Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure

Oxidized amorphous Si₃N₄ and SiO₂ powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si₂ON₂) was observed from amorphous silicon nitride (Si₃N₄) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si₂ON₂ coexisted with β-Si₃N₄ with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si₂ON₂. Pressing a mixture of amorphous Si₃N₄ of lower oxygen (1.5 wt%) and SiO₂ under 1.0–5.0 GPa between 1000° and 1350°C did not give Si₂ON₂ phase, but yielded a mixture of α,β-Si₃N₄, quartz, and coesite (a high-pressure form of SiO₂). The formation of Si₂ON₂ from oxidized amorphous Si₃N₄ seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure.     

Reaction of Zirconia with Silica at the Stoichiometry of Zircon

Zirconia was combined with silica and halide mineralizers and fired in a nitrogen atmosphere. X-ray analysis showed zircon was formed, demonstrating that an oxygen atmosphere is not necessary for the formation of zircon. The reaction mechanism is the same as that forming zircon in air, involving transport of the silica as a volatile halide, followed by diffusion of silica and oxygen across the product layer to a reaction site on the zirconia.     

Generation of Silica Nanoparticles from Tetraethylorthosilicate (TEOS) Vapor in a Diffusion Flame

Silica (SiO2) nanoparticles were synthesized by the gas phase thermal oxidation of tetraethylorthosilicate (TEOS) in a laminar diffusion flame reactor. Characteristics of the formation of silica nanoparticles along the axial distance above the burner outlet were investigated. Effects of maximum flame temperature, TEOS concentration, residence time, and water vapor on the particle size were also investigated. Silica nanoparticles less than 20 nm in average particle diameter were synthesized in all of the experiments. Morphological changes of particles were found along axial distance above the burner outlet; many small aggregates of particles (dp = ～ 7 nm) were found up to 2 cm, isolated smaller particles ( dp = ～ 5 nm) at 4 cm, and aggregates of bigger particles (dp = ～ 10 nm) at 10 cm. Larger particles at higher TEOS concentrations are generated in the flame synthesis. As the maximum flame temperature increased, the average particle size of silica also increased. Smaller particles were produced with decrease of the residence time of TEOS vapor in the flame. The average particle size decreased with the injection of water vapor to the flame.     

硫化钠法常压合成聚苯硫醚的研究

聚苯硫醚 (PPS)是一种新型的高分子工程塑料。概要介绍了PPS的特性及应用实例。在催化剂Na2 CO3 的作用下 ,用对二氯苯 (P -DCB)和脱水后的硫化钠在N -甲基吡咯烷酮 (NMP)溶剂中常压合成聚苯硫醚。实验中主要研究了温度、原料配比和反应时间对该缩聚反应的影响。实验结果表明 :反应最佳温度为 2 0 2± 3℃ ,最佳原料配比为 1∶1.1(Na2 S∶P -DCB) ,最佳反应时间为 8h。     

Surface -OH Profile from Reaction of a Heavy-Metal Fluoride Glass with Atmospheric Water

The surface -OH profile in a 15BaF₂-28.3ZnF₂-28.3YbF₂-28.3ThF₄ (mol%) glass resulting from reaction with atmospheric water for 22.5 h at 344°C was determined by monitoring the 2.9-pm absorption band as material was removed from the surface by polishing. The -OH penetrated -10 pm into the surface. The-OH concentration profile agreed with that predicted from a diffusional analysis, allowing determination of the surface -OH concentration; this corresponded to replacement of one of seven F⁻ ions with OH⁻.     

