Modification of parts of autoclave equipment for founding liquid glass

Experience in restoring and strengthening the rapidly worn outer surface of the connection of the unit for discharging liquid glass from an autoclave by the method of spraying and surfacing is described. Introduction of the method substantially increased the capacity of the equipment.Translated from Steklo i Keramika, No. 12, p. 28, December, 1995.     

Technology of unfired periclase-spinel parts with a phosphate binder

Conclusions The method of production of periclase-spinel parts with a phosphate binder provides high physicotechnical properties in them and does not require high temperature firing.The unfired parts may be used for lining the burning zone of rotating cement and other industrial kilns.Translated from Ogneupory, No. 1, pp. 34–37, January, 1985.     

Dimensional study of thermoplastic parts made using sequential injection molding

As a result of new aesthetical and economical requirements in injection molding, several processes have been developed during last years. In spite of conventional process, sequential injection molding is a versatile technique based on independent control for each gate opening. This procedure allows part filling without weld lines or, at least, these defects can be relocated in suitable positions. A short discussion about sequential principles is made introducing computer simulations. Pressure required for part filling and molding shrinkage were evaluated using experimental procedures with a prototype mold and using conventional and sequential methods. Several setting up parameters were also used to analyze the effect on injection process. Final results show that shrinkage in sequential injection is similar to conventional process but some new effects could be induced by the process asymmetry and should be investigated further. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Glass ceramic coatings based on a fritless glass binder

The conditions and significant factors for preparing heat-resistant glass ceramic coatings for alloyed steels without using frit are considered. It was established that in order to obtain a glassy coating the radius of a particle characterizing the average dispersion of the system should not exceed 2.3 pin and the degree of polydispersion (the ratio of the maximum radius to the minimum one) should be 22. The use of water-insoluble charge ingredients and their calcination after the first crushing ensures complete sealing of shrinkage cracks.     

Abrasive tool made of silicon carbide micropowders on a ceramic binder

The processes that take place in silicon carbide microabrasive powders in firing of abrasives were examined and the effect of the granulometric composition of the powders on the properties of the articles were investigated. The possibility of obtaining articles of a given hardness using micropowders of different granulometric composition was demonstrated. __________ Translated from Steklo i Keramika, No. 8, pp. 33–35, August, 2007.     

Modified wheat gluten as a binder in particleboard made from reed

To evaluate the utilization of reed in environmental friendly high‐density particleboard, modified wheat gluten was used with urea‐formaldehyde as a binder in different ratios, applying the optimum conditions obtained on using UF resin alone. The scanning electron microscopy of the reed fibers showed that the fibers are cylindrical in shape, which helps in enhancing the adhesion between the binder and the inner and outer surfaces of the fibers. The dependence of the mechanical properties (modulus of rupture, modulus of elasticity and the internal bond) and the physical properties (water absorption and thickness swelling) on the urea‐formaldehyde/modified gluten ratios was studied. Addition of 1% and 2% boric acid as a fungicide to the binder mixture resulted in no significant change in the mechanical properties and slight improvement in the physical properties of the produced particleboard. Thermogravimetric analyses of selected samples were done to study the thermal stability of the particleboard bonded with the modified binder with and without boric acid. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Joining laser-sintered with injection-molded parts made of PA12 using infrared welding

Laser-sintering offers the possibility to produce complex and individualized components cost-effectively. To fully exploit the advantages of laser-sintering in assemblies with mass-produced components, high-performance joining processes like welding are necessary. Thus, a cost-effective customization of products can be enabled, which allows to follow the increasing trend of individualization. Infrared welding, in particular, can also be suitable for complex laser-sintered parts due to the reduced transverse forces during joining, compared to other welding processes. The investigations show that high strength between PA12 laser-sintered and injection-molded components can be achieved by infrared welding. The bond strength is mainly influenced by the welding parameters. Especially a low weld pressure leads to high achievable strengths and failure outside the weld seam. Joints between laser-sintered parts and glass fiber reinforced injection-molded components demonstrate the transferability of the obtained knowledge. The residual melt layer thickness of the joint decreases with increasing weld pressure, as the morphological characterization shows. Besides, the typical morphological seam structure can be seen on the side of the injection-molded component. In the area of the laser-sintered components, a deviating morphological structure can be observed. Distinctive flow lines can be observed, spherulitic structures can only partially be seen as well as deformed spherulites.     

Development of high-alumina ceramic concrete based on a composite binder

Information is provided for preparing high-alumina ceramic concretes based on a combined silicate-phosphate binder. Features are revealed for structure formation of the ceramic concrete developed during hardening, drying and firing; probable chemical reactions that occur are indicated.     

