Proper Melting Research Articles

Preparation and Properties of Capric-Lauric-Palmitic Acid Eutectic Mixtures/Expanded Graphite Composite as Phase Change Materials for Energy Storage

This work is focused on the preparation and properties of ternary fatty acid eutectic mixtures/ expanded graphite form-stable phase change materials (PCMs). Based on the theoretical calculation of the mass ratio and ternary eutectic melting temperature, the ternary eutectic mixture of capric acid (CA), lauric acid (LA) and palmitic acid (PA) was prepared firstly, which is for the sake of decreasing the phase transformation temperature. Thermal characteristics such as melting temperature and latent heat of fusion of these developed eutectics measured by using Differential Scanning Calorimetry (DSC) technique, which also showed that the eutectic mixture was composed by CA, LA and PA in the mass ratio of 59.7:30.1:10.02. Then the CA–LA–PA was absorbed in expanded graphite (EG), which acts as a supporting material, the optimum mass ratio of CA–LA–PA to EG is 17:1. The CA–LA–PA/EG composites were characterized by the scanning electronic microscope (SEM), differential scanning calorimeter (DSC). The SEM observations showed that the CA–LA–PA was adsorbed into the porous structure of EG, instead of any chemical action. The DSC results indicated that the phase change temperature and latent heat of the CA–LA–PA and CA–LA–PA/EG were 19.92 °Cand 19.48 °C, and 135.49 J/g and 130.73 J/g respectively. The thermal conductivity of CA–LA–PA /EG composite PCM was improved by the high thermal conductivity of the EG. Thermal cycling test showed that the CA–LA–PA/EG composite had a good thermal reliability. All results indicated that CA–LA–PA/EG composite PCM has a proper melting temperature and latent heat for building energy conservation.

Determination of Parabens in Beverage Samples by Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Droplet

A simple and efficient method for dispersive liquid-liquid microextraction of methylparaben, ethylparaben, propylparaben and butylparaben in real beverage samples was developed. It is making use of solidified floating organic droplets of 1-dodecanol which has low density and a proper melting point. Parameters influencing the extraction efficiency, such as the type of extraction and dispersive solvent, the volume of extraction and dispersive solvent, salt effect, pH, extraction time, were optimized and resulted in enrichment factors (EFs) of 84 for methylparaben, 103 for ethylparaben, 115 for propylparaben and 126 for butylparaben. The limits of detection for parabens were 1.52, 1.06, 0.32 and 0.17 ng/mL, respectively. Excellent linearity with coefficients of correlation from 0.9970 to 0.9997 was observed in the concentration range of 5-1,000 ng/mL. The repeatability of the proposed method expressed as relative standard deviations (RSDs) ranged from 2.54 to 3.89% (n = 5). The relative recoveries for parabens in beverage samples were good and in the ranges of 89.8-109.9, 90.2-107.3, 90.9-101.7 and 92.3-118.1%, respectively. Thus, the proposed method has excellent potential for the determination of parabens in beverage samples.

Preparation and characterization of lauric–myristic–palmitic acid ternary eutectic mixtures/expanded graphite composite phase change material for thermal energy storage

Based on the theoretically calculated mass ratio and the melting temperature of ternary eutectic mixtures, the ternary eutectic mixture of lauric acid (LA), myristic acid (MA) and palmitic acid (PA) was prepared firstly. The differential scanning calorimetry (DSC) results indicated that the eutectic mixture was composed by LA, MA and PA in the ratio of 55.24:29.74:15.02 (by mass). Then the LA–MA–PA was absorbed in expanded graphite (EG), which acts as a supporting material, to prepare six kinds of composite phase change material (PCM). The optimal mass ratio of LA–MA–PA to EG is found. The SEM, FT-IR and DSC comprehensive characterization results show that EG interacted with the capillary tubes and surface tension of LA–MA–PA via its porous structure, instead of any chemical action. At the maximum mass ratio of LA–MA–PA to EG of 18:1 (by mass), the phase change temperature and latent heat of LA–MA–PA ternary eutectic mixture were 31.41°C and 145.8J/g respectively; and the LA–MA–PA/EG composite PCM had a phase change temperature of 30.94°C and a latent heat of 135.9J/g, and the thermal conductivity of the LA–MA–PA/EG was measured as 1.67W/mK, a sharp increase than that of LA–MA–PA. Thermal cycling test showed that the LA–MA–PA/EG composite had a good thermal reliability. Based on all results, it was concluded the prepared LA–MA–PA/EG composite PCM has a proper melting temperature and latent heat for low temperature thermal storage.

