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Low Density and High Mechanical Strength Materials


Metal Matrix Composites with Lightweight Reinforcements

Tech Area / Field

  • MAT-COM/Composites/Materials

8 Project completed

Registration date

Completion date

Senior Project Manager
Tyurin I A

Leading Institute
Institute of General and Inorganic Chemistry (IONKh), Russia, Moscow

Supporting institutes

  • AO Kompozit, Russia, Moscow reg., Korolev\nVNIIKhT (Chemical Technology), Russia, Moscow


  • Los-Alamos National Laboratory, USA, NM, Los-Alamos

Project summary

During the last years lightweight materials with low density and high mechanical strength have found ever-growing use. These materials are essential for construction of different vehicles, especially in automotive and aerospace industries. Reduction in the weight of vehicles allows to lower the fuel consumption, increases the efficiency of transportation (economic effect) and reduces evolution of exhaust gases and pollutants (ecological effect). Therefore development of tenable lightweight materials is a task of great importance. In most cases metallic materials are unrivaled (their high-temperature strength, durability etc. are nonpareil). The most promising trend is development of composite materials with metal base, including metal matrix composites with lightweight reinforcing particles. Different combinations are used; the most popular materials are metal matrix composites (MMC) based on aluminum alloys with reinforcing silicon carbide particles.
The aim of the project is development of MMC with lighter additives, namely crystalline boron compounds including derivatives of cluster boron anions BnXn2- (n=10,12; X=H, halogen).
Uniqueness of the idea: The density of these compounds depends on their structure and composition (from 1 to 2 g/cm3), and their working temperature is as much as 700 оС. Reinforcing particles from such material considerably will allow reducing weight of the MMC; many kinds of material for reinforcements are insoluble in water. So, the developed materials are workable in a wide range of temperatures in a usual environment.

Researches in the given direction are completely original. There are no works in which it would be offered to use boron-hydrogen compounds as strengthening elements in MMC. We submitted application for patent. The list of a part of our works on boron-hydrogen compounds is shown in “References” (16 positions - publications on the given theme were basically in Russian, but magazines have the English variant of the edition).

Except of cluster boron anions BnXn2-, it is also planned to use other additives, including low-molecular boron compounds: derivatives of boron acids, tetrafluoroborates etc. Boron-containing particles could be also formed during formation of MMC (from low-molecular or high-molecular boron compounds in the liquid or solid form).

