Tiny is lovely – development trends of metallurgy in 21st century

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“(…) followed by an escort of wheelchairs, manoeuvring skilfully. The sun is shining on nickel-plated spokes. Anyway, we are already producing nickel and we will be producing more of it.”
Sławomir Mrożek “Żal” (story collection “Słoń”, published by Wydawnictwo Literackie, Kraków, 1957).

 

Metallurgy. The word usually does not usually carry the most pleasant connotations:  A lot has changed since then. Metallurgy of the 21st century has a completely new face. It delivers modern materials for modern technologies, and in many cases, it should be associated with a sterile laboratory rather than with smoking chimneys. The change of the image of metallurgy is connected with the development of nanotechnology and molecular engineering. Contemporary metallurgy uses the latest physical and chemical developments in order to design materials of unique features. Particularly interesting are the physicochemical properties of metallic nanoparticles and conductive polymers.

 

The first class of materials derives directly from classic metals, although the break-up of their grains into the size of several to several dozen nanometres allows to observe phenomena which cannot be observed in the case of macroscopic objects – in this size scale, metals frequently lose their metallic character, gain some semiconductor features, and their chemical reactivity becomes completely surprising. The other class of materials with very interesting practical features are conductive polymers – materials related to plastics from the chemical and structural point of view, but featuring the electrical conductivity of metals.

 

One of the first concepts of nanotechnological devices belong to K.E. Drexler. A nanoassembler was supposed to be a hypothetical, miniature device capable of building organised structures from single atoms. The basic problem connected with the operation of such a device is the so-called “problem of sticky fingers”. Even if we managed to build a manipulator so small that it could move single atoms, they would immediately form chemical bonds, and in consequence, they would only cause the enlargement of the manipulator. It is connected with a high chemical reactivity of isolated atoms. The only “material” that can be used in this case as a building material are noble gases.

 

On the other hand, nanostructural materials have existed in the natural environment for billions of years: the weathering of igneous rocks and the formation of loam can be defined and nanocorrosion, wood and soil are also nanostructural materials. Particularly important is a possibility to design and synthesize materials of a precisely defined structure and predictable properties. Nanotechnology can be defined as the ability to work at the level of atoms, particles and supramolecular systems in order to understand, create and use structures, materials and devices of completely new properties being a result of their structure in a small scale. Therefore, nanotechnology enables an efficient control of the structure of matter at the level of atoms and particles.

 

In a straightforward implementation of Drexler’s ideas there is one catch – building any macroscopic object with the use of this method is impossible. For example, 1 cm3 of water contains about 1023 (100 000 000 000 000 000 000 000) atoms. If someone could carry out an assembly process with a very high speed (one billion atoms per second), building a block of a side length equal to 1 cm would take more than 3 million years. This approach, although tempting, does not really secure “control over the structure of matter”, because putting in order several or even several hundred atoms is definitely not enough to build a functional structure.

 

For a long time we have known methods of an indirect control of the position of single atoms. Chemical synthesis, controlled crystal growth and self-assembly make is possible to build very small structures (also at the atom level) but only with the use of macroscopic tools. Also, at the current technological level, the techniques used in electronics (lithography, epitaxy, and others) allow to build organised structures of dimensions from several dozen to several hundred nanometres. Biological and biomimetic processes can also produce significant quantities of precisely assembled molecular systems in a short time.

 

Therefore, nanotechnology can be described as an interdisciplinary science at the crossroads of biological sciences (biochemistry, biotechnology, genetic engineering), electronics, chemistry and materials engineering (picture no. 2).

 

The interdisciplinary character of nanotechnology is primarily manifested in a large variety of materials (from single particles of organic compounds to alloys and sinters) and a number of their applications (electronics, telecommunications, medicine, and many others). In testing the properties of nanomaterials, practically all available research and testing techniques are used: microscopy of nuclear forces, electron and optical microscopy, X-ray diffraction, and all possible spectroscopic and electrochemical techniques.

