A University of Navarre research team, made up of Irene Esparza, José María Fernández, Carolina Santamaría, María Isabel Calvo and José M García-Mina, have studied the influence of a number of metals in giving wine its colour. The work concluded that a slight change in these elements substantially modifies certain aspects of the quality of the ferments.

Scientists know that colour is one of the main parameters that enable the excellence of the product to be measured, providing as it does information about structure, body and taste. In fact, it is known that the hues, varying from bluish red to an earthy orange, are influenced by -amongst other factors – the stability and reactivity of metals present, such as iron, zinc, copper and manganese.

To carry out the study, they took samples of the Tempranillo variety of grape from a plot supervised by Evena (the Navarre Viniculture and Enological Station), located in Erriberri (Olite) in Navarre. The sample musts and wines were taken from three successive harvests starting in 2002 and which were subject to identical fermentation treatments, the only differentiating factor being meteorological conditions.

Using this method, the preferred location for the metal components in the grape seeds was identified and also how their proportion is modified during the fermentation process. The results show that most iron concentrates in the skin of the seed and that the amount of this metal, together with that of copper, drops considerably in the first days of fermentation.

Shades of colour a la carte

Moreover, the researchers derived a mathematical expression that enables the quantification of these colour changes in a precise way, thanks to which "the wine-producer can measure the shade of colour with great precision and thereby have objective indexes of quality". This will be published shortly in the specialised magazine, Analytica Chimica Acta.

They also concluded that a small quantity of iron in wines produces an increase of between 8% and 30% of its blue component, with a consequent similar decrease in its percentage of red. Finally, in subsequent studies results will be presented as a function of varying the quantity of other metals, such as aluminium or copper, in order to determine the effect on changes in colour.

Background

The CuproBraze process is a relatively new technique for manufacturing heat exchangers, particularly automotive radiators. Developed by the International Copper Association, CuproBraze radiators have already proved themselves in US road tests, and the process is showing promise in a range of other heat exchanger products as it offers significant advantages over existing systems, according to the developers. Recognising the potential of the CuproBraze process, Seco/Warwick has marked its one hundredth anniversary by building a specialist furnace at its Development Centre in Titusville, Pennsylvania, USA, to conduct brazing trials and prototyping work on heat exchangers.

CuproBraze technology enables the manufacture of light, strong, efficient and compact heat exchangers, including oil coolers, heater cores, charge air coolers and condensers, from high strength and high conductivity copper and copper alloys. These alternative materials and technology offer several benefits over existing systems, including a 10% cost saving over conventional aluminium heat exchangers while offering better energy efficiency. Scrap levels from the CuproBraze process are low as rejects can be easily re-brazed, and less energy is required in the brazing process itself. Brazing is carried out at 300°C lower than the melting point of the materials, and the system is much less sensitive than aluminium to rapid heating and cooling cycles.

In comparison to copper/brass systems, CuproBraze has stronger brazed joints, is 35-40% lighter and is easier to recycle. In addition, the braze filler is a non toxic alloy with good wetting and adhesion with no further use for toxic lead solder in the process.

The new braze filler is an alloy of copper, tin, nickel and phosphorous with a metallic content of between 75-90% depending on the joint position and application technique. Different types of binders and braze alloys can be used for the tube to fin joints and tube to header joints, and application can be either by spraying, brushing or rolling.

The new furnace developed by Seco/Warwick highlights some other advantages of the CuproBraze process. The furnace is of a compact front loading design, and it requires a floor area of only 8x7m. However, a free working load space of 1200x1200x400mm is available, along with a larger alternative chamber size of 1500x1500x600mm. The heating system consists of a high pressure, high velocity recirculation fan passing the atmosphere over 90kW electric elements to provide the optimum flow of nitrogen atmosphere through the workload to obtain the tight temperature uniformity required for optimum brazing. At the operating temperature of below 750°C, this method of heating is the quickest way of transferring heat to the workload.

The whole process is rapid, with purging, heating and one complete cycle of cooling being achieved in 20 minutes for a single layer of radiators (16kg) or 30 minutes for a double lay (32kg). In Seco/Warwick's new furnace, the speed and accuracy of the process is ensured with a PL system responsible for temperature control sequencing and logic. Such control will achieve optimum conditions for the CuproBraze process, for which Seco/Warwick expects to see growing demand.

