The effects of surface treated carbon fibers and CaCO<Subscript>3</Subscript> nanoparticles inclusions on the mechanical performances of PA6/ABS-based composites

The mechanical and morphological characteristics of PA6/ABS (60/40)-based hybrid composite containing HNO₃-treated short carbon fibers (HSCF) and CaCO₃ nanoparticles have been experimentally studied. A counter-rotating twin-screw extruder and an injection molding machine were employed to produce different samples containing 10 wt % of HSCF and 0, 2, 5 and 8 wt % of CaCO₃ nanoparticles. The SEM observations indicated high-quality adhesion between HNO₃-surface treated carbon fibers and PA6/ABS polymer matrix. In addition, the morphological studies showed that the inclusion of CaCO₃ nanoparticles caused a significant effect on the ABS particle dispersion in PA6/ABS matrix. The mechanical properties assessments revealed that the incorporation of 10 wt % HSCF into the PA6/ABS can significantly improve tensile strength (82%), tensile modulus (107%), flexural strength (98%), flexural modulus (104%) and impact resistance (24%). The inclusion of CaCO₃ nanoparticles, in the presence of 10 wt % HSCF, led to the noticeable improvements of tensile strength (128% for 2 wt % CaCO₃), tensile modulus (199% for 5 wt % CaCO₃), flexural strength (146% for 5 wt % CaCO₃), flexural modulus (204% for 5 wt % CaCO₃) and impact resistance (46% for 2 wt % CaCO₃). The surface treatment of carbon fibers, dispersion conditions of nanoparticles and ABS phase in polymeric matrix were found to be the major important factors affecting the mechanical properties.     

Experimental investigation on the mechanical properties of Co-polypropylene/GF/CaCO<Subscript>3</Subscript> hybrid nanocomposites

This study aimed to acquire a balance of mechanical properties comprising impact, tensile and flexural performances in PP based blend. In this respect, co-PP was employed as matrix because of its intrinsic high impact behavior. Hybrid nanocomposites based on co-PP and containing 10 wt % micron-sized short glass fibers (GF) and 2 to 8 wt % nano precipitated CaCO₃ (NPCC) particles were produced by applying a two-step melt compounding method. Maleic anhydride grafted polypropylene (MAPP) was used as compatibilizer. Strong glass fiber-matrix adhesion and relatively uniform distribution of nano-CaCO₃ particles were observed in SEM images. The maximum tensile strength was observed in co-PP hybrid nanocomposite containing 10 wt % glass fiber and 5 wt % nano-CaCO₃ which was 58% more than that of neat co-PP. Flexural strength raised as much as 11% by adding glass fiber. The maximum flexural strength was obtained by incorporating 10 wt % glass fiber and 8 wt % nano-CaCO₃ into co-PP matrix which was 24% higher than that of neat co-PP. The impact strength decreased upon addition of 10 wt % glass fiber and 5 and 8 wt % nano-CaCO₃, this was attributed to the inherent high impact behavior of co-PP as well as strong interfacial interaction between dispersed phases and polymeric matrix.     

Peanut-shaped aggregation of CaCO<Subscript>3</Subscript> crystallites in the presence of an amphiphilic derivative of carboxymethylchitosan

An amphiphilic derivative of carboxymethylchitosan (CMCS), (2-hydroxyl-3-butoxyl)propyl-CMCS (HBP-CMCS), was used as an organic additive in the precipitation process of calcium carbonate (CaCO₃). HBP-CMCS molecules can interact with calcium ions, the functional groups of which act as active sites for the nucleation and crystallization of CaCO₃. Simultaneously, HBP-CMCS molecule also functionalizes as a colloidal stabilizer to prohibit the sedimentation of the grown CaCO₃ crystals, depending upon the molar ratio of the initial Ca²⁺ ions to the repeat units of HBP-CMCS molecules. The combination investigations of scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy on the precipitated CaCO₃ crystals proved that concentrations of HBP-CMCS and Ca²⁺ exert great influence on the crystallization habit of CaCO₃, such as the nucleation, growth, morphology, crystal form, etc. The formation of the peanut-shaped CaCO₃ particles suggests the template effect of HBP-CMCS molecules on the aggregation behavior of CaCO₃ nanocrystals.     

