Kinds Of Mixtures Research Articles

Corrosion Resistant Alloys for Phosphoric Acid Production and Storage

This paper addresses the topic of material selection for several parts of the phosphoric acid production chain, focusing essentially on corrosion resistant alloys and life cycle cost. During the phosphate attack by sulfuric acid, the vessel can be susceptible to corrosion due to the presence of an aggressive slurry which consists of a mixture of phosphoric acid, sulfuric acid, chlorides and hydrofluoric acid. This study reports the results of corrosion tests performed on various stainless steels in this kind of mixture at 80°C and 110°C, corresponding to the temperature of the di-hydrate and hemi-hydrate processes, respectively. From this study, it is highlighted that the super-duplex stainless steel 2507Cu / UNS S32550 (25% chromium, 7% nickel) can be recommended for phosphoric acid production provided that the temperature does not exceed 80°C. This alloy also offers a good resistance to abrasion and may allow the design engineer to decrease the wall thickness thanks to its high mechanical properties. If the temperature is higher than 110°C, materials containing more alloying elements must be selected, like alloy 31 / UNS N08031 or alloy 28 / UNS N08028. For phosphoric acid transportation and storage, the behavior of various stainless steels is also investigated. The influence of several levels of chloride contamination on the corrosion rates is considered. The results reveal that the duplex steel 2202 / UNS S32202 (22% chromium, 2% nickel) is a cost-efficient alternative to conventional austenitic stainless steels, offering better mechanical properties and corrosion resistance in the presence of chlorides.

Integrated Process-Product Design based on COSMO-SAC model: Application to the Production of 2,2,4-Trimethyl-1,2-H-Dihydroquinoline (TMQ)

TMQ (2,2,4-trimethyl-1,2-H-dihydroquinoline) is a widely used and effective antioxidant in rubber production technologies. Its product is a kind of mixture which mainly consists of oligomers such as dimer, trimer and tetramer. The quality of TMQ is determined by the content of oligomers, especially dimer. This paper presents a systematic computer-aided molecular design (CAMD) methodology for designing optimal solvents for the synthesis of TMQ reaction system where the function of such solvents is to enhance the yield by optimal selectivity of reaction and extraction of TMQ products. In this work, we proposed an integrated process-product design framework of reaction and extraction solvent design for TMQ product. In this framework, a decomposition-based method is presented, which involves an integrated property estimation method combined group contribution methods with COSMO-SAC (COnductor-like Screen MOdel for Segment Activity Coefficient) and a process model of chemical and phase equilibrium. The results show that the designed solvents are able to improve the yield of dimer.

Characterisation of Polyamide (PA)12 Nanocomposites with Montmorillonite (MMT) Filler Clay Used for the Incremental Forming of Sheets

In this paper, the preparation and characterisation of polymer materials suitable for single point incremental forming (SPIF) technology were performed. Three different kinds of mixtures were selected: a mixture of neat polyamide 12 (PA12), a nanocomposite with PA12 matrix and 1% clay (Cloisite 93A), and a nanocomposite with PA12 matrix and 3% clay (Cloisite 93A). Materials were produced using a melt intercalation method followed by compression moulding. According to the needs of SPIF technology, morphological and mechanical properties were investigated in the obtained mixtures. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize morphological properties. It was determined that the most desired obtained exfoliated structure of clay in the polymer matrix was achieved. Static tensile testing and dynamic mechanical analysis as well as the determination of glass transition temperature and crystallinity of all analysed materials were used to obtain mechanical and thermal properties of the mixtures. The results obtained for each mixture were compared with respect to the content of clay. The content of clay (Cloisite 93A) showed a strong influence on the properties of the obtained materials. The presence of clay (Cloisite 93A) affected the increase of tensile strength and Young’s modulus, while its influence on the attained elongation was not unique.

