Hydroxide Sol Research Articles

One‐Pot Synthesis of Gold Nanoparticles and Aluminum Hydroxide Hydrogels‐Based Nanocomposites with Modulated Optical Properties

AbstractIn this work, the one‐pot synthesis of composites constituted by gold nanoparticles (AuNPs) and aluminum hydroxide hydrogels (AlHG) by employing the Epoxide Route is presented. To modulate the optical properties of the final composites, different anions (X= , , and ) were used as nucleophile, complexing and growth directing agents of the AuNPs. In addition, the concentration of the reactants, e. g., the X : Cl ratio, was set in such a way to preserve the alkalization rate, the transparency of the hydrogels supporting the AuNPs, and the stability of the final composites. Consequently, the composites exhibit different plasmonic properties, resulting from the AuNPs with different sizes and morphologies, as confirmed through transmission electron microscopy, depending on the nature of the employed anion, exclusively. Furthermore, this versatile one‐pot synthesis strategy was employed to design new composites with different I : Cl ratio and synthesize stable colloidal AuNPs within an aluminum hydroxide sol (AuNP@Alsol) without adding any conventional capping agent. This AuNP@Alsol composite can be used as seed to accelerate the extremely slow AuNPs formation kinetics in AuNP@AlHG(SCN), demonstrating the potential of this synthesis method to create composites susceptible to be applied in the photonic and catalysis areas.

Erratum: Deposition of insoluble calcium phosphate layers by combining finely dispersed calcium hydroxide sols with soluble phosphates

The proceedings editor, while fixing formatting issues, inadvertently introduced inaccuracies within the chemical formulas and the authors names. A corrected version of the article has been published.

Deposition of insoluble calcium phosphate layers by combining finely dispersed calcium hydroxide sols with soluble phosphates

Carbonate containing materials are subject to severe weathering. Traditional formulations of stone strengtheners have low compatibility with the original material and further they contain VOCs (volatile organic compounds), which endanger human health and the environment. This study explores the high potential of novel treatments based on water-soluble phosphates used as an agent to react with calcium carbonate (CaCO3) to form an insoluble film of calcium phosphate in the pore space of the treated material. Pretreatments with nanolime suspensions ensure greater availability of calcium ions and reduce the consumption of the original material in the reactions. An alkaline environment is required to promote the conversion of the CaCO3 components to hydroxyapatite-like compounds. Based on experiments in aqueous solutions, different sources of phosphate ions could be examined and compared for the development of effective treatments to apply on different test specimens. To implement the treatments, barium phosphate solutions were investigated. Important aspects of this research are the use of green solvents and the search of components that avoid the formation of byproducts, to increase the efficiency of the chemical reactions and reduce possible negative effects on the operator, the environment and the very same built heritage material. The developed treatments are a valuable alternative to the traditional methods, as it follows an improvement in the material properties without affecting the moisture transport within it and allows the evenly reaction of the strengthened material to external physical and mechanical stresses without creating internal tension between the grains.

Lightweight, robust hierarchically porous ceramics from cost-effective powders for dye removal

A facile and cost-effective approach for hierarchically porous ceramics has been proposed firstly, using coal fly ash as the main powder while secondary aluminum dross (SAD) as curing and foaming agents. Benefited from the hydrolysis of AlN and Al in SAD, gas and lamellar aluminum hydroxide sol attached to the surface of unreacted particles were produced, meanwhile pH value and viscosity increased, realizing foaming and coagulation casting simultaneously to fabricate porous green body. The increase of SAD amount could contribute to more intensive formation of flaky aluminum hydroxide sol, enhancing mechanical strength of green body, which has high compressive strength of 1.03 MPa at a bulk density of 0.68 g/cm3. Porous mullite-based ceramics could be sintered at a relatively low temperature of 1200–1250 °C owing to alkali metal oxide and amorphous SiO2 in the solid wastes, which also help to form micropores on the pore wall due to partially sintering. Porous mullite-based ceramics possess hierarchical pores, bulk density of 1.00 g/cm3, open porosity of 66.15%, specific surface area of 2.24 m2/g and compressive strength of 9.14 MPa. Their removal rate of malachite green solution reaches 99.1% at a concentration of 100 mg/L and an adsorbent dosage of 100 g/L.

