scholarly journals The impact of burning on the structure and mineral composition of bat guano

2021 ◽  
Vol 50 (2) ◽  
pp. 189-202
Author(s):  
Joyce Lundberg ◽  
Donald McFarlane
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Low Temperature ◽  
Morphological Changes ◽  
Colour Change ◽  
Spontaneous Ignition ◽  
Severe Damage ◽  
Future Studies ◽  
The Impact ◽  
Microbial Action

Here we addressed the question of whether burning of guano produces a characteristic suite of morphological changes and/or unique mineralogical products. The changes observed in our experimental burning of guano (both fresh and decayed) included colour change (blackening), grain size and morphological change (grain size generally reduced, morphology rendered generally less distinct), alteration of minerals by dehydration (e.g., gypsum to anhydrite, brushite to whitlockite), and production of new minerals or compounds (e.g., augelite, bayerite, giniite, graphite, oldhamite, strontium apatite, tridymite). The key morphological feature we found that may be diagnostic of burning was severe damage to crystals from rapid dehydration (cracks and striations, leading to eventual fragmentation). The key mineralogical feature we found was production of graphite. The high temperature exotic minerals that were produced (giniite, augelite, tridymite, oldhamite) were all found not to be high temperature obligate. Evidence gleaned from the literature suggests that a great number of the minerals associated with high temperatures can also be synthesized in low temperature settings such as weathering or microbial action (exemplified in the extremely complex biology and biochemistry of decaying guano). While the presence of any one of these minerals is not diagnostic of fire, it could be argued that the suite taken as a whole is moderately strong evidence for burning. In future studies, the chemistry of carbon aromaticity may prove to be the best diagnostic test for pyrolysis. A survey of the conditions under which documented spontaneous ignition occurs leads us to conclude that spontaneous ignition of guano inside a cave is an extremely unlikely event, and any suggestion/assertion to this effect should be rigorously supported.

scholarly journals X-ray diffraction analysis of kaolin M1 and M2 via the Williamson–Hall and Warren–Averbach methods

2021 ◽  
pp. 174751982098472
Author(s):  
Lalmi Khier ◽  
Lakel Abdelghani ◽  
Belahssen Okba ◽  
Djamel Maouche ◽  
Lakel Said
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Low Temperature ◽  
Diffraction Analysis ◽  
Mechanical Resistance ◽  
X Ray Diffraction ◽  
Integral Breadth ◽  
X Ray ◽  
Mullite Phase

Kaolin M1 and M2 studied by X-ray diffraction focus on the mullite phase, which is the main phase present in both products. The Williamson–Hall and Warren–Averbach methods for determining the crystallite size and microstrains of integral breadth β are calculated by the FullProf program. The integral breadth ( β) is a mixture resulting from the microstrains and size effect, so this should be taken into account during the calculation. The Williamson–Hall chart determines whether the sample is affected by grain size or microstrain. It appears very clearly that the principal phase of the various sintered kaolins, mullite, is free from internal microstrains. It is the case of the mixtures fritted at low temperature (1200 °C) during 1 h and also the case of the mixtures of the type chamotte cooks with 1350 °C during very long times (several weeks). This result is very significant as it gives an element of explanation to a very significant quality of mullite: its mechanical resistance during uses at high temperature remains.

scholarly journals Can Ultra-fast High Temperature Sintering (UHS) Boost Transparency of Alumina?

2021 ◽  
Author(s):  
Milad Kermani ◽  
Danyang Zhu ◽  
Jiang Li ◽  
Jinghua Wu ◽  
Yong Lin ◽  
...  
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Low Temperature ◽  
Green Density ◽  
Alumina Ceramics ◽  
Fine Grained ◽  
Reducing Atmosphere ◽  
Transparent Alumina ◽  
Rapid Sintering ◽  
First Time

Abstract Established routes for consolidation of transparent alumina ceramics by pressure-less sintering requires several hours of dwelling in a reducing atmosphere at a temperature exceeding 1600 ℃. Here, for the first time, we report on low temperature and ultrafast consolidation of translucent alumina ceramics. Transparency was promoted by the synergistic of high initial green density (62.7 %) and rapid sintering using Ultra-fast High Temperature Sintering (UHS) technique. The proposed approach, using a heating rate of 430 ℃/min and dwelling time of 15 minutes, resulted in ultra-fine-grained translucent alumina ceramics at 1359 ± 57 ℃ with a grain size of 0.39 µm, and an in-line transmittance of 28.7 % at a wavelength of 700 nm. For comparison, conventionally fired counterparts were opaque due to their incomplete densification, pore coalescence.

