衬底温度对低功率直流磁控溅射ZnO薄膜特性的影响

采用低功率直流反应磁控溅射法,在Si衬底上成功制备出了具有高c轴择优取向的ZnO薄膜,利用X射线衍射仪、荧光分光光度计研究了沉积温度对ZnO薄膜微观结构及光致发光特性的影响.结果表明,合适的衬底温度有利于提高ZnO薄膜结晶质量;在室温下测量样品的光致发光谱(PL),观察到波长位于440nm左右和485nm左右的蓝色发光峰及527nm左右微弱的绿光峰,随衬底温度升高,样品的PL谱中蓝光强度都明显增大,低功率溅射对其蓝光发射具有很重要的影响.综合分析得出440nm左右的蓝光发射应与Zni有关,485nm附近的蓝光发射是由于氧空位形成的深施主能级上电子跃迁到价带顶的结果,而527nm左右的较弱的绿光发射主要来源于导带底到氧错位缺陷能级的跃迁.生长温度主要是通过改变薄膜中缺陷种类及浓度而影响着ZnO薄膜的发光特性的.     

Zn缓冲层对氧化锌薄膜的结构和光学特性的影响

采用射频磁控溅射法在玻璃衬底上制备了具有高c轴择优取向的不同Zn缓冲层厚度的ZnO(ZnO/Zn)薄膜。利用X射线衍射(XRD)法、扫描电子显微镜(SEM)技术和光致荧光(PL)发光谱(PL)等表征了ZnO/Zn薄膜的微观结构和发光特性。XRD的分析结果显示,随着缓冲层厚度的增加,(002)衍射峰的半高宽(FWHM)逐渐变小,表明薄膜的结晶质量得到改善。通过对样品PL谱的研究,发现分别位于435(2.85eV)和480nm(2.55eV)的蓝光双峰以及530nm(2.34eV)的绿光峰,且缓冲层沉积时间为10min时,样品的单色性最好。推测位于435nm的蓝光发射主要来源于电子从锌填隙缺陷能级到价带顶的跃迁所致,而绿光峰的发光机制与氧空位有关。     

沉积气压对磁控溅射制备ZnO薄膜的结构与光学性能影响

采用CS-400型射频磁控溅射仪在Si(111)和石英基底上成功的制备了ZnO薄膜,分别用XRD、SEM、紫外-可见光分光光度计和荧光分光光度计表征样品的结构和光学性质.实验表明,采用射频磁控溅射制备的ZnO薄膜具有六角纤锌矿结构的(002)峰和(101)峰的两种取向.在沉积气压>1.0Pa时所制备的ZnO薄膜具有(002)择优取向,并且十分稳定.SEM图表明,ZnO薄膜颗粒大小较为均匀,晶粒尺寸随着气压升高而变小,沉积气压不同时,薄膜样品的生长方式有所差异.在400～1000nm范围内,可以看出除O.5Pa下制备的ZnO薄膜外,其余ZnO薄膜在可见光区域的平均透过率超过80%,吸收边在380nm附近,所对应的光学带隙约为3.23～3.27eV,并随着沉积气压上升而变大.ZnO薄膜的PL谱上观察到了392nm的近紫外峰和419nm的蓝峰;沉积气压对Zno薄膜的发光峰位和峰强有影响.     

不同生长温度下Zn1-xSbxO薄膜的结构与发光性能研究

采用固相反应法制备了不同比例的Sb掺杂ZnO靶材,并用脉冲激光沉积(PLD)法在Si(100)基底上制备了Zn_1-xSb_xO薄膜。通过XRD、光致发光(PL)谱对所制薄膜进行了结构表征和性能分析,探讨了不同Sb掺杂量和不同生长温度对薄膜结晶质量和发光性能的影响。结果表明：对比纯ZnO的PL谱发现ZnSbO薄膜出现了紫外峰,且随着Sb浓度的增加,所有发光峰的强度相对增大;针对Zn_0.98Sb_0.02O薄膜,不同的基底生长温度改变了薄膜的紫外和蓝光发射强度,500℃下薄膜具有最好的结晶质量和最强的发光峰;对于500℃下生长的Zn_0.98Sb_0.02O薄膜,当激发光源波长从325nm变化到300nm,峰位红移,而且紫外峰与蓝光锋强度比由1∶3变为12∶1。据此,可以通过改变Sb掺杂量、生长温度和激发光源波长,从而制备出不同波段、不同强度的发光器件。     

