银粉球磨过程中的晶粒变化研究

使用类球形银粉作为前驱体球磨得到片状银粉,采用X射线衍射(XRD)、扫描电镜(SEM)等方法研究片状银粉机械球磨过程银粉发生的物理变化包括晶体择优取向、衍射峰角度位移和宽化、形貌及粒度分布。结果表明,银粉球磨过程中(220)晶面出现择优取向,衍射峰发生高角度位移且应晶粒尺寸随着球磨时间延长显著减小。     

9Cr-ODS钢雾化合金粉的机械合金化过程

为说明在制备纳米结构氧化物弥散强化(Oxide Dispersion Strengthened,ODS)钢过程中机械合金化(Mechanical Alloying,MA)工艺参数对雾化9Cr-ODS钢预合金粉组织和性能的影响规律,利用扫描电镜、激光散射粒度分析仪、XRD和维氏硬度计研究了该钢预合金粉形貌、微观结构、维氏硬度随MA时间的变化规律。结果表明:随着MA时间的延长,雾化合金粉形貌由球状先变成不规则片状,后又变成等轴状;平均粒径先增大后又减小,在2 h后达到最大;晶粒尺寸在MA的最初阶段(0~2 h)迅速减小,MA 8 h后减小速度明显放缓;晶格畸变随MA时间变化规律与晶粒尺寸随MA时间变化规律相反;维氏硬度增加,但MA初期上升较快,而后上升速率逐渐降低。     

Mg70Al20Ca10合金机械合金化过程中的结构变化

以纯金属Mg、Al和Ca为原料,采用机械合金化的方法制备了Mg70Al20Ca10非晶态合金,分析了球磨过程中粉末试样的晶粒尺寸变化和相结构变化情况.结果表明,球磨过程中形成纳米晶和两种非晶相.Mg-Al-Ca合金在化学驱动力较小的条件下,可以通过机械驱动力的作用提高Ca、Al在Mg中的固溶度,导致非晶转变的发生.     

机械合金化法制备Cu-Nb合金过程中的形变孪生特性

采用机械合金化法制备纳米Cu-10%Nb合金,通过显微硬度测量以及高分辨透射电镜观察,对该合金粉末在室温球磨过程中的微观结构演变和形变孪生特性进行研究;利用局部应力集中模型分析形变孪晶的形核机制。结果表明:随着球磨时间的增加,该合金硬度(HV)不断升高,球磨120 h后可达4.8 GPa;该合金在球磨初期以位错胞结构为主;球磨50 h后,Cu平均晶粒尺寸减小至约50 nm,部分区域出现纳米形变孪晶;继续增加球磨时间,孪晶数量增加,孪晶界强化效果显著;由于孪生将促进纳米晶粒的进一步细化,球磨120 h后,纳米晶尺寸减小到20 nm以下。     

Al-V合金预磨状态对Al-Fe-V-Si-Nd机械合金化过程中显微组织演化的影响

采用高能球磨法制备Al89.5Fe6 .4V0 .7Si2 .4Nd合金粉末 ,并用X射线衍射技术研究了球磨过程中的组成。发现经 60h高能球磨 ,合金粉末的微观组织由Al非晶和Al3V相组成 ;Al V合金的预磨状态影响Al89.5Fe6 .4 V0 .7Si2 .4Nd合金机械合金化过程中显微组织演化。     

Al-Bi合金凝固过程及微合金化元素Sn的影响

实验研究了Al-Bi合金凝固过程及微合金化元素Sn的影响,发现添加微量Sn能有效改变Al-Bi合金的液-液相变过程、细化富Bi相粒子。Sn对富Bi相的细化效果随着Sn添加量的增加而增强,当添加量≥0.10%(质量分数)时即可达到最佳细化效果。建立了Al-Bi合金凝固过程中组织演变的动力学模型,模拟分析了微合金化元素Sn作用下Al-Bi合金凝固组织形成过程。结果表明,微量Sn可有效降低Al-Bi合金两液相间的界面能,提高富Bi相液滴的形核率,促进Al-Bi合金形成弥散型凝固组织。     

