University of San Carlos
Nasipit, Talamban, Cebu City, Philippines

CERAMIC INSULATORS: AN IDEAL FOR ELECTRICAL SAFETY

By:
Kirby Emmanuel C. Oraiz
Frank Joseph P. Ruiz
Ramel Joseph A. Derecho
University of San Carlos Talamban Campus
Nasipit, Talamban, Cebu City, Cebu

INTRODUCTION:

Science and technology are in continuous development. This leads to ever more demanding and intelligent technology.
The demands made on modern materials are increasing with the same dynamism. The features that are demanded include greater strengths for material-saving constructions, lighter components for energy saving, higher quality for more security and longer service life. After all, cost-effectiveness plays a crucial role.
Ceramic materials have in the past made an important contribution to this process of innovation.
Requirements for the successful application of ceramics include constructions that are appropriate to the materials and the manufacturing processes, as well as appropriate applications. The point is not that common materials can be displaced, but rather that customised products allow completely new solutions.
In order to make intelligent and effective use of the properties of ceramics, it is not sufficient simply to take an existing structural component and to replace it in every detail with a ceramic part. A drawing of the component used so far, however, together with a great deal of supplementary information, can show the way to the mass-produced ceramic component.
Thermal, electrical, mechanical loading and the chemical environment must all be taken into account in this process. Appropriate criteria relevant to each particular case mean that one or more suitable materials out of the wide range of available ceramics can be identified. The materials tables and associated descriptions in the following chapters will be helpful in this process.
The ceramic material for the new application must satisfy the technical analysis of the particular problem, must also offer an appropriate price/performance ratio throughout its service life, and may have to offer additional benefits.
The drawing is then checked for feasibility of implementation, and optimised for manufacture.
The tolerances required are often typical of those for metals, i.e. relatively close for all surfaces. In order to optimise costs it is necessary to distinguish between the general tolerances typical for ceramics, and special tolerances that may be needed for functional surfaces.
In a few cases it may also be necessary to consider the functional principles, and therefore perhaps a new design for the assembly.
The user will be steered through the process described above by the ceramics manufacturer.
After clarifying the technical details, the ceramics manufacturer can choose the optimum production procedure, bearing in mind the length of the production run, and can make a quotation.
Ceramics have already proven themselves in a wide variety of applications, and are being considered for others where high hardness, wear resistance, corrosion resistance and high temperature stability, combined with low specific weight, are necessary. The new high-tech materials achieve high levels of strength. Their figures are comparable with those for metals, and generally exceed those of any polymer.
The properties of the ceramic material are heavily influenced by those of the particular microstructure. The mechanical and physical properties can be influenced in different ways through the deliberate creation of particular microstructures, a process referred to as "microstructure design".
An important point always to bear in mind when applying ceramics is this - ceramics are brittle! The ductility of metal construction materials make them "good-tempered and well-behaved". They are able to forgive small errors of construction (incorrect tolerance), because they are able to disperse local stress peaks through elastic and plastic deformation.
Other features typical of metals include good electrical and thermal conductivity, and characteristics that are independent of orientation.

Ceramic materials, on the other hand, are usually electrically and thermally insulating, have high hardness figures, and may have very low thermal expansion. Their shape is, furthermore, extremely stable due to the absence of a capacity for plastic deformation. Compression strengths ten times greater than the bending or tensile strengths can be achieved. In comparison with metals, ceramics are particularly suitable for application at high temperatures, since the characteristics of ceramic materials are altogether less strongly influenced by temperature than metals and even then only at particularly high temperatures. Ceramics offer equally high benefits in terms of corrosion and abrasion resistance.
Because of these advantages, we find technical ceramics wherever we go. Without ceramic insulators, many household devices would not function. Likewise, without insulators and safety devices made of technical ceramics, a reliable electricity supply would be unthinkable. Ceramic substrates and parts are the basis for components and modules in all areas of electronics, while in machine and plant construction sliding and bearing elements provide low wear, corrosion-free function. Ceramic construction and insulation materials are indispensable to the industrial furnaces used in high-temperature technology. Even these few examples make clear that technical ceramics have an important role to play in today's world.
Ceramic components are often, however, not visible at the first glance. Nevertheless they play a crucial role, both in conventional applications and in innovative products.
The potential of technical ceramics has not yet been exhausted.

Electrical ceramic insulators are used in applications that require a non-conductive rigid component and/or source for heat dissipation. Although all ceramic formulations can be used in electrical applications, Steatite and Alumina (all grades) are the most common choice due to their excellent electrical properties. Electrical insulators commonly have coatings applied including glazing, teflon coating and metalizing. Metalization of ceramic electrical insulators is common practice for ease of installation into control panels and electrical boards through soldering.