ZnO缓冲层上低温生长Al掺杂的ZnO薄膜

采用射频磁控溅射法在ZnO缓冲层上制备了不同Al掺杂量的ZnO（AZO）薄膜。利用X射线衍射（XRD）、扫描电子显微镜（SEM）和光致发光（PL）等表征技术,研究了AZO薄膜的微观结构、表面形貌和发光特性。结果表明,随着Al掺杂量的增加,ZnO薄膜的择优取向性发生了改变,且当Al的掺杂量为0.81%（原子分数）时,（002）衍射峰与其它衍射峰强度的比值达到最大,表明适合的Al掺杂使ZnO薄膜的择优取向性得到了改善。在可见光范围内薄膜的平均透过率超过70%。通过对样品光致发光（PL）谱的研究,发现所有样品出现了3个发光峰,分别对应于以444nm（2.80eV）、483nm（2.57eV）为中心的蓝光发光峰和以521nm（2.38eV）为中心较弱的绿光峰。并对样品的发光机理进行了详细的探讨。     

Ni2+掺杂ZnO薄膜及粉体的结构和发光性能研究

采用激光脉冲沉积法,用XeCl准分子激光器在Si (100)基片、真空和5Pa氧气气氛下制备了Ni2+(0.8％(原子分数))掺杂的呈六角纤锌矿结构的ZnO薄膜.氧气气氛下制备的薄膜沿(002)取向生长,表面比较平整,平均颗粒尺寸为80nm.真空条件下制备的薄膜出现Zn2SiO4杂相,平均颗粒尺寸为150nm.和真空条件下制备的薄膜相比,氧气气氛下制备的薄膜具有较强的ZnO本征发光,在425nm附近出现由于填隙Zn缺陷引起的较宽的蓝光发光带,并且在482nm处出现了由于氧空位和氧间隙间的转换引起的较强的蓝光发光峰,同时由于氧缺陷引起的449nm附近的蓝光发光峰强度明显降低.     

RF溅射稀土掺杂ZnO薄膜的结构与发光特性

通过射频磁控溅射技术在Si(111)衬底上制备了未掺杂和La、Nd掺杂ZnO薄膜.XRD分析表明,ZnO薄膜具有c轴择优生长,La、Nd掺杂ZnO薄膜为纳米多晶薄膜.AFM观测,La、Nd掺杂ZnO薄膜表面形貌较为粗糙.从薄膜的室温光致光谱中看到,所有薄膜都出现了395 nm的强紫光峰和495 nm的弱绿光峰,La掺杂ZnO薄膜的峰强度增大,Nd掺杂ZnO薄膜的峰强度减弱,分析了掺杂引起PL峰强度变化的原因.     

Ti缓冲层对ZnO薄膜吸收特性和荧光光谱的影响

采用射频磁控溅射法在Si衬底和玻璃衬底上制备了ZnO/Ti薄膜,利用紫外-可见分光光度计和荧光分光光度计等技术表征了ZnO/Ti薄膜的光学特性,研究了Ti缓冲层的厚度对ZnO薄膜的影响。透射吸收光谱显示所有ZnO薄膜在可见光区域的平均透过率超过80%,当引入缓冲层后,薄膜的紫外吸收边先向长波方向移动,且随着缓冲层厚度的增加紫外吸收边向短波方向移动。薄膜的荧光光谱显示,所有样品出现了位于390nm的紫外发光峰,435和487nm的蓝光双峰以及525nm的绿光峰,并对各发光峰的来源进行了探讨。     

Ge掺杂ZnO薄膜光学特性的研究

采用射频磁控共溅射法在硅基片上沉积了Ge掺杂ZnO薄膜,所制备的样品具有强蓝光发射和弱黄光发射.通过分析Ge掺入量和退火温度对发光谱的影响,并与相同条件下所沉积的纯ZnO薄膜的发光特性进行比较,结果表明,蓝光发射可能与Ge杂质形成的施主能级有关,弱黄峰可能源于Ge替代Zn空位形成的杂质能级到价带的跃迁复合.     

ITO上磁控溅射ZnO薄膜及其光电性质

在ITO(In2O3:Sn)衬底上射频溅射ZnO薄膜,研究了射频溅射功率对ZnO薄膜的晶体结构,表面形貌及光学透过率的影响.结果表明,随着射频功率的提高,沿(002)方向生长的ZnO薄膜的结晶度显著增强,薄膜的表面颗粒略有减小,表面粗糙度由13.13 nm降低到5.06 nm.在300～400 nm波长范围内薄膜的光学透过率随着射频功率的增加而降低.在双层薄膜中空间内建电场的存在有助于光生电子和空穴有效地分离,使ZnO/ITO双层薄膜具有较强的光电响应能力,光电流达14μA.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...