The OFF to ON switching time and ON state consolidation in write-once-read-many-times memory devices based on doped and undoped carbon-sphere/polymer composites

We investigate the write operation in memory devices prepared using thin films of carbon spheres and cross-linked poly(4-vinylphenol) composites. Three types of carbon-spheres (N-doped, B-modified and undoped spheres) are used and their influence on memory characteristics is discussed. These memory devices show write-once-read-many-times (WORM) characteristics with an OFF to ON (high resistance to low resistance) transition at low voltages, of ca. 2 V. We investigate the ON-current, OFF-current and ON to OFF current ratio of devices prepared with composites of the three types of carbon spheres. The results are presented for devices prepared with three different carbon sphere concentration, for each carbon sphere type. The OFF to ON transition occurs in less than 1 μs and the ON-state in the best case is consolidated in less than 10 μs, for a write-operation voltage of 5 V.     

Tied-ridging and fertilizer use for sorghum production in semi-arid Ethiopia

Grain sorghum [Sorghum bicolor (L.) Moench] yield is often constrained by low soil water and nutrient availability in Ethiopia. The integration of tied-ridging for water conservation with fertilizer application in semi-arid sorghum production areas of northern and central Ethiopia was evaluated in five trials in 2005–2007. Three tillage practices and four fertilizer application treatments were evaluated in a complete factorial. The tillage practices included tied-ridging before (TR_br) and after (TR_r) the on-set of rains, and shilshalo, a traditional ridging practice for preventing runoff and controlling weeds practiced with the traditional oxen-drawn plow. The fertilizer treatments (N–P) were 0-0, 10-10, 22-0, and 32-10 kg ha⁻¹. Grain yield was increased over shilshalo with tied-ridging by 6–45%. Grain yield was increased by 26% with pre-plant application of N plus P and by 16% with side-dress N application in central Ethiopia, but yield was not increased in the northern Ethiopia trials. Tied-ridging did not increase the yield response to nutrient application. Tied-ridging before or after on-set of rains was found to be equally effective in increasing yields and should be considered for sorghum production in semi-arid areas of northern and central Ethiopia. Response to applied N and P was probably constrained by soil water deficits, even with tied-ridging and especially in the drier environments of northern Ethiopia. Application of N and P should be considered if mean yield levels are above 2.5 Mg ha⁻¹.     

Reaction to fire and water vapour resistance performance of treated wood specimens containing TiO2 and clay nanoparticles

The effect of TiO₂ and/or clay nanoparticles on water vapour permeability and the reaction to fire performance of coated and impregnated spruce wood were studied. Water vapour permeability properties were used to assess the moisture transfer properties and durability of the specimens using the cup test. The reaction to the early stage fire development properties of the specimens was analysed using a small scale cone calorimeter test. Comparisons between the different treated and untreated specimens on the moisture and reaction to fire performances were performed. The results revealed poor reaction to fire and water vapour resistance of specimens treated with TiO₂ and/or clay nanoparticles containing treatments. Copyright © 2013 John Wiley & Sons, Ltd.     

低温时效对Fe-22Al合金微观组织和力学性能的影响

利用金相显微镜、XRD、TEM和力学性能测试方法研究了低温时效对Fe-22Al合金的微观组织和力学性能的影响。结果表明,Fe-22Al合金经退火和固溶处理后的金相组织为粗大的等轴状晶粒,但固溶处理后晶粒尺寸有所减小。合金主要的相组成为α-Fe相以及具有B2结构的FeAl相,不存在DO3结构的Fe3Al相。存在明显的基体衍射斑点和(100)超点阵斑点意味着发生失稳有序化转变,并形成大量B2结构的有序相。暗场像结果表明存在大量Al原子的富集区和贫集区,即合金中发生了调幅分解转变。经过530℃时效处理后,合金的衍射斑点中同时存在DO3结构和B2结构的超点阵斑点。随时效的进行,逐渐发生B2→DO3相变,在B2结构的有序相内部形成大量细小的DO3相,并逐渐长大和粗化,最终形成粗大的海绵状结构。经过固溶和时效处理后,Fe-22Al合金的硬度和抗压强度分别为359HV、1610 MPa。     

