Investigation of the effect of vacuum on the curing of mixtures on a silicate binder

The article presents the results of a study of the effect of vacuuming on the curing processes of liquid‑glass mixtures. The method of conducting experiments using an original laboratory vacuum installation and the mechanisms of curing a liquid‑glass mixture with various hardening methods are described. Studies have shown that vacuuming can signifi antly accelerate the curing and increase the strength of the mixture while reducing the content of the silicate binder. This; in turn; facilitates the knockability of liquid‑glass mixtures and expands the prospects for using these environmental friendly mixtures in foundry as an alternative to sands based on organic binders.

Using Jerusalem artichoke powder in functional food production

Introduction. Jerusalem artichoke is a valuable low-maintenance crop whose tubers contain vital nutrients and prebiotics. We propose using Jerusalem artichoke powder as a functional nutrient in the formulation of food products. Study objects and methods. We studied the influence of vacuum, vibration, and grinding on the kinetics of drying Jerusalem artichoke tubers of a “Skorospelka” variety in the laboratory vacuum vibromixing mill dryer (VVMD). Results and discussion. The rate of drying in the VVMD was almost 5.5 times as high as that of convective drying. The kinetic curves showed that grinding provided a period of decreasing drying rate until almost complete drying. Vibration drying in the VVMD was twice faster than vacuum drying. The comparison of theoretical and experimental data on moisture and drying time revealed good adequacy. The NMR analysis of changes in the molecular mobility of the samples obtained in the VVMD showed an implicit twocomponent spectrum, indicative of low moisture. The chemical analysis of the tubers and powders by standard methods confirmed that the proposed gentle technology (fast drying at 30°C) preserved 86% of inulin. Conclusion. Jerusalem artichoke powder obtained in the VVMD can be used in different branches of the food industry due to its long shelf life, low consolidation, and no caking, with residual moisture of 6.1%.

Optimization of the Mixing Ratio of Two Different Clays Used for Ceramic Roof Tiles

Brick- and tile manufacturing is one of the most rapidly developing industries. Professionals are constantly seeking modern technological solutions with which much better and longer lifetime of ceramic roof tiles can be reached. The aim of this R&D work was to optimize the mixing ratio of two different clay minerals of the industrial partner. The Authors have tried to develop a mixture by increasing the mixing ratio of the clay „Jamina”, which reaches or exceeds the mechanical strength and frost-resistance of the ceramic roof tiles which were made according to the present recipe used by the industrial partner. After XRD tests in virtue of preliminary mixture design, the Authors have made clay mineral mixtures that were milled and homogenized in an edge mill for an appropriate grain size. After mixing and homogenizing, samples with different length were made for further investigations with the use of a laboratory vacuum extrusion system. Shrinkage after drying and firing, apparent porosity and water absorption were measured on these samples. Mechanical test were also executed, as well as bending strength tests and compressive strength tests. On the basis of the results of the executed tests, it can be seen that the Authors were successfully developed clay mixtures, with which ceramic roof tiles can be produced with properties that are more favourable than the present mixture used by the industrial partner. The increase of the ratio of ‘Csaba I.’ clay increases the bending and compressive strength of the fired ceramic roof tiles. So the reduction of the amount of clay „Jamina” affects the mechanical properties of the ceramic roof tiles favourably.

High Vacuum Brazing of Fe-Cr-Al-Y Honeycomb

M-Cr-Al-Y and in particular Fe-Cr-Al-Y alloys with high aluminium matrix content have a tendency to form thin, stable and tightly adherent alumina scales even at low oxygen partial pressures. This forms the basis of their superior hot gas oxidation, carburization and sulfidation resistance when used at high temperatures. However, the same tendency makes the alloys more difficult to braze because the easily formed and highly stable ceramic surface layers significantly reduce wettability and hence braze flow. Fe-Cr-Al-Y alloys have recently been suggested as promising alloys for use in gas turbine engines as abradable honeycomb gas path seals. This paper reviews the vacuum brazing of honeycombs made from highly alloyed Fe-Cr-Al-Y foils to metal backing members. Most suitable Fe-Cr-Al-Y materials, commercial braze filler alloys and braze cycles are presented. Emphasis is placed on industrial equipment rather than laboratory vacuum furnaces. Brazing under high vacuum conditions in all-metal furnaces is recommended as a brazing procedure for honeycomb made from MI 2100, which is high in aluminium content, to various commonly used carrier structure alloys.