Influence of CaCO<Subscript>3</Subscript> nanoparticles shape on thermal and crystallization behavior of isotactic polypropylene based nanocomposites

Summary The influence of calcium carbonate nanoparticles with different shapes (spherical and elongated) on the thermal properties and crystallization behavior of isotactic polypropylene was investigated. CaCO₃ nanoparticles were covered by an appropriate coating agent to improve the interfacial adhesion between the filler and the polyolefin matrix. The nanocomposites were prepared by melt mixing and subsequent compression molding. A remarkable effect of CaCO₃ on the thermal properties of iPP was observed. Moreover, the analysis of crystallization kinetics showed that CaCO₃ nanopowder coated with PP-MA are efficient nucleating agents for iPP, and the overall crystallization rate results higher than plain iPP.     

The role of pyruvic acid as starting material in some organic reactions in the presence of SBA-Pr-SO<Subscript>3</Subscript>H nanocatalyst

Pyruvic acid contains three different reactive positions: –COOH, ketone carbonyl and methyl groups. Correspondingly, pyruvic acid was applied as starting material in the modified Niementowski reaction and Aldol condensation using SBA-Pr-SO₃H as an efficient nanocatalyst. Aldol condensation of pyruvic acid and oxindole provided a new oxindol-based carboxylic acid which was subsequently used in the Ugi four-component reaction. Moreover, through the modified Niementowski reaction of pyruvic acid, new derivatives of quiazoline were produced in the presence of SBA-Pr-SO₃H. The obtained products are important due to their potentially biological active skeletons.     

A study of the interaction between polyelectrolyte-coated nanostructured CaCO<Subscript>3</Subscript> particles and a stearic acid monolayer spread at the water/air interface

The influence of nanostructured CaCO₃ particles, both uncoated and coated with a polyelectrolyte (poly(diallyldimethylammonium chloride), polyethyleneimine, fluorescein-5-isothiocyanate-labeled poly(allylamine hydrochloride), or sodium polystyrene sulfonate), on a stearic acid monolayer spread on the surface of an aqueous subphase has been studied. The interaction of the particles present in the subphase with the monolayer as depending on the presence and composition of a polymer coating has been estimated with the help of compression isotherms and the Brewster angle microscopy. The monolayers were transferred from the aqueous subphase onto a solid substrate and studied by scanning electron microscopy. Strong interaction has been revealed between the calcium carbonate particles and the stearic acid monolayer. It has been shown that the transfer of the monolayer from the aqueous suspension surface onto the solid substrate may be accompanied by the detachment of the polymer coating from the surface of CaCO₃ particles or their transfer together with the monolayer.     

Biomimetic Nucleation and Morphology Control of CaCO_3 in PAAm Hydrogels Synthesized from Lyotropic Liquid Crystalline Templates

Hydrogels have been thought to be the material which can provide appealing replacements of biological organisms. Pores of hydrogels synthesized from lyotropic liquid crystalline (LLC) templates were smaller in size and more uniform than those of traditional hydrogels. LLC poly‐acrylamide (PAAm) hydrogels were used as the growth media of CaCO₃. After copolymerized with acrylic acid and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), LLC hydrogels were modified with COOH and SO₃H, respectively. The effect of functional groups on the biomimetic mineralization of CaCO₃ was studied. Most of crystals from traditional hydrogels are rhombohedral and could not form aggregates. Only a few could aggregate and have a particular morphology with irregular orientation of subcrystal. Compared with crystals separated from traditional hydrogels, crystals growing in the LLC hydrogels were much more regulated and could form aggregates with particular morphology and regular orientation, that is, face (104) of rhombohedral subcrystals parallel to the surface of the macrocrystals. Modification of COOH and SO₃H groups made CaCO₃ subcrystal align more tightly. COOH had minor influences on the crystal orientation and small modification to the aggregate morphology. SO₃H groups could change the crystal orientation and morphology effectively. The aggregates are pseudo‐spherical and the face perpendicularity to the face (104) parallels to the surface of the aggregates.     

