基于有限元的脉冲激光辐照材料温度场研究

在激光超声检测过程中,为了合理加载脉冲激光的能量,以便获得幅值较大的超声波信号,同时避免脉冲激光造成材料的损伤,需要对脉冲激光辐照材料的温升进行数值计算。依据有限元理论,建立脉冲激光辐照材料的有限元模型,结合导热微分方程,将脉冲激光以热流密度的形式加载于材料表面,分析材料表层受激光辐照时的温度场,讨论有限元热分析时网格尺寸的选取对分析结果的影响。给出了材料表层受脉冲激光辐照时温度场的计算方法和网格尺寸的选择依据,并利用温度场的理论解析结果和应力场分析结果分别验证了温度场有限元计算方法的正确性和有效性。     

脉冲激光二极管端面泵浦Nd;YAG棒时变温度场

在脉冲激光二极管(LD)泵浦的激光晶体中存在升降温的时变过程,为解决脉冲LD端面泵浦的激光晶体产生的热效应问题,基于热传导方程,采用特征函数法和常数变异法得到了脉冲超高斯光束端面泵浦Nd∶YAG棒的时变温度场的一般解析表达式.同时定量分析了单脉冲和重复脉冲端面泵浦Nd∶YAG棒的时变温度规律.研究结果表明,重复脉冲端面...     

A Novel Buffering Technique for Aqueous Processing of Zinc Oxide Nanostructures and Interfaces,and Corresponding Improvement of Electrodeposited ZnO‐Cu2O Photovoltaics

A novel buffering method is presented to improve the stability of zinc oxide processed in aqueous solutions. By buffering the aqueous solution with a suitable quantity of sacrificial zinc species, the dissolution of functional zinc oxide structures and the formation of unwanted impurities can be prevented. The method is demonstrated for ZnO films and nanowires processed in aqueous solutions used for the selective etching of mesoporous anodic alumina templates and the electrochemical deposition of Cu₂O. In both cases, improved ZnO stability is observed with the buffering method. ZnO‐Cu₂O heterojunction solar cells (bilayer and nanowire cells) synthesized using both traditional and buffered deposition methods are characterized by impedance spectroscopy and solar simulation measurements. Buffering the Cu₂O deposition solution is found to reduce unwanted recombination at the heterojunction and improve the photovoltaic performance.     

595nm脉冲染料激光非损伤嫩肤的动物实验研究

评估脉冲染料激光非损伤嫩肤后皮肤的组织学变化及真皮胶原蛋白含量的变化,初步探讨脉冲染料激光非损伤 嫩肤的机理,为有效的临床治疗提供借鉴。实验采用590nm的脉冲染料激光。24只昆明小鼠随机分为4组,1组对照组,3组 实验组。三种能量的激光各照射5次,间隔3天,光斑有10％的重叠。照射后进行常规的病理学切片,HE和VG染色,目镜 测微尺测量真皮胶原纤维的厚度,SPSS进行数据分析。激光照射后短期内可以观察到轻微的炎症反应,长期观察发现小鼠皮 肤表皮和真皮厚度明显增加,真皮胶原纤维排列整齐有序,成纤维细胞数量增加,没有观察到水疱和红斑等副反应。8 J／cm2、 10 J／cm2和12 J／cm2组真皮胶原纤维的厚度分别比对照组高29％(p<0.05)、35％(p<0.05)和38％(p<0.05),但它们之间 没有统计学上的显著差异。证明595nm的脉冲染料激光非损伤嫩肤是一种安全有效的的嫩肤方法。     

10.6 μm脉冲激光对多晶硅探测器干扰损伤实验

用10.6 μm脉冲CO2激光辐照多晶硅光电探测器,进行了干扰与损伤阈值实验研究,得到了对多晶硅探测器的干扰、损伤阈值;分析了不同干扰能量的干扰效果,研究了干扰损伤机理,依据受干扰程度对干扰等级进行了划分;通过干扰激光能量与干扰光斑面积的关系,重度饱和后探测器随时间恢复情况,探讨了各干扰等级下10.6 μm脉冲激光对红外成像系统的干扰效果。     

Low‐Temperature Processable High‐Performance Electrochemically Deposited p‐Type Cuprous Oxides Achieved by Incorporating a Small Amount of Antimony

The development of an electrochemically robust method for the low‐temperature deposition of cuprous oxide (Cu₂O) thin films with reliable and conductive p‐type characteristics could yield breakthroughs in earth abundant and ecofriendly all oxide‐based photoelectronic devices. The incorporation of the group‐V element antimony (Sb) in the solution‐based electrodeposition process has been investigated. A small amount of Sb (1.2 at%) in the Cu₂O resulted in rapid nucleation and coalescence at the initial stage of electrochemical reaction, and finally made the surface morphology smooth in 2D. The growth behavior changed due to Sb addition and produced a strong diffraction intensity, single‐domain‐like diffraction patterns, and low angle tilt boundaries in the Cu₂O:Sb film, implying extremely improved crystallinity. As a result, these films exhibited extraordinary optical transmittance and band‐to‐band photoluminescence emission as well as higher electrical conductivity. The Cu/Cu₂O:Sb Schottky diode showed good rectifying characteristics and more sensible photoresponsibility.     

