Self-propagating high-temperature synthesis: textbook

164 Pages·2018·5.391 MB·English

by  Рогачев А.С.

AL-FARABI KAZAKH NATIONAL UNIVERSITY and
INSTITUTE OF COMBUSTION PROBLEMS
Z. A. Mansurov
A. S. Mukasyan
A. S. Rogachev
SELF-PROPAGATING
HIGH-TEMPERATURE SYNTHESIS
Textbook
Almaty
«Qazaq University»
2018
UDC 544.1 (075.8)
LBC 21.1 я 73
M 24
The Academic Council of Department Chemistry and Chemical Technology
and RISO of al-Farabi Kazakh National University
was recommended for publication
(Protocol №7 dated 05.07.2018)
Reviewer
Doctor of Chemical Sciences, Associate Professor N.N. Mofa
We express great gratitude to Dr. S.M. Fomenko for discussion and thanks to Ph.D-student
Makpal Seitzhanova for her assistance in preparation of this textbook for publication.
Mansurov Z.A., Mukasyan A.S., Rogachev A.S.
M 24 Self-propagating high-temperature synthesis: textbook / Z.A. Mansurov,
A.S. Mukasyan, A.S. Rogachev. – Almaty: Qazaq University, 2018. – 164 p.
ISBN 978-601-04-3469-1
The textbook is devoted to the problems of self-propagating high-temperature synthesis.
This textbook can be useful to a wide range of professionals involved in nanotechnology as
well as bachelors, masters and Ph.D students and doctors.
Published in authorial release.
UDC 544.1 (075.8)
LBC 21.1 я 73
ISBN 978-601-04-3469-1 © Mansurov Z.A., Mukasyan A.S., Rogachev A.S., 2018
© Al-Farabi KazNU, 2018
2
C
ONTENTS

PREFACE ............................................................................................................................... 5

Chapter 1. SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS ................... 7
1.1. General definitions ...................................................................................... 7
1.2. Fundamentals of SHS .................................................................................. 8
1.3. Structural macrokinetics of SHS processes ................................................. 10
Control questions ................................................................................................... 11
References ............................................................................................................. 11

Chapter 2.DIFFERENT PROCESSES OF SELF-PROPAGATING
HIGH-TEMPERATURE SYNTHESIS ............................................................. 12
2.1. Gasless combustion synthesis ...................................................................... 12
2.2. Combustion synthesis in gas–solid systems (infiltration combustion) ......... 15
2.3. Combustion synthesis with a reduction stage .............................................. 20
2.4. Solution combustion synthesis .................................................................... 22
2.5. Mechanical activation of initial powder mixtures for SHS .......................... 23
2.6. Example of SHS with preliminary mechanical treatment of the powders ... 25
Control questions ................................................................................................... 26
References ............................................................................................................. 26

Chapter 3. THERMODYNAMICS AND DRIVING FORCE OF SHS PROCESSES ..... 30
3.1. General principles ........................................................................................ 30
3.2. Equilibrium, reversibility, stationary and stability of the
SHS processes and products ........................................................................ 36
3.3. The thermodynamics of the reaction cell ..................................................... 38
Control questions ................................................................................................... 41
References ............................................................................................................. 41

Chapter 4. KINETICS OF HETEROGENEOUS REACTIONS ........................................ 42
4.1. Solid-state reactions ..................................................................................... 44
4.2. Solid–gas reactions ...................................................................................... 49
4.3. Reactions with the liquid phase ................................................................... 57
4.4. Reactions with gasification of the initial solid phase reagent ...................... 58
4.5. Methods of high-temperature kinetics of heterogeneous reactions .............. 60
Control questions ................................................................................................... 64
References ............................................................................................................. 65

Chapter 5. STRUCTURE FORMATION IN HYBRID SOLID–GAS SYSTEMS ............ 68
5.1. Model of structure formation during combustion of metals with
nitrogen ........................................................................................................ 70
5.2. Models of structure formation during combustion of non-metals
in nitrogen ................................................................................................... 73
Control questions ................................................................................................... 77
References ............................................................................................................. 77

