Journal of Materials Science and Chemical Engineering, 2014, 2, 66-69
Published Online January 2014 (
Research of Nanostructures Formation
during Self-Propagating High-Temperature
Synthesis of Boride-Containing
Composite Materials
D. S. Raimkhanova, R. G. Abdulkarimova, Z. A. Mansurov
Institute of Combustion Problems, Almaty, Kazakhstan
Received October 2013
This pa per considers the techni que of obtaining bor ide-cont aini ng na nostr uctur ed composite materials by t he
method of self-propagating high-temperature synth e sis ( SHS) . It is sho w n tha t the selection of regi mes and con-
ditions of reactions allo ws receiving materials on t he basis of tita niu m and chromium borides as we ll as alumi-
num oxi de w ith finely disper se d structure and high mechanical properties.
Aluminum Oxid e; Titaniu m Diboride ; Chromium Dibo ride; Composite M at erials;
Nanomaterials; SHS
1. Introduction
Obta i ni ng cera mic and composite materials co nta i ning
nano -sized phase and struc tur a l co mpo nents is curr e nt l y
one of the mos t important problems. One of the trends
for solving such problems is a combination of several
technological tech niq ue s allo win g modifying the material
struc t ur e dir ectionall y at the sta ge of preparation and
carrying out of subse q uent synthesi s [1,2]. Among vari-
ous methods of synt he si s on t he b asis of reactions, the
synt he si s in the mode of self -propagating high-tempe ra-
ture synt he s i s ( SHS) is pa rtic ularl y attracti ve because of
its adva nta ge s : lo w energy consumption, short process
time, si mplicit y of equipme nt and t he formation of prod-
ucts with high pur i t y, etc. [1-3].
Diborides of transition metals such as TiB2 and CrB 2
have many excellent properties suc h as high meltin g
point, high densi ty, good thermal and electrical conduc -
tivity, excellent wear and corrosion resistance a nd c he-
mical stability [1-3]. Furthermor e, adding Al2O3 to the
borides of these metals improves their breaking stren gt h,
flexur a l str e ng t h, i mpact strength and thi s ma kes boride
composites very promising for a wide ran ge of applica-
tions, includ i n g cutting tools, wear-proof parts and high
temperature structura l materials [2,3].
2. Methodology of Exp eriment
2.1. Self-Propagating High-Temperature
The purpose of this research is to study the SH-s ynt he sis
of composites based on TiB 2-Al 2O3 and CrB 2-Al 2O3 wi th
a wide range of phase composition in the process of SHS
in the systems of Ti-TiO2-B -B2O3-Al, Cr2O3-Al-B2O3,
TiO2-H3BO3-Mg-nNa Cl.
The initial components of the SHS-cha rge were T iO2,
Cr2O3, B2O3 oxides, amor p hous boron and aluminum of
PA-4 gr ad e (purity of 99.1%, particles <40 microns). The
char ge of a specified composition wa s inte r mixed t ho r-
oughly up to achi evin g a high degre e of homo ge nei t y.
Cylindrical samples wi th a diameter of 20 mm and a
height of 25 mm were pressed on an auto matic pr ess
(Carver, Inc., USA) with the effort of 4 t. Exp er iment s
wer e performed in the a ir atmosphere; the initiating of
SH-synt he si s wa s perfor med by thermite or ma g nes ium.
Compositio ns contai ni n g TiO2, H3BO3, Mg, and vari-
ous amounts of NaCl (5, 10, 15wt.%) were prepared for
cond uc ting SH -s yn t he sis in the system of TiO2-H3BO3-
Mg-nNaC l. Educing of titanium diboride fro m combus-
tion products was conducted by treating the latter with
water and hydrochloric acid.
The micro struc t ur e of synthe siz e d products was stud-
ied by scanning electron microscope—micro -analyzer
JCXA-733 (JEOL)Superprobeand SEM Hitachi
S-4800 FE-SEM, Japan, the p ha se co mpositio n of SHS
products by the X-ray diffractometer DRON-3.
2.2. Combustion Front Quenching Met hod
To study the st ruct ura l tr a nsitions in the co mbu stion of
Ti-TiO2-B-B2O3-Al the meth od of combustion fro nt
quenchin g me t hod (CFQ M ) s ystem wa s used [4]. The
reaction mixture was placed in a wedge-shaped notc h in
a copper block, and the comb ustion reaction was initiated
by an incandescent tungsten spir al at the base of the
wedge. When the co mbustion wave traveled to ward the
apex, because of the inte ns e t ransfer of heat to the cool-
ing copper block, the combustion was quenc he d , so the
intermediate a nd final products of the reaction were fr o-
zen. The st r ucture s of the specimen in the regions wher e
the fr o nt is quenche d we re ob served with scanning elec-
tron microscopy (SEM).