A New Intelligent Model for Computing Crack in Compacted Soil-Biochar Mix: Application in Green Infrastructure

There have been studies analysing water retention and cracking in soil-biochar mix, but there is lack of model for estimating cracking in these kind of mixture. These models can be useful as it can be directly inputted in governing equations of seepage analysis for further analysing stability of green infrastructure. The objective of this study is to develop a model for computing crack as function of water content, suction and biochar content. Neural network-based modelling was adopted to achieve the objective. A series of experiments were conducted to quantify cracking in soil biochar composite using a novel crack intensity factor as a function of water retention and soil suction in five different soils with varying biochar content (i.e., 0%, 2%, 5%, 10% and 15%). The biochar was obtained from an invasive weed (i.e., Water hyacinth). The data obtained from the experimental study was then used for developing model using Artificial neural networks (ANN) technique. A single ANN model was developed and validated with the testing data. The model was found to give satisfactory performance. This model can be useful in improving the water balance calculation in green infrastructure as well as agricultural fields (subjected to extreme drying-wetting season).

Study of the Change of the Specialists' Isolative Garment Properties Against the Effects of Peroxide Decontamination Mixture

Abstract The influence of the peroxide decontamination mixture on the barrier polymeric material used for the construction of the anti-gas protective garment OPCH-05 has been study. This kind of mixture is used with the help of the decontamination vehicle ACHR-90 and its EDS mixture. The both soldiers and operators of the ACHR-90 or the EDS mixture can be in a direct contact with spattering decontamination mixture that can cause significant damages of the anti-gas protective garment OPCH-05. For evaluation of protective properties and their potential changes the MIKROTEST method and methodology has been used. This paper is another publication which deals with the influences of decontamination mixtures introduced in the Czech Armed Forces Chemical Corps armament on the barrier material composed of the butyl-rubber polymeric mixture in combination with the polyamide textile.

Durability of mortars with leftover recycled sand

Abstract This study presents the durability of mortars made with leftover recycled sand. In order to take the outside storage of this young concrete into consideration, with its ensuing carbonation, two series of recycled sands are studied, one non-carbonated and the other carbonated. First, all the basic characteristics, such as water absorption, density, cement content, and thermogravimetric characteristics of the sands and their fractions are studied. Since the idea of recycling leftover sand is still new and not much studied, an indepth study of its fractions is necessary. The results show that recycled sand presents two layers: an old cement paste layer and a natural sand layer. It is the old cement paste layer that varies with the size and fractions, influencing the characteristics of the sands and the durability of their mortars. Second, many indicators of durability are studied (strength, air permeability, chloride ion migration, capillarity, carbonation and porosity accessible to water) according to the mortar composition, and are compared with those of reference mortars made with natural sand. The results demonstrate that, for both kinds of mixtures, the durability range is very close to the reference. However, a marked increase of durability was observed through the chloride ion migration index of the mortar with carbonated recycled sand. It can also be underlined that the mixture with carbonated recycled sand showed equal or even better performances than non-carbonated sand (better compressive strength index, migration index and carbonation index). Overall, this study demonstrates that the recycling of these kinds of leftover sand is possible.

Understanding structure and dynamics of organic liquid mixtures by molecular simulations

The structure and dynamics of acetonitrile and its mixtures with toluene and water in the whole composition range are investigated by molecular dynamics simulations with several combinations of empirical non-polarizable force fields. The acetonitrile and toluene binary system has been theoretically studied for the first time. One existing force field combination leads to unphysical phase separation in the mixture of acetonitrile with water. Densities, excess molar volumes, dielectric constants, viscosities and self-diffusion coefficients obtained by more suitable force fields are systematically compared with experimental data. For static properties, it is possible to get nearly quantitative agreement for both kinds of mixtures. The evaluation of the dielectric constant illustrates the importance of including the purely electronic component of polarization. The right trends for dynamical properties are captured. The arrangement of the closest acetonitrile molecules is antiparallel in the neat liquid, those with slightly larger separation of molecular centers orientate with respect to each other in various ways without strong preference for any of them. The addition of toluene causes structuring of acetonitrile and enhances the preference of antiparallel arrangement. Water has a smaller effect on the acetonitrile radial distribution functions, but it affects the preferences for individual arrangements.

