退火对Cr3+离子掺杂Al2O3薄膜的结构及发光性能影响

用脉冲激光沉积技术在Si(100)基底上制备了纯Al2O3、掺杂浓度为0.3%、1%(质量分数)的Cr3+∶Al2O3薄膜。制备态的薄膜为立方γ-Al2O3结构,经800℃真空条件下退火1h样品的结晶度有所提高,呈现α-Al2O3相与γ-Al2O3相的衍射峰。薄膜基本保持了靶材中原有各元素成分比例,平均粒径为250nm,形貌为条形。与Al2O3粉体相比,制备态薄膜在386nm处的发光峰强度明显提高。这可归因于薄膜中氧空位的增加使双氧空位吸收电子所产生的F2+色心浓度提高。薄膜经真空退火后在332、398nm附近的发光峰强度明显增强,这是由于薄膜中氧空位的增加提高了F+、F色心浓度。与此同时,制备态薄膜在386nm附近发光峰经退火后由386nm蓝移至381nm,可归因于退火后制备态薄膜的内应力得到了释放。1%(质量分数)Cr3+掺杂薄膜在646、694nm出现Cr3+离子由4 T2能级跃迁至4 A2能级及由E-能级跃迁至4 A2能级产生的荧光发光峰。     

ZnO缓冲层退火温度对Ti02∶Eu/ZnO薄膜光致发光性能的影响

采用溶胶-凝胶法在普通载玻片上制备出以ZnO为缓冲层、稀土Eu3+掺杂的TiO2薄膜,研究了ZnO缓冲层退火温度对TiO2∶Eu薄膜的光致发光性能以及晶体结构的影响.结果表明,随着ZnO层退火温度的升高,薄膜的PL谱增强,在500℃退火时达到最强;XRD显示,TiO2∶Eu3+/ZnO薄膜中有很强的ZnO(002)衍射峰,但是TiO2的(101)衍射峰却很微弱,且ZnO在500℃退火时TiO2的(101)衍射峰最弱.     

电子束蒸发法制备掺钇稳定氧化锆薄膜的光学特性研究

利用电子束蒸镀方法在单晶硅和石英玻璃上制备了掺不同Y_2O_3浓度的掺钇稳定ZrO_2薄膜(YSZ),用X射线衍射、原子力显微镜、扫描电子显微镜和透射光谱测定薄膜的结构、表面特性和光学性能,研究了退火对薄膜结构和光学性能的影响.结果表明:一定浓度的Y_2O_3掺杂可以使ZrO_2薄膜稳定在四方相,退火显著影响薄膜结构,随着温度的升高薄膜结构依次经历由非晶到四方相再到四方和单斜混合相转变;AFM分析显示薄膜表面YSZ颗粒随着退火温度的升高逐渐增大,表面粗糙度相应增大,晶粒大小计算表明,退火温度的提高有助于薄膜的结晶化,退火温度从400℃到1100℃变化范围内晶粒大小从15.6nm增大到46.3nm;同时利用纳秒激光对薄膜进行了破坏阈值测量,结果表明电子束蒸镀制备YSZ薄膜是一种制备高抗激光损伤镀层的有效方法.     

脉冲激光沉积制备立方AlN薄膜的研究

采用脉冲激光沉积(PLD)方法,在SrTiO3(100)衬底上在650℃、10Pa N2条件下成功制备了立方结构的AlN薄膜.高能电子衍射(RHEED)及X射线衍射(XRD)分析表明立方AlN和SrTiO3的外延关系为AlN[100]∥SrTiO3[100]和AlN(200)∥SrTiO3(100).其AlN(200)衍射峰的摇摆曲线半高宽(FWHM)为0.44°,说明薄膜结晶性能良好.原子力显微镜(AFM)表明外延的立方AlN薄膜表面具有原子级平整度,其表面均方根粗糙度(RMS)为0.674nm.通过X光电子能谱(XPS)分析AlN薄膜表面成分,结果表明AlN薄膜表面没有被氧化.     

脉冲激光沉积方法生长硅基ZnO薄膜的特性

用脉冲激光沉积法(PLD)在n型硅(111)平面上生长ZnO薄膜.X射线衍射(XRD)在2θ=34°处出现了唯一的衍射峰,半高宽为0.75°;傅里叶红外吸收(FTIR)在414.92cm-1附近出现了对应Zn-O键的红外光谱的特征吸收峰;光致发光(PL)测量发现了位于370和460nm处的室温光致发光峰;扫描电子显微镜(SEM)和选区电子衍射(SAED)显示了薄膜的表面形貌以及晶格结构.利用PLD法制备了具有c轴取向高度一致的六方纤锌矿结构ZnO薄膜.     

