磁粉粒度对烧结Sm(Co0.72Fe0.15Cu0.1Zr0.03)7.5的磁性能的影响

采用粉末冶金法制备烧结Sm(Co0.72Fe0.15Cu0.1Zr0.03)7.5,研究磁粉粒度对磁体磁性能的影响.结果表明,增加球磨时间将细化磁粉粒度,提高磁粉的比表面积,有利于降低磁体的烧结温度.球磨5,7,9,11 h的磁粉的最佳烧结温度分别为1225,1225,1215,1215 ℃.磁粉球磨9 h,烧结温度为1215 ℃条件下制备的磁体的综合磁性能最优剩磁Br=0.94 T,感应矫顽力Hcb=708.4 kA·m-1,最大磁能积(BH)max=171.9 kJ·m-3,内禀矫顽力Hci=2276.6 kA·m-1;温度稳定性良好,长径比为0.7的磁体经550 ℃老化2 h后的磁通不可逆损失低于5%,有望应用于550 ℃环境中.     

纳米晶复合Nd2Fe14B/α-Fe合金制备与磁性能的研究

采用熔体快淬及晶化处理工艺制备Nd11Fe71Co8V1.5Cr1B7.5纳米晶合金。经21m·s-1快淬及640℃ 4min晶化处理后,制成的粘结磁体的磁性能最佳,为:Br=0.64T,JHc=903.5kA·m-1,(BH)max=71kJ·m-3。添加Cr元素可提高内禀矫顽力,从而提高最大磁能积。     

双相纳米晶永磁体的研究

Nd8 .5Fe75Co5Cu1 Nb1 Zr3B6 .5合金熔体经 18m·s- 1 快淬 ,在 670℃ / 4min退火处理后 ,制备成的粘结磁体的最佳磁性能为 :Br=0 .68T(6 8kGs) ,JHc=62 0 .3kA·m- 1 (7 8kOe) ,(BH) max=74kJ·m- 3(9 3 3MGOe)。在低Nd合金中复合添加Zr和Cu ,提高了内禀矫顽力 ,改善了磁滞回线的矩形度 ,从而提高了最大磁能积。     

Co含量对Pr10Fe74-xCo10+xC4B4 (x=0,2,4,6,8) 快淬条带的磁性能的影响

用快淬方法制备了Pr10Fe74-xCo10+xC4B4 (x=0,2,4,6,8) 条带,研究了成分和工艺对条带磁性能的影响.实验发现,当x=2,带速是20 m·s-1时,条带的磁性能最佳,其剩磁Jr=0.94 T,矫顽力μ0 iHc=0.96 T,最大磁能积 (BH)max=127.32 kJ·m-3.通过Henkel-plot分析,发现x=2,带速为20 m·s-1的样品中的晶间交换作用最强,因而能获得最佳的磁性能.     

粉体特性对Sm(Co,Fe,Cu,Zr)_(6.9)高温永磁合金磁性能的影响

分别采用球磨和气流磨工艺制备了Sm(Co,Fe,Cu,Zr)6.9合金粉体。研究了粉体的形状和粒径对烧结磁体磁性能的影响规律。与球磨工艺相比,气流磨制备的粉体颗粒外形更规则。在平均粒径相同的情况下,采用气流磨粉体烧结时效后的永磁合金样品取向度更高,室温剩余磁化强度Mr、最大磁能积(BH)max和500℃条件下的Mr,iHc,(BH)max均优于采用球磨粉体经相同工艺制得的样品。外形规则的气流磨粉体制得的合金样品在室温和500℃条件下的磁性能均随粉体粒径减小呈先升高后降低的趋势,室温下6.8μm气流磨粉体烧结时效样品的磁性能达到最优,为Mr=8092 Gs,iHc=18.3 kOe,(BH)max=123 kJ.m-3;该样品在500℃条件下的磁性能仍达到Mr=5177 Gs,iHc=9.0 kOe,(BH)max=39 kJ.m-3。     

