WHAT DO WE DO WITH MATERIALS

Post 624 –by Gautam Shah

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We use objects for their many different qualities. Some are used for their structural properties, while others are useful due to their surface qualities. We try to find an object with the best combination of such attributes. Where such a combination is not easily or immediately available, we primarily try to change the object appropriately and secondarily we try to combine materials and create geometric compositions.

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Aerogel, extremely low density, low thermal conductive material. It is solid and feels like hard styrofoam to touch > Wikipedia image by Image policy

There are Four categories of essential qualities sought in objects for various purposes:

● Engineering Attributes:

Chemical -composition, phase, resistance, structure.

Physical -thermal, electrical, magnetic, gravity-metric, optical, acoustics.

Mechanical -stress/strength, form-ability, rigidity, toughness, durability.

Dimensional Features

Shape -camber, lay/orientation, out of flat, roughness, waviness.

Size -scale, proportion, orientation, nature of perception.

Surface Properties:

Colour -hue, tone, illumination, refractivity, reflectivity, opacity, transparency, fluorescence.

Texture -level and direction of illumination, perceptive organ, nature of contact, scale.

Pattern -random, rational, orientation of cut, original, altered.

Other Considerations:

Availability -local, seasonal, quality, quantity.

Costs  -access, procuring, conversion.

Conveyance  -distance, time, weight, volume.

Handling -safety, storage, containment

Manufacturing -conversion, processing

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Spider silk Cape from Madagascar golden Orb spider silk > Wikipedia image by Cmglee

For a material to be purposeful two broad considerations are required.

  1.          What one does to a material?
  2.         How the material responds?
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Moulding the earth > Flickr image by Julien Harneis

WHAT ONE DOES TO A MATERIAL ?

We seek an object with a perfect combination of many different qualities. Our quest is however further complicated when we require materials in very large quantities, and of equalized quality. We need materials locally, and often immediately.

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Laterite quarrying for stones at Angadipuram, India > Wikipedia image by Werner Schellmann

HOW THE MATERIAL RESPONDS ?

The material’s response is evident on three counts:

● Other Materials,

● Environment

● User.

● Other Materials: A material responds to other materials within its field. The reaction occurs both, in the presence or absence, of the environment and the user.

A material of a higher phase reacts more readily to a material of the lower phase -, e.g. solid to a liquid. Material with an ion charge reacts to a material with opposite ion charge. A material with lower latent energy becomes recipient.

The response of a material occurs more emphatically, through the surface, than anywhere else. Materials with their own surface systems respond in the same manner as their body would. However, applied surface systems with the same or of foreign materials show different reactions. The surface preparation, application method, and bonding techniques, all play their role in such reactions.

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Doughnut Shop achieving consistent finish > Wikipedia image by Neil T

● Environment: A material-object is affected by many features of the environment. The effects are local if directional (through specific orientation), or occur comprehensively. The constituents of the object also respond differently to specific effects of the environment. For such multilateral environmental demands, single, or mono material systems are inadequate. To serve such demands, separately as well as unitedly, multi-material-objects or composites are conceived. A surface material, covering the entity, forms its own environment for the entity. Here the situation can also be equated to material to environment response.

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Abandoned ship in the former Aral sea, Kazakhstan > Wikipedia image by Staecker

Effects of the environment substantially relate to the movement of earth-sun, and so have a time dimension. The time dimension makes such environmental effects to be temporary, permanent, recurrent, or variable. The effects of environment are structurally causative (capable of causing structural changes in a material), and also sensually attributive (capable of providing the sensorial experiences).

One perhaps cannot terminate the processes of nature, however, the effects of environment can be temporarily delayed or quickened and spatially diffused, or intensified, to programme the functioning of an object.