Effect of Different Tempering Temperatures on Microstructure and Impact Property of 20CrMnTi Steel

2014 ◽  
Vol 900 ◽  
pp. 92-95
Author(s):  
Sheng Xu Liu ◽  
Yi Qiang Xiao ◽  
Ming Long Kang ◽  
Jian Min Zeng ◽  
Guo An Wang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Low Temperature ◽  
Fracture Morphology ◽  
Optical Microscope ◽  
Impact Property ◽  
Medium Temperature ◽  
The Impact ◽  
Type Of Fracture ◽  
Scanning Electron

The effect of different tempering temperatures on microstructure and impact property of 20CrMnTi steel has been studied on Zwick/roell Amsler PKP 450 pendulum machine, SU-8020 scanning electron microscope (SEM) and optical microscope. The results shows that the impact property of 20CrMnTi steel is dramatically improved after high-temperature tempering. However, the minimum value occurs when it was tempered at 350°C because of low-temperature tempering brittlement at this degree. The SEM fracture morphology was typical dimples after high temperature tempering, and the type of fracture was ductile fracture; the type of cleavage characteristic and quasi cleavage characteristic were generated on the fracture morphology at low-temperature and medium-temperature tempering respectively, and the type of fracture was brittle.

Effect of the Mixing-Melt and Superheating on the Primary Si Phase of Hypereutectic Al-20%Si Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 79-88
Author(s):  
Lian Deng Wang ◽  
Ding Yi Zhu ◽  
Zhe Liang Wei ◽  
Yong Lu Chen ◽  
Li Guang Huang ◽  
...  
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Low Temperature ◽  
Melt Mixing ◽  
Local Melting ◽  
Average Temperature ◽  
Present Alloy ◽  
Primary Si

The Al-20%Si alloy was prepared by mixing the high temperature melt of hypereutectic Al-30%Si alloy with the pre-crystallized low temperature hypoeutectic Al-10%Si alloy melt and then superheating the mixture, i.e., melts mixing and superheating (for short: MMS), combining with chemical metamorphism. The effect of pre-crystallized characteristic of the mixed melt on microstructure of Al-20%Si alloy was then investigated, The primary Si granules of the sample, poured by melt mixing with different composition and temperature, were well distributed with a grain size of less than 36μm. And after superheating, the primary Si phase of the mixed melt could be further refined and distributed more uniformly, which if adding the modificator into the mixed melt, the size of primary Si were been deceased and refined by less than 20μm. The analysis result shows that the decrease in the temperature of the mixed melt, from the average temperature of 740 °C for the mixture of Al-30%Si (900°C) and Al-10%Si (580°C) to 670°C for present alloy, leads to the increase in the degree of undercooling, and consequently to the refinement of primary Si. During the superheating, the growth, local melting, as well as the proliferation of primary Si occurred because of the unhomogeneous micro-distribution of the temperature and composition within the mixing melt, resulting in the further decrease in the grain size of primary Si. And adding the modificator could promote the effect of modification of primary Si of MMS process on the hypereutectic Al-Si alloy.

scholarly journals Effect of temperature on Chromatophores of freshwater prawn, Macrobrachium lamarrei (Crustacea-Decapoda)

2017 ◽  
Vol 5 (01) ◽  
Author(s):  
Sanjive Shukla ◽  
Richa Shukla ◽  
Sandeep Shukla ◽  
Sareef Ahamad ◽  
Anand Mishra
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Direct Contact ◽  
Colour Change ◽  
Freshwater Prawn ◽  
Effect Of Temperature ◽  
Colour Changes

Charomatophores are colour bearing cells, responsible for colouration and colour changes in animals specially in freshwater Crustaceans. As animal’s integument comes in direct contact with the environment therefore they may provide foremost information of the changes in surroundings. Freshwater prawns, M. lamarrei were subjected to low (200C ± 20C), normal (260C ± 20C) and high temperature (350C ± 20C) showed remarkable changes in colouration, chromatophore number and structure. Animals became dark coloured at low temperature while lighter in colouration at high temperature in comparison to the animals kept at normal temperature. Most of the chromatophores were in stellate and punctate stage in low and high temperature respectively in comparison to reticulate stage at normal temperature. Mechanism of colour change as well as importance of colour in marketing value of freshwater prawns has been discussed.

scholarly journals Impacto de las variaciones de temperatura diaria en la historia natural de los anuros tropicales