(Bi,Pb)2Sr2CaCu2O8薄膜的激光感生电压效应

采用紫外脉冲激光沉积技术和高低温沉积工艺,在LaAlO3(100)平衬底及倾斜衬底上成功制备了c轴取向的(Bi,Pb)2Sr2CaCu2O8[(Bi,Pb)-2212]薄膜;研究了在倾斜LaAlO3(100)单晶衬底上生长的(Bi,Pb)-2212薄膜激光感生热电电压信号与沉积条件及入射激光能量的关系。为避免(Bi,Pb)-2212薄膜被激光剥蚀或蒸发,还初步研究了MgO保护层对(Bi,Pb)-2212薄膜激光感生电压信号的作用,结果表明MgO层能够显著增强激光感生热电电压效应。     

铝合金连续-脉冲激光焊接工艺对比实验研究

为了研究5052铝合金激光焊接工艺,采用脉冲激光和连续激光分别对1.5mm厚的5052铝合金板进行了焊接,并对工艺参量进行了优化。通过对两种不同类型激光焊接试样的焊缝形貌的对比、微观组织的分析、抗拉强度和显微硬度测试,可知脉冲激光焊接对焊接接头气孔的控制更为理想,使得脉冲激光焊接所获得的焊接质量更加优异,与连续激光焊接相比,其接头的抗拉强度增加了10%。结果表明,脉冲激光焊接和连续激光焊接均可以使焊接试样得到较为理想的焊缝形貌和较高的抗拉强度。     

Pure CuBi2O4 Photoelectrodes with Increased Stability by Rapid Thermal Processing of Bi2O3/CuO Grown by Pulsed Laser Deposition

A new method for enhancing the charge separation and photo‐electrochemical stability of CuBi₂O₄ photoelectrodes by sequentially depositing Bi₂O₃ and CuO layers on fluorine‐doped tin oxide substrates with pulsed laser deposition (PLD), followed by rapid thermal processing (RTP), resulting in phase‐pure, highly crystalline films after 10 min at 650 °C, is reported. Conventional furnace annealing of similar films for 72 h at 500 °C do not result in phase‐pure CuBi₂O₄. The combined PLD and RTP approach allow excellent control of the Bi:Cu stoichiometry and results in photoelectrodes with superior electronic properties compared to photoelectrodes fabricated through spray pyrolysis. The low photocurrents of the CuBi₂O₄ photocathodes fabricated through PLD/RTP in this study are primarily attributed to their low specific surface area, lack of CuO impurities, and limited, slow charge transport in the undoped films. Bare (without protection layers) CuBi₂O₄ photoelectrodes made with PLD/RTP shows a photocurrent decrease of only 26% after 5 h, which represents the highest stability reported to date for this material. The PLD/RTP fabrication approach offers new possibilities of fabricating complex metal oxides photoelectrodes with a high degree of crystallinity and good electronic properties at higher temperatures than the thermal stability of glass‐based transparent conductive substrates would allow.     

（英）沉积温度对脉冲激光沉积法在YSZ (100)衬底上生长的Mn1.56Co0.96Ni0.48O4尖晶石薄膜结构、电学和磁学性能的影响

在YSZ（100）衬底上,采用脉冲激光沉积法在500℃至700℃的不同沉积温度下生长出尖晶石结构的Mn_1.56Co_0.96Ni_0.48O₄（MCNO）薄膜.由于沉积温度是制备高质量薄膜的重要因素,本文研究了MCNO薄膜结构、电学和磁学性能随沉积温度的变化.通过对X射线衍射图和原子力显微镜图像的分析,发现MCNO薄膜的结晶与沉积温度有很大关系.随着沉积温度的升高,MCNO薄膜的电阻率呈V型变化,其导电过程可以用小极化子跳跃机理来描述.同时,随温度变化的磁化曲线表明所有样品都显示出从铁磁性到顺磁性的转变,且沉积温度为600℃的MCNO薄膜具有216 K的高居里温度.以上研究结果表明,在600℃沉积的MCNO薄膜具有适用于热敏电阻器件和多功能异质结所需的良好性能.