烧结对纳米铁酸盐的影响

采用TEM和XRD方法研究了热处理条件对于纳米铁酸盐的结构和性能的影响。结果表明:随煅烧温度升高,纳米铁酸盐晶粒尺寸显著增大,晶粒发育趋于完整导致晶格畸变度明显降低,结构致密程度增加使得晶格常数减小,粉体烧结程度增大,相应粉体相对密度随之增加;较低温度(如300℃)下,煅烧时间对纳米铁酸盐晶粒尺寸无明显影响,相应晶格畸变度、晶格常数和粉体相对密度变化不大;较高温度(如600℃)下,铁酸盐晶粒尺寸随煅烧时间延长而增大,且煅烧初期粒子增长较快,此过程伴随着铁酸盐晶格畸变度进一步下降,晶格常数却有所增加,粉体相对密度略有下降;认为烧结过程铁酸盐晶粒生长为扩散生长机制是造成不同煅烧温度下煅烧时间对纳米铁酸盐微观结构和性能的影响行为不同的主要原因。     

BaTi03/铁氧体复合材料的制备及性能

采用传统溶胶-凝胶法和改进的柠檬酸盐溶胶-凝胶法制得了钦酸钡,并对其进行了比较.采用柠檬酸-EDTA的联合络合溶胶-凝胶法制得了针状纳米锶铁氧体磁性微粒,并将钛酸钡和锶铁氧体进行了复合.利用XRD对样品的物相进行分析,利用TEM对样品形貌和粒径进行表征,利用振荡样品磁强计(VSM)对样品进行了磁性能研究,并利用矢量网络分析仪对粉末的电磁波吸收性能进行了表征.结果表明,在2～6GHz范围内,钛酸钡质量分数为30%的复合材料在850℃煅烧2h后吸波性能最佳,最大吸收量为28dB,10dB频带宽度为1.7GHz.     

负载氧化铟纳米颗粒多壁碳纳米管的制备与表征

在NaOH溶液活化、混合酸(浓硫酸和浓硝酸混合)处理多壁碳纳米管(MWNTs)的基础上,利用共沉淀法和后续热处理制备了多壁碳纳米管/氧化铟复合粉体,并使用X射线衍射仪和电子显微镜表征了复合粉体的物相和形貌。结果表明:NaOH和混合酸处理能在多壁碳纳米管表面引入丰富的羟基和羧基等官能团,且大大提高了碳纳米管的比表面积;煅烧多壁碳纳米管/氢氧化铟前驱体后,能够得到负载纳米氧化铟的多壁碳纳米管,其中450℃煅烧的效果最好,粒径为20～30nm的纳米氧化铟颗粒均匀覆盖在碳纳米管表面上。     

高分子网络凝胶法制备氧化物纳米陶瓷粉体

以Al2O3和Y2O3纳米陶瓷粉体的制备为例,研究了高分子网络凝胶法制备氧化物纳米陶瓷粉体的过程及其影响因素.制备了颗粒尺寸小于20nm的Al2O3和Y2O3粉体,分析了网络凝胶机理和胶体的热失重过程.对粉体进行煅烧发现氧化铝的最佳煅烧温度为1100℃;氧化钇的最佳煅烧温度为850℃.单体和网络剂的摩尔比例对粉体粒度有一定影响当单体和网络剂的比例为51时,所制备的纳米颗粒尺寸细小,均匀;当比例偏离51较大时,团聚比较严重,且一部分颗粒尺寸长大,造成颗粒尺寸分布不均匀.     

雾滴微反应器法制备纳米氧化铝粉体

以硫酸铝铵和碳酸氢铵为原料,用新技术--雾滴微反应器法制备了纳米氧化铝粉体,并与用传统沉淀法制备的纳米氧化铝粉体进行比较,用SEM和TEM等方法对制备的前驱体和最终粉体进行表征,用XRD法对最终粉体进行物相分析.结果表明:雾滴微反应器法制备的纳米氧化铝粉体比传统沉淀法制备粉体的颗粒尺寸较小,粒径分布窄,分散性好,比表面积达到138.1cm2·g-1;前驱体在1 150℃煅烧20 min可完全转化为α-Al2O3.     

相转移法制备纳米CoFe_2O_4粉体

采用相转移法制备了纳米CoFe2O4前驱体.运用差示扫描量热仪(DSC)研究了纳米CoFe2O4前驱体的热分解特性.利用XRD、TEM研究了不同煅烧温度对生成的纳米CoFe2O4成分、形貌和粒度的影响,探讨了相转移法的制备机理.结果表明:相转移法可有效控制成核速度,油相的成膜有效地实现了阻聚作用,400℃为最佳煅烧温度,所得到的CoFe2O4粉体呈规则的立方形链状分布,无明显团聚体,平均粒径为30 nm,且粒径分布窄.     

利用综合热分析仪研究纳米二氧化钛凝胶的热稳定性

以TiCl4为原料,分别以Cr(NO3)3、Fe(NO3)3和Al(NO3)3为掺杂剂,采用共沉淀制备了含不同掺杂剂和掺杂量的纳米二氧化钛凝胶,利用综合热分析仪(热重分析一差示扫描量热联用仪,简称DSC-TG)研究了纳米二氧化钛凝胶从30-1100℃热稳定性以及组分和物相的变化,XRD测定了二氧化钛凝胶在煅烧过程中晶型转变。结果表明:含不同掺杂剂和不同掺杂量凝胶的DSC-TG曲线有很大的差别;Cr3+和Fe3+掺杂能促进金红石相的形成,Al3+掺杂有利于锐钛矿相的稳定。     

超临界流体干燥法制备纳米ZrO2粉体及其煅烧行为研究

用超临界流体干燥法制备了纳米ZrO2粉体,并用不同热处理工艺进行处理,之后对样品进行TEM和XRD分析。结果表明,煅烧温度和煅烧时间对纳米ZrO2粉体性能的影响是显著的。随着煅烧温度的提高和时间的延长,粉体由t相转变为m相,晶粒尺寸逐渐增大,但是煅烧温度对ZrO2相组成和晶粒尺寸的影响比时间的影响更大。     

改进Pechini法制备镍铁氧体纳米颗粒及其表征

用改进的Pechini法制备了高度分散的泡沫凝胶颗粒,然后分别在500,650,800℃进行热分解得到了镍铁氧体纳米颗粒;用XRD、TEM、IR及VSM等对其形貌、结构和磁性能进行了分析。结果表明:用改进Pechini法得到的镍铁氧体纳米颗粒分散性好,尺寸均匀,晶化程度高,纯度高;500℃热解后得到的镍铁氧体粒径为50～120nm;室温下在796kA.m-1磁场下的饱和磁化强度可达13.03kA.m-1;随着热解温度的升高,镍铁氧体纳米颗粒的直径、饱和磁化强度、矫顽力都增大。     

乙二胺四乙酸络合溶胶-凝胶法制备CuFeMnO_4尖晶石复合金属氧化物

采用乙二胺四乙酸(EDTA)络合溶胶一凝胶法制备了CuFeMnO4尖晶石复合金属氧化物,用TG-DTA、IR、XRD、SEM等仪器对其干凝胶的热分解过程、产物物相结构、微观形貌和太阳光吸收率等进行了分析表征.结果表明:制备的干凝胶在442℃以上已基本分解完全;经600℃煅烧晶化后形成CuFeMnO4尖晶石复合金属氧化物,平均晶粒尺寸在14 nm左右,但纳米颗粒已严重团聚,形成大的颗粒;所获得的复合金属氧化物粉体对200～2 500 nm波长范围的太阳光吸收率约为85.435%.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.