Low Temperature Viscosity Research Articles

Equilibrium viscosity and structural change in the Cu47.5Zr45.1Al7.4 bulk glass-forming liquid

The low temperature viscosities of Cu47.5Zr45.1Al7.4 glass-forming liquid are measured by thermomechanical analysis in three-point beam bending mode. The experimental equilibrium values are fitted with the Vogel-Fulcher-Tammann (VFT) function, and the fragility parameter of the supercooled liquid is determined to be D* = 20.6. Viscosity measurements during isothermal annealing at 710 K show an initial relaxation from the glassy state into the supercooled liquid, followed by an anomalous viscosity increase of about two orders of magnitude. In-situ transmission electron microscope (TEM) and spherical aberration-corrected TEM investigations reveal that the effects of primary crystallization, nanoscale decomposition and structural ordering might be responsible for the anomalous viscosity behavior. The change in dynamic properties of the supercooled liquid, which is reflected by the larger VFT fitting parameter D* = 41.9 of the new annealed state reached before the final crystallization, is suggested to be not only related to the nanoscale structure change, but may also be caused by the change in chemical composition of the new annealed glass due to the primary crystallization. Furthermore, possible mechanisms for the nanoscale phase separation and the formation of atomic clusters are discussed based on the results of high-resolution TEM experiments.

Binary mixtures of ionic liquids based on EMIm cation and fluorinated anions: physico-chemical characterization in view of their application as low-temperature electrolytes

Binary mixtures of ionic liquids (ILs) consisting of 1-ethyl-3-methylimidazolium [EMIm]+ cation coupled with fluorinated anions: bis(fluorosulfonyl)imide [FSI]-, bis(trifluoromethanesulfonyl)imide [TFSI]- and tetrafluoroborate [BF4]-, were formulated to obtain ionic fluids which are liquid at low temperature and to understand their properties. The thermal behaviour of [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x) mixtures with various molar ratios of IL components was investigated with differential scanning calorimetry (DSC). They exhibited reduced enthalpy of the phase transitions and lower melting temperature compared to the parent ILs, or only vitrification/devitrification occurring below −90 °C in some cases where x ranges from 0.5 to 0.8, 0.1 to 0.6 or 0.2 to 0.8 for [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x), respectively. For the formulations showing solely a glass transition, considered to be prospective low-temperature electrolytes, the density, viscosity and conductivity values were determined in a wide temperature range. The density demonstrated linear temperature dependence, whilst the dynamic viscosity and ionic conductivity followed the Vogel-Tamman-Fulcher equation. The corresponding Walden plot for pure ILs and their mixtures revealed a high degree of ionicity classifying them as “good ionic liquids” even down to −25 °C. The [EMIm][FSI]x[BF4](1-x) mixtures with x ranging from 0.5 to 0.6 displayed the lowest viscosity and highest conductivity, indicating them as promising electrolytes for IL-based electrochemical capacitors operating at low temperature, down to at least −40 °C.

Application of Sulfated Tin (IV) Oxide Solid Superacid Catalyst to Partial Coupling Reaction of α-Pinene to Produce Less Viscous High-Density Fuel

Brønsted acid-catalyzed reactions of α-pinene have been studied because of their ability to produce various types of fragrance molecules. Beyond this application, dimeric hydrocarbon products produced from coupling reactions of α-pinene have been suggested as renewable high-density fuel molecules. In this context, this paper presents the application of a sulfated tin(IV) oxide catalyst for the partial coupling reaction of α-pinene from turpentine. Brønsted acid sites inherent in this solid superacid catalyst calcined at 550 °C successfully catalyzed the reaction, giving the largest yield of dimeric products (49.6%) at 120 °C over a reaction time of 4 h. Given that the low-temperature viscosity of the mentioned dimeric products is too high for their use as a fuel in transportation engines, lowering the viscosity is an important avenue of study. Therefore, our partial coupling reaction of α-pinene provides a possible solution as a considerable amount of the isomers of α-pinene still remained after the reaction, which reduces the low-temperature viscosity. On the basis of a comparison of the reaction products, a plausible mechanism for the reaction involving coinstantaneous isomerization and coupling reaction of α-pinene was elucidated.

