Ci a ion: Pi ala, R.K.; Sha ma, P.;
Anne, G.; Pa il, S.; Va ghese, V.; Das,
S.R.; Kuma , C.S.; Fe nandes, F.
De elopmen and Mechanical
Cha ac e iza ion o Ni-C Alloy
Foam Using Ul asonic-Assis ed
Elec opla ing Coa ing Technique.
Coa ings 2023,13, 1002. h ps://
doi.o g/10.3390/coa ings13061002
Academic Edi o : Kei h J. S ine
Recei ed: 22 Ap il 2023
Re ised: 21 May 2023
Accep ed: 24 May 2023
Published: 28 May 2023
Copy igh : © 2023 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
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coa ings
A icle
De elopmen and Mechanical Cha ac e iza ion o Ni-C Alloy
Foam Using Ul asonic-Assis ed Elec opla ing
Coa ing Technique
Raj Kuma Pi ala 1, P iya anjan Sha ma 1,* , Gajanan Anne 2, Sachinkuma Pa il 3, Vinay Va ghese 4,
Sudhansu Ranjan Das 5,* , Ch Sa eesh Kuma 6,7,* and Filipe Fe nandes 8,9
1Depa men o Mechanical Enginee ing, Kone u Lakshmaih Educa ion Founda ion,
Vaddeswa am 522502, Andh a P adesh, India
2Depa men o Mechanical and Indus ial Enginee ing, Manipal Ins i u e o Technology,
Manipal Academy o Highe Educa ion, Manipal 576104, Ka na aka, India; [email p o ec ed]
3Depa men o Mechanical Enginee ing, REVA Uni e si y, Bangalo e 560064, Ka na aka, India;
sachinkuma [email p o ec ed]
4Depa men o Mechanical Enginee ing, Adishanka a Ins i u e o Enginee ing & Technology,
Cochin 683574, Kalady, India; [email p o ec ed]
5Depa men o P oduc ion Enginee ing, Vee Su end a Sai Uni e si y o Technology,
Bu la 768018, Odisha, India
6CFAA-Ae onau ics Ad anced Manu ac u ing Cen e , Uni e si y o he Basque Coun y (UPV/EHU),
Biscay Science and Technology Pa k, Ed. 202, 48940 Zamudio, Spain
7Depa men o Mechanical Enginee ing, Uni e si y o he Basque Coun y, Escuela Supe io de Ingenie os
Alameda de U quijo S/N, 48013 Bilbao, Spain
8Depa men o Mechanical Enginee ing, ARISE, CEMMPRE, Uni e si y o Coimb a, Rua Luís Reis San os,
3030-788 Coimb a, Po ugal; [email p o ec ed]
9ISEP, Poly echnic o Po o, Rua D . An ónio Be na dino de Almeida, 4249-015 Po o, Po ugal
*Co espondence: [email p o ec ed] (P.S.); [email p o ec ed] (S.R.D.);
[email p o ec ed] (C.S.K.)
Abs ac :
Me al oams and alloy oams a e a no el class o enginee ing ma e ials and ha e nume ous
applica ions because o hei p ope ies such as high ene gy abso p ion, ligh weigh and high
comp essi e s eng h. In he p esen s udy, he me hodology adop ed o de elop a Ni-C alloy
oam is discussed. Polyu e hane (PU) oam o 40PPI (pa s pe inch) po e densi y was used as
he p ecu so and coa ing echniques such as elec oless nickel pla ing (ELN), ul asonic-assis ed
elec opla ing o nickel (UAEPN), and pack cemen a ion o ch omizing we e used o de elop he
Ni-C alloy oam. The su ace mo phology, s u hickness and minimum weigh gain a e each
coa ing s age we e e alua ed. I was obse ed om he esul s ha he adop ed coa ing echniques
did no damage he o iginal ligamen c oss-sec ion o he PU p ecu so . The minimum weigh
gain and he coa ing hickness a e he UAEPN p ocess we e obse ed o be 42 g and 40–60
µ
m,
espec i ely. The p ope ies such as po osi y pe cen age, pe meabili y and comp essi e s eng h
we e e alua ed. Finally, he p essu e d op h ough he de eloped oam was es ima ed and e i ied o
de e mine whe he he de eloped oam can be used o il e ing applica ions.
