Materials as 'Clay in the Potter's Hand'

A look through the past into the future

Some people think that cultural changes in the history of mankind are related to the technological advances and development of new materials and processes. The fact that the three earlier periods in human life are known as the Stone Age, Bronze Age and Iron Age indicates the close link between man and materials. The related question to be asked, based on past materials and technological developments, is: "whether one can predict a future developments related to the field of materials science and engineering?" In order to examine the materials field from different points of view, let’s begin our materials journey through time. The importance of materials is significant in interpreting ancient cultures from periods prior the invention of writing. We know very little about the cultural and spiritual life that took place during those periods, and the information obtained depends on the materials that have been preserved. Earlier the culture, less information was preserved about it, and all that have been left is the materials (the shell), but not the spiritual and cultural life behind it.

Since the invention of writing and the ability to describe things in simplified manner, the important of materials as interpretation tool was reduced enormously, since one can learn about the cultural characteristics from the writings themselves. But materials are still important tool in the characterization of human cultures, even after the invention of writing: we wear materials, build our homes from materials, we create art using materials, and materials are used to create technological revolutions which follows by social revolutions. The relationship between materials, technology and culture can be studied from the behavior of ancient traditional societies. In such societies, like African traditional societies, the craftsman who works with metals is also the chief of religion, and the ceremonies associated with iron production are ritual. In those tribes only a small group of men participants in the metallurgical production. During the ritual ceremony of iron production, there’s a use of fertility-related and life creation imagers: the blowers are shaped in a phallic figure, while the ovens (into the blowers are insert) are shaped as a pregnant female. These societies describe the metals production from its ore as a magical mix of elements such as: wind, fire, and earth (ore), to create a new element (the metal).

Early materials, ancient technologies

Since the beginning of mankind, our ancestors began to use stones to make tools and weapons. It is usually assumed that this ancient period, known as the Stone Age, was started around the world two million years ago, before the Homo-sapiens ("wise man") intelligent human was borne. At the same time men were also used wood and bones, but the main material used to produce things was the stone. At the same time the pottery industry also began to developed, and people began to make pottery that have been used as storing food containers. Later, it was found that melting copper with tin creates new alloy called bronze. The bronze was used to create tools, weapons and jewelry, duo to its better hardness and strength with compare to pure copper. New period was born in mankind history - the Bronze Age. Mesopotamia and Egypt were the first to produce bronze tools. The new technology was spread from the Middle East to more places through the ancient world, and workshops were born, in which bronze was casting into a desired shape patterns to create tools and objects, including axes, knives, as well as jewelry, art and ritual artifacts.

In Israel, the copper mining metallurgy was began around 4000 BC, mostly in Timna mines. During the sixties of the 20 century, archaeological excavation was performed in the Judean Desert, conducted by the archeologist Pesach Bar-Adon (see references). A hoard was discovered at the Nahal Mishmar cave, including a huge collection of items from the Chalcolithic period (6,000 years ago; were the term chalcolithic comes from ancient Greek: khalkos "copper" and lithos "stone"). The collection included a variety of metallic objects, including crowns, standards, and objects made of other materials such as ivory and hippopotamus teeth. The main assumption is that the artifacts belonged to the ancient religious temple of Ein Gedi. The temple is about 12 km far from the cave of treasure, and evidences of rapid abandonment were found there. Scientific examination of the copper artifacts found in the cave of treasure showed significant differences between the manufacturing processes of the different objects. The simple tools were made by open casting of almost pure copper, which is typical to the ores found in the regime of Israel. The more complicated artistic artifacts were made of copper alloys containing antimony, nickel, arsenic and other elements, made by using the “lost wax” technique, and were probably used for ritual purposes.

