he shea ex olia ion p ocess in he ki chen
blende , and he wo phases we e mixed by s ong magne ic s i ing.
Composi e suspensions con aining 1, 2.5, and 5 ol. % BNNS we e
p epa ed. A e d ying on a ho pla e, he esul ing powde s we e ho-
mogenized in an aga e mo a be o e sin e ing.
The composi e powde s we e spa k plasma sin e ed a 1250 ◦C o 5
min unde acuum, using hea ing and cooling amps o 100 and 50 ◦C/
min, in a SPS model 515 S (D . Sin e , Inc., Kanagawa, Japan; a CITIUS)
o in an HPD 25 model (FCT Sys eme GmH, Ge many; a Labo a oi e
Ma ´
e iaux Ing´
enie ie e Sciences, MATEIS) o p epa e disk-shaped samples
o 15-mm o 40-mm diame e , espec i ely. A 75 MPa p essu e was
applied om 700 ◦C when hea ing and i was main ained du ing he
sin e ing p ocess un il i s emo al a he same empe a u e while cooling
down. The empe a u e was moni o ed using an op ical py ome e
ocused on a hole d illed in he cen e o he g aphi e die. A g aphi e oil
(0.35 mm hick) was placed be ween he powde s and he die/punches
and along he inne wall o he mold o ensu e elec ical, mechanical,
and he mal con ac and o easy sample emo al. The esul ing sin e ed
composi e disks (3 – 4 mm hick) we e manually g ound o emo e he
g aphi e pape om he SPS molding sys em.
2.2. Mic os uc u al cha ac e iza ion
The bulk densi y o he sin e ed samples was measu ed by he
A chimedes’ me hod, using dis illed wa e as imp egna ion and
imme sion liquid. The imme sion p o ocol desc ibed in ASTM C373–18
was ollowed. The specimens we e d ied in an o en a ~ 100 ◦C o a
leas 2 h be o e being weighed in ai (m
a
) using a p ecision balance
(Me le AM100). The samples we e hen degassed by placing hem
unde acuum in a desicca o o 2 h 30 min. The imme sion p ocess was
comple ed by b inging he desicca o o a mosphe ic p essu e and
lea ing he samples imme sed o 24 h o ensu e comple e imp egna ion
o he open po osi y. A e his p ocedu e, he imp egna ed samples
we e weighed in ai (m
ia
) and in dis illed wa e (m
iw
) using a p ecision
balance (Me le AM100) and he expe imen al densi y (
ρ
exp
) calcula ed
as ollows:
ρ
exp =ma
mia −miw
ρ
w
whe e
ρ
w
is he wa e densi y a he es empe a u e. Fo each ma e ial,
he expe imen al densi ies we e a e aged om a leas h ee di e en
measu emen s. The ule o mix u es was used o calcula e he heo e ical
densi ies o he composi es, conside ing he densi y alues o 6.05 g cm
-3
o 3YTZP and 2.1 g cm
-3
o h-BN, p o ided by he ma e ial supplie s.
Semi-quan i a i e analysis o he c ys allog aphic phases p esen in
he sin e ed composi es was pe o med by X- ay di ac ion (XRD, model
D8 Ad ance A25, B uke Co. Massachuse s, USA; a CITIUS) in B agg-
B en ano con igu a ion, equipped wi h a Lynxeye PSD de ec o
(B uke , Ge many), wi h coppe K
α
adia ion.
Low-magni ica ion scanning elec on mic oscopy (SEM, FEI-Teneo,
FEI, O egon USA; a CITIUS) using backsca e ed elec ons (BSE) o
imaging was used o cha ac e ize he BNNS dis ibu ion in he zi conia
ma ix. To ha end, c oss sec ion (c.s.) su aces, i.e. su aces pa allel o
he SPS p essing axis, we e polished wi h diamond pas e down o 1
μ
m.
SEM was used o examine he ac u e su aces o he composi es as well
as o cha ac e ize he BNNS mo phology and ce amic g ain size, quan-
i ying he mean equi alen plane diame e and i s co esponding
s anda d de ia ion. ImageJ and O iginLab so wa es we e used o
analyze he g ain size dis ibu ions by measu ing mo e han 300 g ains
o each ma e ial and i ing o a logno mal dis ibu ion.
2.3. LTD expe imen s – accele a ed ageing es s
Au ocla e ageing es s we e pe o med o e alua e he sensi i i y o
he composi es o hyd o he mal deg ada ion. Samples wi h in-plane
sec ions polished down o 1-mic on we e placed in an au ocla e
(SANOcla , model TKL-MCS-5, Ge many) wi h dis illed wa e a 134 ◦C
and 0.2 MPa o con olled pe iods o ime acco ding o ISO s anda d
13356. In-plane sec ions o he samples we e selec ed o he analysis
since p e ious s udies e ealed ha hyd o he mal ageing esis ance on
hese composi es was dec eased when analyzed on he c oss-sec ions
[25]. The e olu ion o he ans o med monoclinic phase was quan i-
a i ely ollowed on he polished su ace by XRD a e each s eam
exposu e pe iod. The XRD da a we e acqui ed o e a sho 2θ ange
( om 27◦ o 33◦), wi h a s ep size o 0.015◦and a ime pe s ep o 0.5 s.
