Annihilation of deformation-produced vacancy clusters in alkali halides at room temperature

The aging of plastically deformed crystals of NaCl and KCl at room temperature for a long time results in a bulk density increase as evidenced by thermal gradient flotation measurements. The effect is explained by the annihilation of deformation-induced clusters on dislocations. No density variation was found in LiF and NaF crystals. A model has been suggested for the formation of vacancy clusters by disrupture of unrelaxed dislocation dipoles. From the model it follows that cluster size and mobility should decrease in the homologic row of alkali halides, which is consistent with experimental evidence. The cluster diffusion coefficient has been estimated to be 10^?16 cm²s^?1 at room temperature.     

Precursor compound enabled formation of aqueous-phase CdSe magic-size clusters at room temperature

The formation pathway of aqueous-phase colloidal semiconductor magic-size clusters(MSCs)remains unrevealed.In the present work,we demonstrate,for the first time...     

Magnetic excitations of rare Earth atoms and clusters on metallic surfaces

Magnetic anisotropy and magnetization dynamics of rare earth Gd atoms and dimers on Pt(111) and Cu(111) were investigated with inelastic tunneling spectroscopy. The spin excitation spectra reveal that giant magnetic anisotropies and lifetimes of the excited states of Gd are nearly independent of the supporting surfaces and the cluster size. In combination with theoretical calculations, we argue that the observed features are caused by strongly localized character of 4f electrons in Gd atoms and clusters.     

Patterning of sub-1 nm dangling-bond lines with atomic precision alignment on H:Si(100) surface at room temperature

We have patterned sub-1 nm dangling-bond (DB) lines on a H-terminated Si(100)-2 × 1 surface aligned with atomic precision at room temperature using a scanning tunneling microscope (STM) to controllably desorb hydrogen atoms from a H:Si(100) surface. In order to achieve continuous and aligned DB lines, we have performed a detailed investigation of the effects of patterning parameters such as the writing voltage, writing current and electron dosage, as well as STM tip apex geometry on the fabrication and alignment of Si DB lines. We show that there exists an optimum set of patterning parameters which enables us to obtain near-perfect Si DB lines and align them with near atomic precision in a highly controllable manner. In addition, our results indicate that the pattern quality is weakly dependent on the STM tip apex quality when the patterning parameters are within the optimum parameter space.     

金属夏比缺口(V型)室温冲击试验检测结果不确定度的评定

介绍了测量不确定度在金属夏比（V型缺口）室温冲击试验中的应用，并对影响冲击试验结果的测量不确定度做了详细评定，从试样的形状和尺寸、缺口底部的光洁度、冲击试验机、试验温度、检查试样尺寸量具的最小分度值五方面分析了不确定度的来源，对各分量进行了计算、合成并作出评定。     

室温下介孔分子筛MCM-41的合成与表征

在室温下 ,以十六烷基三甲基溴化铵 (CTABr)为模板剂 ,正硅酸乙酯和水玻璃为硅源 ,通过水热法分别合成出了性能优良的介孔分子筛MCM 4 1,并采用XRD、N2 吸附脱附、FTIR、SEM、热重等手段对合成的样品进行了分析表征。其结果表明 ,合成的固体产物具有MCM 4 1特有的六方排列的孔道结构 ,并且具有较高的有序度、比表面积、孔容和热稳定性     

Deposition of size-selected metal clusters generated by magnetron sputtering and gas condensation: a progress review

This paper presents a topical review of the production and deposition of size-selected metal clusters generated by magnetron sputtering and gas condensation. Clusters with up to 75,000 atoms can be obtained by controlling the gas pressure in the sputtering source, prior to size selection with a novel (time-of-flight) mass filter. The clusters are deposited on the model graphite substrate to study the cluster-surface interaction. Two regimes for cluster deposition have been identified at elevated impact energies: (i) 'pinning' (ca. 10 eV per atom) and (ii) implantation (ca. 100 eV per atom). Of particular importance is the pinning regime, since this allows the fabrication of monodispersed cluster arrays, which are stable against diffusion at room temperature (and above). The deposition of size-selected metal clusters represents a novel method of preparing surface nanostructures, with potential applications including model catalyst studies and the immobilization of biological molecules.     