Keywo ds: Ni-C alloy oam; elec oless nickel pla ing; ul asonic-assis ed; ch omizing; po osi y
1. In oduc ion
Po ous ma e ials such as alloy oams and me al oams ha e abundan enginee ing
applica ions due o hei excep ional physical and mechanical p ope ies. Basically, an
alloy o me al oam is a cellula s uc u e ha has a solid ma ix made o an alloy o me al
wi h emp y oids. I he oids a e connec ed by means o open po es, hen he oam is
desc ibed as an open-cell oam, and i he oids a e no connec ed by open channels and a e
disconnec ed by solid walls hen he oam is said o be a closed-cell oam. Alloy oams o e
Coa ings 2023,13, 1002. h ps://doi.o g/10.3390/coa ings13061002 h ps://www.mdpi.com/jou nal/coa ings
Coa ings 2023,13, 1002 2 o 12
signi ican pe o mance gain in ligh and s i s uc u es o high ene gy abso p ion, be e
he mal managemen and high comp essi e s eng h [
1
]. These oams a e ep oducible and
non- oxic. Thus, oams a e one o he bes ligh weigh ma e ials ha can be employed in
many unc ional and s uc u al applica ions.
Mos comme cially exis ing me al oams a e based on coppe , nickel, zinc, aluminum,
i anium and hei alloys. Aluminum alloy oams a e mainly used in sound abso p ion,
he mal insula ion and ib a ion con ol applica ions [
2
]. Nickel-based alloy oams such as
Ni-C oams combine good mechanical p ope ies and be e co osion esis ance a oom
empe a u e as well as o high- empe a u e applica ions. Because o hei low densi y,
high speci ic a ea and good duc ili y, Ni-C alloy oams can be used as sandwich-s uc u e
co e ma e ial and o mechanical damping applica ions [
3
]. These oams a e also used o
p oduce nea -ne -shape complex componen s, and o il e ing and sepa a ion applica ions,
due o hei unique mic os uc u e. Chao-Heng e al. [
4
] in es iga ed a nickel oam o
pho oca aly ic il e ing applica ions and concluded ha he emo al o o maldehyde om
indoo ai is made be e by inco po a ing he nickel oam in a s anda d ai il e .
Se e al echniques such as slu y oaming [
5
,
6
], di ec oaming wi h a blowing
agen [
7
,
8
], in es men cas ing [
9
,
10
] and elec ochemical deposi ion [
11
–
13
] a e a ail-
able o ab ica e alloy oams. The mic os uc u e and mechanical p ope ies o he oam
g ea ly depends on he ab ica ion echnique. To use he de eloped oam o il e ing and
sepa a ion applica ions, main aining he o iginal po osi y, ligamen o s u s uc u e is
necessa y o be e unc ional pe o mance. Hence, in he p esen s udy, elec ochemical
deposi ion echniques we e used o de elop Ni-C alloy oams. Duan e al. [
14
] de eloped
a Ni-C alloy oam using elec odeposi ion echniques and in es iga ed he a ious p ocess
pa ame e s o op imiza ion o he mic os uc u e and highe elec ical esis i i y. Pang Qiu
e al. [
15
] syn hesized Ni-Fe-C alloy oams employing gas-phase co-deposi ion echniques
and s udied hei comp essi e and ene gy abso p ion p ope ies. They concluded ha bo h
p ope ies we e inc eased wi h an inc ease in C con en in he de eloped oam.
The mechanical p ope ies o he cellula s uc u es depend on he po e size, ela-
i e densi y, s u ma e ial and po osi y pe cen age. Michailidis e al. [
16
] ab ica ed an
open-cell aluminum oam using a space holde echnique and e alua ed i s comp essi e
s eng h. I was unde s ood om hei s udy ha he s ess–s ain cu e o he oam
depends on he po e size and ha he comp essi e s eng h educes wi h enhancemen
o he po osi y pe cen age. Kaplon e al. [
17
] used wo di e en polyu e hane (PU) oam
ma e ials as p ecu so ma e ials and de eloped open-po osi y magnesium oam using an
in es men -cas ing echnique, and hey examined i s mic os uc u e, co osion esis ance
and mechanical comp essi e s eng h. Zhang e al. [
18
] de eloped geopolyme oams
by employing aluminum and H
2
O
2
-sodium olea e as oaming agen and op imized he
po e s uc u e. Chemical composi ions and mic os uc u e we e analyzed using Fou ie
ans o m in a ed spec oscopy and X- ay di ac ion (XRD) echniques and hey measu ed
he pe meabili y and low p ope ies using a pe meame e .
F om he li e a u e su ey, i can be summa ized ha a ew s udies [
17
,
19
,
20
] ha e used
aluminum, zinc, magnesium and coppe me als as oams, while some o he
s udies [
14
,
15
,
21
] ha e used nickel alloys, aluminum alloys and i anium-based coppe
alloys as oams. In a ew wo ks [
7
,
8
,
10
], mel oaming, di ec oaming wi h a blowing
agen , and in es men cas ing we e used o ab ica e me al o alloy oams. In a ew o he
wo ks [
19
,
22
–
24
], elec odeposi ion echniques and powde me allu gy me hods we e used
o ab ica e alloy oams. Some s udies [
25
–
27
] in es iga ed he mic os uc u e, mechanical
p ope ies and p ocess pa ame e s o he de eloped oams, and some o he s udies [
28
,
29
]
concen a ed on he unc ional pe o mance and op imum po e-size s uc u e. O e all,
nickel-based and aluminum-based open-cell oams ha e been discussed wi hou much
ocus on he luid low cha ac e is ics and pe meabili y calcula ions.
