钢熔炼炉对N2/SF6气氛中镁合金表面膜的影响

在密封的钢熔炼炉中研究了不同温度下0.3%SF6/N2气氛中AZ91D镁合金的表面膜成分和形貌,以及表面膜成分与保护效果之间的关系.结果表明当熔炼温度超过780℃,表面膜中开始检测到铁,随着熔炼温度的增加,表面膜中铁含量逐渐增加.780,810,820 ℃时,膜中铁含量分别为1.65at%,35.14at%和46at%当熔炼温度为810℃,表面膜中开始出现孔洞;当熔炼温度超过824℃,表面膜宏观很不平整,AZ91D镁合金显著蒸发.可能原因是780℃以上的熔炼温度下,FeF3具有很高的蒸气压,FeF3在钢熔炼炉壁上生成、升华,再到温度更低的小坩埚中心区和Mg蒸汽反应,生成MgF2和Fe.     

含S、F的空气气氛对镁合金熔体的保护

对镁合金熔体在密封的FeS2-HFC134a-空气气氛中熔炼的保护效果进行了研究。结果表明,该气氛对Mg熔体有很好的保护效果,并且该气氛比仅含S或者F的气氛的保护效果优越。在熔炼温度为730℃、保温时间为1～30min时,0.15%的HFC-134a+1g的FeS2+空气气氛可以阻止Mg熔体的氧化与蒸发。然而,当保温时间增加至60min时,该气氛不具保护效果。通过SEM,EDS和XRD等检测技术对试验条件下形成的镁合金表面膜进行了检测分析。结果表明,S、F混合气氛下形成的表面膜含有Mg、F、O和S等4种元素,其主要相为MgF2、MgO和MgS。随着保温时间增加,S、F混合气氛下形成的表面膜逐渐变厚,更趋于均匀和致密,这是由于氧化镁基氧化膜中致密度高的MgF2和MgS增加的缘故。     

在SF_6和N_2混合气氛的密封炉中熔炼AZ91D镁合金

在SF6和N2混合气氛的密封炉中,研究了SF6含量和保温时间对AZ91D镁合金熔炼保护效果的影响,并对表面膜的形貌、厚度、成分和结构进行了分析。研究结果表明,密封炉中形成的表面膜致密,厚度在0.6~1.4μm之间,成分为F和Mg,摩尔比约为2∶1,相结构为MgF2,对镁合金熔炼起保护作用。混合气氛中SF6的含量对保护效果有显著的影响,SF6的含量为0.01%时不起保护作用,SF6的量为0.03%以上时起到保护作用。SF6含量为0.1%的混合气氛中,保温时间为7.5~120.0min时都有保护效果;保温时间为7.5min时形成的表面膜较薄,保温时间在15~120min时表面膜厚度变化不明显。     

FeS2对AZ91D镁合金熔炼保护机理研究

在空气气氛的镁合金密封熔炼炉中加入固态硫铁矿(FeS2),研究了FeS2对AZ91D镁合金熔炼的保护效果,并采用SEM、EDS和XRD等检测分析技术对保护膜形貌、成分和相组成进行了研究.研究结果表明,在空气气氛中,硫铁矿对镁合金熔炼有良好的保护效果.在730℃中保温30 min时保护膜由MgS、MgO和MgF2混合物组成,保护膜致密;保护膜的厚度随保温时间的延长而增加,其厚度在1.0～2.0 μm之间.FeS2在空气中分解和氧化生成S和SO2,产物与空气中的O2以及镁液反应生成MgS和MgO,使镁熔体表面氧化膜变致密,从而起到熔炼保护作用.通过热力学分析可知,受热时硫铁矿消耗密封熔炼炉内的氧,并且在表面膜中MgS形成趋势大,形成的MgS的稳定性比MgO好.     