The monoclinic zi conia olume ac ion (V
m
) was es ima ed as
desc ibed by To aya [26]:
Vm=1.311Xm
1+0.311Xm
The monoclinic/ e agonal zi conia con en a io, Xm, was de e -
mined by measu ing he a ea unde he monoclinic and e agonal
p incipal di ac ion peaks egis e ed in he XRD pa e ns, using he
Ga ie and Nicholson equa ion [27].
The ans o med monoclinic ac ion as a unc ion o he ageing ime
was analyzed assuming nuclea ion and g ow h p ocesses in he ame-
wo k o he Kolgomo o -Jhonson-Mehl-A ami (KJMA) o malism:
X=1−exp{ − [b⋅( − 0)]n},
whe e X is he monoclinic con en escaled o he sa u a ion alue, X=
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
3
Vm
Vmax, b is an A henius he mally ac i a ion e m, 0 is he induc ion ime,
and n is he A ami exponen ela ed o he nuclea ion and g ow h
condi ions o he monoclinic egions [28]. The onse o ans o ma ion 0
was accu a ely es ima ed a e [29] as
0= slope −
α
( in − slope),
whe e in is he ime a which he ans o ma ion a e is maximum
(ob ained using dX
d cu es), slope = in −X( in )
dX
d ( in )and
α
= − 0.014,co e-
sponding o n=1 (which is consis en wi h he bes - i esul s ha we e
ob ained in he KJMA-plo s o ou s udy).
The ageing pa ame e s n and b we e es ima ed by linea i ing o he
KJMA-plo s, i.e. ln(− ln(1−X)) e sus ln( − 0), in he in e al co e-
sponding o X =0.1 and X =0.9.
2.4. Mechanical cha ac e iza ion
F ac u e oughness (K
IC
) and c ack g ow h esis ance cu es (R-
cu es) we e e alua ed using he single edge V-no ched beam (SEVNB)
echnique in ba s machined om 40-mm disk-shaped sin e ed compos-
i es. The s aigh - h ough- hickness V no ch was made in he cen e o 3
mm x 3.8 mm x 25 mm (b x w x L) ec angula specimens. The 3 mm
wide side ecei ed he s a ing no ch (diamond saw) ha was inished by
ul asho pulsed lase abla ion (UPLA). The no ch-leng h- o-wid h
a io, which is he o al no ch leng h, was 0.3 o he K
IC
measu e-
men s and 0.5 o he R-cu e analyses. Expe imen al de ails o he
no ch lase abla ion we e desc ibed elsewhe e [11]. The no ch was
pe o med pa allel o he SPS p essing axis. In a p e ious s udy [30] we
assessed R-cu e analysis on aniso opic 3YTZP composi es wi h
educed g aphene oxide ( GO) as ille in which he no ch was pe -
o med pe pendicula o pa allel o he SPS p essing axis, epo ing ha
he highes c ack esis ance was achie ed when he plana c ack on
was pe pendicula ly o ien ed o he GO main ab plane. Thus, in he
p esen s udy his no ch con igu a ion was selec ed o pe o m he
bending es s.
K
IC
was measu ed in a ou -poin bending con igu a ion, wi h sup-
po ou e and inne spans o 21 mm and 10 mm, using a uni e sal
es ing sys em INSTRON 8500 machine (No wood, USA; a MATEIS).
Specimens we e loaded in ai a a cons an displacemen -con olled a e
o 0.5 mm/min and o ce-de lec ion cu es we e eco ded. The ac u e
oughness alues we e calcula ed as he s ess in ensi y ac o (K
I
) o
he maximum applied load, F
max
, as desc ibed in [11]. Resis ance o
s able c ack g ow h (R-cu e) was s udied bo h in ai and oli e oil in
o de o e alua e he e ec o slow c ack g ow h in he composi es.
R-cu e was es ima ed using he compliance me hod on a h ee-poin
bending de ice wi h a suppo span o 20 mm ollowing he p ocedu e
ecen ly alida ed o simila composi es [11,30]. Tes s we e conduc ed
a a cons an displacemen a e o 10
μ
m/min o achie e slow c ack
p opaga ion du ing loading. All es s we e unloaded a 100
μ
m/min
p io o comple e ailu e o ensu e no u he c ack p opaga ion. Fo
each ma e ial, he K
IC
alue and K
I0
and ΔK
I, h
pa ame e s we e a e -
aged om a leas h ee measu emen s, and he dispe sion o he esul s
was e alua ed as he demi-dispe sion o he indi idual alues. Oli e oil
was chosen among o he oils because o i s lowe wa e con en . The
imp egna ion p o ocol was es ablished ollowing he in e na ional
s anda d o densi y measu emen s h ough liquid imme sion (ASTM
C373–18 [31]) and he me hodology p esen ed by Che alie e al. [32].
