Introduction
The arrangement of the atoms or ions in engineered materials contains imperfections or defects. These defects often have a profound effect on the properties of materials. We introduce the three basic type of imperfections: point defects, line defects (or dislocations), and surface defects. These imperfections only represent defects in or deviations from the perfect or ideal atomic or ionic arrangements expected in a given crystal structure. The material is not considered defective from technological viewpoint. In many applications, the presence of such defects is useful. There are few applications, though where we strive to minimize a particular type of defect. For example, defects known as dislocations are useful for increasing the strength of metals and alloys; however, in single crystal silicon, used for manufacturing computer chips, the presence of dislocations is undesirable. A crystal of pure alumina is transparent and colorless, but when we add a small amount of chromium, it creates a special defect, resulting in a beautiful red ruby crystal. In the processing of Si crystals for microelectronics, we add very small concentrations of P or B atoms to Si. These additions create defects in the arrangement of atoms in silicon that impart special electrical properties to different parts of the silicon crystal. The effect of point defects, is not always desirable. When we want to use copper as a conductor for microelectronics, we use the highest purity available. This is because even small levels of impurities will cause an orders of magnitude increase in the electrical resistivity of copper. Regions between different grains of a polycrystalline material, represent one type of defect. Ceramic superconductors, under ce...
... middle of paper ...
...layer composites represent advanced engineering materials that are shown to exhibit high structural stability, mechanical strength, toughness and resistance to fracture. The effect of the interface imperfections on the strengthening of NMMs with incoherent interfaces, by performing molecular dynamics simulations. Two types of interfaces are considered, a perfect one, and with discontinuities. Our simulations demonstrate that the result of the interaction between dislocations and interfaces is the creation of interfacial disconnections make of a dislocation that spreads within the interface, and a step entrapped at the interface. The energy calculations show these steps increase the total energy of the system and enhance the strengthening effect of the interface by adding extra barriers to slip transmission to improving the mechanical properties of the structure.
Microelectromechanical Systems (MEMS) are systems that are designed on a micro metre scale and have become more popular as the demand for devices to get smaller has increased. The main uses of these systems are for sensors, such as accelerometers and gyroscopes and other such devices like microscopy and inkjet nozzles for example. There are many materials that can be used for MEMS as the cost of the material is almost eradicated due to the micro size of the systems being produced. This brings materials such as gold, platinum and diamond can be used, as these materials have some properties which are very desirable for a MEM systems. The most common material that is currently used in MEMS is silicon and silicon based compounds as they possess many good properties for MEMS production. Most of the materials chosen for MEMS are semiconductor materials Figure 1 shows the properties of commonly used materials.
There are many types of distortions occurring in the ideal perovskite structure due to the flexibility inherent inside the perovskite structure. Resulting the tilting of the octahedra. Then displacement of cations takes place from the centres of their respective coordination in polyhedral. The distortion of the octahedral is accelerated by electronic factors. Most the physical properties of perovskite structure depend on these distortions. Particularly the electronic, magnetic and dielectric properties which are so important for many of the applications of perovskite materials. These materials have different useful magnetic and electronic properties. Most of the properties depends upon some defects like vacancies, dislocations, stacking faults, grain boundaries et...
In basic research, special model systems are needed for quantitative investigations of the relevant and fundamental processes in thin film materials science. In particular, these model systems enable the investigation of i.e. nucleation and growth processes, solid state reactions, the thermal and mechanical stability of thin film systems and phase boundaries. Results of combined experimental and theoretical investigations are a prerequisite for the development of new thin film systems and tailoring of their microstructure and performance.
Have you ever met a person with a deformed face? Are you that person? In the novel Wonder by R.J Palacio the main character August was born with a deformed face. The book starts with August deciding if he wants to start middle school. His mother has been homeschooling him since he was born through when he hit ten years old. When August goes to school for the first day, he get’s bullied, and gets constantly stared at. Throughout the school year, he gets bullied. She wants kids to know that they are heard when finishing this book and that you can’t control what you look like but you can control what people think of you. August deals with so much bullying throughout the school year. He goes through his friend betraying him, nasty comments, unwanted stares, and with no one actually wanting to get to know him except for a couple of them. Bullying affects him in so many ways, and yet he stays strong to who he is.
