烧结Nd-Fe-B磁体多主相复合制备及微观结构研究

利用双合金混粉法添加Dy实现烧结Nd-Fe-B磁体多主相复合制备,研究磁体的磁性能和微观结构。研究结果表明:单主相合金制备烧结Nd-Fe-B磁体时,主相晶粒中Dy含量差别不大,颗粒状富Nd相中所含Dy含量明显高于主相晶粒中所含Dy含量。双合金混粉法制备烧结Nd-Fe-B磁体时,能够提高磁体的取向,磁体中存在多主相晶粒复合;富Nd相中含Dy元素的总量降低,主相晶粒中含Dy元素的总量增加。烧结Nd-Fe-B磁体的多主相复合制备可以利用双合金混粉法得以实现;同时,相同合金成分时,双合金混粉法制备出的烧结Nd-Fe-B磁体的磁性能优于单合金法制备出的磁体,烧结Nd-Fe-B磁体的多相复合制备能够提高磁体的磁性能。     

Nd-Fe-B磁体烧结过程晶粒长大行为的研究

定量描述了Nd-Fe-B磁体烧结过程晶粒长大行为，分析了烧结温度、烧结时间、合金粉末粒度及其分布对烧结过程晶粒长大的影响，讨论了烧结过程晶粒长大机制。在Nd-Fe-B磁体烧结过程开始之后的0—1h时间区段，晶粒长大迅速；随着烧结时间的延长，晶粒长大速度减小。合金粉末平均粒度增大，或者合金粉末粒度分布范围增宽，显著促进Nd-Fe-B磁体烧结过程中晶粒的长大。在Nd-Fe-B磁体的烧结过程中，存在两类晶粒长大机制，即Nd2Fe14B颗粒的溶解与析出、Nd2Fe14B颗粒的并合与长大。Nd2Fe14B颗粒的并合与长大不仅使磁体的平均晶粒尺寸增大，也使晶粒尺寸分布范围增宽，是烧结Nd-Fe-B磁体显微组织中出现异常大晶粒的根本原因。     

双合金混粉法添加镝对烧结Nd-Fe-B磁体的磁性能及微观结构的影响

研究双合金混粉法添加Dy对烧结Nd-Fe-B磁体的磁性能和微观结构的影响。结果表明:添加少量Dy能够同时提高磁体的矫顽力和最大磁能积;当Dy含量为1.0%时,磁体的最大磁能积达到最大值。烧结温度从1065℃增加到1085℃时,烧结Nd-Fe-B磁体的磁性能没有急剧恶化,磁体的烧结温度范围较宽。磁体在烧结过程中高Dy含量合金主相晶粒中的Dy元素扩散到不含Dy元素的合金主相晶粒中,造成最后所得磁体中存在不同Dy含量的主相晶粒;磁体不同主相晶粒中Dy含量差别较大,随着添加Dy含量的增加,磁体中不同主相晶粒平均含Dy量也逐渐增加。     

ZrB2对烧结Sm(Co0.717Fe0.15Cu0.10Zr0.033)7.2合金微观组织和性能的影响

通过在制粉阶段添加微量ZrB2粉末的方法,制备了Sm（Co0.717Cu0.1Fe0.15Zr0.033）7.2（ZrB2）x（x=0～0.025）烧结磁体.采用扫描电子显微镜、能谱分析和X射线衍射分析磁体的微观组织及相组成,利用NIM-2000型直流磁性测量仪测试磁体的磁性能,研究了添加ZrB2对永磁体组织性能的影响.结果表明： 适量添加ZrB2可以降低磁体的烧结温度; ZrB2发生部分分解会影响合金组织与结构,使合金室温磁性能和高温稳定性都有不同程度的提高; 没有分解的ZrB2颗粒以质点的形式存在,使磁体的断裂韧性值大幅度增加.     