 

Development of automotive industry…

 

The nanotechnological revolution begins to have more and more influence on the automotive industry. The application of nanotechnology in the automotive industry is very versatile, from power transmission systems, light and durable constructions, new sources of energy, reducing the pollution of the environment and less energy consumption to easier recycling of worn-out parts. The visions of vehicles created with the use of advanced nanotechnology cover environmentally-friendly developments such as CO2-free engines, self-cleaning windows and car bodies, more silent operation, and even adjusting the colour of bodywork to the user’s mood.

 

Nanotechnology is already present at the assembly plants of the automotive industry, for example, in the form of modern anti-glare coatings on car windows, and polymer nanocomposites used in the production of light and durable elements of bodywork and chassis. Currently, they are the only nanotechnological materials used in the process of batch production in the automotive industry. Next to be implemented seem to be new anticorrosive coatings with polymer composites containing nanoparticles of silicon monoxide. These materials are characterised by high mechanical strength and resistance to scratches, they adhere well to the surface of metals, and provide excellent protection against corrosion.

 

Many other possible applications are currently tested in laboratories, or they are at a development phase. Theoretical analyses have shown that decreasing rolling friction, air resistance and the weight of the power transmission system by 30 per cent will decrease fuel consumption by nearly 30 per cent, and it will therefore lower the amount of fumes and dust released into the atmosphere. According to the authors, the main source of savings does not lie in lowering the weight of a vehicle, but in lowering air resistance and decreasing frictions in the power transmission system. The analysis does not take into account a further increase of power saving connected with the use of the alternative sources of energy (fuel cells and photovoltaic cells). Particularly high hopes are connected with the introduction of fuel cells with polymer membranes. It is estimated that the fuel cells used in motor vehicles as a source of energy will lower the amount of harmful pollutants (mainly dust and nitric oxide) by about 70 per cent. Another significant breakthrough will be the development of new nanostructural metallic materials (for example, quasicrystalline alloys or composites reinforced with carbon nanotubes) for storing and producing hydrogen, commonly believed to be a fuel of the future.

 

The economical improvement of motor vehicle operation will also be a result of decreasing friction and increasing the strength of power unit elements. Durable and hard coatings of a low coefficient of friction will become indispensable, and of a particular importance will be nanocomposites whose matrix will constitute aluminium, nickel and iron, reinforced with nanodispersive materials of high hardness (SiC, SiO2, TiO2, BN, diamond), as well as chemically- and thermally-resistant polymers, such as Teflon. Besides decreasing friction, new nanomaterials should have much lower density, and lowering the weight of a vehicle will bring significant savings in energy consumption. Composites containing nanotubes and fullerenes are particularly promising materials. Calculations have proved that the mechanical strength of materials built of carbon nanotubes will be 50 times better than steel, with five times lower density. Currently, however, the production of nanotubes of precisely defined parameters on a large scale is expensive.

 

Many construction elements of vehicles are made of composite materials. Chassis and bodywork more and more often contain elements made of polymer matrix composites reinforced with glass fibre, carbon fibre, and even plant fibre. This approach brings both material savings as well as a lower consumption of energy. The application of materials of biological origin (for example, waste plant fibre as the reinforcement of composites) improves the environmental aspect of the manufacturing process.

 

The replacement of composites with nanocomposites (composites whose size of reinforcement particles is up to 100 nm) can bring a further improvement of mechanical properties, and lowering the weight of manufactured elements. Current production includes various elements made of polymer nanocomposites (nylon, polyolefins, polycarbonates, biodegradable polylactides) reinforced with carbon nanotubes, ceramic nanofibres, nanocrystalline silicates and nanoclays. A leading company in the use of nanocomposite materials for the production of vehicles is General Motors. So far, the materials have been used to make such elements as car bumpers, handles, and parts of upholstery. The introduction of nanocomposites has led to decreasing the use of polymers by 40 per cent, accelerating the production process and lowering energy consumption, which in total has brought down the production costs by 60-80 per cent. Additionally, these nanocomposites are non-flammable, which substantially increases the safety of using the vehicles, and the reduction of polymer content lowers the amount of toxic waste created during the production process and makes it easier to dispose of worn-out parts.

