Method of Nano-Disperse Grinding
Universal Method of Mechanical Grinding (Milling) of all Sort of Materials to a Nano-Dispersed (Sub-Micron) Magnitude
Tech Area / Field
- MAN-MAT/Engineering Materials/Manufacturing Technology
3 Approved without Funding
Institute of Metallurgy, Georgia, Tbilisi
- University of Liverpool, UK, Liverpool
Project summaryThe problem actuality:
Grinding of hard and plastic materials, especially for getting nano-dispersed powders constitutes one of the main problems of currently used technologies of powder getting in many industrial sectors, particularly in the production of metal-ceramic, ferrite product, solid fuel for jet engine, ultra-strong and high temperature resistant materials for outer coatings of space shuttle launch vehicles, medical product powders, paint production etc.
Elaboration of more effective methods for getting nano-dispersed powders requires solution number of scientific and technical issues concerned not only to getting powder, but to the keeping of specific characteristics, inherent for super-dispersed materials, which are needed during converting the powder into concrete detail (please fined UNIMAT web page: http://www.nottingham.ac.uk/unimat/expertise/nanotech/index.phtml). For instance, according to the American standard “ASTM-C750-97”, specification (on a strategic boron carbide-B4C powder) admits ferrite presence up to 1.0% mass. This standard is shared nearly in a whole world. When grinding by traditional attritor-type device metallic wear debris compounds from 5 up to 10% mass and, in order to keep specific characteristics of B4C, its removal needs additional expensive chemical treatments in addition.
The project primary goals are:
Development of the effective and universal method of getting nano-dispersed powders of heterogeneous materials; Research of the principle of the grinding (milling); Significantly broaden class of materials grinding (milling) of which by the given method is well-grounded by economic, energy (power) and technological (processing) points of view; Estimation of abilities and advantages of new method in comparison with traditional methods of grinding (milling).
State of affairs and possible impact of the project on progress in given field:
As is well known, having unique characteristics (please fined -“Peculiarity of Atom Structure of Ultra-dispersed Systems” V.F. Petrushin, F.M. Zeleniuk, I.G. Andreev, A.V. Bukhanov, “Physicochemical of Ultra-dispersed System of Materials”, All-Union conference M. 1987, page.60), usage of sub-micron powders makes it possible to get materials with greatly increased operating performances.
Currently many ways are known for getting dispersed materials and these ways undergo constant development. However, experts are seeking new – off-centre methods, which could lay foundation for more effective manufacturing of sub-micron powder materials.
In industry as well as in the laboratory practice four systems are mostly used: Rotating (revolving); Vibrating (high-frequency); Percussive; and Jet milling.
Powder particles, made by different methods, possess different physical and technological characteristics. When using noted above methods of getting high-dispersed powders, we face serious problem bounded to the pollution of final powder by attached foreign solids; and of the poly-dispersed (unequigranular) composition of the final powder. These two shortages (bottlenecks) have their negative impact on the final properties of the converted product. The main shortage for Jet milling system is high power usage. At the same time in order to reach desired size distribution powder needs additional screening. The permanently renovated rare gas feeding process in the jet system is very expensive, so the gas is in permanent circulation. However, the process remains rather complicated because of necessity in filtering for separation of the finest particles from the main flow.
Based on the analysis of currently known data, one could say, that there is no single system for getting sub-micron materials, which could be applied effectively instead of any above noted methods even in the case of comparatively low level of final dispersion. By this point of view, suggested by us original method for getting sub-micron powder materials belongs to the universal category.
The original dispersing method will make it possible to: significantly broaden the range of materials that could be processed by the universal method; greatly cut down the needed time; and reach less fouling with wear debris (attached foreign solids). The disperse process occurs due to impingement of the particles causing their self-destruction. The rate of the moving particles comes to the speed of sound-wave or supersonic velocity (speed). They are coming across within the process and swiftly give in to grinding. The velocity of the particles directed to each other amounts 350 m/c. Total velocity within the active (particle meeting) zone amounts 700 m/c. Impingement process may be interpreted in several ways, that allows us regulate parameters of operation and productivity.
Principle of the given method significantly differs from the traditional ones. These distinctions have positive impact on the final processing characteristics of the end product. Here we can enumerate part of disperse materials, accessible to the process of the suggested universal method. For example, such a hardly grinding materials as titanium nitride - TiN, titanium carbide - TiC, tungsten carbide - WC, intermetallic - NiAl, alloy of SmCo, brass and boron carbide-B4C, as well as wood sawdust and a previously fragmented glass and plastic etc.
Expected results and their applications:
Suggested method will make it possible to reaching mono-dispersed (equigranular) system of the end product (powder). As was noted, the disperse process mainly occurs due to impingement of the particles causing there self-destruction that ensures less fouling with a wear debris (attached foreign materials). The maximum diametrical size of the derivable source material should amount ~ 5000 m (micron). As processing by new method, particle size composition of the pounded (end) material would be of 0.5 – 0.1 m (500-100 nm). The processing time scale, in comparison of traditional systems, could be reduced from some dozens hours to several minutes.
The universal feature of the suggested method could ensure its effective usage into different engineering processes. Such are: receipt of true emulsion, suspension, and homogeneous mixture for powder composition structure. It would be possible to physically formulate processes having place within the principally new method of material grinding to the sub-micron size on the base of experimental research. The universal feature of the method will make possible grinding of brittle, hard and plastic materials with a significantly shorted power expenses.
Primary scientific novelty, in a case of project development, would be research (exploration) and explanation of the operation principle of the universal method.
Practical benefits in a case of project development would be: Making up of principally new scheme of the convenient, inexpensive, universal device; grinding and mixing technology of different nano-crystal powders and liquids; upon the completion of the project there will be possible documentation assignation on using of new method for manufacturing (producing).
Project participants information:
The project team has accumulated a great experience in getting of super-fine ceramic and metal powders with an of-centre (nonstandard) device - “Rotator of Magnetic Induction”, which was created with direct participation of the given project’s Scientific Manager. The project team members have great experience of getting different alloys, compounds and composites with both, chemical-metallurgy and method of mechanical alloying.
In the frames of successful co-operation for materials grinding (milling) with other scientific organizations we can discuss the work made in interest of the Georgian Centre of High Technologies – “Institute of Stable Isotopes”. They used to apply traditional attritor device for grinding such a strategic material as B4C (boron carbide). In this case attached metallic wear debris came to some 5 to 10% mass and its removal needed additional expensive chemical treatments. When using off-centre technology suggested by the Institute of Metallurgy and Materials Science attachment of wear debris was reached no more than 0,2-0,3% mass. That excludes additional expensive chemical treatments and meets American standard “ASTM-C750-97” with the admitted presence of ferrite foreign solid up to 1% mass. Importantly, the grinding time was reduced from some 6 (six) hours to 0,4 hour (15 minutes) and obtained powder material was well criticized by the Institute of Stable Isotopes.
The project collaborator will be: acquainting with the reports of the project; exchanging the information during the project development; arranging the consultations; estimating the given results; participating in preparation of publications and patents; discussing the prospects of novelty applications; taking up of a partnership in commercialization of results etc.
The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.
ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.