真空下非金属材料放气模型与研究综述

总结了放气研究在工业领域的各种应用．分析了真空环境下非金属材料放气的三种模型：Schram模型、扩散模型和基于马列夫理论吸附扩散模型。对国内外非金属材料放气的研究状况进行了论述。     

Synthesis of titanium oxide and titanium nitride nano-particles with narrow size distribution by supersonic thermal plasma expansion

The paper reports the synthesis of nano-crystalline ceramics like titanium dioxide and titanium nitride using a plasma chemical experimental reactor powered by a multi-segment (cascaded) arc plasma torch. The precursor-laden plasma beam emerging from the torch anode section expands supersonically through a converging nozzle to a low-pressure collection chamber. This results in a uniform and controlled gas dynamic quenching ensuring rapid synthesis of pure, un-coagulated free-flowing particles with a narrow size distribution. Simple Langmuir probes and calorimetric energy balance methods are used for plasma and reactor characterization, while X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), Raman and X-ray photoelectron spectroscopy (XPS) techniques have been used for product analysis. It is shown that size distribution of both the product particles is comparatively narrower than that found in most thermal plasma assisted laboratory synthesis studies. The expansion process was observed to produce a non-equilibrium electron population, which could charge up the particles after nucleation and hence could curb unwanted coagulation.     

A novel biomedical titanium alloy with high antibacterial property and low elastic modulus

β-type titanium alloys have attracted much attention as implant materials because of their low elastic modulus and high strength,which is closer to human bones and can avoid the problem of stress fielding and extend the lifetime of prosthetics.However,other issues,such as the infection or inflammation postimplantation,still trouble the titanium alloy's clinical application.In this paper,we developed a novel near β-titanium alloy (Ti-13Nb-13Zr-13Ag,TNZA) with low elastic modulus and strong antibacterial ability by the addition of Ag element followed by proper microstructure controlling,which could reduce the stress shielding and bacterial infections simultaneously.The microstructure,mechanical properties,corrosion resistance,antibacterial properties and cell toxicity were studied using SEM,electrochemical testing,mechanical test and cell tests.The results have demonstrated that TNZA alloy exhibited an elastic modulus of 75-87 GPa and a strong antibacterial ability (up to 98 ％ reduction) and good biocompatibility.Moreover,it was also shown that this alloy's corrosion resistance was better than that of Ti-13Nb-13Zr.All the results suggested that Ti-13Nb-13Zr-13Ag might be a competitive biomedical titanium alloy.     

新型纳米结构炭材料的储氢研究

氢能是一种清洁的可再生能源。由于传统的储氢材料和储氢技术达不到氢燃料电池电动车的实用要求,储氢问题已成为氢能应用中最急需解决的关键问题。近年来,各种新型纳米结构炭材料的储氢已成为国际上的一个研究热点,引起了人们的广泛关注。但在这一研究领域中一直存在着许多争议和很大的分歧。通过综述国内外近几年来各种新型纳米结构炭材料如单壁碳纳米管、多壁碳纳米管、石墨纳米纤维以及炭纳米纤维等的储氢研究进展,指出了这一领域中需要解决的问题如储氢测试方法的标准化、纳米结构炭材料的评价以及储氢机制和吸附位的研究等。     

基于阻尼材料拓扑分布的结构-声辐射优化

基于拓扑优化思想,提出一种人工材料假设,建立了阻尼材料铺设的拓扑优化数学模型。在阻尼材料用量一定的情况下实现阻尼材料最优分布,达到减振降噪之目的。采用遗传算法进行求解,进行了阻尼材料和人工材料的转换,实现了阻尼材料的拓扑优化。数值算例表明:所提方法在减振降噪设计中具有可行性和有效性,有较好的工程应用价值,可为阻尼材料的敷设提供一种可行有效的思路。     

Elastic property prediction by finite element analysis with random distribution of materials for heterogeneous solids

In the present paper, finite element method is employed to predict the effective material properties of heterogeneous materials via random distributions of the constituent materials. With the random distributing strategy, massive parametric analysis via finite element becomes feasible for multi-phase heterogeneous solids. Using a two-phase bi-continuous material as an example, the effects of the specimen size with respect to the characteristic size of the micro-structural size and the element density on the predicted effective properties are considered. The numerical predictions of the effective properties are checked by two analytical bounds which were proposed by Hashin and Shtrikemn (1963) through the principle of variation and the matrix-fiber model. Some discussions on the finite element prediction are also made to clarify the status of the present work in the composite mechanics research.     

