Mn implanted GaAs by low energy ion beam deposition

High dose Mn was implanted into semi-insulating GaAs substrate to fabricate embedded ferromagnetic Mn-Ga binary particles by mass-analyzed dual ion beam deposit system at room temperature. The properties of as-implanted and annealed samples were measured with X-ray diffraction, high-resolution X-ray diffraction to characterize the structural changes. New phase formed after high temperature annealing. Sample surface image was observed with atomic force microscopy. All the samples showed ferromagnetic behaviour at room temperature. There were some differences between the hysteresis loops of as-implanted and annealed samples as well as the cluster size of the latter was much larger than that of the former through the surface morphology. (C) 2004 Elsevier B.V. All rights reserved.

I. Reactively sputtered Ti-Si-N thin films for diffusion barrier applications. II. Oxidation, diffusion and crystallization of an amorphous Zr_(60)Al_(15)Ni_(25) alloy.

Films of Ti-Si-N obtained by reactively sputtering a TiSi_2, a Ti_5Si_3, or a Ti_3Si target are either amorphous or nanocrystalline in structure. The atomic density of some films exceeds 10^23 at./cm^3. The room-temperature resistivity of the films increases with the Si and the N content. A thermal treatment in vacuum at 700 °C for 1 hour decreases the resistivity of the Ti-rich films deposited from the Ti_5Si_3 or the Ti_3Si target, but increases that of the Si-rich films deposited from the TiSi_2 target when the nitrogen content exceeds about 30 at. %.

Ti_(34)Si_(23)N_(43) deposited from the Ti_5Si_3 target is an excellent diffusion barrier between Si and Cu. This film is a mixture of nanocrystalline TiN and amorphous SiN_x. Resistivity measurement from 80 K to 1073 K reveals that this film is electrically semiconductor-like as-deposited, and that it becomes metal-like after an hour annealing at 1000 °C in vacuum. A film of about 100 nm thick, with a resistivity of 660 µΩcm, maintains the stability of Si n+p shallow junction diodes with a 400 nm Cu overlayer up to 850 °C upon 30 min vacuum annealing. When used between Si and Al, the maximum temperature of stability is 550 °C for 30 min. This film can be etched in a CF_4/O_2 plasma.

The amorphous ternary metallic alloy Zr_(60)Al_(15)Ni_(25) was oxidized in dry oxygen in the temperature range 310 °C to 410 °C. Rutherford backscattering and cross-sectional transmission electron microscopy studies suggest that during this treatment an amorphous layer of zirconium-aluminum-oxide is formed at the surface. Nickel is depleted from the oxide and enriched in the amorphous alloy below the oxide/alloy interface. The oxide layer thickness grows parabolically with the annealing duration, with a transport constant of 2.8x10^(-5) m^2/s x exp(-1.7 eV/kT). The oxidation rate is most likely controlled by the Ni diffusion in the amorphous alloy.

At later stages of the oxidation process, precipitates of nanocrystalline ZrO_2 appear in the oxide near the interface. Finally, two intermetallic phases nucleate and grow simultaneously in the alloy, one at the interface and one within the alloy.

Mn implanted GaAs by low energy ion beam deposition

High dose Mn was implanted into semi-insulating GaAs substrate to fabricate embedded ferromagnetic Mn-Ga binary particles by mass-analyzed dual ion beam deposit system at room temperature. The properties of as-implanted and annealed samples were measured with X-ray diffraction, high-resolution X-ray diffraction to characterize the structural changes. New phase formed after high temperature annealing. Sample surface image was observed with atomic force microscopy. All the samples showed ferromagnetic behaviour at room temperature. There were some differences between the hysteresis loops of as-implanted and annealed samples as well as the cluster size of the latter was much larger than that of the former through the surface morphology. (C) 2004 Elsevier B.V. All rights reserved.