Chemorheological behaviors of TDE-85 toughened by low viscosity liquid epoxy for RTM process

In this study, 1,4-cyclohexanedimethanol diglycidyl ether (EP-1) has been synthesized via a two-step process to toughen and lower the viscosity of TDE-85 epoxy first time and suitable for the resin transfer molding (RTM) process. Chemical structure of EP-1 and the reactivity, rheological and mechanical properties of TDE-85/MeTHPA/DMP-30/EP-1 system were studied. When the composition ratio of TDE-85/MeTHPA/EP-1/DMP-30 is 100: 140: 15: 1 and the curing process is 80 °C/2 h + 110 °C/2 h + 140 °C/2 h, the overall performance of the resin system reached to an optimal value. Impact and bending strength of the casting came out to be 27.64 kJ m−2 and 167.2 MPa, which improved 75.16% and 17.50% respectively compared to the pristine resin system without EP-1. Dynamic viscosity analysis of TDE-85/MeTHPA/DMP-30/EP-1 system showed that the viscosity-temperature curve was U-shaped and the platform zone was located around 60–95 °C during which the viscosity was less than 200 mPa s. Dual-Arrhenius and engineering viscosity models were established to predict the viscosity characteristics of the resin. It was found that the dual-Arrhenius model matched better with the experimental data at low temperature and low viscosity region. Whereas when the viscosity increased, the engineering viscosity model became more accurate. The viscosity analysis provided the basis for the window prediction of RTM molding process.

Leveling of Polymer Grating Structures upon Heating: Dimension Dependence on the Nanoscale and the Effect of Antiplasticizers.

The transition temperatures of nanoscale polymeric films are measured from a leveling experiment where a designed nanostructure is heated from below. Surface tension forces drive the relaxation of the polymeric features, allowing direct measurement of the critical temperature of collapse, Tflow, and indirect measurement of the glass transition temperature, TG. Small-angle X-ray scattering and atomic force microscopy are used to follow the leveling dynamics, whereas a mathematical model for the momentum balance is implemented to extract the viscosity of the polymer film as a function of temperature. Our methodology is illustrated in the context of films of poly(methyl methacrylate) that are patterned via nanoimprint lithography into dense gratings. We study how the glass transition temperature and the critical temperature of collapse vary as a function of the film size and the inclusion of the antiplasticizer, tris(2-chloropropyl) phosphate. The grating periods are varied consistently between 80 and 240 nm, whereas the antiplasticizer concentrations are 1, 3, 5, and 10 wt %. The solution of the momentum balance allows the detailed correlation between stresses, curvature, heating, and shear rates during leveling. We found that both temperatures, TG and Tflow, decrease as the film size decreases or as the concentration of the antiplasticizer increases. In addition, antiplasticizer concentrations between 3 and 5 wt % stabilize the size dependence of Tflow. We show that the nature of the antiplasticizer is effectively to increase the low-temperature viscosity of the film. However, during leveling, the antiplasticized film sustains its curvature, thereby driving a sudden relaxation, once TG is reached, and increasing the possibilities of defects.

Activated Low-Temperature Viscosity Breaking of Heavy Oil with Additives of Iron Particles and Asphaltene and Paraffin Deposits

The effect of iron-containing solid wastes from metal working, asphaltene and paraffin deposits, and that of an electromagnetic field on activated low-temperature viscosity breaking of bituminous oil has been studied. It has been found that the use of additives and an electromagnetic field makes it possible to reduce the temperature of oil cracking to 397°C, increase the yield of light petroleum products (gasoline, diesel, and gas oil fractions), and increase the quality of produced fractions.