On the possibility of ferromagnetism in CdO:Mn at room temperature

Nanocrystalline samples of Cd_{1? x} Mn _x O (x?=?0.00, 0.02, 0.04 and 0.06) were synthesised by sol–gel method and characterised by X-ray diffraction, Faraday's rotation, Guoy's method and electron paramagnetic resonance (EPR) at room temperature (RT). Results reveal that ferromagnetism at RT for Mn-doped CdO nanoparticles is possible.     

Microplasticity at room temperature of single-crystal titanium carbide with different stoichiometry

Single crystals of titanium carbide with a C-to-Ti range of 0.64 to 0.99 were plastically deformed at room temperature with a hardness indenter and a drill. The operating slip systems were determined by hardness anisotropy and transmission electron microscopy. The results were characteristic for bulk material deformation of TiC, below, as well as above, the brittle-to-ductile transition temperature. A typical low temperature behaviour is the formation of cracks and dislocation motion along the slip systems {1 1 0} 〈1 1 0〉 and {1 0 0} 〈1 1 0〉, which are both common in the rock-salt structure. The high temperature deformation is characterized by the slip system {1 1 1} 〈1 1 0〉. The degree of plastic deformation and the importance of the slip system {1 1 1} 〈1 1 0〉 increases as the C-to-Ti ratio decreases from 0.99 to 0.64.     

The facile synthesis of PbS cubes and Bi2S3 nanoflowers from molecular precursors at room temperature

PbS and Bi₂S₃ nanocrystals with well-controlled sizes and shapes were easily produced from molecular precursors (xanthate) in ethylene diamine (en) solution at room temperature. When lead or bismuth ethylxanthate were added into en solution, the precipitates were instantly formed, and subsequently, PbS cubes and flower-like Bi₂S₃ hierarchical structures were obtained if the mixtures were left still for 5 days under ambient conditions. This work not only provides a facile route to synthesize chalcogenides with well-defined nano- and microstructures in a solution-phase system, but also gives insight into understanding on decomposition behavior of molecular precursors in various solvents.     

常温生长类金刚石薄膜的实验研究

利用射频等离子体增强化学气相沉积(RFPECVD)工艺在常温下实现在不锈钢、硅片、玻璃等基底上大面积沉积类金刚石(DLC)膜.薄膜表面光滑致密,与衬底的结合力较高.用Raman,FTIR,SEM,EDX研究了薄膜的形貌、结构与组分.用栓-盘摩擦磨损试验机测试了薄膜的摩擦系数.通过优化沉积参数,所沉积的DLC膜在与100Cr6钢球对磨时摩擦系数低于0.01.在摩擦过程中DLC膜的磨损机制借助SEM进行了研究.     

Observations of p-type semiconductivity in titanium dioxide at room temperature

Titanium dioxide (TiO₂) is widely considered to be a strongly n-type semiconductor due to its tendency for oxygen deficiency. In this work, however, room temperature p-type semiconductivity has been observed in rutile TiO₂, as determined using surface photovoltage spectroscopy and cyclic voltammetry subsequent to controlled processing at elevated temperatures. In particular, room temperature p-type semiconductivity has been imposed via strong oxidation [p(O₂) = 75 kPa] at elevated temperatures (1273 K), followed by rapid cooling in the same gas phase. It is reasoned that under such conditions, the observed p-type behaviour is due to the formation of titanium vacancies (acceptor-type ionic defects) at the TiO₂ surface. It is also concluded that the extremely slow diffusion kinetics of these defects towards the bulk is what limits the p-type behaviour to the surface and near surface regions. Nevertheless, this could be overcome by applying appropriately lengthy annealing times. The reported observation of p-type semiconductivity in TiO₂ is expected to have far reaching consequences for this intensely researched material.     