Because o new ad ancemen s in he ae ospace, de ense and au omo i e indus ies,
he e is a la ge demand o ligh weigh s uc u es which can be used as il e ing media, as
well as s uc u al componen s o inc ease uel e iciency and unc ional pe o mance. Thus,
Coa ings 2023,13, 1002 3 o 12
o sa is y hese equi emen s, he de elopmen me hodology o such a no el s uc u al
ma e ial, a Ni-C alloy oam, is discussed in he p esen s udy. As pe he knowledge o he
au ho s, he e is no s udy a ailable on Ni-C oams which add esses hei p ocess capabili y,
p essu e d op and pe meabili y calcula ions. Ve y limi ed s udies a e a ailable on he
syn hesis o Ni-C alloy oams using elec odeposi ion echniques. Thus, he objec i es
o he p esen s udy a e (i) o discuss he me hodology adop ed o de elop a Ni-C alloy
oam and i s p ocess pa ame e s’ op imiza ion; (ii) o e alua e he p ocess capabili y o he
a ious me hods used o de elop such a oam; and (iii) o de e mine i s po osi y pe cen age,
pe meabili y, p essu e d op and mechanical comp essi e s eng h.
2. Ma e ials and Me hods
2.1. Ma e ials
Polyu e hane oam ha ing 40 PPI (pa s pe inch) po e densi y and a s u hickness o
100–110
µ
m was aken as p ecu so and pu chased om Sheela oam L d., Noida, India. All
he eagen s used in he elec oless nickel pla ing (ELN), ul asonic-assis ed elec opla ing
o nickel (UAEPN) and pack ch omizing we e o analy ical g ade and pu chased om
Al a Aesa , Mumbai, India. Demine alized (DM) wa e was used o p epa e di e en ba h
composi ions.
2.2. Syn hesis o Ni-C Alloy Foam
Figu e 1shows a schema ic ep esen a ion o he Ni-C alloy oam de elopmen
me hodology. The me hodology adop ed o de elop he Ni-C oam was mainly elec-
odeposi ion echniques and solid-s a e di usion echniques. Ini ially, PU oam ha ing
60
×
60
×
15 mm
3
dimensions and 40 PPI was aken as a base ma e ial and me allized
using an elec oless nickel-pla ing echnique. The de ailed ba h composi ion and he ELN
p ocedu e a e desc ibed in Figu e 2. As an ou pu o he ELN p ocess, a hin laye o
Ni a oms was deposi ed on he p ecu so oam. The op imized p ocess pa ame e s we e
empe a u e: 90–95
◦
C, ime: 50–60 min and pH: 4.5–5.5. In o de o achie e uni o m
deposi ion and he equi ed hickness o Ni coa ing on he me allized oam, an ul asonic-
assis ed elec opla ing o nickel (UAEPN) echnique was used. Table 1 ep esen s he
ba h composi ion and ope a ing pa ame e s used in he s udy. The p ocess scheme o he
UAEPN echnique is shown in Figu e 3. The ELN-coa ed Ni oam was used as ca hode,
while wo nickel pla es o size 80
×
80
×
15 mm
3
we e used as anodes du ing he UAEPN
p ocess. La e , in o de o emo e he PU p ecu so om he de eloped Ni oam, sin e ing
was ca ied ou a 1100
◦
C o 1 h. A esis ance-hea u nace o 9 kW capaci y and educing
a mosphe e (H
2
) was used du ing sin e ing. In he sin e ing p ocess, he PU p ecu so was
bu n ou a 450–500
◦
C and s eng hening o he EPN oam was ca ied ou by c ea ing
bonding be ween he pla ed Ni pa icles.
Coa ings 2023, 13, x FOR PEER REVIEW 4 o 14
Figu e 1. Schema ic illus a ion o Ni-C alloy oam de elopmen me hodology.
Figu e 2. P ocess scheme o ELN echnique.
Figu e 3. P ocess scheme o UAEPN echnique.
To deposi he ch omium on he sin e ed Ni oam, a ch omizing o pack-cemen a ion
p ocess was used. Ch omizing is a solid-s a e diffusion p ocess in which diffusion hap-
pens h ough he diffe ence in concen a ions o he deposi ing ma e ial. To s a wi h he
Figu e 1. Schema ic illus a ion o Ni-C alloy oam de elopmen me hodology.
Coa ings 2023,13, 1002 4 o 12
Coa ings 2023, 13, x FOR PEER REVIEW 4 o 14
Figu e 1. Schema ic illus a ion o Ni-C alloy oam de elopmen me hodology.
