Low Fusion Temperature Research Articles

Investigations on MoS2 plasma by infra-red pulsed laser irradiation in high vacuum

MoS2 targets were irradiated by infra-red (IR) pulsed laser in a high vacuum to determine hot plasma parameters, atomic, molecular and ion emission, and angular and charge state distributions. In this way, pulsed laser deposition (PLD) of thin films on graphene oxide substrates was also realized. An Nd:YAG laser, operating at the 1064 nm wavelength with a 5 ns pulse duration and up to a 1 J pulse energy, in a single pulse or at a 10 Hz repetition rate, was employed. Ablation yield was measured as a function of the laser fluence. Plasma was characterized using different analysis techniques, such as time-of-flight measurements, quadrupole mass spectrometry and fast CCD visible imaging. The so-produced films were characterized by composition, thickness, roughness, wetting ability, and morphology. When compared to the MoS2 targets, they show a slight decrease of S with respect to Mo, due to higher ablation yield, low fusion temperature and high sublimation in vacuum. The pulsed IR laser deposited MoS x (with 1 < x < 2) films are uniform, with a thickness of about 130 nm, a roughness of about 50 nm and a higher wettability than the MoS2 targets. Some potential applications of the pulsed IR laser-deposited MoS x films are also presented and discussed.

Hollow Core Double-Clad Fiber Coupler for Nonlinear Micro-Endoscopy

We report the design, fabrication and characterization of the first hollow core double-clad fiber coupler for nonlinear micro-endoscopy. It is made of a pure silica negative curvature hollow core double-clad fiber and a highly multimode fiber fused along each other. The fabrication of such a coupler was made possible thanks to the use of a soft (borosilicate) glass multimode fiber which can be fused along the negative curvature fiber without altering its geometry, thanks to its much lower fusion temperature. A 60% power transfer from the double-clad fiber to the multimode one was measured at 500 nm. Demonstration of two-photon fluorescence and second harmonic generation imaging was performed on unlabeled biological tissues with an endoscopic head mounted on the hollow core double-clad fiber coupler to demonstrate its applicability. This device greatly simplifies the integration of nonlinear micro-endoscopes based on hollow core double clad fibers.

Innovative preparation of α-LiFeO2 using spent LiFePO4 and Na2CO3 by ball milling-assisted roasting–water leaching method

α-LiFeO2 was successfully prepared using spent LiFePO4 and Na2CO3 by ball milling-assisted roasting–water leaching method. The effect of ball milling on roasting temperature was investigated by thermal analysis and X-ray diffraction (XRD) techniques. The effect of excess Na2CO3 on pure α-LiFeO2 synthesis was studied with the help of XRD techniques and scanning electron microscope (SEM). Results showed that ball milling pretreatment made α-LiFeO2 formation process shift towards lower roasting temperatures. Lithium iron oxides including α-LiFeO2 and Li0·5Fe2·5O4 could be obtained at 600 °C by ball milling, but 700 °C by hand grinding. With excess Na2CO3, more reaction channels provided by CO2 release and lower fusion temperature may accelerate the synthesis and grain refinement of α-LiFeO2. Pure α-LiFeO2 could be obtained with a molar ratio of 1:1.8 between LiFePO4 and Na2CO3 at 600 °C for 3 h. A new approach was provided for preparing α-LiFeO2 from spent LiFePO4 by roasting with dephosphorization agent Na2CO3.

Study on characteristics of coal gasification fine slag-coal water slurry slurrying, combustion, and ash fusion

In this study, the effects and mechanisms of coal gasification fine slag-coal water slurry (CGFS-CWS) preparation, combustion and ash fusion (AF) were assessed. As the CGFS content increased, the viscosity of the slurry increased, but the stability of the slurry improved significantly. The improvement in the slurry stability is due to the negative charge on the surface of CGFS is significantly stronger than that coal particles. This stronger charge provides strong electrostatic repulsion, which facilitates particle dispersion. The slurry combustion experiments revealed that the incorporation of CGFS significantly reduced the burnout temperature of the slurry and increased the maximum combustion rate. When the mixing amount was less than 8%, the flammability index, combustion stability index, and comprehensive combustion characteristic index significantly improved. Such finding may be due to the formation of activation centers by the alkali metals in CGFS, which promote combustion reactions. The AF temperature of the CGFS-CWS ash decreased as the CGFS blending amount in the slurry increased. This result is due to the melting-assisting effect produced by the Fe2O3 and sulfate contained in the CGFS ash. Albite crystallization with a lower fusion temperature also appeared in the CGFS-CWS, which may be generated by the reaction of nepheline in coal ash and sodium-containing compounds in CGFS ash at high temperatures.