Thermodynamic Properties of Caprolactam Ionic Liquids

A series of caprolactam ionic liquids (ILs) containing incorporated halide anions were synthesized. Their physical properties, such as melting points, heats of fusion and heat capacities, were measured by differential scanning calorimeter (DSC). The results indicate that these ionic liquids exhibit proper melting points, high value of heats of fusion, and satisfying heat capacities which are suitable for thermal energy storage applications.

In situ fibrillation of polymeric nucleating agents in polypropylene and subsequent transcrystallization propelled by high-pressure water penetration during water-assisted injection molding

In situ microfibrillar reinforced composites (MFCs) parts of polypropylene (PP) and a special polymeric nucleating agent (acrylonitrile–styrene copolymer, SAN) with four weight ratios (PP/SAN; 98/2, 96/4, 94/6, and 92/8) were molded via water-assisted injection molding (WAIM). The phase morphology and crystalline structure of the WAIM MFCs parts were studied. It was found that high shear stress and cooling rate caused by the high-pressure water penetration during the WAIM could result in the in situ fibrillation of the SAN droplet, followed by the formation of transcrystals at the interface between the SAN microfiber and PP matrix. Moreover, β-form spherulites can be induced by the SAN. The contents of the transcrystals and β-form spherulites were dependent on the SAN content and melt temperature. Interestingly, a WAIM PP/SAN MFCs part with nearly half of its thickness totally dominated by transcrystals and the other half containing high contents of β-form spherulites can be obtained at proper SAN content and melt temperature. This work is expected to provide a promising way to tailor the crystalline structure of the molded parts.

Ultrasound-assisted surfactant-enhanced emulsification microextraction based on the solidification of a floating organic droplet used for the simultaneous determination of six fungicide residues in juices and red wine

A novel ultrasound-assisted surfactant-enhanced emulsification microextraction technique based on the solidification of a floating organic droplet followed by high performance liquid chromatography with diode array detection was developed for simultaneous determination of six fungicide residues in juices and red wine samples. The low-toxicity solvent, 1-dodecanol, was used as an extraction solvent. For its low density and proper melting point near room temperature, the extractant droplet was collected easily by solidifying it at a low temperature. The surfactant, Tween 80, was used as an emulsifier to enhance the dispersion of the water-immiscible extraction solvent into an aqueous phase, which hastened the mass-transfer of the analytes. Organic dispersive solvent typically required in common dispersive liquid–liquid microextraction methods was not used in the proposed method. Some parameters (e.g., the type and volume of extraction solvent, the type and concentration of surfactant, ultrasound extraction time, salt addition, and volume of samples) that affect the extraction efficiency were optimized. The proposed method showed a good linearity within the range of 5μgL−1–1000μgL−1, with the correlation coefficients (γ) higher than 0.9969. The limits of detection for the method ranged from 0.4μgL−1 to 1.4μgL−1. Further, this simple, practical, sensitive, and environmentally friendly method was successfully applied to determine the target fungicides in juice and red wine samples. The recoveries of the target fungicides in red wine and fruit juice samples were 79.5%–113.4%, with relative standard deviations that ranged from 0.4% to 12.3%.

Preparation and thermal energy storage properties of paraffin/calcined diatomite composites as form-stable phase change materials

A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite through the fusion adsorption method. In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined diatomite. The prepared paraffin/calcined diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04°C and 89.54J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value.

Dispersive liquid-liquid microextraction of phenolic compounds using solidified floating organic droplets, and their determination by HPLC

We have developed a simple and efficient method for dispersive liquid-liquid microextraction of 4-nitrophenol, 2-naphthol and bisphenol A in real water samples. It is making use of solidified floating organic droplets of 1-dodecanol which has low density and a proper melting point. The type and volume of extraction solvent and dispersive solvent, the effect of salts, pH value and extraction time were optimized and resulted in enrichment factors of 84 for 4-nitrophenol, 123 for 2-naphthol, and 97 for bisphenol A. The limits of detection by HPLC are 1.50, 0.10 and 1.02 ng · mL−1, respectively. Excellent linearity is observed in the concentration range from 10 to 800 ng · mL−1, with coefficients of correlation ranging from 0.9988 to 0.9999. The relative standard deviations (for n = 5) are from 3.2 to 5.3 %, and relative recoveries for the three phenols in tap, river and spring water range from 85.0 to 105.0 %, 98.3 to 110.0 %, and 98.6 to 109.0 %, respectively.