Reaction pathways of carboxylic acids over TiO<Subscript>2</Subscript> single crystal surfaces: diketene formation from bromo-acetic acid

This work presents the first investigation of a halo-carboxylic acid (Br-CH2COOH) over the surface of an oxide single crystal (the {011}-faceted TiO₂(001) single crystal). A very rich chemistry is observed. This is broadly divided into three categories: elimination of HBr to make ketene, dimerisation of two molecules of ketene to 4-methyl-2-oxetanone and 1,3-cyclobutanedione, and further reaction of the latter to a mass spectrometer m/e 70 signal attributed to crotonaldehyde (formed by ring opening). Temperature programmed desorption (TPD) and Scanning Kinetic Spectroscopy (SKS) gave complementary results with SKS opening a simple way for investigating surface chemical reactions in UHV conditions with high surface coverage at still high temperatures. A successful modeling of SKS data was conducted providing the activation energies (E _a) for ketene desorption, with a reaction order n close to 1, for both CH₃COOH (E _a = 21.3 kcal/mol) and BrCH₂COOH (E _a = 17.2 kcal/mol). In order to further understand the surface reaction of BrCH₂COOH semi-empirical PM3 computation of its adsorption and reaction on a Ti₈O₂₉H₂₆ cluster representing the (011) TiO₂ surface was conducted and compared to that of CH₃COOH on the same cluster. Dissociative adsorptions of both the O-H and C-Br bonds are more stable than the non-dissociative adsorption modes. The di-coordinated species, TiOC(O)CH₂O_s, formed by the simultaneous dissociation of both C-Br and O-H bonds of BrCH₂COOH appears the most plausible surface intermediate for the observed carbon coupling reactions.     

Polytherm of the CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>–KNO<Subscript>3</Subscript>–H<Subscript>2</Subscript>O phase diagram

The crystallization polytherm of the ternary CO(NH₂)₂–KNO₃–H₂O system is plotted for the first time via visual polythermal analysis and calculating ternary eutonics characteristics from data on the boundary elements of two-component systems. The ternary eutonics modeling error does not exceed 3.5%. In addition to the crystallization fields of individual components, the field of the redox reaction that occurs in the system between potassium nitrate and carbamide is shown in the CO(NH₂)₂–KNO₃–H₂O diagram by a dashed outline.     

Reaction of Sulfur and Oxygen-Bridged 8-Quinolinolato Trinuclear Molybdenum Cluster [Mo<Subscript>3</Subscript>OS<Subscript>3</Subscript>(qn)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>3</Subscript>]<Superscript>+</Superscript> with Acetylene Carboxylic Acids

The reaction of a sulfur and oxygen-bridged 8-quinolinolato trinuclear molybdenum cluster [Mo₃OS₃(qn)₃(H₂O)₃]⁺ (3; Hqn = 8-quinolinol) with equimolar amounts of acetylene carboxylic acid, 4-pentynoic acid, 5-hexynoic acid, acetic acid, and pimelic acid gave clusters having μ-carboxylato groups, [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡CCOO)] (6), [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡C(CH₂)₂COO)] (7), [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡C(CH₂)₃COO)] (8), [Mo₃OS₃(qn)₃(H₂O)(μ-CH₃COO)] (4), and [{Mo₃OS₃(qn)₃(C₂H₅OH)}₂(μ-C₇H₁₀O₄)] (5), respectively. X-ray structural analyses, ¹H NMR, and electronic spectra of these clusters made clear that each of the COO⁻ groups of the reagents bridges two Mo atoms in each cluster and that no adduct formation occurred at the sulfurs in the clusters. The reaction of 3 with a large excess-molar amount (50 times) of acetylene carboxylic acid gave [Mo₃OS(μ₃-SCH=C(COOH)S)(qn)₃(H₂O)(μ-HC≡CCOO)] (9) with two molecules of acetylene carboxylic acid, one acting as a carboxylato bridge and the other in adduct formation, as supported by the electronic and ¹H NMR spectra. The corresponding aqua cluster [Mo₃OS₃(H₂O)₉]⁴⁺ (1), on the contrary, reacts with acetylene carboxylic acid to give adduct [Mo₃OS(μ₃-SCH=C(COOH)S)(H₂O)₉]⁴⁺ (2). Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