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Chapter 6. SHS OF TiB2-Al2O3 and CrB2-Al2O3 CERAMICS ........................................... 78
6.1. Self-propagating high-temperature synthesis of boron containing
ceramic materials: the state of art ................................................................ 78
6.2. Experimental ............................................................................................... 81
6.3. Results and discussions ............................................................................... 84
6.3.1. Layer-by-layer X-ray structural analysis of hardened samples.
SHS-process was stopped by “Hardening” method followed by analysis
of partially and completely burnt part of the charge
in 0.75TiO2-0.25Ti-2B-Al system ............................................................... 84
6.3.2. SHS parameters ........................................................................................... 85
6.3.3. Analysis of the composition and morphology of the combustion
products ....................................................................................................... 87
6.4. Conclusions ................................................................................................. 91
Control questions ................................................................................................... 91
References ............................................................................................................. 92
Chapter 7. SOLUTION COMBUSTION SYNTHESIS ....................................................... 94
7.1. Synthesis gas production on glass cloth catalysts modified by Ni
and Co oxides .............................................................................................. 94
7.2. Synthesis of catalysts ................................................................................... 95
7.2.1. Study of the catalytic activity ...................................................................... 96
7.2.2. Physicochemical examination of samples ................................................... 96
7.3. Characteristics and properties of the catalysts ............................................. 97
7.4. The catalytic activity of samples in the reaction of dry reforming
of methane ................................................................................................... 101
Control questions ................................................................................................... 104
References ............................................................................................................. 104
Chapter 8. COMBUSTION SYNTHESIS OF SILICON AND SILICON
CARBIDE NANOPOWDERS ............................................................................ 106
8.1. Combustion synthesis of silicon nanopowders ............................................ 106
8.2. Investigation of the silicon nanopowders .................................................... 108
8.3. Combustion synthesis of silicon carbide ...................................................... 113
Control questions ................................................................................................... 117
References ............................................................................................................. 118
Chapter 9. SHS REFRACTORY MATERIALS “FURNON” AND THEIR
PRACTICAL IMPLEMENTATIONS IN KAZAKHSTAN AND RUSSIA ... 119
9.1. SHS-refractories: “Furnon” ......................................................................... 119
9.2. New carbon-containing refractories ............................................................. 123
Control questions ................................................................................................... 132
References ............................................................................................................. 132
Laboratory work 1. Measuring of the combustion wave velocity ............................................ 134
Laboratory work 2. Measuring of the maximum combustion temperature .............................. 140
Laboratory work 3. Combustion wave profile ......................................................................... 151
Laboratory work 4. SHS of nitrogen containing materials by using chromium
oxide based concentrate ............................................................................................................ 157
Laboratory work 5. Synthesis of the boron-based composites by using SHS method .............. 160
Laboratory work 6. SHS synthesis of superconductors: magnesium diboride ........................ 162
4
P
REFACE