Hydrolysis‐induced simultaneous foaming and coagulation casting of secondary aluminum dross aqueous suspension

AbstractThe reactive AlN, heavy metal ions, and salts in secondary aluminum dross make them harmful to the environment and difficult to handle, and therefore categorized as hazardous solid waste. A novel, simple, and versatile technique has been proposed here to prepare hierarchically porous ceramics using secondary aluminum dross as the sole raw material, namely, the hydrolysis‐induced simultaneous foaming and coagulation casting method. As the main component, Al and AlN could be hydrolyzed to generate aluminum hydroxide sol, which can form three‐dimensional network and lead to the outstanding compressive strength of green body (7.03 MPa). Gas release during hydrolysis, high‐temperature oxidation of AlN, and metallic Al based on Kirkendall effect could account for the final multilevel pores. The utilization of harmful components in secondary aluminum dross, supplys an alternative colloidal forming way for porous green body with complex shape when combined with other ceramic powders or inorganic solid waste. Low sintering shrinkage of 1.38%–3.60% for hierarchically porous ceramics offers this highly effective and low‐cost method to be easily promoted for industrial production.

Investigation of microstructure, morphology and properties of monolayer and multilayer coating T6-HSS by the sol–gel route

ABSTRACT The coating’s purpose is to enhance the tribological conditions at the tool-workpiece and chip–tool interfaces. In comparison to commercial coatings, the current work offers a coating for high-speed steel (HSS) equipment that is thinner and less expensive. A single-point AISI T6 high-speed steel tool having a square cross-section was used to prepare the cutting inserts for turning purpose. The best conditions for coating the HSS insert with ceramic oxides using the sol–gel process were determined. These precursor conditions involved: viscosity, PH, dispersion materials, and the ageing period. The deposition conditions were the number of coating cycles, the immersion time, the calcination temperature, and dry temperature that affects the layer thickness, adhesion, surface roughness, and homogeneity for coating layer. Titanium tetra-isopropoxide (TTIP), a catalyst HCl, and a dispersion material (triethanolamine) were employed to prepare the precursor (titanium hydroxide). The PH, the viscosity, and the ageing time, of the produced precursor were 6.46 and 8.74 cP, and 6 h, respectively. After the dip coating of the cutting inserts for 5 sec immersion time and two number of coating cycle in titania precursor, the inserts were dried at 355℃ for 1 hour. Then, to form the alumina coating film, the inserts were dipped in the alumina hydroxide sol, which was made by combining aluminium isopropoxide IPA, deionised water H2O, and nitric acid (HNO3). The produced precursor had a PH of 5.83, viscosity of 8.11 cP, with an ageing time of 12 h. The immersion time and number of coating cycles in the alumina precursor were 25 sec, and two, respectively. The inserts were dried at 355℃ for 1 hour, then calcinated at 500°C for 2 h to achieve the appropriate film thickness for the machining test. The study investigates the thermal and tribological properties of coated with single and multiple layers as well as uncoated cutting inserts. The results indicated that the hardness is 1393.3 HV with a thickness of 6 µm for multilayer. X-ray diffraction-phase analysis confirms the presence of phases originating from the coatings and substrate. EDS analysis of the chemical composition of the studied coatings indicates the presence of titanium and aluminium, as well as oxygen. Atomic force microscopy (AFM) was used to examine the surface morphologies of coated surfaces. Scratch hardness is measured in GPa and differs between monolayers (alumina) and multilayers (titania/alumina). Monolayer alumina has a value of 0.374 GPa, whereas multilayer alumina/titania has a value of 1.010 GPa. Multilayer coated inserts, on the other hand, have a lower wear rate than monolayer coated and uncoated inserts. The thermal expansion coefficient of the titania layer is often relatively near to the thermal expansion coefficient of the bulk HSS (11 × 10−6, 13 × 10−6 1/K) that reduces mismatch between substrate HSS and top coating layer (alumina).

LiAlO<sub>2</sub> prepared by nitrates-free synthesis for carbon capture by MCFCs

The pure crystalline phase of alpha lithium aluminate, the state-of-the-art matrix support material, was directly prepared by two nitrates-free methods at 650 °C. A solgel method included pyrolysis of a colloidal mixture of aluminum hydroxide sol and lithium formate. The advantages of the used formate pyrolysis are the absence of nitrogen oxide emission in comparison to other combustion methods as well as it provides high homogeneity of a product. The solid-state reaction is a conventional method used in industry so the optimal powder-to-ball weight ratio was found in this study to give a high surface area. Described methods of synthesis are easy, economic and low-emission methods for the preparation of submicron α-LiAlO<sub>2</sub> powders with the surface area of about 25‒27 m 2 /g which is optimal for application as matrix material in мolten сarbonate fuel cells.