These findings raise some important questions, such as: from where came the antimony, nickel and arsenic, which are not typical elements in the local copper ores found in the land of Israel? And why similar copper artifacts, produced by the “lost wax” technique, were not found elsewhere in the world at the same period? The differences in materials and technologies between the simple and the expensive metallic objects indicate the using of engineering considerations as well as metallurgical understanding, used by the ancient artist who created the artifacts. A research conducted by Prof. Goren from the Department of Archaeology and Ancient Near Eastern Civilizations, Tel-Aviv University, examined the ceramic molds of the expensive artifacts found in the cave of treasure, which were manufactured by the "lost wax” technique. The ceramic molds were produced from available materials, around the closest geographical area near the production place of the metallic objects. Therefore, investigation of the molds helps discovering the place where the objects were cast, but not in decoding the origin of the copper alloy.

Later in antiquity, different nations discovered the use of iron. Between the years 3000-2000 BC people in the area of Mesopotamia has been prepared iron metallic objects from iron resource found in meteorites. However, the beginning of the Iron Age was at the end of the second millennium BC, when the empires of the late Bronze Age began to collapse along with their cultural worlds, a thing which led to social, commercial, economic and technological changes throughout the ancient world, and led gradually to the development of iron-processing techniques. Around 1500 BC, the Hittites developed a method for producing metallic iron from its ores, and since then the use of iron have been spread throughout the ancient Near East. At the same period, serious weapons, made of iron, began to replace gradually the bronze weapons. It is usually assumed that the daily use of iron started around the 10th century BC. The Iron Age which started then, (in a sense) continues until our present days.

In the mid-18th century, a chain of technological changes occurred in England, which was spread to the rest of European and to the U.S., and cause the Industrial Revolution. Two significant discoveries allowed the Industrial Revolution: the first was the development of a method for producing iron by burning almost pure coal, called Cox (Coke), using special furnace called Blast furnace, and the second is the invention of the steam engine. In 1913 the stainless steel was invented, having excellent corrosion resistance. The very common steel, which is known to all of as from everyday life, is an iron alloy containing low amounts of carbon (up to 2% weight). In modern steel industry it is common to add additional elements, including magnesium, manganese, nickel, chromium, and silicon. The purpose of alloying the steel is to improve further properties such as: strength, hardness and the durability in wear.

The modern world: Science, engineering and material properties

After World War II a new engineering filed was developed: Materials Science and Engineering. This field deals with the relationship between solids states materials microstructure and their properties; study of the mechanisms that influences the materials properties, including: dislocations, diffusion, crystal growth, fracture mechanics, etc.; examining the reasons for materials failure, materials processing and manufacturing processes such as: casting, welding, and thin films production in the microelectronics industry, the development of new materials, materials selection considerations for engineering applications, materials characterization techniques, including: optical microscopy, scanning electron microscopy, x-ray diffraction, hardness tests, tensile strength test, etc. In this engineering profession researchers develop a variety of materials, including semiconductors and electronics industry materials, electrical conductivity polymers, quasi crystals, super conductors, nanomaterials, biomaterials, and “green” materials which are friendly to the environment. Many studies in the field of materials science are interdisciplinary, and include collaborations between the materials engineers and others among them mechanical and electrical engineers, physicists, chemists, biologists, geologists and even archaeologists.

The materials world around us is made of different combinations of atom, which through different bonding between them create a wide variety of materials such as ceramics, metallic alloys, polymers, composite materials and semiconductors. In order to illustrate the relationship between inter-atomic bonding and materials properties, we shall compare between the ceramic group of materials and the metals group. Ceramic materials contain metallic and non-metallic elements, and they are characterized by a crystalline structure, high hardness (resistance to the penetration of another body), high thermal and electrical isolation, brittleness, high temperature resistance and durability to aggressive chemical environments (such as acids). Metallic materials are also characterized by crystalline structure, but they have large number of free electrons, which are moving as an electron cloud shared by many atoms. Metals are brightening, having high electric and thermal conduction, they are ductile (having the ability to undergo plastic deformation), with good fracture toughness and low resistance to aggressive chemical environments.