Ceramic electrical insulators are most often used to provide non-conductive bridges between electronic components, however, they are also installed into control boards and boxes as a heat sink. At NCC, we are capable of producing a wide variety of geometries for ceramic heat sinks and electrical insulators. We have also developed long-running alliances with outside vendors and suppliers to provide our customers with a range of capabilites for ceramic fabrication that allows us to provide the best quality ceramic products for the best price.
I. HISTORY OF CERAMICS
The use of ceramics can be traced back to the early history of mankind. Reliable archaeological research has shown that the first ceramic figures were formed from malleable ceramic material and hardened by fire more than 24,000 years ago. Almost 10,000 years later, as our ancestors developed settled communities, tiles were first manufactured in Mesopotamia and India. The first useful vessels were then produced in Central Europe between 7,000 and 8,000 years ago.
Until the end of the Middle Ages, the smelting and process furnaces of the early metal industry were constructed using natural sandstone bonded with kaolinite or siliceous material. The development of synthetic refractory materials (Agricola, Freiberg around 1550) was one of the foundation stones of the industrial revolution, and created the necessary conditions for melting metals and glass on an industrial scale, and for the manufacture of coke, cement and ceramics.
The ceramics industry was an important partner to the chemical industry. Acid-resistant stoneware and porcelain were for a long time the most important materials available for corrosion protection. Nowadays they have largely been replaced by acid-resistant steels and enamels, but also by ceramics based on oxides, nitrides and carbides.
Beginning in the second half of the 19th century, electro-ceramics provided the momentum for industrial development. During this time, basic solutions for electrical insulation based on porcelain were developed.
It is difficult to determine the precise beginning of modern, high-performance ceramic materials. Until the turn of the 20th century, the development of ceramic materials had a primarily empirical character. Scientific methods were first applied to ceramics in the course of the 20th century.
The development of manufacturing technologies using quartz-enriched porcelain achieved bending strengths of more than 100 MPa for the first time. It was only in the 1960s, with the systematic development of alumina porcelain, that marked increases in strength, especially in large insulators for voltages over 220 kV, resulted in considerable weight reductions.
The growth of broadcast radio in the 1920s led to the need for special ceramic insulation materials that did not heat up under the influence of high-frequency electromagnetic fields. This led to the development of steatite and forsterite, both of which are still in use today. Research on oxide magnetic materials began in the 1940s (hard ferrites, soft ferrites). At this time, capacitor materials based on titanium oxide were also developed, and research began on the ferroelectric and piezoelectric properties of perovskite (BaTiO3). This made a wide palette of materials available – some even with semiconducting properties – for sensors, frequency selective components (filters) and capacitors with high storage capacity. Theoretical considerations are derived from basic research by Heisenberg, Dirac, Heitler, Londas, Hartre and Fock, among others.
A further important milestone was the introduction of sparkplugs made of sintered alumina (Siemens, 1929). The development of micro-electronics increased the demand for aluminium oxide materials, for example, as a material for substrates and housings. An important property of this material, in addition to high electrical resistance, low dielectric losses, high thermal conductivity, high mechanical strength and thermal shock resistance, is the vacuum tightness offered by these new types of material.
While the thermal properties were sufficiently well explained by the theories of Debye, it was necessary to develop a theory of fracture mechanics in order to explain mechanical properties. Whereas initially aluminium oxide and later zirconium oxide, were first used as ceramic construction materials, the outstanding properties of covalently bonded materials based on silicon (silicon carbide, silicon nitride, SIALONe etc.) were recognised and exploited at the end of the 1960s. Research into all these materials continues today. In addition to the approaches of fracture mechanics, new mathematical methods and computer simulations have been developed in order to understand the relationship between microstructure and properties through modelling. In parallel with the theoretical developments, process technologies have been optimised, extending as far as the introduction of completely new process sequences and sintering methods.
Known materials continue to be improved, new materials are being developed, and new applications are being found. The materials of today can no longer be compared with those that were on the market ten or twenty years ago. Scientific research is increasing our understanding of materials. New and improved manufacturing technologies have brought progress in the areas of quality, reproducibility and operating safety.

II. CERAMIC MATERIALS
Ceramic materials, on the other hand, are usually electrically and thermally insulating, have high hardness figures, and may have very low thermal expansion. Their shape is, furthermore, extremely stable due to the absence of a capacity for plastic deformation. Compression strengths ten times greater than the bending or tensile strengths can be achieved. In comparison with metals, ceramics are particularly suitable for application at high temperatures, since the characteristics of ceramic materials are altogether less strongly influenced by temperature than metals and even then only at particularly high temperatures. Ceramics offer equally high benefits in terms of corrosion and abrasion resistance.
Because of these advantages, we find technical ceramics wherever we go. Without ceramic insulators, many household devices would not function. Likewise, without insulators and safety devices made of technical ceramics, a reliable electricity supply would be unthinkable. Ceramic substrates and parts are the basis for components and modules in all areas of electronics, while in machine and plant construction sliding and bearing elements provide low wear, corrosion-free function. Ceramic construction and insulation materials are indispensable to the industrial furnaces used in high-temperature technology. Even these few examples make clear that technical ceramics have an important role to play in today's world.
Ceramic components are often, however, not visible at the first glance. Nevertheless they play a crucial role, both in conventional applications and in innovative products.
The potential of technical ceramics has not yet been exhausted

III. Technical Ceramics tableware, decorative ceramics, ceramic sanitary ware, wall and floor tiles and ceramic abrasives belong to the fine ceramics category.
The category of coarse ceramics includes, for example, brick or conventional refractory materials.
It also refers to refers to ceramic products for engineering applications.