钾长石与氢氧化钠常压水热反应提钾工艺研究探讨

研究了常压下氢氧化钠分解钾长石工艺。结果表明:常压下氢氧化钠分解钾长石水热反应宜在沸腾状态下进行,待游离水分完全挥发后继续加热养护一定时间,然后产物加水浸取。比较理想的工艺条件为:m钾长石∶m氢氧化钠=1.0∶3.0,固液比为8∶1,养护温度220℃,养护时间15 min,浸取水量为25 mL/g。在理想工艺条件下,钾溶出率在85%以上。     

Possibilities of Colloidal Silica Separation from Water Suspension in the Polyethylene Glycol (PEG) Presence at Different Temperatures

The influence of polyethylene glycol (PEG) adsorption on the silica (SiO₂) suspension stability was examined in the range 15–35°C. For this purpose the following methods were applied: turbidimetry, spectrophotometry, and microelectrophoresis. They allow determination of silica suspension stability, its absorbance, and zeta potential of the solid particles in the absence and presence of the polymer. The obtained results indicate that both polymer adsorption and temperature influence the stabilization-flocculation properties of the systems under examination. The silica suspensions without the polymer are relatively stable in the whole range of the investigated temperatures (electroststic stabilization). The adsorption of polyethylene glycol with lower molecular weight (PEG 2000) practically does not change the stability properties of the suspension (steric stabilization), whereas the adsorption of PEG with the higher molecular weight (20000) causes its deterioration (bridging flocculation). The higher the temperature is the greater the effect of destabilization is obtained. Such behavior of the investigated system is the result of changes in the structure of the polymer adsorption layer with the increasing temperature.     

Detection of Military Explosives by Atmospheric Pressure Chemical Ionization Mass Spectrometry with Counter‐Flow Introduction

To detect vapors from explosives, we have developed a new detection system based on a novel ion source for atmospheric pressure chemical ionization (APCI). The direction of the sample gas flow introduced into the ion source is opposite to that of the ion flow produced by the ion source. We call this technique “counter‐flow introduction” (CFI). The CFI ion source has high ionization efficiency for nitro‐compounds and is installed in an ion‐trap mass spectrometer. Our tests on various military explosives show that this system is suitable for practical on‐line explosive detection; namely major explosives can be detected within a few seconds without any pretreatment of the sample gases.     

用气相色谱-质谱联用技术研究干气与苯反应机理

在利用气相色谱－质谱联用技术分析干气与苯反应产物的基础上,研究了在固态酸催化剂存在下,低相对分子质量烯烃与苯反应的机理。     

Water Vapor Permeability of Poly(L‐lactide)/Poly(D‐lactide) Stereocomplexes

PLLA/PDLA blend films with only stereocomplex crystallites as a crystalline species together with pure PLLA and PDLA films with only homo‐crystallites as a crystalline species were prepared, and the effects of enantiomeric polymer blending, crystalline species, and crystallinity on the water vapor permeability were investigated. The WVT coefficient P of PLLA/PDLA blend films was 14–23% lower than that of pure PLLA and PDLA films in the crystallinity X_c range of 0–30%. Amorphous PLLA/PDLA blend films have a much lower P than pure PLLA and PDLA films. The dependence of P on X_c for blend films was stronger for X_c = 0–30% than for X_c = 30–100%. This dependence is discussed using the Nielsen model and the concept of “restricted” (or “restrained”) and “free” amorphous regions.

     

Alkali Silica Reaction (ASR) as a root cause of distress in a concrete made from Alkali Carbonate Reaction (ACR) potentially susceptible aggregates

The mechanism of Alkali Carbonate Reaction (ACR) in concrete made from fine-grained, argillaceous dolomitic limestone coarse aggregates remains controversial. ACR distress is described as an increase in volume caused by the crystallization of brucite during the dedolomitization process. However, recent studies by Katayama suggest that ACR is a combination of the “deleteriously expansive Alkali Silica Reaction (ASR) of cryptocrystalline quartz in the matrix of the reactive aggregates and a harmless dedolomitization that produces brucite and a carbonate halo.” We investigated ACR susceptible concrete extracted from a wharf structure in Quebec, Canada, and determined that ASR was the cause of damage. Optical and SEM-EDS analyses identified ASR gel extending from reactive aggregates to the paste, and X-ray elemental mapping confirmed the gel composition. Silica (Si) was found in the matrix of the aggregate and is the source of reactive silica. These results support ASR as the mechanism in ACR susceptible concrete.     