Chemical modification of titanium immersed in hydrogen peroxide using nanosecond pulsed fiber laser irradiation

This paper addresses chemical alteration of titanium using pulsed Ytterbium fiber laser irradiation. For this study, Hydrogen Peroxide (HP) is used as the medium to study its effect on increasing anatase-titania composition in titanium substrates for samples irradiated by the laser. The variation of anatasei-rutile transformation generated in HP is compared with those generated in air. X-Ray diffraction (XRD) analysis suggests that three titanium dioxide structures - brookite, anatiase, and rutile - are present in the substrates irradiated by the laser beam. Additional peaks appeared in XRD results of HP immersed samples indicating that anatase and a rare titanium oxide structure, Hongquiite, are also produced, whereas these oxides are not detected in the samples generated in air. Energy-dispersive X-ray spectroscopy (EDAX) analysis reveals an increase of the oxide layer on the surface of HP-treated samples.     

Evaluation of the reactivity of titanium with mould materials during casting

A methodology for evaluating the reactivity of titanium with mould materials during casting has been developed. Microhardness profiles and analysis of oxygen contamination have provided an index for evaluation of the reactivity of titanium. Microhardness profile delineates two distinct regions, one of which is characterised by a low value of hardness which is invariant with distance. The reaction products are uniformly distributed in the metal in this region. The second is characterised by a sharp decrease in microhardness with distance from the metal-mould interface. It represents a diffusion zone for solutes that dissolve into titanium from the mould. The qualitative profiles for contaminants determined by scanning electron probe microanalyser and secondary ion mass spectroscopy in the as-cast titanium were found to be similar to that of microhardness, implying that microhardness can be considered as an index of the contamination resulting from metal-mould reaction.     

Fabrication of hydrogen sensors with transparent titanium oxide nanotube-array thin films as sensing elements

Transparent thin films comprised of highly ordered titania nanotube-arrays were grown from titanium thin films using an anodization technique, from which highly sensitive and selective hydrogen sensors that can operate at room temperature were fabricated. Titanium films sputter deposited on glass at 500 °C were anodized in a fluorine-containing electrolyte to obtain nanotube-array films. Precise monitoring of current during the anodization enabled removal of the samples from the anodization bath at a point where the remaining metal layer became discontinuous, without destroying the nanotube architecture. The samples were then annealed in oxygen at 420 °C to crystallize the nanotube-arrays as well as oxidize any un-anodized metallic regions, yielding transparent films comprised of titanium oxide nanotube-arrays. Herein, we discuss the morphology, structure and optical characterization of these films. When coated with a 10-nm discontinuous palladium layer, the optically transparent nanotube-array films serve as excellent hydrogen sensors, exhibiting a four-order magnitude drop in resistance with exposure to 1000 ppm hydrogen at room temperature.     

Porous titanium implant materials and their potential in orthopedic surgery

In orthopedic surgery bony defects remains a challenge. In generally autologous or heterologous bony transplants can be used. Main problem is the limited amount of bone and donor site morbidity. Nowadays excellent implants and scaffolds at low costs are necessary in respect to the financial problems in our health care system and the strong financial limitations in clinical medicine. Recently a biomimetic approach, in which a porous synthetic bone substitute with properties similar to these of trabecular bone has been developed (VITOFOAM?). Aim of our study was to investigate whether cp‐Ti or Ti6Al4V or stainless steel (316L) porous metal implants achieve material properties comparable to bone. Materials and Methods Three cp‐Ti, Ti6Al4V and stainless steel (316L) porous metal specimen each with a pore size of 150 to 600 μm have been tested in respect to determine the Young’s Modulus E (GPa), Compression Strength (MPa) and Porosity (%) under axial compression. Results Young’s Modulus of the cp‐ Ti samples was in the range of 1.2 to 2.8 GPa, for Ti6Al4V 2.3 to 4.1 GPa could be achieved. Compression Strength for cp‐ Ti and Ti6Al4V ranged from 30 to 65 MPa with porosity values ranged from 71 to 80 %. Discussion The highly porous nature of VITOFOAM? combined with the good biocompatibility of cp‐ Ti or Ti6Al4V and the mechanical properties make these materials ideal bone scaffolds. Trabecular bone shows pore sizes of 300–1500 μm, Young’s Modulus of 0.2–2 GPa and Compression Strength from 5–50 MPa. Porosity of spongious bone ranges from 30 to 95 %. These values are comparable to the values achieved with VITOFOAM?. Porous titanium foam with its osteoconductive properties may therefore be an ideal and cheap alternative. Implant costs can be lowered to 50 % for implants e.g. for intercorporal interbody fusion in spinal surgery. Actually further research is done to show the possibility in spinal surgery or loading technologies with Tricalciumphosphat, Hydroxylapatit, Antibiotics or Cytostatics.     