The specimen was placed in a desicca o unde a acuum o 10
–2
mba
o 2.5 h, a e p ope ly d ying i in s o e a 105 ◦C o mo e han 2 h, in
o de o emo e mois u e and isola e he c ack pa h om he ai hu-
midi y. The imme sion liquid was also placed inside he desicca o o
minimize ai in he oil. Finally, he specimen was imme sed in oli e oil
main aining he acuum o ano he 2 h. To gua an ee no con ac wi h
he en i onmen al humidi y, no mal p essu e was eco e ed jus be o e
he es ing.
The ac u e su aces and c ack pa hs be o e ailu e we e analyzed by
SEM (Zeiss SUPRA VP55, Swi ze land; a MATEIS) o in es iga e he
possible s eng hening mechanisms. The s ess-induced ans o med
monoclinic ac ion less han 2 µm below he ac u e su ace was es i-
ma ed by g azing incidence X- ay di ac ion (GIXRD, D8 Ad ance
B uke AXS di ac ome e , Bille ica, USA; a MATEIS). A Weibull mi o
was coupled o a ixed 0.2◦sli in he inciden beam o he di ac om-
e e . Scans we e aken in he c ack plane a e ac u e, om 27◦ o 33◦,
wi h a s ep size o 0.02◦and a ime pe s ep o 30 s. The V
m
was
calcula ed om he di ac og ams as desc ibed in sec ion §2.3.
3. Resul s and discussion
3.1. Analysis o he BNNS ob ained by shea ex olia ion in ki chen
blende
The liquid shea ex olia ion o h-BN pa icles was pe o med a h ee
di e en eloci ies –low, medium and high– o he ki chen blende , as
de ailed in sec ion §2.1.1. The ob ained BNNS suspensions a e e alua ed
in his sec ion o de e mine he op imal o o speed in e ms o ex oli-
a ion deg ee and p oduc ion a es. The pa icle size dis ibu ion o he
ob ained suspensions was join ly e alua ed by lase g anulome y
(Fig. 1a) and dynamic ligh sca e ing (Fig. 1b) due o hei echnical
limi a ions o measu ing ine and la ge pa icles, espec i ely. As shown
by he BNNS pa icle size dis ibu ion cu es, he majo i y o he
nanoshee s exhibi ed pa icle sizes below 1 µm, ega dless o he ex o-
lia ion eloci y, al hough a mino p opo ion we e ound in he 1–10 µm
ange. This is in ag eemen wi h p e iously epo ed size dis ibu ions o
BNNS ob ained by mechanical ex olia ion in liquid media, since wide
ange o nanoshee s sizes a e usually ound, commonly be ween 100 nm
and 1 µm [24,33,34]. The la ge pa icles may eme ge om ei he
s acked BNNS o poo ly ex olia ed h-BN nanopa icles ha we e no
p ope ly emo ed du ing cen i uga ion. Anyhow, hese echniques es-
ima e a sphe ical diame e , hus he nume ical alues he e ob ained
should only be conside ed as an es ima ion o he o de o magni ude o
he pa icle size, as p e iously men ioned in sec ion §2.1.1.
When compa ing he pa icle size dis ibu ion o he suspensions
ob ained a he di e en speeds, i can be es ablished ha inc easing he
ki chen blende eloci y p oduces la ge ac ions o smalle BNNS. The
main peak om he lase g anulome y analysis in Fig. 1a (cen e ed a ~
0.1 µm) in ensi ies o highe o o speeds, whe eas a second mino band
(~ 2 µm) educes i s in ensi y. Fu he mo e, highe eloci ies o he
ki chen blende o o also educe he size o la ge pa icles, as a second
peak a ~ 0.7 µm de elops simul aneously o he diminu ion o he 2 µm
band. E alua ion o he dynamic ligh sca e ing esul s (Fig. 1b), p o-
ides simila conclusions. The BNNS suspension ob ained a he lowes
speed p esen s a pa icle size dis ibu ion cen e ed a ~ 0.5 µm. Fo he
o he wo speeds (i.e. medium and high) he dis ibu ions a e cen e ed a
~ 0.3 µm, so an inc ease on he o o eloci y dec eases he ac ion o
la ge BNNS. Bo h echniques show a bimodal dis ibu ion o BNNS and
bo h poin o smalle nanoshee s sizes when using he ki chen blende a
i s medium and maximum powe (speeds 3 and 5). Howe e , dynamic
ligh sca e ing es ima es sligh ly la ge pa icle sizes han lase g an-
ulome y due o he dis inc physical phenomena employed o es i-
ma ing pa icle sizes in each echnique.
Fig. 1c illus a es he op ical abso p ion beha io o he ex olia ed
BNNS suspensions ob ained a he h ee ki chen blende eloci ies o e
he nea UV and he isible ligh spec um. All h ee spec a show simila
p o iles, indica ing sca e ing o he BNNS in solu ion nea he UV ange,
as p e iously epo ed [24,34]. The concen a ion o he BNNS sus-
pensions e alua ed by de e mining he abso bance o he dilu ed sus-
pensions a 300 nm anges om 0.07 o 0.22 mg ml
-1
a speed 5 o ~
0.05 mg ml
-1
a speeds 1 and 3. The suspended BNNS ob ained a he
highes o a ional speed (5) p omo e a g ea e sca e ing, indica ing ha
he amoun o ma e ial e ained was maximized o his ex olia ion
condi ion.
