【HUST】Network Security Nano | 2023 Graduate Nanotechnology Examination Reference

Table of contents

2 Structural properties of nanomaterials

Printing suggestions: PPT color printing (so that the focus is more prominent), 12 PPTs per side, simply make a keyword list, and you can see it clearly through personal testing. If you don’t want to print in color, it might be better to have fewer sheets.

Question type: 25 multiple-choice or single-choice questions (does not differentiate between multiple-choice or single-choice questions) + 4 major questions.

The author's final score: I only passed the low score of 88 in the final exam, which proves that the experience in this article is not of value and reference in a strict sense. There was a big question that I read wrongly, and I scrawled a bit when I was writing it. I guess I will deduct a lot of money. Therefore, perhaps the most important experience in this article is the question type and the blood and tears lessons (meaning read the questions carefully and this paper is not difficult at all).

~~I originally wanted to post it before the exam, but I always felt that the exam was more liberal arts in nature and I was worried that I might mislead others by posting randomly.~~

1 What are nanomaterials?

The key point is to distinguish what these concepts are, but during the exam, it is better to just look at the title of the first page of each PPT.

Nanometer is a unit of length measurement, 1 nanometer = 10^-9^ meters.
NanostructureUsually refers to tiny structures with a size below 100 nanometers (1-100nm).
Nanomaterials means that at least one dimension in three-dimensional space is in the nanoscale range (10^-9^~10^-7^m) or is composed of them as basic units Material
The technology that studies and processes substances and materials on a nanometer scale is callednanotechnology. Nanotechnology is essentially a technology that uses single atoms and molecules to create materials.
Nanoscience: The science that studies the preparation of materials and their properties and phenomena at the nanoscale.
Nano science and technology (referred to asNano technology): manufacturing and researching nanoscale (10^- 9^～10^-7^m) science and technology of devices and materials.

NOTICE!
The difference between nanostructures and nanomaterials:

Shakusize范围：

Nanostructure: refers to tiny structures with a size below 100 nanometers (1-100 nanometers). These structures can be nanoparticles, nanowires, nanosheets, etc. They are not necessarily complete materials, but rather tiny building blocks.

Nanomaterials: Refers to materials with at least one dimension in the nanoscale range (10^-9^~10^-7^ meters) in three-dimensional space. These materials can be nanoparticles, nanofilms, nanotubes, etc., which are complete materials with specific chemical and physical properties.

Construction：

Nanostructures: Usually form part of a larger material or are tiny organizational units that can be dispersed in macroscopic materials.

Nanomaterials: are complete materials that have nanoscale dimensions in at least one dimension. These materials can exist alone or be used to build larger systems.

Characteristics：

Nanostructure: Usually has properties different from those of macrostructure. These properties can be due to size effects, surface effects or quantum effects.

Nanomaterials: Because their overall size is at the nanometer level, they have specific nanoscale properties that may be different from macroscopic materials, such as electronics, optics, Properties such as magnetism may differ significantly from their large-scale counterparts.

In general, nanostructures usually refer to small-sized structural units, while nanomaterials are complete materials,which have nanoscale dimensions in at least one dimension< /span>. Both are important in the field of nanotechnology and nanomaterials because their properties and applications can sometimes be manipulated and exploited at the nanoscale.

NOTICE! Multiple choice question ( I didn’t test this question, but I did test which equipment can perform atomic level analysis. In fact, you can find the answer by flipping through the PPT )
Which of the following inventions are landmark inventions for nanotechnology:
Scanning tunneling microscope (left) and atomic force microscope (right)< /span>

Nanorods, nanowires
Quasi-one-dimensional solid nanomaterials refer to nanoscale in two-dimensional directions, and the length is much larger than the scale in the above two-dimensional directions. Even new nanomaterials in macroscopic quantities. Those with a small aspect ratio (ratio of length and diameter) are called nanorods and those with a large aspect ratio are called nanowires

Nanorods: have a small aspect ratio (ratio of length to diameter) and a circular cross-section. Generally less than 20.
Nanowires: Large aspect ratio and circular cross-section.
The cross-section of the nanoribbon is rectangular.
Semiconductor and metallic nanowires are often called quantum wires.
Coaxial nanocable: A nanowire with a semiconductor or conductor as its core and a heterogeneous nanoshell (semiconductor or conductor) as outer shell. The outer shell and core wire are coaxial.

2 Structural properties of nanomaterials

The following content is supplementary explanation by the teacher. Please read this part of the PPT directly and copy the principles during the exam.