FeS2/Air气氛中熔炼AZ91D镁合金试验

在密封容积为13L的镁合金熔炼炉中加入固态硫铁矿(FeS2),研究了FeS2/Air气氛中,FeS2加入量、熔炼温度和保温时间等对AZ91D镁合金熔炼保护效果的影响,并采用SEM、EDS和XRD等对保护膜形貌、成分和相组成等进行了研究。结果表明,试验温度小于760℃时,加入硫铁矿的空气气氛对镁合金熔炼有良好的保护效果。当熔炼温度为730℃时,保温30min,硫铁矿加入量为1g时,保护效果较差;加入量为2g和5g时,保护效果好,加入量为10g时,保护效果变差。在730℃时,当保温时间提高到60min时,2g的硫铁矿保护效果差,将硫铁矿量增至5g时,保护效果良好。熔炼温度提高到800℃,保温30min,2g硫铁矿保护效果差。加入硫铁矿的空气气氛中形成的保护膜由MgS和MgO混合物组成,保护膜致密,保护膜的厚度随保温时间的延长而增加,其厚度在1.0～2.0μm之间。     

FeS2/Ar/空气气氛中镁合金熔炼试验研究

在开放式熔炼炉中熔化了AZ91D镁合金,研究了不同粒度的FeS2和空气气氛中不同含量的Ar对AZ91D镁合金熔炼保护效果.采用SEM、EDS和XRD对保护膜形貌、成分和相组成进行了分析.结果表明,温度为730℃时,加入一定量硫铁矿的保护效果是好的.熔炼温度为730℃,保温30min时,硫铁矿粒度越小,保护效果越好,但当粒度减小到一定程度时,保护效果反而减弱;随着空气含量的降低,保护效果加强,但当空气含量太少时,保护效果开始减弱.     

在密封熔炼炉含0.01%HFC134a的氮气中熔炼AZ91D镁合金

在一次性充入含0.01%HFC134a(体积分数)的氮气的密封熔炼炉中,研究了表面搅拌、熔炼温度和熔炼炉密封质量对AZ91D镁合金保护效果的影响以及气氛对熔炼坩埚内壁的腐蚀,并对表面膜形貌、厚度和成分进行了研究。研究结果表明,HFC134a适合充当镁合金在密封熔炼炉中保护气体,氮气是一种好的载气。无表面搅拌时,AZ91D镁合金的最高保护温度是865℃;有表面搅拌时,最高保护温度是800℃。允许熔炼炉内压升率超过10 kPa/min。所有保护膜呈致密胞团状结构,膜厚度在1~2μm之间,且比较均匀。而AZ91D镁合金不被保护时,表面膜呈絮状,膜厚度在2~5μm之间变化,厚度很不均匀。随熔炼温度升高,表面膜中C含量逐渐减少到零,表面膜中氧含量逐渐升高。炉内气氛对熔炼炉内壁无可观察到的腐蚀。     

含SO2气氛对熔态镁合金的保护行为（英文）

在密封和开放条件下研究含SO2的不同气氛对AZ91D合金的保护行为,分析表面膜的形貌与成分。结果表明:在密封条件下,含SO2气体对熔体的保护需要一定量的O2;含SO2和O2的气氛通过与熔体反应,在熔体表面形成一层致密的网状结构表面膜,表面膜主要含有MgO和MgS;MgS提高了表面膜的致密度,从而提高了表面膜的保护作用。     

HFC-125/N_2混合气体对熔态AZ91D镁合金的保护行为研究

采用SEM、EDS、XRD和XPS等分析手段研究了HFC-125/N2混合气体对AZ91D镁合金熔体的保护效果,以及所形成的表面膜的形成过程。结果表明:HFC-125可以对镁熔体提供长期有效的阻燃保护;所得镁熔体表面膜主要由MgF2构成;随着时间的延长,表面膜内Mg含量逐渐减少,F含量逐渐增多。     

