Ceramic Cement Research Articles

Overview — clay mineral applications

The applications of the clay minerals in the various process industries engineering, petroleum discovery, recovery and refining, and others, are closely related to their structure and composition. Important characteristics relating to applications of clay minerals are particle size, surface chemistry, particle shape, surface area, and other physical and chemical properties specific to a particular application such as viscosity; color; plasticity; green, dry and fired strength; absorption and adsorption; abrasion; and others. The discussion of the applications of clay materials is organized as follows: kaolins; smectites; palygorskite (attapulgite) and sepiolite; and miscellaneous. The largest volume applications in each category are discussed in general, leaving the more specific details to be covered in the papers in this symposium that cover a particular application. The major uses of kaolins are in the paper, ceramic, paint, plastic, rubber, and cracking catalyst industries. The major uses of smectites are in drilling fluids; as a bond for foundry sands and iron ore pellets; as a sealant in many engineering applications; and as absorbents for pet litter, agriculture chemicals, and oil and water. Palygorskite and sepiolite are used as absorbents in pet litter, agricultural chemicals, water and oil sorption, and as the suspending medium in many applications such as saltwater drilling fluids, paints, pharmaceuticals, and others. Miscellaneous applications include the uses of shales and other clay materials in structural ceramic products, cement, lightweight aggregate, asphalt emulsions, and other important uses. According to U.S. Bureau of Mines figures, approximately 50 million tons of clay materials are used annually with a total value of $1.1 billion. This high usage and value certainly attests to the importance of clays to the economy and welfare of the United States and to industry. Clay materials perform a function in most every application and are not just an inert component in the formulation. The abundance and availability of the clay materials and their relatively low cost guarantees their continued utilization in the future. Research and development will find new applications for clays in the future which has been the pattern in the past.

Traditional construction in the architecture of Gaudi

In order to create the original and beautiful architectural forms which made Gaudi famous, the architect solely employed traditional materials (brick, stone, glazed ceramic lime and quick-drying cement for mortar, plaster, etc.) and techniques, or their derivations. The author reviews these Gaudinian construction techniques, from the simple column to hyperbolic paraboloids, the square column, the false arch, festoon arches or catenary profiles, spiral arches. Catalan vaults (brick vault of one, two or more ceilings of brick laid flat), ribbed vaulting, cupolas, penditives, partition arches, etc.

Experiments in Compton scatter imaging of materials with wide-ranging densities using a low-activity gamma source

A low-activity Compton scatter imaging device employing a 1.4 mCi 133Ba gamma source has been used to detect 6 mm diameter voids in materials of very different densities and structural types. Two-dimensional histogram images have been obtained of sections of steel, steel covered with simulated marine growth, medium-density polyethylene and an inorganic ceramic cement, all containing 6 mm diameter simulated voids. The image contrast is large enough to differentiate these voids from statistical noise in runs of reasonable duration for practical source intensities, therefore making the technique promising for a variety of applications to small-component inspection. The images obtained are corrected for the effects of photon attenuation and in one case the image has been compared with a non-corrected one.

Ceramic cements and ceramic concretes of quartz-chamotte composition

On the basis of quartz sand and scrap chamotte refractories (28.0% Al2O3, 67.0% SiO2) we obtained highly concentrated bonding suspensions (cement slips) of mixed composition enabling us to form castings with a porosity of 12.2–18.3% characterized by bending strengths of up to 4.5 MPa and compressive strengths of up to 32.4 MPa.

