Effect of crystal alignment on the remanence of sintered NdFeB magnets
光的衍射英文作文
光的衍射英文作文Light DiffractionLight is a fundamental aspect of our physical world, and its behavior has been the subject of intense study and fascination for centuries. One of the most intriguing and complex phenomena associated with light is diffraction, which refers to the bending and spreading of light waves as they encounter obstacles or apertures. This phenomenon has profound implications in various fields, from optics and quantum mechanics to biology and technology.At its core, diffraction is a wave-like property of light, where the interaction between light and the physical structures it encounters leads to the interference and redistribution of the light waves. This process is governed by the principles of wave interference, where the constructive and destructive interference of light waves result in patterns of light and dark regions, known as diffraction patterns.The fundamental principles of diffraction can be understood by considering the wave nature of light. Light, like other forms of electromagnetic radiation, can be described as a wave, with a specific wavelength and frequency. When light encounters an obstacle or anaperture, the waves are forced to bend and spread out, creating a diffraction pattern. The specific characteristics of this pattern are determined by factors such as the size and shape of the obstacle or aperture, as well as the wavelength of the light.One of the most well-known examples of diffraction is the phenomenon of single-slit diffraction. When light passes through a narrow slit, the resulting diffraction pattern consists of a central bright region, known as the central maximum, surrounded by alternating bright and dark regions, known as diffraction fringes. The spacing and intensity of these fringes are directly related to the wavelength of the light and the width of the slit.Another important aspect of diffraction is the concept of the Fraunhofer diffraction, which describes the diffraction pattern observed at large distances from the aperture or obstacle. In this case, the diffraction pattern is characterized by a series of bright and dark spots, known as the Fraunhofer diffraction pattern. This pattern is particularly useful in applications such as optical imaging, spectroscopy, and the design of diffraction-based optical devices.Diffraction also plays a crucial role in the behavior of light in various natural and man-made systems. For example, the diffraction of light through small apertures or slits is responsible for the characteristic patterns observed in the interference of light, such as those seen inYoung's double-slit experiment. Additionally, the diffraction of light around the edges of objects or through small openings is responsible for the phenomena of diffraction fringes, which can be observed in various optical devices and natural phenomena, such as the colorful patterns seen in the wings of some insects or the halos and glories observed around the Sun or Moon.The study of diffraction has also led to the development of numerous applications in science and technology. In optics, diffraction is used in the design of various optical devices, such as diffraction gratings, which are used in spectroscopy and other analytical techniques. In the field of quantum mechanics, the wave-like nature of particles, as described by the de Broglie hypothesis, has led to the observation of diffraction patterns in the behavior of subatomic particles, such as electrons and neutrons.Furthermore, the understanding of diffraction has been instrumental in the development of modern imaging techniques, such as X-ray crystallography, where the diffraction of X-rays by the atoms in a crystal is used to determine the arrangement and structure of the atoms within the crystal. Similarly, the diffraction of light by various biological structures, such as the compound eyes of insects or the structures found in the wings of some butterflies, has inspired the development of biomimetic materials and devices.In conclusion, the phenomenon of light diffraction is a fundamental and fascinating aspect of our physical world. It is a testament to the wave-like nature of light and the complex interplay between light and the physical structures it encounters. The study of diffraction has led to numerous insights and advancements in various fields, and its continued exploration promises to yield further discoveries and innovations that will shape our understanding of the universe and the technology we use to interact with it.。
你相信安联奇迹吗英语作文
