添加钕对Mg2Ni储氢合金的结构和电极性能的影响

利用两步法制备了一系列添加Nd的三元Mg2-xNdxNi合金。XRD分析证实，当x=0．05，0．1时，制得的三元Mg2-xNdxNi合金均为Mg2Ni单相合金；三元Mg18Nd0．2Ni(x=0．2，0．3)合金为三相合金，三相分别为Mg2Ni，NdNi，NdMgNi4。模拟电池测试结果表明，同Mg2Ni合金相比，球磨10h的三元Mg1．8Nd0．2Ni合金和Mg17Nd03Ni合金电极的放电容量提高明显，且Mg17Nd03Ni合金电极的循环性能有明显改善。这极有可能与合金中NdMgNi4相的存在以及球磨形成的微结构有关。     

MoSi2弥散强化铜合金的密度研究

用高能球磨冷压烧结的方法制备了MoSi2弥散强化铜合金。分析了烧结温度、球磨方式和压坯密度对比的弥散强化铜合金烧结密度的影响。结果表明：烧结温度对其烧结密度的影响最大，其最佳烧结温度为950℃；球磨方式的影响次之，但湿磨比干磨效果好；压坯密度对烧结密度的影响不明显。     

镁基储氢复合材料放氢过程相转变速率研究

用机械合金化方法，在充氢球磨条件下，经不同时间球磨，制备Mg—Ni—MnO2储氢材料。用自行研制的储氢性能测试装置对这种材料放氢过程中的相转变速率进行了测试，并与经相同的球磨工艺制备的Mg—Ni、Mg—MnO2储氢材料的储氢性能进行了比较。试验结果表明：球磨时间对Mg—Ni—MnO2储氢材料的粒度有影响；颗粒大小对放氢过程的相转变速率有影响。颗粒越小，相转变速率的相对峰值越大，完成相变所用的时间相对要短；Ni与MnO2同时催化的镁基储氢材料放氢性能明显高于Ni或MnO2单独催化的储氢材料。     

放电等离子烧结快速制备高钪含量铝钪合金

采用放电等离子烧结技术制备高钪含量Al-Sc合金,利用扫描电子显微镜、能谱仪和X射线衍射仪等设备对球磨前后Al-Sc合金粉末的形貌、相组成以及不同温度快速烧结样品的显微组织结构进行观察和分析,研究烧结温度对Al-Sc合金显微组织的影响。结果表明:球磨后粉末的形状较规则,其颗粒尺寸为25~45mm,并初步实现了机械合金化,除Al、Sc相以外,有少量Al3Sc和AlSc2相生成。放电等离子烧结可实现高钪含量铝钪合金的快速致密化,成功制备出钪含量30%(质量分数)的铝钪合金,通过调整烧结工艺参数,烧结样品的相对密度可达92.19%;当烧结温度高于500℃时,所得样品致密,无孔洞,且无明显晶界;随着烧结温度的提高,Sc相与第二相融合,形成Al3Sc、AlSc2等第二相,存在于合金中,且Al3Sc相呈现逐渐增强的趋势。     

W-10%TiC复合材料的制备与力学性能研究

采用高能球磨手段制备了W-10%TiC(质量分数, 下同)纳米复合粉体, 并采用热压方法烧结成致密块体, 研究了高能球磨、烧结温度、烧结时间及烧结压力对复合材料致密度和力学性能的影响. 结果表明: 高能球磨后, 复合粉体的颗粒形状近似球形, 粒径均匀, 平均粒径为100 nm, 并且纳米复合粉体的烧结温度大大降低, 其原因是粉体的颗粒细小、扩散系数高、表面能高等性质及球磨过程中少量Fe, Ni杂质的引入. 对所制备纳米粉体而言, 较合适的烧结工艺为: 1700 ℃, 30 Mpa压力下烧结60 min, 在此工艺条件下制备的复合材料的致密度达到98.4%, 抗弯强度和断裂韧性分别达到: 681 Mpa, 6.24 Mpa·m1/2.     

