共沉淀法制备Ca0.6Mg0.4Zr4(PO4)6纳米粉体

采用共沉淀法,以Ca(NO3)2·4H2O、Mg(NO3)2·6H2O、ZrO(NO3)2·8H2O和NH4H2PO4为原料合成Ca0.6Mg0.4Zr4(PO4)6(C0.6M0.4ZP)纳米粉体,通过TG-DSC、XRD、TEM和纳米粒度/Zeta电位分析手段研究了反应过程pH值、反应物浓度配比和沉淀反应方式等对合成粉体的相组成、平均颗粒尺寸及其分布等的影响.结果表明:将Ca2 、Mg2 、Zr4 离子混合溶液加入到不同pH值的NH4H2PO4溶液中,并控制pH=3～11,沉淀物经900℃煅烧3 h后,可合成单相的C0.6M0.4ZP纳米粉体;当Zr4 浓度为0.5 mol/L、沉淀剂NH4H2PO4浓度为1.0 mol/L、pH=9时,合成粉体平均颗粒尺寸和粒径分布范围最小,分别为40 nm和20～70 nm.     

室温气敏型Fe2O3纳米膜的制备及表征

针对传统Fe2O3气敏元件工作温度高、响应时间长等缺点,采用分析纯FeCl3·6H2O和乙醇为主要原料,以AI2O3陶瓷片为基底,利用溶胶凝胶法制备了Fe2O3纳米膜及气敏元件.利用XRD(X射线衍射)、AFM(原子力显微镜)对纳米膜的结构及形貌进行了表征,结合Fe2O3纳米膜的形成机理,主要讨论了镀膜次数对薄膜结构、性能的影响;研究了薄膜元件的阻温特性及室温气敏性能.结果表明:镀膜20次后,Fe2O3颗粒粒径约为20～30 mn,镀膜30次后,纳米膜平整、均匀、无裂纹;室温下薄膜元件便对H2CH4有一定的气敏效应,响应时间小于3s,灵敏度随气体浓度变化呈线性关系.     

几种无机纳米粒子在润滑油中抗磨性对比研究

利用超声波纳米粉碎机制得无机复合纳米颗粒,通过选用合适的分散剂和采用超声波分散的方法,制备出悬浮性、分散性良好的油基纳米抗磨剂,采用摩擦试验机对所制备的产物的抗磨性与Al2O3、Si3N4纳米粉进行了对比试验及表征分析。结果表明实验制备的无机复合纳米颗粒相对于Al2O3、Si3N纳米颗粒具有更好的抗磨减摩性能,同时出现了负磨损现象,无机复合纳米粒子在摩擦副表面起到了修复作用。     

凝胶-热分解法制备NiFe_2O_4纳米粉末及其性能表征

以硝酸铁、硝酸镍以及柠檬酸为原料,采用凝胶-热分解法制备出了尖晶石NiFe2O4纳米粉末。研究了凝胶-热分解法的反应机理和反应过程,讨论了热处理温度对颗粒平均尺寸以及性能的影响。利用X射线衍射(XRD)、TEM以及VSM对样品物性进行表征,结果表明,所制样品为纯相的NiFe2O4纳米颗粒,颗粒的大小为35～65 nm,且颗粒的粒径随热处理温度的升高而增大,当热处理温度为700℃时,颗粒大小均匀、分散性好,比饱和磁化强度达到54.63 emu/g。同时,作者也对反应的动力学原理进行了研究,得出NiFe2O4纳米颗粒形成的活化能为16.15 kJ/mol。     

超声波技术在Fe3O4磁粒子制备中的应用

为制备磁粒子足够细小、均匀且稳定的磁性液体,将超声波技术引入Fe3O4磁粒子制备过程中,研究了化学共沉淀法制备Fe3O4磁粒子的不同阶段超声波功率对颗粒大小及磁性能的影响.结果表明:在共沉淀阶段引入超声波功率(40W)制备的Fe3O4磁粒子不易团聚,均匀细小;在包覆阶段引入超声波功率(40W)使表面活性剂在Fe3O4磁粒子表面形成稳定包覆层;在最佳条件下所制备Fe3O4磁粒子的平均粒径为10nm左右.     

