本文關(guān)鍵詞：錳硼化合物的高溫高壓合成及其物性研究　出處：《吉林大學(xué)》2017年博士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： 錳硼化合物 硬度機(jī)制 高溫高壓 硬質(zhì)多功能 維氏硬度

【摘要】：過(guò)渡金屬具有較高的價(jià)電子密度,具有很強(qiáng)的抵抗體積形變能力,但是抗剪切能力差,雖然有較高的體彈性模量,但是硬度不高;輕元素硼、碳、氮可以形成方向性極強(qiáng)的共價(jià)鍵,形成的化合物具有很強(qiáng)的抵抗剪切應(yīng)力的能力。過(guò)渡金屬輕元素化合物,在過(guò)渡金屬中引入強(qiáng)共價(jià)鍵網(wǎng)絡(luò),使之同時(shí)具有兩者的特點(diǎn),可以形成了一種類(lèi)似于“鋼筋混凝土”的高強(qiáng)度晶體結(jié)構(gòu);另外,由于過(guò)渡金屬豐富的價(jià)電子,可以為形成的化合物帶來(lái)豐富的物理化學(xué)性質(zhì),因而該體系是一種潛在的高硬度多功能材料。磁性材料在現(xiàn)代機(jī)電系統(tǒng)、磁電子學(xué)等方面有重要應(yīng)用;硬質(zhì)材料可以往往具有較強(qiáng)的化學(xué)鍵、化學(xué)性質(zhì)穩(wěn)定、抗氧化性強(qiáng)等特點(diǎn),同時(shí)具有耐磨、抗形變等優(yōu)點(diǎn);為尋找滿足極端條件應(yīng)用的高硬度磁性材料有著重大的物理學(xué)和材料學(xué)意義。本文針對(duì)潛在的高硬度磁性錳硼化合物進(jìn)行了研究,利用高溫高壓的方法對(duì)錳硼體系進(jìn)行了系統(tǒng)的合成,并利用實(shí)驗(yàn)與理論模擬相結(jié)合的方法對(duì)錳硼化合物的結(jié)構(gòu)、力學(xué)性質(zhì)、磁學(xué)性質(zhì)、成鍵特性等進(jìn)行深入的探究,得到了一些有價(jià)值的成果:一、利用高溫高壓這種特殊方法對(duì)錳硼體系進(jìn)行了實(shí)驗(yàn)合成,得到了錳硼體系在高壓下的相圖。合成出了Mn2B(SG:I4/mcm)、Cr B結(jié)構(gòu)的Mn B(SG:I41/amd)、Fe B結(jié)構(gòu)的Mn B(SG:Pnma)、Ta3B4結(jié)構(gòu)的Mn3B4(SG:Immm)、Al B2結(jié)構(gòu)的Mn B2(SG:P6/mmm)以及Mn B4(SG:P21/c)。發(fā)現(xiàn)高溫高壓下錳硼化合物的合成有以下特點(diǎn):(1)合成硼濃度高于50%的錳硼化合物均需要硼單質(zhì)過(guò)量;(2)Mn B4的在高壓下的合成區(qū)間變窄(3)高壓條件下得到了一種Cr B結(jié)構(gòu)的Mn B新結(jié)構(gòu);以上結(jié)果說(shuō)明高溫高壓對(duì)于豐富物質(zhì)的相圖是一種十分有效的手段。二、在Mn B晶體當(dāng)中,硼原子在錳金屬晶格當(dāng)中形成了一維無(wú)限長(zhǎng)“之”字狀硼鏈,使得錳原子之間的距離得到了一定的擴(kuò)大,實(shí)現(xiàn)了從錳金屬的反鐵磁性磁序向鐵磁性磁序的轉(zhuǎn)變。磁學(xué)參數(shù)測(cè)試表明Mn B具有較高的居里轉(zhuǎn)變溫度、較低的矯頑力以及較高的磁飽和強(qiáng)度,表明Mn B是一種優(yōu)異的高溫鐵磁材料。此外,由于強(qiáng)共價(jià)鍵“之”字狀硼鏈的引入,Mn B的維氏硬度值達(dá)到了16 GPa左右,遠(yuǎn)高于傳統(tǒng)鐵磁性材料的硬度值�！爸弊譅钆疰湹囊胄纬闪艘环N高硬度的鐵磁性材料,使得鐵磁性材料更加接近更強(qiáng)、更輕、更節(jié)能的目標(biāo),為鐵磁性材料在極端條件下的應(yīng)用打下了堅(jiān)實(shí)的基礎(chǔ)。三、當(dāng)錳硼化學(xué)配比達(dá)到1:2時(shí),硼原子形成了石墨烯狀的六元環(huán)空間骨架,錳原子層與硼原子層交替排列,形成了一種BICs類(lèi)型的晶體結(jié)構(gòu)。由于石墨烯狀硼層空的π價(jià)帶,實(shí)驗(yàn)上始終未能合成出石墨烯狀的硼烯。X射線光電子能譜與第一性原理計(jì)算結(jié)果均表明:在BICs晶體Mn B2當(dāng)中,由于錳原子向硼原子層中轉(zhuǎn)移了一定量的電子,六元環(huán)狀的硼層空的π價(jià)帶得到了填充,實(shí)現(xiàn)了石墨烯狀硼層的在Mn B2晶體中穩(wěn)定存在。由于石墨烯狀硼層的填充,錳原子層之間的距離得到了擴(kuò)大,錳原子之間的交換作用發(fā)生了改變,實(shí)現(xiàn)了反鐵磁性錳金屬向弱鐵磁性Mn B2的轉(zhuǎn)變;同時(shí),由于石墨烯狀硼層內(nèi)部存在較強(qiáng)的共價(jià)鍵,六元環(huán)狀硼層具有很強(qiáng)的力學(xué)性質(zhì),導(dǎo)致Mn B2在c軸方向具有極高的硬度值。這種方向性極高的硬度與鐵磁性性質(zhì)可能將在涂層防護(hù)、極端條件下的磁器件等領(lǐng)域得到一定的應(yīng)用。四、隨著硼元素濃度的增加,硼濃度驅(qū)動(dòng)硼原子亞結(jié)構(gòu)分別經(jīng)歷了Mn2B的孤立硼原子、Fe B結(jié)構(gòu)的Mn B和Cr B結(jié)構(gòu)的Mn B中的“之”字鏈狀、Mn3B4的聚合“之”字鏈、Mn B2的石墨烯狀硼層、Mn B4的三維空間籠狀結(jié)構(gòu)。隨著硼原子亞結(jié)構(gòu)的演變,錳硼化合物的硬度經(jīng)歷了先增加、后減小、再增加的過(guò)程。說(shuō)明硼含量與硬度并非呈線性關(guān)系;高的電子密度、三維空間結(jié)構(gòu)對(duì)硬度的提升有一定的幫助,但是一定的硼濃度將會(huì)產(chǎn)生層狀結(jié)構(gòu)硼化物,對(duì)高硬度將產(chǎn)生致命的影響。隨著硼濃度的不斷升高,錳硼化合物的磁性依次經(jīng)歷了順磁性、鐵磁性、反鐵磁性、順磁性的演變過(guò)程,這與硼原子亞結(jié)構(gòu)進(jìn)入錳金屬晶格當(dāng)中,不同程度地?cái)U(kuò)大了錳原子之間的距離,進(jìn)而影響到了錳原子之間的交換作用有關(guān)。