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
4
E en a he highe blende speed, he concen a ions o BNNS in
suspension a e no ou s anding, howe e , he easiness and apidi y o
his shea ex olia ion echnique, oge he wi h he la ge suspension
olumes ha can be p epa ed, make i an adequa e ou ine o he
p oduc ion o BNNS o use as ille s in composi e ma e ials. Since he
highes o o speed (5) o he ki chen blende inc eased he BNNS p o-
duc ion a e and p o ided a highe p opo ion o small-sized nanoshee s,
eloci y 5 o he ki chen blende was selec ed as he op imal condi ion
o he BNNS p oduc ion.
The s uc u al in eg i y o he nanoshee s was con i med o be in ac
by Raman spec oscopy (Fig. 1d). The E
2g
band o he ex olia ed BNNS is
cen e ed a ~ 1370 cm
-1
, p esen ing a blue-shi o ~ 4 cm
-1
ela i e o
ha o bulk h-BN (E
2g
a 1366 cm
-1
) [34–36]. P e ious s udies indica ed
ha an upshi o 2–4 cm
-1
e eals he p esence o monolaye h-BN
p edominan ly, in ag eemen wi h he phonon mode heo e ically ound
o his 2D ma e ial [34,35]. The e o e, he Raman analysis sugges s he
ob aining o p ima ily monolaye h-BN in he BNNS suspended a e
ex olia ion wi h he ki chen blende a speed 5.
TEM mic og aphs o hese nanoshee s (Fig. 2) allowed es ima ing he
eal plana size o he BNNS. Nume ous s acked nanoshee s a e shown in
Fig. 2a, illus a ing he wide pa icle size dis ibu ion (100–800 nm).
E alua ion o mo e han 30 indi idual nanoshee s e ealed ha BNNS
wi h sizes be ween 100 and 400 nm we e p edominan , wi h he spo-
adic obse a ion o nanoshee s la ge han 1 µm (Fig. 2b). These ob-
se a ions a e in ag eemen wi h he LG and DLS analyses, which
indica ed a signi ican p opo ion o small nanoshee s (sizes below 1
µm). The BNNS la e al sizes a e ex olia ion in he ki chen blende a e
signi ican ly lowe han hose epo ed o nanoshee s ob ained by o he
ex olia ion echniques, such as plane a y ball milling ex olia ion (sizes
up o ~3
μ
m) [11,33]. The mo phology o he BNNS can also be
desc ibed om hese images, which show hin ounded lamina es o
hose wi h diame e below 400 nm. The la ge nanoshee s a e also hin,
as shown by hei anspa ency and lexibili y (Fig. 2b) and exhibi ed a
mo e i egula shape wi h ounded edges. Finally, no holes o s uc u al
damage we e obse ed in he BN nanoshee s, and he 6- old symme y
was co obo a ed by high- esolu ion TEM (inse in Fig. 2b).
Fig. 1. a), b) Analysis o he pa icle size dis ibu ion o he BNNS suspensions ob ained a low (1), medium (3) and high (5) blende o o eloci ies by a) lase
g anulome y and b) dynamic ligh sca e ing; c) op ical abso bance spec a o he suspensions by UV– is spec oscopy, and d) Raman spec um o he BNNS
ex olia ed a speed 5.
Fig. 2. T ansmission elec on mic oscopy images o as-ex olia ed BNNS. High- esolu ion TEM image is p esen ed in b) as an inse .
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
5
3.2. Mic os uc u al cha ac e iza ion o he sin e ed composi es
Fully dense composi es (Table 1) wi h educed e agonal zi conia
(Z O1.95, JCPDS 01–081–1544) as he main c ys allog aphic phase
we e ob ained (XRD pa e ns no shown). The zi conia ma ix exhibi ed
submic ome ic g ain sizes (0.17–0.32
μ
m) ega dless he BNNS
concen a ion.
All he composi es p esen ed a homogeneous dis ibu ion o he
BNNS h oughou he zi conia ma ix. As an example, a ep esen a i e
BSE-SEM image om he composi e wi h 2.5 ol. % BNNS is p esen ed in
Fig. 3a. Mo eo e , a ma ked aniso opy is ob ained, wi h he basal plane
o he BN nanos uc u es (ho izon al di ec ion) o ien ed pe pendicula
o he SPS p essing axis ( e ical di ec ion). As p e iously discussed [11,
13], his p e e en ial o ien a ion is caused by he syne gic e ec o he
uniaxial p essu e exe ed du ing he SPS and he 2D s uc u e
mo phology o he BNNS.
The ac u e su ace o he composi e wi h 2.5 ol. % BNNS p e-
sen ed in Fig. 3b co obo a es he smalle dimension o he BNNS
ex olia ed in ki chen blende in compa ison wi h hose coming om
o he echniques such as plane a y ball milling ex olia ion [11,33]. The
hin BN nanoshee s a e loca ed be ween he zi conia ce amic g ains,
indi idually o in small g oups, and hey main ain he igid cha ac e
p e iously epo ed o BNNS [11,13,37].
