Formation Of Zinc Sulfide Research Articles

Organo-Chlorinated Thin Films Deposited by Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition for Adhesion Enhancement between Rubber and Zinc-Plated Steel Monofilaments.

A continuous-flow plasma process working at atmospheric pressure is developed to enhance the adhesion between a rubber compound and a zinc-plated steel monofilament, with the long-term objective to find a potential alternative to the electrolytic brass plating process, which is currently used in tire industry. For this purpose, a highly efficient tubular dielectric barrier discharge reactor is built to allow the continuous treatment of "endless" cylindrical substrates. The best treatment conditions found regarding adhesion are Ar/O2 plasma pretreatment, followed by the deposition from dichloromethane of a 75 nm-thick organo-chlorinated plasma polymerized thin film. Ar/O2 pretreatment allows the removal of organic residues, coming from drawing lubricants, and induces external growth of zinc oxide. The plasma layer has to be preferably deposited at low power to conserve sufficient hydrocarbon moieties. Surface analyses reveal the complex chemical mechanism behind the establishment of strong adhesion levels, more than five times higher after the plasma treatment. During the vulcanization step, superficial ZnO reacts with the chlorinated species of the thin film and is converted into porous and granular bump-shaped ZnwOxHyClz nanostructures. Together, rubber additives diffuse through the plasma layer and lead to the formation of zinc sulfide on the substrate surface. Hence, two distinct interfaces, rubber/thin film and thin film/substrate, are established. On the basis of these observations, hypotheses explaining the high bonding strength results are formulated.

Theoretical studies of the decomposition of Zn[(iPr)2PSSe]2 single-source precursor in the gas phase for the chemical vapor deposition of binary and ternary zinc chalcogenides

Understanding the reaction mechanism by which single-source precursors decompose is important to the design of suitable experimental procedure involved in the chemical vapor deposition (CVD) process. The possible reaction mechanisms for the thermal decomposition of Zn[(iPr)2PSSe]2 precursor and its species in the gas phase has been studied by density functional theory calculation at the M06/LACVP∗ level. The results reveal that the reaction pathways that lead to the formation of zinc sulfide on the singlet potential energy surface are favored kinetically over those that lead to zinc selenide and ternary ZnSexS1−x formation. On the doublet PES, the reaction pathways that lead to zinc selenide formation are favored kinetically over those that lead to zinc sulfide and ternary ZnSexS1−x formation. However, in terms of equilibrium thermodynamic, the reaction pathways that lead to ternary ZnSexS1−x formation are more favorable than those that lead to zinc selenide and zinc sulfide formation on both the singlet and the doublet PESs. Density functional theory calculations reveal that the formation of ternary ZnSexS1−x are more favorable on thermodynamic grounds, than on kinetic.

Hydrogenation of bitumen in supercritical water flow and the effect of zinc addition

The composition of liquid and volatile products and residue of bitumen conversion in supercritical water (SCW) flow at 400°C and 30 MPa with and without addition of zinc savings to bitumen is investigated. The yield of liquid products upon bitumen SCW conversion reaches 47.3%. The data on oxygen and hydrogen balance in the initial bitumen, products, and conversion residue indicate the chemical participation of H2O molecules in the conversion. The yield of liquid products is increased up to 62.3% if zinc is added to the initial bitumen with a simultaneous increase of the H/C atomic ratio in the products. Hydrogenation is due to hydrogen evolution during zinc oxidation by supercritical water. Under these conditions, ZnO nanoparticles with a size of 50–100 nm are formed. The data of transmission electronic microscopy and X-ray diffraction analysis of oxidized zinc demonstrate the presence of about 0.5 wt % of ZnS and about 1.2 wt % of metal zinc clusters (up to 10-nm size) in the samples. According to the sulfur atoms’ balance accounting products and conversion residue, 12.6 wt % of bitumen sulfur participates in the formation of zinc sulfide.

