铌欠缺对PZN基陶瓷微观结构和介电性能的影响

使用化学混合法制备了PZN基陶瓷 ,研究了铌离子欠缺对其相组成、微观结构和介电性能的影响。随着铌离子欠缺量的增加 ,预烧粉体中的焦绿石相含量大幅度增加 ;但是微量铌离子欠缺对烧结后陶瓷的相组成没有什么影响 ,甚至当铌欠缺量达到 2 %时 ,陶瓷仍然为 10 0 %的钙钛矿结构。随着铌欠缺的增加 ,晶粒尺寸增大 ,但是陶瓷仍具有良好的成瓷性。铌欠缺使介电常数减小 ,但是对介电损耗影响很小 ;介电常数减小的原因归结为“有效有序微区”尺寸的减小和铁电活性的铌离子浓度的降低     

Effects of Normal Load,Sliding Speed,and Surface Roughness on Tribological Properties of Niobium under Dry and Wet Conditions

The effects of normal load, sliding speed, and surface roughness on the friction and wear of high-purity niobium (Nb) during sliding without and with an introduction of water were systematically investigated. Increasing the normal load or sliding speed decreased the friction of the Nb under the both dry and wet conditions because the increased wear of the Nb decreased the interfacial shear strength between the steel ball and Nb by promoting the surface roughening and the production of wear debris. However, the Nb tested at the lowest sliding speed under the lowest normal load with water exhibited the lowest friction and wear due to the formation of oxide layer on the wear track. The friction and wear of the Nb tested under the dry condition decreased with increased surface roughness because the higher interfacial shear strength between the steel ball and smoother Nb resulted in the earlier breakdown of the native oxide layer and direct contact between the steel ball and Nb. However, increasing the surface roughness of the Nb increased its friction and wear under wet conditions, probably due to the easier breakdown of the oxide layer that formed on the rougher surface during sliding. The tribological results clearly showed that the introduction of water during sliding had a significant influence on the tribological properties of the Nb.     

铌欠缺对掺镧PZN基陶瓷的有序微区和介电性能的影响

研究了铌欠缺对掺镧 PZN基陶瓷相结构、有序微区以及介电性能的影响。铌欠缺消除了掺镧所产生的焦绿石相 ,使陶瓷试样恢复为百分之百的钙钛矿相结构。 Ram an散射光谱分析表明 ,铌欠缺使掺镧 PZN基陶瓷的有序微区增大 ,同时铌欠缺也提高了掺镧 PZN基陶瓷的介电常数。铌欠缺使介电常数增大的原因归结于焦绿石相的消除和“有效有序微区”尺寸的扩大     

Thermal oxidation of Zr-2.5Nb alloy and its biotribological properties

Zirconium alloys are potential materials for permanent implants due to their suitable mechanical strength, good biocompatibility, and superior corrosion resistance. However, Zr-2.5Nb alloys are greatly limited to the applications of artificial joints due to their poor tribological properties. Thermal oxidation is considered as a good way to improve the tribological properties of Zr-2.5Nb alloys. The effect of temperature on the properties of thermal oxidized Zr-2.5Nb alloys was investigated to understand the growth mechanism of ZrO₂ coating. In addition, the surface hardness of the thermal oxidized Zr-2.5Nb alloys was examined. Finally, the tribological properties of the thermal oxidized Zr-2.5Nb alloys were investigated to evaluate the potential application in artificial hip joints. The results showed that ZrO₂ coating was successfully synthesized on the surface of Zr-2.5Nb alloys, and the temperature has significantly effects on the thickness of the ZrO₂ coatings. It also found that thermal oxidation could significantly improve the surface hardness and wear resistance of Zr-2.5Nb alloys.     

