scholarly journals Reproduction of melting behavior for vitrified hillforts based on amphibolite, granite, and basalt lithologies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
John S. McCloy ◽  
José Marcial ◽  
Jack S. Clarke ◽  
Mostafa Ahmadzadeh ◽  
John A. Wolff ◽  
...  
Keyword(s):  
Iron Age ◽  
Glass Production ◽  
Melting Behavior ◽  
Source Rocks ◽  
Ex Situ ◽  
Maximum Temperature ◽  
Heating And Cooling ◽  
Heat Treated ◽  
Granitoid Rocks ◽  
Dark Glass

AbstractEuropean Bronze and Iron Age vitrified hillforts have been known since the 1700s, but archaeological interpretations regarding their function and use are still debated. We carried out a series of experiments to constrain conditions that led to the vitrification of the inner wall rocks in the hillfort at Broborg, Sweden. Potential source rocks were collected locally and heat treated in the laboratory, varying maximum temperature, cooling rate, and starting particle size. Crystalline and amorphous phases were quantified using X-ray diffraction both in situ, during heating and cooling, and ex situ, after heating and quenching. Textures, phases, and glass compositions obtained were compared with those for rock samples from the vitrified part of the wall, as well as with equilibrium crystallization calculations. ‘Dark glass’ and its associated minerals formed from amphibolite or dolerite rocks melted at 1000–1200 °C under reducing atmosphere then slow cooled. ‘Clear glass’ formed from non-equilibrium partial melting of feldspar in granitoid rocks. This study aids archaeological forensic investigation of vitrified hillforts and interpretation of source rock material by mapping mineralogical changes and glass production under various heating conditions.

scholarly journals Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N System

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3963
Author(s):  
Marius Holger Wetzel ◽  
Tina Trixy Rabending ◽  
Martin Friák ◽  
Monika Všianská ◽  
Mojmír Šob ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Equilibria ◽  
Phase Stability ◽  
Polymorphic Transition ◽  
Ex Situ ◽  
Stable Phase ◽  
Iron Nitride ◽  
Phase System ◽  
Target Composition ◽  
Heat Treated

Although the general instability of the iron nitride γ′-Fe4N with respect to other phases at high pressure is well established, the actual type of phase transitions and equilibrium conditions of their occurrence are, as of yet, poorly investigated. In the present study, samples of γ′-Fe4N and mixtures of α Fe and γ′-Fe4N powders have been heat-treated at temperatures between 250 and 1000 °C and pressures between 2 and 8 GPa in a multi-anvil press, in order to investigate phase equilibria involving the γ′ phase. Samples heat-treated at high-pressure conditions, were quenched, subsequently decompressed, and then analysed ex situ. Microstructure analysis is used to derive implications on the phase transformations during the heat treatments. Further, it is confirmed that the Fe–N phases in the target composition range are quenchable. Thus, phase proportions and chemical composition of the phases, determined from ex situ X-ray diffraction data, allowed conclusions about the phase equilibria at high-pressure conditions. Further, evidence for the low-temperature eutectoid decomposition γ′→α+ε′ is presented for the first time. From the observed equilibria, a P–T projection of the univariant equilibria in the Fe-rich portion of the Fe–N system is derived, which features a quadruple point at 5 GPa and 375 °C, above which γ′-Fe4N is thermodynamically unstable. The experimental work is supplemented by ab initio calculations in order to discuss the relative phase stability and energy landscape in the Fe–N system, from the ground state to conditions accessible in the multi-anvil experiments. It is concluded that γ′-Fe4N, which is unstable with respect to other phases at 0 K (at any pressure), has to be entropically stabilised in order to occur as stable phase system. In view of the frequently reported metastable retention of the γ′ phase during room temperature compression experiments, energetic and kinetic aspects of the polymorphic transition γ′⇌ε′ are discussed.

Mechanical Performance of Steam-Cured Self-Compacting Concrete Incorporating Silica Fume and Limestone Powder

2021 ◽  
Vol 56 ◽  
pp. 111-122
Author(s):  
Youcef Ghernouti ◽  
Bahia Rabehi ◽  
Sabria Malika Mansour
Keyword(s):  
Heat Treatment ◽  
Silica Fume ◽  
Mechanical Performance ◽  
Limestone Powder ◽  
Maximum Temperature ◽  
Self Compacting Concrete ◽  
Curing Period ◽  
Heat Treated ◽  
Binder Ratio ◽  
Mechanical Strengths