Figu e 2. P ocess scheme o ELN echnique.
Figu e 3. P ocess scheme o UAEPN echnique.
To deposi he ch omium on he sin e ed Ni oam, a ch omizing o pack-cemen a ion
p ocess was used. Ch omizing is a solid-s a e diffusion p ocess in which diffusion hap-
pens h ough he diffe ence in concen a ions o he deposi ing ma e ial. To s a wi h he
Figu e 2. P ocess scheme o ELN echnique.
Table 1. Ba h composi ion and p ocess pa ame e s o UAEPN echnique.
P ocess Ba h Composi ion Ope a ing Pa ame e s
UAEPN
Ni sal (NiSO4·6H2O + NiCl2·6H2O): 350 g/L Cu en : 7–8.5 A
Vol age: 10–12 V
pH: 4–5
Du a ion: 300–360 min
Bo ic acid: 20 g/L
Sodium sulpha e: 15 g/L
Omni addi i e 992: 8 mL/L
Magnum b igh ene 437: 10 mL/L
Coa ings 2023, 13, x FOR PEER REVIEW 4 o 14
Figu e 1. Schema ic illus a ion o Ni-C alloy oam de elopmen me hodology.
Figu e 2. P ocess scheme o ELN echnique.
Figu e 3. P ocess scheme o UAEPN echnique.
To deposi he ch omium on he sin e ed Ni oam, a ch omizing o pack-cemen a ion
p ocess was used. Ch omizing is a solid-s a e diffusion p ocess in which diffusion hap-
pens h ough he diffe ence in concen a ions o he deposi ing ma e ial. To s a wi h he
Figu e 3. P ocess scheme o UAEPN echnique.
To deposi he ch omium on he sin e ed Ni oam, a ch omizing o pack-cemen a ion
p ocess was used. Ch omizing is a solid-s a e di usion p ocess in which di usion happens
h ough he di e ence in concen a ions o he deposi ing ma e ial. To s a wi h he
ch omizing p ocess, i s , ball milling o he ch ome pack was ca ied ou . The ch ome
pack consis ed o 55 w .% C powde , 15 w .% NH
4
Cl (ac i a o ) and 30 w .% Al
2
O
3
( ille
ma e ial). The powde s we e ca e ully mixed using a mo a and pes le and unde wen
high-ene gy ball milling o 5 h. Ball milling o he pack ensu ed uni o m mixing (blending)
o powde s and educ ion in he powde pa icle size. Then, he en i e pack composi ion
was collec ed and kep in an SS ay o size 65
×
70
×
15 mm
3
. Then, he ay was loaded
wi h sin e ed Ni oam and he pack composi ion and loaded in he esis ance u nace and
Coa ings 2023,13, 1002 5 o 12
allowed o hea up o 1100
◦
C a a hea ing a e o 8
◦
C/min. A gon was used as a shielding
gas o a oid oxida ion o he oam du ing ch omizing. The sample was soaked o 6 h a
1100 ◦C and hen allowed o u nace cooling.
2.3. Cha ac e iza ion Techniques
Di e en cha ac e iza ion echniques such as scanning elec on mic oscopy (SEM), X-
ay di ac ion (XRD), elec on dispe si e spec oscopy (EDS) (TESCAN ORSAY HOLDING,
B no, Czech Republic) and comp ession es s we e pe o med o e alua e he mic os uc u e
and mechanical beha io o he de eloped alloy oam.
S u hickness, mo phology and elemen al mapping o he de eloped oam we e
examined using Vega 3 TESCAN SEM (TESCAN ORSAY HOLDING, B no, Czech Republic)
a a wo king dep h o 10–11 mm and 10 kV ol age.
In o de o know he phase o ma ions and alloys o med be ween he Ni and C , XRD
(Philips, Cae philly, UK) analysis was used. The de eloped oam and a Ni 60 C 40 solid
sample we e compa ed using XRD o con i m he bonding be ween he Ni and C elemen s.
The quasi-s a ic comp ession beha io and he maximum comp essi e s eng h o
he de eloped oam we e examined using a 50 kN load cell Uni e sal Tes ing Machine
(UTM—Jin Ahn Tes ing, Suzhou, China). A cylind ical specimen o 12 mm diame e and
15 mm heigh was conside ed and es ed acco ding o he ASTM C365-05 s anda d. The
lowes possible dimension o he sample was selec ed, such ha i should be a leas se en
imes he cell size o a oid size e ec s. Specimens we e kep on he bo om am o he UTM
machine and load was applied o he specimens when he op am mo ed downwa ds a a
cons an c oss-head speed o 0.5 mm/min.
2.3.1. Measu emen o Theo e ical Po osi y
The heo e ical po osi y o he de eloped oam was measu ed by using he wa e
displacemen me hod and Equa ion (1).
