低维功能固体的电声结构调制及其机敏特性研究

发布时间：2018-06-23 10:02

本文选题：电声结构调制 + 低维固体　；参考：《中国科学技术大学》2015年博士论文

【摘要】：作为一类重要的功能材料,无机机敏材料能够感知和响应光、热、磁、电等外部环境的变化,是实现材料智能行为的关键环节。更重要的是,伴随着机敏性质而出现的能量形式转换和物理行为改变在能源存储和利用、信息写入和读取等领域有着巨大的应用价值。设计高性能的固体机敏材料以提升感知能力、响应速率和能量利用率一直是人们追逐的目标。随着纳米科技的迅猛发展,固体的低维化处理为提高机敏性能带来了新的希望。低维固体由尺寸降低引起的量子限域效应、表面效应等使其具有与宏观块体材料截然不同的电子、声子结构,因而表现出特殊的电学、磁学、光学等本征物理性质,为优化固体材料机敏性能、发展新型机敏材料提供了一个理想的材料平台。本论文通过分析诱导特定机敏性能产生所需的特殊电子、声子结构,在实现电声结构的功能导向性调制基础上,最终获得低维固体机敏性质的优化和新型机敏性能的开发。作者利用元素掺杂,氢修饰、维度调控、缺陷工程等多种化学处理手段,对低维功能固体的电子、声子结构进行了有效且可控的调制,提升了相关材料对磁、热、光等外场敏感的机敏性能。本论文对低维功能固体电声结构的调制策略为设计高性能机敏材料带来了新的思路。论文的主要内容包括以下几个方面： 1.作者通过溶液化学方法首次成功的制备了新物相锐钛矿结构VTiO4零维纳米晶,并在该简单氧化物中实现了大的室温磁-介电响应。利用V4+离子和Ti4+离子原子半径的相似性,V4+离子被大量引入锐钛矿Ti02结构中,形成了V/Ti原子比高达1/1的新型离子型固溶体,成功的将锐钛矿结构引入钒氧化合物体系中。在该结构中,具有3d1单电子的V4+离子的大量引入为其带来了磁有序和极化有序的协同效应。一方面,V4+-O2--V4+之间的超交换作用诱导产生了室温铁磁性。另一方面,由V4+离子带来的姜-泰勒效应使得整体晶格发生畸变,这种晶体结构对称性的降低增强了离子极化能力,进而带来了巨介电效应。上述铁磁和畸变晶格中的声子结构共存进一步诱发自旋-声子相互作用,使得材料表现出大的室温磁介电响应(△ε/ε0=7.2%)。这种向简单氧化物中大量引入姜-泰勒磁性离子的方法为设计和探索新的磁介电机敏材料提供了新的思路。 2.利用氢修饰调控了一维钒-钒原子链中电子-电子关联效应,获得了电子声子结构的去耦合调制,优化了单斜相VO2(M)材料的热电性能。通过氢离子对金属绝缘体转变材料V02(M)的修饰作用,成功的向结构中注入电子,.强化了一维钒-钒原子链中的电子关联效应,将原本仅在高温存在的金红石V02(R)稳定到了室温。与此同时,随着氢离子浓度的增加,获得了载流子浓度呈梯度变化的系列样品：金属态氢化V02(R)、过渡态VO2(M-R)以及半导体态V02(M)。最终获得的金属态氢化V02(R)的室温载流子浓度是半导体态V02(M)的1000倍。另一方面,因为氢具有最小的离子半径,因此氢修饰能够维持钒氧骨架结构,保持声子结构没有明显变化。这种通过原位氢修饰的方法,在材料结构变化不大的基础上,完成了对电子-电子关联作用的有效调制,实现了电声去耦合调控,获得了能够在包含室温的宽范围温区内工作的热电性能。值得注意的是,能够在室温或者低于室温的温区内获得高ZT优值的简单氧化物结构是很少的。该实验表明对于电子-电子关联作用的调控将是实现电声去耦合调制,提升热电性能的强有力手段。 3.作者利用量子限域效应首次在二维ZrNCl纳米片材料中实现了高效的紫外光热性能。通过化学插锂和液相超声剥离的结合,第一次制备出了具有3～4个ZrNCl结构单层的二维超薄纳米片。在该二维结构体系中,原子层限域作用带来电子弛豫能量的增加；同时,由四原子组成的[Cl-Zr-N-Cl]单层的独特结构产生了更强烈的表面化学键振动。上述协同效应,增强了光生电子与声子的相互作用,进而产生了高效的紫外光能到热能的转换。在200mW/cm2的紫外光照下,二维ZrNCl纳米片可产生5.25W/g的热流,是块材样品的24倍,更是其他宽带隙半导体材料的几十倍,其光热转换效率可达到72%,是目前半导体材料紫外光热转换性能的最优值。该工作不仅实现了一种基于紫外光的新的能量转换形式,同时利用限域效应增强电声耦合的概念也为发展新的光热机敏材料提供了有益的指导。 4.作者通过向二维ZrNCl纳米片中引入缺陷的方法,提高了材料的电导率并缩减了能带隙,获得了提升的光电催化分解水性能,首次将金属氮卤化合物体系引入光电催化反应。在可见光照射下(λ≥400nm),含有少量氯缺陷的ZrNCl纳米片在1.6V (vs RHE)时的光电流达到3.3mA/cm2,是不含缺陷ZrNCl纳米片光电流值的7.3倍,含缺陷ZrNCl块材的22倍。实验表明,引入氯缺陷后,ZrNCl纳米片的电导率明显提高,有利于光电催化过程中的电荷转移；同时,含缺陷的ZrNCl纳米片光吸收边进入可见光区,提高了可见光的利用率。此外,相比于块体材料而言,其二维的形貌提供了更多与电解液的接触面积,且与导电基底的接触更为紧密。这种利用缺陷工程对二维纳米材料电子结构调制以实现光电催化过程优化的策略对于优化和发展新型光电反应催化剂具有较高的借鉴意义。
[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.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB34;O641

【共引文献】