Thermal Characteristics of Ash from Bamboo and Masson Pine Blends: Influence of Mixing Ratio and Heating Rate.

Thermal characteristics and kinetic parameters of ash from bamboo and masson pine blends with different mixing ratios were investigated using a thermogravimetric analyzer at different heating rates. The results showed that bamboo ash had lower fusion temperatures than the ash of masson pine. Mixing ratios and heating rates had a significant impact on the thermal characteristics and activation energy of ash samples. There was a synergistic interaction of chemical compositions in the bamboo and masson pine ashes. The mass loss of ash samples increased with the increase in the bamboo content of the blends. All ash samples had the maximum activation energy at the heating rate of 20 °C/min. The activation energy had a good linear correlation with mixing ratios at high conversion and heating rates. The optimum blend was suggested as 20% bamboo/80% masson pine due to its high activation energy. The results of this study are helpful to design a combustion system of bamboo and masson pine blends.

Effectiveness of lanthanum zirconate and Yttria stabilised zirconia freestanding APS thermal barrier coatings against natural CMAS attack at high temperatures

ABSTRACT CMAS-resistant thermal barrier coating is essential for durability of turbine components in advanced aero-engines. They are mostly evaluated using synthetic model CMAS powders. However, the degradation by natural CMAS can be higher considering their multiple constituents, nanostructure and low fusion temperature. The study compares the resistance of APS LZ and 8-YSZ freestanding disks to natural CMAS up to 1450°C and 100 h. The readily formed sealing layer of apatite, stable at 1450°C for 100 h, restricts further damage to LZ. But YSZ undergoes extensive destabilisation from metastable tetragonal (t´) to monoclinic and cubic phases after 1 and 10 h at 1450°C and 1250°C, respectively. Wetting, spread of CMAS and thermal diffusivities of the coatings are assessed. A 4–10 fold increase in thermal diffusivities is noticed. The paper attempts to bring some insight on CMAS reactivity with coating constituents based on fundamental considerations of ionicity, basicity, bond strength and diffusivities of species.

Investigation on Ash Slag from Combustion of Medium-Density Fiberboard Production Residues

Medium-Density Fiberboard (MDF) is made by breaking down of wood as conifer wood thinnings and wood processing industry residues including sawdust, which is glued and pressed together, and is widely used as a building material. Woody residues from production of MDF (MDFres) is a large and available amount and can be combusted for heat and energy production. In this study, MDFres fuel properties and ash melting behavior were investigated. The ash slag from combustion of MDFres in a residential combustion appliance was collected and analyzed with scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDX). The results show that MDFres ash contains considerably high content of calcium, silicon, potassium and sodium. The ash has a very low fusion temperature, of about 878 °C in oxidizing atmosphere. The ash slag collected from combustion of the MDFres has dense and intact structure and glass-like morphology, indicating that the ash experienced intensive melting. EDX spot analyses on the chemical composition of the slag reveal that Ca, Si, Al, Mg, K and Na are the main elements contained in the slag. Together with the spot analysis, EDX mapping analyses results indicate strong correlations between the elements Ca, Si and K and indicates formation of alkali silicates that have low melting temperatures during combustion of MDFres. Formation and presence of these low temperature melting compounds are the main reason for ash sintering and slagging at a sufficiently high combustion temperature.