Novel glass-ceramic SOFC sealants from glass powders and a reactive silicone binder

The processing of sintered ceramics is often conditioned by the debinding step. The binders may determine some defects in the final product directly, by causing some gas evolution even at an advanced state of densification, due to incomplete decomposition at low temperature, or indirectly, by offering poor adhesion between particles, so that ‘green’ compacts may be easily damaged. The present investigation is aimed at exploring a novel concept for sintered glass-ceramics, based on the adoption of a silicone polymer as reacting binder, providing an abundant ceramic residue after firing. A glass belonging to the CaO-MgO-Al₂O₃-SiO₂ system, already studied as a sealant in solid oxide fuel cell (SOFC) planar stack design, was reproduced in form of ‘silica-defective’ variants, featuring a SiO₂ content, in the overall formulation, reduced up to 15?wt%. The overall silica content was recovered by mixing powders of the new glasses with the silicone: upon firing in air, the interaction between glass powders and polymer-derived silica led to glass-ceramics with the same phase assemblage than that formed by the reference glass and with a CTE of 9.5?×?10^?6 K^-1. The new approach has been successfully applied to the manufacturing of glass-ceramic seals as joining materials for solid oxide cells.     

Flexibility improvement of short glass fiber reinforced epoxy by using a liquid elastomer

In certain applications of fiber reinforced polymer composites flexibility is required. The aim of this study was to improve flexibility of short glass fiber reinforced epoxy composites by using a liquid elastomer. For this purpose, diglycidyl ether of bisphenol-A (DGEBA) based epoxy matrix was modified with hydroxyl terminated polybutadiene (HTPB). A silane coupling agent (SCA) was also used to improve the interfacial adhesion between glass fibers and epoxy matrix. During specimen preparation, hardener and HTPB were premixed and left at room temperature for an hour before mixing with epoxy resin to allow possible reactions to occur. In order to compare flexibility of the specimens flexural tests were conducted and the data were evaluated numerically by using a derived relation. Test data and scanning electron microscope analysis indicated that surface treatment of glass fibers with SCA, and HTPB modification of epoxy matrix improved flexural properties especially due to the strong interaction between fibers, epoxy, and rubber. It was also observed that HTPB modification resulted in formation of relatively round rubber domains in the epoxy matrix leading to increased flexibility of the specimens.     

Determination of activation temperature of glass bulb sprinklers using a thermal liquid bath

A thermal liquid bath was used to determine the activation temperature of a wide range of temperature rated (57–182°C) glass bulb (3 and 5 mm diameters) sprinklers using water and glycerine. An optical switch and a thermocouple were installed adjacent to each sprinkler (within 10 mm) to record the activation of each glass bulb in the liquid bath having a uniform temperature distribution (±0.5°C). All the tests for determining the activation temperatures of glass bulb sprinklers were conducted in the liquid bath using a 0.277°C/min rate of temperature rise. Based on a heat transfer analysis, this rate is within the maximum allowable rate of rise of water and glycerine temperatures, which allows the glass bulb temperature to closely follow the liquid temperature. The sprinkler activation temperature was evaluated in terms of percentage rating, which is expressed as the percent variation of the average activation temperature, as measured in the liquid bath, from the nominal rated temperature. Sprinklers (93°C rated or lower) activation temperatures in water were consistently within ±3.5% of rating. In glycerine, the activation temperatures of sprinklers rated between 93 and 182°C performed within 3.5% of their rating. Copyright © 2005 John Wiley & Sons, Ltd.     

Post-infiltration to improve the density of binder jetting ceramic parts

Infiltration of printed bodies with a ceramic suspension is a relevant approach to enhance density and properties of the porous binder-jetted parts. In the present work, significant improvements of alumina parts processed through this combination printing-infiltration was reported. The density of non-infiltrated (but sintered) samples only reached 55.3 ± 1.1% of the theoretical density while it raised up to 87.9 ± 0.5% after infiltration of a pre-consolidated body followed by sintering. Influence of multi-infiltration operations, pre-consolidation temperature, solids loading of suspensions and duration of infiltration on the final part density were discussed. Infiltration mechanism and porosity distribution have been carefully investigated. It was demonstrated that the ceramic suspension infiltrated the pre-consolidated ceramic skeleton mostly under the effect of gravity which may result in density heterogeneities of the infiltrated parts. The reported processing route can be straightforwardly applied to other ceramic systems and is particularly inexpensive, and it is believed to have industrial relevance.