Materials for research:
The offered composite material has a metal matrix and reinforcing particles. Aluminum and copper will be applied to a matrix. Boron-hydrogen compounds will be applied for reinforcing particles, for example:
[Me2NH2]2 B10H10
[Bu4N] B10H10
Procedure of obtaining initial boric compounds includes four stages:
1. Synthesis of boron clusters using known procedures and low-molecular boric raw material (borates and tetrahydroborates) as a starting compounds.
2. Study of complexing processes and the synthesis of coordination compounds. These processes will be carried out both in the aqueous solutions and in the organic solvents. For isolation and purification of several compounds it may be necessary to use recrystallization from the solutions or the melt, and also adsorptive and ion exchange chromatography.
3. Study of substitution processes of exopolyhedral hydrogen atoms by functional groups and atoms of halogens. Synthesis of coordination compounds on the basis of similar derivatives and finalizing the procedures of their purification and isolation.
4. Study of physical chemistry properties (hardness, density, etc.), a choosing type of the light strengthened particles according to the studied properties. Accumulation of samples for creating materials.
Preparation methods of the initial boron compounds:
The main aims of the project are the synthesis, the analysis of the physical chemistry properties of the complex compounds of closo-borate anions. It is planned to synthesize a number of the complex compounds, where as the ligands are closoborate anions (BnHn)2- (n=6-12) and their substituted derivatives, and as the complexors are the cations of transitional and intransitive metals.
Work will include the series of successive stages. Initially it is planned to study the complexing reactions in the water and the organic solvents, which flows between the metal ions of groups B of periodic table, and by the unsubstituted closo-borate anions. It is possible that in several cases the compounds with the boron anions cluster in the external sphere will be formed. However, in our works it were already mentioned several cases, when the boron anions was as the ligands.
Besides of these studies, also it will be carried out the works, on a study of the coordination ability of substituted boron anions clusters. As the exopolyhedral deputies in such compounds will be acyl, carboxyl, nitro, nitroso groups and so on. It is also planned to examine the coordination properties of the cluster boron anions derivatives with “inert” substituents, such as halogen atoms or alkyl groups. In these cases two variants of behavior of closo-borate anions in the coordination compounds are possible. First, it is coordination to the central atom of metal due to “active” centers of subsistent – unshared electronic pairs of oxygen or nitrogen atoms. In the second, it is possible coordination with the formation of tricentric bonds boron-hydrogen-metal. One of the work aims should become the determination of relationship of similar types of binding depending on the type of subsistent and metal- complexor
Study influence of protonation processes on the process of complexing will be the third stage of works. It is well known the ability of boron cluster anions to join proton with the formation of anions [ BnH(n+1) ]-. We are already determined several mechanisms of complexing in the acid media. First of all we planned to isolate several compounds in which unconventional state of closo-borate anions are realized, including formation of quadrangular faces. For the silver (I) and Copper (I) compounds we have synthesized such kind of complexes and studied their structure by the X-ray structure analysis. During the project structure of all obtained complexes will be investigated, with the aim of explanation of closo-borate anions influence on composition and structure of coordination sphere of complexor. It is planned to systematize obtained experimental data with the purpose of understanding of closo-borate anions (BnHn)2-(n=6-12) coordination ability. One of the projects goals is studies of the physical chemistry properties of closo-borate anions complexes with the aim of creation on their basis practically useful materials.
Method and its implementation:
The composites will be synthesized by two basic means: 1) without formation of liquid phase and 2) with formation of liquid phase. Formation of composite by the first method will be based on mechanical alloying and subsequent compaction. It is planned to use different types of mechanical alloying equipment, namely vibrational setups and planetary mills. Mechanochemically prepared granules, consisting of metal matrix and reinforcing particles, will be then compacted by use of both traditional and dynamic procedures.
During elaborating methods of dynamic compacting, special attention will be draw to weakening the of the reflected wave action, because of reflected wave can lead to the appearance of microscopic cracks in the composite materials.
Synthetic procedures, which are based on liquid phase formation, should be investigated very thoroughly, because it is necessary to avoid chemical interaction between components leading to formation of embrittling phases.
Current status of technology:
