低維功能固體的電聲結(jié)構(gòu)調(diào)制及其機(jī)敏特性研究
本文選題:電聲結(jié)構(gòu)調(diào)制 + 低維固體; 參考:《中國(guó)科學(xué)技術(shù)大學(xué)》2015年博士論文
【摘要】:作為一類(lèi)重要的功能材料,無(wú)機(jī)機(jī)敏材料能夠感知和響應(yīng)光、熱、磁、電等外部環(huán)境的變化,是實(shí)現(xiàn)材料智能行為的關(guān)鍵環(huán)節(jié)。更重要的是,伴隨著機(jī)敏性質(zhì)而出現(xiàn)的能量形式轉(zhuǎn)換和物理行為改變?cè)谀茉创鎯?chǔ)和利用、信息寫(xiě)入和讀取等領(lǐng)域有著巨大的應(yīng)用價(jià)值。設(shè)計(jì)高性能的固體機(jī)敏材料以提升感知能力、響應(yīng)速率和能量利用率一直是人們追逐的目標(biāo)。隨著納米科技的迅猛發(fā)展,固體的低維化處理為提高機(jī)敏性能帶來(lái)了新的希望。低維固體由尺寸降低引起的量子限域效應(yīng)、表面效應(yīng)等使其具有與宏觀塊體材料截然不同的電子、聲子結(jié)構(gòu),因而表現(xiàn)出特殊的電學(xué)、磁學(xué)、光學(xué)等本征物理性質(zhì),為優(yōu)化固體材料機(jī)敏性能、發(fā)展新型機(jī)敏材料提供了一個(gè)理想的材料平臺(tái)。 本論文通過(guò)分析誘導(dǎo)特定機(jī)敏性能產(chǎn)生所需的特殊電子、聲子結(jié)構(gòu),在實(shí)現(xiàn)電聲結(jié)構(gòu)的功能導(dǎo)向性調(diào)制基礎(chǔ)上,最終獲得低維固體機(jī)敏性質(zhì)的優(yōu)化和新型機(jī)敏性能的開(kāi)發(fā)。作者利用元素?fù)诫s,氫修飾、維度調(diào)控、缺陷工程等多種化學(xué)處理手段,對(duì)低維功能固體的電子、聲子結(jié)構(gòu)進(jìn)行了有效且可控的調(diào)制,提升了相關(guān)材料對(duì)磁、熱、光等外場(chǎng)敏感的機(jī)敏性能。本論文對(duì)低維功能固體電聲結(jié)構(gòu)的調(diào)制策略為設(shè)計(jì)高性能機(jī)敏材料帶來(lái)了新的思路。論文的主要內(nèi)容包括以下幾個(gè)方面: 1.作者通過(guò)溶液化學(xué)方法首次成功的制備了新物相銳鈦礦結(jié)構(gòu)VTiO4零維納米晶,并在該簡(jiǎn)單氧化物中實(shí)現(xiàn)了大的室溫磁-介電響應(yīng)。利用V4+離子和Ti4+離子原子半徑的相似性,V4+離子被大量引入銳鈦礦Ti02結(jié)構(gòu)中,形成了V/Ti原子比高達(dá)1/1的新型離子型固溶體,成功的將銳鈦礦結(jié)構(gòu)引入釩氧化合物體系中。在該結(jié)構(gòu)中,具有3d1單電子的V4+離子的大量引入為其帶來(lái)了磁有序和極化有序的協(xié)同效應(yīng)。一方面,V4+-O2--V4+之間的超交換作用誘導(dǎo)產(chǎn)生了室溫鐵磁性。另一方面,由V4+離子帶來(lái)的姜-泰勒效應(yīng)使得整體晶格發(fā)生畸變,這種晶體結(jié)構(gòu)對(duì)稱(chēng)性的降低增強(qiáng)了離子極化能力,進(jìn)而帶來(lái)了巨介電效應(yīng)。上述鐵磁和畸變晶格中的聲子結(jié)構(gòu)共存進(jìn)一步誘發(fā)自旋-聲子相互作用,使得材料表現(xiàn)出大的室溫磁介電響應(yīng)(△ε/ε0=7.2%)。這種向簡(jiǎn)單氧化物中大量引入姜-泰勒磁性離子的方法為設(shè)計(jì)和探索新的磁介電機(jī)敏材料提供了新的思路。 2.利用氫修飾調(diào)控了一維釩-釩原子鏈中電子-電子關(guān)聯(lián)效應(yīng),獲得了電子聲子結(jié)構(gòu)的去耦合調(diào)制,優(yōu)化了單斜相VO2(M)材料的熱電性能。通過(guò)氫離子對(duì)金屬絕緣體轉(zhuǎn)變材料V02(M)的修飾作用,成功的向結(jié)構(gòu)中注入電子,.強(qiáng)化了一維釩-釩原子鏈中的電子關(guān)聯(lián)效應(yīng),將原本僅在高溫存在的金紅石V02(R)穩(wěn)定到了室溫。與此同時(shí),隨著氫離子濃度的增加,獲得了載流子濃度呈梯度變化的系列樣品:金屬態(tài)氫化V02(R)、過(guò)渡態(tài)VO2(M-R)以及半導(dǎo)體態(tài)V02(M)。最終獲得的金屬態(tài)氫化V02(R)的室溫載流子濃度是半導(dǎo)體態(tài)V02(M)的1000倍。另一方面,因?yàn)闅渚哂凶钚〉碾x子半徑,因此氫修飾能夠維持釩氧骨架結(jié)構(gòu),保持聲子結(jié)構(gòu)沒(méi)有明顯變化。這種通過(guò)原位氫修飾的方法,在材料結(jié)構(gòu)變化不大的基礎(chǔ)上,完成了對(duì)電子-電子關(guān)聯(lián)作用的有效調(diào)制,實(shí)現(xiàn)了電聲去耦合調(diào)控,獲得了能夠在包含室溫的寬范圍溫區(qū)內(nèi)工作的熱電性能。值得注意的是,能夠在室溫或者低于室溫的溫區(qū)內(nèi)獲得高ZT優(yōu)值的簡(jiǎn)單氧化物結(jié)構(gòu)是很少的。