Po osi y(%)=Po es olume (S−D)
Bulk olume (S−I)(1)
whe e S, D and I indica e he weigh o a sa u a ed sample, a d y sample and a sample
imme sed in wa e , espec i ely.
The weigh o a sa u a ed sample indica es he weigh o he oam when i s po es a e
sealed wi h wa e . Thus, he weigh o wa e in po e space = S
−
D and he weigh o wa e
displaced = S −I.
Po es Volume Vp=wWa e (S−D)
densi ywa e
(2)
I we conside he densi y o wa e o be 1 g/cc, hen he po es olume will be equal
o he weigh o wa e in po e space. Simila ly, he bulk olume can be exp essed in e ms
o he weigh o wa e displaced.
2.3.2. Measu emen o Pe meabili y and P essu e D op h ough Foam
The de eloped oam can ha e applica ion as an oil–ai sepa a o ; hence, o suppo i s
unc ionali y, he measu emen o i s pe meabili y and p essu e d op h ough i is necessa y.
Pe meabili y is a p ope y o po ous ma e ials which indica es he ease o low o luids
h ough hem. Since he po osi y o oam a ies a he di e en p ocessing s ages o he
oam, i is also necessa y o e alua e pe meabili y a hose s ages.
Tad is e al. [
30
] de i ed he ela ionship be ween he p essu e d op (dp), he po osi y
(ε) o he medium and an a e age pa icle diame e (dP) using Equa ion (3).
dP
dX =A1−ε)2
ε3dP2µV+B(1−ε)
ε3dP
ρV2(3)
Coa ings 2023,13, 1002 6 o 12
A and B a e he cons an s which di e acco ding o he po ous medium. Fo he Ni-C
oam po ous medium, he alues o A and B can be aken as 100 and 1.0, espec i ely.
µ
, V
indica es dynamic iscosi y and eloci y o he luid, dX ep esen s hickness o he oam
and ρ-densi y o he luid.
The ela ionship be ween pa icle diame e (d
p
) and po e size (d) o he oam is gi en
by Equa ion (4).
dp=1.51−ε
εd(4)
The ela ionship be ween pe meabili y (K), heo e ical po osi y (
ε
) and pa icle diame-
e (dp) is gi en by Equa ion (5).
K=dp2ε3
A(1−ε)2(5)
3. Resul s and Discussion
3.1. Su ace Mo phology and P ocess Capabili y o ELN- and UAEPN-Coa ed PU Foams
In o de o examine he ligamen c oss-sec ion o he oam and o e alua e he coa ing
hickness, SEM analysis was used. Figu e 4shows he su ace mo phology and he s u
hickness o he ELN- and UAEPN-coa ed oams, and he p ocess capabili y o he ELN
and UAEPN p ocesses. I can be no ed om he esul s ha ELN-coa ed oam has s u
hickness in he ange o 115–125
µ
m and ha o he UAEPN-coa ed oam is in he ange o
160–180
µ
m. As he s u hickness o he PU p ecu so was 100–110
µ
m, hese mo phology
esul s indica e ha he hickness o he coa ing a e he ELN p ocess was a ound 15–25
µ
m
and a e he UAEPN p ocess i was a ound 40–60
µ
m. To e alua e he p ocess capabili y o
he ELN and UAEPN p ocesses, 10 di e en oam samples o he same size we e conside ed
and coa ed using he same p ocess pa ame e s. I was obse ed om he esul s ha he
minimum weigh gain a e he ELN p ocess was a ound 2 g and a e he UAEPN p ocess
i was a ound 42 g. Thus, om his s udy, i can be concluded ha he selec ed p ocess
pa ame e s can be ea ed as he ideal pa ame e s.
Coa ings 2023, 13, x FOR PEER REVIEW 8 o 14
3. Resul s and Discussion
3.1. Su ace Mo phology and P ocess Capabili y o ELN- and UAEPN-Coa ed PU Foams
In o de o examine he ligamen c oss-sec ion o he oam and o e alua e he coa ing
hickness, SEM analysis was used. Figu e 4 shows he su ace mo phology and he s u
hickness o he ELN- and UAEPN-coa ed oams, and he p ocess capabili y o he ELN
and UAEPN p ocesses. I can be no ed om he esul s ha ELN-coa ed oam has s u
hickness in he ange o 115–125 µm and ha o he UAEPN-coa ed oam is in he ange
o 160–180 µm. As he s u hickness o he PU p ecu so was 100–110 µm, hese mo -
phology esul s indica e ha he hickness o he coa ing a e he ELN p ocess was a ound
15–25 µm and a e he UAEPN p ocess i was a ound 40–60 µm. To e alua e he p ocess
capabili y o he ELN and UAEPN p ocesses, 10 diffe en oam samples o he same size
we e conside ed and coa ed using he same p ocess pa ame e s. I was obse ed om he
esul s ha he minimum weigh gain a e he ELN p ocess was a ound 2 g and a e he
UAEPN p ocess i was a ound 42 g. Thus, om his s udy, i can be concluded ha he
selec ed p ocess pa ame e s can be ea ed as he ideal pa ame e s.