QuEChERS in Combination with Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction Based on Solidification of Floating Organic Droplet Method for the Simultaneous Analysis of Six Fungicides in Grape

A method for simultaneous analysis of six fungicides in grape was developed by using ultrasound-assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet method (UA-DLLME-SFO) combined with high-performance liquid chromatography equipped with UV detector (HPLC-UV). The extractant was obtained from grape samples using the modified QuEChERS (acronym of quick, easy, cheap, effective, rugged, and safe) method. Then the target fungicides were rapidly transferred from the acetonitrile extract to the phase of 100 μL of 1-undecanol, which is of low density, low toxicity, and proper melting point near room temperature using UA-DLLME-SFO. Experimental parameters affecting the extraction efficiency were studied and optimized. Under the optimum conditions, recovery tests were carried out at three different concentrations. The average recoveries ranged from 72.5 % to 100.6 % with relative standard deviations of 0.8 % to 7.3 % (n = 5). The limits of quantifications of the method for all the target fungicides varied from 0.5 to 5 mg kg−1, which were lower than the MRLs established by Codex Alimentarius Commission and USA. Compared with the conventional method, the proposed method is easy, fast, economic, and less toxic and avoids conventional concentration methods like rotary evaporation and nitrogen stream drying.

Preparation of non-dendritic microstructure of AM60 alloy for rheoforming using self-inoculation method

A rheocasting process, i.e. self-inoculation method (SIM), has been developed for preparing sound semisolid slurry of AM60 alloy. This process involves mixing between alloy melt and particles of solid alloy (self-inoculants in SIM) and subsequent pouring of the mixed melt with a multistream fluid director. Results show that the combined action of self-inoculants and fluid director can create high nucleation and survive rate of the primary α-Mg phase even with high superheat (85°C) in the AM60 alloy. The melt treatment temperature and addition amounts of self-inoculants are the main factors influencing the slurry microstructure. In order to prepare high quality semisolid slurries, proper melt treatment temperature range of 680–700°C and self-inoculants addition range of 5–7% are suggested. The grain multiplication derives from the heterogeneous nucleation induced by self-inoculants and free crystals and dendrite fragments enhanced by the fluid director; globular grain growth and coarsening of particles should be contributed to the microstructure formation.

The Fabrication and Inspection of a Microball Made of Optical Fibre for Micro-Nano Coordinating Measuring Machine

The manufacture of micro-nano three-dimensional (3D) probe is a key factor for Micro-nano Coordinating Measuring Machine (Micro-nano CMM) to achieve the precise measurement. This paper proposes a method to fabricate a microball from an optical fibre using a fibre fusion splicer, which is used for Micro-nano CMM to measure miniature workpieces. Utilizing fused optical fibre tapering and choosing proper melting parameters, a microball with diameter of about 100μm and with roundness of less than 2μm could be fabricated. The offset distance between the microball centre and fibre stylus central line due to the gravity effect could be less than 1μm. This approach not only greatly reduces the time for the preparation of the probe, but also extends micro-nano CMM’s capability of measuring miniature workpieces.

Die attach properties of Zn–Al–Mg–Ga based high-temperature lead-free solder on Cu lead-frame

Several candidate alloys have been suggested as high-temperature lead-free solder for Si die attachment by different researchers. Among them, Zn-Al based alloys have proper melting range and excellent thermal/electrical properties. In this study, Zn-Al-Mg-Ga solder wire was used to attach Ti/Ni/Ag metallized Si die on Cu lead-frame in an automatic die attach machine. Die attachment was performed in a forming gas environment at temperature ranging from 370 to 400 C. At the interface with Cu lead- frame, CuZn4 ,C u 5Zn8 and CuZn intermetallic compound (IMC) layers were formed. At the interface with Si, Al3Ni2 IMC formed when 200 nm Ag layer was used at the die back and AgZn and AgZn3 IMC layers when the Ag layer was 2,000 nm thick. Microstructure of the bulk solder consists of mainly two phases: one with a brighter contrast (about 80.9 wt% Zn) and the other one is a mixture of light (about 73.7 wt% Zn) and dark phases (about 45 wt% Al). Zn-Al-Mg-Ga solder wetted well on Cu lead-frame, covered entire die area and flowed in all directions under the Si die. Less than 10% voids were found in the die attach samples at die attach temperatures of 380 and 390 C. Die shear strength was found within the acceptable limit (21.8-29.4 MPa) for all the die attach temperatures. Die shear strength of standard Pb-Sn solder was also measured for comparison and was found to be 29.3 MPa. In electrical test, maximum deviation of output voltage after 1,000 thermal cycles was found 12.1%.