Tissue Sampling and Homogenization in the Sub-Microliter Scale with a Nanosecond Infrared Laser (NIRL) for Mass Spectrometric Proteomics

It was recently shown that ultrashort pulse infrared (IR) lasers, operating at the wavelength of the OH vibration stretching band of water, are highly efficient for sampling and homogenizing biological tissue. In this study we utilized a tunable nanosecond infrared laser (NIRL) for tissue sampling and homogenization with subsequent liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis for mass spectrometric proteomics. For the first time, laser sampling was performed with murine spleen and colon tissue. An ablation volume of 1.1 × 1.1 × 0.4 mm³ (approximately 0.5 µL) was determined with optical coherence tomography (OCT). The results of bottom-up proteomics revealed proteins with significant abundance differences for both tissue types, which are in accordance with the corresponding data of the Human Protein Atlas. The results demonstrate that tissue sampling and homogenization of small tissue volumes less than 1 µL for subsequent mass spectrometric proteomics is feasible with a NIRL.     

C–S–H (I)—A Nanostructural Model for the Removal of Water from Hydrated Cement Paste?

Helium gas is used as a nanostructural probe to investigate the structural changes in C–S–H (I) due to the removal of interlayer water. Changes in the 002 basal spacing are correlated with helium inflow characteristics. Similarities to helium inflow experiments conducted on hydrated Portland cement and C₃S pastes are discussed. Conclusions are drawn with respect to the viability of considering C–S–H (I) as a physical model for the drying of Portland cement and C₃S pastes.     

聚乙二醇对混合嵌段聚氨酯透湿性能的影响

综合考虑聚酯型聚氨酯和聚醚型聚氨酯的特点,以聚己二酸丁二醇酯(PBAG)和聚乙二醇(PEG)混合作为软段,采用溶液预聚法制备了聚酯-聚醚混合型聚氨酯。考察了混合软段中PEG摩尔分数以及PEG相对分子质量对聚氨酯薄膜的表面接触角、吸水率、透湿率及力学性能的影响。结果表明,随着PEG摩尔分数的增大和PEG相对分子质量的增大,薄膜的接触角和拉伸强度降低,吸水率、透湿率增大。当PEG摩尔分数从0.28增加到0.71时,薄膜接触角从75.8°降低至63.5°,吸水率从25.7%增加到106.1%,透湿率从1226g/(m2·24h)增加到3408g/(m2·24h);PEG相对分子质量从1000增加到10000时,薄膜接触角从80.5°降到55.7°,吸水率从4.5%增加到356.4%,透湿率从733g/(m2·24h)增加到3577g/(m2.24h)。     

Vapor Pressures,Mass Spectra and Thermal Decomposition Processes of Bis(2,2‐Dintropropyl)acetal (BDNPA) and Bis(2,2‐Dinitropropyl)formal (BDNPF)

Simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and Fourier‐transform ion cyclotron resonance (FTICR) instruments have been used to measure the mass spectra, measure vapor pressures and evaluate the thermal decomposition mechanism of bis(2,2‐dinitropropyl)acetal (BDNPA) and bis(2,2‐dinitropropyl)formal (BDNPF). The high mass accuracy FTICR mass spectra provide the chemical formulas of the ion fragments formed in the mass spectra of BDNPA, BDNPF and their decomposition products, and provide a basis for predicting possible structures of the ion fragments. The heat of vaporization (Δ_vapH) and vapor pressure at 25 °C are 93.01±0.38 kJ/mol and 1.4532+0.40/−0.27 mPa for BDNPA, and 84.77±0.88 kJ/mol and 2.20+1.87/−1.07 mPa for BDNPF. STMBMS data support a nitro‐nitrite ( NO₂→ O NO) rearrangement mechanism for both compounds. Upon rearrangement, both NO and NO₂ are cleaved from the structure, thus producing a ketone radical. The nitro‐nitrite rearrangement begins to occur at appreciable rates between 160 and 180 °C. Additional decomposition products include amines, imines and amides, as well as CO₂ and H₂O at higher temperatures. STMBMS mass loss data suggest the formation of a residue during the decomposition of BDNPA and BDNPF. The major difference between the decomposition of the two compounds is the slower reaction rate of BDNPF. We postulate that the less sterically hindered formal carbon of BDNPF subjects it to interactions with an intermediate, thus forming a complex and delaying its release. Methods to elucidate complex thermal decomposition mechanisms from STMBMS data are illustrated.     