3.3. Low empe a u e deg ada ion o he 3YTZP-BNNS composi es
A sigmoidal inc ease in he hyd o he mal deg ada ion is obse ed in
he ageing cu es o he zi conia ce amic and he composi es displayed
in Fig. 4a, which clea ly show ha he ac ion o monoclinic zi conia,
Vm,accele a es mo e apidly o e ageing ime in he zi conia e e ence
ce amic compa ed o he BNNS composi es. In addi ion o he
imp o emen o he LTD esis ance obse ed o all he composi es, since
hei ageing cu es a e sys ema ically lowe han ha o he monoli hic
zi conia, a mo e ema kable enhancemen wi h inc easing BNNS con-
en was also obse ed. Conside ing ha he zi conia g ain size in he
composi e wi h 1 ol. % BNNS is simila o ha o he e e ence 3YTZP
(see Table 1), he delay in LTD seems o be ela ed o he BNNS inco -
po a ion. Con a y o he expec ed beha io ha zi conia wi h a coa se
g ain size would unde go as e LTD deg ada ion [38], he composi e
wi h 2.5 ol. % BNNS demons a es an ageing a e compa able o ha o
i s coun e pa wi h 1 ol. %, no wi hs anding i s coa sened ma ix
mic os uc u e. Fu he mo e, he composi es wi h 2.5 and 5 ol. %
BNNS, bo h wi h simila coa sened ma ices show a signi ican
imp o emen in LTD esis ance compa ed o he monoli hic zi conia,
especially a he highes BNNS con en . Finally, he monoclinic ac ion
o 3YTZP ( e e ence) and all composi es con aining BNNS emains
below 10 % ollowing 5 h o exposu e o wa e apo a 134 ◦C, which
makes hem sui able o biomedical applica ions in acco dance wi h ISO
13356 s anda ds [39].
In he p esen s udy, he inco po a ion o BNNS has been shown o
ha e a bene icial in insic e ec on he e a da ion o zi conia LTD. No
seconda y in e phases a BNNS/zi conia in e aces a e expec ed based
on he exhaus i e HR-TEM s udy p e iously pe o med in pa ly hy-
d oxyla ed BN nanoshee s ein o ced zi conia composi es [11], exhib-
i ing mos ly ab up in e aces wi hou in e media e phases be ween he
BNNS and he zi conia g ains. Thus, he imp o emen in LTD esis ance
would no appea o be ela ed o he p esence o o he seconda y phases
a he g ain bounda ies. Ne e heless, he O
2
and H
2
O ba ie p ope ies
o bo on ni ide nanoshee s ha e been poin ed ou o be esponsible o
he p e en ion o mois u e pene a ion in o di e en ma e ials [10,11,
33,40]. The e ec i eness o bo on ni ide nanopla ele s in imp o ing he
wa e apo ba ie p ope ies in polyme composi es has also been
p e iously demons a ed [33,40]. Rega ding a zi conia ma ix, he
addi ion o a low quan i y o bo on ni ide nanoshee s (1.5 ol. %)
demons a ed a signi ican inhibi o y e ec on deg ada ion, as obse ed
in accele a ed low- empe a u e es s conduc ed o e a i e-hou pe iod
[10]. Following hese esul s, Lee e al. [10] p oposed a po en ial solu-
ion o he issue o low- empe a u e deg ada ion aking ad an age o he
wa e ba ie p ope ies o wo-dimensional hexagonal bo on ni ide
ille s, bu no u he s udies we e conduc ed on he e alua ion o LTD
a e di e en ime pe iods in an au ocla e o on he mic os uc u al
e ec s in ela ion o he p esence/absence o BN nano ille s (pla ele s o
shee s) in he g ain bounda y a eas. In he composi es analyzed in he
p esen s udy, he BN nanoshee s a e dis ibu ed h oughou he ma ix
wi h hei ab plane p e e en ially o ien ed pe pendicula o he p essing
axis du ing SPS, i.e. pa allel o he sample in-plane. Thus, any wa e
molecule a emp ing o each in o he ma ix is blocked by he nano-
shee s, which ac as mois u e ba ie and p e en he p opaga ion o he
-m ans o ma ion in o he composi e bulk in a e y e ec i e way,
esul ing in an imp o emen o he ageing esis ance.
As illus a ed in Fig. 4b, he bes linea eg ession o plo s ln(-ln(1-X)
e sus ln ( -
0
) demons a e compa able slopes o bo h he e e ence
ce amic and he composi es. Table 1 shows he kine ics pa ame e s n
and b in he KJMA equa ion ha a e essen ial o p edic ing he ageing
kine ics o composi es unde any leng h o s eam exposu e a 134 ◦C.