Self-Propagating High-Temperature Synthesis,сombustion synthesis is an attract-
tive technique to synthesize a wide variety of advanced materials including powders
and near-net shape products of ceramics, intermetallics, composites, and functionally
graded materials. SHS-produced materials have found their application in different
branches of modern science and technology, including mechanical engineering,
aerospace engineering, electrical engineering, chemical industry, ferrous and
nonferrous metallurgy and electronics.
Self-propagating high-temperature synthesis is a subject of discussion on different
international symposiums and meetings on combustion, as well as materials science
forums, where different aspects in the field of SHS are regularly presented and
discussed.
It is worth noting that a major contribution to the investigation of SHS processes
was made by A.G. Merzhanov and members of his scientific school, such as
V.M. Shkiro, I.P. Borovinskaya, and Yu.M. Maksimov, as well as by the world
recognized leaders in the SHS field, including Z. Munir, K.C. Patil, A. Varma,
T.P. Weihs and other researchers. Theory of this process is based on the classical
fundamental works of N.N. Semenov, Y.B. Zeldovich and B.I. Khaikin.
This textbook is written on the base of special course delivered to PhD-students of
Department of Chemical Physics and Materials. In the first chapter, we consider the
fundamentals of self-propagating high-temperature synthesis and structural
macrokinetics of SHS processes. Chapter 2 is devoted to the different routes of self-
propagating high-temperature synthesis, including gasless combustion synthesis,
combustion synthesis in gas-solid systems and with reduction stage, solution
combustion synthesis, mechanical activation of initial powder mixtures for SHS and
the effects of mechanical treatment of the reaction mixtures on SHS. In the third
chapter, we describe the thermodynamics and driving force of SHS processes, their
general principles, equilibrium, reversibility, stationary and stability of the SHS
processes and products, the thermodynamics of the reaction cell. Chapter 4 is dedicate
to the kinetics of heterogeneous reactions, including solid-state and solid–gas
reactions, reactions with the liquid phase, reactions with gasification of the initial solid
phase reagent. The fifth chapter describes the structure formation in hybrid solid–gas
systems, focusing on general models of structure formation during combustion of
metals and non-metals in nitrogen.
Chapter 6, describes the specifics of self-propagating high temperature synthesis
and structure formation of boron containing, ceramics. The seventh chapter considers
the solution combustion synthesis of catalysts. It is demonstrated that fine catalysts
fabricated by SHS method can be effectively used for the solution of ecological
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problems in processes of CO and hydrocarbon combustion, as well as for the
utilization of the components, which lead to the, so-called, “greenhouse effect”.
Chapter eighth is dedicated to combustion synthesis of silicon nanopowders. In the
ninth chapter we overview the SHS refractory materials from “Furnon” family and
their practical implementations in Kazakhstan and Russia.
At the end of this textbook, we also provide the laboratory works that are related
to the different aspects of SHS process.
Finally, for those who seek for the deeper understanding of the theory and mecha-
nisms of SHS-processes, as well as other combustion-based technologies, we highly
recommend reading additional literature cited in this book (cf. Chapter 1, Ref. 1-10).
6
C 1
HAPTER
SELF-PROPAGATING HIGH-TEMPERATURE
SYNTHESIS
1.1. General Definitions
Self-propagating high-temperature synthesis (SHS) is a science-intensive process
for fabrication of materials. It was established in the second half of XX century by
group of Russian scientists leaded by A.G. Merzhanov [1]. The history of this
discovery and development of its technological applications have been described in
many books and reviews [2-6]. Comprehension of SHS requires fundamental
knowledge in thermodynamics, chemical kinetics, general and structural
macrokinetics, materials science, and other related fields.
SHS involves processes in which the reactive mixture of the initial reagents
(usually powders), when ignited, spontaneously transformed into the valuable solid
products due to the exothermic self-sustained reactions. Several other terms – such as
combustion synthesis, gasless combustion, self-propagating exothermic reaction – are
used to describe the process.
A well-known example of SHS reaction is the thermite reaction given below:
Fe O + Al → 2Fe + Al O
2 3 2 3
This reaction generates temperatures above the melting point of alumina and is
used in the welding process for joining railway lines.
Considering the SHS as a variety of heterogeneous combustion, three stages of
the process can be outlined:
1) mixing the components typically at room temperature, when the chemical
