不同分散剂对纳米铁粉分散性能的影响

通过对直流氢电弧蒸发法制备的纳米铁粉Zeta电位的测量,选用非离子型和阴离子型2类分散剂,分别研究了油酸、聚乙烯吡咯烷酮（PVP）和十二烷基苯磺酸钠（SDBS）3种分散剂对纳米铁粉分散性能的影响.结果表明：超声时间、分散剂加入量及pH值对分散效果影响显著,随着超声时间和表面活性剂加入浓度的提高,粉体分散效果呈先增大后减小的趋势;PVP和油酸对纳米铁粉的分散效果较好,分散剂分散效果从高到低顺序依次为：PVP＞油酸＞SDBS;推荐最佳分散工艺：无水乙醇作为溶剂,超声功率560 W,超声时间15 min,pH等于10,PVP加入量4%.     

超声波对镀镍金刚石性能的影响

本文研究了超声波对镀镍金刚石性能的影响。结果表明：超声波使金刚石表面的镍镀层更加均匀和致密，并有增加镀速的作用。超声波可提高镀镍金刚石的抗压强度、氧化温度和热稳定性，并随超声波频率的增加，金刚石性能有提高的趋势。     

分散剂对陶瓷釉料中纳米氧化锌分散性的影响

采用沉降实验、粒度分析等手段对含纳米ZnO的水溶液、釉料和陶瓷成品进行了表征.研究了纳米Zno在水和釉料中的分散行为、纳米ZnO对陶瓷成品性能的影响.结果表明,纳米ZnO在水中最佳分散条件为0.8%(质量分数,下同)混合表面活性剂、2.0%纳米ZnO、pH 9;纳米znO在釉料中最佳分散条件为0.8%混合表面活性剂、4.0%纳米ZnO、pH9.陶瓷成品光泽度提高7.14%,烧成温度降低约15℃.     

分散剂对复合刷镀Ni-纳米SiC沉积行为影响的研究

为了解Ni-纳米SiC体系的刷镀特性,针对Ni刷镀液、纳米SiC和分散剂组成的刷镀液体系的沉降过程进行了研究.试验表明:当分散剂浓度大于2.5%时,可以充分分散纳米SiC颗粒,在沉降过程中,不易形成大的颗粒聚集体,颗粒的最终沉积密度增大,沉降粉体体积减小;在同样条件下,随着环境温度的升高,造成连续相黏度下降及扩散速度加快,使沉降速度升高;镀液中纳米SiC含量≤3g/L时,在分散剂作用下纳米SiC分布均匀稳定,沉积速度减慢.     

超声波对电镀金刚石工具性能的影响

分别在有超声波和无超声波条件下,制备了镍镀层和电镀金刚石工具。采用显微硬度计测试了镍镀层硬度,采用热震法和锉削法测试镀层与基体的结合强度,用显微镜观察镀层金相组织,计算了工具磨削比。研究结果表明:在电镀金刚石工具制备过程中,应用超声波可以细化镀层晶粒,提高镀层硬度,增强镀层与基体的结合强度。上砂前应用超声波可提高电镀金刚石工具磨粒密度和工具的磨削比。     

超声波作用对金刚石提纯效果的影响

通过大量实验,我们研究出一种提纯超细金刚石微粉的新方法:在专用试剂中利用超声波强力分散作用,打开金刚石制备过程形成的聚结体杂质,这样就增加试剂的接触面积,提高杂质成分的分解效果,最终得到提纯至99.95%以上的超细金刚石微粉.结果表明:在30 min之内提纯效果随着超声时间的增加而增加,超声时间超过30 min以后提纯效果反而会下降,在超声时间为30 min时提纯效果有一最佳值.并借助TG-DSC、XRD等测试方法对提纯前后的金刚石微粉进行对比分析.     