 

Another significant step in the nanotechnological revolution in the automotive industry (and not only there) will be the implementation of inexpensive and efficient photovoltaic cells into batch production. Currently, materials which can serve both as a solar cell as well as paint covering bodywork are in the phase of development. Many kinds of this type of material are already known, mainly ones containing modified nanocrystalline titanium dioxide and suitable pigments. Multilayer composites containing nanoparticles of germanium have also been developed, and they act as efficient photoelements suitable for being placed on the surface of bodywork.

 

It is worthwhile to mention here some other sources of clean energy for mechanical vehicles.
There are prototypes of engines powered by hydrogen gas, but a real breakthrough will take place when electric engines powered by hydrogen fuel cells will enter the manufacturing phase. As long as the construction of highly-efficient electric motors is usually not a problem, a serious problem is safe storage of large quantities of hydrogen (cylinders are too dangerous, and due to their high weight they add considerably to the weight of the vehicle), as well as the production of durable and efficient fuel cells. It is thought that the storage of hydrogen can be achieved with the use of metal alloys forming unstable hydrides, which undergo the dissociation process in not very high temperatures. The capability of such materials to accumulate hydrogen is very high and much better compared to pressure vessels, and even better than storing hydrogen in a liquid form. Some quasicrystalline alloys have properties which make it possible to use them as materials for collecting hydrogen. Also, cheap, durable and efficient electrolytes, catalysts and materials for the electrodes of fuel cells will be needed, and the role of nanotechnology is this process is enormous. Polymer nanocomposites can in the future become good electrolytes, and metal-ceramic composites seem to be good candidates for electrodes as well as catalysts.

 

The use of fuel cells will contribute to a significant improvement of energy saving by vehicles, the elimination of the combustion process will additionally stop the problem of harmful air pollution, and the lack of moving parts in the cells will ensure quiet and failure-free operation for a long time.

 

Other future applications of nanotechnology in the automotive industry will be connected with the use of nanoparticles for the purpose of modifying different types of surface in order to dye bodywork and the elements of accessories, as well as to create self-cleaning and superhydrophilic surfaces. These applications are discussed below in the section dealing with the use of nanoparticles for surface modification.

 

Apart from the use of nanomaterials as construction materials, it is also worthwhile to mention ceramic nanocomposites acting as catalysts removing toxic compounds from exhaust gases (mainly carbon monoxide, hydrocarbon, and nitric oxides). A particularly high catalytic activity, as well as chemical, thermal and mechanical stability are observed in materials containing cerium and zirconium oxides placed on a catalytically inactive substrate of aluminium oxide.

 

What follows from the given examples is that the role of nanotechnology in the automotive industry is significant and relates to many different aspects: lowering the cost of production and operation of vehicles, environmental protection, increasing the safety of driving, and even aesthetic values. We can expect that in the future the role of nanotechnology in the automotive industry, similarly to other domains and spheres of life, will become even more important.

 

Advanced materials in catalysis…

 

Growing fuel prices, a continuous decrease in the supplies of crude oil, and concerns related to the natural environment create a need to look for new, alternative, inexpensive and environmentally-friendly carriers of energy. In the future, hydrogen will be of a particular importance as a clean fuel. It has small molecular weight and a high calorific value, and the product of its combustion is water. This makes it a fuel friendly to the natural environment. One of the methods of its production is electrolysis. In this process, alongside the cathodic reduction of water particles, gaseous hydrogen is created. However, this method, as any other method, also has some drawbacks, for example: limited speed of production, high energy consumption, low efficiency, but first of all, high costs of making fuel cells, the price of which is considerably determined by the price of materials used for their construction. This creates a need to look for new materials, the use of which will lower the production costs of the cells and enable their widespread use. A solution to this problem is one of the challenges of contemporary metallurgy and materials engineering, which consists in the development of a material of a low value of overvoltage for the reaction leading to the development of gaseous hydrogen. Such materials would allow to improve the energy balance of the process of hydrogen production, and lower the production costs of the electrolysers. One of the challenges of contemporary technology is combining this type of construction with photovoltaic cells, which use advanced technologies and semiconductor materials, which enable an efficient conversion of solar energy into electric current. Therefore, the use of fuel cells, the utilization of solar energy, and the use of hydrogen as a fuel are of a significant importance for the natural environment. It is impossible not to mention the use of catalysts in the process of eliminating pollution released into the environment by combustion engines and the by-products of combustion, or the syntheses carried out by the chemical industry. Catalysis plays a very important role not only in fuel cells. The development of catalytic materials determines the development of the strategic branches of industry, for example, pharmaceutical, fuel and fertilizer industries. Materials of catalytic properties belong to the group of functional materials which are the most important for the economic development. Their development has a significant influence on the economic development. It is estimated that every year the market of catalysts absorbs 10 trillion dollars. It is also estimated that ca. 10 per cent of the gross domestic product of the countries which belong to the European Union are dependent on catalysts and the branches of industry which make use of them.