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Faux rustication > Flickr image by marctasman

● User: A user perceives a material-object in different terms like: Engineering attributes, Dimensional features, Surface properties and for Other considerations. A surface is the most proximate and tangible part of an object. A surface, is often the reason, why an object continues to survive in a particular setting.

surface-experience

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This was part of First chapter – Section 1 of my Notes on Surface Finishes Interior Design Notes

 

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PLATES, SHEETS and FILM MATERIALS -part I

Post 580 by Gautam Shah

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Sheets are surface materials with stiff to flexible body. Sheets have high proportion of surface area in comparison to volume. A sheet (mainly metal) is thinner than 6mm when compared to the counterpart, the plate. A film is a thinner formation than a sheet. Sheets, Plates and Films, all have different properties and uses. A sheet is used for packing tins, air-conditioning ducts, automobile bodies, furniture, appliances, utensils, pipes, purlins, etc. A plate is used for heavier structural entities like ships, tunnel sections, pressure storage tanks, chemical reaction vessels, reactors etc. A film is an independent entity applied as a cover or foil, formed by material deposition (gas, liquid or solid), or one integrated to a substrate (surface allying, surface ceramic formation or molecule deposition).

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Woolaroc Oklahoma Silver Navajo belt buckle of Sheet metal > Wikipedia image by Wolfgang Sauber

Metal sheets are formed chiefly by hot or cold rolling. Polymer, glass, cement, paper, gypsum sheets are extruded or cast. Foams can be classed as cast sheets. Soft sheets such as fabrics, mats etc. are formed by weaving, netting or pressing the mass of fibres. Palm leaves, leathers, skins, timbers, stones, mica, are naturally formed composite sheets.

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Extruded Sheet metal can for beverage > Wikipedia image by http://www.flickr.com/photos/marcodede/116648094/ by Marcos Andre

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Cement cast sheet (board) > Wikipedia image by Swtpc6800 en:userSwtpc6800 Michael Holley

 In modern age substantial volumes of sheets are manufactured by sheet lamination or layering, particulate forming, impregnating woven or non-woven structures, or by sandwiching various types of sheets. A sheet could have skins formed from other or same materials (that constitutes the core). Sheets formed by rolling or extrusion could be in long lengths or small width strips. Sheets, otherwise, are formed and sized to ‘standard’ sizes. The ISO standard sizes (width and length) are in multiples of 300mm. Sheet forms like fabric are manufactured and sized in multiples of 100mm. Paper is supplied in sizes (ISO standard) of series A & B (such as A0, A1, etc.). Standardization of sheet sizes encourages standardization of manufacturing plants, processes, transport, storage and wastage rationalization.

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Embossed Metal floor deck sheets > Pixabay free images by yourschantz

Plates, Sheets and Films, basically have distinctive processing methods, though some may carry common terms. Plates processing, require greater effort to shape, cut or punch through due to their thickness. Plates have characteristic flexural stiffness. So sheets like plywood and other composites behave like plates. Plates may show different stress behaviour on two faces, such as seen in rolling, bending and welding processes. Plates are assembled by welding, rivetting, forging, mechanical joining and occasionally situational fixing. Sheets are processed by methods such as cutting, punching plain bending and deformation bending. Metal sheets formed by cold-forming. Sheets are assembled by butt welding, adhesion joining, seaming, rivetting, screwing and situational fixing (e.g. dove tail joining of wood materials). Film materials in sheet forms are applied by static charging, adhesion or heat melting.

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Expanded sheet metal Lattice > Wikipedia image by Sven Teschke Budingen

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Sheet metal cabinets > Wikipedia image by sailko

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Thin Film material > Wikipedia image by Fieldsken Ken Fields

Malleable metal sheet products are manufactured mainly by stamping or pressing and drawing. Some drawn parts go through changes in body thickness (such as the kitchen pressure cooker forming). Large plastic deformation is an advantageous property for metals’ sheets. During stamping or micro drawing often there are no changes so some processes like corrugation or furniture are done on pre-coated sheets. Stiffer sheets like wood veneers and plywoods, stone (for cladding), acrylics, etc. must be sawn and in few instances shear cut. Sheets show anisotropy or directional variation of mechanical properties where the material reacts differently in different directions. Metal and composites take advantage of this characteristic while creating geometric compositions.

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Corrugated Paper boards Image attribution: Chris 73 / Wikipedia Commons

Sheets are further processed like folding, corrugation, embossing, and perforation to impart geometric qualities. Sheets are engraved or etched by mechanical, laser and plasma-based processes. Simple processes like grinding, rubbing, ironing, burnishing, flame treatments are applied on wood, paper, leather, fabrics and plastics to remove or suppress surface irregularities. Chemical treatments include Linear Plasma-based processes, nitridation, oxidation electroplating, zinc coating, chromate and phosphate treatments, coating, painting, material deposition, surface hardening, surface alloying and cementation. These alter the surfaces for polarity, wettable, electrical conductive, weldable or solderable, corrosion resistant, tarnish proof, chemical resistant, high wear, hardness and remove surface irregularities.