Acceptable distribution of main materials groups includes the ceramics materials, which characterized by metallic and not metallic elements having a crystalline structure; metals are also characterized by crystalline structure, but with large numbers of free electrons moving as a cloud of electrons common to all atoms surround them; polymer, which are built of long chain of molecules that contain non-metallic elements; composite materials, which are artificial materials composed of two or more materials, so that the combination between them will create an improved material, having enhanced properties for a particular use; and semiconductors which are materials having electrical properties range from insulation to electrical conductor according to temperature changes and other factors

Most solid materials have a crystalline structure, in which atoms are arranged in periodic array, so there is a long-term order of atoms. Ideal crystal has a perfect order, but in reality there are no such perfect materials, and crystals contain defects called imperfections, which affects the material properties. There is a close connection between the manufacturing processes the material has been gone and the microscopic structure it has (the bonding between atoms, the density of atoms, the arrangement of atoms and the presence of defects in the material) and the macroscopic properties it owns. As illustration, a pure gold has a yellow color, but the color can be changed by alloying it, i.e., adding small amount of different elements to gold, with concentrations between a few to tens percent, depending on the desirable properties. For example, the combination between gold and copper will give an orange-reddish coloring, whereas adding silver, palladium, platinum, nickel and zinc will give the gold a silver tone (white gold). Atomic impurities at very low concentrations alter the electrical properties of semiconductor materials, whereas line defects named dislocations affect the ability of metals to undergo plastic deformation. The materials properties will be accepted in accordance with: inter-atomic bonding, the atomic arrangement and the material defects. These properties bring the materials engineer decide whether to use a certain material in certain applications, or to attempt to develop new materials with enhanced properties.

A world hidden before our eyes

Now let's deal with the production of today's materials, focusing on the tiny world hidden before our eyes. The idea of building Micro-Electro-Mechanical Systems (MEMS) was raised by the Jewish noble prize winner, Prof. Richard P. Feynman, on his famous lecture "There's plenty of room at the bottom", in 1959. In his lecture, Feynman claimed that in future, it would be possible to manipulate individual atoms, and ill people would no longer be operated by a human doctor, instead a sick person would swallow a "tiny robot" that will travel inside the human body to perform medical missions. The word nano, derived from Greek, meaning "small". And indeed, this is the orders of magnitude of viruses and DNA molecules. The uniqueness of the technologies is that it is small enough to minimize components considerably. In fact, the microelectronics industry is already now in the Nano-Age, because today the size of the integrated circuit lines (electrical wires) reaches the size of less than 50 nanometers, and the developing lines already have lines of 30 nanometers in size. MEMS systems combine mechanical elements, sensors, switches, gears, electronic components and optical components, manufactured on silicon wafers using technologies of clean room, getting dimensions of a few microns (one thousandth of a millimeter). These components are built with "top to bottom" technologies, i.e., material removal techniques. Processes are carried out mechanically, chemically, electrochemically, and the components are used in ink-jet printers and cars airbags acceleration gauges. Applied example of micro-electro-optical system is the medical capsules of Givenimaging Company, which was established in 1998. It is an endoscopic capsule, 26 millimeters long, containing a tiny video camera to diagnose gastrointestinal problems, with tiny electronic components such as: array of light sources, battery, transmitter and other electronic components. The capsule is swallowed easily, and it allows observation of the small intestine, as it finds its way through the digestive system.

Currently the MEMS are replacing dimensions into the Nano-Electro-Mechanical Systems (NEMS). Uniqueness of these systems is not only being much tinier then the MEMS, but also being the tiniest electro-mechanical machines to be built ever, as they are already at the molecular scale. At the nano-research we are talking about concepts of building systems in terms of "bottom-up", i.e., construction of the machine from the atomic and molecular-level, gathering and ordering the atoms together until the final product. In the NEMS filed, there is an overlap in the orders of magnitude between the MEMS components and the biological and chemical nano world. In the interface between the MEMS and the nano components it is important to have NEMS components that will be coordinators between the systems. For example, nano-biological components are supposed to handle various problems in the human body. These components are often needed to connect to pumps and pipes in the MEMS magnitude, and hence the NEMS is entered as an adapter interface, because for accessories in the micro-scale order, it is hard to connect and have mechanical hold of biological components in the nano-scale .In the nano world a neuron and an electronic chip can communicate with each other, creating neuro-technology. By using nano-technology, one can manipulate individual atoms and molecules, disconnecting them from the surface and moving them from place to place. This manipulation allows the arrangement of atoms and molecules in different ways. So, by using scanning tunneling microscope (STM), one can draw or write with these atoms, and connect the atoms together to build new and advanced materials.

