Aqueous Ammonium Chloride Solution Research Articles

塩化アンモニウム水溶液からのモリブデンの晶析に関する研究

塩化アンモニウム水溶液からのモリブデンの晶析に関する研究

Mushy-layer dynamics in micro and hyper gravity

We describe the results of experiments on mushy layers grown from aqueous ammonium chloride solution in normal, micro, and hyper gravity environments. In the fully developed chimney state, the chimney plume dynamics differ strikingly when conditions change from micro to hyper gravity. In microgravity, we find fully arrested plume motion and suppressed convection. As gravity exceeds Earth conditions, we observe a host of phenomena, ranging from arched plumes that undergo forced Rayleigh-Taylor instabilities to in-phase multiple plume oscillatory behavior. For the same initial solute concentrations and fixed boundary cooling temperatures, we find that, in runs of over two hours, the averaged effects of microgravity and hypergravity result in suppressed growth of the mushy layers, a phenomenon caused by a net enhancement of convective heat and solute transport from the liquid to the mushy layers. These behaviors are placed in the context of the theory of convecting mushy layers as studied under normal laboratory conditions.

Suppressing freckles during solidification due to periodic motion of top liquid layer

In the past, one main area of focus in the solidification of a liquid binary alloy has been the investigation of strategies for the elimination or minimization of the presence of “double-diffusive convection”, the main cause of poor quality alloys. In particular, “freckles” occurring in the solidification process cooled from the bottom can result in severe material defects in the final product. The objective of this study is to investigate the effect of a periodic lid-driven flow on the development of double-diffusive convection during solidification from below to aid in the removal or reduction of the occurrence of this convection that causes the formation of freckles. A hyper-eutectic aqueous ammonium chloride (NH4Cl–H2O) solution was used as the test sample and was contained in an enclosure cooled from the bottom to study flow development and heat and mass transport phenomena during solidification. Flow visualization using the shadowgraph technique and measurements of the temperature distribution, the concentration distribution, and the movement of the liquid–mush interface were conducted during solidification. The experimental results revealed that the imposed periodic lid-driven flow had a positive effect on the process by suppressing the plumes emanating from the channels and reducing the strength of the double-diffusive convection.

Dispersion polymerization of acrylamide with water‐soluble chitosan as the stabilizer

AbstractA cationic polyelectrolyte of P (CMTC‐AM‐DMC) was synthesized by dispersion polymerization in aqueous solution of ammonium chloride, with acrylamide and dimethylaminoethyl methacrylate methyl chloride as main raw materials. N‐carboxymethylthioureidochitosan was used as both the reactant and the stabilizer, and 2,2′‐azobis (2‐amidinopropane) dihydrochloride (V‐50) as the initiator. The effects of the major reaction variables such as the concentration of inorganic salt and initiator, temperature, reaction time, and pH on the polymerization were discussed in this article. The optimal conditions of the polymerization were determined by orthogonal tests. The results showed that an increase in salt concentration resulted in an increase of molecular weight and particle size and a decrease of apparent viscosity, while when salt concentration was up to 23.9%, apparent viscosity was slightly higher than others. Molecular weight, particle size, and apparent viscosity all decreased with the increase of initiator. The apparent viscosity, molecular weight, and particle size would decrease with pH, and the product would be coagulated when pH > 7. Temperature influenced the characteristic a lot. Overall conversion was less dependent on these factors except for the temperature. Molecular weight and overall conversion increased gradually with the time, and the monomers could react completely at about 5–7 h. Flocculation occurred with 13% of salt concentration, 0.005% of initiator, and pH > 7. The optimal reaction conditions for obtaining a stable aqueous dispersion were 22.3% for ammonium chloride, 0.007% for initiator, react under 55 °C for 5 h at pH = 4. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Fabrication of precise copper micro-coils using electrolytic etching

Precise and homogeneous copper micro-coils were fabricated using electrolytic etching in aqueous solution of sodium chloride and ammonium chloride. It was clarified that the etching rate was hardly influenced by the resist pattern thickness and the etching voltage, but only depended on the helical space pattern width. Start and stop of the etching was exactly controlled by switching on and off the power supply circuit, and the etching was practiced under the room temperature without heating the specimens. The sidewall surfaces of the etched coils were very much smoother than those of the coils fabricated by the conventional chemical etching, and very favorable coil width homogeneity was obtained even for narrow space patterns with a width around [email protected]

염화암모늄 수용액 응고시에 Mush 층에서 성분적 대류의 선형안정성

The onset of convection in a mushy layer is analyzed by using linear stability theory in time-dependent solidification of a binary melt. A simplified model of a near-eutectic mush, in which the mush is assumed to be a porous block, is used and the propagation theory is applied to determine the critical conditions for the onset of convection. The present critical Rayleigh number is higher than the existing experimental result and also theoretical results obtained by considering the mushy layer with an overlying liquid layer. The constant pressure (permeable) condition applied on the mush-liquid interface produces a lower critical Rayleigh number, which is closer to the experimental results of aqueous ammonium chloride solution, compared with the impermeable condition.