 

Limitations of contemporary electronics…

 

The main problem related to the development of contemporary electronics is the miniaturisation of devices and their components. One of the reasons for a continuous need to miniaturise electronic systems is a never-ending demand for smaller and more efficient computers of high computing power. From the perspective of materials used in electronics, the main problem in this type of systems is heat abstraction. Many commonly-available metals and materials cannot match constantly-growing requirements towards the used materials. These requirements mainly concern operating temperature and corrosion resistance. A future material of promising properties which gives hope of using it in the construction of electronic systems is graphene. It is still, however, a material of the future, and its use will still require a lot of research and testing by many science centres around the world. It should be mentioned that the electronic industry relies on using substantial quantities of noble metals. Hence due to the depleting natural resources of noble metals as well as rare earth elements, it is necessary to carry out research into the synthesis of new, cheaper materials of similar properties that could be their alternative. A challenge for electronics, apart from material limitations, is also the scale in which particular elements of circuits are made. The techniques of producing electronic circuits also constitute a challenge for contemporary nanoengineering. They frequently require advanced means and procedures which take advantage of the latest achievements of science and technology.

 

Aviation industry and astronautics…

 

Due to small mass and good strength, nanocomposites have a wide range of applications in the armaments and aviation industries. The best example is the B-2 Stealth bomber, whose construction to a large extent is based on modern nanocomposite materials.

 

Probably the most important part of aircraft, both passenger and military, in which nanomaterials have been used more and more often in the course of the recent years, are turbojets. The improvement of engine performance has brought and in the future can still bring substantial savings, since fuel consumption constitutes up to 40 per cent of the total cost of aircraft operation.

 

New nanomaterials and nanostructural coatings of high mechanical and thermal strength, elastic, with a low coefficient of friction and optimum thermal expansion make it possible to continue the improvement of jet engines, and in consequence, to lower the cost of operating aircraft and improve flight parameters. Reducing the density and improving the strength of materials will lower the weight of an aircraft, which can additionally be a source of large savings.

 

Nanotechnology is of significant importance not only to civil aviation, but also to air force and astronautics. In the case of air force, the role of nanotechnology consists in the production of stealth protective coatings and the development of new, analytical technologies, especially for the purpose of the detection of biological hazards.

 

Also, the use of new, “super” hard materials for the production of the cores of armour-piercing penetrating shells needs to be considered.
A further development of contemporary astronautics without nanotechnology is impossible to imagine. New light materials and new efficient sources of energy are elements indispensable to continue space exploration. The role of new, light and durable materials is similar to the role of materials in aviation: lowering the weight of an aircraft and increasing its strength leads to a substantial reduction of costs. Composites reinforced with carbon nanotubes can be a particularly valuable construction material for the vehicles of the future. Many elements of spacecraft are exposed to extremely high temperatures (engine nozzles, thermal shields), and the production of these elements is very expensive. Nanotechnological production methods with the use of nanocrystalline metals and ceramic nanopowders will allow to lower the temperature of processing the materials with a simultaneous improvement of their properties.

 

A very important aspect of nanotechnology is the development of new production methods of highly-organised thin layers. This achievement will contribute to the improvement of the efficiency of photovoltaic cells, and will add to the improvement of contemporary, heat-resisting ceramic shields.