Graphene-based field effect transistor with ion-gel film gate

Graphene is a kind of two-dimensional material with high light transmittance, high mechanical properties and high carrier mobility. The energy band of graphene can be turned by doping and electric field. Researches on the application of graphene to electronic devices focused on field effect transistors. For improving the performance, one generally improves the fabrication process and device structure, but many researchers chose to change the material or structure of dielectric layer. Ion-gel is a kind of mixture of organic polymer mesh structure with good thermal stability and high dielectric value, prepared by macromolecule organic polymer and ionic salt electrolyte material. With the effect of electric field, cations and anions in ion-gel diffuse to form a double charge layer distribution with a charge layer on the surface of material. This capacitance characteristic is similar to that of traditional capacitor. In this paper, ion-gel (PVDF-[EMIM]TF2N) film is used as a dielectric layer material to prepare the bottom-gate graphene-based field effect transistor (GFET), which is compared with the GFET with SiO<sub>2</sub> bottom-gate, according to electrical characteristic curves. The effect of the ion-gel film on the transconductance, switching ratio and Dirac voltage of the GFET are analyzed. The effect of the vacuum environment and temperature on the GFET performance with ion-gel film gate are also investigated. The results show that in the room-temperature environment, the switching ratio and transconductance of the ion-gel film gate GFET device increase to 6.95 and 3.68 × 10<sup>–2</sup> mS, respectively, compared with those of the SiO<sub>2</sub> gate GFET, while the Dirac voltage decreases to 1.3 V. The increase in transconductance and switching ratio of ion-gel film gate GFETs are mainly due to the high capacitance of ion-gel film compared with those of conventional SiO<sub>2</sub> gate dielectrics. There will be more carriers inside the graphene while in the carrier accumulation region of GFET transfer characteristic curve, which makes graphene more conductive. The Dirac voltage of ion-gel film gate GFET can be reduced to 0.4 V in the vacuum environment; as the temperature increases, the transconductance of GFET can increase up to 6.11×10<sup>–2</sup> mS. The results indicate that the ion-gel film-based graphene field effect transistor shows good electrical properties in serving as high dielectric constant organic dielectric materials.

Compressive Strength of Cement Mortar with white cement and limestone

In this paper, the properties of cement mortar were studied after replacing part of the cement with other materials namely white cement, and limestone powder. The experimental test results were compared with normal cement mortar. Three kinds of mixtures were used. In the first type, cement was replaced with white cement only with different rates (5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%), the best ratio was determined, namely, the percentage that gave the highest value in the compression strength test, which is the compensatory ratio of 25%. In the second type of mixtures, a fraction of the cement was replaced with limestone powder only and with different rates (10%, 20%, 30%, 40%, and 50%). In the third type, cement was replaced by 25% white cement and different limestone powder ratio. Super-plasticizer (SP) was used with 1.5% rate. The compressive strength, absorption, the dry and wet density of all mixtures was measured. The results showed that the use of white cement instead of cement led to the production of cement mortar different in colors and better specifications, especially when the compensation rate was 25%. The results also showed that limestone powder gave a remarkable improvement in the properties of white cement mortar. Â

Influences of Clay Brick Particles on the Performance of Cement Stabilized Recycled Aggregate as Pavement Base

This paper presents an investigation on the influences of clay brick particles on the performance of cement stabilized recycled aggregate as pavement base. The comparative tests of unconfined compressive strength, compressive modulus of resilience, frost resistance, scouring resistance, drying shrinkage and temperature shrinkage of 6 kinds of mixtures with different coarse and fine clay brick particle contents were carried out. Test results showed that the unconfined compressive strength of cement stabilized recycled aggregate was compromised by the clay brick particles, especially the lateral strength. The coarse clay brick particles had little influence on the compressive resilience modulus of the mixture, while the fine clay brick particles could significantly increase it. The frost resistance of the mixture increased first and then slightly decreased with the increase of the content of coarse clay brick particle, while it increased with the increase of fine particle content. The scoured mass loss increased with the increase of coarse clay brick particle content. However, it is discovered that the fine clay brick particles had almost no influences on the scoured mass loss. The addition of both coarse and fine clay brick particles could decrease the drying shrinkage of the mixture at early construction stage. The temperature shrinkage performance of the mixture was not so sensitive to the addition of clay brick particles. Generally, the cement stabilized recycled aggregate with clay brick particles could meet the requirements of the pavement base in many cases but it needs to be optimized in application with consideration of the load and climate conditions.