High-performance ceramic is defined in DIN V ENV 12 212 as a "highly-developed, high-strength ceramic material, which is primarily non-metallic and inorganic and possesses specific functional attributes."
The concept high-performance ceramics is primarily used to distinguish them from traditional ceramics based on clay, including tableware, sanitary ware, walls and floor tiles as well as ceramics for civil engineering. This definition agrees with that of the "Japanese Fine Ceramics Association".
Structural or construction ceramics are terms that have not yet been standardised, referring to materials that in some way must withstand mechanical stresses, bending or pressure for example.
Functional ceramics are high-performance ceramics in which the inherent characteristics of the material play an active role, for example ceramic parts which possess specific electric, magnetic, dielectric or optical properties.
Electrical ceramics are high-performance ceramics that are applied because of their specific electric or electronic characteristics. Electrical engineering applications make use primarily of the excellent insulating characteristics and mechanical strength. The electronics industry also takes advantage of characteristics such as ferroelectric behaviour, semiconductivity, non-linear resistance, ionic conduction, and superconductivity.
IV. Materials Groups
Technical ceramics are often subdivided into groups in accordance with the definitions mentioned above. However since this does not permit unambiguous classification, they are alternatively grouped according to their mineralogical or chemical composition.
The following groups belong to the materials defined as technical ceramics: * silicate ceramics * oxide ceramics * non-oxide ceramics
Silicate ceramics, as the oldest group amongst all the ceramics, represent the largest proportion of fine ceramic products. The major components of these polyphase materials are clay and kaolin, feldspar and soapstone as silicate sources. Additionally such components as alumina and zircon are used to achieve special properties such as higher strength. During sintering a large proportion (> 20%) of glass phase material, with silicon dioxide (SiO2) as the major component, is formed in addition to the crystalline phases.
Included in the silicate ceramic materials category are: * porcelain, * steatite, * cordierite and * mullite.
Due to the relatively low sintering temperatures, the good understanding of how to control the process, and the ready availability of the natural raw materials, silicate ceramics are much cheaper than the oxide or non-oxide ceramics. The latter require expensive synthetic powders and high sintering temperatures.
Silicate ceramics are found, for example, in heat engineering applications, measurement and control engineering, process and environmental technologies, high and low voltage applications with typical uses such as insulators, fuse cartridges, catalysts, enclosures and in a wide range of applications in the electrical equipment industry. Silicate ceramics also continue to be used as refractory materials.
Oxide ceramics are defined as all materials that are principally composed of a single phase and a single component (>90 %) metal oxide. These materials have little or no glass phase. The raw materials are synthetic products with a high purity. At very high sintering temperatures a uniform microstructure is created which is responsible for the improved properties.
Some examples of oxide ceramics include * as a single-material system
- aluminium oxide,
- magnesium oxide
- zirconium oxide,
- titanium dioxide (as a capacitor material) * and as a multi-material system o mixed oxide ceramics - aluminium titanate - lead zirconium titanate (piezo-ceramics) o and dispersion ceramics - aluminium oxide reinforced with zirconium oxide (ZTA - Al2O3/ZrO2).
Oxide ceramics are found in the electrical and electronics industries, and often as structural ceramics, i. e.i.e. for non-electrical applications. They offer the typical properties suited to these applications, such as high fracture toughness, wear resistance, high-temperature resistance and corrosion resistance.
Non-oxide ceramics include ceramic materials based on compounds of boron, carbon, nitrogen and silicon. (Products made of amorphous graphite do not belong to this category!)
Non-oxide ceramics usually contain a high proportion of covalent compounds. This allows their use at very high temperatures, results in a very high elastic modulus, and provides high strength and hardness combined with excellent resistance to corrosion and wear.
The most important non-oxide ceramics are: * silicon carbide, * silicon nitride, * aluminium nitride, * boron carbide and * boron nitride. Electrical Engineering Area of Application | Parts | Why use ceramic? | Materials | Insulators | Antenna rods, spacers, feed-throughs, terminating sockets, threaded pipes, retaining pins, sleeves, adjusting pins, contact spring holders, potentiometer rings, regulator brings, regulator sockets, tubes, switch pins, slotted tube plates, protective tubes, external fuse tubes, fuse housings, fuse bodies, fuse tubes, fuse sockets, fuse bases, resistor bodies | Electrical insulation, low loss factor, mechanical strength | Steatite, cordierite, mullite, aluminium oxide, magnesium oxide alumina porcelain |

Figure 118: Electrical fuse bodies, sockets, etc. Figure 119: Resistor bodies

Figure 120: Sockets Figure 121: Low-voltage power fuses

Figure 122: Feed-throughs, sockets and insulators for halogen lamps

Figure 123: Heating element supports

| | | |
.

http://www.keramverband.de/brevier_engl/3/3_3.htm