CNTs表面改性与TiO2-CNTs异质结光催化性能

碳纳米管(CNTs)混酸(H₂SO₄/HNO₃, 体积比为3:1)超声辅助纯化及氧化植入活性基团－COOH, 进一步借助其转化为酰氯基团, 分别于CNTs 表面共价嫁接亲水性赖氨酸及亲脂性正十八胺基团, 赋予赖氨酸表面改性CNTs 显著水溶(6.85 mg·mL-1)和十八胺表面改性CNTs 显著醇溶(10.15 mg·mL^-1)性能. 运用低温水热法以亲水性CNTs 复合TiO₂, 溶胶-凝胶法以亲脂性CNTs 复合TiO₂, 观察到复合催化剂光催化性能随CNTs 溶剂分散性能增加而明显提升. 运用傅里叶变换红外(FTIR)、激光拉曼、X射线衍射(XRD)、Brunauer-Emmett-Teller 低温氮气吸附、透射电镜(TEM)及X光电子能谱(XPS)等手段表征, 系统探讨CNTs 的表面改性机制及CNTs 溶解分散性能与复合催化剂的光活性的关联. 认为表面改性CNTs 借助Ti－O－C键合促进其与纳米TiO₂的异质结合, 从而充分利用CNTs的大比表面积及电荷传输性能促进催化剂的污染物光催化降解.     

Effects of macromolecules on the crystallization of CaCO3 the Formation of Organic/Inorganic Composites

The effects of macromolecules as soluble additives and solid matrices have been examined for the crystallization of CaCO₃. A vaterite form grows on a glass substrate in the presence of poly(glutamic acid) (PGA) containing a carboxylic acid group as a soluble additive. In contrast, no crystal growth has been observed when poly(acrylic acid) (PAA) exists as an additive though it has the same functional group. The conformation or the backbone structure of the polymers may have an influence on the crystal polymorph of CaCO₃. Thin film states of CaCO₃ crystals have been obtained as organic/inorganic composites with chitosan that acts as a solid matrix in the presence of PAA or PGA as a soluble additive.     

Investigation of photo‐oxidative effect on morphology and degradation of mechanical and physical properties of nano CaCO3 silicone rubber composites

Photo‐oxidative degradation of treated and untreated nano CaCO₃: silicone rubber composite was studied under accelerated UV irradiation (≥290 nm) at different time intervals. Prolonged exposure to UV leads to a progressive decrease in mechanical and physical properties along with the change in behavior of filler‐matrix interaction. This was due to decrease in cross‐linking density with increase in mobility of rubber chains. Meanwhile, synthesized nano CaCO₃ was modified with stearic acid for uniform dispersion in rubber matrix. The increase in carbonyl (>CO), hydroxyl (? OH), CO₂, and alkene functional groups on the UV exposed surface of treated and untreated nano CaCO₃: silicone rubber composites at different time intervals was studied using Fourier transform infrared (FTIR) spectroscopy. The change in morphological behavior of filler‐matrix interaction after UV exposure was studied using SEM. Overall, the study showed that the treated nano CaCO₃: silicone composites were affected more by UV exposure than untreated nano CaCO₃: silicone composites and pristine composite after UV exposure. This effect was due to peeling of stearic acid from the surface of CaCO₃, which makes the rubber chains slippery and thus separation of filler and rubber chains takes place with initiation of fast‐degradation. Copyright © 2011 John Wiley & Sons, Ltd.     