你相信安联奇迹吗英语作文Do You Believe in the Miracle of Allianz Arena?The term "Miracle of Allianz Arena" often evokes a sense of awe and wonder in the world of football. But do we truly believe in such miracles?For many football enthusiasts, the idea of a miracle is not just a stroke of luck or a fluke. It's a bination of determination, teamwork, and an unwavering spirit that defies the odds. In the case of the Allianz Arena, there have been moments when teams have staged remarkable ebacks, turning the tide of a seemingly lost game. These instances have left fans on the edge of their seats, hearts pounding with excitement and disbelief.Believing in the Miracle of Allianz Arena means having fth in the power of human potential and the unpredictable nature of sports. It's about acknowledging that even when the situation looks dire, there's always a glimmer of hope. The players' never-say-die attitude and their ability to rise above challenges can inspire us to believe that miracles can happen.However, some might argue that these so-called miracles are just rare occurrences, the result of a perfect alignment of circumstances rather than a supernatural force. They might point to the statistical improbability and the role of pure chance in determining the oute of a game.In my opinion, whether one believes in the Miracle of Allianz Arena or not depends on one's perspective. If you see football as more than just a game, but a platform for showcasing human resilience and the pursuit of the impossible, then it's not hard to believe in miracles. But if you approach it from a purely analytical and rational standpoint, miracles might seem like an exaggeration.In the end, the Miracle of Allianz Arena remns a topic that stirs passionate debates among football lovers. It serves as a reminder of the magic and drama that the sport can bring, and why we continue to hold our breath and hope for the unexpected every time the whistle blows.。
晶格常数的英文
晶格常数的英文English:The lattice constant, also known as the lattice parameter or lattice spacing, is the physical constant that describes the distance between unit cells in a crystal lattice. It is a fundamental property of crystals and is often represented by the symbol "a." The lattice constant can be determined experimentally using techniques such as X-ray diffraction or electron diffraction, and it plays a critical role in understanding the properties of materials and predicting their behavior under different conditions. The lattice constant also influences various physical and mechanical properties of materials, including thermal expansion, electrical conductivity, and mechanical strength.中文翻译:晶格常数，也称为晶格参数或晶格间距，是描述晶格中单位晶胞之间距离的物理常数。
这是晶体的一项基本性质，通常用符号“a”表示。
晶格常数可以通过X射线衍射或电子衍射等技术实验确定，它在理解材料性质和预测在不同条件下行为方面起着至关重要的作用。
晶体生长过程视频
up a crystal growing attempt
Solubility Profile
Solubility
Nucleation – fewer nucleation sites are better. Too many nucleation sites (i.e. dust, hairs, etc.) lower the average crystal size
Mechanics – mechanical disturbances are bad.
Peak positions for true atomic positions
Limiting the Resolution of the Data
Limited qmax = 11.54° Resolution = 2.5 Å
Set-up simultaneous crystal growing experiments
Factors Affecting Crystallization
Solvent – moderate solubility is best. Supersaturation leads to sudden precipitation and smaller crystal size
positions are still resolvable
Limiting the Resolution of the Data
Limited qmax = 14.48° Resolution = 2.0 Å
增强型场效应晶体管英文
增强型场效应晶体管英文Enhanced Field-Effect Transistors, or EFETs, are really cool components in electronics. They're like the superheroes of the semiconductor world, able to handle more current and voltage than regular FETs. And the way they do it is just fascinating.Talking about EFETs, I gotta mention their awesome gate structure. It's designed to amplify the electric field, allowing for better control over the flow of electrons. That's why they're called "enhanced" – they really take performance to the next level.One thing I love about EFETs is their versatility. They can be used in a wide range of applications, from high-speed computers to power electronics. And with their improved performance, they're helping to push the boundaries of what's possible in electronics.EFETs are also pretty efficient. They minimize powerloss and heat generation, which is crucial for maintaining stable operation and extending the lifespan of electronic devices. So not only are they powerful, but they're also energy-smart.In my opinion, EFETs are the future of electronics. As technology continues to advance, we're going to see more and more devices utilizing these enhanced transistors to achieve incredible levels of performance and efficiency. Who knows, maybe one day we'll have computers that run entirely on EFETs!。
单色光频率与折射率的关系英语
单色光频率与折射率的关系英语Refractive Index and Frequency of Monochromatic Light.In the realm of optics, the relationship between the frequency of monochromatic light and the refractive index of a medium plays a pivotal role in understanding the phenomena of refraction and dispersion. This intricate relationship governs the bending of light as it traverses the boundary between two dissimilar media and the subsequent separation of light into its constituent colors.Refractive Index: A Measure of Light's Velocity.The refractive index (n) of a medium is a dimensionless quantity that characterizes the medium's ability to impede the propagation of light. It is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v):n = c / v.A higher refractive index indicates that light travels slower in that medium. The refractive index is dependent on the wavelength of light, exhibiting a phenomenon known as dispersion.Dispersion: Wavelength Dependence of Refractive Index.Dispersion arises due to the fact that