Rega dless he BNNS con en , a simila n alue (n≅1.2 ±0.2) is ob-
ained, which is consis en wi h p e ious obse a ions o 3YTZP com-
posi es con aining mul ilaye ed g aphene [9]. Wei and G emilla d [38]
ha e ecen ly e iewed he li e a u e on n alues o zi conia ce amics
doped wi h y ia, which sp ead o e a ange om 0.5 o 4. These alues
we e achie ed by applying a ious o ms o KJMA equa ion o i he -m
ans o ma ion cu es wi hou conside ing he induc ion ime in hei
exp essions. Thei indings indica e ha hese alues a e no a ec ed by
g ain size, y ium con en in he e agonal phase, o he ac ion o he
cubic phase. In line wi h his e iew, ou p e ious ou comes also sugges
he independence o he na u e o he inco po a ed impe meable
nanoshee s. The alues o he b-pa ame e sligh ly dec eased wi h
inc easing BNNS con en in he composi es, om b =0.028 ±0.09 h
-1
o he e e ence zi conia alue o 0.008 ±0.002 h
-1
o he composi e
wi h 5 ol. % BNNS, in ag eemen o he end o he e a ded onse o
ageing [38]. As al eady epo ed in 3YTZP ce amics, he n alues a ound
1 indica e ha he nuclea ion o he monoclinic phase is he dominan
ageing mechanism.
3.4. Assessmen o he s able c ack p opaga ion in he composi es
The ac u e oughness and R-cu e beha io we e only e alua ed on
he composi es wi h 1 and 2.5 ol. % BNNS, since p e ious s udies ha e
shown a dec ease in he mechanical pe o mance o zi conia composi es
when inco po a ing GBN con en s highe han 2.5 ol. % [30,41].
Table 2 summa izes he oughness and he R-cu e pa ame e s o he
3YTZP ( e e ence) and each 3YTZP-BNNS composi e.
The ac u e oughness o he composi es a ained simila alues o
hose o he e e ence zi conia, i.e. K
IC
~ 4.2 MPa⋅m
1/2
(Table 2). The
limi ed ac u e oughness o he ma e ials de eloped in his wo k is
ela ed o he e ined zi conia g ains p oduced by he ela i ely low SPS
empe a u es needed o densi ica ion. This g ain e inemen limi s he
Table 1
Rela i e densi y (
ρ
el
), zi conia mean g ain size (d) and s anda d de ia ion (s.d.)
and alues o he ageing pa ame e s (n and b) o he s udied ma e ials, including
he
2
o he KJMA linea plo i ing.
BNNS ol
%
ρ
el
(%)
d (µm)
σ
d
(µm) n b (h
-1
)
2
0 100 0.21 0.13 1.35 ±
0.07
0.028 ±
0.009
0.98849
1 99.7 0.17 0.07 1.13 ±
0.03
0.012 ±
0.002
0.99171
2.5 99.0 0.27 0.19 1.32 ±
0.07
0.012 ±
0.004
0.98313
5 100 0.32 0.15 0.93 ±
0.04
0.008 ±
0.002
0.97729
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
6
s ess-induced -m ans o ma ion oughening mechanism. P e ious
wo ks on se e al ce amic ma ices inco po a ing ei he BNNS o BNNP
ha e epo ed oughness enhancemen . Lee e al. [10] measu ed a 20 %
inc ease in SENB K
IC
on alumina-TZP composi es wi h he addi ion o 1
ol. % BNNP. Rein o cing Si
3
N
4
wi h 2 ol. % BNNP also p omo ed
oughe ma e ials when compa ed o he monoli hic ce amic [37].
Simila ly, Sun e al. [42] obse ed supe io oughness on used silica
composi es when inco po a ing up o ~ 5.5 ol. % BNNS. On he con-
a y, in ou p e ious s udy [11] we ha e epo ed no oughness
enhancemen o 3YTZP composi es wi h 2.5 ol. % BNNS ex olia ed by
hyd oxide assis ed milling. Thus, he in insic oughness o 3YTZP
composi es con aining BNNS and sin e ed by SPS emained unchanged,
ega dless o he con en (1 o 2.5 ol. %) and he manu ac u ing me hod
(blende ex olia ion o hyd oxyde-assis ed plane a y ball milling) o he
second phase.
Fig. 5 illus a es he R-cu es ob ained by he compliance me hod o
he wo composi es (1 and 2.5 ol. %) and he e e ence zi conia
(3YTZP) o e alua e he e ec o he BNNS con en . Table 2 ga he s he
R-cu e pa ame e s o each ma e ial a e aged om a leas h ee es s.