广西贺县龙水金矿床的同位素地球化学研究及成因探讨

广西贺县龙水金矿位于湘桂稳定区，桂粤交界山脉的北段，博白-茶陵深断裂的西侧，区内广泛发育加里东期到燕山期的花岗岩，出露的基底地层主要为震旦系到寒武系。本文主要研究龙水金矿II号矿化带。该带位于寒武系水口群清溪亚群和大宁花岗闪长岩体的接触带附近，围岩为寒武系的碳质板岩，矿脉为硫化物石英脉，主要有黄铁矿、方铅矿、闪锌矿和石英等矿物。金矿化与硫化物密切相关。主要的金矿物为银金矿，少许自然金。确定金矿床的成矿年龄一直是个比较刺手的问题。本文选择矿脉中信为是成矿期的石英作为Rb-Sr等时年龄测定的对象，是基于其纯净和其中的原生气液包体基本可代表成矿热液的特征。结果表明其Rb-Sr等时年龄为120.5Ma，并认为此年龄代表了成矿年龄。有石英Rb-Sr等时线的~(87)Sr/~(86)Sr初始比为0.732089, 与矿脉中碳酸相加矿物的Sr同位素比值（约为0.7337-0.7402）一起，表明Sr应是来自地壳的富Rb盐矿物的Sr源区。另外，为了与围岩的蚀变年龄对比，测定了近矿围岩的Rb、Sr同位素组成，结果形成两条等时线，年龄分别为245.9 Ma和173.6 Ma，表明成矿以前至少发生了两次地质事件，导致了Sr同位素的均一化。这两次地质事件分别与华南的东吴运动及燕山运动第一幕相对应。矿石Pb同位素的~(206)Pb/~(204)Pb、 ~(207)Pb/~(204)Pb 和~(208)Pb/~(204)Pb 分别在18.4-18.9、15.6-16.1和38.4-39.6的范围内，并在~(207)Pb/~(204)Pb vs ~(206)Pb/~(204)Pb坐标图上呈现出斜率为1左右的线性排布。只有个别数据点要以得出依据Doe模式的模式年龄，约为200 Ma。在Zart,am Pb构造模式中，矿石Pb同位素数据大部分位于上地壳Pb线以上，呈现出富放射性成因Pb的特征。为了解释异常Pb的成因，本文进行了定量计算。结果表明矿石Pb为古老的存留地壳Pb与少地幔源Pb的混合，即矿石Pb同位素经历了这样的演化过程：在39-29.8亿年间由地幔分异出的地壳 Pb，未参与壳幔循环作用，一直到燕山期，与少量幔源Pb混合，并加入成矿。混合μ值为9.85-10.22。矿石的地质情况及矿石Pb同位素的Δα-Δβ-Δγ示踪结果均支持这一结论。本文初次研究了脉石英中的U、Pb同位素组成。脉石英中Ｕ含量很低。Pb同位素组成基本可以划分为两组，一组为与方铅矿数据近似的普通Pb组成，另一组则较富放射性成因Pb，并向围岩的Pb同位素组成漂移，可能是随着热液的演化和大气降水的加入，受围岩Pb的影响所致。矿脉中硫化物样品的S同位素比值（加权平均为0.16‰）和碳酸盐矿物样品的C同位素比值（在-0.1～-4.1‰的范围内），表明其应为内生来源。根据脉石英的气液包体均一温度（180-250 ），计算与脉石英存在0同位素平衡的热液的同位素的同位素组成，结果为1.2～-4.8‰，表明有大气降水的参与。石英气液包体水溶液为弱碱性，其成分分析表明其中K_2O/Na_2和CaO/MgO（分别根据K~+/Na~+和Ca~(2+)/Mg~(2+)的换算）与围岩相差很大。另外，矿石中微量元素主要为Au、A2g、Cu、Pb、Zn、Co、Ni、Mo、Bi、Ga、As、Sb、和Hg，而围岩中微量元素则主要为Cu、Ni、Mn、V、Zr、Ti、Cr和Ba。因此，热液中成矿元素主要不是来自围岩。黄铁矿的Co/Ni、S/Se/的比值可以指示热液化的来源。龙水金矿矿脉中黄铁矿的Co/Ni > 1，S/Se < 15000，均在与岩浆作用有关的热液范围内。因此，热液活动应主要与岩浆岩有关。矿石、围岩和花岗闪长岩的稀土配分模式相似，均呈现向右倾斜的V字型，并且类似于太古代后沉积岩。结合Pb、Sr同位素的研究，推测花岗闪长岩的源岩主要为古老的地壳物质。概括起来，龙水金矿床为约120.5 Ma形成的中低温热液矿床；热液中成矿物质主要来自花岗闪长岩。由于围岩与矿床紧密的空间联系及围岩中的高Au含量，围岩可能提供了一部分Au及其他成矿物质。

Effect of post-weld-annealing on the tensile deformation characteristics of laser-welded NiTi thin foil

Laser welding is an important process for fabricating complex components involving NiTi shape memory
alloy. As welding is a thermal process, the amount of heat input and the rate of cooling have significant
impact on the microstructure and hence the resultant characteristics of NiTi. In this study, the effect of
laser welding and post-weld-annealing from 573 K to 1173 K on the thermal phase transformation behaviors,
tensile deformation and micro-hardness characteristics of the laser-welded NiTi thin foils were investigated.
It was found that the as-welded sample exhibited inferior super-elasticity compared to the base
material, and the super-elasticity could be partially restored by annealing at 573 K. On the other hand,
annealing of the weldment above the recrystallization temperature would lower the super-elasticity.

