Kageeporn Wongpreedee

The Effects of Depositing Sn-Ag-Cu-S Systems at Different Temperatures on Silver Substrates

Niello bars contain Lead which prohibits by laws and danger to environment. This research was to study the effects of temperatures which a black amalgam of lead-free niello bar alloys was filled in carved grooves of 95wt%Ag-5wt%Cu and 99.99wt%Ag substrates at 400C, 500C, 600C and 700C. Three compositions of lead-free niello bar alloys were selected in this research. The characterizations of microstructure, interface layers, and porosities of lead-free niello bar alloys after applying were reported. The results showed that all three compositions contain six compounds of CuAgS, Ag, Cu2S, Sn2S3, SnS and Cu4SnS4. After applying lead-free niello bar alloys on the substrates, it showed that composition #2 on the 95wt%Ag-5wt%Cu substrates was matched to the best condition of temperature at 600C giving lowest porosities.

Kinetic transformation of nanofilamentary au Metal-Metal Composites

Recovery and recrystallization of Au wire can degrade strength and alter conductivity properties during exposure to elevated temperature. Au Deformation Processed Metal-Metal Composites (Au DMMC’s) are being developed for electronic applications requiring high conductivity and high strength. This paper discusses the relationships between microstructure, strength, and resistivity of Au DMMC’s. Au DMMC samples were prepared by a powder metallurgy technique and processed into wire down to diameters as low as 120μm. The extensive deformation reshaped the initially equi-axed powder into filaments that are 30 to 100 nm in diameter and 16 to 180 mm in length, which confers high strength. The high conductivity can be explained by electrons flowing parallel to the filamentary microstructure aligned with the wire axis. Au DMMC’s were found to have good thermal stability compared to conventional cold-worked Au interconnection wires. Although these composites will revert to solid solutions if exposed to high temperatures for prolonged times, their relative stability is sufficient to allow them to maintain their two-phase microstructure during the anticipated lifetime temperature profiles of many products.

Lost Wax Casting Conditions with Tourmaline In Situ

The technique of stone-in-place casting has been established in jewelry production for three decades. However, the process is not widely used since it is limited to precious stones with high hardness and high stability at high temperature. This experiment tested tourmaline, which is a semi-precious gemstone having less hardness and less stability compared with precious stones. The objective was to achieve the conditions of a lost-wax casting process with tourmaline placed in waxes in the casting process. The experiment was divided into two parts. The first part was to understand the tolerance of tourmaline under the heating conditions. Natural tourmaline stones were investigated and compared inclusions tested at a temperature of 700°C. Tourmaline with ion-implantation was also heated to 700°C for comparison. The second part was to test tourmaline in-place casting with tree conditions of flask casting at 550°C, 625°C, and 700°C. The results showed that stones were able to tolerate as much as at 700°C. The inclusion growth of ion-implantation under heating to 700°C also observed the growth of inclusion in the same way as untreated tourmaline. The casting condition at 550°C showed better results. The highest probability of stones breaking after casting occurred in bezel settings.

The Development of Bi-Ag Sandwich Sheets for Fire Assay Applications

A Fire assay is method to verify the fineness of gold with use lead in its process. In this research, Bi-Ag sandwich sheets for a lead-free fire assay method were developed. Bi-Ag sandwich sheets were produced by a hot-dipping method at temperature 300 °C and 400 °C. Samples were characterized the microstructure by SEM along the process. A fire assay method was used to verify and correlate the results of gold fineness to various kinds of wrapping sheets which are Bi-Ag sandwich sheets and lead. The Bi-Ag sandwich sheets shows the layer of 14-20 µm at 300 °C and 8.5-10.5 µm at 400 °C. After cupellation process, the metal beads were observed by SEM and mapping techniques to analyze the remained copper. XRF characterization was confirmed the results of compositions showing an increasing amount of copper as increasing temperature dipping on Bi-Ag sandwich of 0 wt%, 1.58 wt% and 1.34 wt% at S1, S2 and S3, respectively. Higher amounts of copper left on bead buttons consisted with the accuracy of fire assay results which were S1, S2 and S3 obtaining 99.99 wt%, 99.87 wt% and 100 wt% of gold, respectively.

Interface Layers of Ag-Al Fusing Metals by Casting Processes

The materials of fusing metals commercially used in the jewelry niche marketing is seen as precious metals. An innovation of fusing metals searched for new materials to differentiate from the markets for mass production. In this research, it studied the bonding processes of silver and aluminium metals by casting processes for mass productions. The studies had been varied parameters on the types of aluminium and process temperature controls. This research had used two types of aluminium which were pure aluminium 99.99% and aluminum 5083 alloys bonding with pure silver 99.99%. The temperatures had been specified for two factors including casting temperature at X1, X2 and flasking temperature at Y1, Y2. From the results, it was found that the casting temperature at 730°C and the flasking temperature at 230 °C of pure silver-aluminum 5083 alloys bonding had the thinnest average thickness of interface at 427.29 μm. The microstructure of pure silver-aluminum 5083 alloy bonding was revealed eutectic-like structures at the interfaces. The EDS analysis showed the results of compounds at interface layers of Ag sides giving Ag2Al intermetallics on pure silver-aluminum 5083 alloy bonding unlike pure silver-pure aluminium bonding giving Ag3Al intermetallics.