Effects of potassium fertilization on potato starch physicochemical properties

Potato starch serves as an excellent raw material or food additive in the food industry. With the advancement of the potato staple food strategy in China, improving the potato starch yield and quality has attracted more and more attention. Potassium is an essential nutrient for potato due to its direct effects on the yield and quality of potato tubers. Here, the effects of three different potassium levels on potato starch physicochemical properties were evaluated by field experiments. With increasing potassium fertilization rates, the amylose content, phosphorus content and particle size decreased, thereby resulting in low gelatinization temperature, breakdown and setback viscosity, and high swelling power, relative crystallinity and transparency. Our study indicated that enhanced potassium fertilization improved the resistance to heat and shear stress and decreased the retrogradation of starch, and the 270 kg/ha potassium fertilization rate could obtain the highest tuber and starch production with desirable starch physicochemical properties. The integrated results also provide some novel insights into the management of the fertilization conditions to obtain native starches with special properties.

Response surface models for synthetic jet fuel properties

Jet fuel is a mixture of different hydrocarbon groups, and the mass contribution of each of these groups toward the overall chemical composition of the fuel dictates the bulk physical properties of the fuel after completion of the refining and blending processes. The fluidity properties of jet fuel mixtures at low temperatures are critical in understanding and mitigating the safety risks and performance attributes of aircraft engines, which may lead to the introduction of more stringent specification limits in the near future. Therefore, in this study the low-temperature viscosity and freeze point properties of jet fuels were investigated by variation of the linear to branched chain paraffin mass ratio, in conjunction with variation of the carbon number distribution according to a mixture by process variables experimental design. Furthermore, response surface models were developed and discussed for the two main fluidity properties of interest and inferences were made from the models for the potential generation of optimal jet fuel mixtures.

Ignition and Combustion Performances of High-Energy-Density Jet Fuels Catalyzed by Pt and Pd Nanoparticles

High-energy-density fuels are critical for supersonic aerospace propulsion, but they suffer from the difficulties of ignition and low level of combustion completion. This research reports Pt and Pd nanoparticles (NPs)-assisted ignition and combustion of a high-energy-density JP-10 fuel. Pt and Pd NPs in the 2 to 8 nm size range were synthesized and dispersed in JP-10 to form homogeneous suspended mixtures. The mixtures were stable for over two years, and the Pt and Pd NPs did not precipitate after high speed centrifugation. The presence of Pt and Pd NPs almost had no influence on the viscosity and density of the JP-10 fuel samples, and both the Pt NPs/JP-10 and Pd NPs/JP-10 fuels showed good low temperature viscosities. The shock tube test results showed that Pt and Pd NPs can effectively improve the ignition and combustion performances of JP-10 fuel because Pt and Pd NPs can reduce the apparent ignition activation energy of JP-10. In comparison with the apparent activation energy of pure JP-10 fuel, the ...

Hot embossing of polypropylene micro-tubes into functional tubular components with controlled inner-pore sizes

To meet ever-increasing demands on the micro-components for medical and non-medical applications, a new micro-shaping technology - “hot embossing of micro-tubes”, had been developed for the forming of polymeric tubular micro-components. The paper presents the results from the forming of Polypropylene(PP) micro-tubes with outer diameters of 1.3mm and inner diameters 0.6mm, to achieve various reduced inner-features. The study was effected by combining experiment, numerical simulation and SEM analysis. FE simulation was implemented by using the material data obtained from the material characterisation tests. The forming experiment was conducted with a high-precision hot-embossing machine, developed in-house, with automated handling and good reliability and repeatability. The Polypropylene (PP) micro-tubes were successfully formed into the desired features at the temperatures of 60°C and 100°C respectively. The influences of the parameters/factors, such as tool design, temperature, forming pressure and holding time, on the quality of the shaped parts, are discussed in details. Based on this study, it is concluded that PP is an ideal candidate material among the polymeric materials for hot embossing of tubular micro-components, due to its good ductility, low transition temperature and low viscosity. Keywords: Micro forming, Manufacturing process, Tool geometry

An evaluation of neat biodiesel/diesel performance, emission pattern of NOx and CO in compression ignition engine