粉末冶金M2高速钢的制备与组织性能研究

采用机械球磨法制备了M2高速钢(HSS)粉末,研究了烧结温度对数控机床用高速钢显微组织、硬度、抗弯强度等性能的影响,并分析了热处理对高速钢显微组织和力学性能的影响。结果表明,球磨时间为16 h时高速钢粉末的颗粒分布均匀、平均尺寸最小;在烧结温度为1 245℃时,高速钢试样中未见显微孔洞或者裂纹等缺陷存在,同时碳化物细小、弥散;烧结温度为1 235℃时,高速钢试样的烧结机制为固相烧结,相对密度为87.2%,升高烧结温度至1 245℃及以上时,高速钢试样的烧结机制为液相烧结,相对密度保持在98%以上;随着烧结温度的升高,高速钢试样的磨损失重呈现先减小后增大的趋势,抗弯强度呈现先增加后减小的趋势,在烧结温度为1 245℃时具有较小的磨损失重和最大的抗弯强度;淬火和回火热处理可以进一步提高烧结试样的洛氏硬度。     

球磨时间与含碳量对铜碳复合材料组织与性能的影响

将铜粉和碳粉分别按质量分数为Cu-2%C和Cu-8%C配比混合,经过高能球磨得到铜-碳复合粉末,然后冷压成形,压坯在H2气氛、820℃温度下烧结2 h,获得铜-石墨块体材料。采用X射线衍射、扫描电镜、透射电镜以及电导率测试仪等对高能球磨后的复合粉末和块体材料的物相组成、微观组织结构与导电性能进行分析,研究球磨时间与碳含量对铜-碳复合粉末与块体材料的组织结构及性能的影响。结果表明,铜碳混合粉末经高能球磨,得到亚稳态Cu(C)过饱和固溶体,经固相烧结后形成"蠕虫状"组织。随球磨时间延长,材料密度先增加后减小,球磨24 h时密度最大,Cu-2%C和Cu-8%C材料的密度分别为7.58 g/cm3和6.79 g/cm3;电导率随球磨时间延长而增加,球磨72 h时Cu-2%C和Cu-8%C的电导率分别为54.2%IACS和33.0%IACS。     

添加剂CeO_2对La_2Mg_(17)-50% Ni储氢性能的影响

研究了球磨添加CeO2对La2Mg17-50%(质量分数,下同)Ni复合合金的相结构和储氢性能的影响,并对合金的形貌和吸放氢性能进行了检测。XRD结果表明,球磨加入CeO2后,在La2Mg17-50%Ni合金中除了Mg2Ni和Ni相外,产生Ce Mg12相。SEM形貌图清晰地看见CeO2附在La2Mg17-50%Ni合金表面上呈白色小颗粒。吸氢动力学性能表明,加入CeO2后,使La2Mg17-50%Ni合金的最大吸氢量从3.298%增加到3.594%。添加CeO2后合金的最佳饱和吸氢温度降为200℃(3 MPa),且吸氢动力学性能提高至1 min内的吸氢量达到3.382%,是其最大吸氢量的94%。然而,CeO2在放氢过程中的积极作用并不明显。     

机械合金化Mg-LaNi5合金的研究

采用X射线衍射(XRD)、扫描电子显微镜(SEM)、差热分析(DTA)等测试方法研究了新型材料Mg-69％LaNi5(质量分数)的组织形貌及热稳定性能等。结果表明：该合金在转速为280r／min的条件下球磨250h后形成了短程有序或无序的镧、镁、镍等非晶及MgNi2纳米晶(3nm)组织；所得样品的颗粒形状主要为规则的球形或近球形，还有少量多角形等不规则形状。球磨样品在763K温度下保温35d，得到热稳定性较好的具有纳米尺度(2．5nm)的Mg2NiLa，Mg2Ni，MgNi2三相合金。     

烧结温度对TiC_(0.7)N_(0.3)-WC-TaC-Mo-(Ni,Co)金属陶瓷材料组织与性能的影响

采用粉末冶金工艺制备TiC_(0.7)N_(0.3)-WC-TaC-Mo-(Ni,Co)金属陶瓷材料。通过密度测试仪、万能力学试验机、维氏硬度测试仪、X射线衍射分析仪和扫描电镜等方法检测金属陶瓷样品的密度、抗弯强度、硬度、物相结构和微观结构,比较分析不同烧结温度对TiC_(0.7)N_(0.3)-WC-TaC-Mo-(Ni,Co)金属陶瓷材料的组织结构和性能的影响。结果表明:烧结温度对材料的致密化过程和结构性能产生重要影响;当烧结温度为1450℃时,材料的抗弯强度达到1110MPa,显微硬度达到1200HV;材料组织致密,环形相连续分布,硬质相细小、均匀,能有效抑制在应力作用下材料内部裂纹的扩展,增加韧性断裂特征。     

