Sintered transparent polycrystalline ceramics: the next generation of fillers for clarity enhancement in corundum

A significant proportion of mined natural corundum (ruby and sapphire) contain fractures, which negatively affects a gemstone’s clarity and value. Over the past decades, heat treatment techniques have been developed for either fracture healing, or filling to make such gems marketable. The clarity enhancement processes are mainly based on techniques which are either not durable, as in the case of lead silicate fillers, or do not yield perfect transmittance through a fracture, as in the case of borax based fluxes. Therefore, the gemstone treatment community is actively in pursuit of better techniques for clarity enhancement in corundum. Given that application of pressure is a recent advancement in the heat treatment processes of natural sapphire, it is essential to explore the possibilities regarding different outcomes such treatments can have. In this perspective paper, we have briefly described how application of pressure during heat treatments can lead to in-situ sintering of transparent polycrystalline ceramics within the fractures of corundum, which can result in clarity enhancement. Spinel-structure based fillers can be tailored to mimic corundum in terms of tribological, chemical and optical properties. Therefore, gemstones treated with such fillers will be durable, unlike currently used glass-based filler material. We also provide a possible explanation for ghost-fissures in sapphires heated under pressure, as being a by-product of in-situ sintering process of ceramic fillers that are thermodynamically compatible with Al2O3. The prospect of transparent polycrystalline ceramics in the gem and jewelry industry opens a new field of research in this area, given that ceramic fillers can outperform currently used methods and material for clarity enhancement in gemstones. In essence, we present a novel application for sintered transparent polycrystalline ceramics.

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INFLUENCE THE QUENCHING AND TEMPERING ON THE MICROSTRUCTURE, MECHANICAL PROPERTIES AND SURFACE ROUGHNESS, OF MEDIUM CARBON STEEL

THE IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING ◽

10.32852/iqjfmme.vol18.iss1.78 ◽

2018 ◽

Vol 18 (1) ◽

pp. 125-135

Author(s):

Sattar H A Alfatlawi

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Surface Roughness ◽

Carbon Steel ◽

Cold Water ◽

Medium Carbon Steel ◽

Medium Carbon ◽

Heating And Cooling ◽

Treatment Processes ◽

Quenching And Tempering

One of ways to improve properties of materials without changing the product shape toobtain the desired engineering applications is heating and cooling under effect of controlledsequence of heat treatment. The main aim of this study was to investigate the effect ofheating and cooling on the surface roughness, microstructure and some selected propertiessuch as the hardness and impact strength of Medium Carbon Steel which treated at differenttypes of heat treatment processes. Heat treatment achieved in this work was respectively,heating, quenching and tempering. The specimens were heated to 850°C and left for 45minutes inside the furnace as a holding time at that temperature, then quenching process wasperformed in four types of quenching media (still air, cold water (2°C), oil and polymersolution), respectively. Thereafter, the samples were tempered at 200°C, 400°C, and 600°Cwith one hour as a soaking time for each temperature, then were all cooled by still air. Whenthe heat treatment process was completed, the surface roughness, hardness, impact strengthand microstructure tests were performed. The results showed a change and clearimprovement of surface roughness, mechanical properties and microstructure afterquenching was achieved, as well as the change that took place due to the increasingtoughness and ductility by reducing of brittleness of samples.

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Determination of Optimum Post Weld Heat Treatment Processes on the Microstructure and Mechanical Properties of IS2062 Steel Weldments

i-manager s Journal on Material Science ◽

10.26634/jms.3.3.3670 ◽

2015 ◽

Vol 3 (3) ◽

pp. 7-12

Author(s):

M. Bala Chennaiah ◽

◽

P. Nanda Kumar ◽

K. Prahlada Rao ◽

◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Post Weld Heat Treatment ◽

Treatment Processes ◽

Microstructure And Mechanical Properties ◽

Weld Heat

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Effect of Two-step Heat Treatment Processes on the Formation of Protein Particles and Oil Droplets in Soymilk

Food Science and Technology Research ◽

10.3136/fstr.26.445 ◽

2020 ◽

Vol 26 (3) ◽

pp. 445-450

Author(s):

Makoto Shimoyamada ◽

Hironori Shikano ◽

Shingo Mogami ◽

Makoto Kanauchi ◽

Hayato Masuda ◽

...