Background

The initial discovery of superconductive materials was made in 1911. Before 1986, the critical temperatures for all known superconductors did not exceed 23 Kelvin (23K or –418°F; 0K is absolute zero or -459°F). Before the discovery and development of HTS materials, the use of superconductivity had not been practical for widespread commercial applications, except for magnetic resonance imaging (“MRI”) and superconducting magnetic energy storage (“SMES”) applications, principally because commercially available superconductors (i.e. LTS materials) are made superconductive only when these materials are cooled to near 0K. Although it is technologically possible to cool LTS materials to a temperature at which they become superconductive, broad commercialisation of LTS materials has been inhibited by the high cost associated with the cooling process. For example, liquid helium, which can be used to cool materials to about 4K (-452°F), and which has been commonly used to cool LTS materials, is expensive and relatively costly to maintain.

In 1986, a breakthrough in superconductivity occurred when two scientists, Dr. K. Alex Muller, who is currently under contract as a consultant to ASC, and Dr. J. Georg Bednorz, at an IBM laboratory in Zurich, Switzerland, identified a ceramic oxide compound which was shown to be superconductive at 36K (-395°F). This discovery earned them a Nobel Prize for Physics in 1987, which is one of four Nobel Prizes that have been awarded for work on superconductivity. A series of related ceramic oxide compounds which have higher critical temperatures were subsequently discovered, including those being used by American Superconductor.

What is Superconductivity?

Zero Resistance

Superconductors lose all resistance to the flow of direct electrical current and nearly all resistance to the flow of alternating current when cooled below a critical temperature, which is different for each superconducting material.

Perfect Conductor of Electricity

A superconductor is a perfect conductor of electricity; it carries direct current with 100% efficiency because no energy is dissipated by resistive heating. Once induced in a superconducting loop, direct current can flow undiminished forever. Superconductors also conduct alternating current, but with some slight dissipation of energy.

Critical Temperature

Superconducting materials known today, including both high temperature superconductor (“HTS”) and low temperature superconductor (“LTS”) materials, need to be cooled to cryogenic temperatures in order to exhibit the property of superconductivity.

HTS vs LTS

The differences between high and low temperature superconductors can best be explained using the figure 1. This graph illustrates the complete loss of resistance to the flow of electricity through wires of an LTS material (niobium-titanium alloy) and an HTS material (bismuth-based, copper oxide ceramic) at the critical temperature T_c which is different for each superconducting material. The specific HTS material in this chart has no electrical resistance below 108K (-265°F) as opposed to the specific LTS material in this chart, which has no electrical resistance below 10K (-441°F).

Conditions Required for a Material to Exhibit Superconducting Behaviour

· The material must be cooled below a characteristic temperature, known as its superconducting transition or critical temperature (T_c).

· The current passing through a given cross-section of the material must be below a characteristic level known as the critical current density (J_c).

· The magnetic field to which the material is exposed must be below a characteristic value known as the critical magnetic field (H_c).

These conditions are interdependent, and define the environmental operating conditions for the superconductor.

Advantages of Superconducting Wire

Superconducting wires provide significant advantages over conventional copper wires because they

· Conduct electricity with little or no resistance and associated energy loss

· Can transmit much larger amounts of electricity than conventional wires of the same size

Background

Combining old-fashioned metal working techniques with modern technology, engineers at The Johns Hopkins University have produced a form of pure copper metal that is six times stronger than normal, with no significant loss of ductility.

Previous Attempts to Strengthen Metals

The achievement, reported in the 31 October issue of Nature, is important because earlier attempts to strengthen a pure metal such as copper have almost always resulted in a material that is much less ductile, making it more likely to fracture when stretched. Strength refers to how much stress a metal can tolerate before its shape is permanently deformed.

Potential Applications of Stronger Pure Metals

En Ma, a professor in the Department of Materials Science and Engineering at The Johns Hopkins University, and coauthor of the paper said, ‘We were able to get the strength of pure copper up to and beyond that of copper alloys without adding any other metals to it and without sacrificing ductility.’ Ma went on to say that such strong and tough pure metals could have applications in microelectromechanical systems, for which suitable alloys may be more difficult to produce and may be more prone to corrosion, and in biomedical devices, in which a pure metal may be preferable to alloys that could expose the body to toxic metallic or non-metallic elements.