reaction does not yet take place;
2) the initiation of an exothermic chemical reaction (ignition or self-ignition);
3) a self-sustaining chemical reaction which occurs without external heat sources
and leads to the formation of combustion products (chemical compounds, powders,
materials or net shape articles important from the practical applications) [4, 7-9].
The initiation of a chemical reaction is usually carried out by heating the reaction
mixture and there are two entirely opposed methods of heating. The first way is to heat
the whole sample slowly so that temperature has time to equalize over the entirety of
its volume. In this case the reaction should develop simultaneously and uniformly at
all points of the sample and at a specific temperature one should observe a sharp self-
7
acceleration of the process – the whole sample evenly ‘self-ignites’. This SHS mode is
called volume combustion or thermal explosion, it is illustrated in Fig. 1.1. SHS in the
thermal explosion mode has much in common with reaction sintering in powder tech-
nology, but there is a fundamental difference. It consists in the fact that in reaction
sintering it is necessary to avoid spontaneous heating of the sample by chemical reac-
tion, whereas in SHS this warm-up is utilized. The theory of thermal explosion was
developed in the works of the outstanding Russian scientist and Nobel Prize winner
N.N. Semenov and his followers.
Fig. 1.1. Self-propagating high-temperature synthesis modes: volume combustion.
The second way of ignition is optimal rapid heating of only a small volume of the
sample (e.g. ~1 mm3) that results in local reaction initiation of an exothermic reaction,
which then self-propagates to the rest of the sample in the form of a combustion wave.
This SHS mode is called the wave or auto-wave combustion mode. Fig. 1.2 shows
schematically such a process. Fast heating is needed to ensure that the heat from the
local area of ignition has no time to spread to nearby areas and create an uneven
temperature distribution in the sample. The point is that the route of the reaction and
thus the properties of the combustion products depend on the initial temperature of the
medium. Consequently, if the initial temperature is not uniform, the products of
combustion synthesis are varied in the volume of the sample. Typically, the non-
uniformity of the product is undesirable, except in special cases where the purpose of
synthesis is to provide materials with a gradient structure and properties.
Fig. 1.2. Self-propagating high-temperature synthesis modes: auto-wave combustion.
1.2. Fundamentals of SHS
Theory has played an important role in combustion science. Early examples,
include Chapman-Jouguet detonation theory; the Burke-Schumann fast-chemistry
approxi-mation for diffusion flames (derivable in a limit process that called
8
Damkohler-number asymptotic); Frank-Kamenetskii's steady-state theory of
spontaneous combustion (the origin of activation-energy asymptotic); Zeldovich's
early contributions to deflagration theory (equivalent to use of activation-energy
asymptotic for achieving spatial scale separation); and the Darrieus-Landau
hydrodynamic limit for deflagrations (which could be termed Peclet-number
asymptotic).
It is no an accident that most of these theoriespresent anasymptotic approxima-
tions. Indeed, the combustion problems, like those of fluid mechanics, can seldom be
linearized, and so analytical strategies require mathematical tools capable of dealing"
with nonlinearities. Asymptotic is the only universal tool, requiring only a large para-
meter Asymptotic, whether matched asymptotic expansions (such as boundary-layer
theory), Poincare-Lighthill strategies (as in perturbed orbital mechanics and sonic-
boom theory) or multiple-scale techniques (justifying Krylov-Bogoliubov averaging,
WKB approximations, and adiabatic invariances), essentially emerged strongly after
World War II (although with roots extending back to Laplace and Newton) and was
vigorously developed by the fluid-mechanics community.
It is difficult to pick up copies of the Journal of Fluid Mechanics from the 1950s,
1960s, and 1970s, and understand the theoretical work discussed there without at least a
rough grasp of asymptotic. In combustion, the development of asymptotic was slower and
for many years was restricted to the Russian school associated with names of Semenov,
Zeldovich, and Frank-Kamenetskii. The achievements of this school are summarized by
Zeldovich, Barenblatt, Librovich, and Makhviladze in a book [10], which in many ways is
a compendium of that work. These contributions are characterized by rich physical
discussion, and they challenge anyone who might feel that physical understanding and
intuition are necessarily in conflict with formal mathematical strategies.
It is a fact that simple mathematical models that incorporate a minimum of
physics, when solved in a manner that makes transparent the physical interactions in
various parts of the combustion field, and when the results are presented in a physical