2016 ◽  
Vol 65 (1) ◽  
pp. 55 ◽  
Author(s):  
Manuel Hernando Bernal-Bautista ◽  
Jorge Luis Turriago-González ◽  
Francisco Antonio Villa-Navarro
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Variable Temperature ◽  
Developmental Time ◽  
Maximum Temperature ◽  
Medium Temperature ◽  
Variable Environment ◽  
Gosner Stage ◽  
C 23 ◽  
The Impact

Anuran embryos and tadpoles are daily exposed to wide thermal variations in their ponds, with maximum temperatures at midday. The aim of this research was to study the impact of three daily variable thermal environments (with maximum experimental temperatures between 10:00 and 16:00 hours), on the survival, developmental time and body size of metamorphs of four tropical anuran species from lowland habitats in Colombia. A total of 50 embryos (Gosner stage ten) to metamorphosis (Gosner stage 46) of Rhinella humboldti, Hypsiboas crepitans and Engystomops pustulosus were exposed to each one of the three daily variable temperature treatments: high temperature (mean = 27.5 °C; maximum temperature = 34 ± 1 °C; range = 23-35 °C), medium temperature (25.5 °C; 29 ± 1 °C; 23-30 °C), and low temperature (24 °C; 24 ± 1 °C; 23-25 °C). For the other species, Espadarana prosoblepon, 40 embryos to metamorphosis were exposed to each one of the following thermal treatments: high temperature (mean = 22 °C; maximum temperature = 25 ± 1 °C; range = 18-26 °C), medium temperature (20.5 °C; 22 ± 1 °C; 18-23 °C), and low temperature (19 °C; 19 ± 1 °C; 18-20 °C). For all species, the thermal variable environment with the highest temperature showed the greatest accumulated survival, reduced significantly the developmental time from embryos to metamorphs, and the snout-vent-length of metamorphs. Therefore, under field conditions where ponds are exposed to thermally variable environments, the highest temperatures may promote a decrease in the period of time to metamorphosis, and a positive increase for the anuran survival; nevertheless, extreme temperatures were also found in the microhabitat of the species studied, higher than their upper thermal limits reported, which suggest a vulnerable situation for them and other tropical anurans from similar habitats.

Microstructure and deposition kinetics of Nb prepared by chemical vapor deposition

2018 ◽  
Vol 32 (22) ◽  
pp. 1850257 ◽  
Author(s):  
Yan Wei ◽  
Da Wei Zhang ◽  
Jun Wang ◽  
Hong Zhong Cai ◽  
Xu Xiang Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Chemical Vapor Deposition ◽  
High Temperature ◽  
Low Temperature ◽  
Deposition Rate ◽  
Vapor Deposition ◽  
Deposition Temperature ◽  
Chemical Vapor ◽  
Deposition Kinetics ◽  
Hydrogen Flow

The deposition kinetics and microstructure of chemical vapor deposition (CVD) of Nb on the Mo substrate at different deposition variables is investigated. The morphology of CVD Nb is columnar, it exhibits a strong preferred orientation and its growth direction is perpendicular to the substrate surface, the deposition rate and grain size increased with the increase of deposition temperature. The deposition rate conforms to the Arrhenius formula, the activation energy [Formula: see text] at high temperature and low temperature is 0.85 kJ/mol and 7.2 kJ/mol, respectively. The rate-limiting step for CVD Nb at high temperature is chemical reaction step, whereas that is the mass transport step at low temperature. Chlorination temperature has a weak influence on deposition rate and grain structure, the deposition rate and grain size of CVD Nb increased with the increase of the chlorine flow and hydrogen flow, the maximum deposition rate is [Formula: see text], thus, the optimum deposition temperature is 1200[Formula: see text]C, chlorination temperature is 350[Formula: see text]C, hydrogen flow is 400 ml, chlorine flow is 200 ml.

Experimental Study on Damage Characteristics of CFRPs/Aluminum Honeycomb Sandwich Structure Impacted by Ultra-High Speed Under High and Low Temperatures

2020 ◽  
Vol 20 (02) ◽  
pp. 2050028
Author(s):  
Enling Tang ◽  
Xiaoqi Zhang ◽  
Yafei Han
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Sandwich Structure ◽  
Impact Speed ◽  
Damage Characteristics ◽  
Honeycomb Sandwich ◽  
Temperature Environment ◽  
Aluminum Honeycomb ◽  
The Impact ◽  
Honeycomb Sandwich Structure

