In situ Spinel Expansion Design by Colloidal Alumina Suspension Addition

The incorporation of nano powders into refractory castables it is not a straightforward procedure, due to their agglomeration and sintering drawbacks. Considering the alumina grain size effect on the in situ spinel formation and the associated overall volumetric expansion, alumina–magnesia refractory castables containing different alumina sources were evaluated by the assisted sintering technique. Reducing the size of fine tabular alumina (<200 μm) led to lower expansion levels, indicating the main role of alumina grain size in this property. Regarding the reactive aluminas (nano alumina powder, hydratable alumina, and colloidal alumina), the composition containing colloidal alumina performed remarkably better, leading to the lowest in situ spinel expansion level as a consequence of its high sinterability. The use of nano scaled alumina suspensions was the most suitable alternative to inhibit the shortcoming of nano powder agglomeration. Conversely, the castable containing the nano alumina powder did not behave as expected. The present work pointed out that the use of nano powders in refractory castables is only feasible if the compound is fully dispersed. Otherwise, cheaper raw materials could provide even better results than those of nano agglomerated powders.     

Characterization and Dehydration Behavior of a Natural,Ammonium Hydroxide,and Thermally Treated Zeolitic Tuff

Aqueous NH₄OH-treated and subsequently calcined forms of local natural zeolitic tuff were characterized by different techniques including scanning electron microscopy (SEM), X-ray powder diffraction, inductively coupled plasma–atomic emission spectroscopy (ICP-AES), volumetric N₂ adsorption at ?196°C, thermogravimetry (TG), differential scanning calorimetry (DSC), and transmittance infrared spectroscopy. The dehydration behavior of the samples was investigated using an in situ temperature-programmed diffuse reflectance Fourier transform infrared spectroscopy (TP-DRIFTS) method under vacuum. The DRIFTS spectra recorded yielded information about the effect of the NH₄OH treatment and subsequent calcination on the dehydration behavior of the natural zeolite. Changes in the infrared bands corresponding to vibrations of the O–H and N–H bonds upon in situ heating under vacuum were analyzed.     

Synthesis and Characterization of Amorphous Nano‐Alumina Powders with High Surface Area for Biodiesel Production

Nano‐alumina powders containing yttrium oxide were synthesized via the sol‐gel method using aluminum chloride hexahydrate as catalyst precursor. Fourier transform infrared analysis showed the presence of Al‐O and Al‐O‐Al bands in the powder structure and X‐ray diffraction spectra proved that the alumina was in the amorphous phase. The amorphous nano‐alumina powders were shown to be mesoporous with a high surface area, and both spherical and slit‐shaped particles were found in the calcined powder. A high percentage of conversion of oil to biodiesel was obtained in the transesterification reaction and the synthesized nano‐alumina powders could be easily regenerated for further use. The amorphous nano‐alumina powder can thus be recommended for use as active catalyst in the transesterification reaction for biodiesel production on the industrial scale.     

Prediction of oil yield from oil shale minerals using diffuse reflectance infrared Fourier transform spectroscopy

Multivariate analysis techniques, principal component analysis (PCA), principal component regression (PCR) and partial least square regression (PLSR), were employed to develop calibration and prediction models for the determination of oil yield from oil shale samples using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Data pre-processing included the use of second-derivative spectral data. Multi-component models were constructed and were effective in predicting oil yield with accurate predictions achieved using oil shale samples other than those used in the calibration set. DRIFTS with multivariate calibration modelling is demonstrated to provide a simple and rapid method of evaluating oil yield from oil shales compared with, and potentially replacing, the traditional modified Fisher assay (MFA) method.     

Stabilisation of low softening point petroleum pitch fibres by HNO3

This paper deals with the stabilisation of low softening point pitch fibres obtained from petroleum pitches using HNO₃ as oxidising agent. This method presents some advantages compared with conventional methods: pitches with low softening point (SP) can be used to prepare carbon fibres (CF), the stabilisation time has been reduced, the CF yields are similar to those obtained after general methods of stabilisation, and the initial treatments to increase SP when low SP pitches are used to prepare CF, are avoided. The parent pitches were characterised by different techniques such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), elemental analysis and solvent extraction with toluene and quinoline. The interaction between HNO₃ and the pitch fibres, as well as the changes occurring during the heat treatment, have been followed by DRIFTS.     