Synthesis and Photocatalytic Properties of Tantalum Nitride with an Inverse Opal Structure

Certain oxynitrides (LaTiO2N and TaON) and nitrides (Ta3N5) demonstrate potential as visible-light-driven photocatalysts1. These materials are typically synthesized from oxide precursors by thermal ammonolysis at temperatures up to 950 oC. Accordingly, these oxynitrides and nitrides intrinsically possess an abundance of anion vacancies or defects which act as electron-hole pair recombination centers, thereby limiting photocatalytic performance. In this work, we introduce photonic band gap engineering as a strategy for suppressing electron-hole pair recombination in tantalum nitride thin films, thereby achieving improved photocatalytic performance. Briefly, a series of inverse opal (IO) Ta3N5 thin films with different macropore sizes were fabricated by the colloidal crystal template approach. This kind of approach has been successfully made on TiO2 photocatalysts2. Three batches of monodisperse polymethylmethacrylate (PMMA) colloids of diameters ranging from 230 to 430 nm were first synthesized by the surfactant-free emulsion polymerization of methyl methacrylate. PMMA colloidal crystal thin films were then grown on silica glass slides using a flow-controlled vertical deposition technique. As the meniscus of the suspension moved down the glass slide by pumping up a peristaltic pump, colloidal crystal layer of several microns were deposited. Several drops of TaCl5 solution were placed softly on the edge of the colloidal crystal and immersed into the crystal by capillary phenomena. Subsequently, the interstitial voids in the colloidal crystal films (synthetic opals) were filled with a tantalum hydroxide sol. Ammonolysis of the resulting composite films under an ammonia stream of 200 ml/min at 700ºC yielded IO Ta3N5 thin films, shown in Fig.1. The IO Ta3N5 films possess a 3-dimensionally ordered macroporous structure with periodicity on the scale of visible-light wavelengths, resulting in pseudo photonic band gaps at visible wavelengths. By matching the red-edge of the PBG location with the absorption edge of Ta3N5, electron-hole pair recombination is suppressed and the photocatalytic activity dramatically improved. In this experiment, strong reflection due to [111] photonic bandgap was clearly observed at 543nm for the IO amorphous Ta2O5 film and at 581nm for the IO Ta3N5 film, respectively. Appearance of the IO Ta3N5 film was reddish orange in color but it gave a strong yellow reflection in a certain angle, seen in Fig. 2. Since the optical bandgap of Ta3N5 was estimated to be 2.1eV (=590nm), the IO tantalum nitrides with both optical and bandgaps properly matched could be fabricated. Photocatalystic H2 evolution activity of the IO Ta3N5 under UV or visible ray irradiation will be appeared at the presentation, togather with a comparison with that of Ta3N5 powder. References Tsuyoshi Takata, Chengsi Pan and Kazunari Domen; Sci. Technol. Adv. Mater., 16 (2015) 033506 (18pp).Waterhouse et al., Sci. Rep., 3 (2013) 2849 (5pp). Figure 1

Effects of Preparation Conditions on Electrophoresis and Other Properties of Iron Hydroxide Sol

Effects of Preparation Conditions on Electrophoresis and Other Properties of Iron Hydroxide Sol

Improving dispersion stability of zirconium hydroxide sol for preparing nano zirconia by the reverse precipitation

Zirconium hydroxide sol was prepared by the reverse precipitation method with ZrOCl2 solution as raw material and the processing condition of the zirconium hydroxide sol was investigated. When the saturated absorption amount of the surfactant was 1.0 wt%, the pH value for the highest stability was shifted from 7.9 to 9.3 and the pH range for preparing stable zirconium hydroxide sol widened as 8.0-11.0. The suitable concentration of ZrOCl2 solution for the efficient gelation keeping the high dispersion stability was investigated. The microwave drying was demonstrated to be suitable for preparation of nanoparticle. The characteristics of produced nano zirconia were discussed, which in results the shape of powder was spherical and the grain size was 35 nm at average with moderate dispersion.