选择性激光熔化原位自生TiB+La2O3/TC4钛基复合材料的组织和力学性能

以Ti-6Al-4V钛合金粉末和LaB6粉末为原料,采用选择性激光熔化(SLM)技术制备原位自生TiB+La2O3/TC4钛基复合材料以及TC4钛合金,对比研究了复合材料和钛合金的物相组成、显微组织、硬度和抗压强度.结果表明:复合材料和钛合金的显微组织均为β柱状晶及晶内分布的针状α'马氏体,复合材料的β晶粒和α'马氏体...     

SAF2205/16MnR爆炸法复合钢板焊接接头的耐腐蚀性能

采用钨极氩弧焊(TIG)及焊条电弧焊(SMAW)两种焊接工艺获得了SAF2205/16 MnR爆炸法复合钢板焊接接头;用化学浸泡法测试了接头的点腐蚀速率,用电化学腐蚀工作站测试了接头的极化曲线,并用光学显微镜观察了腐蚀形貌。结果表明:在6%FeCl3+H2O和6%FeCl3+15%HCl+H2O不同腐蚀条件下,SMAW接头和TIG接头的点腐蚀速率都很小;在室温条件下,不锈钢与接头焊缝金属区在3.5%NaCl溶液中的抗电化学腐蚀性能强弱依次为不锈钢、TIG接头、SMAW接头,三者的自腐蚀电位都为-0.3 V左右,两种接头均具有较好的耐腐蚀性能。     

温度对超细钴颗粒形貌及磁性能的影响

以硫酸钴、酒石酸钾钠、水合肼为原料,通过液相还原法在不同反应温度下制备出形貌各异的超细钴颗粒。采用扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)和振动样品磁强计(VSM)分别观察了样品的形貌、晶体结构和静磁特性。结果表明,利用水合肼还原硫酸钴制备的纯钴颗粒形貌随温度发生变化,温度对[C4H4O6]2+在不同晶面上吸附量的影响导致了不同晶面生长速率;随着反应温度的升高,超细钴颗粒剑状花瓣明显增强,反磁化过程中剑状花瓣内磁畴运动困难,最终导致所制备的钴颗粒矫顽力逐渐增加。     

SiC颗粒掺杂对激光直接成形Al2O3陶瓷裂纹敏感性的影响

为抑制激光直接成形Al2O3陶瓷过程中的裂纹,利用SiC未熔颗粒的增韧原理,在Ti-6Al-4V合金基底上进行添加SiC颗粒的Al2O3同轴送粉激光直接成形实验,分析了激光直接成形Al2O3+ SiC复相陶瓷的可行性以及成形件裂纹敏感性的影响因素.利用光学显微镜观察薄壁成形试样的裂纹扩展、显微组织和两相结合情况,并使用X射线衍射仪(XRD)进行相分析.结果表明:SiC颗粒可在激光直接成形Al2O3+SiC陶瓷中起到抑制裂纹的作用,并可形成各成分结合良好,无明显化学反应,含有较完整SiC未熔颗粒的复相陶瓷材料.单因素实验显示:SiC比例f、激光功率P、扫描速度v和送粉率n对裂纹敏感性均有显著影响,最后采用工艺参数:f =10％(重量百分比)、P=186 W、v=300 mm/min及n=1.78 g/min成形了裂纹敏感性低,无明显缺陷的长×高×厚约为17 mm×6 mm×2 mm的薄壁件.     

匀相沉淀法制备纳米Al2O3粉末

介绍了一种以工业用NH4Al(SO4)2*12H2O和NH4HCO3为原料采用匀相沉淀法制备纳米Al2O3粉末的新工艺,并研究了沉淀剂NH4HCO3的滴加速度、醇洗、表面活性剂等因素对Al2O3粒径的影响.研究结果表明,该工艺制备的粉体粒度均匀、平均粒径小于25nm.     

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...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

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.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.