 

Until now, a substantial development of technology has been connected with armament or space exploration. The situation is similar in the case of nanotechnology. A lot of “nano” products are currently too expensive to be used in everyday life. We need to believe that similarly to the cases of Teflon, Polartec™ and Velcro™ (commonly called Velcro tape), there will be a slow diffusion of space technologies into everyday life.

 

Metallic glass – material of unique properties…

 

A specific group of nanomaterials is metallic glass. It is a fully-amorphous material, with no structure both in nano- and micro-scale. It can be classified as a nanomaterial because its nanostructure (and actually the lack of it) is intentional. The last ten years have brought a significant development in the scope of production of metallic glass: it has been possible to produce shape castings with the speed of cooling in the order of 1–100ºC·s–1. These materials are at least twice as durable as steel, lighter and more corrosion resistant, and at the same time harder than ceramics and highly elastic. Initially, steel alloys in the glass state were produced only in the form of thin strips with the use of the technique of melt spinning. The first glass materials needed a cooling speed of the order of 106ºC·s–1, therefore, it was only possible to produce very thin layers of the material. In the course of time, new alloys have been developed, for which it was possible to achieve the glass state at lower cooling speeds. Currently, there are glass materials which have a reasonably low softening temperature (~400ºC), which means that additionally to the standard technologies used in the production of shape castings it is possible to use a technique similar to the production of plastics.

 

The unique properties of the alloy Vitreloy 1, a nice look (in particular, a distinctive metallic lustre, silver-grey colour, and resistance to corrosion) and quite a high price were the reasons why the first commercial use of the material was the production of golf clubs, followed by baseball bats, and high-quality tennis rackets. The tennis racket Radical made by HEAD was voted the product of the year 2003 by the magazines “Fortune” and “BusinessWeek” (picture 8). High resistance to cracking combined with high elasticity allow users to achieve much better sports results than in the case of using crystalline metals. Metallic glass is currently used on a larger scale to produce fishing, hunting (bows and firearms) and scuba-diving equipment. Unique aesthetic values of the material mean that it is also used in the production of jewellery, and thanks to its good mechanical strength, also in the production of watch cases for the fans of extreme sports.

 

An intensive development of the production techniques of metallic glass has resulted in a more common use of the material. Thanks to the exceptional hardness and elasticity of metallic glass, it has been used as an “environmentally-friendly” substitute of depleted uranium in armour-piercing penetrating shells. It is also used to produce the housings of specialist electronic devices, especially ones operating within the range of high frequencies (mobile phones, other telecommunication systems, digital video cameras and recorders). A common use of metallic glass in medicine is justified by its excellent mechanical strength combined with resistance to corrosion and biocompatibility. The material is typically used for the production of artificial knees and casings of artificial pacemakers.

 

Nanoparticles, nanopowders, nanomaterials – advanced materials in the role of surface modifiers…

 

Nanoparticles and other nanostructures have existed nearly from the beginning of the universe. Many theoretical models assume that the originally-existing nanomaterials had a predominant role in the creation of life on earth. Currently, Nature also takes advantage of different nanoparticles, for example, the beautiful colour of butterfly wings is connected with optical phenomena taking place on nanostructural surfaces. Nanopowders and nanoparticles, both metallic and non-metallic, have more and more applications. They can be used both as suspensions in liquids (for example, medicines, paints, lubricants) and in the forms bound to the surface of a solid body. The latter group of applications is much closer to metallurgy, as it can be a method of the nanotechnological enrichment of product surfaces.

 

The enrichment of metal surfaces with the use of nanomaterials (especially nanopowders) creates great possibilities. At the current state of knowledge, it is possible to develop superhard, heat-resistant and corrosion-resistant coatings on the surface of metals, to achieve the “biocompatibilisation” of surface, and to make the surface in virtually any colour.

 

Moreover, an important practical significance lies in the processing of a surface, which gives it a superhydrophilic or superhydrophobic character. The superhydrophilic effect consists in giving a material surface excellent wettability: water does not create isolated drops on the surface, but covers it with a thin, uniform layer. It is of significant importance in the case of car windows and bodywork: windows maintain full visibility during rain, which is important for the safety of driving, especially in difficult weather conditions. Furthermore, windows and bodywork remain clean because all dirt is easily removed by rain, which has a positive impact on the environment due to a decreased use of detergents and other cleaning agents.