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Storage tanks of Plates > Wikipedia image by Alex Marshall (Clarke Energy)

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EMULSIONS

Post 577 by Gautam Shah

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Egg white, yolk and plant gums have been part of our life since prehistoric times, as thickening and emulsifying agents. Plant gums, like ‘Gum Arabic’ was used as thickening agent (and as a binder) for body paints, pottery colours and as a food emulsifier. Egg yolks and oil do not mix well but slowly whisking it can create a non separating, stable emulsion. This was technique was also used for forming colour pastes for wall paintings. The colours mixed into an emulsion did not drip or run during application. The egg offered substrate binding properties, whereas the oil helped protect the surface.

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Churning cream to make Butter > Wikipedia image by Adam Engelhart from San Fransisco, California, USA 

An emulsion is a mixture of two or more immiscible (that would not normally mix) liquids. It contains very small particles (droplets of microscopic or ultra-microscopic size) of one liquid distributed throughout the other. Chemically, these are colloids with liquids as both phases. In an oil-in-water emulsion, such as butter or margarine, the continuous phase is water and the dispersed phase is oil. Opposite to this, the water-in-oil emulsions, the oil is in continuous phase and water is dispersed into it. Butter and margarine, are examples of water-in-oil emulsions. Mayonnaise is an oil-in-water emulsion, stabilized with lecithin obtained from egg yolk. A mix of oil and water when agitated, forms a temporary emulsion, one where liquids separate immediately. But traditionally emulsifiers like gum Arabic, egg yolk, were used to stop the coalescence of oils droplets.

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Mayonnaise whisking > Wikipedia image >source http://.flickr.com/photos/fotoosvanrobin/3277764542/ author FotoosVanRobin from Netherlands 

Milk is a common example of an oil-in-water emulsion. Cream and Butter are both material combinations with same substances, but in different proportions. A Cream is oil-in-water emulsion whereas a Butter is water-in-oil emulsion. Their tastes and textures are though very different. Emulsion products include mayonnaise, margarine, hollandaise, icing, fillings, chewing gum, confectionery items, face creams, skin lotions, make-up products, hair dressing products, dyes, tanning compounds, medical formulations, lithography inks, oil bound distempers (*OBD), and plastic or latex paints. Emulsions deliver a liquid product dispersed in a carrier liquid to reduce the cost, disperse the applied material and add body to the formulation.

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Shaving Creams consist of an emulsion of oils, soaps, or surfactants and water> Wikipedia image by Coffeeaddict

Emulsions are formed and maintained by single or combination of processes like: Addition of an emulsifier, Mechanical mixing, Thickening agents and Heat energy. Stable emulsions can be undone by nullifying the effect of the emulsifier through chemical agents, freezing or high temperature heating.

Emulsifiers: An emulsifier makes the emulsion stable. Addition of surface-active agents reduces the interfacial tension between the dispersed and the continuous phases.

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Body Creams and Lotions > Wikipedia image by Gryffindor

Mechanical mixing: Vigorous stirring with or without stirrer blades causes the dispersible phase into finer droplets to form suspension in the continuous phase.

Thickening agents: Such agents increase the viscosity of the continuous phase, which prevents the movement and coalescence of dispersed droplets. Nominally emulsions have higher viscosity then their individual ingredients. Most emulsions are shear-thinning fluids where vigorous stirring can reduce the viscosity.

Heat energy: The viscosity and interfacial tension of the dispersing phase is reduced by heating.

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Ancient manner of Butter making in Canada > Wikipedia image

Transparency and Colour of Emulsions: The size of the droplet of the dispersing phase affects the light reflection, changing its transparency and colour. Emulsions are cloudy or milky in appearance when disperse-phase is of finer droplets. If the droplets are very large, then it is closer to simple dispersion or suspension. Emulsion paints are added with thixotropic agents that lower the viscosity on stirring before application, but on storage gain high viscosity to prevent settling of pigments.