Polymer composite of poly(vinyl phenol)-reduced graphene oxide reduced by vitamin C in low energy consuming write-once–read-many times memory devices

We report the application of reduced graphene oxide, using vitamin C as reducing agent, to make a composite with poly(vinyl phenol) as the active layer of write-once–read-many times memory devices. These devices present a high ON/OFF current ratio of 10⁵ when read at 1 V, retain the information for a long time maintaining the ON/OFF current ratio constant, and require low energy for performing at 5 V the memory write (less than 10^?8 J cm^?2 device active area) and read operations.     

Microstructural characteristics of in situ Mg2Si/ Al-Si composite by low superheat pouring

To control the morphology and size of the primary and eutectic Mg2Si phases in in situ Mg2Si/Al-Si composite and achieve a feasible and reliable technique to produce appropriate feedstock for the thixo-casting and rheo-casting of this type of material, three AI-Si matrix composites reinforced by 5wt.%, 9wt.% and 17wt.% Mg2Si with hypoeutectic, eutectic and hypereutectic compositions were prepared by the low superheat pouring （LSP） process. The effects of the pouring temperature （superheat） on the morphology and size distribution of primary phases （primary e-AI and Mg2Si）, binary （a-AI ＋ Mg2Si） eutectic cell and eutectic Mg2Si were investigated. The experimental results show that low pouring temperature （superheat） not only refines the grain structure of the primary e-AI and binary （e-AI ＋ Mg2Si） eutectic cell in three composites and promotes the formation of more non- dendritic structural semi-solid metal （SSM） slurry of these phases; but also refines the primary and eutectic Mg2Si phases, which seems to be attributed to the creation of an ideal condition for the nucleation and the acquisition of a high survival of nuclei caused by the LSP process.     

原位β-Zr相/Zr非晶基复合材料的干摩擦滑动磨损行为

采用铜模喷铸法制备出直径为3 mm的原位β-Zr相/Zr非晶基复合材料,对其在干摩擦条件下的滑动磨损行为进行了研究。结果表明,与纯块状非晶合金相比,Zr基块状非晶复合材料的耐磨性能得到明显的改善。复合材料比纯块状非晶合金具有更低的摩擦系数和磨损速度,最低的磨损速度比纯非晶合金的减小48.1%。同时,包含一定体积分数β-Zr相的复合材料表面磨损比纯非晶合金的轻,只有一些浅的犁沟,其磨削小,显示出轻微的磨粒磨损特征,而纯非晶合金的磨损表面呈现出片状、分层、凸起及深的犁沟等特征,磨削大,为严重的磨粒磨损。复合材料低的磨损速度归因于铸态下析出的分布在非晶基体上的韧性β-Zr枝晶相的存在。该相具有较强的承载、塑性变形和加工硬化能力,通过减小界面处非晶基体的应力集中、释放应变能、限制剪切带和裂纹的萌生与扩展、使塑性变形更加均匀等途径提高耐磨性能。     

PHASE TRANSFORMATION UNIT OF BAINITIC FERRITE AND ITS SURFACE RELIEF IN LOW AND MEDIUM CARBON ALLOY STEELS

The lath-or plate-shaped bainitic ferrite of low and medium carbon alloy steels consists ofpackets of ferrite sublaths which are composed of many finer and regular ferrite blocks.Theyare uniform shear growth units of bainitic phase transformation.No carbide is precipitatedfrom them.The bainitic O-carbides are precipitated from γ-α interface or carbon-richaustenite.The mode of arrangement of the units in ferrite sublath packet is in uni-or bi-di-rection.Single surface relief is produced by the accumulation of uniform shear strains with allthe ferrite units arranged unidirectionally in a sublath packet,while tent-shaped surface reliefis formed by the integration of the uniform shear strains of two groups with ferrite units pilingup in two directions and growing face to face;whereas if they grow back to back,the integra-tion will be responsible for invert-tent-shaped surface relief.The interface trace between twogroups of ferrite units in a sublath packet is shown as“midrib”.