Experimental Analyses Defining Mechanical Characteristics of Obtained W-Cu-Ni Composite Applied as a Radiation Shielding Material

This work aims to obtain a new composite material of system W-Cu-Ni using the powder metallurgy usable as material for strongly shielding of the gamma radiation as an environmental friendly alternative to lead. Tungsten (W) is the main shielding element in this composite. The main reason to use CuNi in this compound is the miscibility of both metals and their low fusion temperature, allowing liquid phase sintering. The tungsten has high density (19.25 gcm-3), high melting point (3,422 °C) and is presented as matrix of the composite. In order to meet the need for sintering with low temperatures, the liquid phase sintering technique has been used. For sintering temperature optimization, the particles of the metal powders have been homogenized in shape and size. In order to reduce the average particles size, a ball mill has been used for 48 hours. After grinding, the particle size analysis has showed that the mean particle size in WCuNi composition has been 8.6 μm. The powder mixture has been compacted in isostatic press at 200 MPa pressure. The samples have been sintered between 1,100 °C and 1,400 °C at 1100 mbar pressure with a flow of protective atmosphere (Ar2) for 180 min for each temperature. The formation of the isomorphic system CuNi is responsible for giving the mechanical characteristic of solid to the composite WCuNi. The result of micro hardness test shows a maximum of 331 HV and average of 276 HV. Optical and electronic microscopy (SEM) with EDS have been undertaken in order to characterize the samples. The classical scientific method of experimentations with gamma radiation of the cobalt-60 source by attenuation of the energies has been employed to study these effects on the samples. The results shows that composite has more shielding efficient than lead and is safety for life and environment when compared with lead toxity.

Evaluation of slagging and fouling characteristics during Zhundong coal co-firing with a Si/Al dominated low rank coal

Blending is a promising method to improve ash related problems to meet combustion requirements. To evaluate the slagging and fouling characteristics of Zhundong coal (ZD) co-firing with a Si/Al dominated low rank coal (WD), the influence factors of slagging and fouling propensity based on ash composition and fusion temperatures was discussed. Release, thermal change and transformation behaviors of minerals in the mixed ashes were investigated by Thermogravimetric analysis and FactSage software. Morphology and chemical characteristics of ash deposits along heating surfaces of a practical boiler co-firing these two coals were also analyzed. The results show that when alkali/acid ratio (RB/A) is higher than 0.400 and difference value between ST and DT (ST-DT) lower than 20 °C, blending presents a severe slagging and fouling tendency. Under high temperature, ZD ash underwent a major weight loss which, is characterized by intense endothermic reactions and leads to the low ST-DT value. Feldspar, tridymite and anhydrite are the dominated minerals for blending ashes, and transformation of them contributes to the low fusion temperatures. Deposits along heating surfaces of boiler for burning ZD coal blending could be divided into two groups: condensed deposits and molten deposits. The former is due to the volatilization of mineral elements and have higher AFTs and the latter mainly due to the formation of low fusion temperature eutectics.

Ash fusion characteristics of bamboo, wood and coal

Ash fusion characteristics of bamboo, masson pine and coal were investigated using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRF results showed that the major components of bamboo ash were K2O, SiO2 and SO3. Masson pine ash mainly included Fe2O3 and CaO. Coal ash was comprised of SiO2, Al2O3, CaO, Fe2O3 and SO3. The variation of major components resulted in different fusion characteristics, such as the low fusion temperature of bamboo ash and the high thermal conductivity of masson pine ash. XRD results confirmed chemical compositions transformation because six main chemical reactions occurred during thermal treatment process. SEM and TEM results showed that the elongated grains or plates of various sizes of all thermal treated ashes disappeared and they had less pores and denser structure on the surface, indicating structure transformation. The results from this research will be helpful to promote utilization of masson pine and bamboo for fuel in power station of China.