根據(jù)硼濃度對(duì)錳硼化合物硬度和磁性的影響可知:硬質(zhì)磁性功能材料的設(shè)計(jì)需要同時(shí)兼顧材料的硬度設(shè)計(jì)理論與磁性理論,選擇合適的過(guò)渡金屬元素和輕元素種類(lèi)與化學(xué)配比,達(dá)到晶體同時(shí)兼具較高硬度與優(yōu)異磁性的目的。綜上,通過(guò)高溫高壓的方法對(duì)Mn-B體系進(jìn)行系統(tǒng)的合成,得到了一系列不同配比的錳硼化合物,繪制了Mn-B體系在高壓下的合成相圖,為錳硼化合物高溫高壓合成提供了精確的合成相圖。合成出了一批具有較良好磁學(xué)性能且硬度較高的物質(zhì),高溫鐵磁性硬質(zhì)多功能材料Cr B結(jié)構(gòu)的Mn B和Fe B結(jié)構(gòu)的Mn B、方向性高硬度的磁性材料Mn B2以及出現(xiàn)Peierls相變的Mn B4材料。發(fā)現(xiàn)通過(guò)高溫高壓這種特殊手段對(duì)錳硼體系的電子密度、電子結(jié)構(gòu)、成鍵特性以及晶體結(jié)構(gòu)的調(diào)節(jié)的規(guī)律,并能通過(guò)溫度、壓力及前驅(qū)物組份等條件控制不同種類(lèi)的硼原子空間骨架。以硼濃度為變量研究了錳硼化合物的硬度、磁性的變化規(guī)律,發(fā)現(xiàn)了硬度與硼濃度之間并非線性關(guān)系,硼濃度通過(guò)改變錳原子之間的距離影響了錳硼化合物的磁性。該工作當(dāng)中得到的硼濃度對(duì)硬度和磁性的作用規(guī)律為今后尋找鐵磁性高硬度材料指明了方向。
[Abstract]:The valence electron density of transition metal has high, has a strong resistance volume deformation ability, but the anti shearing ability is poor, while the elastic modulus is higher, but the hardness is not high; the light element boron, carbon, nitrogen can form a covalent bond with strong direction, the formation of compounds with strong ability to resist shear stress. Transitionmetal compounds, the strong covalent bond network in transition metal, which has the characteristics of both, can form a high strength crystal structure similar to the "reinforced concrete"; in addition, because the transition metal valence electron rich, can bring extensive physical and chemical properties for the formation of compounds, so the system is a potential high hardness multifunctional material. Magnetic materials in the modern electrical system, have important applications in magnetic electronics etc.; hard materials can have a strong chemical bond, The characteristics of chemical stability, oxidation resistance is strong, also has the advantages of deformation resistance and wear resistance, high hardness; for meet the extreme conditions of magnetic material has a significant application of physics and materials science. Aiming at the potential of high hardness magnetic manganese boron compounds were studied, using the method of high temperature and pressure of the system synthesis of manganese boron system, magnetic properties, and method of using a combination of experimental and theoretical simulation of manganese and boron compounds, mechanical properties, bonding properties in-depth inquiry, obtained some valuable achievements: first, the special method of using high pressure and high temperature experiments were carried out on the synthesis of manganese and boron in the system. The phase diagram of manganese boron system under high pressure. The synthesis of Mn2B (SG:I4/mcm), Cr B Mn (SG:I41/amd) B structure, Fe structure of B Mn B (SG:Pnma), Ta3B4 Mn3B4 (SG: Immm) structure, Al (SG:P6/ B2 Mn B2 structure MMM) and Mn B4 (SG:P21/c) has the following characteristics. The synthesis of manganese boron compounds under high temperature and high pressure: (1) the synthesis of boron concentration is higher than 50% of the manganese boron compounds to elemental boron excess; (2) under high pressure synthesis of narrow interval Mn B4 (3) high pressure can be obtained under the conditions of new Mn B the structure of a Cr B structure; the above results showed that high temperature and high pressure is a very effective method for the phase diagram of material abundance. Two in Mn, B crystal, boron atoms to form an infinite one dimensional zigzag chain in boron manganese metal lattice, the manganese atomic distances must be to expand, to achieve the transition from antiferromagnetic magnetic order to manganese metal ferromagnetic order. Magnetic parameters test showed that the Curie temperature Mn B with high and low coercivity and high saturation magnetization, showed that the Mn B is a kind of high temperature ferromagnetic material excellent. In addition, because The introduction of a strong covalent bond of zigzag boron chain, Vivtorinox Mn B hardness value reached about 16 GPa, much higher than the traditional iron magnetic material hardness. "Introduction" shaped boron chain formed a ferromagnetic material with high hardness, the ferromagnetic material is more close to the more stronger. Light, more energy-efficient, a solid foundation for the application of ferromagnetic materials under extreme conditions. In three, when the ratio of 1:2 chemical manganese and boron, boron atoms form six membered ring space framework of graphene like manganese and boron atoms, atomic layer layer arranged alternately, forming a crystal structure type of BICs. As the valence band graphene like boron layer empty, experiment has been unable to synthesize graphene like boron by.X ray photoelectron spectroscopy results show that calculated with the first principle: in BICs crystal Mn B2, due to boron manganese atom atomic layer in a quantitative power transfer Son, the six membered ring of boron vacancies are filled valence band PI, the graphene like layer of boron in Mn B2 crystal is stable. Due to the filling of graphene like layers of boron, manganese atomic layer between the distance has been expanded, changed the exchange interaction between manganese atoms, to achieve the transformation anti ferromagnetic manganese metal to the weak ferromagnetic Mn B2; at the same time, due to the presence of strong covalent bonds of graphene like boron layer, six membered boron layer has strong mechanical properties, resulting in Mn B2 has a very high hardness value in the direction of C axis. The direction of magnetic properties of high hardness and may in the coating protection, can be widely applied in areas such as the magnetic device under extreme conditions. Four, with the increase of boron concentration, concentration of boron boron atom driven sub structure respectively through isolated boron atoms