Creation of a new material stream from Japanese cedar resources to cellulose nanofibrils

Japanese cedar is one of the most abundant plantation softwoods in Japan, although it is not effectively utilized as a wood resource. Japanese cedar cellulose was isolated and subjected to one-pot catalytic oxidation and reduction with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and NaBH₄, respectively. The TEMPO-oxidized and NaBH₄-reduced Japanese cedar celluloses (TOCs-NaBH₄) had carboxylate content of up to 1.4 mmol/g and viscosity-average degrees of polymerization from 2000 to 3000. The X-ray diffraction patterns of the TOCs-NaBH₄ showed that the crystal widths were ~ 3 nm, indicating that the C6-OH groups present on the crystalline cellulose microfibril surfaces were selectively oxidized to C6-carboxylate groups. When the TOCs-NaBH₄ with carboxylate content of 0.9–1.4 mmol/g were mechanically disintegrated in water, transparent TEMPO-oxidized cellulose nanofibril (TOCN) dispersions were obtained. The lengths of the TOCNs, determined from their atomic force microscopy images, varied from 800 to 1500 nm, depending on the oxidation conditions. The TOCNs prepared from Japanese cedar cellulose have an average of high aspect ratios (> 300), which is greater than that (~ 150) prepared from wood pulp and thus advantageous.     

3-<Emphasis Type="Italic">O</Emphasis>-Propyl cellulose: cellulose ether with exceptionally low flocculation temperature

The synthesis of 3-O-propyl cellulose with degree of substitution (DS) ranging from 0.19 to 1.02 was carried out via 2,6-di-O-thexyldimethylsilyl cellulose. The products were characterized by means of one- and two-dimensional NMR spectroscopy after peracetylation. The dissolution behavior of 3-mono-O-propyl cellulose in water was studied and compared with propyl cellulose derivatives having different degree of substitution and distribution of functional groups. Depending on the DS, exceptionally low flocculation temperatures between 15 and 23 °C were found for 3-O-propyl celluloses.     

A wet-chemical method for the synthesis of in-doped CaZrO3 ceramic powders

Both CaZr_0·9In_0·1O_3-α ceramics and ceramic nano-powders are synthesized starting from a co-precipate formed using a wet-chemical co-precipitation method. The XRD-results confirm that CaZrO₃ and CaIn₂O₄ phases exist after the co-precipitates are calcined at 1273 K for 3 h in air. The CaIn₂O₄ phase disappears after calcining the powder twice at 1823 K for 10 h in air with the formation of the CaZr_0·9In_0·1O_3-α phase. The XRD pattern of the ceramic powders is the same as that of sintered CaZr_0·9In_0·1O_3-α ceramics (1823 K for 10 h in air). Scanning electron microscopy shows that the ceramic powders calcined at 1273 K for 3 h are nano-sized powders. After sintering at 1823 K for 10 h, the grain-size increases dramatically. EDX results indicate that the Ca:Zr: In ratio in the co-precipitates is close to the theoretical value. The ratio of Ca:In decreases with increasing calcining or sintering temperature. ©     

Electrostatic immobilization of substrate and polyoxotungstate catalyst at the surface of micelles for enhanced reaction efficiency in water

Polyoxometalate (POM)-based micellar catalysts were prepared by assembling the Keggin tri-anion [PW₁₂O₄₀]^3 − and (L)-N-acetylmethioninate salts of Gemini surfactants in water. Contrary to conventional catalytic systems, we propose a new approach in which the POM catalyst and the substrate to be oxidized ((L)-N-acetylmethioninate) are both localized at the surface of micelles by electrostatic interaction before the reaction. The high local concentration of reactants due to their confinement at the surface of micelles enhances the reaction kinetics. Catalyst recovery experiments showed that, after two cycles of reactions, the activity of the catalysts  was not changed.     

Base-free copper-catalyzed aerobic oxidation of benzylic alcohols with N-benzylidene-N,N-dimethylthane-1,2-diamine and TEMPO

Selective oxidation of alcohols using N-benzylidene-N,N-dimethylthane-1,2-diamine, CuBr₂ and TEMPO as the catalytic system was developed. Catalyzed by this simple catalytic system in the absence of any external base, various benzylic alcohols could be oxidized to their corresponding aldehydes with excellent yields in CH₃CN/H₂O (v/v = 1/1) under 0.2 MPa O₂ at 80 °C.     