Figu e 4. (a) Ac ual sample and (b) s u hickness o ELN-coa ed oam; (d) ac ual sample and (e)
s u hickness o UAEPN-coa ed oam; p ocess capabili y o (c) ELN p ocess and ( ) UAEPN p o-
cess.
3.2. Su ace Mo phology and P ocess Capabili y o Ch omized Foam
In o de o con i m ha he de eloped oam has good mechanical p ope ies, i was
necessa y o examine he s u in eg i y in all he s ages o de elopmen . Figu e 5 shows
he mo phology and s u in eg i y o ch omized oam. I was obse ed om he esul s
ha he ch omized oam did no ha e any s u disconnec ions o ailu es; hence, i was
con i med ha he ch omizing p ocess did no des oy he s u in eg i y. The ch omized
oam had s u hickness o a ound 250–260 µm and a minimum weigh gain o 6.75 g. All
he esul s e alua ed o he p ocess capabili y o he ch omizing p ocess showed con-
sis en and p omising esul s. Hence, he ch omizing p ocess can be used o deposi he
ch omium on he sin e ed Ni oam.
Figu e 4.
(
a
) Ac ual sample and (
b
) s u hickness o ELN-coa ed oam; (
d
) ac ual sample and (
e
) s u
hickness o UAEPN-coa ed oam; p ocess capabili y o (c) ELN p ocess and ( ) UAEPN p ocess.
Coa ings 2023,13, 1002 7 o 12
3.2. Su ace Mo phology and P ocess Capabili y o Ch omized Foam
In o de o con i m ha he de eloped oam has good mechanical p ope ies, i was
necessa y o examine he s u in eg i y in all he s ages o de elopmen . Figu e 5shows
he mo phology and s u in eg i y o ch omized oam. I was obse ed om he esul s
ha he ch omized oam did no ha e any s u disconnec ions o ailu es; hence, i was
con i med ha he ch omizing p ocess did no des oy he s u in eg i y. The ch omized
oam had s u hickness o a ound 250–260
µ
m and a minimum weigh gain o 6.75 g. All
he esul s e alua ed o he p ocess capabili y o he ch omizing p ocess showed consis en
and p omising esul s. Hence, he ch omizing p ocess can be used o deposi he ch omium
on he sin e ed Ni oam.
Coa ings 2023, 13, x FOR PEER REVIEW 9 o 14
Figu e 5. (a) Ch omized oam and i s (b) s u hickness and (c) p ocess capabili y.
3.3. EDS and XRD Analysis o Ni-C Alloy Foam
To e alua e he bonding and he phase o ma ions be ween he Ni and C elemen s,
EDS and XRD analyses we e pe o med on he oam. Figu e 6 shows he line scanning
and EDS spec um o de eloped Ni-C alloy oam. I can be no ed om he esul s ha
he Ni and C elemen s we e uni o mly dis ibu ed h oughou he oam and he weigh %
o Ni was 71.56, C was 22.65 and oxygen was 2.17. This esul indica ed ha , hough he
bonding occu ed be ween he Ni and C elemen s, oxida ion o C also happened. This
oxida ion phenomena can be a ibu ed o an imp ope ine -gas low du ing ch omizing
and can be con olled by a ho ough cleaning o he u nace and sample, and by main ain-
ing he a gon gas low a e a 2 ba . EDS analysis alone is no sufficien o con i m he
bonding be ween he Ni and C elemen s; hence, o con i m he bonding and o es ima e
he phase o ma ions, XRD analysis was used. The esul s we e compa ed wi h e e ence
pa e ns in X’Pe HighSco e and con i med he o ma ion o Ni
2
C and Ni
2
C
4
O
7
com-
pounds. In addi ion, o suppo he esul s, he XRD spec um o he de eloped oam was
compa ed wi h a Ni-C (60:40%) solid sample. I can be obse ed om he esul s ha
majo peaks o bo h spec ums we e ma ching and, hence, i should be concluded ha he
de eloped oam has good bonding be ween Ni and C . I can also be no ed om he XRD
esul s ha he Ni-C oam had body-cen e ed cubic s uc u e. Thus, he esul s con i med
he comple e diffusion o ace-cen e ed C elemen s in o he body-cen e ed Ni oam and
he bonding be ween hem. Since he de eloped oam had a good amoun o C , i can be
used o co osion- esis ance and elec ical- esis ance applica ions.
Figu e 5. (a) Ch omized oam and i s (b) s u hickness and (c) p ocess capabili y.