With the rapid development of material science, the original aluminum alloy shield structure of spacecraft has been gradually replaced by sandwiched structure of carbon fiber reinforced resin matrix composite structure with aluminum honeycomb. In order to reveal the damage characteristics induced by debris impacting on shield structure of spacecraft and aiming at the engineering requirements that spacecraft undergo alternately high and low temperature environment during on-orbit operation, CFRPs/aluminum honeycomb core sandwich shield structure is used as the impact object. The damage characteristics of 2A12 aluminum projectile impacting on CFRPs/aluminum honeycomb sandwich structure with different aluminum honeycomb arm lengths at different impact velocities are studied by using the high and low temperature system for the target and the loading system of two-stage light gas gun. The experimental results show that the arm lengths of aluminum honeycomb have little effect on the perforation area of front and rear surfaces of CFRPs/aluminum honeycomb sandwich structure at high temperature, but the impact speed has a great effect on the perforation areas of front and rear surfaces of rear panels. The lower the impact speed is, the smaller the perforation diameter is. The deformation and ablation areas of the front and rear surfaces of the aluminum honeycomb increase with the increasing of the arm length of the aluminum honeycomb. At the same time, the physical quantities mentioned above have similar changes in low temperature environment. The fitting formulas, such as the relationships among perforations of the front and rear surfaces of CFRP and the arm lengths of aluminum honeycomb, and ablation area of aluminum honeycomb and the arm lengths of aluminum honeycomb are given at the given experimental conditions. The micro-morphology and damage characteristics of the panels and aluminum honeycomb are analyzed at the different locations near the impact point at high temperature.

scholarly journals The impact of extreme climate change on the fluctuation of electricity energy demand——Evidence from China's prefecture-level cities

2021 ◽  
Vol 260 ◽  
pp. 01014
Author(s):  
Yudong Tan ◽  
Tong Jiang ◽  
Hao Xiao ◽  
Jingyi Tang ◽  
Zhen Jia
Keyword(s):  
Climate Change ◽  
High Temperature ◽  
Low Temperature ◽  
Energy Demand ◽  
Electricity Demand ◽  
Extreme Climate ◽  
Extreme High Temperature ◽  
Residential Electricity ◽  
Negative Effect ◽  
The Impact

Climate change directly make the demand for electricity diversified and uncertain, which increase the risk of power grid operation. This paper attempts to explore the impact of extreme climate change on the fluctuation of China's electricity energy demand from the perspective of climate change. Based on the panel data of 90 prefecture-level cities in China from 1989 to 2017, the author builds an econometric model to test the impact of extreme low temperature and extreme high temperature on electricity demand. The results show that the occurrence of extreme high temperature weather has a positive effect on residential electricity demand while the emergence of extreme low temperature weather has a negative effect.

Estimation of Impact Toughness Transition Temperatures of As-Quenched Steels

2018 ◽  
Vol 941 ◽  
pp. 498-503
Author(s):  
Sakari Pallaspuro ◽  
Antti J. Kaijalainen ◽  
Saara Mehtonen ◽  
Jukka I. Kömi ◽  
Zhi Liang Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Low Temperature ◽  
Impact Toughness ◽  
Yield Strength ◽  
Rolling Temperature ◽  
Transition Temperatures ◽  
Finish Rolling Temperature ◽  
Finish Rolling ◽  
Low Temperature Toughness ◽  
The Impact

High strength and sufficient toughness are key requirements for modern high-performance structural steels. In an attempt to develop a suitable estimation of impact toughness transition temperatures for as-quenched steels, we investigated the determiners of low-temperature toughness with a group of thermomechanically rolled direct-quenched steels with varying martensite contents. These were produced by altering chemical composition, finish rolling temperature and reduction below the non-recrystallization temperature, i.e. austenite pancaking, and characterised in terms of microstructural constituents, grain size distributions, texture and fractography. Provided the finish rolling temperature is high enough to avoid the formation of granular bainite on subsequent cooling, high levels of austenite pancaking yield the best combinations of low-temperature toughness and strength by effectively refining the size of the coarsest grains and randomizing the texture. While absolutely no direct correlation is found within as-quenched steels between the impact toughness transition temperatures and yield strength alone, T28J and T50 do closely follow a dynamic reference toughness, i.e. the opening stress intensity factor defined by yield strength and the size of the coarsest grains in the effective grain size distribution. This parameter reflects the transition temperatures – the lower the temperature, the lower the reference toughness needed to cause a local brittle fracture. Finally, we show that the impact toughness transition temperatures T28J and T50 of as-quenched steels can be accurately estimated, irrespective of the test specimen orientation, by utilizing just the dynamic reference toughness and the fraction of {100} cleavage planes within ± 15° of the specimen notch plane.

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