ICP-AES法测定Nb:SrTiO_3晶体及功能陶瓷材料中的铌含量

本文报导了用ICP-AES法直接测定掺铌钛酸锶晶体及功能陶瓷材料(Nb:SrTiO_3)中铌含量的分析方法。研究了试样的分解方法、铌分析线的选择、Nn:SrTiO_3基体的干扰及试液的稳定性。所选三条铌分析线的检出限分别为0.0042μg/mL、0.0015μg/mL、0.0013μg/mL。合成试样回收率为98.7％～100.9％。铌含量为0.1％1.0％时,测量的相对标准偏差<1.5％。方法简便、准确,用于样品分析,结果满意。     

电感耦合等离子体光谱法测定钢中W、Nb、Al

在试样消解过程中,通过增加氢氟酸的浓度和适当延长消解时间来完成对Al的溶解和对Nb、W的络合,对于试样的消解条件进行优化后,再采用电感耦合等离子体发射光谱分析技术测量钢中的W、Nb、Al,讨论W、Nb、Al的光谱干扰因素和分析参数。实践证明,本方法具有良好的精密度和准确性,适用于对多牌号、多批次钢种生产的日常检测。     

钛铌钒铬在高碳焊缝中的分布

利用电子探针(EPMA)、能谱分析(EDS)对高碳多元合金焊缝和急冷熔滴中的碳化物及合金元素分布进行了研究，探讨了Ti、Nb、V及Cr共存时碳化物的形成规律及机理。结果表明，Ti、Nb强烈与C结合形成碳化物，并能由液相中析出；同时，Ti、Nb的存在对V和Cr的碳化物倾向有抑制作用，使V和Cr固溶于基体中，避免了网状碳化物。     

Nb对SiC颗粒／NiCrMo合金铸铁界面润湿性的影响

研究了Ｎｂ对ＳｉＣ颗粒／ＮｉＣｒＭｏ界面润湿性的影响。结果表明，适量的Ｎｂ可以显著地改善上述两者的界面润湿性，Ｎｂ的最佳含量为０．０６ω％。     

A study on the mechanical properties of ti-8ta-3nb alloy for biomaterials

Ti-8Ta-3Nb has been developed as a new biomaterial. The experimental specimens are as-cast and forged Ti-8Ta-3Nb alloys. Treatment in a solution, ranging from 760 to 960°C has carried out. The microstructural research has carried out after the solution treatment and the hardness was measured. The specific heat and the length variations of Ti-8Ta-3Nb were also measured. The optimum temperature for the solution heat treatment of Ti-8Ta-3Nb was found to be 880°C. This was based on the mechanical properties and the volume fraction of α phase and their phases shown from the results of the solution heat treatment. From the results, the β transition temperature of Ti-8Ta-3Nb was found to be between 860° and 880°C.     

Fretting wear of Ti-48Al-2Cr-2Nb

An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296–823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473–823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals.     

粉末冶金Ti-22Al-25Nb合金的真空热压烧结工艺

以气雾化法获得的Ti-22Al-25Nb（at.%）预合金粉末为初始原料,采用真空热压烧结工艺方法制备组织致密、成分均匀的粉末冶金Ti-22Al-25Nb合金。应用有限元软件MSC.Marc对Ti-22Al-25Nb（at.%）预合金粉末的致密化过程进行数值模拟,分析了温度和压力对Ti-22Al-25Nb粉末致密化过程的影响,揭示了粉末相对密度随温度和压力变化的规律,得到优化的烧结工艺参数,以指导热压实验烧结。通过热压烧结实验制备了组织致密、成分均匀的Ti-22Al-25Nb合金,发现1 050 ℃/35 MPa/1 h条件下烧结的合金具有最优的室温和650 ℃高温综合力学性能。     