Mn2B, Fe B B and Cr B structure of the Mn structure of the Mn B " Chain polymerization, zigzag chains Mn3B4, graphene like boron layer of Mn B2, Mn B4 3D cage structure. With the evolution of the boron atom substructure, manganese and boron compounds through the hardness first increased, then decreased, and then increased. The process shows that there is a linear relationship between boron content and hardness is not; high electron density, will help enhance the three-dimensional structure of hardness, but will produce certain concentration of boron layered boride, will be fatal to high hardness. With the increasing concentration of boron, magnetic manganese boron compounds experienced a paramagnetic, ferromagnetic, antiferromagnetic, CIS the evolution of magnetic, and the boron atom substructure into manganese metal lattice, different degrees of expansion of manganese atom distance between, and thus affect the exchange interaction between manganese atoms. According to the boron concentration of manganese boron compounds and magnetic hardness The influence of design of hard magnetic functional materials need to consider the hardness of the material design theory and the theory of magnetism, choose suitable transition metal elements and light elements and chemical composition, crystal to both high hardness and excellent magnetic properties. Therefore, systematic synthesis of Mn-B system by means of high temperature and high pressure. A series of different ratio of manganese and boron compounds, synthesis of phase diagrams of Mn-B system under high pressure, provides accurate phase diagrams for the synthesis of manganese boron compounds in high temperature and high pressure. The synthesis of a number of relatively good magnetic properties and high hardness material, high temperature hard ferromagnetic multifunctional material Cr B structure Mn B and Fe B structure of Mn B, Mn B2 magnetic material direction of high hardness and Mn B4 Peierls. The phase change material of manganese boron body with high temperature and pressure of this special means Department of electron density, electron structure, bonding properties and crystal structure of the regulation of law, and by the temperature, the boron atom space framework of different kinds of control pressure and precursor componentthese conditions. Variables of Mn boron compounds with boron concentration for hardness, magnetic variation, hardness and found the non-linear relationship between the concentration of boron, boron concentration of magnetic manganese boron compounds by changing the distance between the manganese atoms. The role of boron concentration in hardness and magnetic properties is the ferromagnetic materials with high hardness and pointed out a direction.

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TQ163

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