Papers by Keyword: Foam

Abstract: In commercial CMP tools, slurry is applied near the pad center. As the pad rotates, more than 95% of the fresh slurry flows directly off the surface due to bow wave formation and inertial forces without ever entering the pad-wafer interface, resulting in low slurry utilization [1]. Furthermore, some slurry that manages to go under the wafer stays on the pad, mixes with fresh slurry and re-enters the pad-wafer interface. This used slurry contains reaction products, foam and pad debris (due to pad conditioning) that cause wafer-level defects [2]. Such defect-causing by-products keep recirculating on the pad during polishing and accumulate near the retaining ring over time. Also, since large amounts of DI water are used between wafer polishes to rinse off the debris and reaction products, appreciable amounts of water may stay on the pad and inside the grooves. When fresh slurry is introduced to polish the next wafer, it mixes with the residual water and is diluted, resulting in lower material removal. As such, the current slurry application method does not provide efficient slurry utilization and leaves significant room for improving defect levels. Moreover, the constant sweeping of the conditioner arm during in-situ conditioning results in uneven slurry distribution and introduces additional challenges when it comes to carrier multi-zone pressure control for reduced within-wafer removal rate non-uniformity.

Abstract: This article deals with thermal insulation sandwich materials and with their flexural properties. Suitability of designed testing method is confirmed according to experimental research. According to proposed method, flexural properties such as flexural strength and modulus of elasticity are stated. Type and mechanism of destruction sandwich materials during tests are described also.

Abstract: Cellular material such as aluminium foam has been considered as a potential material for energy absorption upon impact and blast loadings. One of the most important properties that contribute to this feature is the densification strain. At high impact velocity, prediction of the densification strain from quasi-static engineering stress-strain curve has been found inadequate. Furthermore, theoretical prediction using the equation proposed by Reid et al. always over-predicts the dynamic crushing stress. Formation of the shock wave at high impact velocity is believed to further increase the densification level of the foam. However, this effect is disregarded when determining the densification strain quasi-statically. The present study aims to address this issue by determining the densification strain experimentally from impact tests. Forty cylindrical aluminium foams with three different lengths were used as projectiles and were fired towards a rigid load cell by using a gas gun. The peak forces generated from the impact were recorded and analysed. The experimental densification strains were determined physically by measuring the deformation of the foam projectiles after the tests. It is concluded that, at high impact velocity, the densification strain varies with the initial impact velocity. Therefore an appropriate value of densification strain needs to be used in the equation of dynamic crushing stress for a better approximation.

Abstract: All components of a huge machine tool need to work together perfectly to ensure not only a quality finished product, but operator safety. One of those many components is the material of support panels and moving parts in the machine construction. Mechanical structure of the machine, in most cases does not reach the technical level of regulatory techniques or electric drives and potential increase in dynamics, speed or accuracy of the machines remain unused. Used classic construction materials, steel or light alloy then zoom in to limit their physical capabilities. Designers have machine tools or robots are forced to solve the formidable task in the form of reducing the weight of the moving parts while maintaining or even increasing stiffness with respect to the thermal stability or damping. Laminates are for construction of production machines, robots and manipulators of crucial importance. One big advantage is the high rigidity while maintaining low specific weight. The presented paper is focused on the investigation of composite sandwich construction produced by prepreg technology, which is the suitable production choose for construction of machine tools parts. First of all, the production of sandwich structures with cork core, honeycomb core and foam cores are compared and described. In terms of the production process it is a method very friendly to the environment, since there are no leaks styrene vapours into the air. Since it is important from the perspective of a manufacturer of transport or machine industry manufactured from environmentally friendly materials, so naturally from materials that are from the perspective of safety of passengers (operators of machine tools or robots) at a high level, when any accident was lowest possible hazard due to fire (burn materials used) and terms of the strength of composite materials. This is one of the major scientific articles and to find the most ideal surveyed composite sandwich materials that would be the greatest possible extent fulfils the required properties. In the experimental part of the article are compared and investigated the mechanical characteristics of composite sandwich structures with regard to varying number of layers of predimpregnated skin materials due to the different types of core materials suitable for use in the machine industry. In addition, these characteristics are an important part of the article research because described the influence number of layers to values of the bending stiffness those composite structures.