改进片铸与烧结技术制备高性能钕铁硼磁体的研究

通过优化合金成分设计与改进速凝片铸技术、烧结技术,应用国内通用的工业生产烧结钕铁硼磁体的各类原材料,在工业生产线上实现了45UH高性能烧结钕铁硼磁体的批量生产。SEM观察和XRD分析结果表明:磁体具有比较高的取向度;其显微组织致密、精细而均匀,平均晶粒尺寸约为5μm。45UH烧结钕铁硼磁体的典型磁性能为Br=1.363 T,Hcb=1060 kA.m-1,Hcj=2140 kA.m-1,Hk=1625 kA.m-1,(BH)max=366.0 kJ.m-3;其Hcj/79.6 kA.m-1+(BH)max/7.96 kJ.m-3=72.8。在295～453 K温度区间,其剩磁与内禀矫顽力的温度系数分别为-0.108%.K-1和-0.486%.K-1。当L/D=0.7时,在473 K保持2 h磁体开路磁通不可逆损失为4.1%左右。批量生产的45UH烧结钕铁硼磁体,其常温磁性能优异,温度稳定性良好。     

高性能含镨快淬(Nd,Pr)12(FeCoZr)82B6粘结磁体的制备

采用过快淬加晶化退火处理的方法,研究了含有Pr的近正分快淬(Nd,Pr)12(FeCoZr)82B6粘结磁体制备工艺,粘结出的磁体磁性能为:Br=0.669T,Hci=811kA·m-1,Hcb=434kA·m-1,(BH)m=75kJ·m-3。合金快淬态的组成和显微结构、晶化退火温度、晶化退火时间直接影响磁体的磁性能,以24m·s-1速度快淬,并在655℃退火10min,可获得最佳磁性能。实验制备的粘结快淬(Nd,Pr)12(FeCeZr)82B6磁体(密度6 1g·cm-3)磁性能为:Br=0 669T,Hci=811kA·m-1,Hcb=434kA·m-1,(BH)m=75kJ·m-3     

铌和锆对(Nd,Pr)2Fe14B/α-Fe快淬合金晶化和磁性能的影响

研究了Nb和Zr添加对快淬纳米双相(Nd,Pr)2Fe14B/α-Fe合金晶化行为和磁性能的影响. 结果表明 (Nd0.4Pr0.6)8.5Fe85.5B6合金非晶晶化时, 在α-Fe相初始晶化后, 出现了(Nd,Pr)3Fe62B14亚稳相, 最终亚稳相分解形成(Nd,Pr)2Fe14B和α-Fe两相组织; (Nd0.4Pr0.6)8.5Fe84.5Nb0.5Zr0.5B6非晶晶化时, 同时析出α-Fe相和(Nd,Pr)2Fe14B相. 这说明添加Nb和Zr可避免亚稳相的形成并细化晶粒, 最大磁能积(BH)max从复合添加前的107.5上升到143.6 kJ·m-3. 而且, Nb和Zr原子在非晶晶化过程中可以部分取代Nd和Pr的晶位, 使稀土原子可以参与形成更多的硬磁相, 进一步提高了内禀矫顽力iHc. 合金(Nd0.4Pr0.6)8.5Fe84.5Zr0.5Nb0.5 B6经690 ℃退火10 min后磁性能最优, Br=1.10 T, iHc=534.2 kA·m-1, (BH)max=143.6 kJ·m-3.     