The basic mechanism for the single event effect in microelectronics includes the charge deposition and the charge collection. In the charge deposition process, there are two ways to release charge in semiconductor devices: (1) direct ionization is caused by the incident particles, and (2) indirect ionization is caused by the nuclear reaction between the incident particle and the device. Usually the deposition mechanism for heavy ions...
However, it can also be located in the in the bulk of the silicon both
Material with ionic bonding , including many ceramics such as MgO , also are resistant to slip . Movement of a dislocation disrupts the change balance around the anions and cations , requiring that bonds between anions and cations be broken .
Scanning probe microscopy in nano mechanical testing has started with the invention of the scanning tunneling microscope in the year 1981. Till then based on the type of principles there are number of models developed and are in use. Scanning probe microscopy found popularity owing to its ease in versatility in dealing with a number of issues, typically it is used to identify the material properties on nano to even pico scales. Scanning probe microscopy techniques such as atomic/friction force microscopy(AFM/FFM) are increasingly finding applications in tribological studies of engineering surfaces as well for finding surface texture etc. Atomic and molecular level details can be assessed using Scanning probe microscopy with great ease and the instruments are highly versatile. AFMs with suitable tips are being used to study issues like scratching, wear etc. Scratch and wear properties of variety of materials have been measured. Mechanisms of material removal are also studied. Localized surface elasticity maps of composite materials with penetration depths less than 10nm can be found using SPM with nano mechanical testing procedures. Nano indentation hardness and the young’s modulus of elasticity can be measured with a depth of indentation as low as 1nm. Scratching and indentation on the nano scale are powerful ways to screen for adhesion and resistance to deformation of ultrathin coatings. These studies provide insight into failure mechanisms of the materials and thin coatings. SPM in nano mechanical testing provides insight into the surface characterization and provided glimpse of failure mechanisms study. (Bhushan, 2001). The manner of using interactions between the probe and the surface to obtain an image is gene...
stresses in multi-layered microelectronic packaging are responsible for delaminationrelated failures especially during manufacturing. Materials with different coefficients of
[11] "TEM Basics." MATTER - Materials Science & Engineering Educational Software. The University of Liverpool, 25 July 2000. Web. 10 July 2010. .
There are considerable differences in published property data for Metal matrix composite. This is partly due to the fact that there are no industry standards for metal matrix composites, as there are for metals. Reinforcements and composites are typically made by proprietary processes, and, as a consequence, the properties of materials having the same nominal composition can be radically different. The issue is further clouded by the fact that many reinforcements and they are still in the developmental stage, and are continually being refined. Numerous test methods are used throughout the industry, and it is widely recognized that this is a major source of differences in reported properties. Some properties cannot be measured as they would be for monolithic metals. For instance, toughness is an important but hard to define material property. Standard fracture mechanics tests and analytical methods for metals are based on the assumption of self-similar crack extension; i.e., a crack will simply lengthen without changing shape. Composites, however, are non-homogeneous materials with complex internal damage patterns. As a result, the applicability of conventional fracture mechanics to metal matrix composite is controversial, especially for fibre-reinforced ma...
In this experiment, our aim is examining the microstructure of metals. By studying microscopic structures of metals, we determine which material fits best to a given application. We used the most common method, optical technique, to examine the microstructure.
Design , characterization, production and application of materials devices and systems by controlling shape and size of the nanoscale.
In modern days, silicon’s primary use is semiconductors in electronics. Nearly all electronics in the world have at least one semiconductor and that semiconductor wouldn’t be possible without silicon. The process of turning raw silicon into a usable resource is still unchanged, like everything, the process has been modernized and quickened with electric ovens and preciously controlled environments.
Grundmann, Marius. Physics of Semiconductors: An Introduction Including Devices and Nanophysics. New York: Springer, 2006. Print.