Protonation of the Dodecahydro-<Emphasis Type="Italic">closo</Emphasis>-Dodecaborate Anion in CH<Subscript>3</Subscript>CN/CF<Subscript>3</Subscript>COOH

The behavior of the [B₁₂H₁₂]^2– anion in CH₃CN, CF₃COOH, and the CH₃CN/CF₃COOH system is studied by IR spectroscopy. Based on the IR spectroscopy data correlated with the data obtained when studying the protonation processes of boron cluster anions [B₆H₆]^2– and [B₁₀H₁₀]^2–, the possibility to prepare the protonated form of the closo-dodecaborate anion, namely monoanion [B₁₂H₁₃]^–, is concluded in CF₃COOH and the CH₃CN/CF₃COOH system. In the IR spectra of salts of the protonated forms of anions [B_nH_n]^2– (n = 6, 10, 12) in solutions and Nujol mulls, a high-frequency shift of the ν(BH) absorption bands is observed as compared with the spectra of salts of non-protonated anions Cat₂[B_nH_n] (Δν = 70–100 cm^–1).     

Study of the composition and properties of products formed in interaction of Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> with proton-containing reagents

Composition and properties were studied of products formed in treatment of solid Na₂CO₃ with aqueous solutions containing acetic and citric acids with mass fractions of 0.40–0.60 and 0.33–0.49, respectively, at a Na₂CO₃/H _x An molar ratio of 2–6, where H _x An = CH₃COOH and H₃(C₆H₅O₇). It was found that the content of water in the systems under study and the strength of an acid affect the yield of the double salt of carbonic acid, Na₂CO₃·NaHCO₃·2H₂O and the composition of derivative proton-containing compounds. It is noted that sodium sesquicarbonate can be formed both by the crystallization mechanism and via a transformation of the primary structure of sodium carbonate. In the resulting powder-like products, water introduced with the acid solution is predominantly consumed for formation of crystal hydrates of carbonate-containing and derivative proton-containing compounds. The hygroscopic point of the resulting salt formulations was determined to be at a level of 70–75%. It was noted that sesquicarbonate-containing salt formulation formed in “dry” neutralization of sodium carbonate by acid solutions can be regarded as a builder for obtaining synthetic household detergents.     

Preparation and selected properties of pigments on base of Ln-doped CaSnO<Subscript>3</Subscript>

Inorganic pigments containing lanthanides based on orthorhombic perovskite structure of CaSnO₃ have been prepared by solid state reaction of CaCO₃, SnO₂ and lanthanide oxides (Tb₄O₇, Pr₆O₁₁, CeO₂). The TG-DTA analysis indicates the formation of Ca-stannates around of temperature 1200°C, but from the pigmentary — application point of view, it is better to synthesize the product at higher temperature (1400 or 1500°C). The resultant materials were characterised by XRD, particle size distribution and measurement of colour properties. The doping of Ca-stannates by ions of rare earth elements (Tb, Pr, Ce) brings the production of two-and three-phase systems. The most interesting colour properties provided the stannate doped by ions of terbium and cerium and synthesized by heating at temperature 1400°C. The pigment has reddish brown colour hue.     

Synthesis and characterization of well-defined poly(methyl methacrylate)/CaCO3/SiO2 three-component composite particles via reverse atom transfer radical polymerization

The attempt to prepare structurally well-defined polymer/inorganic composite particles, i.e., poly(methyl methacrylate) (PMMA)/CaCO₃/SiO₂ three-component composite particles, via reverse atom transfer radical polymerization (ATRP), using 2-2′-azo-bis-isobutyronitrile as initiator and Cu(II) bromide as catalyst was reported. CaCO₃/SiO₂ two-component composite particles were first obtained through sol–gel method, and their morphology and surface element information were determined by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The results indicate that the CaCO₃ was encapsulated by the obtained SiO₂. After being modified by silane coupling agent, the CaCO₃/SiO₂ composite particles copolymerized with methyl methacrylate (MMA) under standard reverse ATRP conditions to produce PMMA/CaCO₃/SiO₂ three-component composite particles. In the case concerned, first-order kinetic plots and linear increase of molecular weight (Mn) vs conversion and narrow molecular weight distribution for the graft polymer samples were observed. Furthermore, the gel permeation chromatography results illustrated that both the free PMMA chains from the solvent and the graft PMMA chains from the surface of CaCO₃/SiO₂ two-component composite particles were growing at the same rate. Characterizations of the PMMA-grafted CaCO₃/SiO₂ composite particles were done by Fourier transform infrared and thermogravimetric analysis. The results showed that the surface of the modified inorganic particles was grafted by the MMA and that the grafting percentage was about 8.7%.     

