Influence of composition of sodium aluminoborosilicate melts containing nickel and calcium oxides on the wetting angle on platinum

The influence of the composition of sodium aluminoborosilicate melts containing nickel and calcium oxides on the wetting angle on platinum has been studied by the method of “small drop on thin thread.” It is shown that partial mutual replacement of silicon, aluminum, and boron oxides (up to 4 mol %) does not substantially change the wetting angle. The wetting angle increases after the partial replacement of these oxides by calcium oxide and decreases after their replacement by nickel oxide. Since a change in the surface tension of melts in the composition range studied is insignificant, the work of adhesion and the “glass melt-metallic substrate” interfacial tension are determined by the wetting angle. The maximum work of adhesion and the minimum interfacial tension are characteristic of melts with an increased nickel oxide content, and the minimum work of adhesion and the maximum interfacial tension are observed for melts with an increased calcium oxide content. Deceased.     

Potentiodynamic behaviour of graphite and platinum electrodes in sodium nitrite-potassium nitrite melts

The potentiodynamic behaviour of graphite and platinum electrodes was studied in alkaline nitrite melts. No appreciable corrosion of graphite was observed, due to the apparently low concentration of highly oxidising species. Rate processes such as NO₂^? ion oxidation. NO₂ reduction and OH^? ion oxidation were studied and interpreted with formerly discussed reaction pathways.     

Influence of oxide dopants on the wetting of doped graphite by cryolite/alumina melts

In the aluminium smelting industry, the wetting of the electrolyte on the carbon anode is an important property associated with the onset of the anode effect. The effect of dopants on the wettability of the anode was investigated in this study. The carbon material selected was graphite. The composition of the cryolite/alumina melts varied between a very low alumina content and 6 wt.% alumina. The sessile drop approach was adopted to measure the contact angle between the melt and the graphite at 1030 °C. The influence of oxide dopants, chromium III oxide and alumina, in the graphite on the wettability was studied. The wettability on a pure graphite surface depends to a small extent on the liquid surface tension but mostly on the liquid–solid interfacial tension that varies with the concentration of alumina in the liquid. The wettability on an oxide doped graphite surface depends on the dissolution of the oxide in the melt that changes the liquid–solid interfacial tension. The alumina dissolution has a double effect on the liquid–solid interfacial tension: the chemical reaction as well as the change in the oxy-anions concentration at the interface decrease the interfacial tension.     

Corrosion of nickel in sodium sulphate-sodium chloride melts. Part I

The corrosion behaviour of Ni in molten Na₂SO₄, NaCl, and in mixtures of these two salts, at 900° C, in laboratory air and under O₂+SO₂/SO₃ atmospheres has been examined by electrochemical curves and topochemical analysis of corrosion products.Ni passivity in pure Na₂SO₄ was observed under potentiodynamic and potentiometric conditions, the passive film corresponding to NiO. Passivity was not so easy to achieve in chloride melts as in sulphate alone, but once a thick oxide film forms on the specimen, the Cl^– addition is accompanied by an increase in the film stability. The inhibiting role of NaCl on Ni in the passive-transpassive area was also evidenced. In opposition, halide additions (especially those up to 25%) increased the dissolution current densities of Ni in the active region. These higher dissolution rates are represented by the equation Ni₃S₂+4NaCl+1/2 O₂ = 2NiCl₂+2Na₂S + NiO which is also suggested as a critical factor in the Ni passivation.The passive capability found for Ni in Na₂SO₄/NaCl melts, in air, is destroyed by SO₃ atmospheres. This corrosion-stimulation is due to the SO₃ role in promoting reactions such as NiS + 3O^2– = Ni²⁺+SO₃+8e which would be potential-determining at the Ni surface until Ni²⁺ precipitates or the conjugate oxygen cathodic reduction process takes place. Microprobe analysis also evidenced S penetration which might be the reason for the Ni embrittlement.The polarization curves for Ni in pure NaCl showed the lack of a passive region; occurrence of extensive intergranular attack was also indicated by metallographic observation. The observed dissolution must occur at the expense of the Ni interactions with the species which intervene in the reaction equilibrium between O₂ and molten NaCl (O₂, Cl^–, Cl₂ and O^2–) as well as with the Na⁺ cations, as has been discussed elsewhere. Its self-sustaining nature is enhanced by the continuous reduction of the nickel ion content of the melt by NiCl₂ evaporation.     