In-situ measurements of concentration and temperature during transient solidification of aqueous solution of ammonium chloride using laser interferometry

The variation in temperature and concentration plays a crucial role in predicting the final microstructure during solidification of a binary alloy. Most of the experimental techniques used to measure concentration and temperature are intrusive in nature and affect the flow field. In this paper, the main focus is laid on in-situ, non-intrusive, transient measurement of concentration and temperature during the solidification of a binary mixture of aqueous ammonium chloride solution (a metal-analog system) in a top cooled cavity using laser based Mach–Zehnder Interferometric technique. It was found from the interferogram, that the angular deviation of fringe pattern and the total number of fringes exhibit significant sensitivity to refractive index and hence are functions of the local temperature and concentration of the NH4Cl solution inside the cavity. Using the fringe characteristics, calibration curves were established for the range of temperature and concentration levels expected during the solidification process. In the actual solidification experiment, two hypoeutectic solutions (5% and 15% NH4Cl) were chosen. The calibration curves were used to determine the temperature and concentration of the solution inside the cavity during solidification of 5% and 15% NH4Cl solution at different instants of time. The measurement was carried out at a fixed point in the cavity, and the concentration variation with time was recorded as the solid–liquid interface approached the measurement point. The measurement exhibited distinct zones of concentration distribution caused by solute rejection and Rayleigh Benard convection. Further studies involving flow visualization with laser scattering confirmed the Rayleigh Benard convection. Computational modeling was also performed, which corroborated the experimental findings.

Modifiable chemically crosslinked poli(κ-carrageenan) particles

Abstract Micron size κ-carrageenan hydrogel particles, p(CRN) from linear κ-carrageenan, were prepared via microemulsion polymerization using divinyl sulfone (DVS) as chemical crosslinker in a sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse miceller system. Magnetic field responsive (m-p(CRN)) composite particles were also synthesized by encapsulating magnetic ferrite (Fe 3 O 4 ) nanoparticles together with linear κ-carrageenan within the AOT reverse micelle before the crosslinking reaction. The synthesized bare p(CRN) particles were further modified to produce positive charges on the particles (q-p(CRN)) by a quaternization reaction with an 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution. Scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential measurements and FT-IR analysis confirmed that particle sizes and charges were altered by chemical modification. Furthermore, a model drug, phenylephrine HCl was used for in vitro drug delivery studies to compare the effectiveness of modification of p(CRN) microgels by comparing bare p(CRN), m-p(CRN) and q-p(CRN) particles drug release capabilities in phosphate buffer solution (PBS) at pH 7.4.

ChemInform Abstract: Studies on Novel Synthetic Methodologies. Part 219. Allylation of N‐Benzoylhydrazones (= N′‐Alkylidene‐Substituted Benzohydrazides) by Treatment with Allyl Bromide in the Presence of Zinc in Aqueous Ammonium Chloride Solution.

ChemInform Abstract: Studies on Novel Synthetic Methodologies. Part 219. Allylation of N‐Benzoylhydrazones (= N′‐Alkylidene‐Substituted Benzohydrazides) by Treatment with Allyl Bromide in the Presence of Zinc in Aqueous Ammonium Chloride Solution.

Aggregation and adsorption of sodium dioctylsulfosuccinate in aqueous ammonium chloride solution: Role of mixed counterions

The critical micelle concentration (cmc) of sodium dioctylsulfosuccinate (AOT) was determined at 25°C from surface tension and fluorescence methods in aqueous NH4Cl solution for assessing the influence of mixed counterions on the special counterion binding behavior (SCB) of AOT. The SCB of AOT refers to a sudden twofold increase in the value of the counterion binding constant (β) in aqueous medium when the concentration (c*) of the added 1:1 sodium salt is about 0.015molkg−1, and it has been tested so far for sodium ion only. In the presence of sodium and ammonium mixed counterions also the SCB of AOT exist, but with lower c* (0.009molkg−1 NH4Cl). Synergism in the cmc occurs due to mixed counterions. In the case of inorganic counterions, unlike the case with organic counterions, the cmc is dependent on the total counterion concentration in solution and negligibly on the specific type of counterion. Na+ and NH4+ bind almost equally to the micelle in the region of low β (below c*), but in the region of high β (above c*) NH4+ binds predominantly. It has been shown that the theoretical expression for the surface excess of ionic surfactant+electrolyte system containing a single counterion can also be used to evaluate the surface excess in the presence of mixed counterions if the two counterions are considered to undergo Henry-type adsorption at the air–solution interface.

