Effect of Heat Treatment on Structural and Mechanical Properties of Alloyed Fused Alumina

Heat treatment of ceramic-bond grinding tools during manufacture takes place at temperature of abrasive grains up to 1250 °C, which results in variation of their phase composition, structure, and strength. Similar phenomena may take place during grinding caused by the occurring high-temperature processes. It primarily pertains to alloyed fused alumina. X-ray and topography testing, as well as studying of micromechanical properties made it clear that structural performance, material strength, and fracture pattern of single grains of Ti-containing fused alumina affected by temperature depend on the type and ratio of alloy additives in alumina and on the decomposition level of the Ti2O3 solid solution. In terms of aggregate properties, purple varieties of Cr-Ti fused alumina featuring the minimum TiO2/Cr2O3 ratio of 1.5 in the solid solution after heat treatment are preferable.

Development of Technology Ferrous Metal Melting Furnace Ancient Times in Indonesia

Technological knowledge of the use of metals is inseparable from human knowledge in the processing pyrotechnics of fire as a power in high temperature processes for producing objects. The fire is used for smelting and casting in melting furnaces. Metal smelting furnace is a heat production device, which is used to purify the metal, in this case iron. This paper aims to determine the development of ferrous metal smelting furnace technology in Indonesia with the library research method from the results of previous studies. Based on the results of the analysis, there are four technologies for smelting iron, namely pit kiln, bloomery furnace, blast furnace, and induction furnace. Of the four technologies, three are in use in Indonesia, namely bloomery furnace, blast furnace, and induction furnace.

Effect of Content and Size of Reinforcements on the Grain Evolution of Graphene-Reinforced Aluminum Matrix Composites

Graphene-reinforced aluminum matrix composites (GRAMCs) attract great interest in industries due to their high performance potential. High-temperature processes such as sintering and aging are usually applied during the preparation of GRAMCs, leading to grain coarsening that significantly influences its properties. In this work, a modified 3D Monte Carlo Potts model was proposed to investigate the effect of content and size of graphene on the grain evolution during the heat treatment of GRAMCs. Grain growth with graphene contents from 0.5 wt.% to 4.5 wt.% and sizes from 5 μm to 15 μm were simulated. The grain growth process, final grain size and morphology of the microstructure were predicted. The results indicated that both the content and size of the reinforcements had an impact on the grain evolution. The pinning effect of grain size can be enhanced by increasing the content and decreasing the size of graphene. Agglomeration and self-contacting phenomena of the graphene arose obviously when the contents and sizes were relatively high. The average grain size decreased by 48.77% when the content increased from 0.5 wt.% to 4.5 wt.%. The proposed method and predicted regulations can provide a reference for the design and fabrication of GRAMCs.

Behaviour of Microwave-Heated Al4SiC4 at 2.45 GHz

The ongoing development of high-temperature processes with the use of microwaves requires new microwave absorbers that are useful at these temperatures. In this study, we propose Al4SiC4 powders as important and efficient microwave absorbers. We investigated both the behavioural microwave heating and electrical permittivity characteristics of Al4SiC4 powders with various particle sizes at 2.45 GHz. The TE103 single-mode cavity indicated that Al4SiC4 powder samples yielded different heating behaviours and dielectric constants for each particle size compared with SiC. By microwave heating ∅50 mm × 5 mm disks of Al4SiC4 and SiC, we demonstrate that for specific sizes, Al4SiC4 can be heated at a higher temperature than SiC. Finally, the results of the two-dimensional two-colour thermometer show that an energy concentration appears at the interface of the microwave-heated Al4SiC4. These phenomena, which are inconsistent in individual physical property values, can be explained without contradicting microwave heating physics.

Effect of the combustion system on reduction of thermal specific energy consumption in an industrial high temperature process

This paper presents an experimental study carried out in an industrial furnace for frits production using different configurations of burners based on different combustion techniques such as enriched air combustion, flat-flame oxy-combustion and preheater air combustion. The residence time of combustion gases inside the furnace also was modified. Several combustion configurations were tested and its effects on productivity and thermal energy specific consumption and efficiency were determined. The results show that higher residence time of the combustion gases can decrease significantly the specific consumption of fuel, while the change of the burners and combustion techniques did not show significant effects on decreasing the energy consumption. However, it is highlighted that the oxy-combustion flat-flame burners produced the lowest specific consumption of fuel. Even though the experiments were conducted in a furnace for frit production, the corresponding results can also be applied to guide or improve other industrial high temperature processes.

Special effect pigments

Special effect pigments are in the very most cases synthetic pigments, characterized by high luster, brilliance and iridescent colors known from optically thin films. The visual appearance has its origin in reflection and refraction of light at thin single and multiple layers. The pigments are either transparent, semitransparent or light-absorbing platelet-shaped crystals or layer systems. They can consist of single crystals, but also of monolayer or a multilayer structures in which the layers have different refractive indices and light absorption properties. Pigment based on the layer-substrate principle represent the technically most important class of special effect pigments. There are many variation and combination possibilities for the layer and substrate materials used. Special effect pigments based on platelets of natural or synthetic mica, on alumina, silica, or borosilicate flakes are the main representatives of layer-substrate pigments. They are manufactured in most cases by wet chemical processes combined with high-temperature processes. The production of substrate particles includes mechanical processes, but also crystal growth, glass formation, and web coating.

Fiber Bragg Grating Wavelength Drift in Long-Term High Temperature Annealing

High-temperature-resistant fiber Bragg gratings (FBGs) are the main competitors to thermocouples as sensors in applications for high temperature environments defined as being in the 600–1200 °C temperature range. Due to their small size, capacity to be multiplexed into high density distributed sensor arrays and survivability in extreme ambient temperatures, they could provide the essential sensing support that is needed in high temperature processes. While capable of providing reliable sensing information in the short term, their long-term functionality is affected by the drift of the characteristic Bragg wavelength or resonance that is used to derive the temperature. A number of physical processes have been proposed as the cause of the high temperature wavelength drift but there is yet no credible description of this process. In this paper we review the literature related to the long-term wavelength drift of FBGs at high temperature and provide our recent results of more than 4000 h of high temperature testing in the 900–1000 °C range. We identify the major components of the high temperature wavelength drift and we propose mechanisms that could be causing them.