The Strengthening Process

To make pure copper stronger, the Johns Hopkins engineers had to employ extreme cold and mechanical manipulation, followed by a carefully designed heat treatment stage. ‘A real significance of this project is that we showed what traditional metallurgical processing can do in the new era of nanotechnology’ said Yinmin Wang, a doctoral student and lead author of the paper.

Rolling

The researchers started with a 1 inch (25.4mm) cube of pure commercial copper and dipped it into liquid nitrogen at a temperature of -196°C for three to five minutes. After removing it, the researchers rolled the copper flat, cooling the sample between rolling passes until it had reached a thickness of about 1mm This affected the metal’s microscopic crystals, each consisting of atoms arranged in a lattice pattern. The severe rolling deformation created a high density of dislocations, meaning that atomic planes had been moved out of their proper position within the lattice. The cold temperatures kept these defects from quickly moving back into their original alignment.

Heat Treating

Next, the copper was heat treated - three minutes at 200°C. As it heated up, the dislocations began to disappear in a process called ‘recrystallisation,’ said Wang. ‘New, ultrafine crystal grains formed that were almost dislocation-free. The higher the stored dislocations’ density after rolling, the finer the recrystallised grains during heating. In our copper, these new grains were only a couple of nanometers in size, several hundred times smaller than the original crystals, making the copper much stronger than it was in its original form,’ he continued.

Why These Materials Are Stronger Than More Conventional Materials

This change occurred because of the reduction in grain size to a level similar to that of nanocrystalline materials, which are defined as materials with grain sizes less than about 100 nanometers. When the grains are smaller, Ma explained, more grain boundaries exist to block the moving dislocations, and the metal's strength is increased.

However, by carefully controlling the temperature and the timing when they heated the metal, the Johns Hopkins engineers allowed about 20-25% of the copper’s crystals to grow to a larger size in a process called ‘abnormal grain growth’, i.e. non-uniform grain growth. According to the researchers, this final mix of ultrafine grains and larger ones, described as ‘bimodal distribution’ is what gave the new copper its coexisting high strength and ductility. ‘By manipulating the grain size distribution starting from a nanometer-scaled grain structure, we reached an inhomogeneous microstructure that is stable during stretching,’ said Ma. ‘That reinstated the copper’s ability to stretch uniformly without fracture, a feature very important for the formability of the high strength copper when processing it into different shapes in forming operations.’

Application to Other Metals and Alloys

Next, the researchers plan to test their process with other pure metals as well as with metal alloys to see if it produces the same change in mechanical properties. ‘Materials with uniformly nanocrystalline grains can give you very high strength, but usually not enough ductility’ said Ma. ‘They are also difficult to process, often involving compaction of nanocrystalline powders. If you want a metal that is both strong and ductile, you may want to go down the bulk processing route. Our work demonstrates that extraordinary properties can be derived from a nanostructured material by first creating and then tailoring the ultrafine grain structures.’

Background

Stainless steels and heat resisting steels are ferrous alloys to which a minimum of 12% chromium is added. A 12% chromium stainless steel will resist corrosion or ‘rusting’ when exposed to weather. To obtain greater corrosion resistance for more severe applications, the chromium content may be raised to as high as 27%.

Stainless steels often contain other elements which are added to modify their properties. The effects of various elemental additions are reviewed in the following sections.
Carbon

In the majority of stainless steel grades carbon is usually held to 0.08% maximum in the austenitic grades and preferably much less. For example, the grade sometimes specified for welding, 304L, has carbon restricted to 0.03% maximum. Higher carbon contents up to 1.00% render some of these steels amenable to conventional hardening and tempering heat treatment for the purpose of developing high strength and hardness levels e.g. the 440 grades.
Nickel

Nickel is the most common element added to these steels and when added in quantities of 8.00% or greater, develops the austenitic series of grades. Lesser amounts of nickel will produce the duplex austenitic-ferritic grades.
Molybdenum

Molybdenum improves passivity of the surface resulting in increased corrosion resistance, particularly pitting in chloride environments.
Titanium

This element is a strong carbide former and is very effective in preventing precipitation of chromium carbide during welding. Chromium carbide precipitation adjacent to welds can result in intergranular corrosion or weld decay.
Manganese

Similarly to nickel, manganese promotes the formation of austenite and in certain grades partially replaces nickel. It is also used in the free-machining grades to which sulphur and selenium additions have been made.
Silicon