Nerva Nuclear Reactor Instrumentation

The environmental conditions existing at many of the points at which measurements are required in the ground testing of the NERVA reactors are beyond the capabilities of commercially available transducers. The measurement of the temperatures inside the reactor core was accomplished by pushing thermocouples to the high temperature limit of this sensing means. Tungsten and tungsten alloys have shown the capability of surviving a reactor test at these temperatures in the presence of carbon and high pressure hydrogen. Vibration and pressure transducers have been developed which can operate in an ambient of cryogenic hydrogen with internal temperatures of over 500°F degrees generated by gamma and neutron heating. The measurement of strain with gages subjected alternately to cryogenic and maximum high temperatures for this type sensor was accomplished with weldable gages. The problem of bringing electrical signals from the sensors in the severe environments to the data recording system was solved by using magnesium oxide insulated conductors in stainless steel sheaths. In future testing, measurements are desired at locations in the core where temperatures and radiation levels are even higher than those which have already been experienced. Development continues on thermocouples to measure 5000°R, on vibration and acoustic pressure transducers to operate at radiation heating levels of four watts per gram and on methods of connecting magnesium oxide insulated sheathed cable to strain gages bonded with ceramic cements.

Resistance strain gauges for the measurement of steady strains at temperatures above 650°C

The paper considers the problem of obtaining steady strain data using electrical resistance strain gauges at temperatures above 650°C, in the presence of moderate temperature gradients, from turbojet components operating in oxidizing environments. The characteristics of forty-six metal and alloy systems are briefly outlined and the properties of platinum, and alloys of face centred cubic platinum metals and metals in the VIa group of the periodic table of elements are discussed in detail. The behaviour of colloidal sols, acid and alkali bonded ceramic cements and flame-sprayed oxides at high temperatures is considered and their effect on the short and long term stability and strain sensitivity of strain gauges presented. Only a limited number of pure oxides possessed an adequately high electrical resistivity at the higher temperatures for use as strain gauge bonding media. Such oxides, when flame-sprayed on to suitably prepared surfaces, developed a bond of sufficient shear strength to transfer the applied strain in a consistent and repeatable manner to the gauge filament. The porosity was low enough to offer some degree of oxidation protection to the strain sensitive grid. The temperature coefficient of resistance, drift rate and strain sensitivity of flat grid, dual-element gauges bonded in this manner to Nimonic specimens are shown and it is concluded that grids of this type, wound from platinum and a commercially available platinum-tungsten alloy, would permit the detection of steady strains within an accuracy of about ±0.5 ton/in2 over the temperature range 600—850°C and within ±1.0 ton/in2 over the approximate range 600—950°C from Nimonic specimens, provided the mean gauge temperature could be determined. Methods of determining this temperature in the presence of moderate temperature gradients along the longitudinal axis of the gauge are discussed and some field data are presented. Drift rates equivalent to less than 0.1 ton/in2/h were noted. It is thought that a coil wound gauge would offer improved performance over a flat grid gauge for temperature gradients across the element, but the problem of providing a suitable former has not been resolved satisfactorily.

Ceramic cements to withstand temperatures of up to 2900�

Ceramic cements to withstand temperatures of up to 2900�

Dental materials 1956–1958: A review

The author reviews 65 papers that ap­ peared in the literature from 1956 through 1958. The subjects covered in­ clude: biological effectsof dental mate­ rials; metallic materials, including amal­ gam, gallium-base alloys, gold-base alloys and chromium-cobalt alloys; ceramic materials, including porcelain, cements and investments; organic materials, in­ cluding denture base resins, relining resins, plastic teeth, direct filling resins and elastic impression materials; and the mechanical properties of enamel and dentin. Recent literature reveals a trend toward testing new dental materials bio­ logically before subjecting them to clin­ ical use.

EFFECT OF MOISTURE UPON ELECTRICAL RESISTANCE OF EMBEDDING CEMENTS*

ABSTRACTFor insulating electrical resistors from the casing of household appliances, etc., ceramic cements when properly applied are superior to other materials. If not sufficiently vitrified after application, however, they absorb moisture, thus tending to lower their resistance sufficiently to permit users of the appliances to experience electrical shocks. The necessary firing temperature varies widely with different cements. Some are satisfactory when cured by the heat of the embedded resistor alone while others are not. The hygroscopic properties are shown to be markedly increased by the presence in the cement of bentonite, borax, mica dust, or glass cullet. The borax also reduces the ultimate resistance objectionably at higher temperatures.The apparatus used for testing is described in detail.