Evaluation of Corrosion Fatigue Behaviour of Laser-welded NiTi Alloys using Bending Rotation Fatigue Test in Simulated Body Fluid

Shape memory NiTi alloys have been used extensively for medical device applications such as orthopedic, dental, vascular and cardiovascular devices on account of their unique shape memory effect (SME) and super-elasticity (SE). Laser welding is found to be the most suitable method used to fabricate NiTi-based medical components. However, the performance of laser-welded NiTi alloys under corrosive environments is not fully understood and a specific focus on understanding the corrosion fatigue behaviour is not evident in the literature. This study reveals a comparison of corrosion fatigue behaviour of laser-welded and bare NiTi alloys using bending rotation fatigue (BRF) test which was integrated with a specifically designed corrosion cell. The testing environment was Hanks’ solution (simulated body fluid) at 37.5oC. Electrochemical impedance spectroscopic (EIS) measurement was carried out to monitor the change of corrosion resistance at different periods during the BRF test. Experiments indicate that the laser-welded NiTi alloy would be more susceptible to the corrosion fatigue attack than the bare NiTi alloy. This finding can serve as a benchmark for the product designers and engineers to determine the factor of safety of NiTi medical devices fabricated using laser welding.

Effects of alloying elements on the cytotoxic response of titanium alloys

Titanium alloys, alloys, especially beta-type alloys containing beta-stabilizing elements, constitute a highly versatile category of metallic materials that have been under constant development for application in orthopedics and dentistry. This type of alloy generally presents a high mechanical strength-to-weight ratio, excellent corrosion resistance and low elastic modulus. The purpose of this study is to evaluate the cytotoxicity and adhesion of fibroblast cells on titanium alloy substrates containing Nb, Ta, Zr, Cu, Sn and Mo alloying elements. Cells cultured on polystyrene were used as controls. In vitro results with Vero cells demonstrated that the tested materials, except Cu-based alloy, presented high viability in short-term testing. Adhesion of cells cultured on disks showed no differences between the materials and reference except for the Ti-Cu alloy, which showed reduced adhesion attributed to poor metabolic activity. Titanium alloys with the addition of Nb, Ta, Zr, Sn and Mo elements show a promising potential for biomedical applications. (C) 2011 Elsevier B.V. All rights reserved.

Effect of the Oxygen on the Mechanical Properties of Ti-Mo Systems Alloys

Titanium alloys normally contain oxygen, nitrogen, or carbon as impurities, and although this concentration is low, these impurities cause changes in the mechanical properties of Ti alloys. Oxygen is a strong alpha-phase stabilizer and its addition causes solid-solution strengthening, shape memory effect, and superelasticity. The most promising alloys are those with Nb, Zr, Ta, and Mo as alloying elements. In this paper, the preparation, processing, and characterization of Ti-Mo alloys (5 and 10 wt%) used as biomaterials are presented, along with the influence of oxygen on their mechanical properties. The addition of oxygen causes an increase in the elasticity modulus of the Ti-5Mo alloy due to an increase in the alpha' phase volume fraction, which possesses a higher modulus than the alpha '' phase. Ti-10Mo possesses a mixture between alpha '' and beta phases, oxygen enters these two structures and causes a dominating effect.

Variabilidade espacial e sazonal da concentração de elementos-traço em sedimentos do sistema estuarino de Santos-Cubatão (SP)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A NEW CU-BASED SMA WITH EXTREMELY HIGH MARTENSITIC-TRANSFORMATION TEMPERATURES

A new series of high temperature copper based shape memory alloys has recently been patented. These alloys contain 8-20 wt% Al, 1-20 wt% Ag, 0-2 wt% of a minor element (preferably Co), balance copper. The martensitic start transformation temperatures of these alloys are above 200 degrees C and, in some cases, they have good high temperature stability and may be useful in commercial applications where higher operating temperatures than those obtained from Cu-Zn-Al and Cu-Al-Ni shape memory alloys are required.

Controle nebuloso aplicado em asas adaptativas utilizando ligas de memória de forma

Pós-graduação em Engenharia Mecânica - FEIS

Description and geochemistry of DSDP Leg 55 Holes

One of the objectives of Leg 55 was to investigate the Tertiary history of sedimentation and environment on the Emperor Seamounts after their volcanic activity. For the three first sites, 430, 431, and 432, drilled on Ojin, Nintoku, and Yömei Seamounts, the Neogene sedimentary deposits are not well represented and are not typical pelagic sediments. Except for two holes (430A and 432), where we found calcareous oozes, the sediments are heterogeneous sands, gravels, and pebbly mudstones with a wide range in grain size and composition. Two phenomena characterize these deposits: the inheritance of volcaniclastic material and its alteration, and the authigenesis of secondary minerals including silicates, phosphates, and ferromanganese oxides formed under volcanic influence in a marine environment.