Influence of rare earth oxides on kinetics and reaction mechanisms in CMAS silicate melts

Dissolution of different rare earth oxides RE₂O₃ and cyclosilicate Ca₃RE₂(Si₃O₉)₂ was studied at 1200 °C in a pseudo-ternary CAS melt. This investigation is relevant to CMAS resistant thermal barrier coatings (TBC) used in aircraft engines. CMAS is a generic term for the molten siliceous deposits resulting from the ingestion of mineral particles with the intake air. The aim was to assess the influence of the rare earth on the reaction kinetics, solubility limits and underlying phase equilibria in a model CAS melt. RE₂O₃ (RE = Nd, Sm, Gd, Dy and Yb) were selected to span a wide range of trivalent lanthanide sesquioxides and Lewis basicities. Powders dispersed in CAS glass-beads were reacted at 1200 °C and quenched after several durations. All the RE₂O₃ led to the formation of metastable apatite, and then to stabilization of cyclosilicate in CAS. Disilicate Yb₂Si₂O₇ was also obtained in Yb₂O₃ bead-sample during early-stage of interaction. However, RE₂O₃ oxide basicity has a direct influence on silicates (apatite, disilicate and cyclosilicate) solubility limits in CAS, on RE-apatite crystal growth as well as on induction time for RE-cyclosilicate nucleation. The results are discussed in the light of crystal chemistry, thermodynamic considerations and RE cation field strength (Z/r²) which is alternative to define oxide basicity.     

Voltammetric behaviour of platinum in aqueous solutions containing sodium hypophosphite

The anodic and cathodic behaviour of polycrystalline Pt in sodium hypophosphite solutions has been investigated by cyclic voltammetry. In acid solutions the voltammograms show that, owing to the presence of the reducing agent, electrooxidation of species related to H₃PO₃ occurs in the potential range 0.6 to 1.4 V with respect to NHE. In alkaline solutins the presence of NaH₂PO₂ partially inhibits the HER and displaces the formation of the oxygen monolayer on platinum to higher potentials. The voltammetric peaks are attributed to the electrooxidation of the products resulting from the chemical decomposition of NaH₂PO₂ in contact with the Pt surface.     

Indentation cracking and deformation mechanism of sodium aluminoborosilicate glasses

Developing less brittle oxide glasses is a grand challenge in the field of glass science and technology, as it would pave the way toward new glass applications and limit the overall raw material usage and energy consumption. However, in order to achieve this goal, more insight into the correlation between the chemical composition and material properties is required. In this work, we focus on the mechanical properties of quaternary sodium aluminoborosilicate glasses, wherein systematic changes in glass chemistry yield different resistances to indentation crack initiation. We discuss the origin of the composition dependence of indentation cracking based on an evaluation of the deformation mechanism taking place during the indentation event. To this end, we use a simple metric, the extent of indent side length recovery upon annealing, to quantify the extent of reversible volume deformation. Finally, we also compare the compositional trend in crack initiation resistance to that in crack growth resistance (fracture toughness), showing no simple correlation among the two.     

QHS-3型钠钙浮选剂用催化剂生产过程中含铜、镍离子废水的处理

对QHS-3型钠钙浮选剂用催化剂生产过程中产生的含铜、镍离子废水采用常规中和沉淀法与加入金属螯合剂M相结合的方法进行了去除铜、镍离子的研究,结果表明:在最佳工艺条件下,即在溶液的pH值为9.2,聚丙烯酰胺(PAM)加入量为6 mg/L,金属螯合剂M投加量为80～90 mg/L时,处理后的废水中的铜、镍离子的质量浓度达到了国家排放标准.     