different wavelengths of light interact with the charged particles within a medium to varying degrees. As a result, the refractive index of a medium changes with the wavelength of light. This variation is typically observed as a gradual increase in the refractive index with decreasing wavelength.For a given medium, the refractive index is generally higher for shorter wavelengths (higher frequencies) oflight compared to longer wavelengths (lower frequencies). This means that blue light, with its shorter wavelength, experiences a greater refractive index than red light,which has a longer wavelength.Refraction: Bending of Light at an Interface.When light encounters the boundary between two media with different refractive indices, it undergoes refraction. This phenomenon is characterized by a change in the direction of light as it crosses the interface. The angle of refraction (r) is related to the angle of incidence (i) and the refractive indices of the two media (n1 and n2) by Snell's law:n1 sin(i) = n2 sin(r)。
光与物质相互作用英文
光与物质相互作用英文Light-Matter Interaction.Light and matter interact in a variety of ways,including absorption, emission, scattering, and reflection. These interactions are essential for many natural phenomena, such as photosynthesis, vision, and the colors of objects. They are also used in a wide range of technologies, such as lasers, solar cells, and optical fibers.Absorption.When light is absorbed by matter, the energy of thelight is transferred to the matter. This can cause the matter to become excited, which can lead to a change in its chemical or physical properties. For example, absorption of light can cause a molecule to dissociate, or it can causean electron to be promoted to a higher energy level.Emission.When matter emits light, the energy of the light comes from the matter itself. This can happen when an excited atom or molecule returns to its ground state, or it can happen when an electron recombines with a hole. Emission of light is the basis for many light sources, such as lasers and LEDs.Scattering.When light is scattered by matter, the direction of the light is changed. This can happen when light interacts with particles that are smaller than the wavelength of light, or it can happen when light interacts with rough surfaces. Scattering of light is responsible for the blue color of the sky and the white color of clouds.Reflection.When light is reflected by matter, the direction of the light is changed, but the wavelength of the light remains the same. This can happen when light interacts with asmooth surface, such as a mirror, or it can happen when light interacts with a transparent material, such as glass. Reflection of light is used in a variety of applications, such as mirrors, lenses, and optical fibers.The interaction of light with matter is a complex and fascinating topic. It is essential for understanding a wide range of natural phenomena and technologies.Here are some additional details about each of the four types of light-matter interactions:Absorption.When light is absorbed by matter, the energy of the light is transferred to the matter. This can cause the matter to become excited, which can lead to a change in its chemical or physical properties. For example, absorption of light can cause a molecule to dissociate, or it can cause an electron to be promoted to a higher energy level.The amount of light that is absorbed by matter dependson the wavelength of the light and the properties of the matter. Some materials, such as metals, are very good at absorbing light, while other materials, such as glass, are very poor at absorbing light.Emission.When matter emits light, the energy of the light comes from the matter itself. This can happen when an excited atom or molecule returns to its ground state, or it can happen when an electron recombines with a hole.The wavelength of the light that is emitted by matter depends on the energy difference between the two states involved in the transition. For example, when an electron recombines with a hole in a semiconductor, the energy difference between the two states is typically in the visible range, so the emitted light is visible light.Scattering.When light is scattered by matter, the direction of thelight is changed. This can happen when light interacts with particles that are smaller than the wavelength of light, or it can happen when light interacts with rough surfaces.The amount of light that is scattered by matter depends on the size and shape of the scattering particles and the wavelength of the light. For example, small particles scatter light more effectively than large particles, and short-wavelength light is scattered more effectively than long-wavelength light.Reflection.When light is reflected by matter, the direction of the light is changed, but the wavelength of the light remains the same. This can happen when light interacts with a smooth surface, such as a mirror, or it can happen when light interacts with a transparent material, such as glass.The amount of light that is reflected by matter depends on the refractive index of the material. The refractive index is a measure of how much light is bent when it passesfrom one material to another. Materials with a high refractive index, such as glass, reflect more light than materials with a low refractive index, such as air.。