Complex mullite structures fabricated via digital light processing of a preceramic polysiloxane with active alumina fillers

By taking advantage of the multi-functional properties of preceramic polymers, their transformation into ceramic material at low sintering temperatures and the processing capabilities of polymer manufacturing processes, mullite components were fabricated by additive manufacturing. A photocurable silicone preceramic polymer resin containing alumina particles was shaped into complex structures via Digital Light Processing. Dense and crack-free, highly complex porous mullite ceramics were produced by firing a mixture of a commercially available photosensitive polysiloxane as the silica source, containing alumina powder as active filler, in air at a low sintering temperature (1300 °C). In particular, the developed formulations, coupled with the additive manufacturing approach, allow for precise control of the architecture of the porous ceramic components, providing better properties compared to parts with stochastic porosity.     

Direct decomposition of nitrous oxide over Ru/Al2O3 catalysts prepared by deposition–precipitation method

Alumina-supported ruthenium catalysts were prepared by the deposition–precipitation (DP) and impregnation (IMP) methods. The catalysts were characterized by BET surface area, X-ray diffraction, temperature-programmed reduction (TPR) and diffused reflectance infra-red spectroscopic (DRIFTS) techniques. The DP catalysts showed higher activity than their IMP analogues. The DRIFTS analysis revealed preferential formation of Ruⁿ⁺ species on the surface of DP catalysts. Both Ruⁿ⁺ and Ru⁰ species appeared on IMP catalysts, with the composition of Ru⁰ increasing with increase in metal loading. The temperatures at which the peak maxima appeared were higher in the TPR patterns of the DP catalysts, indicating greater interaction between Ru and alumina, which explained the formation of the cationic Ru species. The high activity of the catalysts prepared by DP method was related to the formation of electron deficient Ru sites during the preparation of the catalyst.     

High-temperature stabilization of polypropylene using hindered phenol–thioester stabilizer combinations,Part 1: Optimization and efficacy via nondust blends

The thermal degradation of unstabilized polypropylene has been investigated under long-term processing (twin extruder) and thermal aging at 150°C, with additive concentration studies on combinations of an established hindered phenolic antioxidant (pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) [S1010] and two popular thioesters (distearyl-3,3′-thiodipropionate [DSTDP] and didodecyl-3,3′-thiodipropionate [DLTDP]) using melt flow rate, carbonyl index and powder diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) (FTIR), and differential scanning calorimetry (DSC) (oxidation induction time [OIT]) and ultimate embrittlement time (Fracture) on injection-molded test pieces. It was found that 20:80 phenol:thioester ratios provided the best long-term thermal stability (LTTS); however, this was the reverse for processing stabilization (80:20), underlining the antioxidant nature of the two stabilizers (long term vs. melt). Melt preblending of the stabilizers (to form a no-dust blend) gave rise to improved LTTS. DRIFTS FTIR indicated that there was an improvement in preblending the additives, which removed any volatile impurities. Increased additive dispersion and localized potential efficacy in the stabilization cycle is important, as well as possible improved addition of the additives to the extruder rather than fine powder. The data are discussed in relation to the long-term stabilization of polypropylene in high-temperature applications such as under the bonnet of automobiles where minimizing stabilizer losses and maximizing synergy are important.     

钛柱撑黏土的核磁共振和漫反射红外光谱

Pillared clays（Ti-PILCs）were synthesized from Na-type montmorillonite through intercalation with polymeric hydroxy-titanium.The mechanism of the pillaring course was studied by means of magic angle spinning nuclear magnetic resonance（MAS NMR）and diffuse reflectance infrared spectroscopy（DRIFTS）techniques.DRIFTS suggested that after Ti-pillaring,the silicon-oxygen tetrahedral Si—O—Si bond and aluminum oxide octahedral Si—O—Al bond were broken.Meanwhile,NMR also showed the change of the silicon-oxygen tetrahedral structure and aluminum oxide octahedral structure in the pillared clay.In the pillaring process,the titanium hydroxy-oligomeric cations entered the layers of the montmorillonite by ion-exchange,the Si—O—Al bond of the raw clays were broken,the silicon-oxygen tetrahedron structure were overturned,and the reactive oxygen species（structural hydroxyl）reacted with titanium hydroxy-oligomeric cations to form Si—O—M bond.This led to the incorporation of pillaring species of Ti in the layers of the clay.After further heat treatment,the TiO₂ pillars were formed in the layers to obtain Ti-PILCs.     