Annotated record and illustrations of Mn nodules retrieved during cruise KH-73-4 of the R/V Hakuho Maru and cruises GH76-1 and GH77-1 of the R/V Hakurei Maru

Deep sea manganese nodules from the Central Pacific Basin are mainly composed of 10Å manganite and d-MnO2 Two zones equivalent to the minerals are evidently distinguishable according to their optical properties. Microscopic and microprobe analyses revealed quite different chemical compositions and textnral characteristics of the two zones. These different feature of the two zones of nodules suggest the different conditions under which they were formed. Concentrations of 11 metal elements in the zones and inter-element relationships show that the 10Å manganite zone is a monomineralic oxide phase containing a large amount of manganese and minor amounts of useful metals, and that the d-MnO2 zone which is apparently homogeneous under the microscope is a mixture of three or more different minerals. The chemical characteristics of the two zones can explain the variation of bulk composition of deep sea manganese nodules and inter-element relationships previously reported, suggesting that the bulk compositions are attributable to the mixing of the 10Å manganite and d-MnO2 zones in various ratios. Characteristic morphology and surface structure of some types of nodules and their relationships to chemistry are also attribut able to the textural and chemical features of the above mentioned two phases. Synthesis of hydrated manganese oxides was carried out in terms of the formation of manganese minerals in the ocean. The primary product which is an equivalent to d-MnO2 was precipitated from Mn 2+ -bearing alkaline solution under oxigenated condition by air bubbling at one atmospheric pressure and room temperature. The primary product was converted to a l0Å manganite equivalent by contact with Ni 2+, Cu 2++ or CO2+ chloride solutions. This reaction caused the decrease of Ni2+, Cu2+ or CO2+ concentrations and the increase of Na+ concentration in the solution. The reaction also proceeded even in diluted solutions of nickel chloride and resulted in a complete removal of Ni2+ from the solution. Reaction products were exclusively 10Å manganite equivalents and their chemical compositions were very similar to those of 10Å manganite in manganese nodules. The maximum value of(Cu+Ni+Co)/Mn ratio of 10Å manganite zones in manganese nodules is 0.16, and the Ni/Mn ratio of synthetic 10Å manganite ranges from 0.15 to 0.18 with the average of 0.167.

Sistema de instrumentação mecanizada Hyflex EDM

A Endodontia é uma área em constante evolução. Consideráveis desenvolvimentos nos materiais e técnicas têm sido essenciais para o melhoramento dos resultados nos tratamentos realizados. É exemplo disso mesmo a constituição dos instrumentos Endodônticos primordiais, construídos em cordas de piano, com evolução para aço de carbono, material este que sofria corrosão provocado pelo cloro presente no hipoclorito de sódio. O aço de carbono evoluiu para aço inoxidável e deste as limas endodônticas passaram a ser feitas em níquel-titânio, conferindo-lhes melhor flexibilidade e efeito de memória de forma. Mesmo com todas estas melhorias significativas, fraturas de instrumentos e erros durante a instrumentação continuam a acontecer e com eles veio a necessidade da pesquisa de possíveis melhorias da constituição das limas em NiTi. Como resultado surgiram ligas como o M-wire, fase-R e CM-wire, criadas a partir de tratamentos térmicos, que trouxeram às limas Endodônticas maior flexibilidade e resistência à fratura que os instrumentos feitos em NiTi convencional. A mais recente evolução das limas Ni-Ti, desenvolvida pela Coltene Whaldent (Allstätten, Suiça), são as limas Hyflex EDM, limas para canais radiculares de 5ª geração. O seu processo de fabrico por eletroerosão cria uma superfície única fazendo com que estas limas sejam mais duras e resistam mais à quebra, aliado à sua alta flexibilidade. É possível assim reduzir o número de limas para a limpeza e modelagem dos canais durante os tratamentos endodônticos sem comprometer a preservação da anatomia dos canais. As limas Hyflex EDM possuem, tal como as limas Hyflex CM, o efeito de controle de memória (CM), o que confere propriedades muito similares entre os dois sistemas.

Competing tetragonal and monoclinic phases in Ni2.2Mn0.80Ga

Temperature dependent synchrotron x-ray powder diffraction, differential scanning calorimetry, and magnetic measurements were performed on Ni2+xMn1-xGa (x=0.20 and 0.35) magnetic shape memory alloys. For x=0.20, though the monoclinic phase is thermodynamically stable, a trace of residual stress can stabilize a tetragonal phase. The residual-stress-induced tetragonal phase transforms to the cubic austenite phase over an unusually large temperature range (348 K < T < 693 K), suggesting extremely slow kinetics of transformation. In contrast to x=0.20, the thermodynamically stable phase of x=0.35 is tetragonal and this composition exhibits the usual features of a reversible martensitic transformation. The results suggest that for x=0.20 the monoclinic and tetragonal phases are nearly degenerate.