Pt-Ir-Ru合金的性能及显微结构

研究了固溶体范围的Pt-Ir-Ru合金的性能,结果表明：Ru和Ir对Pt-It和Pt-Ru合金的力学性能、电阻率和晶粒尺寸有大的影响。研究的合金有高的电阻率,这是由于铂族金属d－层电子散射、原子半径、电子结构和浓度引起。     

含铌H13钢热疲劳过程中的显微结构变化

对添加微量铌与不含铌的4Cr5MoSiV1钢(即H13钢)热疲劳性能进行了测试。结果表明,添加微量铌提高了4Cr5MoSiV1钢的热疲劳抗力。在热疲劳循环过程中,富铬碳化物M23C6粒子明显粗化。添加微量铌的4Cr5MoSiV1钢由于富铬碳化物的粗化受到抑止,且位错密度下降较慢,使得热疲劳裂纹的扩展相对缓慢,因而材料的热疲劳抗力提高。     

Ni-P非晶态合金形成过程中的粘度变化

非晶态合金在玻璃转变温度附近的粘滞流变与其液态合金的粘度密切相关。在测定了Ni-P二元合金表面张力和密度的基础上,研究了其粘度随温度的变化规律及其非晶态的粘滞流变过程。并得到可描述Ni-P合金从液态到非晶态固体的粘度与温度关系的统一表达式: η=C·exp[(B+bT(1-1/T))/(T-T_(vs)~o)]     

Phase transformation of nanocrystalline anatase powders during high energy planetary ball milling

1　INTRODUCTIONTitaniumdioxideisknowntoexistinthreecrys tallineformsofrutile ,anataseandbrookiteinnature .Rutileisthermodynamicallystablewhileanataseandbrookitecantransformirreversiblyandexothermicallytorutileoverarangeoftemperatures[1] .Inaddition ,therearetwohigh pressurephases ,srilankitewithorthorhombicstructureandTiO2 Ⅲ .Underhighpressure ,anataseandrutilecantransformtosri lankite[2 4 ] .Thesrilankitephasecantransformbacktorutileunderappropriateconditions[5] .Overthepastfew years …     

球磨时间和转速对球磨法制备纳米锑粉的影响

以250 μm大小的锑粉为原料,在添加相同含量蒸馏水和烷基酚聚氧乙烯醚的条件下,采用湿法机械球磨的方式制备出不同类型的锑基粉末.采用XRD、TEM及FT-IR对制备的锑基粉末的结构、形貌及粒径大小进行了表征分析,研究了球磨时间和球磨转速对锑粉制备的影响.结果表明:当锑粉原料中加入1 ml/g蒸馏水和0.2 ml/g OP-1O湿磨时,球磨转速为150r/min、球磨时间为18 h可制备出分散良好、粒径分布均匀、平均粒径约为10 nm的锑粉.     

Al-2.5%Pb合金在高能球磨和烧结过程中的组织结构变化

用机械合金化方法制备了Al-2.5wt%Pb合金,采用X射线衍射仪（XRD）和扫描电子显微镜（SEM）分析了Al-2.5wt%Pb合金在高能球磨和烧结过程中的组织结构变化。结果表明,该合金粉末经30 h球磨后,可以获得纳米级Pb颗粒均匀弥散分布在Al基体上的组织。在随后的烧结过程中,纳米相Pb的长大可以用Ostwald熟化的经典-LSW理论来描述。     