All he s udied ma e ials p esen almos la cu es, wi h an inc ease o
he c ack g ow h esis ance om he c ack- ip oughness o he pla eau
o up o ΔK
IR, h
~ 0.4 MPa⋅m
1/2
(Table 2), beha ing as ideally agile
ma e ials. The absence o a ising R-cu e o he composi es implies
ha he inco po a ion o hese BN nanoshee s as ille does no p omo e
signi ican inc easing esis ance o s able c ack g ow h. Among he
ex insic mechanisms ha could be aking pa in he oughening o
zi conia-based composi es, he s ess induced -m zi conia ans-
o ma ion and c ack b idging by second phase usually induce he
g ea es ein o cemen s [1]. The monoclinic con en on he ac u e
su ace o he composi e con aining 2.5 ol. % BNNS a e ailu e o he
SEVNB specimen, measu ed by g azing-incidence XRD, e ealed ha no
ans o ma ion occu ed in he ma e ial (Table 2). Fig. 6 shows SEM
mic og aphs o he ac u e su aces o he composi es a e he me-
chanical es s, e ealing ha he addi ion o BNNS inc eased he
ugosi y o he ac u e su ace due o c ack de lec ion, he inc ease in
ugosi y being mo e ema kable o he highes BNNS con en (Fig. 6d),
due o a g ea e de lec ion o he c ack du ing i s p opaga ion. Indeed,
he c ack plane ugosi y only accoun s o he c ack de lec ion du ing i s
p opaga ion, a less ein o cing mechanism han phase ans o ma ion o
b idging [1], and which may be also occu ing as a way o he c ack o
pu sue lowe -ene gy pa hs h ough weake in e aces [43,44]
Recen s udies on 3YTZP composi es inco po a ing high aspec - a io
GO (nanoshee s o educed g aphene oxide) o BNNS ha e ela ed he
enhanced esis ance o s able c ack g ow h o he low s acking o de and
la ge su ace a ea o he nanoshee s [11,30]. On he con a y, he low
la e al dimensions o ex olia ed g aphene nanopla ele s (e-GNP) ha e
been poin ed ou as he cause o he absence o ein o cemen on 3YTZP
Fig. 3. SEM mic og aphs o he composi e wi h 2.5 ol. % BNNS: a) polished c oss-sec ion su ace and b) ac u e su ace.
Fig. 4. a) Ageing cu es o he 3YTZP-BNNS composi es plo ed wi h he
monoli hic 3YTZP zi conia as e e ence; b) KJMA-plo linea i s o he expe -
imen al da a o de e mina ion o he ageing pa ame e s.
Table 2
Mechanical p ope ies o he composi es wi h BNNS and he e e ence 3YTZP:
SEVNB ac u e oughness (K
IC
), c ack ip oughness (K
I0
), R-cu e oughening
(ΔK
IR, h
) and monoclinic olume ac ion on ac u e su ace (V
m,
).
BNNS ol.
%
K
IC
(MPa⋅m
1/
2
)
K
I0
(MPa⋅m
1/
2
)
ΔK
IR, h
(MPa⋅m
1/2
)
V
m,
( ol. %)
0 4.2 ±0.1 3.3 ±0.1 0.3 0.8
1 4.2 ±0.2 3.9 ±0.2 0.1 No
measu ed
2.5 4.2 ±0.2 3.9 ±0.2 0.4 0.4
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
7
composi es [30]. Thus, he lack o enhanced esis ance o s able c ack
g ow h in he composi es s udied in he p esen wo k is consequence o
he small dimensions o he BNNS ex olia ed in he ki chen blende
(100–800 nm), as desc ibed in sec ion §3.1.
Al hough BNNS in his s udy do no p omo e ising R-cu es, he R-
cu e o bo h composi es is abo e ha o he monoli hic zi conia, wi h
an inc ease o abou 18 % on he c ack- ip oughness. The K
I0
inc ease in
he s udied composi es (~ 3.9 MPa m
1/2
) wi h espec o he monoli hic
zi conia (3.3 MPa m
1/2
) canno be ela ed o oughening by g ain g ow h
since all he ma e ials p esen simila g ain sizes (Table 1) and K
IC
alues
du ing uns able c ack p opaga ion (Table 2). Thus, i is concluded ha i
is a di ec e ec o he BNNS inco po a ion. Acco ding o li e a u e, he
di e ences in K
I0
wi h espec o K
IC
a e a sign o s ess-assis ed co o-
sion by wa e in zi conia [11]. Mo eo e , i has been epo ed ha o a
gi en zi conia ma e ial, he c ack g ow h esis ance (K
I0
) can change
om ~ 3 MPa m
1/2
in wa e o ~ 5 MPa m
1/2
unde acuum condi ions
[45]. Thus, esis ance o s able c ack g ow h was s udied in he p esen
wo k also on oil-imp egna ed SEVNB specimens in o de o gua an ee no
con ac wi h he en i onmen al humidi y. The R-cu e o he composi e
wi h 2.5 ol. % BNNS assessed on oil-imp egna ed specimens e ealed
an almos iden ical cu e o he analogous in ai (Fig. 7). Su p isingly,
he isola ion o he c ack ip om he en i onmen al humidi y did no
change he esul ing cu es, which showed equal oughness a he onse
o c ack p opaga ion han hei analogous in ai . The shape o he
Fig. 5. C ack g ow h esis ance cu es o he 3YTZP composi es wi h 1 and 2.5 ol. % BNNS. The e e ence monoli hic zi conia is included o compa ison pu poses.
Fig. 6. SEM images o he ac u e su aces a e bending es s a di e en magni ica ions o : a) he monoli hic 3YTZP zi conia, and he composi es wi h b) 1 ol. %
BNNS and c) and d) 2.5 ol. % BNNS. In all hese images, he c ack p opaga ed om op o bo om, pa allel o he SPS p essing axis.