 

The superhydrophobic effect also helps in maintaining clean windows and bodywork, and it consists in providing complete non-wettability. Also in this case, water (for example, rain) can quickly remove any dirt from the surface. It is worthwhile mentioning here a preparation called “Antigraf”, developed in Poland several years ago, which makes it possible to easily remove graffiti from the walls covered by the preparation.

 

Nanoparticle suspensions in liquids and in the form of layers have a characteristic intensive colour. The first use of nanoparticles, from a historical point of view, was stained glass. One of the most beautiful and well-known examples is the so-called “Lycurgus Cup”, dated at 4th century AD. The cup is made of glass containing nanoparticles of silver and gold distributed all over the material. In reflected light (when lit from in front), the cup looks intensely green, in passing-through light (when lit from behind), it is red.
Currently produced nanoparticles of metals allow to achieve practically any colour, which depends on the chemical composition, concentration, as well as the size and shape of particles. Besides decorative applications (paints, pigments, ingredients of cosmetics), the optical properties of the materials, both in the form of suspensions and thin layers, make them suitable to be used in sensors and very fast optoelectronic switches.

 

However, probably the most important use of nanostructural coatings is the development of biocompatible materials. It enables the production of implants which are easily integrated with the living tissue, as well as prevents the rejection of an implant and dangerous infections. It is estimated that in the future it will be possible to synthesize materials that will fulfil various functions in living organisms, and possibly support or replace ill organs. Another important task is the production of materials which do not integrate with the biological environment and do not get covered be a protein layer (for example, contact lenses).

 

The first works on implants (for example, artificial joints, dental implants) focused on achieving a suitable strength of metal elements for the purpose of maximising the lifespan of the implants. In the recent years, research has focused on the properties of implant surface and the interaction of the surface of materials with the biological environment. In contemporary medicine, the most important implants are the ones which can integrate with the bone tissue. An improper choice of material leads not only to the lengthening of recovery time (which results in an increase of the cost of treatment), but first of all, it can lead to an inflammatory condition. Furthermore, it can lead to the development of connective tissue, which results in a weak anchoring of the artificial replacement in the bone tissue. Because of this, it is particularly important to prepare the surface of an implant (which is usually a metal casting) before it is inserted into a patient’s body. The process of preparing a casting for implantation into a recipient’s body is called biocompatibilisation.

 

Noble metals yesterday and today…

 

For centuries, people have known noble metals such as silver and gold, which have been used in different spheres of life depending on their form. From the antique ornaments of stained glass windows, jewellery, dishes, pictures, tools and cutlery, to modern and functional materials that are nowadays used in chemical and industrial engineering, electronics, and medicine. A particular use is connected with the form of noble metals. For example, in order to ornament the Lycurgus Cup (4th century AD), the contemporary craftsmen used colloidal silver and gold. Depending on the angle of light incidence, the cup changes its colour from red to green (effect of the so-called “dichroic glass”). The beautiful red colour in the cup is triggered by colloidal gold, and the green colour is produced by the nanoparticles of silver (the size of particles below 50 nm). What is interesting, it was ancient craftsmen who discovered dichroic glass, which in the 1950s and 1960s was rediscovered by NASA and used in, for example, spacecraft as glass coatings protecting against cosmic radiation.

 