Keyword(s):

Heat Treatment ◽

Oil Droplets ◽

Treatment Processes ◽

Protein Particles ◽

Step Heat Treatment

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EFFECT ON HARDNESS and MICRO STRUCTURAL BEHAVIOUR OF TOOL STEEL AFTER HEAT TREATMENT PROCESS

Scholarly Research Journal for Humanity Science & English Language ◽

10.21922/srjhsel.v4i24.10426 ◽

2017 ◽

Vol 4 (24) ◽

Author(s):

Karanbir Singh ◽

Aditya Chhabra ◽

Vaibhav Kapoor ◽

Vaibhav Kapoor

Keyword(s):

Heat Treatment ◽

Empirical Study ◽

Tool Steel ◽

Treatment Process ◽

Heat Treatment Process ◽

Structural Behaviour ◽

Treatment Processes ◽

En 31

This study is conducted to analyze the effect on the Hardness and Micro Structural Behaviour of three Sample Grades of Tool Steel i.e. EN-31, EN-8, and D3 after Heat Treatment Processes Such As Annealing, Normalizing, and Hardening and Tempering. The purpose of Selecting Tool Steel is Because Tool Steel is Mostly Used in the Manufacturing Industry.This study is based upon the empirical study which means it is derived from experiment and observation rather than theory.

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Rock Surface Fungi in Deep Continental Biosphere—Exploration of Microbial Community Formation with Subsurface In Situ Biofilm Trap

Microorganisms ◽

10.3390/microorganisms9010064 ◽

2020 ◽

Vol 9 (1) ◽

pp. 64

Author(s):

Maija Nuppunen-Puputti ◽

Riikka Kietäväinen ◽

Lotta Purkamo ◽

Pauliina Rajala ◽

Merja Itävaara ◽

...

Keyword(s):

Significant Proportion ◽

Debaryomyces Hansenii ◽

Fungal Communities ◽

Fungal Colonization ◽

Rock Surface ◽

Mica Schist ◽

Deep Subsurface ◽

Bacterial Phyla ◽

In Situ Conditions

Fungi have an important role in nutrient cycling in most ecosystems on Earth, yet their ecology and functionality in deep continental subsurface remain unknown. Here, we report the first observations of active fungal colonization of mica schist in the deep continental biosphere and the ability of deep subsurface fungi to attach to rock surfaces under in situ conditions in groundwater at 500 and 967 m depth in Precambrian bedrock. We present an in situ subsurface biofilm trap, designed to reveal sessile microbial communities on rock surface in deep continental groundwater, using Outokumpu Deep Drill Hole, in eastern Finland, as a test site. The observed fungal phyla in Outokumpu subsurface were Basidiomycota, Ascomycota, and Mortierellomycota. In addition, significant proportion of the community represented unclassified Fungi. Sessile fungal communities on mica schist surfaces differed from the planktic fungal communities. The main bacterial phyla were Firmicutes, Proteobacteria, and Actinobacteriota. Biofilm formation on rock surfaces is a slow process and our results indicate that fungal and bacterial communities dominate the early surface attachment process, when pristine mineral surfaces are exposed to deep subsurface ecosystems. Various fungi showed statistically significant cross-kingdom correlation with both thiosulfate and sulfate reducing bacteria, e.g., SRB2 with fungi Debaryomyces hansenii.

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Experimental Investigation of Laser Sintering of Conductive Adhesive for Functional Prototypes Produced by Embedding Stereolithography

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1038.75 ◽

2014 ◽

Vol 1038 ◽

pp. 75-81

Author(s):

Bernd Niese ◽

Philipp Amend ◽

Uwe Urmoneit ◽

Stephan Roth ◽

Michael Schmidt

Keyword(s):

Thermal Damage ◽

Laser Sintering ◽

Conductive Adhesive ◽

Flexible Production ◽

Sintering Process ◽

Building Process ◽

In Situ Generation ◽

Functional Components

Embedding stereolithography (eSLA) is an additive, hybrid process, which provides a flexible production of 3D components and the ability to integrate electrical and optical conductive structures and functional components within parts. However, the embedding of conductive circuits in stereolithography (SLA) parts assumes usage of process technologies, which enables their direct integration of conductive circuits during the layer-wise building process. In this context, a promising method for in-situ generation of conductive circuits is dispensing of conductive adhesive on the current surface of the SLA part and its subsequent sintering. In this paper, the laser sintering (λ = 355 nm) of conductive adhesive mainly consisting of silver nanoparticles is investigated. The work intends to evaluate the curing behavior of the conductive adhesive, the beam-matter-interactions and the thermal damage of the SLA substrate. The investigations revealed a fast and flexible laser sintering process for the generation of conductive circuits with sufficient electrical conductivity and sufficient current capacity load. In this context, a characterization of the conductive structures is done by measuring their electrical resistance and their potential current capacity load.

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