Nb含量对制氢转化炉管HP合金组织转变规律影响的研究

离心铸造的HP40和HP40-Nb合金被广泛用作制氢转化炉炉管材料,通常管壁温度可高达1000℃。通过观察HP40和HP40-Nb合金在原始铸态和高温状态下的显微组织,研究了不同Nb含量对合金共晶组织稳定性的影响。采用扫描电镜和X射线衍射仪研究了炉管材料的显微组织和相结构。研究结果表明:在碳含量0.4%左右的HP合金中,Nb含量0.210%~0.357%时主要起到固溶强化作用,共晶碳化物主要是M7C3,仅有少量的富Nb共晶MC散布在晶界上;当Nb含量0.89%~1.55%时,HP40-Nb原始铸态组织中析出了富Cr的M7C3碳化物和富Nb共晶MC。对于高温状态下的HP40-Nb合金,在晶界和枝晶间形成的富Nb共晶的MC提高了原始共晶组织的稳定性,使得炉管材料的使用温度可向高温推移。     

Processing map for the hot working of Ti-8Ta-3Nb

This paper considers the deformation behavior during hot forging in as-cast and forged specimens of Ti-8Ta-3Nb. The experimental specimens are as-cast and forged specimens of Ti-8Ta-3Nb. The deformation behavior of Ti-8Ta-3Nb alloy has been characterized on the basis of its flow stress variation obtained by true strain rate compression testing in the temperature range 650-900°C and strain rate range 0.001–10s⁻¹ P. The present study aims at assessing the hot workability of as-cast and forged Ti-8Ta-3Nb using the approach of processing maps and comparing specimens of Ti-8Ta-3Nb. The maps are an explicit representation of the various processes that occur in the different temperature and strain rate conditions. The construction of the maps is based on the experimentally determined changes of strain rate sensitivity coefficient. Processing maps were obtained at strains of 0.2, 0.3, 0.4 and 0.5 in both as-cast and forged specimens.     

Nb对Ti3Al价电子结构及其脆性的影响

应用固体与分子经验电子理论计算了Ti3Al及加入Nb后各相的价电子结构,并从均匀变形因子α、解理能Gc及位错行为等方面分析了Nb对Ti3Al脆性的影响。结果表明,Nb使α2相部分无序化,产生新的韧性相,提高了Ti3Al合金的α和Gc值;同时Nb也减弱了Ti-Ti共价键,增加了基面滑移,从而综合导致Ti3Al脆性有本质改善。     

铜和铌对多层焊焊缝金属显微组织和硬度的影响

采用实际堆焊、Gleeble焊接热模拟、透射电镜及光学显微镜和硬度仪等分析了添加不同含量的铜和铌时,对多层焊焊缝金属显微组织和硬度的影响,探讨了铜和铌的作用机制.结果表明:在普通碳-锰焊缝金属的基础上添加质量分数约3.0%的铜和0.03%的铌时,在模拟多层焊各再热区域均可形成均匀的贝氏体组织,且产生大量均匀、热稳定性良好的沉淀析出相,使多层焊高强度焊缝具有均匀的硬度.     

控轧控冷工艺条件下X70针状铁素体管线钢铌、钛的析出行为

通过透射电镜研究了X70针状铁素体管线钢中微合金元素铌、钛在控轧和控冷过程中的析出行为。结果表明：析出粒子主要以两种形式存在,一种是在高温下尺寸较大的铌、钛复合粒子的析出,方形的TiN粒子先析出,随后含铌的粒子将包覆在TiN外面并以其为核析出,而不是独立形核;另一种是在低温条件下,由于变形使大量细小的近似球形的NbC在晶内的位错和亚晶上析出。同时还讨论了控轧控冷技术对第二相粒子析出的促进作用。     

The Tribological Behavior of a Ti-46Al-2Cr-2Nb Alloy Under Liquid Paraffine Lubrication