Effect of Si additions on the Al2O3 grain refinement upon oxidation of Cr2AlC MAX phase

The effect of Si additions on the oxidation behavior of Cr₂AlC based coatings is investigated. Oxidation experiment was performed at 1120 °C in air for 4 h for Cr₂AlC and Cr₂Al_1−xSi_xC (0 < x ≤ 0.06) coatings. The crystal structure, microstructure and chemical composition of the as-deposited as well as oxidized coatings have been investigated. Alloying Cr₂AlC with up to 0.7 at.% Si causes an increase in Al₂O₃ scale thickness by up to 40 ± 17%. Electron microscopy and atom probe tomography data support the notion that the here reported Si concentration induced 40% increase in Al₂O₃ layer thickness (during oxidation at 1120 °C for 4 h) is enabled by the Si concentration induced, and hence concomitant, increase in nucleation density of Al₂O₃.     

Solvent-free oxidation of alcohols catalyzed by an efficient and reusable heteropolyphosphatotungstate

With aqueous hydrogen peroxide as oxidant, secondary alcohols could be efficiently oxidized to ketones in the presence of hexadecyl trimethyl ammonium heteropolyphosphatotungstate ((n-C₁₆H₃₃N(CH₃)₃)₃[PW₄O₁₆]) under solvent-free conditions. The oxidation of alcohol over 0.5 mol% (based on molar amount of hydrogen peroxide) catalyst occurred at 90 °C to give the corresponding ketones with above 92% yield and 97% selectivity. The catalyst could be reused without loss of selectivity.     

Remarkable effect of Co and Mn on the activity of Fe3 − xMxO4 promoted oxidation of organic contaminants in aqueous medium with H2O2

In this work substituted magnetites Fe_3 − xMn_xO₄ (x=0.21, 0.26 and 0.53), Fe_3 − xCo_xO₄ (x=0;0.19;0.38;0.75) and Fe_3 − xNi_xO₄ (x=0;0.10;0.28;0.54) have been used to promote two different reactions involving H₂O₂: (i) the oxidation of organic molecules namely phenol, hydroquinone and methylene blue dye in aqueous medium and (ii) the peroxide decomposition to O₂. The presence of Co or Mn in the magnetite structure strongly increased the rate of H₂O₂ decomposition and the oxidation of the organic molecules whereas the presence of Ni inhibited both reactions. Kinetic data and CEMS Mössbauer spectroscopy suggest that the H₂O₂ decomposition and the organic oxidation are competitive reactions involving oxidizing species generated by surface M²⁺ (M=Fe, Co or Mn).     

Hydrolysis-induced aqueous gelcasting for near-net shape forming of ZTA ceramic composites

A new near-net shape forming process called “hydrolysis-induced aqueous gelcasting” (GCHAS) is reported in this paper for the consolidation of ZTA composites, ZTA-30 (70 wt.% Al₂O₃ + 30 wt.% ZrO₂) and ZTA-60 (40 wt.% Al₂O₃ + 60 wt.% ZrO₂). For comparison purposes, ceramics having the same chemical compositions were also consolidated by hydrolysis-assisted solidification (HAS). All the starting suspensions contained a solids loading of 50 vol.%. In the precursor powder mixtures, 1–5 wt.% of Al₂O₃ was replaced by equivalent amounts of AlN to enhance or promote or co-promote the consolidation of suspensions by HAS or by GCHAS, respectively. The suspensions for GCHAS were prepared by dispersing the ZTA powder precursor mixtures in a premix solution of 20 wt.% MAM (methacrylamide), MBAM (methylenebisacrylamide) and NVP (n-vinylpyrrolidinone) in 3:1:3 ratio in de-ionized water. Ceramics consolidated via GCHAS exhibited superior mechanical properties after consolidation and after sintering for 1 h at 1600 °C in comparison to those consolidated by HAS.     

Oxidation behavior characteristics of an aluminized Ni-based single crystal superalloy CM186LC between 900 °C and 1100 °C in air

Oxidation behavior of an aluminized Ni-based single crystal superalloy CM186LC was performed between 900 °C and 1100 °C in air. The oxidation kinetics approximately followed a parabolic oxidation law at 900 °C and 1100 °C. The mass gains were significantly increased owing to the formation of θ-Al₂O₃ during initial oxidation stage. After 100 h oxidation, the mass gain rates were then decreased due to the transformation from θ-Al₂O₃ to α-Al₂O₃. The microstructures after 500 h oxidation at all temperatures generally consisted of scale, coating layer, interdiffusion zone (IDZ), substrate diffusion zone (SDZ) accompanied with the topologically close-packed (TCP) and substrate.     