3.3. EDS and XRD Analysis o Ni-C Alloy Foam
To e alua e he bonding and he phase o ma ions be ween he Ni and C elemen s,
EDS and XRD analyses we e pe o med on he oam. Figu e 6shows he line scanning and
EDS spec um o de eloped Ni-C alloy oam. I can be no ed om he esul s ha he Ni
and C elemen s we e uni o mly dis ibu ed h oughou he oam and he weigh % o Ni
was 71.56, C was 22.65 and oxygen was 2.17. This esul indica ed ha , hough he bonding
occu ed be ween he Ni and C elemen s, oxida ion o C also happened. This oxida ion
phenomena can be a ibu ed o an imp ope ine -gas low du ing ch omizing and can
be con olled by a ho ough cleaning o he u nace and sample, and by main aining he
a gon gas low a e a 2 ba . EDS analysis alone is no su icien o con i m he bonding
be ween he Ni and C elemen s; hence, o con i m he bonding and o es ima e he phase
o ma ions, XRD analysis was used. The esul s we e compa ed wi h e e ence pa e ns
in X’Pe HighSco e and con i med he o ma ion o Ni
2
C and Ni
2
C
4
O
7
compounds. In
addi ion, o suppo he esul s, he XRD spec um o he de eloped oam was compa ed
wi h a Ni-C (60:40%) solid sample. I can be obse ed om he esul s ha majo peaks
o bo h spec ums we e ma ching and, hence, i should be concluded ha he de eloped
oam has good bonding be ween Ni and C . I can also be no ed om he XRD esul s
ha he Ni-C oam had body-cen e ed cubic s uc u e. Thus, he esul s con i med he
comple e di usion o ace-cen e ed C elemen s in o he body-cen e ed Ni oam and he
bonding be ween hem. Since he de eloped oam had a good amoun o C , i can be used
o co osion- esis ance and elec ical- esis ance applica ions.
Coa ings 2023,13, 1002 8 o 12
Coa ings 2023, 13, x FOR PEER REVIEW 10 o 14
Figu e 6. (a) Line scanning o Ni-C oam along 2.5 mm leng h; a1-Ch omium, a2-Nickel, a3-Oxygen
(b) elemen al mapping; (c) XRD spec um o de eloped oam; (d) compa ison o oam wi h solid
sample.
3.4. Comp essi e S eng h o Ni-C Alloy Foam
To s udy he non-linea comp essi e beha io o he de eloped oam, a uniaxial com-
p ession es was ca ied ou using a UTM. The de o ma ion o he Ni-C oam can be
desc ibed using h ee s ages. The i s s age is called he linea elas ici y po ion, and in
his egion he de o ma ion beha io ollows Hooke’s law. The second s age is called he
collapse pla eau. He e, he plas ic de o ma ion and he ac u e o cell walls p og esses
simul aneously un il a dis inc peak ollowed by a small s ess d op occu s. I can be seen
om Figu e 7 ha he s ess gene a ed in he oam is inc eased up o some plas ic de o -
ma ion s ess and hen becomes cons an . This egion o cons an s ess is called he c ush
pla eau egion and i de ines he beha io o an ideal ene gy abso be .
The hi d s age o de o ma ion is called he densi ica ion o he oam. Once he ap-
plied s ess exceeds he c ush pla eau egion, he oam will s a o comp ess a a cons an
s ess up o 35%–50% o s ain. The densi ica ion egion o he cu e ac s as a sa e y
backup zone in ene gy-abso p ion applica ions and i allows unexpec ed ene gy o be ab-
so bed wi h an inc easing esis ance o he impac loads. I is obse ed om he esul s
ha he maximum comp essi e s eng h o he de eloped oam was 10.21 MPa a a maxi-
mum displacemen o 0.8. Table 2 compa es he comp essi e s eng h and po osi y% o
he de eloped oam wi h o he oams. I can be concluded ha he de eloped Ni-C oam
has be e comp essi e p ope ies and po osi y han he ea lie de eloped oams and hus
can ha e be e po en ial applica ions han he al e na i e ma e ials.
Figu e 6.
(
a
) Line scanning o Ni-C oam along 2.5 mm leng h; a1-Ch omium, a2-Nickel, a3-
Oxygen (
b
) elemen al mapping; (
c
) XRD spec um o de eloped oam; (
d
) compa ison o oam wi h
solid sample.
3.4. Comp essi e S eng h o Ni-C Alloy Foam
To s udy he non-linea comp essi e beha io o he de eloped oam, a uniaxial
comp ession es was ca ied ou using a UTM. The de o ma ion o he Ni-C oam can be
desc ibed using h ee s ages. The i s s age is called he linea elas ici y po ion, and in
his egion he de o ma ion beha io ollows Hooke’s law. The second s age is called he
collapse pla eau. He e, he plas ic de o ma ion and he ac u e o cell walls p og esses
simul aneously un il a dis inc peak ollowed by a small s ess d op occu s. I can be
seen om Figu e 7 ha he s ess gene a ed in he oam is inc eased up o some plas ic
de o ma ion s ess and hen becomes cons an . This egion o cons an s ess is called he
c ush pla eau egion and i de ines he beha io o an ideal ene gy abso be .