Robust Rare‐Earth‐Containing Superhydrophobic Coatings for Strong Protection of Magnesium and Aluminum Alloys

AbstractThe robust rare‐earth‐containing superhydrophobic coatings are fabricated by a simple and scalable method, which includes spraying the lanthanum hydroxide sol onto metallic substrates (AZ61 Mg and 2024 Al) and then modifying the surfaces with stearic acid. The as‐prepared coatings on AZ61 Mg and 2024 Al have identical morphology and composition. Both are composed of fiber‐like La(OH)3 nanowires that cross‐link and form a network structure, which are pivotal for inducing surface superhydrophobicity with water contact angles (WCAs) as high as ≈157°. The superhydrophobic coatings demonstrate remarkable corrosion resistance as well as high chemical and mechanical stabilities. The theoretical simulation based on molecular mechanics suggests that the high stabilities mainly arise from the strong bonding between La2O3 and stearic acid molecules. The fabrication approach proposed here is hopeful to extend for large‐scale preparation of robust superhydrophobic metallic materials widely applied.

Synthesis of praseodymium-ion-doped perovskite nanophosphor in supercritical water

We report the synthesis of praseodymium-doped calcium strontium titanate nanoparticles, (Ca0.6Sr0.4)0.997Pr0.002TiO3 (PCSTO), using hydrothermal synthesis under supercritical water conditions and the production of red luminescence. Starting solutions were prepared by dissolving calcium nitrate, strontium nitrate, titanium hydroxide sols, and praseodymium nitrate in distilled water. We investigated the effect of the reaction temperature, concentration, and pH of the starting solution on the luminescence properties. Synthesis was conducted at temperatures of 200 °C–400 °C, a reaction pressure of 30 MPa, and for reaction times of 4–20 s. The Pr concentration was set to 0.2 mol% relative to the (Ca0.6Sr0.4) ions. We also investigated the effect of high temperature annealing on the luminescence properties of the PCSTO nanoparticles. Particle characteristics were evaluated using x-ray diffraction, a scanning transmission electron microscope (STEM) equipped with an energy-dispersive x-ray spectrometer, and a fluorometer. Single-phase perovskite particles were obtained at hydrothermal reaction temperatures of over 300 °C even for a reaction time of several seconds. STEM images showed that the particles had cubic-like shapes with diameters of 8–13 nm and that they were chemically homogeneous. The PCSTO nanoparticles exhibited sharp red luminescence at 612 nm corresponding to the f–f transition of Pr3+ ions. Moreover, annealing at 1000 °C led to particle growth, achieving diameters of 40 nm and an increase in the quantum efficiency to around 12.0%.

Superhydrophobicity, Self-cleaning and Flame Retardancy Properties of Cotton Fabric

A simple and facile method for fabricating the cotton fabric with superhydrophobicity, self-cleaning and flame retardancy was described in the present work. Three types of antimony pentoxide sol (Sb2O5), aluminum hydroxide sol (Al(OH)3) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (fluoroalkyl silanes) were used as coating for the cotton fabric. It was found that Sb2O5 and Al(OH)3 exhibited significant synergistic effects on the flame retardancy. When the weight ratio of Sb2O5/Al(OH)3(content 30 wt%) was 1:3, the results showed that the limiting oxygen index (LOI) value was 45.1 %, smoke density (SDR) value was 35 %, and it still passed UL94 V-0 rating. The cotton fabrics coated with fluoroalkyl silanes/Sb2O5/ Al(OH)3 showed a superhydrophobicity, anti-contamination and self-cleaning properties. In addition, the results exhibited the outstanding superhydrophobicity, oil/water separation, excellent waterproofing durability and flame retardancy of cotton fabric after 1000 cycles of washing by water, the LOI value was 40.1 %, SDR value was 39 % and WCA was 152° after 1000 cycles of washing. We believe that this simple, environmentally friendly and versatile fabrication of the cotton fabric had excellent real-life applications.

Ultrathin Oxide Layer-Wrapped Noble Metal Nanoparticles via Colloidal Electrostatic Self-Assembly for Efficient and Reusable Surface Enhanced Raman Scattering Substrates.

