Combustion Synthesis and Characterization of W-Cu Composite Nanomaterials
Project Status: 8 Project completed
Commencement Date: 01.01.2015
Duration in months: 24 months
Objective
The present project is aimed to develop a new approaches and technology for the manufacturing of W-Cu composite nanomaterials: powders, sintered alloys and compacts, to characterize their mechanical and electrophysical properties.
The tungsten-copper heavy alloys consist of W particles embedded in matrix of copper and have potential uses in metallurgy, electronics, microelectronics, spaceflight, aviation. The W-Cu alloys combine the properties of both metals, resulting in a material that is heat-resistant, ablation-resistant, low thermal expansion, highly thermally and electronically conductive and easy to machine. The typical mechanical and physical properties of the alloy depend on its composition. Based on W-Cu composite materials of different composition thermal mounting plates, chip carriers, flanges, frames for high-powered electronic devices, die inserts and electrode facings would designed and developed.
Conventionally W-Cu composites are prepared from elementary powders by mechanical alloying at 1000-1300oC under the 100MPa pressure and duration up to some hrs. To improve the physicomechanical properties of phases in the immiscible W-Cu binary system, a number of preparation methods were suggested, including hot-shock consolidation, thermo-mechanical alloying, microwave sintering of elementary powders, copper and tungsten oxides joint reduction by hydrogen at 600-800oC with further mechanical alloying.
Taking into account the disadvantages of above described methods (multistage preparation process, energy and time consumption, low efficiency and low productivity), it is suggested to develop new simple and effective approaches based on energy-saving combustion processes. It is supposed, that the proposed approaches will allow to realize the preparation of W-Cu nanomaterials with new physicomechanical characteristics in a short and inexpensive way. Note that the synthesis of W-Cu nanopowders and sintered alloys by combustion reaction is of great scientific interest too and has never been studied.
The main objectives of the proposed Project are as follows:
- in situ combustion synthesis (CS) of W-Cu nanocomposites of various compositions directly from the oxide or salt precursors and their subsequent compaction.
- to study the formation mechanism of W-Cu nanopowders and sintered alloys from various raw materials and finding the optimal conditions of their synthesis.
- to study the compaction behavior of W-Cu nanopowders and sintered alloys, determination of optimal parameters of their explosive compaction.
- to study the structure and properties of the W-Cu nanopowders, sintered alloys and compact samples obtained by CS method and subsequent compaction.
Compared to other synthesis techniques the specific features of the CS are evident: CS is the fastest, extremely energy efficient, environmentally safe, waste-free and scientifically attractive. As regards for preparation of composite powders and alloys, CS is perspective for in situ synthesis of homogeneous materials with partially or fully ingrowth constituents.
In order to perform joint reduction of copper and tungsten oxides (salts) in controlled combustion mode, it is proposed to use coupling of low exothermic reduction reactions (e.g. MeO+C(CH polymer)) with a high-energetic reaction (CH polymer + NH4NO3), or using Mg+C (or Mg+CH polymer) combined reducers as important levers to control combustion temperature, morphology and microstructure of the final product.
Alongside with CS, we propose to use mechanical activation of oxide mixture obtained from corresponding salts and then reduce the metals in combustion mode for obtaining nanocrystalline blends of Cu & W powders. The latter will undergo to high-pressure consolidation by high temperature explosive compaction in cylindrical billets in two stages:
- preliminary explosive compression of the nanocrystalline W-Cu precursor powder blend is carried out at room temperature with a loading intensity of 5-10 GPa to increase the initial density and to activate the particle surfaces in the blend;
- the same, already predensified cylindrical rods are reloaded by primary explosive shock wave with a loading intensity of 10 GPa, but at a temperature up to-1000 °C (HEC).
Preliminary investigation of nanostructural W-Cu composition with content of nanocrystalline W phase up to 40% and consolidated to near theoretical density at 800 and 1000 °C showed that application nanoscale W phase in W-Cu composition in contrast to conventional micron size compositions has big advantages and allows to obtain billets with improved electronic properties.
The investigation performed in the framework of this project will allow to solve the following problems:
- to develop the innovative way to produce W-Cu nanocomposites by an energy-saving and efficient technology from available raw materials (oxides, salts);
- to realize the alloy preparation with high efficiency and obtain nanocomposites in a short and inexpensive way;
- to overcome high sintering temperatures and to fabricate billets by hot explosive consolidation technology near theoretical density in wide range of containing consisting phases having high value of strength and improved electronic properties. From the commercial standpoint it must be mentioned that cylindrical billets of W-Cu composites with dimensions up to D=30mm and L=300mm will be fabricated.
It is assumed that obtained materials will differ from the materials obtained by conventional methods caused by the advantages of manufacturing method and low cost ensuring their wider application.
The scientific staff of the Institute of Chemical Physics of NAS RA has significant experience in the synthesis of a large number of advanced materials, including metallic nanopowders, composites, and alloys. Tsulukidze Mining Institute and Andronikashvili Institute of Physics of TSU have extensive experience in explosive consolidation of materials, as well as study their physicomechanical characteristics. There is every reason to believe that the combination of experience and efforts of the involved teams will allow to successfully solve assigned tasks of this project in time.
As a result of the project a number of problems will be solved, including those that are related to the purposes and objectives of the ISTC, i.e.
• To direct the accumulated knowledge (in the creation and development of weapons technology) of scientists and engineers both of IChPh NAS RA and two Georgian institutes for the solution of peaceful objectives, namely, to realize fundamental and applied research in the development of new synthesis methods of composite nanomaterials and alloys.
• to establish the scientific links with potential collaborators and other specialists in the field of nanocomposites from ISTC founders’ countries for further long-term collaborations in various international projects.
• to promote the implementation of national and international technical challenges in terms of creating a scientific and technological basis for the production of composite nanomaterials by using energy-efficient SHS processes.
Participating Institutions
LEADING
Institute of Chemical Physics of the National Academy of Sciences (IChPh NAS RA)
PARTICIPATING
G. Tsulukidze Mining Institute (IMM)
PARTICIPATING
Ivane Javakhishvili Tbilisi State University/ E. Andronikashvili Institute of Physics