Reaction of sodium metaphosphate with magnesium and calcium oxides and their mixtures

Conclusions The reactions of MgO and CaO with aqueous solutions of sodium metaphosphate give products in the form of acid orthophosphates. The formation of the acid orthophosphates proceeds in accordance with the schemes: MgO +nNaPO₃=Na_mMgH_2(m–1) (PO₄)_m·aH₂O+(n}-m) NaH₂PO₄·bH₂O, where m=n when n=1, 2, or 3; m=3 when n is greater than 3, and CaO +nNaPO₃=Na _m CaH₂(m–1) (PO₄)_m·aH₂O + (n–m) NaH₂PO₄·bH ₂O. where m=n when n=1 or 2; m=2 when n is greater than 2.The drying process after the reaction of an aqueous solution of sodium metaphosphate with a 11 mix of CaO + MgO results in the formation of NaCaPO₄·nH₂O and Mg(OH)₂ while a 21 mix gives Na₂CaMg(PO₄)₂· nH₂O.When using crystalline sodium metaphosphate the formation of the sodium-calcium orthophosphate and bryanite passes through the intermediate phases Na₂CaP₂O₇ and Na₈Ca₄MgP₈O₂₉.The temperature range of the reaction of the formation of bryanite in the mixes CaO + MgO + 2NaPO₃ depends on the activity of the MgO. When electrofused MgO of varied grain size is used, the formation of bryanite passes through intermediate stages; the temperature range of the reaction giving Na₂CaMg(PO₄)₂ shifts towards higher temperatures with an increase in the grain size of the original MgO.Translated from Ogneupory, No. 5, pp. 51–58, May, 1978.     

Viscosity-structure relationship of alkaline earth silicate melts containing manganese oxide and calcium fluoride

The effect of CaF₂ on the viscosities of the MO-SiO₂-xMnO-yCaF₂ melts (M[=Ca or Ba]O/SiO₂ = 0.4-0.5, x = 10[±1] or 40[±2] mol%, y = 0-15 mol%) have been studied at high temperatures. At MnO = 40[±2] mol%, the viscosity of Ba-Mn-silicate melts is lower than that of Ca-Mn-silicate melts because Mn²⁺ is a strong network modifier in the former system. However, the viscosities of both alkaline earth silicate melts with MnO = 10[±1] mol% are not affected by cation type because MnO activity is too low to affect the viscosity of the melts. The CaF₂ addition decreases the viscosities of the Ba-Mn-silicate melts with low-MnO contents, while it has less impact on the viscosities of the melts with high-MnO contents. The effect of CaF₂ on the relationship between viscosity and the structure of the silicate melts is quantitatively analyzed using the micro-Raman spectra of quenched glass samples. The NBO/Si ratio of alkaline earth silicate melts, which indicates the degree of polymerization of the silicate networks, has a linear relationship with the activation energy for the viscous flow of the melts.     

Corrosion of nickel in sodium sulphate-sodium chloride melts. II. Potential-time and topochemical studies

The corrosion behaviour of Ni in molten Na₂SO₄, NaCl, and in mixtures of these salts at 900° C, has been studied by electrochemical and topochemical methods. Microprobe analysis showed deep S penetration which causes embrittlement of the specimens by intergranular attack.     

Influence of the gas atmosphere on restructuring and sintering kinetics of nickel and platinum aerosol nanoparticle agglomerates

The kinetics of the primary particle growth and the restructuring of nanoparticle agglomerates of Ni and Pt were studied under variation of temperature and gas composition. The aerosol particles used in the study were produced by spark discharge into nitrogen as carrier gas. Restructuring was monitored by measuring the mobility equivalent diameter by SMPS after different residence times in a tempered volume. To determine the kinetics of primary particle growth, samples were taken over a range of residence times for TEM analysis. These experiments were conducted in reducing atmospheres and in pure nitrogen to study the effect of surface state on the kinetics of the processes. To quantify sintering kinetics, a multi-stage sintering model based on the reduction of the surface energy was fitted to the experimental results.

A strong dependence of the primary particle growth and the agglomerate restructuring on the surface state of the particles was found. Both processes were accelerated strongly with increasing purity of the particle surfaces. The model yielded an activation energy for the primary particle growth of Ni-agglomerates in pure nitrogen (99.99%) of about 80 kJ/mol which was decreased for reduced Ni and Pt particles to a value of about 50 kJ/mol. The kinetics of restructuring was much faster than the one for primary particle growth. This enables the seperation of the manipulations of agglomerate structure and primary particle size.     