纳米TiO2在水性介质中分散工艺的初步研究

用沉降法研究了纳米TiO2在水性介质中进行物理和化学分散的工艺.结果表明:在三种方法中,超声分散效果最好,十二烷基苯磺酸钠分散效果较好,电动搅拌分散效果较差;对电动搅拌分散,搅拌大约90 min,转速适当高一些分散效果最好;对超声分散,超声电压大约在180 V,超声约70 min分散效果最好;对采用十二烷基苯磺酸钠分散,其加入量在12.0 g/L为宜.     

超声波对电镀金刚石工具制备过程的影响

应用超声波制备了镀层和电镀金刚石工具，测试镀层硬度和金刚石工具的上砂密度，研究结果表明：当电流密度一定时，金刚石工具镀层硬度随超声波功率增强而增加。在金刚石工具制备过程，超声波不适用上砂的全过程。只要金刚石磨粒埋入镀层厚度合适，超声波可以用于金刚石工具的加厚过程，提高工具的制备效率。     

Surface modification of nanodiamond in aqueous medium

1　INTRODUCTIONTheresearchandpracticeofnanodiamond (dia mondofnano scale ,insomearticlesultrafinedia mond (UFD )orultradisperseddiamond (UDD )iscalled)synthesishasstartedbothintheUnitedStatesandtheformerUSSRinearlier 1980s[1,2 ] .Afterthat,reportsabouttheresearchandsynthesisofthisnano scalematerialpresentthemselvescontinuously .TheproductsofthiskindcomeforthinJapan ,Ger many ,GreatBritainandFranceaswell[3,4 ] .Scien tistsinlandhavealsoshowntheirinterestandinten sivestudieshavealsob…     

毫秒脉冲激光辐照炭黑颗粒悬浮液制备纳米金刚石

采用较低功率密度(106 W/cm2左右)的Nd:YAG毫秒脉冲(脉宽0.2～20 ms)激光辐照循环溶液中的经球磨的炭黑颗粒悬浮液,成功地合成出了尺寸在5 nm左右的纳米金刚石,且粒度分布均匀,利用透射电镜对提纯前和提纯后的产物进行了分析,发现产物中同时存在纳米碳洋葱、石墨颗粒和金刚石颗粒.推测可能的相变机理是激光束辐照炭黑,因为激光束内能量分布不均匀,导致部分炭黑温度升高较小,颗粒经历低温退火作用后少量炭黑无序组织发生石墨化转变,体积收缩形成纳米碳洋葱.温度升高较大的炭黑组织大量发生石墨化转变,后续的能量导致石墨化组织再通过固-固切变机制转化为金刚石结构.     

超声波和热处理对羟基磷灰石结晶度和形貌的影响

以Ca(NO3)2·4H2O和(NH4)2HPO4为原料,采用化学沉淀法,在超声波和机械双重搅拌下,常压合成了羟基磷灰石(简称HA).对热处理前后的产物进行了X射线衍射(XRD)和透射电镜(TEM)分析.结果表明:热处理能显著提高HA粉体的结晶度;热处理前的HA粉体晶粒尺寸较小,热处理后HA晶粒长大.采用超声波和机械双重搅拌获得的HA粉体的结晶度比采用单纯机械搅拌获得的HA粉体的结晶度高.而且,采用双重搅拌获得的HA粉体晶粒大小比较均匀,形状趋于球形,且团聚粘联现象减少,分散性好.     

Features of ultrasonic wave propagation to identify defects in composite materials modelled by finite element method

A two-dimensional plane strain finite element model with absorbing boundary condition has been developed to investigate the ultrasonic wave propagation in isotropic and orthotropic media. It is capable of simulating the experimental pulse echo technique to obtain A-scan data, when a short duration pulse is transmitted into a domain with or without a flaw. The flaw can either be a crack or an inclusion of different material such as a Teflon insert or a resin rich zone. After performing FFT on the A-scan data, frequency domain feature analysis is done. The study provides a guideline regarding the suitability of certain harmonics sensitive to certain types of flaw. The simulation shows other important artifacts of wave propagation such as mode conversion and scattering due to the presence of flaws.     