Measurement of the distribution of the temperature field of materials in microwave resonators of complex shape

The main problems that arise when measuring the temperature field of dielectric materials in microwave resonators of different shapes at a frequency of 2450 MHz are considered. The results of measurements of the temperature field distribution are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 56–58, June, 2008.     

Effect of aggregate size distribution and confining pressure on mechanical property and microstructure of cemented gangue backfill materials

The use of gangue, cementitious materials, and water mixed to make cemented gangue backfill material (CGBM) can achieve solid waste recycling while reducing environmental problems caused by its accumulation. In this paper, the fractal dimension of particle size distribution (PSD) and the confining pressure were investigated on the compressive strength, elastic modulus, stress–strain behavior, dilatancy deformation, and failure mode of CGBM using uniaxial compression, conventional triaxial compression, and microscopic scanning tests. The mechanism of the PSD fractal dimension on the mechanical properties of CGBM was revealed from a microscopic perspective. The results demonstrate that the compressive strength and elastic modulus of CGBM are quadratic polynomial and positively linearly related to the PSD fractal dimension and confining pressure respectively, with the PSD fractal dimension characterizing the maximum compressive strength of CGBM ranging between 2.4150 and 2.6084. The volume strain variation of CGBM diminishes as the PSD fractal dimension grows and increases dramatically when the confining pressure rises. The PSD fractal dimension has a quadratic polynomial relationship with both the cohesive force and the internal friction angle of CGBM. A reasonable PSD fractal dimension can optimize the microstructure of CGBM, reduce the distribution of defects such as microcracks and micropores, and enable hydration products to effectively fill the defects, guaranteeing that the CGBM has sufficient load-bearing capacity.     

Techniques for measuring low levels of hydrogen or hydrogen-bearing materials in solids

Three new nondestructive techniques for detecting ppm levels of hydrogen in metals and solids are discussed, along with a review of existing techniques. Two of the new techniques use neutron beams to detect hydrogen. One of these is applicable to steel samples on the order of 1–5 cm in dimension, and has a lower level of detection of 2 weight ppm. The second nuclear technique is applicable to any metal or solid with a mass number greater than about 12, is most suitable for samples on the order of a few millimeters thick, and has a lower level of sensitivity of 0.4 weight ppm. The third technique uses a modulated beam mass spectrometry system, can handle samples up to 100 grams of any size (as long as the sample can be heated uniformly) and has a sensitivity of less than 0.02 weight ppm. Suggestions for possible applications of these techniques are discussed.     

弹性反冲探测技术分析薄膜中的氢和氦含量

给出了用离子束来弹性反冲探测能谱,分析薄膜材料中的轻质元素含量及其深度分布的基本原理和试验方法,并对其发展和应用做了介绍。作为应用举例,用8 MeV的O3+作为入射离子进行弹性反冲金属钛膜中的氢和氦,通过解析能谱获得了氢和氦含量的深度分布曲线。该技术在涉及氢和氦在材料中的行为研究方面将有重要应用。     

Improvement in oxidation resistance of the intermetallic compound titanium aluminide by heat treatment under a low partial pressure oxygen atmosphere

The improvement in oxidation resistance of an intermetallic compound TiAl was investigated by means of a new type of surface treatment: heat treatment under a low partial pressure oxygen atmosphere. The specimens treated by this method showed superior oxidation resistance compared with a nickel-base superalloy Inconel 713C during cyclic heating to a temperature of 1173 K in static air. The best conditions for the heat treatment under a low partial pressure oxygen atmosphere were found to be: pressure, 6.7 X 10-³ Pa; temperature, 1273 K; time, 7.2 ks (2 h) or more. It was presumed that the excellent oxidation resistance resulting from this method is due to preferential formation of a thin, strong Al₂0₃ surface layer.     