热处理对非晶态合金Nd_9(FeCoZrAl)_(85)B_6磁性能的影响

采用XRD等方法研究了单辊急冷法制备的低钕含量的快淬Nd9(FeCoZrAl) 85 B6 非晶态合金在不同热处理工艺下的相组成、晶粒尺寸大小及其磁性能变化规律。热处理工艺对Nd2 Fe1 4 B相和α Fe相析出、晶粒尺寸大小和合金的磁性能具有明显影响。当热处理温度较低时 ,Nd2 Fe1 4 B相析出不充分 ,并出现不均匀长大 ,其晶粒尺寸反而较大 ;当热处理温度过高时 ,Nd2 Fe1 4 B相虽然析出充分 ,但其晶粒尺寸也明显长大 ;只有当热处理温度适中 ( 685℃ /3 0min) ,既可保证Nd2 Fe1 4 B相析出充分 ,又不至于明显长大 ,才能使Nd2 Fe1 4 B相和α Fe相、Nd2 Fe1 4 B相和Nd2 Fe1 4 B相晶粒间的磁耦合效应达到最佳 ,从而增大剩磁 ,使该合金的磁性能也达到最佳 ,制得的粘结磁体性能 :剩磁Br=65 5mT ,内禀矫顽力jHc=64 4 3kA·m- 1 ,矫顽力bHc=3 79 0kA·m- 1 ,最大磁能积 (BH) m=65 68kJ·m- 3。     

制备工艺对Pr2Fe14B/α-Fe纳米复合永磁材料组织与磁性的影响

用XRD,TEM和VSM等方法研究了快淬法制备的Pr2Fe14B/α Fe纳米复合永磁薄带的显微结构与磁性。比较了直接快淬和非晶晶化两种制备工艺对合金薄带显微结构和磁性能的影响。通过对Pr8Dy1Fe74.5Co10Nb0.5B6合金薄带高压退火,获得了Br=1.11T,Hci=816.0kA·m-1和(BH)max=188.8kJ·m-3的高性能。     

OH(3) (-) and O(2)H(5) (-) double Rydberg anions: predictions and comparisons with NH(4) (-) and N(2)H(7) (-)

A low barrier in the reaction pathway between the double Rydberg isomer of OH(3) (-) and a hydride-water complex indicates that the former species is more difficult to isolate and characterize through anion photoelectron spectroscopy than the well known double Rydberg anion (DRA), tetrahedral NH(4) (-). Electron propagator calculations of vertical electron detachment energies (VEDEs) and isosurface plots of the electron localization function disclose that the transition state's electronic structure more closely resembles that of the DRA than that of the hydride-water complex. Possible stabilization of the OH(3) (-) DRA through hydrogen bonding or ion-dipole interactions is examined through calculations on O(2)H(5) (-) species. Three O(2)H(5) (-) minima with H(-)(H(2)O)(2), hydrogen-bridged, and DRA-molecule structures resemble previously discovered N(2)H(7) (-) species and have well separated VEDEs that may be observable in anion photoelectron spectra.     

Mixed ligand titanium(IV) complexes. Chlorobis(dithiocarbamato)bis(methylsalicylato)titanium(IV) andbis(dithiocarbamato)bis(methylsalicylato)titanium(IV)

Summary Dichlorobis(methylsalicylato)titanium(IV) reacts with potassium or amine salts of dialkyl or diaryl dithiocarbamates in 11 and 12 molar ratios in anhydrous benzene (room temperature) or in boiling CH₂Cl₂ to yield mixed ligand complexes: (AcOC₆H₄O)₂ Ti(S₂CNR₂)Cl (1) and (AcOC₆H₄O)₂ Ti(S₂CNR₂)₂ (2), R=Et, n-Pr, n-Bu, cyclo-C₄H₈ and cyclo-C₅H₁₀. These compounds are moisture sensitive and highly soluble in polar solvents. Molecular weight measurement in conjunction with i.r.,¹H and¹³C n.m.r. spectral studies suggest coordination number 7 and 8 around titanium(IV) in (1) and (2) respectively.     