該實(shí)驗(yàn)表明對(duì)于電子-電子關(guān)聯(lián)作用的調(diào)控將是實(shí)現(xiàn)電聲去耦合調(diào)制,提升熱電性能的強(qiáng)有力手段。 3.作者利用量子限域效應(yīng)首次在二維ZrNCl納米片材料中實(shí)現(xiàn)了高效的紫外光熱性能。通過(guò)化學(xué)插鋰和液相超聲剝離的結(jié)合,第一次制備出了具有3~4個(gè)ZrNCl結(jié)構(gòu)單層的二維超薄納米片。在該二維結(jié)構(gòu)體系中,原子層限域作用帶來(lái)電子弛豫能量的增加;同時(shí),由四原子組成的[Cl-Zr-N-Cl]單層的獨(dú)特結(jié)構(gòu)產(chǎn)生了更強(qiáng)烈的表面化學(xué)鍵振動(dòng)。上述協(xié)同效應(yīng),增強(qiáng)了光生電子與聲子的相互作用,進(jìn)而產(chǎn)生了高效的紫外光能到熱能的轉(zhuǎn)換。在200mW/cm2的紫外光照下,二維ZrNCl納米片可產(chǎn)生5.25W/g的熱流,是塊材樣品的24倍,更是其他寬帶隙半導(dǎo)體材料的幾十倍,其光熱轉(zhuǎn)換效率可達(dá)到72%,是目前半導(dǎo)體材料紫外光熱轉(zhuǎn)換性能的最優(yōu)值。該工作不僅實(shí)現(xiàn)了一種基于紫外光的新的能量轉(zhuǎn)換形式,同時(shí)利用限域效應(yīng)增強(qiáng)電聲耦合的概念也為發(fā)展新的光熱機(jī)敏材料提供了有益的指導(dǎo)。 4.作者通過(guò)向二維ZrNCl納米片中引入缺陷的方法,提高了材料的電導(dǎo)率并縮減了能帶隙,獲得了提升的光電催化分解水性能,首次將金屬氮鹵化合物體系引入光電催化反應(yīng)。在可見(jiàn)光照射下(λ≥400nm),含有少量氯缺陷的ZrNCl納米片在1.6V (vs RHE)時(shí)的光電流達(dá)到3.3mA/cm2,是不含缺陷ZrNCl納米片光電流值的7.3倍,含缺陷ZrNCl塊材的22倍。實(shí)驗(yàn)表明,引入氯缺陷后,ZrNCl納米片的電導(dǎo)率明顯提高,有利于光電催化過(guò)程中的電荷轉(zhuǎn)移;同時(shí),含缺陷的ZrNCl納米片光吸收邊進(jìn)入可見(jiàn)光區(qū),提高了可見(jiàn)光的利用率。此外,相比于塊體材料而言,其二維的形貌提供了更多與電解液的接觸面積,且與導(dǎo)電基底的接觸更為緊密。這種利用缺陷工程對(duì)二維納米材料電子結(jié)構(gòu)調(diào)制以實(shí)現(xiàn)光電催化過(guò)程優(yōu)化的策略對(duì)于優(yōu)化和發(fā)展新型光電反應(yīng)催化劑具有較高的借鑒意義。
[Abstract]:As an important kind of functional material, the inorganic sensitive materials can perceive and respond to the changes in the external environment such as light, heat, magnetism and electricity. It is the key link to realize the intelligent behavior of materials. More importantly, the energy form conversion and physical behavior, which are accompanied by the sensitive nature, are changed to energy storage and utilization, information writing and reading. With the rapid development of nanotechnology, the low dimension of solids has brought new hope to improve the sensitive performance with the rapid development of nanotechnology. The quantum confinement effect of low dimensional solids is caused by size reduction. The surface effect, such as the surface effect, makes it have the electronic, phonon structure different from the macroscopic bulk material, thus showing special physical, magnetic and optical properties, which provides an ideal material platform for the optimization of the sensitive properties of solid materials and the development of new type of sensitive materials.