Solid‐State Polymerization of Poly(ethylene terephthalate): The Effect of Water Vapor in the Carrier Gas

SSP of PET has been thoroughly investigated under the regimes of chemical reaction and particle diffusion control. However, the majority of industrial PET plants operate under conditions of surface by‐product diffusion control, mainly due to recycling cycles of the carrier gas. The presence of residual volatile by‐products in the carrier gas (especially water) may affect adversely the polymerization reaction and the resulting polymer quality. For this reason, the effects caused by varying water vapor content of the carrier gas on the course of the PET SSP are analyzed, with emphasis on the intrinsic viscosity. The presence of small amounts of water in the carrier gas is found to exert a pronounced effect on the course of polymerization, leading to significant reduction of the molar masses of the final product.

     

Effect of Water Vapor on Oxidation Processes of the Cu(111) Surface and Sublayer

Copper-based catalysts have different catalytic properties depending on the oxidation states of Cu. We report operando observations of the Cu(111) oxidation processes using near-ambient pressure scanning tunneling microscopy (NAP-STM) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The Cu(111) surface was chemically inactive to water vapor, but only physisorption of water molecules was observed by NAP-STM. Under O₂ environments, dry oxidation started at the step edges and proceeded to the terraces as a Cu₂O phase. Humid oxidation of the H₂O/O₂ gas mixture was also promoted at the step edges to the terraces. After the Cu₂O covered the surface under humid conditions, hydroxides and adsorbed water layers formed. NAP-STM observations showed that Cu₂O was generated at lower steps in dry oxidation with independent terrace oxidations, whereas Cu₂O was generated at upper steps in humid oxidation. The difference in the oxidation mechanisms was caused by water molecules. When the surface was entirely oxidized, the diffusion of Cu and O atoms with a reconstruction of the Cu₂O structures induced additional subsurface oxidation. NAP-XPS measurements showed that the Cu₂O thickness in dry oxidation was greater than that in humid oxidation under all pressure conditions.     

常压下二乙二醇单乙醚和水二元体系不同温度下的密度、黏度及过量性质

Densities and viscosities were measured as a function of composition for binary liquid mixture of diethylene glycol monoethyl ether [CH3CH2O(CH2)2O(CH2)2OH] + water from 293.15 to 333.15 K at atmospheric pressure, with a capillary pycnometer and Ubbelohde capillary viscometer respectively. From the experimental data, the excess molar volume VE, viscosity deviation η, and the excess energy of activation for viscous flow G*E were calculated. These data were correlated by the Redlich-Kister type equa-tions to obtain the coefficients and standard deviations. The results showed a strong molecular interaction between diethylene glycol monoethyl ether and water.     

Single and Merged Beam Studies of the Reaction H2+ (v = 0,1; j = 0,4) + H2 → H3+ + H

Different approaches for studying low-energy (meV) reactive ion-molecule collisions in molecular beams are presented. In particular, differences in the photoionization (REsonant Multi-Photon Ionization / REMPI, Pulsed Field Ionization / PFI) experiments using single molecular beams vs. merged and crossed beams are discussed. We address the question of the proper determination of cross sections and rate constants in single beam experiments and the factors that influence the width of the collision energy distributions. We identify space charge effects as the dominant contribution under our experimental conditions. Problems pertinent to state-selected primary ion preparation with narrow energy distributions are highlighted. In light of the detailed data analysis, the derived relations are applied to the four-center reaction H₂⁺ + H₂ → H₃⁺ + H, which was studied in single and merged molecular beam experiments. We present merged beam data for the absolute reaction cross section for primary ions created in a storage ion source in the energy range from 5 meV up to 5 eV and relative state-selected cross sections for different vibrational and rotational ion states (v = 0,1; j = 0–4) generated by (3+1) REMPI for a mean collision energy of about 10 meV.