Our group has wide work experience in the field of boron cluster anions chemistry. Earlier we investigated the reactions of complexing closo-borate anions (BnHn)2-(.n=6-12) with Ni(II), Co(II) and Pb(II) in the presence of neutral organic ligands. Structure of the obtained complexes was determined by X-ray diffraction analysis and IR spectroscopy. It was determined that in Ni(II) and Co(II) compounds the closo-decaborate anion play role of gegenion, and in case of Pb(II) – it goes into the metal internal coordination sphere. These results are one of examples of coordination compounds with closo-borate anion is in internal coordination sphere of metal. During the studies processes of complexing of silver (I) and copper (I) with the closo-borate anion (B10h10)2- it was determined that closo-borate anion can play role of innersphere ligand, forming of two types stable coordination compounds: Cat[MB10H10 ] and [M2B10H10 ], (M=Ag(I), Cu(I)). In these compounds, metal - boric bond appeared due to the formation of the tricentric bonds M-H-B. We studied the structures of complex compounds Cs[AgB10H10 ] and (C2H5)3NH[AgB10H10 ], there structure was detirmed by X-ray diffraction method, also possible mechanisms of complex formation was studied. One more work direction, which was conduct firstly in our group, was studying of the influence protonation of boron cluster anions to their complexing ability. From the system acetonitrile- trifluoracetic acids we isolated [(NCCH3)4Cu2B10H10] and {[(NCCH3)3Cu]AgB10H10} complex compounds. Their crystal structures were determined by X-ray diffraction method. In these complexes closoborate anion has unusual geometry - one and two quadrangular faces. Studying of complexing processes in the dynamic conditions, allow us to isolate different formation stages these compounds. On the basis of these data it is possible to point out several stages of the formation of coordination compounds with the uncommon geometry of the polyhedron: with the dissolution of the initial complexes Cu2B10H10 and Ag2B10H10 in the acetonitrile dissociation is occurs, acidation of the formed solution СF3COOH,, leads to the protonation of anion with formation (B10H11) -, and (B10H11) - anion gose to process of complexing. In the coordination compounds I and II deca-borate anion has uncommon geometry - one (I) and two (II) quadrangular faces. These deca-borate cluster geometry versions were calculated earlier and they were proposed as the model for protonated anion (B10H11) -. Probably easiness of forming the complexes with the uncommon geometry of closo-decaborate anion was caused by the fact that cations Cu+ and Ag+ can be considered as <isoelectric analogues> H+. From this point of view, obtained complexes can be considered as the possible models of the protonated anion (B10H11) – structure.
The project includes the following basic stages:
1) Preparation of materials and equipment
2) Development of synthetic methods allowing to obtain boron compounds with given mechanical strength and thermal stability.
3) Investigation of the properties of synthesized compounds, preparation of database including information on physico-chemical properties of boron compounds which could be used in metal matrix composites.
4) Development of procedures allowing obtaining composite materials without formation of liquid phases.
5) Development of procedures allowing obtaining composite materials through formation of liquid phases
6) Study of interaction between matrix and reinforcing particles.
7) Study of the structure and properties of developed materials.
8) Investigation of processing characteristics of developed materials, including mechanical strength, ability to welding and machining.
9)Manufacturing of specimens of developed materials
Expected results
1) Development of a number of aluminum-based composite materials with low density (1,8-2,3 g/cm3).
2) Development of a number of magnesium-based composite materials with low density.
3) Development of methods of low-density composite materials synthesis.
4) Development of methods of thermally stable (up to 700 оС) reinforcing particles synthesis.
5) Preparation of database including information on physico-chemical properties of synthesized metal matrix composites.
For fulfilling the project will be attract highly experienced specialists such as:
1)Zhizhin Konstantin Yurevich: PhD in Chemistry, senior researcher, author of more than 30 scientific publications. Scientific interests are chemistry and application of boron cluster anions. Several original methods of boron cluster anions derivatives synthesis were developed by Dr. Zhizhin.
2)Malinina Elena Anatol’evna: PhD in chemistry, senior researcher, author of more than 30 scientific publications. Scientific interests are chemistry and application of boron cluster anions. Several original methods of boron cluster anions coordination compounds synthesis were developed by Dr. Malinina.
3)Mustyaca Valeriy Nikolayevich: PhD in chemistry, researcher, author of more than 30 scientific publications. Scientific interests are chemistry and application of boron cluster anions. Several of boron cluster anions formation processes was studied by Dr. Mustyaca.
4)Ochertyanova Lubov Ivanovna: PhD in chemistry, senior researcher, author of more than 30 scientific publications. Maijor scientific interests are analytical chemistry and practical-scientific aspects of the atomic-absorption determination of elements in the inorganic materials.
5)Ketsko Valerie Alexandrovich, Doctor of chemical sciences, leading researcher, author more than 80 scientific publications. Major scientific interests are physical chemistry and application of composite materials.
Joint stock company "Composite” staff are the highly experienced specialists in the area of composite materials development and in the field of composite materials compacting.
VNIIKHT staff are the highly experienced specialists in the field of the chemical compounds synthesis and selection of components for the composite materials.
All this facts shows that project can be successfully fulfill in the case it will be supported financially.


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