The hi d s age o de o ma ion is called he densi ica ion o he oam. Once he applied
s ess exceeds he c ush pla eau egion, he oam will s a o comp ess a a cons an s ess
up o 35%–50% o s ain. The densi ica ion egion o he cu e ac s as a sa e y backup zone
in ene gy-abso p ion applica ions and i allows unexpec ed ene gy o be abso bed wi h an
inc easing esis ance o he impac loads. I is obse ed om he esul s ha he maximum
comp essi e s eng h o he de eloped oam was 10.21 MPa a a maximum displacemen o
0.8. Table 2compa es he comp essi e s eng h and po osi y% o he de eloped oam wi h
o he oams. I can be concluded ha he de eloped Ni-C oam has be e comp essi e
p ope ies and po osi y han he ea lie de eloped oams and hus can ha e be e po en ial
applica ions han he al e na i e ma e ials.
Coa ings 2023,13, 1002 9 o 12
Coa ings 2023, 13, x FOR PEER REVIEW 11 o 14
Table 2. Compa ison o comp essi e s eng h and po osi y wi h ea lie s udies.
Type o Foam Max Comp essi exxxS eng h Po osi y% Re e ences
Ni-C alloy oam 10.21 MPa 91% Cu en s udy
Ni-C -Fe alloy oam 3.5 MPa 85% [15]
AZ91 Mg alloy oam 2.2 MPa 83% [17]
SS316L open-cell oam 3.0 MPa 80% [5]
Open-cell coppe oam 0.7 MPa 93% [2]
Figu e 7. S ess–s ain cu e o Ni-C oam subjec ed o uniaxial comp essi e loads.
3.5. Po osi y o Foam a Diffe en P ocessing S ages
In o de o examine he effec s o he coa ing echniques on he mic os uc u e o he
PU p ecu so , he po osi y% was calcula ed a diffe en p ocessing s ages o he Ni-C
alloy oam. The heo e ical po osi y o he de eloped oam was de e mined by Equa ion
(1) and he wa e displacemen me hod. I can be obse ed om Figu e 8 ha he po osi y%
o he oam is dec eased om he ELN s age o he UAEPN s age, and hen again o he
ch omizing s age. This change in po osi y% can be a ibu ed o an inc ease in s u hick-
ness om he ELN s age o he ch omizing s age. Du ing he sin e ing p ocess, he bond-
ing be ween pla ed Ni pa icles happens and hus a negligible dec ease in he po osi y %
can be obse ed.
Figu e 7. S ess–s ain cu e o Ni-C oam subjec ed o uniaxial comp essi e loads.
Table 2. Compa ison o comp essi e s eng h and po osi y wi h ea lie s udies.
Type o Foam Max Comp essi e
S eng h Po osi y% Re e ences
Ni-C alloy oam 10.21 MPa 91% Cu en s udy
Ni-C -Fe alloy oam 3.5 MPa 85% [15]
AZ91 Mg alloy oam 2.2 MPa 83% [17]
SS316L open-cell oam 3.0 MPa 80% [5]
Open-cell coppe oam 0.7 MPa 93% [2]
3.5. Po osi y o Foam a Di e en P ocessing S ages
In o de o examine he e ec s o he coa ing echniques on he mic os uc u e o he
PU p ecu so , he po osi y% was calcula ed a di e en p ocessing s ages o he Ni-C alloy
oam. The heo e ical po osi y o he de eloped oam was de e mined by Equa ion (1)
and he wa e displacemen me hod. I can be obse ed om Figu e 8 ha he po osi y%
o he oam is dec eased om he ELN s age o he UAEPN s age, and hen again o
he ch omizing s age. This change in po osi y% can be a ibu ed o an inc ease in s u
hickness om he ELN s age o he ch omizing s age. Du ing he sin e ing p ocess, he
bonding be ween pla ed Ni pa icles happens and hus a negligible dec ease in he po osi y
% can be obse ed.
3.6. Pe meabili y and P essu e D op o Ni-C Alloy Foam
In o de o es ima e he ease o u bonycoil low h ough he de eloped oam, pe -
meabili y was calcula ed a di e en p ocessing s ages o he oam. I can be no ed om
he esul s ha he pe meabili y dec eased om he p ecu so oam o he UAEPN oam,
and hen again o he ch omized oam. This dec ease can be a ibu ed o a dec ease in he
po osi y% wi h he inc ease in s u hickness. I is obse ed om Figu e 9 ha he oam
had good pe meabili y a all he s ages o p ocessing; hence, i can be concluded om he
s udy ha he de eloped oam can be used o il e ing applica ions.