Effect of sintering additives on the oxidation behavior of Si3N4 ceramics at 1300 °C

This paper describes the results of systematic investigation of the oxidation behavior of Si₃N₄ based ceramics. The tests were carried out at 1300 °C for 2000 h in a high-temperature dry air environment. The Si₃N₄ specimens tested include the following: (a) S-1: Si₃N₄ added 8 mass% Y₂O₃, (b) S-2: Si₃N₄/SiC added 8 mass% Y₂O_3, (c) S-3: Si₃N₄ added 5 mass% Y₂O₃ and 3 mass% Al₂O_3, (d) S-4: Si₃N₄/SiC added 5 mass% Y₂O₃ and 3 mass% Al₂O_3. Several interesting conclusions were obtained as follows: (1) the thicknesses of oxidized layer of S-3 and S-4 were much thicker than S-1 and S-2, (2) oxidation kinetics of S-1 and S-2 obeyed a parabolic law on the whole, while those of S-3 and S-4 had a break, (3) the yttrium (Y) concentration under the oxidized layer decreased significantly. The Y-decreased zone was defined as a diffused layer. The thicknesses of the diffused layers of S-3 and S-4 samples were very large. (4) Primarily, the crystalline phases in the oxidized layer were SiO₂ and Y₂Si₂O_7. (5) The effect of SiC composition on the oxidation behavior was small.     

Oxidation reaction of high molecular weight dicarboxylic acids in sub- and supercritical water

Sebacic and azelaic acids, which are representative of high molecular weight dicarboxylic acids, were oxidized in a batch reactor with H₂O₂ oxidant in water from 300 °C to 400 °C at sub- and supercritical conditions. Intermediate products were identified based on GC–MS, HPLC, and ¹H NMR. The main oxidation products were dicarboxylic acids and the minor products were monocarboxylic acids. (ω − 1)-Keto acids, aldehyde-acids, and γ-lactones with carboxylic groups also were identified.On the basis of the products identified, the oxidation pathways of high molecular weight dicarboxylic acids were formulated. The oxidation of high molecular weight dicarboxylic acids proceed with the consecutive oxidation of higher to lower molecular weight dicarboxylic acids mainly through the oxidation at α-, β-, and γ-carbons to a –COOH group. The oxidation of dicarboxylic acids was also accompanied by oxidative decarboxylation, leading to the formation of monocarboxylic acids.     

Effect of La2O3 addition on long-term oxidation kinetics of ZrB2–SiC and HfB2–SiC ultra-high temperature ceramics

Long-term oxidation kinetics of SiC-reinforced UHTCs and La₂O₃-doped UHTCs over an intermediate temperature range (1400–1600 °C) reveal partially protective behavior for the former characterized by an oxidation kinetic exponent 1 < n < 2. In addition, unstable oxidation behavior was observed in HfB₂-based UHTCs due to the presence of SiC agglomerates. On the other hand, La₂O₃-doped UHTCs were found to be protective over the whole temperature range studied (n = 2), in particular at 1600 °C, where oxidation kinetic exponents as high as 8 were observed as a consequence of formation of new oxidation protective particles, MeO_xC_y, where Me is Zr, Hf or Si. Adsorption of oxygen-containing species formed protective MeO_xC_y phases, which enhanced the thermal stability of the oxide scale as well as providing protection against oxidation for long exposure times at 1600 °C.     

Antioxidative efficiency of novel β-naphthol derivatives in storage assays of cracked naphtha

The types of hydrocarbons found in gasoline have great influence on the formation of gum (nonvolatile, insoluble, adhesive resin that forms sediments within fuel systems of an engine). In this study, the synthetic compound β-naphthol has been used in order to generate novel antioxidative substances: AO1 [6-N-ethyl,N-ethylamino)β-naphthol], AO2 [6-N-ethyl,N-diethylamino)-β-naphthol] and AO3 [mixture of amino-β-naphthol and 1,6-di-amino-β-naphthol]. The derived compounds were subjected to accelerated oxidative stability assays [potential gum (PG) and induction period (IP)] and to storage assays [washed gum (WG) and ASTM color] during six months with cracked naphtha provided by the petroleum refinery RPBC (Presidente Bernardes Refinery, in Cubatão, Brazil). During the PG and IP assays, the experimental amine mixture AO3 and the commercial product known as PDE were highlighted as good oxidation inhibitors, yielding average values of 39.15 mg/100 ml and 637 min, respectively. After the storage period, a better antioxidant behavior was observed for the experimental compound AO2, which provided an average WG value of 6.1 mg/100 ml.     

The simple one-step solvothermal synthesis of nanostructurated VO2(B)

VO₂(B) has been successfully synthesized by simple, facile and environmental friendly one-step solvothermal method using V₂O₅ and ethanol as a starting agent. Obtained micrometer-sized powder was composed from mutually welded nanosized rod-like, flat and snowflake structures. VO₂(B) powder was tested for possible application as anode material for aqueous lithium ion batteries. Lithium intercalation/deintercalation reaction has been carried out by cyclic voltammetry in a saturated aqueous solution of LiNO₃. At scan rate of 10 mV s^?1 very stable cyclic performance of such obtained VO₂ was established with discharge capacity around 184 mAh g^?1.     