There are many examples of experimental studies performed recently at the field of nanotechnologies, and we are going to describe a few of them now. For example, experimental study combining between electronic materials and biological materials was performed by Prof. Yosi Shacham from the School of Electrical Engineering, at Tel-Aviv University, in collaboration with the biologist, Prof. Shimshon Belkin, from the Hebrew University, for developing a toxins detection system, designed to enable coping with non-conventional attack of the water reservoirs. The system is based on a combination between bacteria with high sensitivity to toxins and a nano-electronic system. The heart of the system is genetically engineered bacterium, used as biological sensor for environmental pollution, quickly identifying the toxins in the water. A sophisticated nano-technology system, which includes pumps, control system for measuring temperature, many transistors and many other components, "communicates" with the bacteria, notice in their distress signals and broadcasts about it. Prof. Uri Sivan, Ohad Zohar and Dr. Alex Lahav from the Technion institute put the text of the Bible on a thin layer of gold (20 nanometers thickness) coating a silicon wafer of 0.5 mm2 area. To do so, a Focused Ion Beam (FIB) was bombing a gold substrate. The FIB accelerates ions to the gold surface, which impacts the surface and tears the atoms from it and by doing so they are exposing the silicon layer underneath. When observing the “nano-bible" with a scanning electron microscope (SEM), the silicon underneath the gold look darker than the gold itself.

Epilogue

Aviation and aerospace needs in the 20th century led to new materials developments, with high strength, light weight and durability to aggressive environments (extreme heat and cold, chemical attack, resistance to vacuum, etc.), including a variety of composite ceramic materials. Semiconductor materials development has brought the invention of the transistor, who led to the development of computing systems and worldwide communication. The high-tech industry have been developed thanks to new materials and by improving the properties of existing materials. And who knows, perhaps in the future our period would name the "Silicon Age". The interest of human beings in materials is expected to continue in the future along with new technological developments that would bring with them new revolutions in the history of mankind.

Thanks

Thanks to Prof. Yuval Goren from the Department of Archaeology and Ancient Near Eastern Cultures, Tel-Aviv University, Adi Yogev from the "Icon 2008" festival, Prof. Yael Hanin from the School of Electrical Engineering and the Nanotechnology Center, Tel-Aviv University, Dr. Slava Krylov from the School of Mechanical Engineering, Tel-Aviv University, Dr. Amnon Stupp from NASA Junction in Israel, Tel-Aviv University, and special thanks to Rafi Ashkenazi for the fruitful discussion.

For further reading

Ashkenazi, D., Eliaz, N. Minerals, Lattices and Gemstones – Crystallography and the Structure of Solids. Galileo 115 (2008) (in Hebrew).

Ashkenazi, D. Investigating Material Failures: Were the Titanic and Challenger Disasters Preventable?. Galileo 103 (2007).

Bar-Adon, P. (in Hebrew). The Cave of the Treasure: The Finds from the Caves in Nahal Mishmar. The Bialik Institute and the Israel Exploration Society, Jerusalem (1971).

Callister, W.D., Materials Science and Engineering an Introduction, Fifth Edition, John Wieley & Sons, Inc., N.Y. (1999).

Goren, Y. The Location of the Specialized Copper Production by the Lost Wax Technique in the Chalcolithic Southern Levant. Geoarchaeology, vol. 23(3) (2008).

http://www.zyvex.com/nanotech/feynman.html

• This article was published in GALILEO (Hebrew), February 2010 (Issue 138).

• Dr. Dana Ashkenazi received her Ph.D. in Mechanical Engineering from Tel-Aviv University and her first and second degrees in Materials Science and Engineering from Ben-Gurion University. She conducts research and lectures in the field of Materials Science and Engineering and also has great interest in popular science, art and human culture.