The principle test is worth 10 points for a big question.

Quantum size effect:
- The smaller the particle size, the larger the discrete energy level (which in turn corresponds to the excitor energy level and the energy level of the excited state).
- Phenomenon: Blue shift occurs, that is, the spectrum moves toward ultraviolet wavelengths (short wavelengths).
- Practical application: Can be used to control the color of the spectrum.
Small size effect:
- The size of the nanoparticles is equivalent to or smaller than the physical characteristics such as de Broglie wavelength,the periodic boundary conditions will be destroyed, Its acousto-optical, electromagnetic and thermal properties will have new characteristics.
- Phenomenon: Pure metal fully absorbs the solar spectrum and turns black; the melting point of gold becomes lower; some materials appear superconducting.
- Practical application: Incorporating a small amount of ultra-fine silver powder can lower the melting point of the material and lower the metallurgical sintering temperature, thus reducing the requirements for the container.
surface effect
Macroscopic quantum tunneling effect (the basis of future microelectronic device research): Magnetic particles smaller than the critical size will appear paramagnetic. When the total energy of a microscopic particle is less than the barrier height, the particle can still cross the barrier.

3 Other properties of nanostructures

All of the following were tested.

Super hydrophobic: Contact angle with water>150 degrees. Also known as theself-cleaning effect, it can be used to keep surfaces clean and prevent the invasion of pathogens. It can be used to prevent snow, pollution, oxidation and electric current. conduction and can also be used to reduce drag on water surfaces. Often used to make clothes.

NOTICE! Multiple choice question
Which organisms in nature have hydrophobic properties?
Lotus leaves, plants such as rice and taro, and bird feathers.

Naturally occurring nanostructures and their properties:

butterfly wing color
water strider legs
Structural phototaxis of mosquito and moth eye effects
High adhesion effect of geckos flying over eaves and walls
human skeleton

NOTICE! big topic

I remember what the teacher said, but if I look at the PPT and it is different from what the teacher said, I still need to look at the PPT directly. What is the preparation technology of
nanostructures?

Lithography technology (micro-nano structure)

Self-assembly technology (lower stability than photolithography technology)

template technology

phase separation technology

Electrospinning technology (preparation of nanofibers from polymers)

NOTICE! big topic

Also tested the physical preparation technology of nanomaterials.

4 Nanostructure detection technology

Electron diffraction patterns were not tested at all, nor were the differences between scanning tunneling microscopy (STM) and atomic force microscopy (AFM).

Bright field photos have clear black and white and dark areas are not obvious.
The center dark field photo is blurry in black and white and has rich details in the dark area.

Electron diffraction pattern:

Single crystal: spots. A solid circle in the middle with spots around it.
Amorphous: diffuse diffraction rings. A large spot with an indistinct hollow circle around it. You have to cover most of the middle part so there will be a slight halo.
Polycrystalline: Diffraction rings (halos). A large solid circle in the middle and concentric hollow circles around it. But the middle part must be covered so that the hollow circles on the side can be displayed, otherwise it will be obscured by the light of the big circle in the middle.
Nanoribbon radiation damage.

Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)

NOTICE! Big question
(1) Quantum tunneling effect [Principle of scanning tunneling microscope (STM)]
In classical mechanics, when the height of the potential barrier is greater than the energy of the particle When the energy is large, particles cannot pass through the potential barrier.
In quantum mechanics, the probability of a particle passing through a potential barrier and appearing on the other side of the barrier is not 0. This phenomenon is called the tunnel effect a> (2) Van der Waals forces between atoms [Principle of Atomic Force Microscopy (AFM)].
The tunneling effect is a manifestation of the wave nature of microscopic particles (such as electrons, protons and neutrons).

NOTICE! Multiple choice question
Which instrument has the highest resolution currently? Scanning Tunneling Microscope (STM)

The following content is part of the test, but it is quite different from what I memorized. Just look at the PPT.

X-rays and Scherrer's Formula
A Cu target is used to generate characteristic rays. Can be used to identify crystals. Complete crystal
The incorporation of Zr chromium into TiO2 crystal will cause lattice expansion and low angle shift.
BET method: It can be used to measure the specific surface area, and can be used to measure the specific surface area, pore volume, pore size distribution and nitrogen adsorption and desorption curves of particles (nanomaterials). It plays an important role in studying the properties of particles. Nitrogen has adsorption properties and can be used as adsorbate.
> Samples can be stored in glass bottles

5 Applications of Nanomaterials

For example, the toxicity of nanometers, environmental pollution methods, etc.