Papers by Keyword: Porous Material

Abstract: There are significant impacts on the safty of tunnels because of porous materials.In order to avoid serious accidents of tunnels, Porous materials of carbonate rocks under the condition of low temperature and high pressure have been studied in the paper. Samples of local carbonate rocks have been collected from carbonate rock formation. Special machine was designed to simulate the condition of low temperature (10°C-20°C ) and high pressure (1-30Mpa) undergroud 4000M in jinping.Samples of local carbonate rocks have been tested in the machine. Spectrographs and scanners have been used to observed the change of porous materials of carbonate rocks.Results of the technological measurements show that the change of porous materials of carbonate rocks is affected by low temperature and high pressure.With the change of low temperature and high pressure, surface chemistry is affected throughout the surface of carbonate rocks. When the temperature of carbonate rocks exceed 15°C and pressure less than 18Mpa,there will be new compounds on the surface of carbonate rocks. These new compounds will change the porosity and thesaturated permeability of carbonate rocks.The change may led to serious accidents of tunnels.If we want to avoid these serious accidents,we must keep the temperature of carbonate rock formation less than 15°C and pressure exceed 18Mpa.

Abstract: Unidirectional freeze-drying method has been tried to prepare biomimetic aligned porous materials (APM) from natural macromolecules such as chitosan, gelatin, alginate, carrageenan, various starches, and their composites. All the porous materials have high porosity and surface area, although the pore morphology varies for different sources of natural macromolecules, composition and concentration of solution, as well as crosslinking degree. The APM has potential applications in bioseparation, biomedical engineering, tissue engineering, food and environmental protection.

Abstract: This paper presents a method called zinc oxalate (ZnC₂O₄) recurrence method to prepare porous zinc oxide (ZnO) films via templating with polystyrene (PS) spheres. Effects of calcination time and temperature, concentration of ZnC₂O₄ in precursor solution on ZnO films were studied. Optimal synthetic conditions and structural features of ZnO films were investigated by DTA, XRD and SEM. Experimental results show that porous ZnO films can be easily prepared by zinc oxalate recurrence methods.

Abstract: Spark plasma sintering has been used for decades in order to consolidate a wide variety of materials and permitting to obtain fully dense specimens. This technique has been mainly applied to ceramics. This paper concentrates on an unusual use of spark plasma sintering system: obtaining innovative materials especially architectured ones. Different applications are presented. Firstly, the SPS technique has been used to elaborate nanometers grain size materials or containing nanoscale microstructure. This is possible since the sintering temperature and the holding time are far lower in the SPS compared to other techniques. Then SPS has been used to realize diffusion bonding. In that case again, bonding can be realized at low temperature and for short time. It permits for example to realize bonding between two copper layers which is of a great importance for microelectronic applications. It is worth noting that this bonding can have the same mechanical strength as pure copper even for diffusion time of a few minutes. Secondly, bonding has been also carried out between a metallic layer and a ceramic one. This could lead to design of new layered materials combining interesting properties in terms of mechanical strength but also in terms of electrical resistance. The SPS machine has also been used to obtain porous materials (cobalt alloys or copper) with an adapted microstructure (porosity, tortuosity,). These structures could open new perspectives for biomedical or for microelectronic applications. All these examples lead to a better understanding of the physical processes which happen during spark plasma sintering.

Abstract: In this work, a two-dimensional numerical model of heat and mass transfer for the convective drying process of ceramic material was developed. The governing equations of fully coupled non-linear partial differential was derived from the most comprehensive model with considering the heat, moisture and gas transport along with the influence of microscopic pore temperature gradient. Through validation the distribution of the measured variables and coefficients (diffusivity) show a good agreement with the drying stage in porous material.