双主相(Ce,R)-Fe-B烧结磁体的核壳结构

研究了铈基双主相烧结磁体的磁性能和微结构,重点对双主相磁体不均匀的元素分布及微结构特征进行观察分析。研究表明:在双主相磁体的烧结及热处理过程中,稀土元素在两种主相晶粒之间发生了互扩散,形成了两种典型的核-壳结构晶粒,它们具有成分接近的"壳"和成分明显不同的"核"。双主相磁体中的这种核-壳结构,类似于"晶界扩散"Nd-Fe-B磁体的核-壳结构。在此基础上,对双主相(Ce, R)-Fe-B磁体的矫顽力增强机制和反磁化行为进行了解释。     

双合金结合速凝工艺制备烧结NdFeB研究

采用速凝工艺制备了主相合金铸片,由其微观形貌分析可见,富Nd相呈薄层状均匀分布在主相晶界处。XRD分析表明铸带形成了明显的取向织构。使用普通熔炼方法熔炼几种不同成分的辅相合金。将主相合金与辅相合金配比,运用双合金法工艺制备出烧结NdFeB磁体。研究表明Pr替代Nd有利于提高磁体的剩磁。     

纳米钨合金块体材料的制备

高比重钨合金由于具有一系列优异的物理力学性能, 因此在航空航天、国防军工和民用中有着广泛的应用前景.采用纳米技术制备高比重钨合金块体材料有望进一步提高其性能, 促使其应用.本文分析了纳米钨合金在粉末制备和成型烧结中存在的问题, 并针对纳米钨合金粉末成型和烧结过程中晶粒长大问题以及块体材料中存在大量微孔问题, 介绍了数种可行性控制方法.     

双主相合金法添加镝对烧结Nd-Fe-B磁性能及微观结构的影响

提出了一种制备高矫顽力、高剩磁烧结Nd-Fe-B磁体的方法——双主相合金法,利用这种方法制备的磁体中同时存在Nd2Fe14B和(Nd,Dy)2Fe14B两种主相。能谱分析表明:这种方法可以调控主相成分,制备的磁体易于实现全致密化并且剩磁较高,综合磁性能较好。利用双主相合金法制备磁体的剩磁和磁能积优于双合金法。     

HDD工艺对NdFeB粘结磁体磁性能的影响

叙述了NdFeB合金成分、均匀化处理和HDD处理脱氢过程对磁性粉末及粘结磁体磁性能的影响。实验表明,HDD法制备的NdFeB磁性粉末及粘结磁体具有较好的温度稳定性和时间稳定性。     

回火温度对晶界添加烧结钕铁硼磁体结构演变及磁性提升机理的影响EI北大核心CSCD

采用晶界添加的方法制备了添加Tb65Cu35的烧结Nd-Fe-B磁体,研究了回火温度对晶界添加磁体微结构演变规律及磁性能的影响,并对其性能提升机制进行了分析。结果表明：经910℃一级回火2 h,460℃二级回火2 h的磁体性能最佳,获得了Br=14.14 k Gs,Hcj=12.31 k Oe,(BH)max=47.89 MGOe的磁性能,回火后的磁体的矫顽力从10.21 k Oe提升到12.31 k Oe,增加了约20%,剩磁基本保持不变。矫顽力的提升主要归因于硬磁的(Nd,Tb)-Fe-B壳层以及连续晶界层的形成。通过一阶反转曲线(FORC)对不同回火条件下样品的磁化反转过程进行了分析,可以发现最差回火态晶界添加磁体中有两个峰,然而,最佳回火态的晶界添加磁体只有一个明显的峰,表现出明显的相互作用的单畴晶粒特性,表明最佳回火态磁体内核壳之间具有强的耦合相互作用。     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Effect of the Method of Modification of Zeolite X on Selectivity of Catalytic Methylation of Toluene

Theoretical and Experimental Chemistry - The effect of the method of modification of catalysts based on zeolite X by cesium and magnesium cations (ion exchange and impregnation) on the selectivity...     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

Synthesis of tetrabenzoporphins of the basis of isoindoline

Chemistry of Heterocyclic Compounds -