Controllable and flexible fabrication of ultrathin and uniform oxide layer-wrapped noble metal nanoparticles (NPs) has been expected. Here a new strategy is presented for them based on colloidal electrostatic attraction and self-assembly on the metal NPs via one-step laser ablation of noble metal targets in the hydrolysis-induced hydroxide sol solutions at room temperature. The Au NPs, with several tens of nanometers in size, are taken as core part and TiO2 as shell-layer to demonstrate the validity of the presented strategy. It has been shown that the TiO2 shell-wrapped Au NPs are obtained after laser ablation of Au target in the hydrolysis-induced Ti(OH)4 sol solution. The Au NPs are about 35 nm in mean size, and the TiO2 shell layers are amorphous in structure and about 2.5 nm in thickness. The shell thickness is nearly independent of the Au NPs' size. Further experiments have shown that the thickness and crystallinity of the shell-layer can be tuned and controlled via changing the temperature or pH value of the Ti(OH)4 sol solution or prolonging the laser ablation duration. The formation of the TiO2 shell-wrapped Au NPs is attributed to attachment and self-assembly of Ti(OH)4 colloids on the laser-induced Au NPs due to the electrostatic attraction between them. Importantly, the presented strategy is universal and suitable for fabrication of many other ultrathin oxide-wrapped noble metal NPs. A series of oxide shell-wrapped noble metal NPs have been successfully fabricated, such as Au@oxides (Fe2O3, Al2O3, CuO, and ZnO) as well as Pt@TiO2 and Pd@TiO2, etc. Further, compared with the pure gold NPs-built film, the TiO2-wrapped Au NPs-built film has exhibited much stronger surface enhanced Raman scattering (SERS) performance to the anions NO3-, which weakly interact with noble metals, and the good reusability for the SERS-based detection of 4-nitrophenol, which could be photodegraded by xenon lamp irradiation. This work provides a flexible and universal route to the ultrathin and uniform oxide layer-wrapped noble metal NPs.

Effect of Ferrous Additives on Magnesia Stone Hydration

The article deals with the modification of the magnesia binder with additives containing two- and three-valent iron cations which could be embedded in the chloromagnesium stone structure and also increase the strength from 60 MPa in a non-additive stone to 80MPa, water resistance from 0.58 for clear stone to 0.8 and reduce the hygroscopicity from 8% in the non-additive stone to 2% in the modified chloromagnesium stone. It is proposed to use the iron hydroxide sol as an additive in the quantities of up to 1% of the weight of the binder. The studies were carried out using the modern analysis methods: the differentialthermal and X-ray phase analysis. The structure was studied with an electron microscope with an X-ray microanalyzer. A two-factor plan-experiment was designed which allowed constructing mathematical models characterizing the influence of variable factors, such as the density of the zatcher and the amount of sol in the binder, on the basic properties of the magnesian stone. The result of the research was the magnesia stone with the claimed properties and formed from minerals characteristic for magnesian materials as well as additionally formed from amachenite and goethite. It has been established that a highly active iron hydroxide sol the ion sizes of which are commensurate with magnesium ions is actively incorporated into the structure of pentahydroxychloride and magnesium hydroxide changing the habit of crystals compacting the structure of the stone and changing its hygroscopicity.

Improving the Properties and Structure of Magnesium Materials of Sol of Iron Hydroxide

Currently, magnesia materials are widespread in construction. However, the main problems of their mass use have remained unsolved due to a large number of factors, which result in the rise in their already high prime cost due to introduction of such process operations as crushing and milling of the introduced additives to increase their specific surface and hydraulic activity. Therefore, it is rather promising to search for such additives, which would contain active cations of metals and at the same time build in the structure of magnesium silicate hydrates and form insoluble minerals of the magnesia rock. The search for the additives led us to different sols, introduction of which is restricted to 1% of the weight of the binder, and which are able in such a small amount to increase the basic properties of the cement rock. The approbation of such additives and the evaluation of their influence on the properties, phase composition and structure of the magnesia binder are rather important. The article contains the results of evaluating the influence of the added iron hydroxide sol on hardening and curing of the magnesia paste, formation of the structure and properties of the magnesia rock. At carrying these researches out it has been determined that the iron hydroxide sol introduced into the composition of the magnesia-chloride binder in the amount of up to 1% of the weight of the binder is an efficient additive allowing to activate the development of the rock strength at an early age and to obtain the magnesia rock with the strength of 80 MPa and more, the water-resistance of no less than 0,8, and the hygroscopic property of no more than 2%.

