THE CHANGING ROLE OF THE NATIONAL LABORATORIES IN MATERIALS RESEARCH

ＴＨＥＣＨＡＮＧＩＮＧＲＯＬＥＯＦＴＨＥＮＡＴＩＯＮＡＬＬＡＢＯＲＡＴＯＲＩＥＳＩＮＭＡＴＥＲＩＡＬＳＲＥＳＥＡＲＣＨＷＡＤＳＷＯＲＴＨＪｅｆｆｒｅｙａｎｄＦＬＵＳＳＭｉｃｈａｅｌ（ＣｈｅｍｉｓｔｒｙａｎｄＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅＤｉｒｅｃｔ...     

RECENT DEVELOPMENTS IN NiAl TECHNOLOGY FOR TURBINE AIRFOILS

ＲＥＣＥＮＴＤＥＶＥＬＯＰＭＥＮＴＳＩＮＮｉＡｌＴＥＣＨＮＯＬＯＧＹＦＯＲＴＵＲＢＩＮＥＡＩＲＦＯＩＬＳ￥Ｒ．Ｄａｒｏｌｉａ（ＧＥＡｉｒｃｒａｆｔＥｎｇｉｎｅｓ，１ＮｅｕｍａｎｎＷａｙ，Ｃｉｎｃｉｎｎａｔｉ，Ｏｈｉｏ４５２１５）Ａｂｓｔｒａｃｔ：Ｎｉ...     

ELECTROLYTIC SEPARATION FOR Ce－CARBIDE AND Fe－Ce－CARBIDE IN STEEL

ＥＬＥＣＴＲＯＬＹＴＩＣＳＥＰＡＲＡＴＩＯＮＦＯＲＣｅ－ＣＡＲＢＩＤＥＡＮＤＦｅ－Ｃｅ－ＣＡＲＢＩＤＥＩＮＳＴＥＥＬＸｉａｏ；ＱｉａｎｇＨａｎ；Ｑｉｙｏｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃａｌＣｈｅｍｉｓｔｒｙ，ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅ...     

ELECTROWINNING ZINC FROM CHLORIDE MELTS IN BIPOLAR CELL

ＥＬＥＣＴＲＯＷＩＮＮＩＮＧＺＩＮＣＦＲＯＭＣＨＬＯＲＩＤＥＭＥＬＴＳＩＮＢＩＰＯＬＡＲＣＥＬＬＺｈａｏ；Ｇｕａｎｇｗｅｎ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃａｌＣｈｅｍｉｓｔｒｙ，ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｙｇＢ...     

IN SITU GRADIENT DOUBLE-LAYER COMPOSITES OF Al-Fe ALLOY BY CENTRIFUGAL CASTING

ＩＮＳＩＴＵＧＲＡＤＩＥＮＴＤＯＵＢＬＥＬＡＹＥＲＣＯＭＰＯＳＩＴＥＳＯＦＡｌＦｅＡＬＬＯＹＢＹＣＥＮＴＲＩＦＵＧＡＬＣＡＳＴＩＮＧ①ＷａｎｇＱｕｄｏｎｇ，ＪｉｎＪｕｎｚｅＲｅｓｅａｒｃｈＣｅｎｔｅｒｏｆＦｏｕｎｄｒｙＥｎｇｉｎｅｒｉｎｇ，Ｄａｌ...     

EXAMINATION OF CARBON DIFFUSION IN TANTALUM CLAD STEEL COMPOSITE

ＥＸＡＭＩＮＡＴＩＯＮＯＦＣＡＲＢＯＮＤＩＦＦＵＳＩＯＮＩＮＴＡＮＴＡＬＵＭＣＬＡＤＳＴＥＥＬＣＯＭＰＯＳＩＴＥ①ＸｉａＣｈａｎｇｑｉｎｇ，ＪｉｎＺｈａｎｐｅｎｇＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｒｉｎｇ，Ｃｅ...     

BEHAVIOUR OF ELEMENTAL SULPHUR IN BIOOXIDATION OF GOLD-BEARING SULPHIDE ORES

ＢＥＨＡＶＩＯＵＲＯＦＥＬＥＭＥＮＴＡＬＳＵＬＰＨＵＲＩＮＢＩＯＯＸＩＤＡＴＩＯＮＯＦＧＯＬＤ－ＢＥＡＲＩＮＧＳＵＬＰＨＩＤＥＯＲＥＳ￥ＸｉａｎｇＬａｎ；ＫｅＪｉａｊｕｎ（ＩｎｓｔｉｔｕｔｅｏｆＣｈｅｍｉｃａｌＭｅｔａｌｌｕｒｇ，ＣｈｉｎｅｓｅＡｃａ...     

ELECTROCHEMICAL DETERMINATION OF CURRENT EFFICIENCY IN ALUMINIUM ELECTROLYSIS

ＥＬＥＣＴＲＯＣＨＥＭＩＣＡＬＤＥＴＥＲＭＩＮＡＴＩＯＮＯＦＣＵＲＲＥＮＴＥＦＦＩＣＩＥＮＣＹＩＮＡＬＵＭＩＮＩＵＭＥＬＥＣＴＲＯＬＹＳＩＳＴｉｅ；Ｊｕｎ（ＭｅｔａｌｌｕｒｇｉｃａｌＥｎｇｉｎｅｅｒｉｎｇＩｎｓｔｉｔｕｔｅ，ＮｏｒｔｈＣｈｉｎａＵｎｉ...     