聚丙烯酸盐的助洗性能研究

研究了聚丙烯酸盐（PAA）及其改性聚合物（马来酸酐-丙烯酸甲酯-丙烯酸的三元共聚物）的组成，结构及相对分子质量对钙束缚力，分散力，絮凝性的影响。以两种商品PAA为参照，通过正交实验筛选出了无磷洗衣粉的最佳配方。实验结果表明，Ca^2 束缚值随着聚合物相对分子质量的增加而增大，其聚物中单体组成对Ca^2 束缚值影响不大。以聚合物与CaCl2的螯合物的沉淀量表征及其絮凝剂，发现聚合物加入量和Ca^2 总量相同时，沉淀量随着聚合物相对分子质量的增大而增大，饱和沉淀量只与CaV有关而与聚合物类型无关，达到饱和沉淀量时所应对应的聚合物加入量也近似正比与相应聚合物的CaV，实验条件下PAA对碳黑的分散力均优于STPP，均聚PAA对碳黑的分散力随相对分子质量增大而下降，改性PAA且增相对分子质量的增大而分散力仅略有下降，改性聚合物的相对分子质量对洗涤性能具有更广泛的适用性。     

Surface Chemistry of Lead Titanate and Its Impact on Binder Removal

Carbon residue after binder burnout was characterized for several nonstoichiometric lead titanate powders. Thermal decomposition of the poly(methyl methacrylate) (PMMA) binder was performed in nitrogen at 600°C. A drastic decrease in carbon retention was obtained in the case of the titanium-rich samples. The amount of carbon retention varies from 0.2 mg/m² to 1.2 mg/m² by changing the Pb/Ti molar ratio from 0.92 to 1.08. The surface reaction between PMMA and lead titanate particles was studied by diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). Surface hydroxyls reacted with ester groups in the PMMA or the methylmethacrylate monomer produced upon pyrolysis. The DRIFTS results showed that titaniumrich samples are less reactive and produce less surfacebound organic groups. Interestingly, titanium-rich samples contained more surface hydroxyls. Isoelectric point measurements, however, show that titanium-rich samples are more acidic. Thus, the reactivity of the surface hydroxyls is determined primarily by their acid-base characteristics rather than their concentration. Lead titanate powder was exposed to MMA vapor in a tube furnace at the indicated temperatures using nitrogen carrier gas as a model experiment. DRIFTS difference spectroscopy and Raman spectroscopy were performed on these samples after the exposure. MMA reacts with lead titanate powder in manner similar to PMMA. Analysis for sp ² and sp ³ absorbance of Raman spectra of these exposed powders at 400°–600°C showed pyrolysis behavior of surface-reacted species. The relative amount of sp ² bonded carbon decreases with increasing exposure temperature.     

Analysis of Among-Species Variability in Wood Fiber Surface Using DRIFTS and XPS: Effects on Esterification Efficiency

Abstract

Variability in the chemical composition of surface properties of various wood fibers (eastern white cedar, jack pine, black spruce, and bark) was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray photoelectron spectroscopy (XPS). Both DRIFTS and XPS showed high variability in fiber surface composition between species and between fiber types (sapwood, heartwood, and bark). Fiber surface was modified by esterification reaction using a maleic anhydride polyethylene (MAPE) treatment. DRIFTS failed to assess surface modification, whereas XPS results showed that MAPE treatment increased the surface hydrocarbon concentration of jack pine wood fiber, indicated by a decrease in oxygen–carbon ratio and an increase in relative intensity of the C1 component in the C1s signal. Lignin concentration variability on the fiber surface was determined as the major factor that prevents esterification from taking place.     

On the reactivity of diamond surface with NO2

The reactivity of a synthetic diamond powder with NO₂ was investigated at 313 and 373 K using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and an environmental cell. The reaction is non-catalytic and produces adsorbed RNOx and ROx species on the surface and NO in the gas-phase by dissociative chemisorption. Infrared studies of the adsorbed products have allowed us to identify the presence of nitroalkyl, alkylnitrite, alkylnitrate, carboxyles and anhydrides as the major surface species. The influence of the reaction temperature in terms of kinetics and nature of adsorbed intermediates is also discussed, just as the thermal stability of the adsorbed products.     

洗衣液去污力测试应优化

洗涤剂类别不同,其配方也不同,从洗衣粉的配方成分入手,针对不同成分对去污力的贡献,得出了洗衣粉参比洗涤剂不应作为液体洗涤剂的参比洗涤剂,并由此提出了参比洗衣液的配方建议。     

Optical characterization of stereolithography alumina suspensions using the Kubelka–Munk model

The multiple light scattering in concentrated alumina suspensions adapted to stereolithography can be modeled using diffuse reflectance measurements coupled to the Kubelka–Munk model. The penetration depth of UV radiation can be related to the scattering coefficient allowing the prediction of the cure depth with an accuracy of 20%.     