Oxides of nitrogen (NOx) and carbon (II) oxide (CO) emissions from engine running on pure biodiesel constitute one of the environmental challenges to its application as fuel. Verifying their sources and production pattern is an essential first step to tackling the challenge. 100% biodiesel derived from moringa, jatropha and waste oil along with petroleum diesel were evaluated in a single cylinder diesel engine. It was observed that oxygen concentration and combustion temperature are the primary drivers of a kinetically determined process. NOx emission trended with Zeldovich mechanism prediction and thus increases with increasing O2 concentration and temperature. CO2 dissociation at elevated combustion temperature in a suppressed O2 concentration regime governs CO production for normal diesel running at high load but, low temperature and high viscosity account for same effect in biodiesel runs. CO therefore increases with increasing temperature and decreasing O2 concentrations for petroleum diesel but for biodiesel, the reverse is the case. Novel exhaust gas recirculation (EGR) and low temperature combustion (LTC) engine therefore holds the key to unlocking biodiesel potential and remediating some of the difficulties observed with petroleum diesel.

ЗАКАЛКА С ПОСЛЕДУЮЩИМ ОБОГАЩЕНИЕМ УГЛЕРОДОМ НЕПРЕВРАЩЕННОГО АУСТЕНИТА (Q&P ОБРАБОТКА) МАРТЕНСИТНОЙ КОРРОЗИОННОСТОЙКОЙ СТАЛИ AISI 414

Heat treatment consisting quenching of steel to a temperature inside the martensitic transformation interval with subsequent carbon partitioning between quenched martensite and retained austenite (Q&P treatment) is applied to martensitic stainless steel AISI 414 (Fe – 0.14 % C – 12.5 % Cr – 2.3 % Ni). Q&P processing was modeled using the thermomechanical simulator Gleeble 3800. Phase transformations during processing were studied using a contact dilatometer, which measures the change in the specimen diameter at the thermocouple spot. After austenitization at 1150 °C for three minutes, the temperature of the onset of the martensitic transformation of the steel under study was 270 °C. To implement Q&P processing, the samples were quenched to temperatures of 250 °C, 200 °C, 150 °C and 100 °C. The carbon partitioning between the quenched martensite and untransformed austenite was carried out in the process of 3-minute exposure at 450 °C. It has been shown that quenching to temperatures of 200–250 °C with subsequent annealing at 450 °C does not ensure the enrichment of unconverted austenite with carbon, sufficient to suppress martensitic transformation upon subsequent cooling to room temperature. Lowering the quenching temperature to 150 °C with subsequent annealing at 450 °C leads to complete thermal stabilization of the untransformed austenite up to temperatures of minus 60 °C, which ensures a high lowtemperature toughness of the steel under investigation through the TRIP effect, exceeding the values laid down in the requirements for high-strength pipe steel. The conclusion is made about the prospect of Q&P processing of the investigated steel for obtaining a high-strength state with a high level of low-temperature viscosity.

Indications for a fragile-to-strong transition in the high- and low-temperature viscosity of the Fe43Cr16Mo16C15B10 bulk metallic glass-forming alloy

Viscosity of the Fe-based bulk metallic glass-forming liquid Fe43Cr16Mo16C15B10 is measured around the glass transition and in the stable liquid. Low-temperature measurements are conducted using three-point beam bending in a thermomechanical analyzer, and high-temperature data are obtained from the damping behavior of an oscillating droplet which is electromagnetically levitated in microgravity on a reduced-gravity aircraft. The alloy displays an intermediately strong liquid behavior (D* = 15.1) at low temperatures and a fragile behavior (D* = 7.9) at high temperatures. Hence, the temperature dependence of viscosity changes drastically between the high- and the low-temperature regime, which suggests the existence of a fragile-to-strong liquid-liquid transition in the supercooled liquid. Furthermore, viscosity and fragility data are discussed with respect to the glass-forming ability of the alloy.