This element is added in quantities of around 1.00% to improve scaling resistance of austenitic grades when used at higher temperatures.
Copper

This element improves corrosion resistance in certain applications. An addition of 3.00 - 4.00% improves resistance to attack by sulphuric acid.
Sulphur

The sulphur content of these steels us usually kept below 0.03%. By increasing sulphur to around 0.2% there is an improvement in machinability but the corrosion resisting properties are severely impaired in many instances.
Niobium and Tantalum

These are carbide stabilising elements and act similarly to titanium. They are more commonly used in heavier sections. Niobium is used in stabilised welding rods and is preferred to titanium in this application.
Nitrogen

As an alloying element nitrogen acts to promote the formation of austenite. It can dramatically improve the yield strength of austenitic grades.

Background

Stainless Steel has long been the first choice of designers, manufacturers and users of cookware through its unique combination of properties that provide highly attractive benefits. For pots and pans optimum heat transfer is achieved using a bonded Aluminium or Copper base. In the best quality items this base has a ‘sandwich’ construction with the Aluminium or Copper being completely enclosed with Stainless Steel inside and outside.

Advantages for Stainless Steel for Cookware

Both the professional and amateur user value the fact that stainless products do not stain, chip or rust, are robust and do not affect the flavour of the food, plus they are easy to clean and dishwasher safe. Volume production ensures that high quality finished goods, which with appropriate care can last a life-time, are available at competitive prices. What’s more, being fully recyclable, stainless steel has good environmental credentials, with most producers making new stainless using a high proportion of recycled scrap.

Why Manufacturers Like to Use Stainless Steel for Cookware

Manufacturers welcome designs in stainless steel as the material is readily formable and weldable as well as being easy to finish with a range of attractive finishes. They also like the high quality image that stainless steel tends to provide for their products.

All this means that designers enjoy working in stainless knowing that their products will be easy to make, popular amongst buyers and long lasting.

The Increasing Use of Stainless Steel for Kitchen Applications

The popularity of stainless steel in the kitchen, promoted by campaigns throughout the world, such as ‘Stainless Steel Appeal’ (www.stainlessappeal.com) in the UK, continues to drive growth in world consumption upwards by over 5% per annum. The last ten years has seen more and more stainless steel appearing in kitchen items from toasters to kettles, ovens to microwaves, dishwashers to washing machines and fridge doors to kitchen cupboards.

Case Study - Camerons Cookware

So when designers come to develop new cookware products it is hardly surprising they think of stainless first. Some products recently introduced to the UK highlight how stainless steel aids innovative cookware design. All designed by Chris and Anne Malone of Colorado Springs, USA these products stem from a lifetime interest in cookware and good food.

Cookware Designer Chris Malone said “We developed the Camerons Stovetop Smoker to bring exciting and healthy new flavours to the home stovetop. The BeerRoaster is our solution to dry, flavourless roast chicken whilst the Multi-Roaster filled an obvious gap in what was available on the market. I never considered any material other than stainless steel for its excellent combination of properties, the freedom it gives the designer and the ease of manufacture of the products. These new products have proved very popular in the USA and I hope that UK cooks, chefs and gourmets get as much enjoyment from them.

	Camerons® Stovetop Smoker® allows you to smoke foods of all types on your own stove. Smoke-cooking is a healthy way to infuse flavour without the use of fats, salts or oils and that means no added calories either. Hot-smoking food retains moisture and natural cooking flavours so foods don't dry out or get tough Smoker also doubles as a steamer, so you really get two great cookers in one product Works well with all meat, seafood, and poultry dishes and it transforms ordinary vegetables into delicious main courses
	Camerons® Chicken Beer-Roaster® allows you to enjoy a full size fresh broasted chicken indoors or outdoors on your barbeque using your favourite beer, marinade or fruit juice to enhance the flavour. The vertical design allows reduced fat while maintaining the moisture.
	Camerons® Multi-Roaster® is actually three top quality stainless steel cookware products combined to roast, sauté, casserole and bake your favourite foods The oval 11.5 Litre Roaster, can hold a 20 lb (8.5 kg) Turkey, Large Chicken, or Medium to Large Roast The Aluminium base insert for better heat transfer and no hot spots The bottom can be used as a Sauté Pan or Stock Pot whilst the top can be used as a Sauté Pan, Open Casserole or Serving Tray