Mechanical and Reaction Properties of Al/TiH2/PTFE under Quasi‐Static Compression

TiH2 is introduced into Al/PTFE reaction system for the first time. In order to study the mechanical and reaction properties of Al/TiH2/PTFE composites, five kinds of mixtures with different TiH2 contents and the contrasting TiH2/PTFE mixture are prepared. The true stress–strain curves and reaction phenomena are recorded during the quasi‐static compression experiments; The reaction residues are analyzed with XRD to understand the reaction mechanism. The results show that the introduction of TiH2 can significantly influence the strength of the composites; With the increasing of TiH2 content, the mechanical strength is firstly increase and then decrease; When the content is the same, the reinforcing effect of TiH2 particles on PTFE matrix is greater than that of Al. Violent reaction are observed in the four Al/TiH2/PTFE composites with the content of TiH2 below 20%, but not in TiH2/PTFE. Furthermore, compared with Al/PTFE material, special flames are found during the reaction of composites with TiH2, which become even more obvious with the increasing of TiH2 content. The material reaction mechanism denotes that the high temperature of the crack tip result in the reaction of Al and PTFE, which activates TiH2 to release hydrogen and generate TiC, resulting TiH2 to fully release its energy.

A simulation study on selection of optimized process for azeotropic separation of methanol and benzene: Internal heat integration and economic analysis

This work provides an insight into the separation of azeotropic mixtures by using two different techniques: pressure swing distillation and extractive distillation. Both methods are used to separate an azeotropic mixture of methanol and benzene. This mixture exhibits a minimum boiling azeotrope at temperature 57.97 °C and pressure 1 bar with mole fractions of 0.61 and 0.39 for methanol and benzene, respectively. However, the azeotropic point in methanol and benzene mixture is pressure sensitive, which can be shifted by changing pressure with a process called pressure swing distillation. Extractive distillation with suitable solvent is another method to separate such kind of mixture. Both methods are rigorously simulated and optimized for minimum heat duties. Internal heat integration is applied too for increasing energy efficiency. New optimization techniques are carried out with process simulator Aspen HYSYS V8.4 and results reveal the best method for separation of methanol and benzene azeotropic mixture.

Analysis of viscoelastic response and creep deformation mechanism of asphalt mixture

Asphalt mixture is a typical viscoelastic material. Its mechanical response and deformation behavior depend on the role of time, temperature conditions and stress levels. Three kinds of asphalt mixture (i.e. AC-13, AC-16, AC-20) were used for the static creep test in different temperature conditions and stress levels. According to the creep curve, The Burgers viscoelastic parameters including E1, η1, E2, η2 and the steady-state creep rate K were obtained. The effects of test temperature, stress level and aggregate gradation on the viscoelastic parameters of asphalt mixture were analyzed. Based on the relationship between the steady-state creep rate and the experimental temperature & load stress, the stress index and creep activation energy of asphalt mixture were proposed. By analyzing the relationship between the creep activation energy and the rutting depth, the creep mechanism of the asphalt mixture was discussed. The results show that with the increase of temperature, the four parameters of E1, η1, E2 and η2 of the three kinds of asphalt mixtures generally decrease. But at different temperatures, the viscoelastic parameters of these three kinds of mixtures are not the same. The stress level has a significant effect on the viscoelastic properties of the asphalt mixture. The four viscoelastic parameters have the largest differences when the stress level is at the intermediate load level of 0.5 MPa, but the responses of the different gradation asphalt mixture to the stress level are different. With the increase of temperature and load stress, the steady-state creep rate increases gradually, but the stress indexes of these three kinds of asphalt mixtures stress index are not different. All of them are less than 3, and belong to the diffusion creep under the control of aggregate interface dislocation mechanism. The asphalt mixture that has larger creep activation energy has better stability under high temperature. AC-16 mixture has the highest creep activation energy. Nominal particle size is not a decisive factor for the performance in high temperature.