Micro-emulsions are thermodynamically stable because the dispersed phase is 0.01–0.2 µm in size. Such emulsions have a characteristic transparency as their droplet size is <25% of the wavelength of visible light. Micro emulsions are stable due to the small size of droplets and high proportion of surfactants in the formulations.

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Screen printing Binders are Acrylic emulsions > Wikipedia image

Polymeric emulsions came into commercial use post 1940s. These are prepared with water as the phase, and stabilized with surfactants (molecules that are hydrophilic (water-loving) in one phase and hydrophobic (water-hating) in the other phase). The polymeric emulsions have very high molecular weight, and so when the water phase evaporates polymers coalesce into a tough film. Plastic or Latex paints as known in USA are plastic paints with polymeric emulsion-based formulations. First acrylic emulsion based ‘binders’ were produced for leather and fabric printing, but soon began to be offered as architectural coatings. Plastic paints were formulated at a time (1940s) when solvent-based paints made with alkyd or linseed oils ruled the markets. Oil paints’ were odorous, toxic, and flammable. Early acrylic paints didn’t bond well to ‘oil painted’ surfaces. Acrylic emulsions offered non yellowing, non cracking, environmentally safe, odourless and non-flammable system.

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Acrylic Plastic paint application > Flickr image by http://www.charlesandhudson,com

Acrylic emulsion paint formulations are costly to produce in comparison to ‘oil-based’ paints, and other ‘plastic paints’ such as of Vinyl and PVA (polyvinyl acetate) systems. Interior emulsion paints have high vinyl and low acrylic contents. A paint with a high acrylic content will have much better water and stain resistance.

‘Emulsifying effects’ since prehistoric times, have now developed into science of fluid behaviour and mixing. The term emulsion has become synonymous for liquid-mix systems, and is used to designate solutions, suspensions, or gels.

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STATES of MATTER and COMPOUNDS

Post 573by Gautam Shah

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Materials have three fundamental states of matter, namely Gas, Liquid, and Solid. The state denotes the structural rigidity and resistance to changes of shape or volume. The state or phase of a matter is due to the temperature and pressure. Most substances are solid at low temperatures, liquid at medium temperatures, and gaseous at high temperatures. The state or the changeover of a phase is not always distinct. The temperature at which any given substance changes from solid to liquid is its Melting point, and the temperature at which it changes from liquid to gas is its Boiling point. In the reverse order the Gas to a Liquid transition is known as Condensation, and Liquid to Solid change as Freezing.

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Mixing Oil, Vinegar and Mustard for whipping into emulsion > Wikipedia image by jeffreyw

Solids have molecules held very close to each other, and so maintain the rigid form without any need for a container. Solids formed by slow cooling have constituent atoms, molecules, or ions packed in a regular order and are called crystalline. Solids cooling down very rapidly have no long-range order for the position of the atoms and so have amorphous structure. Solids can be broadly categorized as organic (Such as the wood, paraffin wax, naphthalene and a wide variety of polymers and plastics) versus inorganic (such as metals, alloys, minerals). Solids are formed when definite bonds exist between component atoms and molecules.

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Air entrained coffee of South India > Wikipedia image by Babithajcosta

Liquids are mostly non-compressible fluid, able to conform to the shape of its container but able to retain more or less constant volume irrespective of the pressure.

Gases are compressible fluids able to take the shape of the container by expanding (or compressing) to fill it.

Plasma is the fourth state of matter following solid, liquid, and gas. Plasma is an ionized (electrified) form of gas. It has a collection of charged gaseous particles containing nearly equal numbers of negative and positive ions. Unlike other gases, plasma may self-generate magnetic fields and electric currents, and respond strongly and collectively to electromagnetic forces.

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Plasma cutting machine Wikipedia image by Steve Brown Photography

Compounds are combination of materials in the same or different phases. Compounds can be separated by a chemical reaction. If a compound is uniform, it is called Homogeneous, and nonuniform compounds are called Heterogeneous. Homogenization is a process of distributing one substance, uniformly throughout another (Ice creams, ketch-ups, etc. are homogenized). A mixture is made from molecules of elements and compounds that are simply mixed together, without chemical bonds. Mixtures can be separated using techniques such as filtration, chromatography, evaporation and distillation.

