By adopting the positive defocusing amount,the effect of fiber laser-metal inert-gas welding( MIG) hybrid welding parameters on the weld morphology of 304 stainless steel,mainly including wire feeding speed,arc length,laser power,the distance between laser and MIG arc,welding direction and butt joint,was studied through many welding experiments. Results indicate that the good welding effects can be obtained by matching proper wire feeding speed and arc length when the extension length is 15mm and the distance between laser and MIG is 2mm. The results also show that small diameter wire will help to make the narrow weld width and low weld reinforcement,end tab will solve the problem of bad welding morphology at welding initial position. A conclusion is drawn that good welding quality of 304 stainless steel can be achieved when the proper welding procedure of laser-MIG hybrid welding is adopted.

The powder feeder head is the key component which affects the quality of laser cladding. A new-type lateral powder injection nozzle with cooling module,guiding light and inclinometer is introduced in this paper. It can implement the effect of high-precision and stable cladding for a long time which will markedly improve the cladding productivity and the powder using efficiency. Compared with the traditional feeding nozzle,the feasibility of the new device is tested.

Directly starting from lactic acid (LA) and polyethylene glycol (PEG, Mn=1000), with mLA/mPEG = 9, a green polymer, biodegradable material polylactic acid-polyethylene glycol (PLEG) was synthesized via melt copolycondensation at 165℃ and under 70Pa for 10h. Using the nontoxic catalysts (mCat/mLA=0.005), such as zinc lactate, calcium lactate and taurine, the synthesis of PLEG was investigated. The direct melt polycondensation for the synthesis of PLEG catalyzed by the nontoxic catalysts is practicable, and its relative molecular weight can meet the requirement of drug delivery carrier. The new method is especially beneficial to the safe application of PLEG in medical field.

以乙醇酸为原料,在催化剂氯化亚锡质量分数0.5%,反应温度165℃,反应压力70 Pa,反应时间10 h的条件下进行熔融聚合,直接合成了生物降解的医用纤维材料聚乙醇酸(PGA),用IR,DsC,X射线衍射等进行了表征,并与乙交酯开环聚合二步法合成PGA进行了比较.直接熔融聚合PGA的结晶度和微晶尺寸高于二步法,其合成工艺流程短、简单易行、耗时少,有利于降低医用纤维材料PGA的开发成本.