Currently, nanoparticles of gold are used in different fields of biology, chemistry and optoelectronics, and also in medicine for imaging, e.g. cancerous changes, or in cancer therapy. They are also used as “carriers” of medicines, and in different types of biosensors. Silver, contrary to gold, has for a long time been used in medicine, and nowadays it is obvious that it has some bactericidal and fungicidal properties. These non-typical and ununderstandable, as for those times, properties of silver were documented for the first time by Hippocrates in 400 BC, and the antiseptic properties of silver were treated as some “abracadabra”. Quite popular were all kinds of dishes and meal plates, cutlery and silver containers for storing water and food, which compensated for the lack of fridges at that time. It was also rightly believed that eating food from silver tableware protected users from illnesses, and even plagues. In the 14th century, during the plague of Black Death, a lower death rate was observed among the well-off, and small children were given a silver teaspoon to suck, which was supposed to protect them from infection. Until today, there is a saying in Great Britain “born with a silver spoon in mouth”, which means to have a better start in life. Owing to its price and antiseptic properties, silver, and to be more precise, the ions of silver are used in different types of antiperspirants, paints, grouts, and the like. Speaking of noble metals we should also mention palladium and platinum, which started to be used more commonly only in the 21st century. The irony is that platinum, discovered in Colombia in the 18th century, was initially called “little silver”, i.e. a metal of a lower value than silver. Today, platinum is a very precious metal which plays an important role in many branches of industry, especially in catalytic processes. Every driver knows it very well that their car would not be allowed on the road (leaving out technical aspects like the condition of the vehicle) if it were not for the fact that it has a catalytic converter, which limits the emission of toxic gasses into the environment. Catalytic converters became popular about 30 years ago, and there is no doubt that their development has influenced a rapid development of the automotive industry, and the awareness of environmental protection. Catalytic converters, depending on the type of fuel that a vehicle uses, contain different amounts of platinum, palladium, and rhodium. These metals reduce nitric oxides (NO_x) to nitrogen dioxide (NO₂), and oxidize carbon monoxide and hydrocarbon to CO₂, and to CO₂ and H₂O respectively. Platinum and palladium are also used as catalysts in many other processes, for example, in fuel cells, which are very popular. It is known that catalytic properties are directly related to the size, shape, and also the kind of metal which is supposed to “do the job”. It means that morphology has a strong influence on physicochemical properties, and what follows, their application to practical solutions. In catalytic processes, the required nanoparticles will have a size of up to 5-10 nm and a spherical shape, due to the developed active surface. However, more and more often we can read articles which show that shapes other than spherical have an equally-positive influence on the catalytic properties of nanoparticles. An additional asset of nanoparticles, i.e. particles of a size smaller than 100 nm, is the fact that they have a surface charge. The charge has an influence on their stability, and it also enables surface modification by means of the adsorption of “other” compounds, functional groups, etc. As a result, the same particle but with an additional “arm” gains new properties, for example, a possibility of transporting medicines to target tissues and releasing them in target places. A few sample photographs of the nanoparticles of gold in different shapes are shown below.

 

In summary, it can be stated that both in the past and today, it is nanometric metals that have been appreciated and have found a wide range of applications. Our advantage over ancient craftsmen is undoubtedly the fact that we understand how nanoparticles are created, as well as we know the mechanism, the kinetics of their formation. Consequently, this knowledge allows us to control the properties of nanoparticles, and it also ensures a possibility of their modification (functionality).

 

Conclusion

 

Nanotechnology is a dynamically developing branch of science. As it has been shown in the examples, it is not only a theoretical science, since its achievements are very quickly implemented in production. Although in many cases a high cost constitutes a possible barrier and the materials are used only to a limited extent (for example, is space technology), we should hope that in the future the cost of production will be lowered, and that the materials will have a wide range of applications in everyday life.

 

Particularly important is the role of nanotechnology and nanomaterials in the automotive industry. Lighter vehicles equipped with power units made of materials of a lower coefficient of friction contribute to lowering the cost of the production and operation of vehicles, but they also add to decreasing the consumption of fossil fuels and a significant reduction of environmental pollution.

 

Another extremely important use of nanomaterials is the modification of product surface. These coatings can protect the surface of tools against mechanical damage and corrosion, or to give products a desired look. Medical applications are particularly important – the development of biocompatible surfaces makes it possible to use implants which do not carry a risk of infection, and ones that easily integrate with tissues.

 

It is to be hoped that the coming years will bring a further development of nanotechnology, and that nanomaterials will be used on a more common basis.

Magdalena Luty-Błocho, DSc (AGH UST Faculty of Non-Ferrous Metals)  
Krzysztof Mech, MSc (AGH UST Academic Centre of Materials and Nanotechnology)
Professor Konrad Szaciłowski (AGH UST Faculty of Non-Ferrous Metals and AGH UST Academic Centre of Materials and Nanotechnology)Faculty of Non-Ferrous Metals

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