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Salt + water solution > image attribution: Chris 73 / Wikipedia Commons

Solution: Solution is a homogeneous mixture of two or more substances. The substance present in larger quantity is usually called the solvent, and the other substance present in smaller quantity and dissolved is called the solute. The solvent can be either a liquid or a solid and the solute can be either a gas, a liquid, or a solid. Carbonated water is an example of a Gas (carbon dioxide) dissolved in a Liquid (water). Mixtures of gases, such as the atmosphere, are sometimes referred to as solutions as well. Solutions are distinct from colloids and suspensions in that the particles of the solute are of molecular size and are evenly dispersed among the molecules of the solvent. Solutions appear homogeneous under the microscope, and the solute cannot be separated by filtration. Salts, acids, and bases ionize when they are dissolved in water. Certain metals are soluble in one into another, in the liquid state and solidify with the mixture of atoms preserved. If such a mixture can solidify for different proportions of the two metals, they are said to form a Solid solution of metals.

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Compounded materials occur in following forms: (Medium in Phase)

  • Solid in Solid > Alloys
  • Solid in Liquid > suspension, solution, dispersion
  • Solid in Gas > smoke, airborne dust
  • Liquid in Solid > gel
  • Liquid in Liquid > emulsion, mixture
  • Liquid in Gas > fog, aerosols
  • Gas in Solid > solid foams
  • Gas in Liquid > froth, liquid foam, aerated soda
  • Gas in Gas > atmospheric air
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Cutting tools of Alloys > Wikipedia image by Glenn McKechnie

SOLID in SOLID  A solid solution is a solid-state solution of one or more solutes in a solvent. Solid solutions occur in nature as minerals formed under heat and pressure. It is formed when two metals are completely soluble in liquid state. Typically Brass has copper (64 percent) as the solvent atoms and zinc (36 percent) are solute atoms. Such a mixture is considered a solution (rather than a compound) when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase.

SOLID in LIQUID  Salt or Sugar get dissolved in water forming a Solution. Solution like, amalgams (mercury in silver) are uniform throughout and are homogeneous. On the other hand Sand, Rocks, and wood form heterogeneous mixture where each constituent retains its own chemical identity and properties. A suspension is a heterogeneous mixture containing solid particles that are larger than one micrometer for sedimentation. Colloids have finer suspended particles and do not settle. For suspension to occur some excipients or suspending agents or mechanical agitation is required.

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Smog at Brighton UK by Wikipedia image by Richard Rutter

SOLID in GAS: Very small particles (less than 0.002 mm) can float around in air and larger particles (greater than 0.5 mm) roll along closer to the ground. Smoke and airborne dust are solids in gas medium. The process is used to separate particles of different sizes through mechanical cyclonic effect.

LIQUID in SOLID: Gels are dispersion of molecules of a liquid within a solid. The solid is in continuous phase and liquid is a discontinuous phase. Liquid in solids combinations also manifest when excess amounts (than required for equilibrium) of solute are added to a liquid, a condition called super-saturation occurs. Supersaturated solutions are unstable, and may remain in that state for an indefinite period of time if left undisturbed. However, when solid particles are added at this stage, it encourages crystal growth. A sol is a colloidal suspension of very small solid particles in a continuous liquid medium. Sols are quite stable (often due to presence of dispersion agents) like the blood, pigmented ink, cell fluids and paints. Artificial sols may be prepared by dispersion or condensation.

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Hai dressing gel > Wikipedia image by Bangin

LIQUID in LIQUID: Liquids are miscible or immiscible and chemically they are colloids where both phases are liquids. The particle or droplet size is very large, then it is more likely dispersion or suspension, otherwise it is likely to be an emulsion or a solution.

LIQUID + GAS: Liquid in gas creates a visible mass, as the small particles of liquid have greater surface area, detracting the light. Fog is a natural phenomena considered as a low-lying cloud. Aerosols have liquids in the form of solutions, suspensions, emulsions, and semisolid preparations. Aerosols use propellants of two types: Liquefied-gases and compressed-gases.