Analysis of anisotropy mechanism in the mechanical property of titanium alloy tube formed through hot flow forming

Anisotropy of mechanical property is an important feature influencing the service performance of tita-nium(Ti)alloy tube component.In this work,it is found that the hot flow formed Ti alloy tube exhibits higher yield strength along circumferential direction(CD),and larger elongation along rolling direction(RD),presenting significant anisotropy.Subsequently,the quantitative characteristics and underlying mechanism of the property anisotropy were revealed by analyzing the slip,damage and fracture behav-ior under the combined effects of the spun{0002}basal texture and fibrous microstructure for different loading directions.The results showed that the prismatic slip in primary α grain is the dominant defor-mation mechanism for both loading directions at the yielding stage.The prismatic slip is harder under CD loading,which makes CD loading present higher yield strength than RD loading.Additionally,the yield anisotropy can be quantified through the inverse ratio of the averaged Schmid Factor of the activated prismatic slip under different loading directions.As for the plasticity anisotropy,the harder and slower slip development under CD loading causes that the CD loading presents larger external force and normal stress on slip plane,thus leading to more significant cleavage fracture than RD loading.Moreover,the micro-crack path under RD loading is more tortuous than CD loading because the fibrous microstructure is elongated along RD,which may suppress the macro fracture under RD loading.These results suggest that weakening the texture and fibrous morphology of microstructure is critical to reduce the differences in slip,damage and fracture behavior along different directions,alleviate the property anisotropy and optimize the service performance of Ti alloy tube formed by hot flow forming.     

Second generation (low modulus) titanium alloys in total hip arthroplasty

Titanium alloys ‐ type (α+β) ‐ like Ti6Al7Nb or Ti6Al4V are widely used in cementless total hip arthroplasty due to their lower modulus, biocompatibility and enhanced corrosion resistance in comparison to Stainless Steel or Cobalt‐Chromium implant materials. Several articles report about atrophy of the proximal femur in cases where long stems with a big diameter made of (α+β) Titanium alloys with a relatively high value of the Youngs’ Modulus (110 GPa) in comparison to the Youngs’ Modulus of cortical bone (15–25 GPa) have been implanted using a prosthesis design with distal anchorage technique. Meanwhile several implant manufacturers have developed a new group of biocompatible Beta‐Titanium alloys with a lower Youngs’ Modulus around 70 GPa. This article gives an overview of the current status of available low modulus Titanium alloys including their mechanical characteristics and future developments.     

纸质缓冲材料能量吸收特性研究进展

综述了两类常用纸质缓冲材料能量吸收特性的研究进展,从缓冲吸能影响因素及规律两方面总结国内外研究侧重点和取得的成果,并着重就环境湿度和应变率对纸质缓冲材料吸能特性影响的研究现状进行了阐述。提出考虑环境湿度和应变率,建立蜂窝纸板和瓦楞纸板能量吸收理论预报模型,构建兼具普适性、准确性和简便性的纸质缓冲材料吸能特性表征方法,并应用于缓冲包装优化设计中,是今后研究的重点。     

季鏻盐-铜/蒙脱土复合材料的制备及性能

依次将铜离子和十四烷基三丁基季鏻阳离子(TBTP)与蒙脱土离子交换得到季鏻盐-铜/蒙脱土复合材料(TBTP-Cu/MMT),其中铜和季鏻阳离子的质量含量分别为2.87%和24.07%.热重(TG)、X射线衍射(XRD)分析结果表明,铜离子和季鏻阳离子确实交换到蒙脱土中,并且TBTP-Cu/MMT中季鏻阳离子的热分解起始温度约为220℃,具有较好的热稳定性.抗菌试验结果表明,TBTP-Cu/MMT具有较好的抗菌性能,对金黄色葡萄球菌和大肠杆菌最小抑菌浓度(MIC)分别为12.5 μg·mL-1和200μg·mL-1.研究了蒙脱土复合材料浓度及与细菌的接触时间对抗菌性能的影响,发现随着浓度的增加、接触时间的延长,活菌数减少,抗菌性能提高;将100 mg TBTP-Cu/MMT在100 mL蒸馏水中浸泡20天后,季鏻阳离子和Cu2 的释放量很小,分别为4.891 mg·L-1和1.928 mg·L-1,表明TBTP-Cu/MMT具有良好的耐水性.     

Metastable phase-assisted nucleation in a near-alpha titanium matrix composite with network architecture

ABSTRACT

The secondary alpha (α_s) phase is an important component of a novel TiBw/TA15 composite with network architecture. In order to investigate the precipitation mechanism of the α_s phase, the microstructure after multi-directional forging was characterised by EPMA, EBSD, and TEM. The results showed that several differently sized α_s phases separated out from the (Mo and V)-enriched phase, which was composed of a nano-sized metastable omega phase along with some retained beta phase. It could be also found that the metastable omega phase would transform to the alpha phase when adequate activation energy was provided. The precipitation mechanism of the α_s phase in this composite has been discussed in detail and it can be inferred as an omega-assisted heterogeneous nucleation process.

This paper is part of a thematic issue on Titanium.