Effect of Yttrium on Microstructures and Preparation and Structure of Mg2-xRExNi (RE=La,Ce,Pr,Nd,Y) Ternary Alloys

A series of Mg2-xNdxNi(x=0.05,0.1,0.2,0.3)alloys and Mg1.95RE0.05Ni(RE= La,Ce,Pr,Nd,Y)ternary alloys were prepared by ball milling of mixted powder of Mg,Ni,RE and sintering under the protection of argon.XRD analysis shows that Mg2-xNdxNi(x=0.05,0.1)and Mg1.95RE0.05Ni consist of single phase with the same crystal structure as Mg2Ni.While three-phase alloys including Mg2Ni,NdNi and NdMgNi4 were formed in Mg1.8Nd0.2Ni and Mg1.7Nd0.3Ni alloys respectively.The lattice constants of Mg2Ni in those ternary alloys were calculated.The decomposition of Mg2Ni occurs in the milling process of Mg2Ni and Mg1.95RE0.05 Ni alloys respectively.For the latter,another earlier reaction occurs in milling process,which means that atoms of RE are separated from crystal structure of Mg2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.     

Preparation and Structure of Mg2-xRExNi （RE = La, Ce, Pr, Nd, Y） Ternary Alloys

A series of Mg2-xNdxNi (x =0.05, 0.1, 0.2, 0.3) alloys and Mg1.95RE0.05Ni (RE= La, Ce, Pr, Nd, Y)ternary alloys were prepared by ball milling of mixted powder of Mg, Ni, RE and sintering under the protection of argon. XRD analysis shows that Mg2-xNdxNi (x = 0.05, 0.1 ) and Mg1.95RE0.05Ni consist of single phase with the same crystal structure as Mg2Ni. While three-phase alloys including Mg2Ni, NdNi and NdMgNi4 were formed in Mg1.8Nd0.2Ni and Mg1.7Nd0.3Ni alloys respectively. The lattice constants of Mg2Ni in those ternary alloys were calculated. The decomposition of Mg2Ni occurs in the milling process of Mg2Ni and Mg1.95RE0.05Ni alloys respectively. For the latter, another earlier reaction occurs in milling process, which means that atoms of RE are separated from crystal structure of Mg2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.     

粗晶硬质合金硬度和强度影响因素的分析研究

采用变量搜索试验设计方法,研究了合金碳含量、烧结工艺、钴含量、粘结相成分配比、球料比、球磨时间这六个因素及因素间两两交互作用对粗晶硬质合金硬度、横向断裂强度的影响。结果表明:钴含量、球磨时间是影响硬度的主要因素;烧结工艺、球磨工艺和粘结相成分配比是影响合金强度的主要因素。适当提高烧结温度,可得到缺陷更少、粘结相分布更为均匀故强度更高的粗晶硬质合金。     

固相烧结辅助高温球磨合成LiNi_xMn_(2-x)O_4

以氢氧化锂、硝酸镍、二氧化锰为原料,用固相烧结辅助高温球磨方法,合成了具有Ni掺杂的LiMn_2O_4正极材料。研究了Ni在不同掺杂量时对材料的相结构、形貌和充放电性能的影响,并与未掺杂Ni的LiMn_2O_4进行对比。结果表明,掺Ni后材料的放电比容量随着掺杂量的增大逐渐减小,而材料的容量保持率相比未掺杂时略有提高;当掺杂量x=0.05时,所得产物的充放电性能最佳,首次放电容量达到122.9mAh/g,充放电容量保持率在40次循环后为97.48%。     

Microstructure and improved hydrogen storage properties of Mg based alloy powders prepared by modified milling method

Abstract

In this study, the modified preparation method of combining planetary and vibratory ball milling was proposed to prepare Mg based hydrogen storage alloy powders. The comparison of micromorphology and hydrogen storage behaviour between Mg₂Ni prepared using the modified and conventional preparation methods were investigated experimentally. The comparison results showed that the combination of first planetary and then vibratory ball milling has more favourable effect on improving both the kinetics and the thermodynamics of ball milled Mg₂Ni alloys. The sample synthesised by first planetary milling for 40 h and then vibratory milling for 30 h has faster hydrogen absorption kinetics and lower dehydriding onset temperature than those prepared by the single method of planetary or vibratory milling and hydriding combustion synthesis owing to its popcorn-like microstructure. Moreover, this kind of modified method reduces the reaction enthalpy and activation energy by up to ～18 and 22% respectively.     