A study on air-cooling waste heat recovery from molten slag of slag-tap boilers

For a better utilization of Zhundong coals which have high fouling and slagging tendency, the slag-tap boiler has attracted much attention. To avoid the high sensible heat loss of discharged molten slag, an air-cooling waste heat recovery system is proposed. Energy and economic analyses are conducted to investigate the effectiveness of heating the desulfurized flue gas by hot air and the influences of partially substituting the secondary air by hot air on heat transfer of air preheater and thermal efficiency of boiler. A case study is performed by referring to a typical 50 MW cyclone boiler with nine types of low fusion temperature coals. The results show that for coals with low ash content, the temperature increment of desulfurized flue gas can be over 7 ℃. While for coals with high ash content, the flue gas temperature can be heated to more than 70 ℃, and the surplus hot air can be sent to the furnace. When the hot air is introduced to partially substitute the secondary air, an instantaneous impact on the air preheater will give rise to a decrement of quantity of heat transferred and increments of temperatures of exit flue gas and hot secondary air. The variations of these thermodynamic parameters become smaller with increasing hot air temperature. After introduction of hot air, the thermal efficiency of boiler can increase, resulting in a decrease of fuel consumption rate. In addition, the heating surface area of air preheater can be reduced.

Effects of SiO2/Al2O3 Ratios on Sintering Characteristics of Synthetic Coal Ash

This article explores the effects of SiO2/Al2O3 ratios (S/A) on sintering characteristics and provides guidance for alleviating ash depositions in a large-scale circulation fluidized bed. Five synthetic coal ash (SCA) samples with different S/As were treated in a muffle furnace for 12 h at different temperatures (from 773 K to 1373 K, in 100 K intervals). The morphological and chemical results of the volume shrinkage ratio (VSR), thermal deformation analysis by dilatometer (DIL), scanning electron microscope (SEM), X-ray photoelectron spectrometer (XPS), and X-ray diffraction (XRD) were combined to describe the sintering characteristics of different samples. The results showed that the sintering procedure mainly occurred in the third sintering stage when the temperature was over 1273 K, accompanied with significant decreases in the VSR curve. Excess SiO2 (S/A = 4.5) resulted in a porous structure while excess Al2O3 (S/A = 0.5) brought out large aggregations. The other three samples (S/A = 1.5, 2.5, 3.5) are made up of an amorphous compacted structure and are composed of low fusion temperature materials (e.g., augite and wadsleysite.). Sintering temperatures first dramatically decrease to a low level and then gradually rise to a high level as S/A increases, suggesting that Al2O3-enriched additives are more effective than SiO2enriched additives in alleviating depositions.

Transformation of minerals in direct coal liquefaction residue under gasification atmosphere at high temperatures

AbstractThe transformation behavior of mineral matters in direct coal liquefaction residue from Shenhua Corporation under gasification atmosphere at high temperatures was examined by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Mössbauer spectroscopy was also applied to investigate the iron-bearing minerals and the valence distribution of iron in ash at different temperatures. The results show that the major minerals in coal liquefaction residue are quartz, calcium sulfate, millosevichite, pyrrhotite, kaolinite, and calcite. At high temperatures, they become anorthite, gehlenite, maghemite and magnetite. Due to the formation of anorthite, gehlenite eutectic, ash of coal liquefaction residue exhibits low fusion temperature. The iron-bearing minerals characterized in ash include maghemite, magnetite, fayalite, and the vitreous matter. The content of iron in vitreous matter increases with increasing temperature. Meanwhile, Fe2+/Fe3+ significantly increases from 1.08 to 2.39 as temperature increases from 1100 to 1200°C for the reduction of maghemite, and it is not obviously changed above 1200°C. Furthermore, the liquid phase in ash calculated by FactSage increases with temperature owing to the increase of iron in vitreous phase. In hence, high content of iron in ash from coal liquefaction residue is the major reason for its low ash fusion temperatures.

Leaching of Alkali and Alkaline Earth Metallic Species from Rice Husk with Bio-oil from Its Pyrolysis

Removal of alkali and alkaline earth metallic (AAEM) species, in particular, that of potassium, is an effective way to upgrade rice husk, because its combustion and gasification often suffer from the formation of potassium silicate with a low softening or fusion temperature. This work has been investigating the leaching of AAEM species with a bio-oil (BO) from the pyrolysis of the parent rice husk. The leaching with BO, which had a pH of 2.59, gave removal rates of K and Na equivalent to or higher than those with an aqueous solution of hydrogen chloride (HCl aqueous) or acetic acid (AcOH aqueous) at pH of 2. The leaching abilities of BO in terms of the removal rates of Mg and Ca were equivalent to HCl aqueous at pH 0 and AcOH aqueous at pH < 2, respectively. Such performances of BO arose from the presence of not only AcOH with a concentration of 6 wt % but also phenolic compounds (phenol, alkylphenols, and methoxyphenols). The phenols permeated into the organic matrix of the rice husk, forming hydrophobic...