Syntheses and structures of the infinite chain compounds Cs(4)Ti(3)Se(13), Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14)

The alkali metal/group 4 metal/polychalcogenides Cs(4)Ti(3)Se(13), Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14) have been synthesized by means of the reactive flux method at 823 or 873 K. Cs(4)Ti(3)Se(13) crystallizes in a new structure type in space group C(2)(2)-P2(1) with eight formula units in a monoclinic cell at T = 153 K of dimensions a = 10.2524(6) A, b = 32.468(2) A, c = 14.6747(8) A, beta = 100.008(1) degrees. Cs(4)Ti(3)Se(13) is composed of four independent one-dimensional [Ti(3)Se(13)(4-)] chains separated by Cs(+) cations. These chains adopt hexagonal closest packing along the [100] direction. The [Ti(3)Se(13)(4-)] chains are built from the face- and edge-sharing of pentagonal pyramids and pentagonal bipyramids. Formal oxidation states cannot be assigned in Cs(4)Ti(3)Se(13). The compounds Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14) crystallize in the K(4)Ti(3)S(14) structure type with four formula units in space group C(2)(h)()(6)-C2/c of the monoclinic system at T = 153 K in cells of dimensions a = 21.085(1) A, b = 8.1169(5) A, c = 13.1992(8) A, beta = 112.835(1) degrees for Rb(4)Ti(3)S(14);a = 21.329(3) A, b = 8.415(1) A, c = 13.678(2) A, beta = 113.801(2) degrees for Cs(4)Ti(3)S(14); a = 21.643(2) A, b = 8.1848(8) A, c = 13.331(1) A, beta = 111.762(2) degrees for Rb(4)Hf(3)S(14); a = 22.605(7) A, b = 8.552(3) A, c = 13.880(4) A, beta = 110.919(9) degrees for Rb(4)Zr(3)Se(14); a = 22.826(5) A, b = 8.841(2) A, c = 14.278(3) A, beta = 111.456(4) degrees for Cs(4)Zr(3)Se(14); and a = 22.758(5) A, b = 8.844(2) A, c = 14.276(3) A, beta = 111.88(3) degrees for Cs(4)Hf(3)Se(14). These A(4)M(3)Q(14) compounds (A = alkali metal; M = group 4 metal; Q = chalcogen) contain hexagonally closest-packed [M(3)Q(14)(4-)] chains that run in the [101] direction and are separated by A(+) cations. Each [M(3)Q(14)(4-)] chain is built from a [M(3)Q(14)] unit that consists of two MQ(7) pentagonal bipyramids or one distorted MQ(8) bicapped octahedron bonded together by edge- or face-sharing. Each [M(3)Q(14)] unit contains six Q(2)(2-) dimers, with Q-Q distances in the normal single-bond range 2.0616(9)-2.095(2) A for S-S and 2.367(1)-2.391(2) A for Se-Se. The A(4)M(3)Q(14) compounds can be formulated as (A(+))(4)(M(4+))(3)(Q(2)(2-))(6)(Q(2-))(2).     

Bis(trifluoroacetyl) peroxide, CF(3)C(O)OOC(O)CF(3)

Pure, highly explosive CF(3)C(O)OOC(O)CF(3) is prepared for the first time by low-temperature reaction between CF(3)C(O)Cl and Na(2)O(2). At room temperature CF(3)C(O)OOC(O)CF(3) is stable for days in the liquid or gaseous state. The melting point is -37.5 degrees C, and the boiling point is extrapolated to 44 degrees C from the vapor pressure curve log p = -1875/T + 8.92 (p/mbar, T/K). Above room temperature the first-order unimolecular decay into C(2)F(6) + CO(2) occurs with an activation energy of 129 kJ mol(-1). CF(3)C(O)OOC(O)CF(3) is a clean source for CF(3) radicals as demonstrated by matrix-isolation experiments. The pure compound is characterized by NMR, vibrational, and UV spectroscopy. The geometric structure is determined by gas electron diffraction and quantum chemical calculations (HF, B3PW91, B3LYP, and MP2 with 6-31G basis sets). The molecule possesses syn-syn conformation (both C=O bonds synperiplanar to the O-O bond) with O-O = 1.426(10) A and dihedral angle phi(C-O-O-C) = 86.5(32) degrees. The density functional calculations reproduce the experimental structure very well.