Superconducting magnetic separation of phosphate using freshly formed hydrous ferric oxide sols

ABSTRACT Paramagnetic materials, such as ferric hydroxides, which are cost-effective and highly-efficient, have been little studied in relation to the magnetic separation process. In this study, freshly formed hydrous ferric oxide (HFO) sols were used to remove aqueous phosphate, followed by superconducting magnetic separation. The magnetization of HFO was determined to be 5.7 emu/g in 5.0 T. The particle size distributions ranged from 1 to 80 μm. Ferrihydrite was the primary mineral phase according to XRD analysis. Dissolved P (DP) was first adsorbed on HFO, and second, the P-containing HFO were separated by high gradient superconducting magnetic separation (HGSMS) to remove the Total P (TP). To obtain a P concentration of <0.05 mg/l in the effluent, 0.3, 1.0 and 1.3 g/l HFO were added to 2.5, 5 and 10 mg/l P solutions. The capacity of the HGSMS canister for capturing P-adsorbed HFO depends on the magnetic intensity and flow rate. In the 5.0 T HGSMS at a 1.0 cm/s flow rate, there were 75 column volumes in a single HGSMS cycle. The P concentration increased by 37.5 times after regeneration. Approximately 170 mg/l TP was measured in the backwash water.

Preparation of high performance nano-sized Cu/ZnO/Al2O3 methanol synthesis catalyst via aluminum hydrous oxide sol

Ternary Cu/ZnO/Al2O3 methanol synthesis catalysts were synthesized by co-precipitation of copper and zinc hydroxycarbonates in the presence of various aluminum hydrous oxide sol preparation methods from sodium aluminate and aluminum nitrate as aluminum oxide sources. The catalysts were characterized at various stages of preparation by nitrogen adsorption-desorption, X-ray diffraction, transmission electron microscopy, temperature programmed reduction and N2O chemisorption techniques. The TPR profiles of calcined precipitates were deconvoluted into three peaks which were assigned to the reduction of copper oxide species exhibiting different crystallite size and/or different interactions with zinc oxide. All catalysts were tested for methanol synthesis activity in a fixed-bed reactor under conditions similar to that of commercial operation (503K, 50bar and GHSV of 17250h−1), using H2, CO, and CO2 (80/12/8 molar ratio) mixture as the feed. The experimental results illustrated that the catalyst synthesized based on aluminum hydrous oxide sol prepared by peptization of aluminum hydroxide exhibited higher specific surface area, copper dispersion and catalytic activity for methanol synthesis. The catalysts thus prepared were shown to have less hydrotalcite-like phase, stronger interdispersion between Cu and ZnO and well-dispersed Cu nanoparticles with improved stability and activity in methanol synthesis from syngas.

Prospects of Use and Impact of Nanoparticles on the Properties of High-Strength Concrete

The basic properties of concrete can dramatically improve due to the unique structure of the nanosized particles. Namely, strength, frost resistance, fire resistance, corrosion resistance are increased, density and permeability are reduced; plasticity and water absorption are regulated. Despite of the huge number of advantages of nanomodified concrete, analysis of the use of nanoparticles shows that they are used quite seldom, as it requires a large cash outlay. It is not always profitable to use such additives. This article discusses some additives: magnesium nanoshpinel, microspheres, rice hull ash and metakaolin, astralenes, ferric hydroxide sol, carbon nanotubes, silica fume, nanosilica, MB-01, combined modifiers, based on iron hydroxide sol and silica sol. As well in this article sol-gel method as an additive in concrete is considered. The analysis shows that the use of nanosized particles can reduce a large amount of cement. As an addition, savings of the use are seen in reducing the cost of construction due to the low density with high strength. Accurate material consumption and maximum use of advantages of nanomodified concrete provide great prospects of implementation of this material in construction.

Hard chromium electrodeposition from a trivalent chromium bath containing water-soluble polymer

The effect of polyvinylpyrrolidones (PVPs) with different molecular weights as polymeric additives to a sulfate trivalent chromium bath was ascertained. Introduction of PVPs to the plating bath was stated to result in improvement in the surface appearance of chromium deposits and stabilization of current efficiency value in long-term electrolysis. The rate of metal deposition is practically independent of the deposition time. Thus, using PVP additive allows one to obtain high-quality Cr-coatings with a thickness of several tens of micrometers. It is found by means of turbidimetric analysis that the polymer additive has an accelerating effect on the aggregation of particles of the chromium(III) hydroxide sol formed in the near-electrode layer.