Influence of Alloying Elements on Sulfide Formation in Lead Free Bronze Castings with Dispersed Sulfide Particles

The influence of the zinc sulfide ratio in the sulfide particle in the lead free bronze castings on the machinability is studied. Also, the influence of alloying elements of the zinc sulfide ratio of the sulfide particle is studied for understanding the mechanism of the zinc sulfide formation during the solidification. The zinc sulfide ratio is evaluated with the analysis of the microstructure in the lead free bronze prepared by the sand mold casting. The condition in which the zinc sulfide stably exists during the solidification is estimated with thermodynamic calculation. The machinability is improved with the decrement of the zinc sulfide ratio. The sulfide is formed as the copper sulfide and the zinc sulfide through eutectic reaction, and also appears as the liquid phase through monotectic reaction. The zinc sulfide is formed with the copper sulfide at the temperature, at which the zinc sulfide was predicted to be unstable by the thermodynamic calculation. The ratio of the zinc sulfide increases with increasing zinc content. Tin does not affect the zinc sulfide ratio when the tin content is less than about 4mass%. There is no effect of nickel on the zinc sulfide ratio. [doi:10.2320/matertrans.F-M2011835]

Mechanistic Studies on the Nucleation of Zinc Sulphide Nanoparticles by Means of XAFS Spectroscopy

Mechanistic studies on the nucleation of zinc sulphide nanoparticles from thioacetic acid were performed by means of X-ray absorption fine structure spectroscopy. Solutions of thioacetic acid and zinc salt (acetate or oxide) dissolved in a solvent (acetic acid or acetone) were investigated and compared with the corresponding zinc precursor and crystalline zinc sulphide to study the evolution of the structural environment around the zinc atoms in the solution. The investigations reveal that the coordination of sulphur atoms take place immediately when the mixture is prepared and zinc-sulphur species gradually evolve during the course of the reaction. However, the complete formation of zinc sulphide could not be evidenced even after a considerable period of time. This is likely due to the presence of unreacted zinc-oxygen species. The obtained results indicate that, once dissolved, zinc oxide reacts comparatively faster with thioacetic acid than with zinc acetate and that the choice of the reaction medium plays a crucial role in determining the kinetics and mechanism of zinc sulphide nucleation.

Formation of zinc sulfide and hydroxylapatite nanoparticles in polyelectrolyte-modified microemulsions

The paper is focused on the formation of nanoparticles, i.e., zinc sulfide (ZnS) and hydroxylapatite, in a microemulsion template phase consisting of heptanol, water, and a surfactant with a sulfobetaine head group in the absence and presence of an added polyelectrolyte. In the absence of a polyelectrolyte, beside larger particles, spherical ZnS nanoparticles with a diameter below 10 nm can be redispersed after solvent evaporation. In the presence of the synthetic cationic polyelectrolyte poly(diallyldimethylammonium chloride), a reloading of the particle surface is observed, and cationic charged ZnS nanoparticles, of about 5 nm in size, can be redispersed as a main fraction. When hydroxylapatite is formed in the presence of the more stiff biopolymer chitosan hydroxylapatite, hybrid structures were formed. Transmission electron micrographs show fiber-like aggregate structures, consisting of individual small nanoparticles ordered along the polymer chain.

Using density functional theory to postulate a mechanism for zinc sulfide formation in a CVD reactor