Quantum-chemical analysis and experimental study of the process of the silica surface interaction with the CrO<Subscript>2</Subscript>Cl<Subscript>2</Subscript> and VOCl<Subscript>3</Subscript> vapor mixture

We accomplished a synthesis of the two-component vanadium-chromium containing monolayer on the silica surface by treating the latter with a mixture of CrO₂Cl₂ and VOCl₃ vapors. Analysis of the chemical reactions on the substrate surface is carried out using quantum-chemical modeling. The calculated VOCl₃ reactivity is higher than that of CrO₂Cl₂, which requires the use of an excess of the chromium oxychloride in the reaction mixture to provide a control over the coating composition in a wide range of concentrations. The quantitative forecast of the reaction product composition indicates a significant role of the synthesis temperature and structural strain at the formation of the monolayer. We carried out an experimental synthesis of the two-component coating by the method of molecular layering (ML) under the conditions derived from quantum-chemical predictions, at a concentration ratio of chromium and vanadium in the range from 0.5 to 2.6, and showed the ability of control over the product composition. Based on a comparison of experimental and calculated data the structural strains and the quantitative ratio of the surface centers of different local structure were estimated. The results obtained using infrared Fourier spectroscopy confirm the agreement between the experimental data and the quantum-chemical predictions.     

Influence of N,O-carboxymethyl chitosan on the properties of octadecanoic acid/octadecylamine monolayers and the fractal structure of calcium carbonate

The properties of octadecanoic acid-otctadecylamine monolayers and growth of calcium carbonate (CaCO₃) induced by the monolayers on the surface of supersaturated CaCO₃ solution with N,O-carboxymethyl chitosan (CMC) are studied. The results suggest that CMC is either adsorbed on or inserted into the monolayers, as is confirmed by π-A, dπ/dA-A, and π-t isotherms. The adsorption of CMC changes the properties of the monolayers, a process that results in the transformation of the shape of CaCO₃ particles from crystal-like into the fractal pattern beneath the monolayers. Different fractal morphologies, such as butterfly and wicker branches consisting of hollow ellipsoidal, solid ellipsoidal, and spherical particles, correspondingly, are observed; these morphologies depend on the CMC concentration in the subphase. The dimensions of fractal patterns are determined. The mechanisms of the formation of CaCO₃ crystals and fractal structures are discussed. The text was submitted by the authors in English.     

Electrodeposition of thin Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> films

The electrochemical behavior of copper(II), zinc(II), and thiosulfate (S₂O₃ ^2-) ions on the molybdenum electrode in individual 0.2 М sodium sulfate solutions (рН 6.7) and with addition of either 0.1 М tartaric acid (рН 4.6) or 0.1 М citric acid (рН 4.7) is studied. A one-step electrochemical method is developed for the deposition of thin Cu₂ZnSnS₄ films, which is carried out on the molybdenum electrode at a constant potential in sodium sulfate solutions containing tartaric acid. The effect of the concentration of electrolyte components on the chemical composition of Cu₂ZnSnS₄ films is determined. The phase composition is confirmed by the Raman spectroscopy data. The surface morphology of synthesized films is studied by means of scanning-electron and atomic-force microscopes. The photoelectrochemical characteristics of Cu₂ZnSnS₄ films are determined. Samples of these coatings on the Mo electrode are found to be highly photosensitive.