Study on preparation and thermal properties of binary fatty acid/diatomite shape-stabilized phase change materials

The choice of fatty acids as shape-stabilized phase change materials (PCMs) will increase the feasibilities of PCMs in practical applications due to the low price of the fatty acids. Compounding different fatty acids for each other is an effective way to obtain a PCM with a suitable phase-transition temperature. In this study, a series of binary fatty acids composed by capric acid, lauric acid, palmitic acid and stearic acid for each other were prepared using the phase diagram thermal dynamics calculation method. Then these binary fatty acids are absorbed in four kinds of diatomites with different specific areas, which act as a supporting material, to prepare shape-stabilized PCMs. The prepared shape-stabilized PCMs are characterized by the Scanning electron microscope (SEM) and the differential scanning calorimetry (DSC) analysis method. The results show that there is an optimum absorption ratio between binary fatty acids and the diatomite. The latent heat of capric–lauric acid/diatomite decreases to 57% of that of capric–lauric acid, and the phase-transition temperature rises from 16.36 to 16.74 °C when the capric–lauric acid is absorbed in the diatomite. The prepared capric–lauric acid/diatomite composite PCM has proper melting temperatures and latent heat for thermal energy storage application in buildings.

Dispersive liquid–liquid microextraction based on solidification of floating organic droplet followed by high-performance liquid chromatography with ultraviolet detection and liquid chromatography–tandem mass spectrometry for the determination of triclosan and 2,4-dichlorophenol in water samples

A novel, simple and efficient dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) technique coupled with high-performance liquid chromatography with ultraviolet detection (HPLC–UV) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed for the determination of triclosan and its degradation product 2,4-dichlorophenol in real water samples. The extraction solvent used in this work is of low density, low volatility, low toxicity and proper melting point around room temperature. The extractant droplets can be collected easily by solidifying it at a lower temperature. Parameters that affect the extraction efficiency, including type and volume of extraction solvent and dispersive solvent, salt effect, pH and extraction time, were investigated and optimized in a 5 mL sample system by HPLC–UV. Under the optimum conditions (extraction solvent: 12 μL of 1-dodecanol; dispersive solvent: 300 of μL acetonitrile; sample pH: 6.0; extraction time: 1 min), the limits of detection (LODs) of the pretreatment method combined with LC–MS/MS were in the range of 0.002–0.02 μg L −1 which are lower than or comparable with other reported approaches applied to the determination of the same compounds. Wide linearities, good precisions and satisfactory relative recoveries were also obtained. The proposed technique was successfully applied to determine triclosan and 2,4-dichlorophenol in real water samples.

Improvement in melting and baking properties of low-fat Mozzarella cheese

Low-fat cheeses dehydrate too quickly when baked in a forced air convection oven, preventing proper melting on a pizza. To overcome this problem, low-fat Mozzarella cheese was developed in which fat is released onto the cheese surface during baking to prevent excessive dehydration. Low-fat Mozzarella cheese curd was made with target fat contents of 15, 30, 45, and 60g/kg using direct acidification of the milk to pH 5.9 before renneting. The 4 portions of cheese curd were comminuted and then mixed with sufficient glucono-δ-lactone and melted butter (45, 30, 15, or 0g/kg, respectively), then pressed into blocks to produce low-fat Mozzarella cheese with about 6% fat and pH 5.2. The cheeses were analyzed after 15, 30, 60, and 120 d of storage at 5°C for melting characteristics, texture, free oil content, dehydration performance, and stretch when baked on a pizza at 250°C for 6min in a convection oven. Cheeses made with added butter had higher stretchability compared with the control cheese. Melting characteristics also improved in contrast to the control cheese, which remained in the form of shreds during baking and lacked proper melting. The cheeses made with added butter had higher free oil content, which correlated (R2≥0.92) to the amount of butterfat added, and less hardness and gumminess compared with the control low fat cheese.