Synthesis of n-type Bi2Te1-xSex compounds through oxide reduction process and related thermoelectric properties

We propose a new process for the fabrication of n-type Bi₂Te_3-xSe_x (x = 0, 0.25, 0.4, 0.7) compounds. The compounds could be synthesized successfully using only oxide powders as the starting materials via the mechanical milling, oxidation, reduction, and spark plasma sintering processes. The controllability of the Se content could be ascertained by structural, electrical, and thermal characterizations, and the highest thermoelectric figure of merit (ZT) of 0.84 was achieved in Bi₂Te_2.6Se_0.4 compound at 423 K without any intentional doping. This process provides a new route to fabricate n-type Bi₂Te_3-xSe_x compounds with competitive ZTs using all oxide starting materials.     

Photooxidation of iodide ion on some semiconductor and non-semiconductor surfaces

In 80% aqueous ethanol, TiO₂ (anatase), ZrO₂, ZnO, V₂O₅, Fe₂O₃ and Al₂O₃ photocatalyze the oxidation of iodide ion but CdO and CdS do not; the wavelength of illumination is 365 nm. However, Fe₂O₃ fails to bring in a sustainable photocatalysis in 60% aqueous ethanol. The photooxidation of iodide ion on TiO₂, ZrO₂, ZnO, V₂O₅ and Al₂O₃ in 60% aqueous ethanol was studied as a function of [I⁻], amount of catalyst suspended, airflow rate, light intensity and solvent composition. The metal oxides examined show sustainable photocatalytic activity. Iodine formation is larger with illumination at 254 nm than at 365 nm. The mechanisms of photocatalysis on semiconductor and non-semiconductor surfaces have been discussed. Photocatalytic generation of iodine has been analyzed using a kinetic model. The photocatalytic efficiencies are of the order V₂O₅ > TiO₂ > ZrO₂ > ZnO > Al₂O₃ and V₂O₅ > TiO₂ > ZrO₂ > ZnO=Fe₂O₃ > Al₂O₃ in 60% and 80% aqueous ethanol.     

Improved dielectric properties and grain boundary response of SrTiO3 doped Y2/3Cu3Ti4O12 ceramics fabricated by Sol-gel process for high-energy-density storage applications

A chemical solution processing method based on sol-gel chemistry (SG) was used to synthesize (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) ceramics successfully. The 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics sintered at 1050 °C for 20 h showed fine-grained microstructure and high dielectric constant (ε′ ≈ 1.7 × 10⁵) at 1 kHz. Furthermore, the 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics appeared distinct pseudo-relaxor behavior. Two electrical responses were observed in the combined modulus and impedance plots, indicating the presence of Maxwell-Wagner relaxation. Sr vacancies and additional oxygen vacancies had substantial contribution to the sintering behavior, an increase in grain growth, and relaxation behaviors in grain boundaries. The contributions of semiconducting grains with the nanodomain and insulating grain boundaries (corresponding to high-frequency and low-frequency electrical response, respectively) played important roles in the dielectric properties of (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ ceramics. The occurrence of the polarization mechanism transition from the grain boundary response to the electrode one with temperature change was clearly evidenced in the low frequency range.     

One novel and unprecedented one-dimensional zinc coordination polymer with a N,O-donor chelating phenolic ligand, 3-n-butyl-2-(2-hydroxyphenyl)-3H-benzimidazole: synthesis,structure, characterization,photoluminescence and theoretical calculations

One novel and unprecedented 1D zinc coordination polymer with an unsymmetrical N,O-donor phenolic ligand, [Zn(bpbm)₂]_n (1) (Hbpbm · HCl · H₂O = 3-n-butyl-2-(2-hydroxyphenyl)-3H-benzimidazole hydrochloride hydrate) has been prepared and characterized crystallographically, and the geometric structure and photoluminescent properties, investigated experimentally and theoretically by DFT level. The deprotonated ligands, bpbm^?, as μ₂-bridging, adopt uncommon (O,N)-bridging poly(oligo)merization coordination mode, and not the common O-bridging poly(oligo)merization coordination mode. The photoluminescent property is assigned to π → π¹ ligand-to-ligand charge transfer transition (LLCT).     

Highly active Ni/MgO in oxidative steam pre-reforming of n-butane for fuel cell application

Oxidative steam reforming of n-butane over supported Ni catalysts at relatively low temperature, 723 K, is reported. Among all the supported 20 wt% Ni catalysts studied, only Ni/MgO was able to convert n-butane directly after O₂ oxidation. Additionally, when the Ni/MgO was prepared from an aqueous Ni(NO₃)₂ solution with pH 7, H₂ formation rate of Ni/MgO (pH 7) at a high SV (1660 l(h · g)⁻¹) was 2.3 times as high as that of conventional Ni/MgO. The higher activity of Ni/MgO (pH 7) was ascribed to stronger resistance against oxidation of Ni⁰ due to the formation of relatively large Ni⁰ particles.