Electrodeposition of Zn - Ni Alloys from Protic Ionic Liquids

Electrodeposition of metals and alloys is currently carried out from aqueous solutions despite the environmental problems associated to the complex baths needed to obtain electrodeposits with controlled properties (composition, roughness, etc). In this context, ionic Liquids (IL) are studied as an option to be used as new green solvents for electrodepositon due to their interesting properties : non volatility, low fusion temperature, conductivity, viscosity, etc. However, commercial LIs are generally toxic and highly reactive in the presence of water which limits their application in many chemical and electrochemical processes. In this work, we study the use of environmentally friendly and stable protic ionic liquids (PILs) as solvents in the electrochemical deposition of nanostructured metals (Ni and Zn) and their alloys. The studied PILs synthetized by using well-known amounts of a linear aliphatic amine and a single-chain carboxylic acid as precursors in order to get mixtures of controlled composition (e.g., pure PIL or mixture of a pure PIL and its pure acidic or basic precursor as a co-solvent) to be applied directly as the depositon bath in the electrochemical deposition of nanostructured nickel, zinc and their alloys.The electrodeposition process was studied by electrochemical techniques and the obtained deposits were characterized by optical microscopy and also by SEM and AFM techniques. For the electrodeposition of the studied single metals (Ni and Zn), results shown that nanostructured nickel and zinc deposits can be electrodeposited from these protic ILs with faradic efficiencies dependent on the composition of the IL and on the temperature; the influence of the physicochemical properties of the studied PILs and of the temperature on the morphological characteristics of the obtained deposits were also evaluated. The major effects were attributed to the influence of composition on mass and charge transfer properties of the PILs.In the case of the electrodeposited Ni-Zn alloys, results allow to evaluate the influence of the composition of the ionic liquid on the composition of the electrodeposited alloys. In these media, it is observed that Zn-rich alloys are commonly formed. The morphology of the obtained electrodeposits are strongly dependent on the temperature.These results allow conclude that the studied PILs are good as new reaction media with tunable properties for electrochemical applications, allowing to propose them as new systems for electrodeposition processes, as new single solvents without the use of organic additives.Acknowledgements: Authors gratefully acknowledge financial support from SEP–CONACyT Program (Project CB 2011-1-168032). TBGR is indebted to CONACYT for the fellowship.

Influência das composições química e mineralógica de cinzas de misturas de carvões para PCI no comportamento de fusibilidade e viscosidade a altas temperaturas

Some aspects of permeability deterioration in blast furnace process at high rates of pulverized coal injection are not well known yet. At operational practice variations in the ash quality of injected coals can affect the furnace performance. Previous work has investigated the behavior of individual coals ash at high temperatures in relation to the chemical and mineralogical compositions. This work aimed to assess this behavior for coal blends. Four coals and seven blends were selected and ashed at 800-850°C. The samples were analyzed by X-ray fluorescence and X-ray diffraction techniques and ASTM ash fusion (AFT) and viscosity tests were performed. Ash containing high contents of Si and Al showed higher fusion temperatures and higher viscosity at 1500°C, due mainly to the higher content of Mullite and to the low basicity, while those presenting significant contents of Fe, Ca and S had lower fusion temperatures and lower viscosity, due to the higher content of Anorthite and/or to the higher basicity.