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Aerosol cans > Wikipedia image by http://streetflies.org/stue

GAS + SOLID: A suspension of liquid droplets or fine solid particles in a gas is called an aerosol or particulate. In the atmosphere these consist of fine dust and soot particles, sea salt, biogenic and volcanogenic sulfates, nitrates, and cloud droplets. Gas entrained, solids create solid-foams, here the volume of gas is large, with thin films of liquid or solid separating the regions of gas. Solid-foams have two forms: Closed cell-foams, the gas is trapped inside pockets of solid material, and in Open-cell foams the gas pockets connect with each other. Open or continuous cell forms of pliable walls are compressible due to freedom for air to move around.

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Aerogel > Wikipedia image from NASA

 GAS + LIQUID Foams and froths are colloidal systems, where the gas form bubbles in a liquid medium. Liquid foams are made long lasting by addition or presence of a stabilizer or surfactant. Proteins (eggs, oils, gums) are used as foaming agents. Carbon dioxide dissolved in water is used in aerated drinks and firefighting systems. Foaming is not always a desirable condition such as in lubricating oils. Typically air releasing agents or conditions reduce the foaming. Aerogel is a synthetic porous ultra-light material (98.2% air) that is derived from a gel by replacing liquid with air. The result is a solid with extremely low density and low thermal conductivity. It is known as frozen smoke, solid smoke, solid air, or blue smoke.

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Liquefied Petroleum gas is a mix of Propane and Butane with a powerful odourant the Ethanol  > Wikipedia image by Krish Dulal

GAS + GAS: Gases have particles with vast separation in comparison to liquids and solids. This separation usually makes a colourless gas invisible, and offers greater scope for mixing. Mixtures of gases, such as the atmosphere, are called solutions. Gas mixtures are used in a brewery for sparging or purging, that is to remove a (harmful) gas, and for blanketing or inerting to fill up the residual volume with a benign mix. Anesthesia and diving gear have gas mixing facilities in addition to adding water vapour.

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COPPER – 2 Copper Compounds

Post 479  –by Gautam Shah

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Once distinctive properties of the pure copper nodules were known, no efforts were spared to reestablish the same results. The intention was to derive a copper material easily and locally, similar to the quality of a pure copper nodule. These search resulted in discovery of many copper-containing substances. The substances were realized while processing the raw materials and finishing copper products. It helped realize many ‘copper like’ materials, but with different properties. It was found that copper became more flexible and easy to work with when heated before hammering, a process of annealing. For example, it was known that beating or forging a copper made it little brittle, but stronger for tool making. It was known that some materials could be heated to very high temperatures, in restricted air or closed environment to extract copper metal, a process of ore smelting.

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Copper figure of a bull from the Temple of Ninhursag, Tell al-‘Ubaid, southern Iraq, around 2600 BC. app 600 mm

Egyptians used copper minerals like malachite and azurite for green and blue colouring the murals and also for lip colouring make-up or body colour. Copper Sulphate was used as a mordant in the dyeing to improve colour fastness. It was also used as a topical application for skin deceases and as biocide additive in mural colours. Copper compounds like cupric oxide were used in the ceramics for achieving blue, green or red tints in glasses, glazes and enamels. Chalcopyrite a mixture of pyrite and copper sulfide, is the most common copper ore, and it has been used to extract copper compounds besides the copper metal. Mineral chalcocite, a cuprous sulfide, was used as black powder.

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Chalcocite

Chalcanthite-cured

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Hathor, Egyptian goddess of the sky, music, dance and art, was also the patron of Sinai, the copper sourcing region for the Egyptians. She was often referred to as Lady of Malachite (the copper mineral). Copper is comparatively environment friendly material. But, historically copper ores were with natural Arsenic. The presence arsenic in copper made it a castable metal and strong enough for weapons and sharp edged tools. Osiris, an Egyptian god, often called the Great Green, is portrayed with green skin. Green malachite was a symbol of joy and the land of the blessed dead was described as the ‘field of malachite.’

Green coloured Osiris tomb of Nefertiti

The smelting process for arsenic containing copper produced poisonous fumes. Tin-bronze was a better choice as it was easier to add tin then control the amount of arsenic. But tin was comparatively rare material. Arsenic copper processing was at peak during Roman times, and its traces have been found in ice layers of Arctic regions.

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STONES -Opportunities of Intervention

Post 329 –by Gautam Shah 

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Stones have naturally variegated constitution and surfaces. These, provide with inexhaustible opportunities to work to many different forms, sizes, and finishes. The qualitative consistency of man-made materials though, poses a great challenge to multifarious nature of stone materials.