In this paper, influence of heat treatment on evolution of mechanical strengths at early age, less than 24hours of self-compacting concretes containing limestone powder and silica fume as fine materials was investigated experimentally. Two compositions of self-compacting concrete have been studied; the first is elaborated with silica fume addition and the second with limestone powder, each mixture were prepared with a constant water/binder ratio of 0.39. Concrete samples were either cured in water at (23±1°C), or steam cured at 65°C maximum temperature over six hours (6h) curing period. Tests of mechanical strengths were performed on specimens cooled down slowly to room temperature after heating.The obtained results show that all self-compacting mixtures exhibited satisfying fresh properties and check EFNARC specifications of self-compacting concrete (slump flow diameter higher than 650mm, L-box ratio higher than 80% and sieve stability less than 17%).Mechanical strengths of concrete containing limestone addition are slightly lower than those of concrete based on silica fume at all ages. Moreover, heat treatment generates an improvement of compressive and flexural strength. Interesting compressive strengths are obtained. At 24 hours, after heat treatment, the strengths are already greater than 35 MPa. The values ​​are 37 MPa and 40 MPa for self-compacting concrete containing limestone powder and silica fume respectively compared to 40 MPa and 46 MPa obtained at 7 days for the corresponding non-heat treated concretes. Compressive strength gain of SCCs mixtures with limestone powder and with silica fume, undergoing heat treatment at the age of 24hours is 85% and 75% respectively compared to SCCs mixtures cured in water.

scholarly journals Heat Localization in the Medium in Blow-Up Regime

2020 ◽  
Keyword(s):  
Temperature Distribution ◽  
Blow Up ◽  
Maximum Temperature ◽  
Heating Regime ◽  
Heating And Cooling ◽  
Localized Heating ◽  
Finite Period ◽  
Equation Of Heat Conduction ◽  
The Given ◽  
Heat Front

The existence of the effect of heat metastable localization in the medium in the blow-up heating regime was experimentally proved. This is the regime in which the heating energy for a finite period of time tends to infinity. Previous theoretical studies have shown that in this case some regions, inside of which the temperature increases, may arise, while their size remains constant or decreases with time (heat localization regions). These regions exist as long as there is some energy input from the outside. An installation for the experimental study of the thermal blow-up regimes in a solid was developed. The object of research was an aluminum rod with a heater at its end. The temperature distribution along the rod was measured with thermocouples. The temperature of the rod end could vary according to the given law. Calibration of the installation was performed. The sensitivity of thermocouples was determined. The inertia of the heating and cooling process was estimated. The mathematical description of the thermal processes, occurring during the experiment, was made. The nonlinear equation of heat conduction for the rod was solved, with the heat exchange with the environment by convection and radiation taken into account. The thermal regime at the boundary, which is necessary to create the thermal structures, was determined. The temperature distribution in the rod in the blow-up regime and non-blow-up regime was measured. In the blow-up regime the heat front (the coordinate of the point with the temperature equal to half the maximum temperature) initially shifts from the heat source, and then in the opposite direction, and the size of the area under heating decreases. In the non-blow-up regime the size of the heated region increases all the time. The predicted effect was supposed to be used in installations for thermonuclear fusion where the target was heated by laser radiation pulses of a special shape. This effect can also be used for localized heating in cutting and welding, when the adjacent regions are not to get very hot, and in other similar situations.

High Indentation Resistance of Aluminum Borate Based Glass-Ceramics

2013 ◽  
Vol 545 ◽  
pp. 3-7
Author(s):  
Pat Sooksaen ◽  
Pisud Prasertcharoensuk ◽  
Jiraporn Damnernsawat ◽  
Nimit Pattamawitayanimit
Keyword(s):  
Heat Treatment ◽  
Glass Melting ◽  
Isothermal Holding ◽  
Surface Hardness ◽  
Glass Ceramics ◽  
Isothermal Heat Treatment ◽  
Aluminum Borate ◽  
Holding Period ◽  
Heating And Cooling ◽  
Heat Treated

This study investigated the bulk crystallization of 54B2O3-19SiO2-17Al2O3-5BaO-5MgO (mol%) glass. Melting was carried out at 1500°C for 1 h using a bottom-load electric furnace. The glass melt was cast into a block and annealed at 500°C for 2 h. Isothermal heat treatment was carried out at 1100°C for 2, 4, 8, 16, 32 h to form bulk crystallized glass-ceramics using a heating and cooling rate of 5°C/min. Phases present in the glass-ceramic samples were studied by x-ray diffraction. Crystalline Al4B2O9 and Al18B4O33 were the main phases and the phase stability depended on the isothermal time. Microstructures were observed by a scanning electron microscope. The size of aluminum borate whiskers/rods tend to increase with longer isothermal holding period. The whisker/ rod-like crystals uniformly oriented throughout the microstructure in all heat treated samples. This led to interlocking microstructure and hence an increase in hardness and fracture toughness. Glass-ceramics synthesized at longer heat treatment times resulted in an increase in the surface hardness and shorter path length at the corner of the diamond pyramid-shaped indenter. Glass-ceramics synthesized in this study can be applied as high temperature resistant machinable materials because their microstructures can resist micro-cracking upon indentation.