Zinc sulfide has a large band gap and is widely used in optical devices, laser domes, and reflective windows. Chemical vapor deposition (CVD) is the method of choice for producing zinc sulfide from zinc vapor and hydrogen sulfide on a large scale. Here, high quality, crystallinity, and low cost are desired. As such the ability to control the CVD reaction is very important and requires the CVD reaction mechanism which is not well known. This has motivated the study of the reaction mechanism in this paper. Specifically, the reaction between zinc vapor and hydrogen sulfide in a CVD reactor has been studied using ab initio and density functional calculations. Geometry optimizations were performed using the Becke three parameter and the Lee Yang Parr functional (B3LYP)/6-31G(d) and B3LYP/6-311+G(d, p) for reactants, transition structures, intermediate complexes, and products. Enthalpy and free energy of the reaction were estimated using B3LYP/6-31G(d), B3LYP/6-311+G(d, p), Gaussian G1, Gaussian G2, and G2MP2. The rate constant in the gas phase reaction was calculated using the transition state theory (TST) and was subsequently used in a computational fluid dynamics (CFD) model including momentum, mass, and energy balance. In this paper, two different pathways have been proposed for this reaction, namely a pathway that involves one transition state, and a second pathway involving two intermediate complexes and two transition states. The calculated rate constants using the proposed pathways were employed in a simulation of the deposition process. The calculated deposition rate is in excellent agreement with experimental data for the same reactor configuration. This suggests that molecular modeling is a powerful surrogate for experiments.

めっき廃液中の銅，亜鉛およびニッケルの硫化反応による選択的分離回収

Selective recovery of copper, zinc and nickel from electroplating wastewater was studied by precipitating the metal sulfides formed by sulfuration treatment. CuSO4, ZnSO4 and NiSO4 involved in model solutions and those of plating wastewater were adjusted to 100-120mg dm−3 of the initial metal concentration. Two kinds of sulfurating agents, sodium sulfide (Na2S) and sodium hydrosulfide (NaHS) of 6.8×10−2 mol dm−3, were employed.As a result, it was found that Na2S was more effective for the separation of the metal sulfides precipitated. The formation of metal sulfides was dependent on the pH value of the solution. In the sulfuration process using Na2S, copper was first separated from the solution as copper sulfide in pH1.4-1.5, followed by the formation of zinc sulfide in pH2.4-2.5. Subsequently, nickel sulfide was precipitated after the formation of copper and zinc sulfides in the residual solution in pH5.5-6.0.The same results of the formation behavior of copper sulfide, zinc sulfide and nickel sulfide in a simulated plating solution were obtained for those in an electroplating solution.

Modelling of transport phenomena in a low-pressure CVD reactor

The present work reports the analysis of transport phenomena in a low-pressure chemical vapour deposition (CVD) reactor. A two-dimensional unsteady model has been used to compute flow, chemical reactions and mass transfer rates within the reactor. The formation of zinc sulphide from the reaction of zinc vapour and gaseous hydrogen sulphide has been analysed. Two geometric designs of the reactor have been studied for assessing the overall deposition characteristics. The mathematical model comprises of the conservation equations of mass, momentum and the mass fractions of the reactant and product species. The governing partial differential equations have been solved by the finite volume method. The deposition surface has been taken to be chemically passive. There is an uncertainty in the boundary condition for the depositing species on the passive surface. The difficulty has been resolved by utilizing a homogenous Dirichlet condition at the surface. The present approach yields an upper bound on the deposition rate. The numerical results obtained show that the species concentration field, correlates closely to the flow field in the reactor. Over the range of Reynolds numbers studied namely 10–200, a recirculation pattern adjacent to the side walls is revealed and a stagnation zone forms ahead of the block. Reactant species mix predominantly in the zone close to the inflow plane and the product species are transported by advection. The reactor with a convex substrate streamlines the flow better as compared to the concave. As a result, higher concentrations of the product species reach the substrate. At a Reynolds number of 100, the deposition rate for the convex substrate was seen to increase by a factor of two with respect to the concave.