Abstract: The main objective of here presented research is a design the scaffold/porous titanium (Ti) alloy based composite material demonstrating better biocompatibility, longer lifetime and bioactivity behaviour for load-bearing implants. The development of such material is proposed by making a number of consecutive tasks. Modelling the mechanical, biomechanical and biological behavior of porous titanium structure and an elaboration of results is performed by mathematical methods, including FEM and fuzzy logic. The development of selected Ti-13Zr-Nb alloy with designed porosity and no harmful effects is made by powder metallurgy (PM) with and without space holders, and by rapid prototyping with an use of selective laser melting (SLM). The development of an oxidation technology resulting in high corrosion resistance and bioactivity is carried out by electrochemical oxidation, gaseous oxidation and chemical oxidation, and their combination. The HA depositon is made by electrochemical and chemical (alternate immersion) methods. The core material is designed as a combination of natural polymer and bioceramics in order to allow slow dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing local inflammation processes, and sustaining the mechanical strength close to that of non-porous material.

Abstract: Research on improvement of structure and fabrication methods of the bone implants are carried out for many years. Research are aimed to shape the structures, that will have a Young's modulus value similar to the value of the human bones Young's modulus. Depending on the porosity, Young’s moduli can even be tailored to match the modulus of bone closer than solid metals can, thus reducing the problems associated with stress shielding of a human bones. The designed structure should also be characterized by a high abrasion and corrosion resistance to and allow bone ingrowth in the implant material to make the best bone-implant fixation. For this purpose, implants should have a porous structure with an appropriate pore size and with open-cell porosity. Material for bone implants must also have a high biocompatibility and bioactivity. Following these requirements, the metallic porous materials appear to be the most suitable material for bone implants. In this paper a various methods of a porous materials fabrication for bone implants are listed. It was shown that titanium and its alloys (e.g. Ti6Al4V or Ti13Nb13Zr) are widely used as biomaterials for implants. Research in order to increase their wear and corrosion resistance and to improve their biocompatibility and bioactivity are still carried out. One of the most effective methods of manufacturing the porous materials is a powder metallurgy (PM). In this paper the results of research under shaping the structure of the porous titanium alloy Ti13Nb13Zr are also presented. As a manufacturing method of the porous material from the investigated and mentioned above Ti alloy, the powder metallurgy (PM) was choosen - with and without the use of a space holders. Method of fabrication a spherical powder from the aforementioned Ti alloy and results of its morphology research are discussed. The applied powder compaction method (with use and without use of space holders) and the influence of a sintering process on the final microstructure morphology of porous material obtained from Ti13Nb13Zr alloy are also presented and discussed.

Abstract: In this document, using the anti-squeezed force model in the narrow parallel plate when fluid is squeezed, the equivalent stiffness and damping model is derived. It is further verified that it can increase the stiffness and damping while there are oil between the joint interfaces theoretically. Because the contact state of oily porous material can divide into liquid and solid parts, the document supposes that it is correct and effective to think the stiffness and damping of the two parts as shunt connection.

Abstract: The research on water vapor transmission (WVT) has an important function on analyzing moisture transport through building materials. According to ASTM Standards, there are two traditional methods (Dry cup and Wet cup) to test WVT of porous materials for practical application, without considering the influence of relative humidity and air flow. In this paper, multilayer method is used to test WVT of porous materials, without the influence of air flow on the whole testing process. Multilayer test method is the new way and there is little experience on how to conduct the whole process, how to obtain the accurate data and make the whole process reasonable is the big issue. Through several cases are worked on and analyzed, then renew desiccant every two hour which is depending on the type of porous materials, is the best way to make the whole testing system reaching to steady state for special building materials. At last, this paper shows that the new way is more reasonable and has higher accuracy than traditional method to get WVT.

Abstract: The research on water vapor isothermal sorption of porous building materials have an important function on controlling and solving hygrothermal problems, such as durability, thermal insulation, mold growth and indoor air quality, when building materials are in hygrothermal environment, especially in the high humidity environment. The isothermal sorption is used to describe the maximum moisture sorption capacity, if moisture content exceeds the limitation, probably there will be liquid water appearance, which lead to the risk of mold growth, decreasing durability and increasing thermal conductivity, and so on. The classic testing method of isothermal sorption could be found in ASTM Standards C 1498-01. In this paper, the eco-stucco, eco-fiber batt and eco-fiber board is tested using traditional method. Meanwhile, pore size distribution and capillary condensation is analyzed which is challenge for the design basis of hygrothermal character for the building envelope.