The conductive oxide impact on Aluminum alloy of YAG pulse laser welding
Few articles are reported about conductive oxide impacting on Aluminum alloy of Nd: YAG pulse laser welding at present. Therefore, this paper takes one typical Aluminum alloy as laser welding samples. Through SEM (scanning electron microscope) microscopic analysis and contrast, the comparative study between on with and without surface conductive oxidation impacting on laser welding samples have been conducted. The results show that the laser welding process parameters are needed, but the conductive oxide will bring no destructive effect on laser welding. Accordingly for this reason, it is thought that the conductive oxide will not bring substantial effect on Aluminum alloy of Nd: YAG pulse laser welding.
APPLICATION AND DEVELOPMENT OF LASER-PROCESSING TECHNOLOGY
The applied fields of laser-processing technology is introduced in broad outline.Some typical applications are discussed,such as laser drilling and cutting,laser welding,changed function fechnology on surface,laser carving,milling and texturing,laser deposit,quich-formed technology,laser marking and mark carving.Meanwhile,the present situation of the laser processing industry at home and abroad is introduced.
Development of an Analytical Method for Explosive Residues in Soil
Abstract : An analytical method was developed to determine the concentrations of HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT in soil. The method involves extracting a 2-g sample with 50 mL of acetonitrile using an ultrasonic bath procedure for 18 hr. A 10-mL portion of the extract is diluted with 10 mL of water, filtered through a 0.45-micrometer Millex SR filter, and analyzed by RP-HPLC using a fixed 254-nm UV detector. Separations were obtained on an LC-18 column eluted with 50:50 water-methanol. Retention times were 2.55, 3.82, 5.16, 6.25, 7.04, 8.47 and 10.15 min for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT, respectively. Confirmation of analyte identities is recommended by RP-HPLC on an LC-CN column using 50:50 water-methanol. Kinetic studies using naturally contaminated soil indicated that equilibrium was achieved within 24 hr for the majority of soils and analytes studied. The method provides linear calibration curves over a wide range of concentrations. Reporting limits were conservatively estimated at 1.6, 1.8, 1.5, 0.5, 5.5, 0.8 and 0.8 micro grams/g for HMX, RDX, TNB, DNB, Tetryl, TNT and 2,4-DNT. Analytical precision was estimated at + or - 0.44, 0.51, 0.43, 0.13, 1.24, 0.27 and 0.20 micro grams/g, respectively, in the range of homogeneous variance near the detection limits. At higher concentrations the relative standard deviation was constant at 2% for HMX, RDX, DNB and TNB, 3% for TNT and 2,4-DNT, and 6% for Tetryl.