The effectiveness of low-emissivity coating on a polymer film
This work describes the effectiveness of low-emissivity (low-E) coating on the polymer film with TiO2/ZnO:Ga/Ag/ZnO:Ga/TiO2 structure and the results of heat monitoring. The characteristics of the coating which determine the reduction of heat loss by the low-E coating are given. Also the results of efficiency calculations for low-E coating are presented, such as resistance to heat transfer, heat savings when installing low-E coating on the polymer film, etc. The heat monitoring is carried out to determine the effectiveness of low-E coating. The results of heat monitoring illustrate the effectiveness of low-E coating.
The base layer effect on the d.c. conductivity and structure of direct current magnetron sputtered thin films of silver
Abstract Many low-emissivity solar-control optical coatings on glass consist of a repeating dielectric–silver–dielectric thin film period. We have investigated the effect of structure of the dielectric base layer on the conductivity, structure, and thermal stability of contiguous silver films up to 500 A thick. All individual layers were deposited by d.c.-magnetron cathode sputtering. Specifically, a detailed comparison of thin films of amorphous zinc stannate with crystalline zinc oxide showed that the latter improves the conductivity of 50–100 A and thicker silver layers. X-Ray diffraction analysis showed that zinc oxide with a preferred basal plane orientation results in the preferred growth of the Ag(111) planes parallel to the float glass substrate. Transmission electron microscopy results support the above observation. The transmission electron microscopy results also indicate that the silver–dielectric interface is of similar quality in both cases, thus eliminating the role of the interface as a major cause of the above difference. Our data on the structure and electrical properties of heat-treated samples suggest that the preferential growth of the silver layer results in its higher thermal stability.
Hygroscopic Expansion of some Casting Investments
CREDIT is generally given to Taggart1 for introducing the cast gold inlay to the dental profession. Although he realized that gold shrinks when cooled from molten state to solid state of room temperature, the investment available to him did not supply sufficient compensation. In 1910, Van Horn2 published a paper dealing with a method by which he obtained the compensation by means of wax expansion. The next major research in connection with this problem was the work of Coleman3 at the National Bureau of Standards. He determined the gold shrinkage to be 1.25 per cent and presented a casting technic with compensation values of quantitative nature. The total compensation for the gold shrinkage was obtained by the combination of the setting and thermal expansion of the mold. This procedure is the general practice followed at the present time for compensation. There are some disadvantages to this method. Skinner has indicated the difficulty of obtaining smooth castings and the improper compensation for the casting shrinkage.4 It has been found by Hollenback5 and Scheu6a that castings made at a high temperature are rougher than those made at a low temperature (450° C.), depending upon the great difference in thermal expansion between plaster of Paris and silica, which causes a poor union of the fine particles. This may also result in friability and there may be some warpage due to the differential expansion. A method which provides sufficient compensation at a low mold temperature is the hygroscopic casting technic.b Wilson7 showed that certain plasters expand as much as 0.0044 inch to the inch by taking up moisture from the air. With this information at hand, Scheula, b tested some commercial investment to determine what results the addition of moisture would have. He found6b: (1) All of the casting investments that were tested expanded. (2) The thicker the mix, the greater the expansion. (3) A mix with hot water expanded more than one with cold water. (4) The time at which the mix is placed in the water is of great importance. It was found that if the mix is placed in the water early, it would not expand so much as when placed in a little later. It was also found that if the mix was placed in the water after a certain time, it could not expand to the maximal amount. (5) The temperature of the water in which the mix is placed is important, for two reasons; (a) the temperature of the water controls slightly the expansion of the investment, and (b) water at a temperature of 1000 F. slightly softens the wax pattern so that the fine margins are not marred while expansion is taking place. The mix should remain in the water at least 20 minutes to obtain the full expansion, after which time no further expansion is obtained.