Synthesis of nanocrystalline ZnO–NiO mixed metal oxide powder by homogeneous precipitation method

Nanocrystalline ZnO–NiO mixed metal oxide powder has been successfully prepared via a simple homogeneous precipitation method in short time. The nanocrystalline sample was obtained at low calcination temperature (350 °C). Specific surface area, crystallite size and optical band gap of the samples depend on calcination temperature. The synthesized samples were characterized by means of powder X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, surface area measurements, scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy and magnetic measurements. The synthesized powder samples have been tested for their catalytic reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride.     

The prediction of clay contents in oil shale using DRIFTS and TGA data facilitated by multivariate calibration

The prediction of clay content in oil shale is important for the optimisation of oil shale processing conditions and process feasibility. The multivariate calibration technique of partial least squares regression (PLSR) was implemented in order to predict clay content in oil shale samples taken from the Stuart oil shale deposit, Queensland, Australia. The calibration data used were the diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) spectra of 34 oil shale samples. DRIFTS data from another set of 20 oil shale samples were used for model validation. The data pre-processing includes the use of derivatives facilitated by the Savitsky-Golay nine-points’ method. A four components model was constructed and it showed a root mean square error of calibration (RMSEC) of 4.79% and a root mean square error of prediction (RMSEP) of 4.35%. TGA data sets were also used to construct a calibration model, which produced less accurate results than DRIFTS. DRIFTS, when combined with multivariate calibration, provided an accurate in situ method of evaluating clay content in oil shale. Clay content measured using XRD was used as a reference.     

Pentacoordinate Silicon Complexes as Precursors to Silicate Glasses and Ceramics

The recent discovery that pentacoordinate alkali glycolato silicates such as monomeric MSi(OCH₂CH₂O)₂OCH₂-CH₂OH or dimeric M₂Si₂(OCH₂CH₂O)s (where M = Li, Na, K, or Cs) can be synthesized directly from SiO₂, ethylene glycol, and MOH suggests that these compounds may serve as useful, inexpensive precursors to alkali silicate glasses or ceramics, either by sol–gel processing or by simple pyrolysis. We report here studies on the chemical changes and phase transformations that occur during the pyrolytic transformation of these compounds to ceramic and glassy materials. The evolutionary processes encountered as the materials are heated to selected temperatures were followed by X-ray powder diffraction, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermal analysis techniques. In general, the crystalline compounds oxidatively decompose at temperatures above 300°C to form amorphous materials. At higher temperatures, the line compounds M₂Si₂O₅ begin to crystallize. During the transformation process, ligand oxidation forms CO₂ and H₂O, which react with the alkali metals to form small amounts of carbonates as seen by DRIFTS. At higher temperatures, the carbonates decompose with coincident formation of the primary crystalline phase, except in the case of the potassium compound, which exhibits some phase segregation.     

Characterization of Poly(Aminosiloxane) Surface Chemistry on Aluminum Oxide

N-2-aminoethyl-3-aminopropyltrimethoxysilane (AAPS) was shown to react with aluminum oxide powder to form an amine/carbonate salt, as observed by diffuse reflectance infrared spectroscopy (DRIFT) and thermogravimetric analysis with mass spectroscopy (TGA-MS). TGA-MS, together with electron spectroscopy for chemical analysis (ESCA), reveal that the stoichiometric ratio of amine salt to free amine is higher on the surface of aluminum oxide powder than in a comparable neat film. In addition, TGA-MS shows that a nonstoichiometric ratio of CO₂H₂O is evolved upon heating the surface-treated powder (4.5/1), whereas the neat film evolves CO₂/H₂O at a ratio near unity. The high fraction of protonated amines, together with the higher ratio of CO₂/H₂O in the presence of alumina, is consistent with a proposed bonding mechanism which involves carbonate bridging between protonated amines and hydroxyl sites on the aluminum oxide surface.     

FTIR Spectra of faceted diamonds and diamond simulants

FTIR spectra of faceted diamonds and diamond simulants collected by diffuse reflectance, transflectance, and specular reflection techniques were compared. The transflectance technique exploited total internal reflection phenomenon within the faceted diamond for the spectral acquisition. The transflectance spectra were similar to the well-accepted diffuse reflectance spectra with equal or better spectral qualities. Based on the observed spectral features of the faceted diamond, classification of the diamond, determination of defects, impurities, and treatment process (i.e., irradiation and high pressure and high temperature) can be performed.