Effect of edge preparation on the weldability of plastics in ultrasonic welding

The kinetic mechanism of the formation of welded joints with ‘preferential penetration’ and ‘preferential melting’ in ultrasonic welding of plastics is described. It is shown that the preparation of weld edges in ultrasonic welding of rigid plastics increases the welding speed.     

3种分散剂对ITO浆料稳定性能的影响

选用3种分散剂(聚乙烯吡咯烷酮、柠檬酸三铵、β-丙氨酸),通过球磨分散法制备ITO浆料,通过考察球磨分散时间和分散剂量对ITO浆料稳定性能的影响,分析比较不同分散剂对浆料稳定性作用,并探究其分散机理。结果表明:3种分散剂分散机制均为静电和空间位阻稳定作用;在相对ITO粉体质量比为5%、最佳球磨分散时间为48 h时,在15 d内ITO浆料的RSH可维持在10%以内;3种分散剂对ITO浆料稳定性的影响由强至弱的顺序为:聚乙烯吡咯烷酮>β-丙氨酸>柠檬酸三铵,与其在溶液中酸碱性强弱顺序一致,其中聚乙烯吡咯烷酮的分散效果最好。     

薄壁LY12铝合金焊接残余应力超声波法无损测量及验证

传统残余应力破坏测量方法无法满足焊接结构服役状态下的应力测量,无法实现结构的无损应力测量.基于声弹性原理,超声波法可以无损测量出结构内部的残余应力.使用临界折射纵波进行薄壁结构件测量时,易激发Lamb波和Stonely波等特殊波形,将影响测量的准确度.开发了适用于薄壁结构件测量的新型超声波法焊接残余应力测量系统,对厚度为2mm的两种LY12薄壁焊接结构进行了测量,测量过程实时无损快速.用切割释放法和有限元模拟进行了验证.结果表明,该测量系统准确可靠,为航天器薄壁焊接结构服役状态在线可靠性评估奠定了基础.     

双丝焊铝合金平板残余应力梯度超声波法建立

在假设无限小波叠加在各向同性变形弹性体基础上,推导了超声波法应力测量的理论基础声弹性方程,特殊条件下简化出临界折射纵波声弹性方程.建立了超声波法焊接残余应力测量系统,选用对应力敏感的临界折射纵波作为测量波形,对20 mm厚X坡口双丝焊对接2219铝合金平板纵向残余应力场梯度进行了测量,获取了纵向残余应力场引起的声时差信号分布,用MARC软件计算了铝合金残余应力场纵向应力的分布,与声时差信号的趋势进行了对比,趋势符合.为超声波法重建焊接残余应力场作了准备.     

Setting time study of roller compacted concrete by spectral analysis of transmitted ultrasonic signals

The setting time of roller compacted concrete (RCC) is determined by studying the increase in the propagation velocity of ultrasonic waves transmitted through a sample. In the case of a quick setting binder, this method proves unsatisfactory. Concrete setting is modelled by dissociating the chemical kinetics related to the volume transformations from those related to the surface transformations. Calculations show that the latter, and hence the percolation phenomenon, are prevalent in wave propagation and concrete setting. As a result we assume that concrete acts as a time-varying spectral filter. We are developing tests and software to show that the energy and the frequency spectrum of the transmitted ultrasonic signal makes it possible to analyse the setting process and determine the setting time.     

Reliability of ultrasonic testing methods for hot-rolled steel bars of medium and small diameter

This article describes research on the reliability of ultrasonic testing methods for hot-rolled steel bars of 40–60 mm diameter. Comparison of testing methods is made using direct contact with the bars along the circumferential surface using a straight beam probe (‘S’ probe), a twin crystal probe where the probe face is contoured to the bar curvature (‘SR’ probe) and a straight beam probe with a delay block. The distribution state diagrams of the echo sound pressure and the effective testing range in the cross-section of the bars are obtained. The conclusion is that methods using the SR probe and the straight beam probe with the delay block produce better quality results for steel bars with diameters equal to or smaller than 60 mm, but the S probe is not suitable.