Modelling of transport phenomena in a low-pressure CVD reactor

The present work reports the analysis of transport phenomena in a low-pressure chemical vapour deposition (CVD) reactor. A two-dimensional unsteady model has been used to compute flow, chemical reactions and mass transfer rates within the reactor. The formation of zinc sulphide from the reaction of zinc vapour and gaseous hydrogen sulphide has been analysed. Two geometric designs of the reactor have been studied for assessing the overall deposition characteristics. The mathematical model comprises of the conservation equations of mass, momentum and the mass fractions of the reactant and product species. The governing partial differential equations have been solved by the finite volume method. The deposition surface has been taken to be chemically passive. There is an uncertainty in the boundary condition for the depositing species on the passive surface. The difficulty has been resolved by utilizing a homogenous Dirichlet condition at the surface. The present approach yields an upper bound on the deposition rate. The numerical results obtained show that the species concentration field, correlates closely to the flow field in the reactor. Over the range of Reynolds numbers studied namely 10–200, a recirculation pattern adjacent to the side walls is revealed and a stagnation zone forms ahead of the block. Reactant species mix predominantly in the zone close to the inflow plane and the product species are transported by advection. The reactor with a convex substrate streamlines the flow better as compared to the concave. As a result, higher concentrations of the product species reach the substrate. At a Reynolds number of 100, the deposition rate for the convex substrate was seen to increase by a factor of two with respect to the concave.

γ-Irradiation preparation and characterization of nanocrystalline ZnS

The γ-irradiation method was used successfully to prepare nanocrystalline ZnS in sphalerite structure at room temperature. Sodium thiosulfate, thiourea and mercaptoethanol were used as sulfur sources. The products obtained from irradiated solutions containing zinc ions and different sulfur sources are all sphalerite phase. The TEM images indicate that the product from mercaptoethanol is in best dispersion, and that from sodium thiosulfate aggregates most heavily. The possible mechanisms of the formation of zinc sulfide in different systems are proposed.

Evidence for aqueous clusters as intermediates during zinc sulfide formation

Using zinc sulfide as an example, we demonstrate a plausible stepwise process for the formation of minerals from low temperature aqueous solutions. The process occurs with the formation of soluble complexes that aggregate into soluble rings and clusters. The final moiety in solution has a structure similar to the moiety in the first formed solid, which is a restatement of the Ostwald step rule. Titrations of aqueous Zn(II) with bisulfide indicate that sulfide clusters form at concentrations of 20 μM (or less) of metal and bisulfide. Precipitation does not occur according to voltammetric measurements using a mercury electrode and UV-VIS (ultra-violet to visible) spectroscopic data. UV-VIS data and filtration experiments indicate that the material passes through 0.1 μm Nuclepore and 1000 dalton filters. The complexes form rapidly (kf > 108 Ms−1), are kinetically inert to dissociation and thermodynamically strong. Although a neutral complex of 1:1 (ZnS) empirical stoichiometry initially forms, an anionic complex with an empirical 2 Zn:3 S stoichiometry results with continued addition of sulfide. Gel electrophoresis confirms the existence of a cluster that is negatively charged with a molecular mass between 350 and 750 daltons. On the basis of known mineral and thiol complex structures for these systems, a tetrameric cluster unit of Zn4S6(H2O)44− is likely. Molecular mechanic calculations show that this cluster is structurally analogous to ZnS minerals (particularly sphalerite) and is a viable precursor to mineral formation and a product of mineral dissolution.The formation of Zn4S6(H2O)44− can occur from condensation of Zn3S3(H2O)6 rings, which are neutral molecular clusters. The Zn atoms on one Zn3S3(H2O)6 ring combine with the S atoms on another Zn3S3(H2O)6, to lead to higher order clusters with loss of water. The Zn4S64− species form by the cross-linking of two neutral Zn3S3 rings by added sulfide; thus a Zn–S–Zn bridge forms across the rings with subsequent rearrangement and condensation to Zn4S64−; this combination results in a sphalerite-like cluster. If the rings condense without additional sulfide, a wurtzite-like structure could form. All condensations result in sulfide displacement of water from Zn to form Zn–S bonds. Water loss is an example of an entropy-driven process, which leads to a more favorable thermodynamic process. These clusters would be resistant to oxidation by O2. Voltammetric experiments indicate neutral and anionic clusters for Zn and agree with ion chromatographic data from the sulfidic waters of the Black Sea.