Creation of Patterned Gold Nanostructures via Electron-Beam-Induced Deposition

2013 ◽  
Vol 1546 ◽  
Author(s):  
Anastasia V. Riazanova ◽  
Johannes J. L. Mulders ◽  
Lyubov M. Belova
Keyword(s):  
Electron Beam ◽  
Three Dimensional ◽  
Area Ratio ◽  
Ex Situ ◽  
Geometrical Shape ◽  
Local Electron ◽  
Post Annealing ◽  
Treatment Conditions ◽  
Heat Treated ◽  
Electron Beam Induced Deposition

ABSTRACTOne of the methods to grow nanoscale three-dimensional (3D) Au patterns is to perform local electron-beam-induced deposition (EBID) using the Me2Au(acac) precursor inside the chamber of a scanning electron microscope (SEM). However, due to the organometallic nature of the chemical, the concentration of the metallic constituent in the as-deposited structure is dramatically low, at around 10 at. % of Au. Ex-situ post-annealing of Me2Au(acac) EBIDs is a very promising purification approach, resulting in an Au content of > 92 at. % after annealing at 600 °C. However, in most of the cases it also distorts the geometrical shape of the heat-treated structure, preserving of which is essential for the application. In this paper we present a systematic study of the dependence between the annealing parameters and resulting purity in combination with the shape of the Au structure. Optimized heat treatment conditions for the creation of well-purified high aspect ratio Au pillar array are presented; and for planar continuous structures, the importance of the parameter height to area ratio is identified.

scholarly journals Non-uniform crystallinity and temperature distribution during adjacent laser-assisted tape winding process of carbon/PA12 pipes

2020 ◽  
Vol 111 (11-12) ◽  
pp. 3063-3082
Author(s):  
S. M. Amin Hosseini ◽  
Martin Schäkel ◽  
Ismet Baran ◽  
Henning Janssen ◽  
Martin van Drongelen ◽  
...  
Keyword(s):  
Melting Behavior ◽  
Laser Source ◽  
Transient Temperature ◽  
Substrate Thickness ◽  
Crystallinity Degree ◽  
Heating And Cooling ◽  
Temperature Trends ◽  
The Matrix ◽  
Realistic Description ◽  
Composite Pipes

AbstractThe non-uniform temperature and crystallinity distributions present in carbon fiber–reinforced PA12 composite pipes, produced via laser-assisted tape winding (LATW), are investigated in this paper. The width of the laser source is usually larger than the substrate width which causes multiple heating and cooling of some regions of the (neighboring) substrate and hence temperature and crystallinity gradients during the adjacent hoop winding. A kinematic-optical-thermal (KOT) model coupled with a non-isothermal crystallinity model is developed to capture the transient temperature and crystallinity distributions for growing substrate thickness and width. The predicted temperature trends are validated with thermocouple and thermal camera measurements. The substrate temperature varies in the width direction up to 52%. This will lead to extra polymer remelting and possible degradation. The maximum variation of the crystallinity degree across the width is found to be 270% which shows agreement with the trend of the measured crystallinity degree. It is found that a more realistic description of the melting behavior of the matrix is needed to obtain a more accurate prediction of the crystallinity distribution.

Miocene high-temperature leucogranite magmatism in the Himalayan orogen

2020 ◽  
Author(s):  
Peng Gao ◽  
Yong-Fei Zheng ◽  
Matthew Jason Mayne ◽  
Zi-Fu Zhao
Keyword(s):  
High Temperature ◽  
Partial Melting ◽  
Plate Boundary ◽  
Source Rocks ◽  
Eastern Himalaya ◽  
Maximum Temperature ◽  
Himalayan Orogen ◽  
Metasedimentary Rocks ◽  
Se Tibet ◽  
Zircon Thermometry

Himalayan leucogranites of Cenozoic age are generally attributed to partial melting of metasedimentary rocks at low temperatures of <770 °C. It is unknown what the spatial distribution and characteristics of high-temperature (>800 °C) leucogranites are in the Himalayan orogen. The present study reports the occurrence of such leucogranites in the collisional orogen. We use the Ti-in-zircon thermometry in combination with the thermodynamically calibrated relationships of T-aSiO2-aTiO2 to retrieve crystallization temperatures of Miocene (ca. 17 Ma) two-mica granites from Yalaxiangbo, in the eastern Himalaya, SE Tibet. The results give the maximum temperature as high as ∼850 °C for granite crystallization, providing a significant constraint on the nature of thermal sources. Phase equilibrium modeling using metasedimentary rocks as the source rocks indicates that felsic melts produced at ∼850 °C and 6−10 kbar can best match the target leucogranites in lithochemistry. In this regard, the anatectic temperatures previously obtained for the production of Himalayan leucogranites would probably be underestimated to some extent. Such high temperatures are difficult to explain purely by the internal heating of the thickened orogenic crust. Instead, they require an extra heat source, which would probably be provided by upwelling of asthenospheric mantle subsequent to thinning of the orogenic lithospheric mantle by foundering along the convergent plate boundary. Therefore, the Himalayan leucogranites of Miocene age would be derived from partial melting of the metasedimentary rocks in the post-collisional stage.