Abstract: This article completely investigates from nonwoven to PET/PU composite board on the variations of absorption coefficient by using standard impedance tube with four microphones. Recently, PET/PU composite board is becoming a popular and functional material because of the high flexibility in the abilities, such as thermal protection, chemical-proof, acoustic-resistance and etc.. Thus, it is important to realize the variations of absorption capability from single material to complete composite material, and can feedback some suggestions to the designer. Results shows that nonwoven only has a stable increase in absorption coefficient with the frequencies because of the inherent porous characteristics. With the substantial properties, foam has lower absorption coefficient and two peaks occurring in the higher frequencies. These both peaks are caused by the resonance between wave and foam at specified frequency. With an additional nonwoven in the rear side of composite foam, absorption coefficient of PET/PU composite board will effectively increase. Based on the diverse applications, absorption coefficient of PET/PU composite board can be flexible modulated to consistent with the requirements.

Abstract: In recent years, with the deepening of China's reform and opening up policy, the rapid development of the national economy and urban high-rise buildings and underground engineering increasing, many kinds of malignant fire have become increasingly complex and frequent. In the event of a fire, it may cause great loss of life, serious injuries and state property. In the absence of the necessary rescue equipment, fire brigade and emergency departments in fire and explosion engineering, engineering rescue and various natural disasters will delay the rescue, even can do nothing to rescue. This proves the forcible entry tools play a significant role in fire fighting and rescue. Therefore, the fire brigade and rescue departments should equip with efficient forcible entry tools for rescue as soon as possible.

Abstract: Red mud foam lightweight thermal insulation material was prepared by red mud, fly ash, cement as main raw materials, adding a certain amount of adhesive, through ingredients, mixing, molding, foam, sintering process. The influence of the ratio of red mud and fly ash on the properties of materials was studied and the mechanism of influence was analyzed. The test results show that performances of the samples were best when the ratio of red mud and fly ash is 5:4 and its flexural strength is 0.44MPa, compressive strength is 1.23MPa, density is 481kg/m³.

Abstract: Alumina lightweight insulation bricks were prepared from alumina powders using foaming method. In this paper the influences of foam addition amount (600, 800, 1000, 1200ml/kg) on properties of Alumina lightweight insulation brick were discussed. The phase composition is analyzed by XRD and the microstructure is characterized by SEM. The results show that the bulk density of alumina lightweight insulation brick is 0.63g/cm³,cold compressive strength is 10.53MPa, linear change rate after firing is -4.5% and reheat linear change rate is -0.27%,which synthesized under 1000ml/kg foam amount after firing at 1550°C for 3h. The results indicate that the density of alumina lightweight insulation brick is reduced with the increase of foam addition amount, when the addition amount is more than 1000ml/kg, cold compressive strength decreased significantly and linear shrinkage increased obviously.

Abstract: In this work a new method of Ti-void composites (foam, scaffold) preparation is shown. In this process as a space holder particles we have applied a saccharose crystals (table sugar) with size up to 1.3 mm. After Ti and saccharose particles mixing and pressing, a green compacts composed of sugar and Ti grains were produced. Then, the sugar crystals were removed by its dissolution in water, which lead to open spaces (pores) formation in the green compacts. Then the compacts were sintered at 1250 °C. Alternatively, a sugar was evaporated during sintering without water dissolution. The foams were investigated by SEM, XRD and computed tomography. Such prepared void metal composites have porosity of about 72% and average pore size of about 0.7 mm. The pores have cubical shape corresponding to sugar crystals shape. The method is very promising in foams preparation and the made Ti-void composites can be applied for hard tissue implants, for example.

Abstract: This paper describes experimental investigation on the response of new advanced materials to low and high velocity load. Foams were designed using two types of porous lightweight spherical raw materials with dimensions of 30-100 μm, combined with polymer matrix. Prism shaped specimens were prepared and loaded to obtain physical-mechanical parameters bulk density, compressive and flexural strength under quasistatic load and impact strength. The load-displacement data were captured. The slab specimens were prepared of selected materials, covered with a layer of ballistic laminates on both surfaces to form the sandwich element and were subjected to the blast load of 100 g Semtex 1A from a distance of 10 cm. Blast energy absorption was measured on test rig STAND T0-B according to methodology M-T0-B VTÚO 10_09.