In this paper, the special electrons and phonon structures required to induce specific sensitivity are analyzed. On the basis of realizing the function oriented modulation of the electroacoustic structure, the optimization of the low dimensional solid properties and the development of new sensitive properties are finally obtained. The author uses many chemical treatments, such as element doping, hydrogen modification, dimension regulation and defect engineering. By means of effective and controllable modulation of the electrons and phonon structures of low dimensional functional solids, the sensitive properties of the related materials for magnetic, thermal and optical fields are enhanced. The modulation strategy for low dimensional functional solid acoustic structures in this paper has brought new ideas for the design of high performance and sensitive materials. The main contents of this paper include the following Aspect:
1. the author successfully prepared the anatase null nanocrystalline nanocrystalline of the new phase anatase structure for the first time by the solution chemical method, and achieved a large magnetic dielectric response at room temperature in the simple oxide. Using the similarity of the V4+ ions and the atomic radius of the Ti4+ ions, the V4+ ions were introduced into the Ti02 structure of the anatase to form a V/Ti atomic ratio of up to 1/1. The new type of ionic solid solution has successfully introduced anatase into the system of vanadium oxide. In this structure, a large number of V4+ ions with 3D1 single electrons are introduced into the synergistic effect of magnetic order and polarization order. On the one hand, the ultraexchange between V4+-O2--V4+ induces room temperature ferromagnetism. On the other hand, V4+ The Zingiber Taylor effect caused by the ion caused the distortion of the whole lattice. The reduction of the symmetry of the crystal structure enhanced the ion polarization and the giant dielectric effect. The coexistence of the phonon structures in the ferromagnetic and distorted lattice further induced the spin phonon interaction, which made the material exhibit a large magnetic dielectric response at room temperature. The method of introducing a large amount of ginger Taylor magnetic ions into simple oxides provides a new idea for the design and exploration of new magnetic dielectric motor sensitive materials.