Mixing times of organic molecules within secondary organic aerosol particles: a global planetary boundary layer perspective

Abstract. When simulating the formation and life cycle of secondary organic aerosol (SOA) with chemical transport models, it is often assumed that organic molecules are well mixed within SOA particles on the timescale of 1 h. While this assumption has been debated vigorously in the literature, the issue remains unresolved in part due to a lack of information on the mixing times within SOA particles as a function of both temperature and relative humidity. Using laboratory data, meteorological fields, and a chemical transport model, we estimated how often mixing times are < 1 h within SOA in the planetary boundary layer (PBL), the region of the atmosphere where SOA concentrations are on average the highest. First, a parameterization for viscosity as a function of temperature and RH was developed for α-pinene SOA using room-temperature and low-temperature viscosity data for α-pinene SOA generated in the laboratory using mass concentrations of ∼ 1000 µg m−3. Based on this parameterization, the mixing times within α-pinene SOA are < 1 h for 98.5 % and 99.9 % of the occurrences in the PBL during January and July, respectively, when concentrations are significant (total organic aerosol concentrations are > 0.5 µg m−3 at the surface). Next, as a starting point to quantify how often mixing times of organic molecules are < 1 h within α-pinene SOA generated using low, atmospherically relevant mass concentrations, we developed a temperature-independent parameterization for viscosity using the room-temperature viscosity data for α-pinene SOA generated in the laboratory using a mass concentration of ∼ 70 µg m−3. Based on this temperature-independent parameterization, mixing times within α-pinene SOA are < 1 h for 27 and 19.5 % of the occurrences in the PBL during January and July, respectively, when concentrations are significant. However, associated with these conclusions are several caveats, and due to these caveats we are unable to make strong conclusions about how often mixing times of organic molecules are < 1 h within α-pinene SOA generated using low, atmospherically relevant mass concentrations. Finally, a parameterization for viscosity of anthropogenic SOA as a function of temperature and RH was developed using sucrose–water data. Based on this parameterization, and assuming sucrose is a good proxy for anthropogenic SOA, 70 and 83 % of the mixing times within anthropogenic SOA in the PBL are < 1 h for January and July, respectively, when concentrations are significant. These percentages are likely lower limits due to the assumptions used to calculate mixing times.

Structurally uniform 1-hexene, 1-octene, and 1-decene oligomers: Zirconocene/MAO-catalyzed preparation, characterization, and prospects of their use as low-viscosity low-temperature oil base stocks

An original approach to α-olefin oligomerization as well as novel thermally stable zirconocene catalysts for use in such reactions has been elaborated. The method reported allows the achievement of fractions of lightweight α-olefin oligomers up to 90% yields without considerable formation of byproducts like internal alkenes, alkanes, and higher oligomers. Trimers, tetramers, and pentamers of 1-hexene, 1-octene, and 1-decene were isolated as individual compounds and were hydrogenated. Viscosity characteristics of the isolated saturated and unsaturated hydrocarbons have been studied at various temperatures. The isolated saturated oligomers of 1-octene and 1-decene outperform the traditional electrophilic oligomerization products in terms of viscosity indexes, pour points, and low-temperature viscosity.

Viscosity and configuration entropy of glasses for CHROMPIC vitrification

The composition and temperature dependence of viscosity and configuration entropy of glasses with chemical composition close to that used for CHROMPIC radioactive waste vitrification were studied. The composition of fifteen studied glasses was derived from the composition of currently used glass frit by increasing/decreasing the content of each particular oxide and retaining the same relative amounts of the other components. The high-temperature viscosity in the range (101.8–103.0) dPa s was measured by the falling ball method while the low-temperature viscosity in the range (108–1012) dPa s was measured by the thermomechanical analysis. The experimental viscosity data were smoothed by the Vogel–Fulcher–Tammann viscosity equation. The temperature–composition dependence of viscosity was described by the Adam and Gibbs viscosity equation. The influence of increasing/decreasing content of particular oxides on the values of parameters of the Adam and Gibbs viscosity equation and on the value of configuration entropy was quantified and discussed.