Consistent and Repeatable Property and Residual Stress Control in Forged and Heat Treated Railway Wheels

2011 ◽  
Author(s):  
Jay Galbraith ◽  
George Ames ◽  
Scott Leister
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Pressure Control ◽  
Innovative Technology ◽  
Heat Treat ◽  
Heating And Cooling ◽  
Statistical Variation ◽  
Heat Treated ◽  
Railway Wheels ◽  
Process Controls

Consistent process control of wheel hardness and residual stresses developed during heat treatment are particularly important considerations for service life and safety of railway wheels. This paper details the process controls strategically located throughout an integrated, fully automated heat treatment system that can heat treat up to 65 railway wheels per hour. New, innovative technology such as in-line temperature measurements that control key process steps, uniform wheel heating and cooling, and quench water temperature and pressure control have resulted in wheel hardness and residual stress values with less statistical variation than older, traditional heat treat methods. Automatic serial number tracking and temperature measurement allow for statistical analysis of heat treat processes. Two years after the commissioning of this $18M facility, the quality and productivity benefits realized are discussed.

Modification of Banding in Dual-Phase Steels via Thermal Processing

2014 ◽  
Vol 783-786 ◽  
pp. 1067-1072 ◽  
Author(s):  
K. Mukherjee ◽  
L.S. Thomas ◽  
C. Bos ◽  
David K. Matlock ◽  
John G. Speer
Keyword(s):  
Heating Rate ◽  
Thermal Processing ◽  
Thermomechanical Processing ◽  
Rolled Sheet ◽  
Dual Phase ◽  
Heating And Cooling ◽  
Heat Treated ◽  
Cold Rolled ◽  
Dp780 Steel ◽  
Microscopic Techniques

The potential to utilize controlled thermal processing to minimize banding in a DP780 steel with 2 wt pct Mn was evaluated on samples processed on a Gleeble® 3500 thermomechanical processing simulator. All processing histories were selected to result in final dual-phase steel microstructures simulating microstructures achievable during annealing of initially cold rolled sheet. Strip samples were processed to evaluate the effects of heating rate, annealing time, annealing temperature, and cooling rate. The degree of banding in the final microstructures was evaluated with standard light optical microscopic techniques. Results are presented to illustrate that the extent of banding depended on control of both heating and cooling rates, and a specific processing history based on a two-stage heating rate can be used to minimize visible banding in selected final heat treated products.

OPTIMIZATION of DYNAMIC CH4 GAS HEAT TREATMENT OF NANOCRYSTALLINE STRONTIUM HEXAFERRITE

2012 ◽  
Vol 05 ◽  
pp. 752-759 ◽  
Author(s):  
R. DEHGHAN ◽  
S. A. SEYYED EBRAHIMI ◽  
H. R. KOOHDAR
Keyword(s):  
Heat Treatment ◽  
Phase Composition ◽  
Strontium Hexaferrite ◽  
Gas Flows ◽  
Optimum Conditions ◽  
X Ray Diffraction ◽  
Heating And Cooling ◽  
Heat Treated ◽  
Size And Morphology ◽  
Magnetic Nature

In this research the influence of dynamic CH 4 heat treatment on Sr -hexaferrite has been investigated. With the gas heat treatment, the phase composition, particles size and the morphology of Sr -hexaferrite change significantly. Due to this, the hard magnetic nature of the material changes from hard to soft. The strontium hexaferrite powder was prepared by conventional route with calcination of the mixture of strontium carbonate and hematite at 1100°C for 1 hour. Then the resultant Sr -hexaferrite was isothermally heat treated in methane dynamic atmosphere at various temperatures and gas flows for different times. The rate of heating and cooling were 10°C/min. The optimum conditions were obtained at 950°C and 15CC/min flow for 0.5 hour. The effects of gas heat treatment on the phase composition and the particles size and morphology were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibration Sample Magnetometery (VSM) techniques. The results show the decomposition of Sr -hexaferrite and reduction of the resultant hematite mainly to iron. The crystallite size of the resultant iron was also measured below 50nm.

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