光学纯对映体 英文
光学纯对映体英文## Enantiomers and Optical Purity.In the realm of chemistry, chirality refers to the property of a molecule that lacks mirror symmetry, muchlike our left and right hands. Chiral molecules exist in two distinct forms known as enantiomers, which are mirror images of each other but cannot be superimposed. Enantiomers are like two non-identical twins, sharing the same molecular formula and connectivity but differing in their spatial arrangement.Optical purity, a crucial concept in stereochemistry, quantifies the enantiomeric excess of a chiral compound. It measures the proportion of one enantiomer relative to the other in a mixture. A mixture containing equal amounts of both enantiomers is considered racemic and has an optical purity of 0%. Conversely, a mixture containing only one enantiomer is optically pure and has an optical purity of 100%.### Separation of Enantiomers.The separation of enantiomers is a challenging yet essential task in many fields, including pharmaceuticals, agrochemicals, and fragrances. Various techniques can be employed to achieve this, including:Chiral chromatography: This technique utilizes achiral stationary phase that interacts differently with different enantiomers, allowing for their separation.Chiral resolution: This involves converting a racemic mixture into a pair of diastereomers, which can then be separated by conventional methods.Enzymatic resolution: Enzymes, being chiral themselves, can selectively catalyze reactions with one enantiomer over the other, leading to the formation of optically pure products.### Optical Purity Measurement.Optical purity can be determined using various methods, such as:Polarimetry: This technique measures the rotation of plane-polarized light as it passes through a chiral sample. The magnitude and direction of rotation depend on the enantiomeric composition of the sample.NMR spectroscopy: Chiral solvents or chiral shift reagents can be used in NMR spectroscopy to differentiate between enantiomers based on their different chemical shifts.Chromatographic methods: Chiral chromatography or capillary electrophoresis can be used to separate enantiomers and determine their relative abundance.### Significance of Optical Purity.Optical purity is of paramount importance in several areas:Pharmacology: Many drugs are chiral, and their enantiomers can have different pharmacological properties, including efficacy, toxicity, and metabolism. Enantiopure drugs offer advantages in terms of safety and effectiveness.Agrochemicals: Herbicides and pesticides can be chiral, and their enantiomers may differ in their selectivity and environmental impact. Optical purity ensures the targeted control of pests and weeds.Fragrances and flavors: The fragrance and flavor of chiral compounds can depend on their enantiomeric composition. Optical purity control allows for the creation of specific scents and tastes.### Applications of Chiral Compounds.Chiral compounds find widespread applications invarious industries:Pharmaceuticals: Enantiopure drugs include ibuprofen,naproxen, and thalidomide.Agrochemicals: Herbicides such as glyphosate and pesticides like cypermethrin are chiral.Fragrances and flavors: Enantiopure compounds like menthol, camphor, and limonene contribute to thedistinctive scents and tastes of products.Materials science: Chiral polymers, liquid crystals, and self-assembling systems have unique properties and applications in optics, electronics, and nanotechnology.### Conclusion.The concept of enantiomers and optical purity is crucial for understanding the stereochemistry of chiral compounds. The ability to separate and determine the optical purity of enantiomers is essential in numerous fields, including pharmaceuticals, agrochemicals, and fragrances. The significance of optical purity lies in itsimplications for the safety, efficacy, and properties of chiral compounds in various applications.。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
NdI5.4Fe77.8B6.8 magnets of various degrees of crystal alignment have been prepared by the conventional powder metaHurgy techni.que. The alignment of these magnets have been determined by x-ray diffraction and fitting the standard deviation of a Gaussian distribution for the relative intensity versus the angle between the normals of (hkl) and the tetragonal c axis. The standard deviation is a good indicator for crystal alignment. An aligning field of 8 kOe is found to be essential to obtain a well-aligned NdFeB magnet. The remanence of sintered magnets is directly affected by the crystal alignment. Furthermore, the effect of crystal alignment on the remanence follows the theoretical prediction of the Stoner-Wohlfarth model. Below the spin reorientation temperature, the effect of crystal alignment on the shape of hysteresis loop becomes more significant. The remanences extrapolated from first and second quadrant of the hysteresis loops have been found to be consistent with the prediction of Stoner-Wohlfarth model.
