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New Zirconia Based Materials

#2242


Advanced Nanocrystal Zirconia Based Material of New-Generation

Tech Area / Field

  • MAN-MAT/Engineering Materials/Manufacturing Technology
  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
8 Project completed

Registration date
02.07.2001

Completion date
13.09.2006

Senior Project Manager
Libby M D

Leading Institute
Institute of General Physics named after A.M. Prokhorov RAS / Laser Materials and Technology Research Center, Russia, Moscow

Supporting institutes

  • Blagonravov Institute of Machine Science, Russia, Moscow\nNIIIT (Pulse Techniques), Russia, Moscow

Collaborators

  • Politecnico di Milano, Italy, Milan\nUniversity of Sevillia, Spain, Seville\nUniversity of Sheffield, UK, Shiffield\nArgonne National Laboratory/Energy Technology Division, USA, IL, Argonne\nClemson University, USA, SC, Clemson

Project summary

Development of new constructional nonmetallic materials characterized by high strength and fracture toughness as well as chemical inertness in combination with high resistance to aggressive media over a wide temperature range is an urgent problem of modern science of materials.

Partially stabilized zirconia (PSZ) is one of such materials. It is a solid solution of zirconium dioxide with small additions of yttrium, calcium or magnesium and other rare-earth and alkaline-earth metal oxides. Ceramic (polycrystalline) types of these materials are extensively used worldwide today.

The Purpose of the Project is to develop a technology for governed synthesis of PSZ crystals within a wide range of compositions for specific practical applications basing on experimentally found relationships between PSZ chemico-physical properties, composition and technological conditions of the synthesis; to develop a technology to machine these super-strength materials; to manufacture and to test experimental specimens.

General Physics Institute of the Russian Academy of Sciences (GPI RAS) was the originator of technology for manufacture of new synthetic cubic zirconia (fianit) in the seventies and has developed a procedure for direct RF- melting of dielectric materials in a cold container (skull-melting) by now. The institute has developed special technological equipment to synthesize a nanocrystalline material based on zirconium dioxide (PSZ crystals) by directional melt crystallization. This PSZ crystal material is characterized by high strength, high hardness, high fracture toughness and zero porosity. The new technology of synthesis of single crystals is highly efficient, practically waste-free and currently allows manufacture of PSZ crystals up to 120 mm in length and 40 mm in diameter.

The PSZ crystals are superior to both metallic and extremely tough ceramic dielectric materials by mechanical properties. The PSZ crystals are similar to metals in strength, fracture toughness and thermal expansion coefficient while having much better characteristics of hardness, wear resistance, chemical and electrochemical stability. Under exposure to elevated temperature or aggressive media the PSZ crystals surpass significantly the ceramic constructional materials in mechanical characteristics. A better understanding and control of properties may be achieved with single crystals as compared to ceramics because there is no influence of grains and interfaces.

The Authors of the Project demonstrated experimentally that physico-chemical characteristics of PSZ crystals vary in a wide range depending on composition of the solid solution, type and concentration of ingredients and admixtures and, what is of most importance, on conditions of growth and subsequent treatment (temperature, media) of the material. Foreign investigators manufacture PSZ crystals by floating-zone technique and directional crystallization in a cold container. However, the crystals have been grown in extremely narrow composition range: ZrO2- 3mol% R2O3 (R=Y, Gd, Yb) and were only 10-30 mm size. Their reports on mechanism of crystal toughening confirmed that phase composition, structure and physico-chemical properties of PSZ crystals depended significantly upon the method and technological conditions of the synthesis.

Experimental data accumulated by the Authors of the Project provide evidence for principal possibility to govern synthesis of PSZ crystals, i.e. one can grow PSZ crystals with assigned physico-chemical properties by varying technological conditions of the procedure. A systematic study of <composition – conditions of synthesis – structure – properties> relationship is therefore of much importance and will mark a new stage in the technology of PSZ materials.

Implementation of all the advantages of the governed synthesis in a melt will result in manufacture of large PSZ crystals with a variety of pre-assigned physico-chemical properties that may be used to produce components of various applications, such as:

– Cutting elements of biological and medical equipment (scalpels and other microsurgical instruments for vascular, embryonic, ophthalmological, maxillofacial surgery, cardio- and neurosurgery, for section preparation in microbiology, etc).


– Heavy-duty insertions into loaded components of dental and orthopedic implants.
– Insertions for jewelry.
– Slicers for metalworking machinery.
– Draw plates and thread guides for wire and textile machinery.
– Compact friction assemblies for electronics and clockwork.
– Components of spacecraft equipment for long-term operation in outer space, heavy-duty units with resistance to thermal stress and fretting corrosion for aerospace application.
– Tribo-conjugations in car and aircraft engines.
– Sliding and rolling bearings and other heavy-duty friction units for operation under extreme conditions.

The governable synthesis technology will guarantee any required combination of physico-chemical properties of PSZ crystals to achieve a many-fold increase in reliability and service life of equipment operating under extreme mechanical stress, corrosive media, radiation, intense electromagnetic fields, elevated temperature, absence of lubrication, etc (bearings, engine valves, dies, guides, cutters, prisms in precise equipment, etc).

As demonstrated in preliminary studies of the Authors of the Project, surgical application of PSZ crystals is most promising. Owing to the excellent mechanical properties in combination with chemical inertness the PSZ crystals may be used to manufacture super-sharp “everlasting” surgical equipment ensuring minimum tissular and vascular traumatism. This is of primary importance for ophthalmology, maxillofacial, cardiac, vascular and embryonic surgery. Supersharpness of PSZ scalpel blades ensures high accuracy of line and even edges of the cut of required depth. It was also noted that as incision is being made by PSZ blade the tissue is «moved apart» with minimal trauma resulting in quicker closing and healing cut and formation of an accurate «delicate» postoperational cicatrix. The surgical performance characteristics of PSZ are competitive to diamond and in advance in comparison with sapphire, which are currently in use for such purposes. Moreover, design of PSZ equipment is not limited by size of starting material. The biological compatibility of these materials with live body tissues is a guarantee of their successful application as dental and orthopedic implants.

It should be emphasized that the Authors of the Project manufactured and tested several experimental articles from PSZ crystals, and the test results demonstrated great technological and commercial potentialities of this new ZrO2–based material.

Main objectives of the Project.

1. To synthesize PSZ crystals over a wide range of compositions. To establish <composition – parameters of synthesis – properties> relationships.

2. To clarify mechanism of oxygen redistribution in the crystals in the course of growth and annealing and its effect on physico-chemical profile of the crystals.

3. To develop technological procedures for governed synthesis of PSZ crystals with pre-assigned mechanical and physico-chemical properties.

4. To develop optimal techniques and regimens of PSZ crystal machining to manufacture articles of various designs. To manufacture pilot specimens.

5. To manufacture and to test articles for tribotechnical, constructional, medical, etc. purposes from the PSZ crystals in order to determine optimum application fields.

According to the methodology accepted, all experimental studies within the Project will be stratified into three main stages:

– serial experimental synthesis of PSZ crystals and overall investigation of their structure and physico-chemical properties;


– analysis of the experimental data and establishment of <composition – parameters of synthesis – properties> relationships, establishment of principal factors that determine properties of PSZ crystals and definition of optimum technologic conditions of the synthesis;
– development of technology of governed synthesis to manufacture large PSZ crystals with assigned properties, study of practical application aspects.

The study of <composition – conditions of synthesis – structure – properties> relationships will be performed by X-ray diffraction and differential-thermal analysis, high-temperature Raman and positron spectroscopy, optical and electron microscopy, DC AES, isotope oxygen analysis, X-ray fluorescence spectrometry.

The evaluation of crystalline-chemical, electric, thermal, strength and tribological properties of PSZ crystals will be carried out using modern analytical and testing equipment by methodologies and standards accepted in Russia and abroad.

The Participating Institutes have accumulated a many-year positive experience in the scientific research and experimental design and are recognized authorities in Russia and worldwide.

Starting Background: The considerable experience of LMT RC personnel in development of technology for synthesis and practical application of large optically homogeneous single crystals of cubic zirconia (fianits), in development of methods to grow single crystals of various oxide compounds by directional skull-melting in a cold container with RF heating are a good basis for achievement of the Project goals.

The great professional and intellectual resources of the participants in combination with their developments in methodology, technology, scientific research and design will also promote implementation and further commercialization of the Project results.

The Project completely meets the ISTC tasks and goals because the specific technologies and methods previously developed for military application will be used for synthesis and investigation of new advanced materials for wide peaceful use.

Expected results:

The Project will be focussed on experimental studies, and the experimental findings will present a considerable novelty because there were no such studies so far.

The following developments will be made on the basis of the experimental findings under the Project:

– high-efficiency waste-free technology for governed synthesis of ZrO2-based nanocrystalline materials of a new generation, i.e. large PSZ crystals that are non-metal materials of high strength and wear resistance, supreme fracture toughness;


– optimum technology to manufacture articles of different shapes for specific practical application.

These technologies will be used to synthesize PSZ crystals with a variety of pre-assigned physico-chemical profiles and to manufacture pilot techware of various applications. Basing on the test results a substantiated conclusion will be made as to the prospects for further application of PSZ crystals to solve high-priority technical tasks in science, medicine and industry.


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