context, can be a source of physical insight superior to any other. It is difficult, for
example, to see the specific role of radiation in the stabilization of flame balls [11]
without an examination of the mathematical stability theory. In fact, a little thought
along the lines of radiant-loss influences on flame speeds, without carefully
considering Lewis-number effects, can easily lead to an apparently plausible, but
incomplete and possibly misleading picture. However, the Russian school may have
had one flaw, i.e.an apparent unwillingness, once the mathematical model was posed,
to push analysis to the limits. Some hint of why this had happened can be found on
page 369 of [10], which suggests that additional details may have little physical
validity. But, in fact, there is no reason to believe that the omitted physics necessarily
would undo the subtle details predicted by the physics that is retained. Thus, a
legitimate strategy is to push the mathematics to the limit, but be prepared to adjust the
model should the solutions be at variance with the experimental record or fully
detailed numerical solutions.
Flame balls provide one example of rich behavior generated by a simple model
consistent with the experimental record: there is a lean flammability limit [11]; one-
dimensional stability only if heat losses by radiation, convection or conduction are
present [12,13]; the disappearance of an interval of stable solutions as the Lewis
number of the deficient reactant is increased from small values to unity [14]; three-
dimensional instabilities at mixture strengths well removed from the lean limit [15];
9
repulsion of one flame ball by another to generate drift [16]; and stabilization by
fluctuating velocity gradients of appropriate amplitudes and frequencies [17].
The theoretical papers in the Journal of Fluid Mechanics today look quite
different from those of fifty years ago. These days, the applied mathematician
wrestling with mechanics problems is far more likely to use scientific computation
strategies than asymptotic. The same trend is now apparent in combustion (albeit this
review contains counterexamples), naturally so since asymptotic has its limitations. In
combustion, most asymptotic treatments are either one-dimensional or small
perturbations thereof; exceptions include descriptions of the dynamics of combustion
fronts for flames (such as the Michelson-Sivashinsky equation or the Kuramoto-
Sivashinsky equation) or more recently for detonations, in which multidimensional
combustion problems are reduced to a partial differential equation or an integral
differential equation for a single scalar, an equation that must be solved numerically,
for the most part, but a numerical task that is much simpler than the unreduced
problem.
It must be emphasized that the trend towards computation is not simply an aban-
donment of analytical strategies for computational approaches of a kind long pursued
in the past. Typically, the models are still incomplete, the algorithmic investment is
comparatively small, and there is an applied-mathematician's sensibility (for good and
bad) that permeates the endeavor. Recent monographs and review articles [18,19]
summarize many of the main achievements in combustion theory over the past fifty
years. This literature documents attainment of rather a high level of conceptual
coherence. Combustion theory is, in fact, perhaps one of the most elegant areas of
classical phenomenology, presenting a graphic example of the wide range of natural
phenomena that can be deduced from a few fundamental principles [20].
1.3. Structural macrokinetics of SHS processes
In recent years strict requirements demanded by modern materials led to intensive
studies of structures and mechanism of structure formation of the SHS products. This
is not accidental since the structure of a materialto a great extent determines its
properties, especially. It would not be overestimation to state that problem of
controlling product structure is one of the most important tasks in further development
of SHS. Here the structure means a wide range of characteristics including
macrostructure (composition distribution, macroscopic defects), microstructure
(arrangement of phases and crystals with respect to each other, grain size, porosity and
pore structure, localization of impurities), and crystal structure (crystal lattice type and
lattice parameters, presence of defects, ordering with formation of super lattices,
amount and distribution of dislocations). The structure of combustion wave itself
needs to be added to the above classification since distribution of temperature and
concentration in the combustion and after-burning zones markedly affects the
composition and structure of the synthesized materials. It is well recognized that
structural macrokinetics (SMK) studies evolution of structure in the course of
chemical transformation taking into account heat and mass transfer processes [7,8]. A
place of SMK in the number of other fields of science can be presented by the
following equations:
10