Effects of Nucleators on the Thermodynamic Properties of Seasonal Energy Storage Materials Based on Ionic Liquids

Seasonal energy storage based on phase-change materials (PCMs), long-chain alkylimidazolium bromide ionic liquids [C16MIM]Br and [C16MMIM]Br, are investigated in this paper. The structures of ionic liquids are measured by infrared (IR) spectra. Thermodynamic properties of ionic liquids, such as melting/freezing temperature and endothermic/exothermic heat, are measured by differential scanning calorimetry (DSC). The active use of supercooling of ionic liquids is proposed, which means that the thermal energy is stored in a supercooled liquid state and released by nucleating agents when needed. Copper powder and graphite powder, used as nucleating agents, are added with different mass fractions (0−25 wt %), and their effects on the thermodynamic properties of two ionic liquids are investigated. The results show that the nucleating agents have little effect on the thermodynamic properties of ionic liquids. The degree of supercooling of [C16MIM]Br is maintained at about 20 K when copper powder or graphite powder is added. The proper melting point and stable supercooling state of [C16MIM]Br indicates that it is more suitable for seasonal energy storage.

Clad Strip Casting Using a Twin Roll Casters

The three layers clad strip was fabricated by a vertical type tandem twin roll caster for clad strip (VTTCC). The effect of the casting conditions of the base strip and the overlay strip on the interface between the base strip and the overlay strip was investigated. The temperature of the molten metal and roll-load were investigated casting conditions. Base strip was AA8079 and overlay strip was AA6022. The proper melt temperature of the overlay strip was around the liquidus line of the base strip. The proper roll-load, which was smaller than rolling, was existed.

Casting of Clad Strip by a Roll Caster

The three layers clad strip was fabricated by a tandem positioned vertical type twin roll casters. The effect of the casting conditions of the overlay strip on the interface between the base strip and the overlay strip was investigated. The temperature of the molten metal, roll-load and solidification length were chosen as the casting conditions. Base strip was AA8079 and overlay strip was AA6022. The proper melt temperature of the overlay strip was above the liquidus line of the base strip. The proper roll-load, which was lower than rolling, was existed. There was not clearance at the interface when the solidification length was appropriate.

A novel method for the determination of trace copper in cereals by dispersive liquid–liquid microextraction based on solidification of floating organic drop coupled with flame atomic absorption spectrometry

Abstract A novel, simple, rapid, efficient and environment-friendly method for the determination of trace copper in cereal samples was developed by using dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) followed by flame atomic absorption spectrometry. In the DLLME-SFO, copper was complexed with 8-hydroxy quinoline and extracted into a small volume of 1-dodecanol, which is of low density, low toxicity and proper melting point near room temperature. The experimental parameters affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, the calibration graph exhibited linearity over the range of 0.5–500 ng/mL with the correlation coefficient ( r ) of 0.9996. The enrichment factor was 122 and the limit of detection was 0.1 ng/mL. The method was applied to the determination of copper in the complex matrix samples such as rice and millet with the recoveries for the spiked samples at 5.0 and 10.0 μg/g falling in the range of 92.0–98.0% and the relative standard deviation of 3.9–5.7%.

Development of Anti-entrapment Mould Flux which Crystallizes into Melilite as a Main Phase

Two characteristics, high basicity and high viscosity, are required for the anti-entrapment mould flux. However, it had been difficult to apply the high basicity and high viscosity mould flux for a round billet casting because of heat flux fluctuations in the mould.We supposed that the heat flux fluctuations were caused by unstable crystallization of the flux film between the mould and the solidified shell. Assuming that the contaminating constituents which do not compose the main crystal phase bring the unstable crystallization of the flux film, we have researched an adequate main crystal for the high basicity and high viscosity mould flux which has proper composition and melting point. As a result, there was no proper single crystal, but we have found an adequate combination of two crystals, gehlenite and akermanite. These two crystals have similar constructions each other to make a solid solution, melilite. Melilite behaves as a single phase crystal as well as it can take any compositions between gehlenite and akermanite. These properties of melilite diminish restraints on mould flux design.Consequently, we have successfully developed the anti-entrapment mould flux for the round billet casting, achieving a result to reduce mould flux defects effectively.