Modeling of solid phase sedimentation during directional solidification in a side cooled cavity

PurposeThe purpose of this paper is to present a new numerical approach for modeling the multi‐phase flow during an alloy solidification process. In many solidification processes, advection of solid may have a dramatic effect on bulk convection field as well as on the solid front growth and hence on the macro‐segregation pattern. In the present work, a numerical model is developed to simulate directional solidification in presence of melt convection as well as solid advection in the form of sedimentation. A 2D cavity filled with hyper‐eutectic aqueous ammonium chloride solution (25 wt.% of ammonium chloride) being chilled from one of the side walls has been chosen as the model problem for the numerical simulation.Design/methodology/approachA fixed grid volume averaging technique has been used for solving mass, momentum, energy, and species equation while taking into account the solid phase advection and local re‐melting. Two different criteria have been identified for the solid particles in the mushy zone to be mobile. These two criteria are represented by a critical solid fraction, and a critical velocity. Based on these two criteria, the mushy zone has been subdivided into two different regions namely, an immobile coherent zone consisting of packed equiaxed crystals and a mobile non‐coherent zone where the solid crystals are able to move.FindingsThe numerical results are compared with corresponding experimental observations.Originality/valueThe solid advection velocity and source terms dealing with solid velocity have been calculated using an explicit scheme, whereas the main conservation equations are solved using an implicit scheme.

Solidification of a Liquid Super-Eutectic Binary Alloy in an Enclosure with a Slanted Side Cooling Wall

This study considers the effect of a slanted side cooling wall that has varying inclination angles on the development of thermosolutal convection during the solidification of a super-eutectic aqueous ammonium chloride (NH4Cl-H2O) solution. The shadowgraph and particle image velocimetry techniques were employed to observe the flow development and measure the flow velocity during solidification. The transient temperature distribution within the test cell was also measured by type-T thermocouples. Experimental results reveal that a more slanted side cooling wall accelerated the “filling-box” process, thus it could cause more serious A-segregates and material defects in the solidified ingot.

Allylation of N‐Benzoylhydrazones (=N′‐Alkylidene‐Substituted Benzohydrazides) by Treatment with Allyl Bromide in the Presence of Zinc in Aqueous Ammonium Chloride Solution

AbstractN‐Benzoylhydrazones (=N′‐alkylidene‐substituted benzohydrazides) 1 are allylated efficiently by reaction with allyl bromide (2) in the presence of Zn in aqueous NH4Cl solution. The products 3 are formed in excellent yields (85–94%) within 35–50 min (Scheme, Table).

A SANS study for structural transition of micelles of cationic octadecyl trimethyl ammonium chloride and anionic ammonium dodecyl sulfate surfactants in aqueous solutions

The sizes and structures of micelles formed in aqueous solutions of cationic octadecyl trimethyl ammonium chloride (OTAC) and anionic ammonium dodecyl sulfate (ADS) surfactants were investigated using small angle neutron scattering (SANS). For aqueous OTAC solutions, SANS data indicate that the structure of micelles is of sphere with core and hydrated shell up to OTAC 50 mM. As the total OTAC concentration increases, SANS data show that the micelles become larger and the transition in micellar shape from sphere to oblate ellipsoid takes place. For aqueous ADS solutions, SANS data point to the micelle structure of sphere with core and shell but this time up to ADS 100 mM. Above this concentration the spherical micelles changes to oblate ellipsoid with core and hydrated shell. The surfactant concentration at which micelle shape changes is termed as the shape transition concentration which is 50 mM for OTAC and 100 mM for ADS. Such transitions may be explained qualitatively by the distortion of the hydrocarbon chains at high surfactant concentrations. When micelles are large, a number of hydrocarbon chains of the surfactant molecules should be accommodated in the core of the micelle and therefore the chains are likely to be distorted. That is why the micelle shape changes from sphere to ellipsoid and the ellipsoidal axial ratio ( R a/ R b or R a,core/ R b,core) must increase. This is reflected in the linear relationship between the ellipsoidal axial ratio and the aggregation number.

Determining micelle dimensions and shape in micellar surfactant solutions on the basis of the dispersion of the nuclear spin-lattice relaxation rate

The experimental and computed dispersion curves of the spin-lattice relaxation of systems containing asymmetric micelles are compared. The parameters of the structure of symmetric micelles are determined for aqueous solutions of sodium dodecylsulfate and decyl ammonium chloride on the basis of the obtained results.