包裹型SiO2/Al复合粉体的制备及烧结性能研究

为了克服金属陶瓷两相分布不均、界面不润湿和难以烧结致密等难题,采用球磨技术将增强相均匀包裹在基体材料表面,研究包裹型SiO₂/Al复合粉体的球磨制备工艺及其烧结性能,提高金属陶瓷的综合性能。结果表明,随着球磨时间的延长,SiO₂/Al复合粉体的比表面积先增大后减小,球磨6 h获得的复合粉体比表面积最大,达到8.1 m2·g?1。随着球料比的增大,SiO₂/Al复合粉体的比表面积先增大后减小,说明SiO₂包裹在Al粉表面的量呈现先增多再减少的趋势。随着球磨转速的增大,SiO₂/Al复合粉体比表面积先增大后减小。随着烧结温度的提高,SiO₂/Al金属陶瓷表面硬度先增高后降低,在烧结温度为900 ℃时,SiO₂/Al金属陶瓷的表面硬度达到最高。球磨时间为6 h,球料比为2:1,球磨转速为360 r·min?1,烧结温度900 ℃可以获得性能较佳的SiO₂/Al金属陶瓷。     

W-4.9Ni-2.1Fe 高比重合金的摩擦磨损行为

采用高能球磨和放电等离子体烧结技术制备W-4.9Ni-2.1Fe高比重合金,研究不同球磨时间对合金显微组织结构和摩擦磨损行为的影响. 结果表明:当球磨时间较短（2 h）时,合金粉末中Ni、Fe元素仍以单质的形式存在;随着球磨时间的延长,Ni(Fe)溶入W晶格中形成W的过饱和固溶体,W衍射峰强度逐渐变弱,峰形明显宽化,合金试样的相对密度呈下降趋势;适量的球磨时间（24 h）,既可以保证合金中黏结相的含量和均匀分布,又不至于引入过量的杂质元素而引起合金成分改变,合金拥有最优的耐摩擦磨损性能.      

Solid state reactions between Ni and Al powders induced by plastic deformation

The solid state reactions induced by high-energy ball milling of Al/Ni elemental mixtures at 25, 33, 50, 67 and 75 Ni at.% have been studied by X-ray diffraction and electron microscopy. The thermal stability of the reaction products at different stages of milling has been investigated by differential scanning calorimetry. The sequence of reactions observed in each sample depends even in its early steps on the initial composition of the mixture. The end-product of the milling process is, in some cases, a metastable phase. For long milling times, in fact, we have observed the formation of a metastable f.c.c. solid solution at the two Ni-rich compositions, of the AlNi phase at 50 and 33% Ni and of the Al₃Ni compound at 25% Ni. Thermal treatment of samples at an early stage of milling shows, contrary to the behaviour induced by plastic deformation, that at all compositions the first thermally driven reaction is the formation of Al₃Ni. The experimental observation of an enhancement of Ni diffusivity in Al during ball milling, suggests that this high diffusivity is the main cause of the observed differences.     

Titanium Carbide Reinforcement in Iron Matrix Through Carbothermal Reduction of Mechanically Milled Hematite and Anatase

This study investigated the influence of the duration of milling on the formation of TiC-reinforced iron composite through carbothermal reduction of a hematite and anatase mixture. Mixtures of hematite, anatase, and graphite powders were mechanically activated in a planetary ball mill in an argon atmosphere with different milling times (0 to 60 hours). X-ray diffraction showed that with increasing milling time, the crystallite size of the hematite decreased to nanometer range, accompanied by an increment in internal strain. Prolonging the milling process increased dislocation density of the as-milled powder. The as-milled powder was consolidated by cold pressing under 100 MPa and sintered in vacuum at 1373 K (1100 °C). High temperature during sintering resulted in the formation of iron and titanium carbide phases as confirmed by X-ray diffraction, scanning electron microscope, and energy dispersive X-ray analysis. Without mechanically activated milling, the reaction forming TiC did not occur during sintering at 1373 K (1100 °C), indicating a reduction in reaction temperature promoted by mechanical milling. An increase in milling time resulted in an increase in sintered density and hardness due to the fineness of the composite powder, together with complete TiC and iron phase formation.