The adhesion properties of stearic acid-loaded rubber compounds to brass-plated steel cords

The effect of stearic acid loading in rubber on the adhesion between rubber compounds and brass-plated steel cords was examined in respect to aging treatments and cure conditions. The adhesion interphase of a thin brass film/rubber compound containing stearic acid was investigated using an Auger electron spectrometer. The loading of stearic acid to rubber was not effective in the improvement of adhesion of rubber stock cured under optimum conditions, whereas it improved the adhesion property of premature cured samples by enhancing the physical property. High loading of stearic acid severely deteriorated the adhesion property, even at an unaged state due to the excessive formation of zinc sulfide. The loading of stearic acid did not affect the sensitivity of the rubber compound to humidity and thermal aging, but amplified the deterioration of adhesion when the rubber compound was subjected to salt solution aging, resulting in extremely poor adhesion. The effects of other ingredients and the aging treatment were also thoroughly examined.

Kinetics of Accelerated Vulcanization—III N-Cyclohexyl-Benzothiazole-2-Sulfenamide Accelerated Sulfur Vulcanization of Rubbers

Abstract Sulfenamide type of accelerators are well known for their outstanding processing safety combined with ultra-strong accelerating activity resulting in superior quality vulcanizates. Sulfenamides derived from different amines afford varying degrees of scorch delay and accelerating activity. Since there is no unanimity on the chemistry involved in this type of accelerated vulcanization, a preliminary study has been carried out to gain some insight into the mechanistic scheme. The present paper contains reports on the effects of varying concentrations of N-cyclohexyl-benzothiazole-2-sulfenamide (CBS) on the rate of free sulfur decrease and cross-link formation as well as zinc sulfide formation—whenever it occurs—both in the absence and presence of zinc oxide and of zinc oxide and stearic acid. The influence of temperature has also been investigated.

Kinetics of accelerated vulcanization. Sulfur vulcanization accelerated with 2‐mercaptobenzothiazole and its zinc salt in presence of zinc oxide and zinc oxide and stearic acid

AbstractSulfur vulcanization of natural rubber (NR) and styrene‐butadiene rubber (SBR) accelerated with 2‐mercaptobenzothiazole and zinc oxide with or without stearic acid has been studied and the results compared with those obtained by replacing the thiazole with its zinc salt. The order of the rate of vulcanization as measured from free sulfur decrease or crosslink formation is observed to be unity with respect to time and less than one with respect to accelerator concentration. In absence of stearic acid, the zinc salt is much less efficient than the thiazole in promoting vulcanization, and the efficiency of the latter shows a noticeable improvement over what is attained in absence of zinc oxide. Addition of stearic acid not only raises the efficiency of both the systems to the same level but also leads to a faster rate of vulcanization, a much higher degree of crosslinking, avoidance of reversion, and production of vulcanizates with considerably improved mechanical properties. The formation of zinc sulfide also reveals interesting variation. Attempts have been made to interprete these results in terms of complex formation between zinc salt of thiazole and zinc stearate.

The heats of formation and dissociation of zinc sulphide

AbstractAn entrainment method has been used to measure the reduction and dissociation equilibria of β‐zinc sulphide (sphalerite) in hydrogen and nitrogen respectively.Values obtained for ΔH1000 in the reactions studied ZnS(β)+Hg(g)=Zn(s)+H2S(g), and ZnS(β)=Zn(g)+½S2(g), were 71.93 ± 1.0 and 93.51 ± 1.0 kcal/mole, respectively.The heat of formation of zinc sulphide was calculated from the reaction Zn(s) + S(rhombic) = ZnS(β), and a value of ΔH298=‐49.2 ± 1.0 kcal./mole was obtained.It is concluded that the observed vapour pressure of ZnS is due completely to dissociation of it into Zn and S vapour.

