Investigation On Preparation Of Ag-B\Au-B Target By Hot Pressing And Their Densification

Au-B film can optimize the laser radiation field and improve the conversion rate of laser to X-ray by reducing Raman scattering and Brillouin scattering in the laser radiation field. Au-B film as a key role can be used in inertial confinement fusion (ICF). Au-B film were successfully prepared by NB Meezan through magnetron sputtering. So Au-B target with high density and uniform composition is important raw material for preparing Au-B film. Because of technology security, there are few international literatures about the preparation of Au-B target. Therefore, the study of Au-B target is significant for the new energy development.The difference, melting point(Au:1064℃,B:2030℃) and density (Au:19.3 g/cm3 B:2.34 g/cm3) between Au and B, is a huge gap. In the high temperature liquid phase conditions, the phase of B will float and gater. It is very hard to form alloys or metal compounds between Au and B.So Au-B target prepared by melting dispersion with good uniformity and high density is very hard. In this paper, hot-pressing method was used to prepare Au-B target, and using Ag instead of Au was a good way to cut cost of experiments. Ag and Au have similar physical and chemical properties, and Ag-B and Au-B binary phase diagrams also have a high level of similarity. This paper studied the preparation technic of Ag-B target and densification process and prepare the Au-B target.Firstly, the Ag-B target was prepared by hot pressing using Ag and B powder in mass ratio of 93:7. The density of target was measured by Archimedes method; fracture morphology of Ag-B target was observed by SEM; the phase suructure was measured by X-ray diffraction; DSC curves were analyzed by differential scanning calorimeter Porosity of Ag-B target was measured by mercury intrusion porosimeter. The effects of hot pressing conditions including temperature, pressure and preserving time on relative density, microstructure, grain size and porosity were investigated and densification process of Ag-B target was studied. And serial conclusions were drawn as following.(1) The Ag-B mixturepowder of uniform distribution was prepared after ball-milling and sieving process. DSC curves show that no Ag-B alloy or AgB compound was found under temperature up to 1000℃, but the fusion latent heat of Ag-B powder decreased because of B.(2) With temperature of 450℃ up to 750 ℃, the relative density increased from 81.8%to 95.3%; however when temperature increases from 750℃ to 800 ℃, the relative density decreased from 95.3% to 89.2%, there existed a phenomenon of "anti-densification"; with increasing of preserving time and pressure, the relative density of Ag-B target increased. Comparing with pressure, temperature and preserving time were key factors of Ag-B densification process; at temperature of 750 ℃, preserving time of 120min and pressure of 28MPa, the relative density of 95.32%of Ag-B target is achieved.(3)From 450℃ to 750℃, grain size of Ag-B target increased with the increasing of sintering temperature and preserving time; at temperature of 800℃, the grain size decreased to 16.8nm, there existed a phenomenon of grain "fragmentation". Pressure can restrain the grain growth. Grain growth had both positive and negative effects on the densification process.(4) With temperature from 450℃ to 650℃, the porosity of isolate pore descread from 7.30% to 2.03%. From 750℃ to 800℃, the porosity of isolate pore increased from 3.11% to 9.75%. The phenomenon of "anti-densification" is contributed to the combination and growth of the channel pores and the increasement of volume content of the isolated. With temperature increasing, the porosity of channel pore decreased, at temperature of 800℃, the porosity of channel pore was 1.08%. With preserving time increasing, the porosity of channel pore decreased, the porosity of isolate pore increased to 10.3%at preserving time of 60min and then decreased to 3.11% at 120min. This indicate that at 60min decification of Ag-B target getted into relatively stable stage.(5) Densification process of Ag-B targets can be divided into three stages:rapid densification stage, slow densification stage, and relatively stable stage.Finally, The Au-B mixture powder of uniform distribution was prepared by ball-milling and sieving process and the relative density of Au-B target achieved 95.55% at temperature of 850℃, pressure of 28 MPa, and preserving time of 120 min, under the guidance of Ag-B hot-pressing process. Study about Au-B target properties was carried on by method listed below:Archimedes method; SEM; XRD;Metalloscope. The results indicated that Phase B had uniform distribution of Au-B target,no Au-B atloy or AuB compound was found in the hot-pressing process and grain size is 44.3nm at temperature of 850℃.