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The Opportunities of Intervention for stones are of following types:

  1. Stones alone
  2. Stones with other earth-based materials
  3. Stones with natural organic materials: such as plants
  4. Stones with man-made materials such as Ceramics, Metals, Polymers (plastics and elastomers)

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1 STONES ALONE

Stones represent, one of the largest resource of earth-based materials. We have not touched even a small fraction of its top layer of mass. Ecologically its use or disposals are manageable. Only problems with stones supply are its inconsistency of sensorial and other surface qualities, and difficult to predict structural properties. This is where man-made materials prove to be superior and reliable. Man-made materials require complex and costly processing whereas stones as a natural resource though unlimited in supplies have high costs of extraction and transportation. Man-made materials are highly custom created and so are not reused extensively, but stones have nine lives and can be used till conversion to form of a dust particle. Man-made materials are produced through multiple-processing, making them difficult to recycle or dispose off safely.

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2 STONES WITH OTHER EARTH-BASED MATERIALS

Stones combined with other earth-based materials provide many opportunities of usage. However, stones by themselves or with other earth-based materials have limited scope for combinations. These are mainly by positioning such as spreading, layering or stacking with gravity, by using electromagnetic forces or by kinetic method of tying-knotting. Few earth-based cementing materials such as mud, pozolana or plant gums are insufficient in supplies and technically inadequate. Yet use of natural materials with very small proportion of man-made of joining materials and technologies can achieve outstanding results.

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3 STONES WITH NATURAL ORGANIC MATERIALS

Use of organic materials such as plant-based resources (Jungle, Farm produce) has not been explored adequately. Primitive man started using wood in combination of stone, which has been extended to buildings. Its use is limited, as wood is a scarce resource (not easy to replenish). Other organic products require several levels of processing before qualifying their application with stones. Every single new application is worth its wait and expense.

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4 STONES WITH MAN-MADE MATERIALS

Stones have been used with man-made materials like metals etc. But most technologies involve non-mixing combinations, such as mechanical joining, adhesion fixing or coating. Stones and earth-based materials have been used in many synthesizing processes. Stones in their physical form and characteristics have been exploited, as fillers, for creation of composites. However, stones have been less frequently synthesized with man-made materials such as ceramics, metals and polymers. These are going to be the opportunities for the next generation.

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The inspiration derives from the successes achieved in combining Ceramics with Metals. Ceramics and metals individually have diverse temperature of forming. At a temperature a ceramic begins to evolve some metal either evaporate, liquidize or form oxides. A combination seemingly impossible is now being achieved, for example in electrical transmission equipments, electronic components, tools and cutting edges making. Similarly stones can be combined with many other materials.

Metal application technologies provide exciting results here. Metalizing a stone surface with metallic particulate or molecules, by plating and sputtering techniques is not farfetched. Synthetics are mainly made with organic (carbon-based) monomers in polymers but chaining. These have been used both as the matrix and fillers components in composites. And can we visualize stones, not in the role of filler, but of a matrix in composite forming.

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FILLERS and COMPOSITES

Post 169 – by Gautam Shah

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Forms of Glass fiber used as Fillers

Fillers are inevitable constituents of composites. Fillers provide body, reinforcement, and impart special properties to the new material. Fillers have many forms, such as fine particulates, staple fibre (whiskers or short fibres), filaments (long or continuous fibres), unwoven (felt) and woven fabrics, knit textiles, aggregates, and sheets. Filler materials are natural (wood, plant, hair), minerals (asbestos, sand, stones, powders), and man-made (polymers, metals, ceramics) materials.

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  • Straw, hair, coir, hemp, jute, papyrus, rice-husk etc., have been mixed with clay to form bricks. Sand, ash, and mineral dust were added to mud to reduce the plasticity for plaster work. Wood planks were glued together to form block board or plywood like construction in 15th C BC.
  • Man-made materials include: Fiberglass, quartz, Kevlar, Dyneema or carbon fibre, graphite, carbon-graphite, silicon carbide, titanium carbide, aluminium oxide, boron, coated boron, boron carbide, alumina, alumina-silica, niobium-titanium, niobium-tin, etc.