2. the electron electron correlation effect in one dimensional vanadium vanadium atom chain is regulated by hydrogen modification, and the decoupling modulation of the electron phonon structure is obtained. The thermoelectric properties of the monoclinic VO2 (M) material are optimized. By modifying the V02 (M) of the metal insulator transition material by hydrogen ion, the electrons are injected into the structure of the power, and the one dimension vanadium vanadium atom is strengthened. The electron correlation effect in the chain has stabilized the rutile V02 (R), originally only at high temperature, to the room temperature. At the same time, with the increase of hydrogen ion concentration, a series of samples with the gradient change of the carrier concentration are obtained: the metal state hydrogenated V02 (R), the transition state VO2 (M-R) and the semiconductor state V02 (M). The final obtained hydrogenated V02 (R) chamber The concentration of the temperature carrier is 1000 times that of the semiconductor state V02 (M). On the other hand, because hydrogen has the smallest ionic radius, the hydrogen modification can maintain the vanadium oxygen skeleton structure and keep the phonon structure without obvious change. By the method of in situ hydrogen modification, the electron electron correlation function is completed on the basis of the small change of material structure. The effective modulation has achieved the electroacoustic decoupling control, and the thermoelectric properties that can work in a wide range temperature range containing room temperature are obtained. It is noteworthy that the simple oxide structure of high ZT value can be obtained at room temperature or below the temperature zone at room temperature. It is a powerful means to realize electro acoustic decoupling modulation and enhance thermoelectric performance.
3. the effective UV photothermal properties of the two dimensional ZrNCl nanomaterials were achieved for the first time by the quantum confinement effect. Through the combination of chemical intercalation and liquid phase ultrasonic dissection, the first two dimensional ultrathin nanoscale films with 3~4 monolayers were prepared. In the two-dimensional structure, the confinement of the atomic layer brought the electron relaxation. At the same time, the unique structure of the [Cl-Zr-N-Cl] monolayer composed of four atoms produces a stronger surface chemical bond vibration. The above synergy enhances the interaction between the photoelectron and the phonon, and then produces the efficient conversion of the ultraviolet energy to the heat energy. Under the ultraviolet light of 200mW/cm2, the two-dimensional ZrNCl nanoscale is available. The heat flux that produces 5.25W/g is 24 times that of the bulk material, a few times the other broadband gap semiconductor materials, and its photothermal conversion efficiency can reach 72%. It is the best value for the ultraviolet light and heat conversion performance of semiconductor materials. This work not only realizes a new form of energy conversion based on ultraviolet light, but also enhances electricity by using the limit effect. The concept of acoustic coupling also provides useful guidance for the development of new photo thermal smart materials.
4. by introducing defects into two-dimensional ZrNCl nanoscale, the author improved the conductivity of the material and reduced the band gap. The performance of the enhanced photocatalytic decomposition water was obtained. For the first time, the metal nitrogen halide compound system was introduced to the photoelectrochemical reaction. The ZrNCl nanoscale containing a small amount of chlorine defects under the visible light ([lambda] 400nm) and a small amount of chlorine defects were found. The photoelectric current at vs RHE is up to 3.3mA/cm2, which is 7.3 times of the optoelectronic flow value of the non defective ZrNCl nanometers and 22 times as much as the defective ZrNCl block. The experiment shows that the conductivity of the ZrNCl nanoscale is obviously improved after the introduction of the chlorine defect, and it is beneficial to the charge transfer in the process of photoelectric catalysis; meanwhile, the optical absorption edge of the defective ZrNCl nanoscale is visible to the visible light. In addition, the two-dimensional morphology provides more contact area with the electrolyte than the bulk material, and more closely contact with the conductive substrate. The strategy of using the defect engineering to modulate the electronic structure of the two-dimensional nanomaterial for the optimization of the photoelectrocatalysis process is optimized and developed. The new photoelectric reaction catalyst has a high reference value.
【學(xué)位授予單位】:中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】:博士
【學(xué)位授予年份】:2015
【分類(lèi)號(hào)】:TB34;O641
【共引文獻(xiàn)】
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