Effect of fluorine and chlorine on slag melting characteristics: Experimental study and simulation by neural networks

Hazardous waste from chemical factories including fluorine and chlorine has rather low fusion temperatures. During incineration in a rotary kiln incinerator, hazardous waste including fluorine and chlorine melts and turns into slag, possibly adhering to the inner wall and leading to unstable operation of the incinerator. Prediction of the melting characteristics of hazardous waste including fluorine and chlorine hence plays an important role in preventing slagging. The effect of various chemical components on fusion temperatures (deformation temperature, DT; softening temperature, ST; hemisphere temperature, HT; and flow temperature, FT) has been investigated experimentally: Na 2O and NaF are the most remarkable chemical compounds among those investigated. Correlations between fusion temperatures and chemical components have been investigated; neural networks have been used to predict four characteristic melting temperatures and are verified by tested slag samples of hazardous waste including fluorine and chlorine. Relative errors of fusion temperatures (computed vs. measured) are mostly less than 1.2%.

A Study on Coal Properties and Combustion Characteristics of Blended Coals in Northwestern China

The utilization of blended coals has become popular in northwestern China. In this paper, investigations on coal properties and combustion characteristics of blended coals have been carried out to provide guidance for blended-coal-fired plants. Experimental results show that proximate, ultimate, and calorific value analyses of blended coals can be calculated by mass-weighted average of individual coals. However, grindability, ash composition, ash fusion temperatures, and some characteristics related to combustion performance of blended coals cannot be predicted accurately from those of individual coals and the mixture ratio. Blending a coal of high fusion temperatures with a coal of low fusion temperatures can significantly increase the ash fusion temperatures of blended coals. Thermogravimetric experimental results indicate that the intense combustion stage of blended coals is quite different from those of individual coals. Thermogravimetric curves of blended coals lie between those of individual coals b...

Prediction of Performance From PRB Coal Fired in Utility Boilers With Various Furnace and Firing System Arrangements

The present regulatory requirements enforce the modification of the firing modes of existing coal-fired utility boilers and the use of coals different from those originally designed for these boilers. The reduction in SO2 and NOx emissions was the primary motivation for these changes. Powder river basin (PRB) coals, classified as subbituminous ranked coals, can lower NOx and SOx emissions from power plants due to their high volatile content and low sulfur content, respectively. On the other hand, PRB coals have also high moisture content, low heating value, and low fusion temperature. Therefore when a power plant switches from the designed coal to a PRB coal, operational challenges were encountered. A major problem that can occur when using these coals is the severe slagging and excess fouling on the heat exchanger surfaces. Not only is there an insulating effect from deposit, but there is also a change in reflectivity of the surface. Excess furnace fouling and high reflectivity ash may cause reduction in heat transfer in the furnace, which results in higher furnace exit gas temperatures (FEGTs), especially with opposite wall burners and with a single backpass. Higher FEGTs usually result in higher stack gas temperature, increasing the reheater spray flow and therefore decreasing the boiler efficiency with a higher heat rate of the unit. A successful modification of an existing unit for firing of PRB coals requires the evaluation of the following parameters: (1) capacities or limitations of the furnace size, (2) the type and arrangement of the firing system, (3) heat transfer surface, (4) pulverizers, (5) sootblowers, (6) fans, and (7) airheaters. In the present study we used a comprehensive methodology to make this evaluation for three PRB coals to be potentially fired in a 575 MW tangential-fired boiler.

Thermal shock study of α-alumina doped with 0.2% MgO

Thermal shock behaviour of α-alumina doped with 0.2% MgO is studied. A uniformly mixed powder of α-alumina, magnesia and 2% PVA solution is dried, granulated and uniaxially pressed into circular discs of 30 mm diameter and 3 mm thick. The discs are sintered at a maximum temperature in the range of 1500–1650 °C for 3 h. The thermal shock test is carried out by heating the sample with an oxy-hydrogen flame and by monitoring the crack formation by acoustic emission technique. In general, the samples possess high thermal shock resistance close to their melting temperature. The spinels formed due to MgO doping possess low fusion temperature which hinders the crack growth. The same has been confirmed from scanning electron microscope (SEM) studies. The samples sintered at lower temperature possess higher thermal shock resistance than those sintered at higher temperature. This is attributed to the higher porosity. The abnormal grain growth (AGG) associated with high sintering temperature might have contributed to lowering of thermal shock resistance. To summarize, MgO-doped alumina samples possess high thermal shock resistance by avoiding the catastrophic failure due to the formation of low fusion spinels.