Shaping the Microstructure of High-Aluminum Cast Iron in Terms of the Phenomenon of Spontaneous Decomposition Generated by the Presence of Aluminum Carbide

A suitable aluminum additive in cast iron makes it resistant to heat in a variety of environments and increases the abrasion resistance of the cast iron. It should be noted that high-aluminum cast iron has the potential to become an important eco-material. The basic elements from which it is made—iron, aluminum and a small amount of carbon—are inexpensive components. This material can be made from contaminated aluminum scrap, which is increasingly found in metallurgical scrap. The idea is to produce iron castings with the highest possible proportion of aluminum. Such castings are heat-resistant and have good abrasive properties. The only problem to be solved is to prevent the activation of the phenomenon of spontaneous decomposition. This phenomenon is related to the Al4C3 hygroscopic aluminum carbide present in the structure of cast iron. Previous attempts to determine the causes of spontaneous disintegration by various researchers do not describe them comprehensively. In this article, the mechanism of the spontaneous disintegration of high-aluminum cast iron castings is defined. The main factor is the large relative geometric dimensions of Al4C3 carbide. In addition, methods for counteracting the phenomenon of spontaneous decay are developed, which is the main goal of the research. It is found that a reduction in the size of the Al4C3 carbide or its removal lead to the disappearance of the self-disintegration effect of high-aluminum cast iron. For this purpose, an increased cooling rate of the casting is used, as well as the addition of elements (Ti, B and Bi) to cast iron, supported in some cases by heat treatment. The tests are conducted on the cast iron with the addition of 34–36% mass aluminum. The molten metal is superheated to 1540 °C and then the cast iron samples are cast at 1420 °C. A molding sand with bentonite is used to produce casting molds.

Abrasion Behaviour of Different Charcoal Toothpastes When Using Electric Toothbrushes

Objectives: The purpose of this in vitro study was to compare the abrasion behaviour of different charcoal toothpastes when brushing with electric toothbrushes on human enamel. Materials and Methods: A self-designed brushing machine was built using six commercially available electric toothbrushes in abrasion chambers. Each chamber was constantly supplied with a toothpaste–water mix. Pieces of human enamel, which were embedded in PMMA, were brushed for 4 h. Before and after brushing, profilometer measurements were performed in order to determine the substance loss due to brushing. Results: The following calculated mean removal values (mean ± SD) were found: (4.6 ± 0.6) µm (Group C: Splat Blackwood), (3.2 ± 0.9) µm (Group D: Curaprox Black is White), (2.3 ± 0.7) µm (Group B: Sensodyne Pro Schmelz), (1.7 ± 0.6) µm (Group A: Water), (1.4 ± 0.6) µm (Group E: Prokudent Black Brilliant). A post hoc Tukey HSD test (p = 0.05) showed that the results for Group A/B/E, Group B/D and Group C each lie within subsets that differ statistically significantly from the other subsets. Conclusions: Within the limitations of this in vitro study, it can be stated that some charcoal toothpastes lead to significantly higher abrasion on human enamel, when brushing with electric brushes. Clinical Relevance: As low-abrasion toothpaste is generally advisable, and some charcoal toothpastes should be viewed critically with regard to their abrasive properties.

Improvement of the extruder body design in order to increase reliability and quality of extrusion