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Fillers Particles (of 10 t0 250 μm in diameter) help block the movement of dislocations in the composites and provide distinctive strength properties. Staple fibres used as fillers have high length to a diameter ratio, and are generally in their random orientations, whereas filaments are used for high performance structural applications and are prearranged (for a particular structural use) before introduction of matrix, or in certain cases a fixing compound.

Depending on the load conditions, fibre arrangements for reinforcement are random, unidirectional (aligned in a single direction), or multi-directional (oriented in two or three directions). Continuous fibres are more efficient at resisting loads than are short ones, but it is more difficult to fabricate complex shapes from materials containing continuous fibres, than from short-fibre or particle-reinforced materials.

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Ceramic-Metal composite -Electric Insulator

Particles (fillers) of one material are dispersed in another material (matrix) in many different ways. 1 -Particles are mixed in a liquid phase of the matrix, and allowed to harden to a solid phase, 2 -particles are allowed to grow in the matrix, or 3 -articles are pressed into the matrix and inter-diffusion is encouraged by mechanical working or other energy input.

Particulate fillers in ceramic matrices enhance characteristics such as electrical conductivity, thermal conductivity, thermal expansion, and hardness. Particles of Alumina, Silicon carbide and Boron nitride embedded in a polymer matrix and formed as abrading tools are used for grinding and polishing stone floors, tools etc. Carbon black (as powder) added to vulcanised rubber provides hardness and toughness for automobile tyres. The rubber is further reinforced with metal, rayon, polyester and other threads as continuous fibre filler.

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High end Ceramic composites

  • High-performance ceramic composites are strengthened with filaments that are bundled into yarns. Each yarn, strand or tow may contain thousands of filaments, each of which with a diameter of approximately 10 micrometers (0.01 millimetres).

Often components are formed that are strong in all directions, by creating a three-dimensional lattice of filler component. The filler component itself could be a composite material.

 

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Fillers affect the quality of a composite. Fillers are usually combined with ductile matrix materials, such as metals and polymers, to make them stiffer. Fillers are added to brittle-matrix materials like ceramics to increase toughness. The length-to diameter ratio of the fibre, the strength of the bond between the fibre and the matrix, and the amounts of fibre are variables that affect the mechanical properties. It is important to have a high length-to-diameter aspect ratio so that the applied load is effectively transferred from the matrix to the fibre.

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A variety of reinforcements can be used, including particles, whiskers (very fine single crystals), discontinuous fibres (short), continuous fibres, and textiles preform (made by braiding, weaving, or knitting fibres together in specified designs).

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  • Glass is the most common and inexpensive fibre and is usually use for the reinforcement of polymer matrices. Glass has a high tensile strength and fairly low density (2.5 g/cc).
  • Carbon-graphite: In advance composites, carbon fibres are the material of choice. Carbon is a very light element, with a density of about 2.3 g/cc and its stiffness is considerable higher than glass. Carbon fibres can have up to 3 times the stiffness of steel and up to 15 times the strength of construction steel. The graphitic structure is preferred to the diamond-like crystalline forms for making carbon fibre because the graphietic structure is made of densely packed hexagonal layers, stacked in a lamellar style. This structure results in mechanical and thermal properties are highly anisotropic and this gives component designers the ability to control the strength and stiffness of components by varying the orientation of the fibre.
  • Polymers: A variety of polymer materials are used as filler material for composites. The strong covalent bonds of polymers offer tailor-made properties in the form of bristles, whiskers, staple fibres, filaments, yarns or tows, spun yarns, threads, ropes, unwoven and woven fabrics, knitted compositions. Nylons, polyesters, rayon, acrylic, Kevlar and many other fibres are used for composite formation.

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  • Ceramics: Ceramic fibres made from materials such as Alumina and Silicon carbides are used in very high temperature applications, and also where environmental attacks are severe. Tungsten-boron filaments, Ceramics have poor properties in tension and shear, so most applications as reinforcement are in the particulate form.

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  • Metallic fibres: Metallic fibres have high strengths but since their density is very high they are of little use in weight critical applications. Drawing very thin metallic fibres (less than 100 microns) is also very expensive.

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Following are some of the earlier posts on related Topics

1   MATRIX and COMPOSITES

2   COMPOSITES Part – 1

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