Molecular Design and Characterization of High-Cetane Alkyl Diamondoid Fuels

Four alkyl diamondoids, 1-pentyladamantane (PA), 2-butyladamantane (BA), 2-propyladamantane (2-PrA), and 2-ethyladamantane (EA), were synthesized on a preparative scale, and key fuel properties, including density, net heat of combustion, low-temperature viscosity, and derived cetane number (DCN), were measured. The fuel molecules had densities up to 17% higher than conventional jet fuel and volumetric net heats of combustion comparable to or exceeding that of the synthetic missile fuel JP-10. Remarkably, the alkyl diamondoid fuels had DCNs in the range of 42–49, which should allow for their efficient combustion in diesel engines. PA, BA, and 2-PrA all had essentially the same DCN (∼49), while the short alkyl chain in EA lowered the value to 42.7. Bond dissociation energies for the formation of diradicals from 2-PrA and PA were calculated with density functional theory methods to gain a qualitative understanding of potential combustion mechanisms. Ring opening of the adamantane core during combustion is pr...

Viscosity of pantelleritic and alkali-silicate melts: Effect of Fe redox state and Na/(Na + K) ratio

The viscosity of two series of synthetic alkali silicates, corresponding to Al-bearing pantelleritic and Al-free tri-silicate compositions, has been investigated as a function of temperature, iron redox and Na/(Na+K) ratio. Low temperature (708–1000K) viscosities were determined by the micropenetration technique in the 109.6 to 1013.6Pas range. The effect of Fe2+/Fetot, from 0.15 to 0.86, was explored for [Na/(Na+K)] ratios from 0 to 1. The results demonstrate a strong decrease of viscosity with the replacement of Na for K in both the Al-bearing and Al-free compositions. In the Al-bearing pantelleritic glasses (Ebu) the viscosity as well as the activation energy for viscous flow decrease with an increase of Fe2+/Fetot from 0.15 to 0.76. In contrast, no measurable changes in viscosity occur in the Al-free tri-silicate glasses (NFS and KFS) as Fe2+/Fetot ratio varies from 0.15 to 0.86. The comparison of the pantelleritic glasses with peralkaline compositions from the literature stresses the strong influence of iron redox on the overall viscosity of such melts. This suggests that the contribution of iron species should be accounted for in the calculation of agpaitic index (AI) if magma Fe3+ contents are known.One peculiarity of peralkaline magmas is the excess of alkali to alumina, which generally results in lower viscosities of pantelleritic liquids compared with more common metaluminous rhyolites and exerts a primary control of the rheological behaviour of these melts.Our new viscosity data, combined with existing literature, allow more accurate constraints on the nature and eruption of the pantelleritic magmas. Moreover, the present experimental study can be used to improve the viscosity models that mostly do not take in consideration parameters as iron redox in the viscosity prediction.

Low-temperature magnetic viscosity in thin GaMnSb films containing MnSb clusters

The time dependences of the magnetic moment m(t) of thin GaMnSb films containing MnSb clusters are measured. It is found that the m(t) curves are straight in semilogarithmic coordinates m(lnt). The slope of the m(lnt) lines correspond to the magnetic viscosity S. It is found that the field dependences of the magnetic viscosity S(H) and magnetic moment m(H) at low temperatures are determined by a log-normal distribution of the magnetic anisotropy energy of the MnSb clusters.

Effect of poly-alpha-olefin pour point depressant on cold flow properties of waste cooking oil biodiesel blends

Improving the flow ability at a low temperature is vital for the utilization and popularization of biodiesel. The cold flow properties of waste cooking oil biodiesel–0# diesel blends with poly-alpha-olefin (PAO) pour point depressants were studied. Here results showed that B20 (20vol.% biodiesel-80vol.% diesel) treated with 400ppm PAO exhibited the best depression in cloud point, cold filter plugging point and pour point by 8°C, 9°C and 7°C, respectively. The other fuel properties of B20 were also determined and compared with the limits indicated in the ASTM D7467 standard. Viscosity–temperature curves, polarized optical microscopy, low-temperature X-ray diffraction, and differential scanning calorimetry were used to explore the performance mechanism of PAO in biodiesel blends; and results presented that PAO could effectively lower the low-temperature viscosity, delay the aggregation of wax crystals and modify their crystallization behavior by transforming the shape of crystals and depressing the formation of large wax crystals.