Shock tube measurements and kinetic modeling study on autoignition characteristics of cyclohexanone

Cyclohexanone was identified as an attractive second-generation biofuel that can be used as an alternative fuel or blending component, thereby reducing greenhouse gas and particulate emissions from internal combustion engines. This paper investigates auto-ignition characteristics of cyclohexanone/O2/Ar mixtures behind reflected shock waves. Ignition delay time measurements cover the temperature range of 1255−1646 K, with pressures near 2.5, 5, and 10 atm, argon/oxygen dilution ratios of 23.9, 48.9 and 98.9, and equivalence ratios of 0.5, 1.0, and 2.0. Five kinds of mixtures were prepared to determine the effects of pressure, equivalence ratio and dilution ratio on the reactivity over the entire temperature range. An ignition delay correlation, τ=6.87×10−6P−0.52Φ0.70D0.66exp(45.59/RT)(μs), has been developed for cyclohexanone, including dependencies on pressure, equivalence ratio and dilution ratio. Experimental data have been compared to the kinetic modeling predictions of Serinyel et al. [Proc. Combust. Inst. 35 (2015) 507−514]. In general, the predictions overestimate the experimental data by 30–50%. With several reaction rate constants of selected small radical reactions updated, the predictions by modified mechanism present satisfactory agreement with the measured ignition delay data. Also, simulations based on the original model and modified model were compared to species concentrations measured in a jet-stirred reactor at 10 atm from the literature. Reaction pathway and sensitivity analyses were performed to identify the fuel consumption paths and key reactions during the ignition process of cyclohexanone. To our knowledge, the auto-ignition measurement of gas-phase cyclohexanone presented here are the first measurement for this compound.

The Effect of Mixing Ratio and Fuel Purity on Smoke and Burning Characteristics of N-heptane/Toluene Test Fire

Abstract Experiments were conducted in a fire test room to investigate soot particle and burning behavior of n-heptane/toluene mixtures blended by liquids in different mixing ratio and different purity. Analytical reagent n-heptane (AR, purity ≥ 99.5 %), chemically pure n-heptane (CP, purity ≥ 97 %) and toluene (purity ≥ 99.5 %) were selected to prepare four kinds of mixtures, mixing by volume and by mass were two modes available. Extinction coefficient of smoke was obtained by extinction meter on the room ceiling. Size distribution of soot particles was measured by fast particulate spectrometer DMS500, then count median diameter (CMD) and geometric standard deviation of diameter (GSD) were calculated. Mass loss curve and temperature profile were measured by electronic balance and thermocouples, respectively. Experimental results revealed that even small difference in the incorporation of toluene, such as mixed by volume and mixed by mass, had significant influences on smoke extinction and CMD. When fuels were mixed in a same mass ratio, slight gap in purities could also affect smoke extinction. Thus fuels mixed by mass could not be employed as test fire, while CP n-heptane could be selected to prepare fuels of test fire based on our preliminary results. As for burning behavior, temperature profiles were almost identical for all mixtures, mass loss curves also had good consistencies.

Rapid spectroscopic measurement of methanol in water-ethanol-methanol mixtures

The paper is focused on the Raman spectroscopic analysis of methanol content in water-ethanol-methanol mixtures as this kind of mixture chemically closely relates to alcoholic drinks. Counterfeit alcoholic drinks represent losses to the economy, but especially can cause serious health risks starting from nausea, to blindness, and even death. Extensive methanol poisonings were reported in last decades in number of countries worldwide. A set of water-ethanol-methanol mixtures with a range of concentrations of methanol from 0 % to 100 % was prepared to obtain the calibration dataset, needful for quantitative assessment. Based on calibration data, test samples and alcoholic beverages were evaluated. Raman spectroscopy is used especially because of this method’s benefits as specific vibrational fingerprint, direct measurement through the bottles, no need of additional chemicals and fast response. The study confirms the rapid and accurate analysis complying with safety limits set by methanol spirits legislation.

Dielectric behavior of a sintered heterogeneous ternary composite resin/BT/Cu2O

In this paper, we investigate and model the dielectric behavior of a ternary composite prepared at room temperature with a mixture of epoxy resin (RE), barium titanate (BT) and copper oxide (Cu2 O), sintered at three different temperatures (150 °C, 200 °C, and 250 °C). Time domain spectroscopy (TDS) is used to characterize samples in the range [DC to 2 GHz] by performing a particular study at low frequency (500 MHz). The latter focused on both the sintering and the Cu2 O addition effects on a ternary composite dielectric behavior. These effects were quantified as a function of the BT volume fraction. For this purpose, we used an optimization method based on nonlinear regressions to determine the permittivity, to minimize systematic errors of this dielectric parameter, and to show the effect of Cu2 O on it. Moreover, we attempt to explain the sintering temperature effect on this kind of mixtures through the modified Lichtenecker model. As a matter of fact, the importance of this law is allocated on one hand to the validation and concordance of the experimental results with those of the theory and on the other hand to the temperature effect investigation on the form factor given by the modified Lichtenecker law.