The article highlights one of the ways to improve the design of the extruder body in order to increase the reliability and, at the same time, the quality of extrusion. The object of research is a single-worm extruder. One of the most problematic areas of the extruder is the body. The main disadvantage of the extruder is the wear of the body surfaces due to corrosion or abrasion and requires regular replacement. This is due to the abrasive properties of the polymers and, accordingly, due to the friction of the polymer material against the body and the worm, especially due to contamination in the recycled material. In various sources, the replacement of the extruder worm with a more advanced design is widely covered. And scientists do not pay enough attention to improving the body of the extruder, which indicates the relevance of this study. That is why the problem of increasing the reliability of the extruder body is completely unsolved and urgent. In the course of the study, we used an analysis of the structural features of the extruder body, a literature-patent review of existing methods for improving the body of a single-worm extruder to increase the reliability and, at the same time, the quality of extrusion. As a result of the literature and patent review, the option of improving the extruder body based on the prototype of the split body, which additionally contains an inner surface of steel ribbed plates, was selected. It was found that the ribbing of the plates on the inner surface of the body increases the wear resistance of the body and promotes more intensive advancement of the polymer used material to the extruder head. This is due to the fact that the proposed improved body of the extruder has a number of features: steel ribbed plates rigidly fixed inside it are installed with overlap of the parting line of the extruder body. This makes it possible to increase the wear resistance and, accordingly, the reliability of the extruder body and, additionally, the extrusion quality. Compared with the known one-piece structures of the extruder body, the design of the body is detachable with steel rigidly mounted ribbed plates on the inner surface, which will simplify maintenance during repairs and, at the same time, improve the quality of extrusion.

EVALUATION OF WALNUT SHELL ABRASIVE SANDPAPER

This study is focused on development of an eco-friendly abrasive sandpaper using walnut shell (WS) with the binding effect of epoxy resin on WS, iron oxide and silica, calcium carbonate (CaCO3) and pulverized graphite. The method of mixing and mould compression using a hydraulic press matrix composite with five varying composition was used. The compositions were made by varying the weight of WS, epoxy resin with that of iron oxide and silica, calcium carbonate and pulverized graphite were left constant expressed in percentage weight The abrasive properties investigated were density, compressive strength and wear resistance and water and oil absorption rate. The results reveals obtained that the density, wear resistance rate and compressive strength of the tested composition decreases with increasing WS content despite the fact the rate water absorption increases with increasing WS. The result of obtained reveals that WS can be utilized in the production of abrasive sandpaper

The science system on-board the Emirates Lunar Mission's Rashid rover

<p>The Emirates Lunar Mission is developing the small and light weight "Rashid" rover. The goals for this rover are to traverse several hundred meters on the lunar surface during the course of one lunar day. The Rashid rover's science objectives cover both fundamental science as well as engineering topics with the goal to enable future missions to the lunar surface, and other airless solar system bodies. Hence, Rashid will carry a suite of scientific instruments and an experiment, covering a wide range of the physical properties at the lunar surface. The focus of investigation for the microscopic imager (CAM-M) will be to measure the regolith particle size distribution, and the lunar surface structure at microscopic scales. The Langmuir probe system (LNG) will address  the  electron density profile of the sheath, its behavior over the course of the lunar day, and its dependence on topographic features.  A thermal imager (CAM-T) with low spatial resolution is also foreseen. Finally, the in-situ testing of the adhesive and abrasive properties of various materials to lunar regolith is planned to be conducted by the MAD experiment.  In this paper the science program and instrumentation of the Rashid mission will be outlined. </p>

Strength and abrasive properties of andesite: relationships between strength parameters measured on cylindrical test specimens and micro-Deval values—a tool for durability assessment

Aggregates are necessary materials for the construction industry. Owing to their favourable properties, andesites are frequently used rock materials; hence, the investigation of their mechanical and aggregate properties has great significance. This paper introduces the analyses of 13 Hungarian andesite lithotypes. The samples were collected from six andesite quarries in Hungary. Cylindrical specimens and aggregate samples with 10.0/14.0-mm-sized grains were made from rock blocks. The specimens were tested in dry, water-saturated and freeze–thaw subjected conditions. Bulk density, uniaxial compressive strength, modulus of elasticity, indirect tensile strength and water absorption were measured. The abrasion resistance was tested by micro-Deval tests. The flakiness indexes of the samples were also measured. The data set of the laboratory test results provided input for further, one- and two-variable statistical analyses. According to the test results, there is no significant difference between the strength parameters measured in water-saturated and in freeze–thaw subjected conditions. The correlation and regression analyses revealed relationships between some rock mechanical parameters, as well as between micro-Deval coefficient and uniaxial compressive strength.