MEASUREMENT AND INFLUENCE FACTOR＇S ANALYSING OF INTERFACIAL STRENGTH OF COMPOSITES

ＭＥＡＳＵＲＥＭＥＮＴＡＮＤＩＮＦＬＵＥＮＣＥＦＡＣＴＯＲ＇ＳＡＮＡＬＹＳＩＮＧＯＦＩＮＴＥＲＦＡＣＩＡＬＳＴＲＥＮＧＴＨＯＦＣＯＭＰＯＳＩＴＥＳ￥ＷａｎｇＬｉｎｇｓｅｎ；ＬｉｕＲｕｏｙｕ；ＺａｎｇＪｉｎｓｅｎ；ＦａｎＹｉ（ＲｅｓｅａｒｃｈＩｎｓｔｉ...     

ANALYSIS OF DISSIPATIVE STRUCTURE IN MATERIAL COMMINUTION

ＡＮＡＬＹＳＩＳＯＦＤＩＳＳＩＰＡＴＩＶＥＳＴＲＵＣＴＵＲＥＩＮＭＡＴＥＲＩＡＬ　ＣＯＭＭＩＮＵＴＩＯＮＺｈａｎｇ；Ｚｈｉｔｉｅ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆＴｅ...     

The electrical potential difference across cracks in PZT measured by Kelvin Probe Microscopy and the implications for fracture

An indentation crack in a poled PZT ceramic subjected to an electric field is investigated using AFM and KFM to determine the crack opening displacement and the electrical potential difference across the crack. The experimental results are used to calculate the crack tip stress and dielectric displacement intensity factors and the crack tip energy release rate. From the applied electric field and the measured field interior to the crack, the dielectric constant of the crack interior is determined to be 40. The consequences of this permittivity on the crack tip energy release rate are illustrated for a Griffith crack. The theoretically predicted effect of an applied electric field in retarding crack growth decreases significantly with increasing permittivity. In practical situations in terms of crack length, applied load and electric field level, the retardation of crack growth is negligible when the dielectric constant of the crack interior is higher than 20.     

Local electric field investigation of Si2N2O and its electronic structure, elastic and optical properties

This paper demonstrates that the Clausius-Mosotti equation cannot be used for Si₂N₂O since the Lorenz approximation is invalid therein. Therefore a modified definition for the Lorenz electric field is suggested which can be derived from the optical dielectric constant calculated using the plane-wave pseudopotential method. In addition, other parameters of Si₂N₂O such as the energy band gap, density of states, elastic and optical properties are also given in this paper. Based on the new expression for local electric field, the modified Clausius-Mosotti equation is suggested, and then the dielectric constant of Si₂N₂O is discussed by using the additivity rule. It is found that the result of the phenomenological analysis of the dielectric constant is basically consistent with the experimental data and the first principles results, which explain the experimental observation that the dielectric constant of Si₂N₂O is enhanced with the increase of Li content. Also, the modified Clausius-Mosotti equation and the additivity rule are suggested to be used in predicting the dielectric behaviors of the new and complex compounds.     

Effects of CeO2 doping on the structure and properties of PSN-PZN-PMS-PZT piezoelectric ceramics

Quinary system piezoelectric ceramics PSN-PZN-PMS-PZT were prepared by using a two-step method. The effects of CeO2 doping on piezoelectric and dielectric properties of the system were investigated at morphotropic phase boundary （MPB）. The results reveal that the relative dielectric constant ε33^T｜ε0, the Curie temperature To, the piezoelectric constant d33, the mechanical quality factor Qm, and the electromechanical coupling coefficient Kp are changed with the increase of CeO2 content. On the other hand, the effects of CeO2 doping on the dielectric properties of PSN-PZN-PMS-PZT piezoelectric ceramics at high electric field are consistent with the change at weak electric field. The values of dielectric constant and dielectric loss are enhanced with the increasing of electric field.     

恒位移下BaTiO_3单晶在空气中亚临界裂纹扩展与畴变

用正交偏振光显微镜,通过原位观察研究了恒位移下BaTiO_3单晶贯穿裂纹快速扩展与畴变的关系,以及在室温空气中(湿度为35%RH)亚临界裂纹扩展和畴变的关系。结果显示,加载开始时首先出现畴变,且其体积分数随载荷升高而增大;当载荷达到临界值时,裂纹快速形核、扩展并止裂,在空气中保持恒位移,畴变能慢慢发生,即空气中水吸附能促进畴变,当畴变发展到临界条件时就引起裂纹的亚临界扩展(即应力腐蚀)。     

Analytical Modeling of Triple-Metal Hetero-Dielectric DG SON TFET

In this paper, a 2-D analytical model of triple-metal hetero-dielectric DG TFET is presented by combining the concepts of triple material gate engineering and hetero-dielectric engineering. Three metals with different work functions are used as both front- and back gate electrodes to modulate the barrier at source/channel and channel/drain interface. In addition to this, front gate dielectric consists of high-K HfO₂ at source end and low-K SiO₂ at drain side, whereas back gate dielectric is replaced by air to further improve the ON current of the device. Surface potential and electric field of the proposed device are formulated solving 2-D Poisson’s equation and Young’s approximation. Based on this electric field expression, tunneling current is obtained by using Kane’s model. Several device parameters are varied to examine the behavior of the proposed device. The analytical model is validated with TCAD simulation results for proving the accuracy of our proposed model.     