The Action of Vulcanization Activators

Abstract 1. Zinc oxide and stearic acid do not affect the rate of addition of sulfur to rubber in the vulcanization of pure sodium butadiene rubber in mixtures without accelerators. 2. In mixtures containing diphenylguanidine as accelerator zinc oxide and stearic acid do not affect the rate of addition of sulfur to rubber. 3. In mixtures containing mercaptobenzothiazole zinc oxide retards and stearic acid accelerates the addition of sulfur to rubber. 4. In a similar manner zinc oxide suppresses and stearic acid activates isotope exchange between elementary sulfur and sulfur of the thiol group in mercaptobenzothiazole. 5. Zinc oxide and stearic acid in mixtures with mercaptobenzothiazole increase the rate and degree of crosslinking of the molecular chains of rubber; zinc oxide has the greater influence on the degree, while stearic acid has the greater influence on the rate, of the crosslinking reaction. 6. In mixtures with diphenylguanidine the influence of vulcanization activators on the degree and rate of crosslinking is considerably less pronounced than in mixtures with mercaptobenzothiazole. 7. The kinetics of zinc sulfide formation during vulcanization has been studied and it was established that ZnS is formed as the result of reactions of zinc oxide and zinc compounds with thiol and polysulfide groups in the rubber. Model substances have been used to demonstrate other possible routes for the formation of zinc sulfide during vulcanization. The effect of zinc oxide and stearic acid on the rate and degree of crosslinking is associated with participation of these compounds in such reactions. 8. Isotope exchange between radioactive sulfur in the vulcanizate and elementary sulfur was used to follow the formation and changes in the numbers of polysulfide linkages during the vulcanization process. The amount of sulfur participating in isotope exchange as vulcanization proceeds at first increases, passes through a maximum, and then decreases, which indicates a regrouping of the polysulfide linkages with an increase in their number and a decrease of the average number of sulfur atoms per linkage. Zinc oxide decreases the degree of isotope exchange between the vulcanizate and elementary sulfur at all stages of vulcanization. 9. Vulcanization activators, by favoring a decrease in the number of sulfur atoms in the sulfur bonds, increase the heat stability of the vulcanizates. This effect of the activators was demonstrated by kinetic data on stress relaxation in deformed vulcanizates at 126°. 10. The cleavage and regrouping of polysulfide linkages in the presence of zinc oxide and zinc compounds is accompanied by the combination of part of the sulfur as zinc sulfide, which leads to a decrease in the number of newly formed crosslinks. This effect of zinc oxide is manifested in vulcanization reversion effects and in changes of vulcanizate properties under thermomechanical influences. 11. From the above experimental data the general conclusion may be drawn that the fundamental role of vulcanization activators does not lie in their influence on the kinetics of the addition of sulfur to rubber, but rather in their influence on the nature of the vulcanization structures formed and on changes in them in the course of vulcanization.

Contributions to the Mechanism of Devulcanization II

Abstract Certain aspects of the reclamation of natural, butyl, and GR-S rubbers have been considered. While there are specific characteristic changes in all cases, e.g., zinc sulfide formation, etc., at the same time, important differences are recorded. The relation between some physical characteristics of cured reclaims and their parent vulcanizates have been discussed. The wide differences in the quality of reclaims, dependent upon the nature of the vulcanizing system employed in the parent vulcanizate, are interpreted as being substantially in agreement with previously published work, which has demonstrated the importance of curing mechanism upon reclaiming susceptibility.

Mixed Crystal Formation of Zinc Sulfide Postprecipitated with Mercuric Sulfide. The Aging of Mercuric Sulfide and of Zinc Sulfide.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMixed Crystal Formation of Zinc Sulfide Postprecipitated with Mercuric Sulfide. The Aging of Mercuric Sulfide and of Zinc Sulfide.R. MoltzauR. MoltzauMore by R. Moltzau and I. M. KolthoffI. M. KolthoffMore by I. M. KolthoffCite this: J. Phys. Chem. 1936, 40, 5, 637–643Publication Date (Print):May 1, 1936Publication History Published online1 May 2002Published inissue 1 May 1936https://doi.org/10.1021/j150374a009RIGHTS & PERMISSIONSArticle Views49Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (424 KB) Get e-Alerts