空气对流对HFC125/N2气氛下镁熔体表面膜的影响

HFC125气体可以对高温镁合金提供有效的阻燃保护。研究了空气对流对HFC125/N2混合气体与镁合金熔体反应形成的表面膜的影响。结果表明：在弱空气对流条件下所得表面膜几乎没有氧原子,而在强空气对流条件下所得表面膜含有少量氧原子;两种工作环境下保护效果没有明显差别。     

Structural, mechanical and corrosion properties of TiOxNy/ZrOxNy multilayer coatings

Results on the deposition and characterization of TiO_xN_y/ZrO_xN_y multilayers, with bilayer periods of 20 and 400 nm, are presented. The coatings were deposited on TiNiNb alloy substrates by the pulsed magnetron sputtering method. The elemental composition, hardness, adhesion and corrosion resistance of the coatings were analyzed.As resulted from the XPS analysis, the individual layers consisted of a mixture of titanium or zirconium oxynitrides and corresponding oxides. X-ray analysis revealed that the coatings were amorphous. Only slight differences between the microhardness and adhesion values of the coatings with small and large bilayer period Λ were found. The experiments also showed that the multilayered coatings improved the corrosion resistance of the uncoated alloy and reduced the amount of ion release in artificial body fluids.     

生物医用NiTi形状记忆合金腐蚀研究进展

镍钛形状记忆合金(NiTi-SMA)具有较好的耐腐蚀和机械性能,在口腔和临床医学中有着大量而广泛的应用。NiTi-SMA腐蚀后释放Ni²⁺会引发细胞毒性和过敏反应,进一步提高NiTi-SMA的耐蚀性是目前生物医学材料领域发展的核心之一。本文对近年来国内外有关口腔医学和临床医学中常用NiTi-SMA的腐蚀研究现状进行了总结,同时也对NiTi-SMA增材制造及表面改性技术进行了评述,以期为开发高性能抗腐蚀生物医用NiTi-SMA提供一定的指导意义。     

Li掺杂Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3高熵陶瓷的制备及介电性能研究

近年来,在高熵合金基础上发展起来的高熵陶瓷逐渐引起了研究者的广泛关注,其出现为开发高性能的无机非金属材料提供了新的设计思路。本文采用固相法制备了BaMO3基钙钛矿型高熵陶瓷Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3 (x = 0, 2.3%, 5.3%, 8.3%, 11.3%),并研究了Li含量对高熵陶瓷物相结构、微观形貌及介电性能的影响。结果表明,Li含量对陶瓷结构的影响不大,陶瓷均保持立方钙钛矿结构,且无杂相产生;陶瓷的晶粒尺寸相对较均匀。当x = 0时,即B位七元等摩尔比Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li1/7)O3高熵陶瓷,其介电常数达到了最大值2920 (@100 Hz),相较于已报道的不掺Li的六元高熵钙钛矿陶瓷Ba(Ti1/6Sn1/6Zr1/6Hf1/6Nb1/6Ga1/6)O3提升了近50倍。     

MOCVD growth and characterizations of BxAl1−xAs and BxAl1−x−yInyAs alloys

Zinc-blende B_xAl_1−xAs and B_xAl_1−x−yIn_yAs alloys have been grown on exactly oriented (0 0 1)GaAs substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). The influence of susceptor coating, growth temperature and gas-phase boron mole fraction on boron incorporation into AlAs has been comprehensively investigated. It has been found that boron incorporation into AlAs could be enhanced and the optimal growth temperature range of B_xAl_1−xAs alloys changed from 580 °C to 610 °C when SiC-coated graphite susceptors were replaced by the non-coated ones. In this study, the maximum boron composition x of 2.8% was achieved for the pseudomorphically strained B_xAl_1−xAs alloys. AFM measurements show that RMS roughness of B_xAl_1−xAs alloys increased sharply with the increase of gas-phase boron mole fraction. Raman spectra of B_xAl_1−xAs alloys show a linear increase of the BAs shift with boron composition x. Based on BAlAs deposition, bulk B_xAl_1−x−yIn_yAs (x = 1.9%) quaternary alloy was grown lattice-matched to GaAs successfully. Moreover, 10-period BAlAs/GaAs and BAlInAs/GaAs MQW heterostructures were also demonstrated.     