阿芬太尼对扁桃体腺样体切除患儿气管插管效果的随机双盲研究

目的：比较不同剂量阿芬太尼诱导对行扁桃体腺样体切除术患儿气管插管条件、血流动力学参数及苏醒质量的影响。方法：选取90例择期行扁桃体腺样体切除术的患儿,随机分为3组,每组30例,分别给予阿芬太尼20 μg/kg（A20组）、40 μg/kg（A40组）和60 μg/kg（A60组）进行麻醉诱导,余麻醉诱导和维持方案一致。评估3组患儿的Helbo-Hansen评分,记录麻醉诱导前（T0）、气管插管前（T1）、气管插管即刻（T2）、插管后1 min（T3）的平均动脉压（MAP）、心率（HR）以及自主呼吸恢复时间、睁眼时间、拔管时间、入恢复室后的躁动评分和药物不良反应。结果：与A20组比较,A40、A60组患儿Helbo-Hansen整体评分和咳嗽得分较低（P<0.05）。与T0比较,A40和A60组患儿在T1～T3时点MAP降低,A20组患儿T2、T3时点HR增快,A40组患儿T1时点HR减慢,A60组患儿T1～T3时点HR减慢（P<0.05）;与A20组比较,A40组患儿T1～T3时点MAP较低,T2、T3时点HR较慢,A60组患儿T1～T3时点MAP较低、HR较慢（P<0.05）。A60组患儿自主呼吸恢复时间和拔管时间延长（P<0.05）。结论：扁桃体腺样体切除术患儿麻醉诱导期给予阿芬太尼40 μg/kg或60 μg/kg联合丙泊酚3 mg/kg、罗库溴铵0.3 mg/kg均可使患儿获得满意的气管插管条件,而前者麻醉诱导期间生命体征更平稳,可实现术后快速拔管。     

Phase transition of Ni-Mn-Ga alloy powders prepared by vibration ball milling

This study investigated the phase transformation of the flaky shaped Ni-Mn-Ga powder particles with thickness around 1 μm prepared by vibration ball milling and post-annealing. The SEM, XRD, DSC and ac magnetic susceptibility measurement techniques were used to characterize the Ni-Mn-Ga powders. The structural transition of Heusler → disordered fcc occurred in the powders prepared by vibration ball milling (high milling energy) for 4 h, which was different from the structural transition of Heusler → disordered fct of the powders fabricated by planetary ball milling (low milling energy) for 4 h. The two different structures after ball milling should be due to the larger lattice distortion occurred in the vibration ball milling process than in the planetary ball milling process. The structural transition of disordered fcc → disordered bcc took place at ∼320 °C during heating the as-milled Ni-Mn-Ga powders, which was attributed to the elimination of lattice distortion caused by ball milling. The activation energy for this transition was 209 ± 8 kJ/mol. The Ni-Mn-Ga powder annealed at 800 °C mainly contained Heusler austenite phase at room temperature and showed a low volume of martensitic transformation upon cooling. The inhibition of martensitic transformation might be attributed to the reduction of grain size in the annealed Ni-Mn-Ga particles.     

CNTs辅助球磨对Zr粉形貌和氧化性能的影响

研究了不同球磨时间条件下CNTs辅助球磨对Zr粉形貌和氧化性能的影响。采用XRD和SEM分析了球磨过程中Zr粉的物相组成和形貌演变,采用热重（TG）法评估了Zr粉的氧化性能。结果表明：添加CNTs辅助球磨对Zr粉的物相组成没有影响,但是会影响Zr粉的形貌和氧化性能。不添加CNTs时,随着球磨时间的增加（1 h~3 h）,Zr粉粒径持续减小,球磨3 h后,Zr粉粒径由十几 μm减小到2~3 μm。添加CNTs辅助球磨后,Zr粉的颗粒细化过程滞后,球磨初期（1 h~2h）,Zr粉粒径没有显著变化,直到球磨时间延长到3 h时,Zr粉粒径才开始明显减小。这是因为CNTs在Zr颗粒表面的黏附和CNTs在Zr粉中的团聚阻碍了磨球对Zr颗粒的机械冲击和破碎作用。与直接球磨Zr粉相比,当所得Zr粉粒径相差不大时,添加CNTs辅助球磨使Zr粉的起始氧化温度和峰值氧化温度降低了11 ℃ ~37 ℃,这是因为CNTs的良好导热性促进了Zr粉氧化过程中的传热。另一方面,球磨时间少于2 h时,Zr/CNTs混合物中Zr粉的氧化增重量比纯Zr粉的增重量略有降低,但球磨时间超过2 h时,这种趋势出现反转。前者是因为短时间球磨时,CNTs引起Zr粉的局部团聚,阻碍了团聚体中Zr粉与氧气的接触,并且混合物中的Zr粉颗粒还没有被明显细化,这都降低了Zr粉的氧化程度;随后的反转趋势是因为球磨时间增加后,混合物中的Zr粉开始明显细化,促进了其氧化反应的进行,但是纯Zr粉由于颗粒尺寸提前细化而发生了显著的自发氧化,降低了活性Zr的含量。     