Crack resistance curves of alumina and zirconia at room temperature

Ceramic three-point bend specimens were pre-cracked in a displacement-controlled test in air at room temperature to form sharp cracks of different lengths. Critical stress intensity factors (K _IC were then measured as a function of sharp crack length in a fast-fracture, load-controlled test. Crack resistance curves (K _IC against crack length) were determined for three commercially pure aluminas of different grain size, a debased alumina containing a glassy phase, and a partially stabilized zirconia (PSZ) material. The crack resistance curves proved to be flat for the finer-grained and the debased alumina. A steeply rising crack resistance curve was, however, observed for a pure coarse-grained alumina material which is explained by friction effects of the cracked microstructure behind the measured crack front. The effect is influenced by the test procedure itself. Though crack branching takes place the crack resistance curve of PSZ is completely flat, which is attributed to fast fracture testing where only the most dangerous flaw is activated.     

Thin film interdiffusion of Au and In at room temperature

Results on the thin film interdiffusion of Au and In at room temperature are presented. Indium films 56–3000 Å thick were deposited by vacuum evaporation onto previously deposited gold films of thicknesses ranging from 200 to 1600 Å. The interdiffusion of Au and In occurs quickly at room temperature and the intermetallic compounds AuIn₂, AuIn, Au₇In₃ and Au₄In are formed. Which compound will be formed depends on the Au:In ratio in the layer and on the diffusion time.     

Interdiffusion and phase formation at room temperature in evaporated gold-tin films

Interdiffusion at room temperature in evaporated Au-Sn films was studied by the in situ backscattering of 2.0 MeV ⁴He ions. The interdiffusion resulted in the formation and growth of an AuSn phase region. The growth of the phase followed a parabolic growth rate law, and the growth rate constant was found to be about 9 × 10^?15 cm²s^?1 at room temperature.     

Transistor effects and in situ STM of redox molecules at room temperature

Inorganic transition metal complexes were identified as potential candidates for transistor-like behavior in an electrochemical scanning tunnelling microscope (STM) configuration at room temperature. The theoretical background has been established based on condensed matter charge transfer theory. It predicts a distinct increase of the tunnelling current close to the equilibrium potential, i.e., if molecular bridge states are tuned into resonance with the Fermi levels of the enclosing electrodes. The complexes display robust electrochemistry on Au(111) electrode surfaces. STM images at molecular resolution reveal detailed information on their surface structure and scanning tunnelling spectroscopy experiments have shown clear evidence of transistor-like behavior.     

Near-threshold fatigue crack growth at room temperature and an elevated temperature in Al---Li alloy 8090

The effects of slip distribution and crack tip shielding mechanisms on the near-threshold fatigue crack growth of the Al---Li alloy 8090 have been studied at both room temperature and an elevated temperature. The slip distribution has been varied by changing the distribution of the S phase, through prior stretching or by means of a duplex heat treatment. Fatigue crack growth (FCG) tests were conducted at a high stress ratio to reduce possible effects due to crack closure.

At room temperature the changes in FCG rates are interpreted as arising from the changes in the degree of planarity of slip in the materials.

At 150°C, the microstructural changes due to the long exposure to elevated temperature appear to dominate the effects observed. At lower ΔK, where the time at temperature is greatest, lower ΔK thresholds than those found at room temperature are obtained. These have been attributed to increased slip homogenization due to the increased precipitation and coarsening of the incoherent S phase together with loss of toughness due to the growth of coarse grain boundary phases and the formation of the associated δ′ precipitate free zone.

At higher ΔK, where the time at temperature is low and microstructural changes are minimal, slower FCG rates than those found at room temperature are obtaine. These are explained in terms of increased crack tip shielding which arises because of the increase in tortuosity of the crack path, the increased slip homogenization and the climb and cross-slip within the crack tip plastic zone.