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Influence of the Compacts Homogeneity on the Incidence of Cracks during Thermal Debinding in Ceramic Injection Molding

Xianfeng Yang,Zhipeng Xie,Yong Huang,

材料科学技术学报 , 2009,
Abstract: During thermal debinding in ceramic injection molding, the inhomogeneity of green body is a key origin of cracks. In this study, the impact of low molecular weight binders on the homogeneity of the green body was investigated. Incidence of cracks during thermal debinding indicated that the volume ratio of wax to stearic acid should be out of high viscosity and incompletely wetting region. In these two formulation regions,typical inhomogeneous microstructures were observed. By mercury intrusion method, it was shown that pore size distribution of the debinded compacts was determined by thermal degradation of low molecular weight binders. A particle-rich region model was established to predict the nucleation of cracks caused by solid loading fluctuation. The criterion of cracks nucleation was that local capillary force from solid loading fluctuation was larger than the suction force from the surroundings.
Analysis and modeling of sintering of Sr-hexaferrite produced by PIM technology  [PDF]
Zlatkov B.S.,Nikolic M.V.,Zeljkovic V.,Obradovic N.
Science of Sintering , 2011, DOI: 10.2298/sos1101009z
Abstract: The powder injection moulding (PIM) technology is lately becoming more and more significant due to complex design possibilities and good repeatability. This technology requires optimization of all steps starting with material and binder, injection, debinding and sintering parameters. Sintering is one of the key links in this technology. The powder injection moulding process is specific as during feedstock injection powder particles mixed into the binder do not come into mechanical contact. Shrinkage during sintering of PIM samples is high. In this work we have analyzed and modeled the sintering process of isotropic PIM samples of Sr-hexaferrite. The Master Sintering Curve (MSC) principle has been applied to analyze sintering of two types of PIM Sr-hexaferrite samples with completely removed binder and only the extraction step of the debinding procedure (thermal debinding proceeding simultaneously with sintering). Influence of the heating rate on resulting sample microstructures has also been analyzed. Influence of the sintering time and temperature was analyzed using three different phenomenological equations.
An internal topological characterization of the subspaces of Eberlein compacts and related compacts -- I  [PDF]
Georgi D. Dimov
Mathematics , 2012,
Abstract: We obtain an internal topological characterization of the subspaces of Eberlein compacts (respectively, Corson compacts, strong Eberlein compacts, uniform Eberlein compacts, $n$-uniform Eberlein compacts).
Recent advances in PIM technology I  [PDF]
Zlatkov B.S.,Griesmayer E.,Loibl H.,Aleksi? O.S.
Science of Sintering , 2008, DOI: 10.2298/sos0801079z
Abstract: In this article the state of art of the PIM (Powder Injection Moulding) technology is given in brief. The main process flow diagram consisting of four steps: feedstock preparation, injection moulding (green samples forming), the debinding (binder removing) procedure and the sintering process was described. After that the materials for binders and additives for the surface active agents were mentioned in brief. The metal injection moulding (MIM) process was analysed in more detail: MIM- stainless steels, MIM-copper and MIM-aluminium as the most metals common in MIM metal parts production. After that our results of MIM stainless steel 316 L and MIM copper are given. The main powder characteristics, the shrinkage and density of the sintered samples were compared for isostatically pressed PM (powder metallurgy) samples and MIM formed samples. The SEM fractographs of MIM and PM samples are given for MIM green parts, debinded (brown) parts and sintered parts, and PM green parts and sintered parts. The results obtained were compared with literature data before they were applied in metal parts production.
Flowability in crushed sand mortar
Cabrera, O. A.,Traversa, L. P.,Ortega, N. F.
Materiales de Construccion , 2010,
Abstract: The present experimental study explored the relationship between mortar flowability and the voids content in crushed sand to determine the effect of grain shape and surface texture as well as dust content on the behaviour of fresh mortar. The findings revealed a close correlation between voids content and the volume of paste needed for mortar to begin to flow as a continuous material, mortar flowability and the water content needed to attain a given flowability. The comparison of the empirical findings to the results obtained with the Larrard (1, 2) model provided further information on the effect of sand grain morphology on fresh mortars. En el presente trabajo se plantea un estudio experimental de la fluidez de morteros basado en el contenido de vacíos de arenas machacadas, para comprender la influencia de la forma y textura superficial de los granos de arena y del contenido de polvo de las mismas sobre el estado fresco de morteros. Los resultados muestran la estrecha relación entre el contenido de vacíos entre granos y los volúmenes de pasta necesarios para iniciar el escurrimiento como un material continuo, la fluidez de los morteros, el contenido de agua para alcanzar una determinada fluidez, etc. El comportamiento evaluado se compara con resultados obtenidos aplicando el modelo de F. de Larrard (1, 2), permitiendo de este modo obtener mayor información de la influencia de la morfología de los granos de la arena sobre el estado fresco de los morteros.