Effect of nonstoichiometry of NbCy and TaCy powders on their high-energy ball milling

Nanocrystalline powders of nonstoichiometric carbides NbC_y and TaC_y are experimentally obtained by high-energy milling of coarse-grained powders. For the first time, the effect of nonstoichiometry of NbC_y and TaC_y carbides on the particle size of produced nanopowders is studied. It is shown that the effect of nonstoichiometry on milling is manifested by the concentration dependences of the main characteristics (crystal structure parameters, energy of interatomic bonds, elastic properties) of milled nonstoichiometric compound. The experimental results on NbC_y (0.77 ≤ y ≤ 0.96) and TaC_y (0.81 ≤ y ≤ 0.96) milling are compared with the theoretical model dependences of the particle size D of nanopowders on the duration of milling t and the composition y of nonstoichiometric cubic carbides NbC_y and TaC_y. It is established that the carbide powders with the average nanoparticle size of 20–30 nm and specific surface area of 25–30 m² g^− 1 are produced by 15 h milling, all other factors being equal.     

Metal injection molding of W-Cu powders prepared by low energy ball milling

Low energy ball milled W/Cu powders were used for metal injection molding (MIM) in order to overcome the low powder volume fraction of MIM parts after debinding as well as the inherently poor sinterability of the W-Cu powder compacts. Ball milling was carried out using commercial fine W and Cu powders to form a powder mixture suitable for injection molding. W powders showed no change in either size or shape during the milling process, but the ductile Cu powders were easily deformed to a three-dimensional equiaxed shape, having a particle size comparable to that of W powders. This modification of powder characteristics by ball milling resulted in an improvement of the solid loading of roughly 58%, maintaining a high and uniform powder packing density in the feedstock. The densification behavior of W-Cu MIM parts is also discussed on the basis of the relationship between Cu composition and W particle size.     

高能球磨制备纳米WC-MgO粉末的反应模式及判据

以WO3、Mg和石墨粉为原材料,通过XRD、SEM和TEM对粉末的结构特征进行表征.结合Magini模型和杨君友模型界定扩散反应和自蔓延反应两种高能球磨合成WC-MgO反应模式的能量区域,并通过球磨能量图阐明球磨速度、球料比和球磨时间等工艺参数对不同反应模式的影响.结果表明:在一定球磨条件下,当有效强度因子大于38.24 kJ/(g·s)时,合成WC-MgO的反应模式为自蔓延反应,所需的球磨总能量介于21.51×109J/g和61.82×109J/g之间;当有效强度因子为22.12～38.24 kJ/(g·s)时,合成WC-MgO的反应模式为扩散反应,所需的最小球磨总能量为112.83×109J/g.     

Mechanical alloying behaviors of Mo-Si-B-based alloy from elemental powders under different milling conditions

Elemental powder mixtures with the composition of Mo-12Si-10B-3Zr-0.3Y(at%)were milled in a planetary ball mill using hardened stainless-steel milling media under argon atmosphere.Effects of milling time,milling speed,process control agent,ball-to-powder ratio and milling ball size on the mechanical alloying processes were investigated from the points of morphology,internal structure,grain size,microstrain,phase constituent and issolution of solute atoms.It is shown that under all conditions,the microstructural evolutions of mechanically milled powder particles are similar.The morphological evolution can roughly be divided into five stages:individual particle,irregular blocky composite particle,flakeshaped particle,agglomerate and single particle.The internal structure generally undergoes five stages:individual particle,coarse lamellar structure,fine lamellar structure,non-uniformly mixed structure and plum-pudding structure.Regardless of exceptional cases,the grain size of Moss decreases and its microstrain increases with the increase in milling time.Si and Zr atoms are dissolved into Mo gradually with the progress of milling.However,the evolutionary rates change significantly with milling conditions.The most significant influencing factor among different milling conditions is the input power from the mill to the powders,which plays a decisive role in the milling process.