3. Resul ts of Resea rch and T heir Discussion
Shutt i ng down of SHS-process with t he sub se quen t
anal ysi s of partiall y a nd f ul l y b ur ne d par ts of the c ha rge
in the syst em of Ti-TiO2-B-B 2O3-Al wa s performed. At
the enlarged fra gme n t of the reaction zo ne of CFQM
SHS wave sh own in the Fig ur e 1(a) and (b), the forma-
tion of gra nu la r inclusions crystallized in t he six-mem-
bered lamellar formations of titanium diboride in a ma-
trix of aluminum oxide shown in the fi na l product.
It was found that aluminum facilitates the formatio n of
sub mic r on par ticles. It can ser ve as the co ncentrator of
crystal whis k er g rowth carried o ut by the mecha nism of
For the s yst e m of Cr2O3-B2O3-Al t he for mation of mi -
crostructure of the solid-phas e combustion products was
also investigat ed . It can be assumed that they represent
areas of a metastable solid sol ution of c hr omium diboride
in aluminum oxide matrix. Studying the micr o st r uc ture
of compositions with hi g he r magnification revealed the
formation of whisker s from aluminum oxide in the ma-
trix of chro mi um diboride [6] (Figure 2).
Figure 2 shows that whisker s are of differe n t sizes and
shapes. Fiber s are of straight, curled and wav y for ms
(Figures 2(b)-(e)). The Figure 2(e) shows whiske rs hav -
ing branc he d struc t ur e . The results obtained show that
the formation of α-Al2O3 fibers with a length of about
(a) (b )
Figure 1. Analysis and microstructure of the combustion system products TiO2-B2O3-Al, obta i ned by the CFQM of the SHS
w ave; (a) reaction zone with the for mation of g rai n s of TiB2; (b) f or mation of Al2O3 f i bers in the pores of r eac tion z one.
Zone No.Atomic ratio, %
BO Al Ti
157.32 39.69 2.99
27.7652.99 37.931.32
344.13 24.23 20.69 10.95
449.98 13.437.4429.14
Zone No.Atomic ratio, %
BO Al Ti
157.32 39.69 2.99
27.7652.99 37.931.32
344.13 24.23 20.69 10.95
449.98 13.437.4429.14
Atomic ratio, %
BO Al Ti
142.87 56.450.67
219.01 29.45 50.001.54
313.42 40.40 42.603.58
Atomic ratio, %
BO Al Ti
142.87 56.450.67
219.01 29.45 50.001.54
313.42 40.40 42.603.58
(a) (b)
(c) (d)
(e) (f)
Figure 2. Microstructure of products of Cr2O3-B2O3-Al; (а) General picture of final products surface; (b) whiskers (feathers)
of aluminum oxide; (c), (d), (e) straight, wavy and twisted forms of whiskers, e-branching of multiple crystals.
l = 10 - 25 micron e a nd a diameter d = 200 - 500 nm.
Vari o us va l ue s of the fi b e r s d iameter follo wed fr om sys-
tem growth self -t ur b ulence , namely, t he growth of tem-
perature, diffusion and chemical reaction, une ve n ness of
the boundary between the liqu id and solid phase s. [3]
Thus, as a result of studies of Ti-TiO2-B-B2O3-Al,
Cr2O3 + Al + B2O3 s ystems, in SHS-products of studie d
syst ems was estab lished the p resence of high temperature
phases—titanium diboride, chr omium diboride and alu-
minu m oxid e c hr omi um (XRD). It was established t ha t
the for mation of submic r o n al uminum oxide whiskers in
the combustion process and tha t t hey str e ng t he n t he re-
sulting composite and improve its fire resistance up to
The product of combustion and further acid ic trea t-
ment of the T iO2-H3BO3-Mg-nNaCl system represented
phases of titanium diboride as well as p hases of T iO2 a nd
titanium nitrid e T iN (Ta ble 1).
The Fig ure 3 shows the r oent ge no gr am of the ob-
tained product after treatment with hydrochloric acid.
We studied the microstructure of the final products
depending on the amou nt of NaCl dil uent in the char ge .
Figure 4 shows microstr uctures of the tita nium diboride
powder TiO2-H3BO3-Mg-nNaCl (5, 10, 15 wt.%) system
obtained in the SHS r eg ime and its sub s eq uent treat ment
with a solution of hydrochloric acid HCl.
Table 1. XRF produc t s after leaching.
Conent, %
TiB2—88.6 TiO2—5.9 SiO2—3.7 TiN—1.8
Figure 3. Roentgenogram of SHS produ c t s .
Figure 4. Sc anning electron micrograph of t he pr o duct after
acidic treatment of TiO2-H3BO3-Mg-nNaCl system (n = 15
Thus, as a result of SHS with furt he r acid ic treatment
with the u se of NaCl acid with the purpose of dissolving
MgO a nd o t her i mpuritie s, it was o btained a tita nium
diboride powder, which represented agglomerates con-
sistin g of spherical particles wit h a size of 200 - 1000
4. Conclusion
The directed r egulation of high te mperature solid-p hase
synt he si s pro cess allows for mi ng co mposite ceramic ma-
terials based on diborides of transitio n metals wi th finely
dispe rse d str uc t ur e and high mechanical properties. This
approach is used to create new, s imple a nd cost-e ffective
processes of creating high str engt h cera mics.
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