晶相组成对Si_3N_4陶瓷介电性能的影响

以MgO-Al_2O_3-SiO_2(MAS)体系作为烧结助剂,采用无压烧结,通过控制烧结工艺,制备出具有不同晶相组成的Si_3N_4陶瓷.研究了晶相组成对氮化硅陶瓷微波介电性能的影响.借助XRD、SEM对Si_3N_4陶瓷微观组织进行了研究.结果表明:在烧结过程中,有中间相Si_2N_2O产生;经1850 ℃、0.5 h烧结,β-Si_3N_4全部转变为具有较大长径比,显微结构均匀的长柱状β-Si_3N_4晶粒;Al~(3+)和O~(2-)能够进入β-Si_3N_4晶体内形成β-Si_(6-x)Al_xO_xN_(8-x)固溶体,使晶体内部产生较大的空隙或晶格畸变,在外电场作用下,易于产生离子位移极化,导致介电常数升高;同时,随着烧结温度的提高,存在于晶界的玻璃相含量增加,试样的介电常数随之升高.     

IN718合金增材制造温度场仿真及微观组织分析

针对微观组织的调控相关问题,构建了IN718材料激光选区熔化(selective laser melting,SLM)温度场仿真的三维有限元模型,研究了激光功率和扫描速度对熔池温度场和凝固机理的影响,进而预测增材制造材料的微观组织,为微观组织的调控提供理论依据。首先分析了激光功率和扫描速度对熔池尺寸的影响,分析了不同工艺参数下熔池温度场的变化;其次基于温度场的仿真结果,计算不同工艺参数下熔池固液界面处温度梯度和凝固速度的变化,分析凝固过程中柱状晶向等轴晶的转变条件,预测熔池不同深度上的微观组织。研究结果发现提高激光功率有利于等轴晶的形成,而扫描速度对等轴晶厚度占比影响不大,另外降低激光功率和提高扫描速度将促使形成的微观组织尺寸更细小。     

氧化铝掺杂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3陶瓷介电性能的影响

Zr4+取代Ti4+的Ba0.6Sr0.4(Zr0.2Ti0.8)O3固溶体在降低介电常数的同时,保持了BST固溶体优异的可调性。为降低BST材料的介电损耗和介电常数,以氧化铝为改性剂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3材料(BSZT材料)进行了掺杂。随着氧化铝掺杂质量分数从1%到10%增加,BSZT材料的介电常数从5000降低到了1550(100kHz),介电损耗降低到0.001(100kHz)以下,而材料的介电可调性保持在35%左右(1.5kV/mm)。X射线衍射图谱表明,烧结后得到的BSZT材料具有典型的钙钛矿结构。扫描电子显微镜观察表明,氧化铝的掺杂使得陶瓷致密度较高,晶粒均匀。     

First principle study of electronic and optical properties of planar GeC,SnC and SiC nanosheets

The electronic structures and optical properties of XC (X = Ge, Sn, Si) nanosheets are investigated in the present study using the full potential linearized augment plane wave (FP-LAPW) technique based on the first principles density-functional theory (DFT). Using the calculated dielectric function within the random phase approximation (RPA), the reflectivity, absorption coefficient, energy-loss function and refraction index of these nanosheets for parallel and perpendicular electric field polarizations are well described. Our electronic structure calculations for XC (X = Ge, Sn, Si) nanosheets confirmed the semiconductor property of these compounds. To ensure the accuracy of our work, we have also calculated the energy gap and optical constants of XC (X = Ge, Sn, Si) bulks in Zinc-blende structure and compared our obtained results with the previous works. The results of our comparison study show that the values of static refractive index and static dielectric constant for XC (X = Ge, Sn, Si) nanosheets in a parallel electric field polarization are greater than those in a perpendicular electric field polarization.     

SOLIDIFICATION OF NICKEL-BASED SINGLE CRYSTAL SUPERALLOY BY ELECTRIC FIELD

The crystal growth of a nickel-based single crystal superalloy DD3 was researched via controlled directional solidification under the action of a DC electric field. The cellular or dendrite spacing of the single crystal superalloy is refined and microsegregation of alloying elements Al, Ti, Mo and W, is reduced by the electric field. The electric field decreases the interface stability and reduces the critical growth rate of the ceUular-dendritic translation because of Thomson effect and Joule heating. The precipitation of the γ＇ phase is more uniform and the size of the γ＇ phase is smaller with the electric field than that without the electric field.