The tribological behavior of a Ti-46Al-2Cr-2Nb alloy prepared by hot-pressed sintering was investigated under liquid paraffine lubrication against AISI 52100 steel ball in ambient environment and at varying loads and sliding speeds. For comparison, the tribological behavior of a common Ti-6Al-4V alloy was also examined under the same testing conditions. The worn surfaces of the two alloys were analyzed using a scanning electron microscope. The friction coefficient of the Ti-46Al-2Cr-2Nb alloy in the range of 0.13–0.18 was significantly lower than that of the Ti-6Al-4V alloy (0.4–0.5), but comparable to that under dry sliding, which indicated that TiAl intermetallics could be more effectively lubricated by liquid paraffine than titanium alloys. Applied load and sliding speed have little effect on the friction coefficient of the Ti-46Al-2Cr-2Nb alloy. The wear rate of the Ti-46Al-2Cr-2Nb alloy was about 45–120 times lower than that of Ti-6Al-4V alloy owing to Ti-6Al-4V alloy could not be lubricated effectively. The wear rate of the Ti-46Al-2Cr-2Nb alloy increased with increasing applied load, but decreased slightly at first and then increased with increasing sliding speed. The wear mechanism of the Ti-46Al-2Cr-2Nb intermetallics under liquid paraffine lubrication was dominated by main plowing and slight flaking-off, but that of the Ti-6Al-4V alloy was plastic deformation and severe delamination.     

Design and performance of a new induction furnace for heat treatment of superconducting radiofrequency niobium cavities

Superconducting radio frequency (SRF) cavities made of high purity niobium (Nb) are the building blocks of many modern particle accelerators. The fabrication process includes several cycles of chemical and heat treatment at low (～120 °C) and high (～800 °C) temperatures. In this contribution, we describe the design and performance of an ultra-high-vacuum furnace which uses an induction heating system to heat treat SRF cavities. Cavities are heated by radiation from the Nb susceptor. By using an all-niobium hot zone, contamination of the Nb cavity by foreign elements during heat treatment is minimized and allows avoiding subsequent chemical etching. The furnace was operated up to 1400 °C with a maximum pressure of ～1 × 10(-5) Torr and the maximum achievable temperature is estimated to be higher than 2000 °C. Initial results on the performance of a single cell 1.5 GHz cavity made of ingot Nb heat treated at 1200 °C using this new induction furnace and without subsequent chemical etching showed a reduction of the RF losses by a factor of ～2 compared to cavities made of fine-grain Nb which underwent standard chemical and heat treatments.     

Effect of as-ground surface and the BALINIT® C and Nb–S coatings on contact fatigue damage in gears

The influence of as-ground surface and the BALINIT^® C and Nb–S coatings on contact fatigue damage have been investigated using testing of case-carburised S156 steel helical gears. The micro-surface features on the as-ground gear flank tend to initiate micro-pitting. In BALINIT^® C coated gears, the surface irregularities are removed by polishing effect resulting in small scale initiation of micro-pitting at the interface between polished and unpolished regions. In Nb–S coated gears, the coating tends to penetrate and fill-up the surface micro-valleys and hence showed only scattered micro-pitting. The Nb–S coated gears did not produce any tooth profile loss whilst the BALINIT^® C coated gears produced profile loss. However, both BALINIT^® C and Nb–S coated gears show enhanced contact fatigue performance.     

萃取色层分离ICP／MS测定U3O8中Zr,Nb,Ta和Ru

〕本文叙述了ＣＬ－ＴＢＰ萃取色层分离,ＩＣＰ／ＭＳ测定Ｕ３Ｏ８ 中痕量杂质元素Ｚｒ、Ｎｂ、Ｔａ 和Ｒｕ 的方法。Ｕ３Ｏ８ 经硝酸及少许氢氟酸溶解后,用ＣＬ－ＴＢＰ萃淋树脂作固定相,硝酸与草酸的混合酸作流动相,进行萃取色层分离使被测杂质元素与铀基体分离,杂质元素淋洗液用ＩＣＰ／ＭＳ测定。取样量为０．５ｇ 时,杂质元素Ｚｒ、Ｎｂ、Ｔａ和Ｒｕ 的测定下限为１×１０－ ８ｇ／ｇ,方法的重加回收率在９３％ －１１２％ 之间,８ 次平行取样测量结果的相对标准偏差小于１７％ ,本方法应用于Ｕ３Ｏ８ 标准物质中Ｚｒ、Ｎｂ、Ｔａ和Ｒｕ 的测量,测量结果与定值数据吻合较好