Characterization and Optical Properties of CdS Thin Films Grown by Chemical Bath Deposition

CdS thin films were prepared on soda-lime glass (SLG) by the chemical bath deposition technique. An aqueous solution of cadmium salts, ammonium chloride, ammonium hydroxide and thiocarbamide were used in the deposition. The obtained CdS film samples were characterized by techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV−VIS−NIR spectrophotometer. The films are of hexagonal phase with preferred (0 0 2) orientation and the grain size increases with the thickness of the films. The films show good transmittance in the visible region. The band gap of the films is 2.41-2.45 eV and decreases with the increasing the thickness of the films.

Thermal characterization of HCN polymers by TG–MS, TG, DTA and DSC methods

This paper presents a thermogravimetry (TG) study of hydrogen cyanide polymers, synthesized from the reaction of equimolar aqueous solutions of sodium cyanide and ammonium chloride. Differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were also used to evaluate the thermal behaviour of these black polymers, which play an important role in prebiotic chemistry. A coupled TG–mass spectrometer (MS) system allowed us to analyze the principal volatile thermal decomposition and fragmentation products of the isolated HCN polymers under dynamic conditions and an inert atmosphere. After dehydration, a multi-step decomposition occurred in this particular polymeric system, due to the release of ammonia, hydrogen cyanide (depolymerization reaction), isocyanic acid (or cyanic acid) and formamide; these two latter species allow us identify bond connectivities. Finally, data collected from TG experiments in an oxidative atmosphere showed significant differences at higher temperatures, above 400 °C. According to these results, the different techniques of thermal analysis here applied have demonstrated to be an adequate methodology for the study and characterization of this complex macromolecular system, whose structure remains controversial even today.

The influence of hydrating agents on the hydration of industrial magnesium oxide

AbstractBACKGROUND: The influence of different hydrating agents on the pH of the hydrating solutions, rate of hydration of MgO to Mg(OH)2 and product surface area was studied as a function of temperature of hydration. Hydrating agents used were aqueous solutions of ammonium chloride, magnesium acetate, magnesium nitrate, nitric acid, acetic acid, magnesium chloride, sodium acetate and hydrochloric acid and distilled water as control. These were chosen to determine either the effect of addition of a common ion, the effect of changing the solution pH or due to the presence of an acetate ion, found earlier to have a beneficial effect on the hydration of MgO.RESULTS: There was no significant difference in the hydration behaviour of the hydrating agents up to 50 °C, where less than 10% of magnesium hydroxide was formed. The amount of hydroxide increased at temperatures above 60 °C. When compared with the hydration in water, all the hydrating agents, with the exception of sodium acetate, showed a significant increase in the degree of hydration. Sodium acetate formed the lowest amount of magnesium hydroxide, ranging between 1.2 and 12.2% magnesium hydroxide. The largest percentage (56.7%) of magnesium hydroxide was formed from hydration in magnesium acetate.CONCLUSION: It seems that MgO hydration is a dissolution‐precipitation process controlled by the dissolution of MgO. The increased degree of hydration in magnesium acetate is possibly due to the presence of acetate and Mg2+ ions. Copyright © 2010 Society of Chemical Industry

In situ LIF temperature measurements in aqueous ammonium chloride solution during uni-directional solidification

We present in situ whole-field measurements of the temperature field using laser-induced fluorescence in a study of bottom-chilled uni-directional solidification of aqueous ammonium chloride. We utilize a two-color, two-dye, ratiometric approach to address the significant spatial and temporal variations of laser sheet intensity field due to refractive index variations caused by the evolving concentration and temperature fields. In our work we take advantage of two temperature sensitive fluorescent dyes with opposite temperature sensitivities in order to increase the overall sensitivity and temperature resolution of the measurements. The resulting temperature sensitivity (about 4% K−1) is more than a factor of two higher than the original work of Sakakibara and Adrian (Exp Fluids 26:7–15, 1999) with a sensitivity 1.7% K−1. In situ measurements of the temperature field during solidification are presented, along with temperature characteristics of some of the complex flow features, such as plumes and fingers.

Solubility prediction of malachite in aqueous ammoniacal ammonium chloride solutions at 25 °C

The solubility of malachite in the presence of ammonia, ammonium chloride and their mixed solution is calculated by a geochemical modeling code and is measured in a series of dissolution experiments using synthetic malachite at 25 °C. The simulated results show a good agreement with the experimental data gained at 25 °C. The predicted and experimental results indicate that the precipitate CuO limits the copper solubility in aqueous ammonia and Cu(OH) 1.5Cl 0.5 in aqueous ammonium chloride. For a mixed solution containing ammonia and ammonium chloride, highest copper solubility can be achieved by adjusting the [NH 3]/[NH 4Cl] ratio to about 2:1. The thermodynamic model presented rationalises the interactions between the different components and predicts the influence of changes in the concentration of ammonia and ammonium chloride on the copper solubility of malachite.