Segregation patterns in binary granular mixtures with same layer-thickness under vertical vibration

Inspired by the theoretical prediction [Phys. Rev. Lett. 86, 3423 (2001)] and the disputed experimental results [Phys. Rev. Lett. 89, 189601(2002), Phys. Rev. Lett. 90, 014302 (2003)] about the problem of granular segregation, we systematically investigate the pattern of binary granular mixtures consisting of same layer-thickness under vertical vibration. Various kinds of mixtures with different diameters and densities particles are poured into the glass cylinder that is sealed and evacuated to an air pressure less than 50Pa to observe separation patterns. It is found that these granular mixtures behave like five kinds of segregation patterns for different driving control parameters, i.e., Brazil nut (BN), reversed Brazil nut (RBN), Mixed states, light-BN (LBN), and light-RBN (LRBN). The latter two regimes are neither purely segregated nor completely mixed states. Moreover, BN phenomenon takes place in the area of low density ratio and found to be independent of layer-thickness, while RBN is sensitive to both the layer-thickness and frequency and occurs at the large density ratio area. Our result may be helpful for the establishment of theory about the segregation and mixing of granular mixtures.

Effects of Diatomite and SBS on Freeze-Thaw Resistance of Crumb Rubber Modified Asphalt Mixture

Asphalt mixture is susceptible to moisture damage under the effect of freeze-thaw (F-T) cycles. In this paper, crumb rubber (CR) was used to modify stone mastic asphalt (SMA) and the effects of diatomite and styrene butadiene styrene (SBS) on antifreezing performances of crumb rubber modified SMA (CRSMA) were investigated. Regression analysis and modified grey model (MGM) were used to construct the prediction models for properties of modified mixtures. CRSMA, CR and diatomite modified SMA (CRDSMA), and CR and SBS modified SMA (CRSSMA) were prepared in laboratory, respectively. Process of F-T cycles was designed. Air void, indirect tensile strength (ITS), and indirect tensile stiffness modulus (ITSM) were measured to evaluate the antifreezing performances of CRSMA, CRDSMA, and CRSSMA. Results indicate that air voids increase with the increasing of F-T cycles. ITS and ITSM all decrease with the increasing of F-T cycles. The addition of diatomite and SBS can reduce the air void and improve the ITS and ITSM of CRSMA. CRSSMA presents the lowest air void, highest tensile strength, and largest stiffness modulus, which reveals that CRSSMA has the best F-T resistance among three different kinds of mixtures. Moreover, MGM (1, 2) models present more favorable accuracy in prediction of air void and ITS compared with regression ones.

Effect of combined polymers on the loss of efficiency caused by mechanical degradation in drag reducing flows through straight tubes

The mechanical molecular degradation in drag reducing flows is a huge problem in the effort to improve the efficiency of drag reducers, which is clearly increased when a combination of materials is used. Here, we analyze mixtures of three kinds of water-soluble polymers: Poly (ethylene oxide) (PEO), Polyacrylamide (PAM), and Xanthan Gum (XG). Two kinds of mixtures are tested: (a) PAM and XG; (b) PEO and XG. The synergy between the polymers is clearly noticeable. The values of the drag reduction (DR) obtained by the polymer–polymer combination was larger than that observed for a single polymer in a solution with the same total concentration of the mixture. Our tests are conducted in straight tubes where the total pressure is fixed. The values of DR are computed step-by-step, as the total amount of solution pass through the system. In doing so, we carefully took into account the loss of efficiency caused by the turbulent flow in the straight tubes. It is quite clear that the degradation of the flexible polymers (PEO and PAM) is delayed in the mixtures. In other words, besides the increase in the DR, the flexible polymers are more resistant when in the presence of the rigid one (XG). Such observation is the main conclusion of this work.