Ag/LaNixCo1-xO3触点材料的制备及电接触性能研究

本文运用溶胶-凝胶燃烧法合成了双钙钛矿型LaNixCo1-xO3(LNCO)纳米材料,利用粉末冶金和热挤压技术制备了相应的Ag/LNCO触点材料及元件样品。重点考察了不同Ni、Co含量对Ag/LNCO触点材料微观结构、物相组成、物理性能、力学性能及电寿命服役能力的影响,对其电弧侵蚀失效行为进行了研究,并与SnO2粉体增强Ag基触点材料进行对比。结果表明:溶胶凝胶法合成的LNCO纳米颗粒粒径为20-30 nm,经粉末冶金工艺制备的Ag/LaNi0.5Co0.5O3触点材料电学性能和电寿命都优于Ag/SnO2触点材料,其电阻率低至2.10 μΩ?cm,电寿命性能达到51287次。表明Ag/LaNi0.5Co0.5O3触点材料性能较佳,是一种可以取代Ag/CdO的新型触点材料。     

Hydrothermal synthesis of superconductors Ba1−xKxBiO3 and double perovskites Ba1−xKxBi1−yNayO3

Superconductors Ba_1−xK_xBiO₃ and body-centered double perovskites Ba_1−xK_xBi_1−yNa_yO₃ have been selectively synthesized by a facile hydrothermal route. The appropriate ratio and adding sequence of initial reagents, alkalinity, reaction temperature and time are the critical factors that influence the crystal growth of the compounds. The purity and homogeneity of the crystals were detected by the ICP, SEM, EDX and TEM studies. Magnetic measurements show that the superconducting transition temperatures T_C of Ba_1−xK_xBiO₃ decrease from 22 K (for x = 0.35) to 8 K (for x = 0.55) with increasing the K doping level.     

Magnetic phase diagrams of the TbRh2−xPdxPdxSi2 and TbRu2−xPdxSi2 systems

The a.c. susceptibility and high field magnetization on TbRh_2−xPd_xPd_xSi₂ and TbRu_2−xPd_xSi₂ compounds were investigated up to 140 kOe. The (T,x) magnetic phase diagrams were determined. For both systems, an increase in the Pd content causes a decrease in the Néel temperature and changes the magnetization curves.     

High strength and good ductility of casting Al-Cu alloy modified by PrxOy and LaxOy

A modified Al-Cu alloy with high tensile strength and ductility of about 574.0 MPa and 10.4%, respectively, was obtained by adding multiple rare earth oxides (Pr_xO_y and La_xO_y) as modifier. Compared with the unmodified Al-Cu alloy, the tensile strength and ductility of the modified sample were increased by 24.3% and 42.5%, respectively. The improvement both in the strength and ductility may attribute to the finer crystal grains and dendrites, more homogeneously distributed θ′ phase precipitates and the intermetallic compounds formed at the crystal grain boundaries as well as in the space of the dendrites.     

Si3N4/Ti/Cu/Ni/Cu/Ti/Si3N4二次部分瞬间液相连接强度

采用Ti/Cu／Ni中间层对Si3N4陶瓷进行二次部分瞬间液相(PTLP)连接，研究连接工艺参数对Si3N4／Ti/Cu／Ni连接强度的影响，同时研究了连接强度随试验温度的变化规律。结果表明，在该试验条件下，室温连接强度随着二次连接温度的提高和二次保温时间的延长而提高，改变连接工艺参数对Si3N4／Ti/Cu／Ni二次PTLP连接界面反应层厚度无明显影响；连接强度在试验温度400℃时达到最大，随后随试验温度升高，连接强度降低，但在800℃前，其高温强度具有很好的稳定性。