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
8
R-cu es also emained unchanged, e ealing ha he BN nanoshee s
we e no de e io a ed by he p esence o wa e . Thus, i can be
concluded ha , as he c ack on ad ances and he c ack ip line en-
coun e s he BNNS ab plane, he nanoshee s hinde he wa e molecules
om eaching he ma ix in he same way ha we ha e men ioned in
Sec ion §3.3. Since he BN nanos uc u es a e e y inely dispe sed, he
p opo ion o hese submic ome ic-sized nanoshee s be ween he zi -
conia g ains is much highe han ha achie ed wi h ni ide o ca bide
pa icles conside ing simila ol. % addi ion [1]. Consequen ly, he
BNNS ad an ageously educe he wa e con ac in o zi conia g ains a
he on o c acks, hence, es aining he zi conia co osion by slow
c ack g ow h.
4. Conclusions
Bo on ni ide nanoshee s mos ly ha ing plana diame e s in he
ange o 100 - 400 nm we e success ully ex olia ed h ough an easy and
en i onmen ally iendly p ocedu e using a low-cos ki chen blende .
The inco po a ion o BNNS con en s up o 5 ol. % in 3YTZP zi conia
esul ed in almos ully dense composi es a e SPS sin e ing o sub-
mic ome ic zi conia g ain size, wi h a homogeneous aniso opic dis-
ibu ion o he BN nanoshee s h oughou he ma ix.
A ema kable imp o emen o he ageing esis ance was achie ed in
all he 3YTZP-BNNS composi es, hanks o he blocking o he wa e
molecules a emp ing o each in o he ma ix by he nanoshee s, which
ac as mois u e ba ie and p e en he p opaga ion o he spon aneous
-m ans o ma ion. The long- e m eliabili y o he zi conia-BNNS
composi es in e ms o ageing deg ada ion was demons a ed.
Al hough he composi es p esen ed a agile pe o mance wi h ac u e
oughness alues simila o hose o he e e ence zi conia, an inc ease o
~18 % on he c ack- ip oughness was achie ed. Almos iden ical R-
cu es we e assessed in ai and in oil-imp egna ed specimens o he
composi e wi h 2.5 ol. % BNNS, e ealing a es ained s ess-assis ed
co osion by wa e in zi conia, hanks o he BNNS inco po a ion.
The homogeneous dis ibu ion o BNNS a he zi conia g ain
bounda ies ep esen s a p omising app oach o enhance he hyd o-
he mal ageing s abili y o 3YTZP ce amics while simul aneously
inc easing hei in insic c ack esis ance.
CRediT au ho ship con ibu ion s a emen
C. Mu˜
noz-Fe ei o: W i ing – o iginal d a , Me hodology, In es i-
ga ion. A. Mo ales-Rod íguez: W i ing – e iew & edi ing, W i ing –
o iginal d a , Valida ion, Supe ision, Resou ces, P ojec adminis a-
ion, Me hodology, In es iga ion, Funding acquisi ion, Da a cu a ion,
Concep ualiza ion. H. Re e on: W i ing – e iew & edi ing, Visualiza-
ion, Valida ion, Supe ision, Me hodology, In es iga ion, Da a cu a-
ion, Concep ualiza ion. E. Guisado-A enas: Me hodology,
In es iga ion. S. Co ino: Me hodology, In es iga ion. P. Mo eno:
Me hodology, In es iga ion. J. P ada-Rod igo: Me hodology, In es i-
ga ion. J. Che alie : W i ing – e iew & edi ing, Visualiza ion, Vali-
da ion, Supe ision, Me hodology, In es iga ion, Da a cu a ion,
Concep ualiza ion. ´
A. Galla do-L´
opez: W i ing – e iew & edi ing,
Visualiza ion, Valida ion, Supe ision, Resou ces, P ojec adminis a-
ion, Me hodology, In es iga ion, Funding acquisi ion, Da a cu a ion,
Concep ualiza ion. R. Poya o: W i ing – e iew & edi ing, W i ing –
o iginal d a , Visualiza ion, Valida ion, Supe ision, Resou ces, P ojec
adminis a ion, Me hodology, In es iga ion, Funding acquisi ion, Da a
cu a ion, Concep ualiza ion.
Decla a ion o compe ing in e es
The au ho s decla e ha hey ha e no known compe ing inancial
in e es s o pe sonal ela ionships ha could ha e appea ed o in luence
he wo k epo ed in his pape .
Acknowledgemen s
This esea ch was suppo ed by p ojec s PID2022–140191NB-I00
and PID2020–119003GB-I00 unded by MCIN/AEI/ 10.13039/
501100011033 and by FEDER, UE. C. Mu˜
noz-Fe ei o acknowledges he
inancial suppo o a VI PPIT-US (Plan P opio Uni e sidad de Se illa,
Spain) ellowship h ough he con ac USE-18740-H. The au ho s a e
g a e ul o he JECS T us o unding he isi o C. Mu˜
noz-Fe ei o o
MATEIS Labo a o y (INSA Lyon) (Con ac No. 2020248). The au ho s
hank P o . J.S. Bl´
azquez (Uni e si y o Se ille) o his ad ice and
assis ance ega ding he KJMA model.
Fig. 7. C ack g ow h esis ance cu es o he composi e wi h 2.5 ol. % BNNS measu ed in ai (con inuous line) and in oli e oil (symbols).
C. Mu˜
noz-Fe ei o e al.
Open Ce amics 23 (2025) 100816
9