Mg2Si半导体薄膜的磁控溅射制备

采用磁控溅射技术和退火工艺制备出Mg2Si半导体薄膜,研究了退火时间对Mg2Si薄膜的形成和结构的影响.首先在Si(111)衬底上溅射沉积380nm Mg膜,然后在退火炉内氩气氛围500℃退火,退火时间分别为3.5h、4.5h、5.0h、5.5h、6.0h.采用X射线衍射和扫描电镜对薄膜的结构和形貌进行了表征.结果表明,采用磁控溅射方法成功地制备了环境友好的半导体Mg2Si薄膜.Mg2Si薄膜具有Mg2Si(220)的择优生长特性,最强衍射峰出现在40.12°位置;随着退火时间的延长,Mg2Si外延薄膜的衍射峰强度先逐渐增强后逐渐减弱,退火5h后,样品的衍射峰最强.Mg2Si晶粒随着退火时间的延长,先逐渐增大,退火5h后逐渐减小.     

退火温度对等离子体增强化学气相沉积方法生长的ZnO薄膜质量的影响

研究ZnO薄膜质量与退火温度的关系,为了获得高质量的晶体薄膜,采用PECVD方法在硅(100)衬底上生长ZnO薄膜,生长温度为120℃,然后分别在氧气环境下退火(600℃～1000℃)1 h.X射线衍射谱和原子力显微镜(AFM)照片结果表明随着退火温度的升高,晶体择优取向明显,晶粒平均尺寸增大,到900℃时,晶粒平均尺寸达到38 nm.光致发光谱的结果表明,随着退火温度的升高,发光峰的半高宽(FWHM)逐渐地变窄,到900℃时,达到92meV,晶体质量得到了明显提高.通过对变温光谱的拟合计算,得到激子束缚能为59 meV,表明紫外发射来自于自由激子辐射复合.     

[100]取向Al-Ti共掺杂ZnO薄膜的制备与光电性能研究

采用常压固相烧结法制备了Al-Ti共掺ZnO靶材, 采用射频磁控溅射技术及真空退火工艺, 在普通玻璃衬底上制备了具有[100]取向Al-Ti共掺杂ZnO薄膜(ZATO). 采用X射线衍射(XRD)、扫描电子显微镜(SEM)对ZATO薄膜的生长机理、显微结构、形貌进行了测试分析, 用四探针测试仪、紫外-可见分光光度计及荧光光谱仪对ZATO薄膜的光电性能进行了测试分析. 结果表明, ZATO薄膜经500℃保温3h退火后, 择优取向由(002)向(100)方向转变; 此时, 衍射谱上还观察到超点阵衍射线条. [100]取向ZATO薄膜的光学带隙从退火前的3.29降至2.86, 平均可见光透过率从90%降至70%, 表现为一般的透过性; 而电阻率则从1.89×10^-2Ω·cm降至1.25×10^-3Ω·cm, 呈现较好的导电性. 薄膜中均出现了380nm附近的带边发射(NBE)峰以及410、564nm的深能级发射峰, 且经500℃保温3h退火后, 这些峰的位置并未改变, 但峰强均明显减弱. 对上述实验机理进行了分析讨论.     

后退火对射频磁控溅射制备β-Ga_2O_3薄膜的影响

采用射频磁控溅射法制备了氧化镓(Ga_2O_3)薄膜,计算了薄膜的O/Ga摩尔比,比值为1.57。研究了后退火对薄膜结构,形貌特征和光学带隙的影响。X射线衍射(XRD)结果表明,退火前的Ga_2O_3薄膜是一种无定形结构。在600℃氧气氛中退火2h后,薄膜开始出现β-Ga_2O_3的(■01)衍射峰;随着退火温度的升高,β-Ga_2O_3(■01)衍射峰进一步增强,并且半高宽从0.61°减小到0.49°。原子力显微镜(AFM)测试结果表明,退火前后薄膜表面的均方根粗糙度从3.47 nm增加到了7.08 nm,晶粒尺寸从19 nm增加到了53 nm。紫外-可见分光光度计(UV-VIS)测试结果表明Ga_2O_3薄膜在250 nm-1500 nm波长范围内的平均透过率在85%以上。利用Tauc公式计算了Ga_2O_3薄膜的光学带隙,带隙宽度在(4.85-5.06)eV之间,且随退火温度增加而减小。分析了表面形貌、光学带隙与薄膜结构之间的关系。     

生长温度对等离子体增强化学气相沉积生长ZnO薄膜质量的影响

以Zn(C2 H5) 2 和CO2 为反应源 ,在低温下用等离子体增强化学气相沉积方法 ,在Si衬底上外延生长了高质量的ZnO薄膜。用X射线衍射谱和光致发光谱研究了衬底温度对ZnO薄膜质量的影响。X射线衍射结果表明 ,在生长温度为2 3 0℃时制备出了高质量 ( 0 0 0 2 )择优取向的ZnO薄膜 ,其半高宽为 0 2 6°。光致发光谱显示出强的紫外自由激子发射与微弱的与氧空位相关的深缺陷发光 ,表明获得了接近化学配比的ZnO薄膜     

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.……     

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.……     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.