Plasma debinding and pre-sintering of injected parts
Santos, Maria Ant?nia dos;Neivock, Matheus Piazzalunga;Maliska, Ana Maria;Klein, Aloísio Nelmo;Muzart, Joel Louis Rene;
Materials Research , 2004, DOI: 10.1590/S1516-14392004000300021
Abstract: results of polypropylene removal in injected metallic parts by using plasma technology are presented. the samples were injected with 55.18% vol. of unalloyed iron powder, 23.57% vol. of paraffin and 21.25% vol. of polypropylene. the paraffin was previously removed in hexane bath, followed by a treatment in abnormal glow discharge of argon and hydrogen for the removal of the polypropylene. the electric discharge was generated in two configurations: a confined anode-cathode with the samples placed on the anode and a confined grid (anode)-cathode system with the sample placed on a holder at floating potential inside the grid. in the first geometry, electrons bombarded the sample surface, while in the second, they are collected by the grid. the samples were characterized by mass loss measurements and scanning electron microscopy. the results showed that the hydrogen discharge was more efficient for both configurations, which is attributed to the high reactivity of hydrogen atoms produced in the discharge. in addition, when plasma debinding was performed at 400 oc for 10 min, by using the confined anode-cathode configuration, the polypropylene removal was total, while in the confined grid (anode)-cathode geometry the removal was approximately 32%. the higher polypropylene removing observed in the anode-cathode configuration is attributed to electron bombardment of the surface of the sample.
Plasma debinding and pre-sintering of injected parts
Santos Maria Ant?nia dos,Neivock Matheus Piazzalunga,Maliska Ana Maria,Klein Aloísio Nelmo
Materials Research , 2004,
Abstract: Results of polypropylene removal in injected metallic parts by using plasma technology are presented. The samples were injected with 55.18% Vol. of unalloyed iron powder, 23.57% Vol. of paraffin and 21.25% Vol. of polypropylene. The paraffin was previously removed in hexane bath, followed by a treatment in abnormal glow discharge of argon and hydrogen for the removal of the polypropylene. The electric discharge was generated in two configurations: a confined anode-cathode with the samples placed on the anode and a confined grid (anode)-cathode system with the sample placed on a holder at floating potential inside the grid. In the first geometry, electrons bombarded the sample surface, while in the second, they are collected by the grid. The samples were characterized by mass loss measurements and scanning electron microscopy. The results showed that the hydrogen discharge was more efficient for both configurations, which is attributed to the high reactivity of hydrogen atoms produced in the discharge. In addition, when plasma debinding was performed at 400 oC for 10 min, by using the confined anode-cathode configuration, the polypropylene removal was total, while in the confined grid (anode)-cathode geometry the removal was approximately 32%. The higher polypropylene removing observed in the anode-cathode configuration is attributed to electron bombardment of the surface of the sample.
CIM to PIM Transformation: An Analytical Survey
Hamid Reza Sharifi,Mehran Mohsenzadeh,Seyyed Mohsen Hashemi
International Journal of Computer Technology and Applications , 2012,
Abstract: Model transformation is one of the main issues and key elements in Model Driven Architecture (MDA). Computation Independent Model (CIM) to Platform Independent Model (PIM) transformation is the first transformation in MDA and it is very important in designing high quality software. Several CIM to PIM transformation approaches have emerged, they have not been objectively analysed yet. In this paper, we provide a review of several CIM to PIM transformation approaches, and present a criteria-based evaluation. The results can be used for assessing and comparing CIM to PIM transformation approaches.
Regularity of operators on essential extensions of the compacts  [PDF]
Arupkumar Pal
Mathematics , 1999,
Abstract: A semiregular operator on a Hilbert C^*-module, or equivalently, on the C^*-algebra of `compact' operators on it, is a closable densely defined operator whose adjoint is also densely defined. It is shown that for operators on extensions of compacts by unital or abelian C^*-algebras, semiregularity leads to regularity. Two examples coming from quantum groups are discussed.
A Review on Liquid Solid Compacts  [PDF]
V.N.L. Sirisha,B. Sruthi,M. Namrata,I. Bhavani Harika
International Journal of Pharmaceutical and Phytopharmacological Research , 2012,
Abstract: At present 40% of the drugs in the development pipelines, and approximately 60% of the drugs coming directly from synthesis are poorly soluble. The limited solubility of drugs is a challenging issue for industry, during the development of the ideal solid dosage form unit. Liqui-solid compacts technique is a new and promising approach to overcome this consequence and that can change the dissolution rate of water insoluble drugs and increase the bioavailability of the drugs. According to the new formulation method of liqui-solid compacts, liquid medications such as solutions or suspensions of water insoluble drugs in suitable nonvolatile liquid vehicles can be converted into acceptably flowing and compressible powders by blending with selected powder excipients. It has been speculated that such systems exhibit enhanced release profiles. In this case, even though the drug is in a solid dosage form, it is held within the powder substratin solution or, in a solubilized, almost molecularly dispersed state, which contributes to the enhanced drug dissolution properties.
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