Optic properties of niobium-phosphate glasses containing lithium,sodium, and potassium oxides

The dependence of the optic properties of niobium-phosphate glasses containing alkali metal oxides on their composition and structural features is investigated. Along with the increase of the niobium oxide content, a shift of the optic absorption boundary to the long-wavelength range and a substantial increase of the refraction index (from 1.50 to 1.73) are observed. The increase of the alkali metal mass results in the decrease of the refraction index and a shift to the short-wavelength range. The correlation between the length of polyphosphate groups and the type of alkali oxide is registered: the chain length increases from lithium to potassium.     

Electrochemical characteristics of cobalt-substituted lithium nickel oxides synthesized from lithium hydro-oxide and nickel and cobalt oxides

LiNi_1−yCo_yO₂ (y=0.1, 0.3 and 0.5) were synthesized by solid state reaction method at 800 °C and 850 °C from LiOH·H₂O, NiO and Co₃O₄ as starting materials. The electrochemical properties of the synthesized LiNi_1−yCo_yO₂ were investigated. As the content of Co decreases, particle size decreases rapidly and particle size distribution gets more homogeneous. When the particle size is compared at the same composition, the particles synthesized at 850 °C are larger than those synthesized at 800 °C. LiNi_0.7Co_0.3O₂ synthesized at 850 °C has the largest intercalated and deintercalated Li quantity Δx among LiNi_1−yCo_yO₂ (y=0.1, 0.3 and 0.5). LiNi_0.7Co_0.3O₂ synthesized at 850 °C has the largest first discharge capacity (178 mAh/g), followed by LiNi_0.7Co_0.3O₂ (162 mAh/g) synthesized at 800 °C. LiNi_0.7Co_0.3O₂ synthesized at 800 °C has discharge capacities of 162 and 125 mAh/g at n=1 and n=5, respectively.     

Elasticity,hardness, and fracture toughness of sodium aluminoborosilicate glasses

Due to an increasing demand for oxide glasses with a better mechanical performance, there is a need to improve our understanding of the composition-structure-mechanical property relations in these brittle materials. At present, some properties such as Young's modulus can to a large extent be predicted based on the chemical composition, while others—in particular fracture-related properties—are typically optimized based on a trial-and-error approach. In this work, we study the mechanical properties of a series of 20 glasses in the quartenary Na₂O–Al₂O₃–B₂O₃–SiO₂ system with fixed soda content, thus accessing different structural domains. Ultrasonic echography is used to determine the elastic moduli and Poisson's ratio, while Vickers indentation is used to determine hardness. Furthermore, the single-edge precracked beam method is used to estimate the fracture toughness (K_Ic) for some compositions of interest. The compositional evolutions of Vickers hardness and Young's modulus are in good agreement with those predicted from models based on bond constraint density and strength. Although there is a larger deviation, the overall compositional trend in K_Ic can also be predicted by a model based on the strength of the bonds assumed to be involved in the fracture process.     

Effect of twist angle and linear density of man-made complex yarns on contact wetting angle

Conclusions Contact wetting angles have been determined on complex twisting viscose, polyamide, and polypropylene yarns by the method of measuring a drop resting on the yarn.It has been found that the type of yarn, its linear density, and the twist angle affect the magnitude of the contact wetting angle.Translated from Khimicheskie Volokna, No. 3, pp. 41–42, May–June, 1988.     

Studies on flow behaviors of polymer melts in nanochannels by wetting actions

The flow behavior of polymer melts in nanochannels by wetting actions was investigated by statistical analyses of generated polymer nanofibers' length in nanochannels of nanoporous alumina template using Scanning Electron Microscopy. The polyethylene nanofibers with high aspect ratio are formed after the infiltration of melts into the alumina nanochannels by wetting actions. The wetting of polyethylene melts in nanochannels is a rapid process due to the high surface free energy of inner walls and wetting driven force. Wetting and flow rate of polymer melts in nanochannels are mainly dependent on the wetting temperature, the size of nanochannels and surface properties of nanochannels adjusted by octadecyltrimethoxysilane self-assembled monolayers. High surface free energy and solid–liquid interaction between melts and surface lead to noticeable flow of polymer melts in nanochannels at the wetting stage.