Permanent address: Magnetic and Electronic Materials Research Laboratory, Hitachi Metals, Ltd., Kumagaya, Saitama 360, Japan.
INTRODUCTION
Crystal alignment plays a significant role in affecting the magnetic properties of sintered NdFeB magnets. Several methods have already been proposed to evaluate the crystal alignment of these magnets using x-ray diffraction patternso Forinstance, Tenaud, Chamberbord, and Vanoni l assumed that the crystal alignment obeys the Gaussian distribution, and then fitted the ratio of the x-ray diffraction intensities of the aligned magnet to the corresponding peak intensity of the random sample to the angle between the c axis and the normal of (hkl) to obtain the standard deviation. Zhou, Zhou, and Graham 2 correlated the crystal alignment to the half-width of the rocking curve of a certain (001) plane. Chang, Wu, and Liu 3 studied the crystal alignment using pole-figure analysis. All these experiments were performed at room temperature. It is known that NdFeB magnets exhibit an axial to conical spin reorientation (SR) when cooled to below 135 K.4 It is of interest to see whether the crystal alignment determined by these methods could be further extended to describe its effect on the remanence in conjunction with SR phenomena. In this paper, we report the effect of crystal alignment on the remanence M, of Nd 15 .4 Fens B6 . 8 sintered magnets using the method described in Refo 1 and compare M, with the theoretical calculation based on the Stoner-Wohlfarth model. 5 This model is also extended to describe the effect of crystal alignment on the remanence when SR occurs.
(1)
The magnets used in this study were prepared by the conventional powder metallurgy technique. Nd I5 .4 Fe77.8 B6.8 magnets with various degrees of alignment were prepared by varying the applied magnetic field from 0 to 955 kAim (12 kOe) during compaction in a die press. An isotropic magnet, pressed in a nonmagnetic die and without applying a magnetic field, was used as the reference for comparing the x-ray diffraction intensities. A Rigaku diffractroa)
Effect of crystal alignment on the remanence of sintered NdFeB magnets
T. Kawai,a) B. M. Ma, S. G. Sankar, and Wo Eo Wallace
Mellon Institute and MEMS Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 1saturation magnetization of the magnet, (J is the angle between the tetragonal c axis and the applied magnetic field, and ec is the cone angle when SR occurs. Cone angles of 0·, 26·, and 30· were used for temperatures of 295, 77, and 4.2 K, respectively. The ( + ) and ( - ) signs used in Eq. ( 1 ) stand for the angles between the applied magnetic field and the magnetization direction of a crystal before and after spin flippingo Since the saturation magnetization Ms is difficult to determine precisely, we assume that all Fe in the magnet exists in the Nd2 Fe 14B phase and calculate Ms by fonowing method:
EXPERIMENT
meter of Co radiation was used in measuring the diffraction intensities. The relative intensity was determined by measuring the ratio of peak heights of the anisotropic magnets to those of the corresponding isotropic reference. This relative intensity was then plotted against the angle 8, the angle between the normal of (hkl) and the tetragonal c axis. This data were then fitted for a Gaussian distribution to obtain a standard deviation a, which then acts as an indicator for the crystal alignment. The My at room temperature was determined by tracing the M-H curve on a IO-mm-cubic sample with a peak applied field of 1590 kA/m (20 kOe). The Mr in the temperature ranging from 4.2 to 273 K were measured on spherical samples of diameter of 3 mm with a VSM-superconducting magnetometer with a peak field of 9 T (90 kOe). A demagnetizing factor Oq1T was applied to obtain the corrected Mr. The specific density of magnets was measured by Archimedes's method. The theoretical M" based on the Stoner-Wohlfarth model, was calculated using the following expression: