A high temperature and high sensitivity micro-thermobalance

A thermobalance which ensures a sensivity of 1 × 10^?6 g and an excellent stability up to 1500 C has been developed. A sample, which is suspended from one end of the beam of the balance, is heated in a compact furnace with a small heat capacity. Temperature is measured by a Pt-PtRh (10%) thermocouple placed close to the sample. Use of an alumina mantle ensures easy control of atmosphere: at room temperature, the evacuation can be done to 1 × 10^?4 Torr, and stable operation can be done up to 1500 C in air inert gas at a flow-rate smaller than 50 ml min^?1. It is also possible to use a corrosive gas as atmosphere. In a blank test with platinum cell support (6.5 mm diam. and 0.1 mm thick) suspended in an air stream of 50 ml min^?1 and heated up to 1500 C at 10 C min^?1, the drift was smaller than 20 × 10^?6 g and the reproducibility was better than 10×10^?6 g. This paper refers to the construction of the thermobalance, and its performances. And some examples of high temperature thermogravimetry through the results of analyses of CaCO₃, quick lime and byproduct lime are also reported.     

Ring-substituted polyaniline copolymers combining high solubility with high conductivity

Poly(aniline-co-phenetidine)s were synthesized by the copolymerization of aniline and o-phenetidine (o-ethoxyaniline). The molar feed ratio of the starting aniline monomers was varied to result in copolymers with different compositions. The actual composition was deduced by integrated proton NMR spectroscopy. The copolymers exhibit excellent solubility characteristics. It was particularly interesting to find that the 20% ethoxyaniline containing copolymer exhibits excellent solubility and yet retains the high conductivity characteristic of the unsubstituted homopolymer. The conductivity of the hydrochloride salt of this par-ticular copolymer is identical to that of the unsubstituted derivative. However, the copolymer solubility greatly exceeds that of the unsubstituted homopolymer. The copolymer in the base form exhibits very high solubility in NMP and the resulting solutions are exceedingly more stable than those of the unsubstituted derivative. A 10% by weight solution of the 20% ethoxy copolymer in NMP is stable for ? 50 days at room temperature afterwhich a gel is formed as compared to previous reports of ? 3–10 h stability for corresponding solutions of the unsubstituted derivative. © 1995 John Wiley & Sons, Inc.     

高湿度条件下分解高浓度O3催化剂的研究

Ｏ3 (臭氧 )具有极强的氧化能力 ,因此被广泛地用于水和空气的除臭、杀菌以及染料废水的脱色、ＣＯＤ的去除及芳香族有机物的降解[1,2 ] 。但Ｏ3 是一种毒性物质 ,处理过程中剩余的Ｏ3 排放到空气中会造成环境污染。目前 ,处理含Ｏ3 尾气的方法主要有活性炭吸附法、药液吸收法、高温热解法和催化分解法[1] ,其中催化分解法不仅有高的分解率 ,而且满足长期稳定、安全、经济等要求 ,是较为理想的Ｏ3 分解方法。催化分解法使用的催化剂主要有含Ｍｎ催化剂、含Ｔｉ催化剂和过渡金属催化剂等。各种催化剂在低湿度条件下的催化性能都比较好 ,但在…     

Advances in zebrafish high content and high throughput technologies

The zebrafish has emerged as an excellent transitional screening model system between cell-based assays, which are rapid and inexpensive but have limited physiological relevance, and higher vertebrate models, which have better physiological relevance, but are more time-consuming and expensive to deploy. As vertebrates, zebrafish maintain significant evolutionary proximity to humans and have been validated as robust models for drug research, studies of mechanism and behavioral genetics. Unlike higher vertebrate models, zebrafish are well-suited to high-throughput applications owing to their high fecundity, rapid extrauterine development and transparency during organogenesis enabling in vivo labeling and imaging. Recent advances have been made in automating high content and high-throughput zebrafish screens, with the goal of developing fully automated drug screening platforms. The application and continued development of these technologies holds potential clinical significance in drug discovery and elucidating disease mechanisms.     

Tensile deformation of high strength and high modulus polyethylene fibers

The influence of tensile deformation on gel-spun and hor-drawn ultra-high molecular weight polyethylene fibers has been investigated. In high modulus polyethylene fibers no deformation energy is used to break chemical bonds during deformation, and flow is predominantly present next to elastic behavior. Flow is reversible after tensile deformation to small strains, but becomes irreversible when yielding occurs.Stress relaxation experiments were used to determine the elastic and flow contribution to tensile deformation. A simple quantitative relation could then be derived for the stress-strain curve that directly links yield stress to modulus. Experimental stress-strain curves could be reasonably described by this relation.Flow during tensile deformation is shown to be correlated with the introduction of the hexagonal phase in crystalline domains. A mechanism of flow is proposed in which, at first, tie molecules or intercrystalline bridges are pulled out of crystalline blocks (reversible), followed by the break-up of crystalline blocks through slip of microfibrils past each other (stress-induced melting, irreversible).     

Quality of high count rate high resolution short-time activation analysis

The fast transfer system was modified to enable a fixed counting geometry with high reproductibility using an endcap geometry. The optimal count rate for short time activation analysis by means of the loss free counting system was found to be within 100–140 kcts/s, if a high accuracy is needed (1%). The method of calculating the peak area after the dead time and pile up corrections was modified by changing the peak fitting parameters gradually with increasing count rates. Epithermal activation by a⁶LiD converter was found to be an ideal irradiation technique for short time activation analysis especially for heavy elements due to the lower contribution of²⁴Na and²⁸Al (up to 30 fold).     

Synthesis of high purity single-walled carbon nanotubes in high yield

A simple method for the synthesis of high purity single wall carbon nanotubes has been developed by using nickel formate as a precursor for the formation of nearly mono-dispersed nickel seed-nanoparticles as catalysts in the CVD growth process.     

Synthesis and properties of high strength high modulus ABA block copolymers

A series of novel ABA block copolymers were synthesized containing a rigid-rod (B) block for reinforcement and a flexible coil (A) block as the matrix. Poly[(benzo[1, 2d: 4, 5d′]bisthiazole-2,6-diyl)-1,4-phenylene] (PBT) was the rigid-rod (B) block utilized in this study and was polymerized in such a way as to provide carboxylic acid end-groups. The carboxy-terminated PBT was copolymerized with the AB monomers, 3,4-diaminobenzoic acid and 4-amino-3-mercaptobenzoic acid, which generates a benzimidazole or benzthiazole (A) block, as well as grafts the blocks together. Composition of the blocks could be varied by the weight of AB monomer used in the copolymerizations. Solution behavior of the copolymers in methanesulfonic acid was determined, and fibers were obtained by wet spinning techniques. The block copolymers exhibited typical tenacities of 200 ksi, 16 Msi modulus, and an elongation to break of 1.4%. Critical concentration values for fabrication increased approximately 3% over mechanical mixtures of the same heterocyclic components.     

Dendrimer-activated surfaces for high density and high activity protein chip applications

Highly functional Si and glass surfaces for protein immobilization have been prepared by a facile activation of native surface silanol groups. Poly(propyleneimine) dendrimers of generations 1-5 were immobilized onto the surface using a facile room-temperature coupling procedure that involved activation of native silanol groups of glass using 1,1'-carbonyldiimidazole under anhydrous conditions. The dendrimer-coated surfaces were used to immobilize proteins and were characterized with respect to surface loading and activity. A number of different chemical, physical, and biochemical techniques including contact angle measurement, ellipsometry, and fluorescence microscopy were used to characterize the resulting surfaces. Increasing the dendrimer generation past G-3 led to increased surface amine content, immobilized protein concentration, and the activity of immobilized alkaline phosphatase (used as a test system). Very high activity of the immobilized proteins in the case of higher generation (G-4 and G-5) dendrimers led us to conclude that such an approach has true potential for creating highly functional surfaces for protein chip applications.     

Proton and carbon-13 high resolution NMR spectroscopy of high polymers

Using a super-conducting magnet, the examination of high polymers by ¹H- and ¹³C-NMR provides complementary and precise information about their microstructures. The configuration of the polymer skeleton and chemical structures which are present in low concentrations are easily observed. Relationships between polymerization mechanisms, microstructure and properties thus become clearer.     

Sulfur-containing silsesquioxane hybrids with high refractive index and high Abbe number

Novel sulfur-containing silsesquioxane nanoparticles, (R_S–SiO_1.5) _n , having uniform size distribution, good solubility, and relatively high refractive index were synthesized by hydrolytic condensation of a triethoxysilane precursor derived from glycidol, followed by the esterification with sulfur-containing acid chlorides. Esterification of the water-soluble silsesquioxane nanoparticles with 3-(methylthio)propionyl chloride afforded silsesquioxane hybrid with a high density of chemically bonded peripheral methyl thioether groups, which was characterized by ¹H, ¹³C NMR, Fourier transform infrared spectroscopy, and thermogravimetric analysis measurements. The resulting product was soluble in various organic solvents, such as CHCl₃, acetone, tetrahydrofuran, dimethyl formamide, and dimethyl sulfoxide. The size of the sulfur-containing nanoparticles evaluated by X-ray diffraction was 2.1 nm. Transmission electron microscopy, gel permeation chromatography, and dynamic light scattering measurements indicated the formation of the nanoparticles having relatively narrow size distribution with an average particle diameter of less than 3 nm without aggregation. The sulfur content of the methyl thioether-containing silsesquioxane hybrid analyzed by elemental analysis was 16.1 %, which led to relatively high refractive index (n _D?=?1.588) and high Abbe number (34.4). Two sulfur-containing silsesquioxane hybrids with peripheral thiophene and phenyl thioether moieties were also obtained by the same procedure, and resulting hybrids showed high refractive indices of 1.605 and 1.627, and Abbe numbers of 31.8 and 24.3, respectively.     

Melting and dissociation of ammonia at high pressure and high temperature

Raman spectroscopy and synchrotron x-ray diffraction measurements of ammonia (NH(3)) in laser-heated diamond anvil cells, at pressures up to 60 GPa and temperatures up to 2500 K, reveal that the melting line exhibits a maximum near 37 GPa and intermolecular proton fluctuations substantially increase in the fluid with pressure. We find that NH(3) is chemically unstable at high pressures, partially dissociating into N(2) and H(2). Ab initio calculations performed in this work show that this process is thermodynamically driven. The chemical reactivity dramatically increases at high temperature (in the fluid phase at T > 1700 K) almost independent of pressure. Quenched from these high temperature conditions, NH(3) exhibits structural differences from known solid phases. We argue that chemical reactivity of NH(3) competes with the theoretically predicted dynamic dissociation and ionization.     

Neutron activation analysis of high purity silver using high resolution gamma-spectrometry

A method of neutron activation determination of microimpurities in high purity silver has been developed. For matrix activity separation the extraction of silver by dibuthylsulfide (DBS) was employed. The purification coefficient was 10⁸ after triple extraction. Using Ge(Li) detector it was possible to determine 30 elements simultaneously in silver samples.     

Phosphonium‐based polyelectrolyte networks with high thermal stability,high alkaline stability,and high surface areas

Phosphonium‐containing polyelectrolyte networks (PENs) ( P1 – P4 ) were prepared by cyclotrimerization of bis(4‐acetylphenyl)diphenylphosphonium bromide ( M1 ) and 1,4‐diacetylbenzene ( M2 ) with p‐toluene sulfonic acid in various M1:M2 ratios (1,0, 1:1, 1:2, and 1:4). The relative abundance of the PAr₄⁺ units in each PEN was demonstrated to influence thermal stability, alkaline stability, water uptake, surface area, and CO₂ uptake in predictable ways. Impressively, PENs with NTf₂^? counterions (Tf = CF₃SO₃) did not exhibit 5% mass loss until heating above 400 °C. Alkaline stability, tested by challenging a PEN with 6 M NaOH(aq) at 65 °C for 120 h, increased with increasing PAr₄⁺ content, which reflected the enhanced reactivity of the HO^? anion in more hydrophobic materials (i.e., PENs with lower M1:M2 ratios). The specific surface areas estimated by Brunauer‐Emmett‐Teller (BET) analysis for these PENs were above 60 m²/g under N₂ and nearly 90 m²/g under CO₂. Notably, P3 (in which 33% of monomers comprise a phosphonium moiety) exhibited a CO₂ uptake affinity of one CO₂ molecule adsorbed for every phosphonium site. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 598–604     

Wettability switching between high hydrophilicity at low pH and high hydrophobicity at high pH on surface based on pH-responsive polymer

Surfaces obtained by modifying poly(N,N'-dimethylaminoethyl methacrylate) (PDMAEMA) on rough silicon substrates are highly hydrophilic at low pH and highly hydrophobic at high pH; such surfaces effectively supplement the research on the wettability of solid surfaces based on the pH-responsive polymers.     

Viscosity of aqueous calcium chloride solutions at high temperatures and high pressures

Viscosity of six (0.10, 0.33, 0.65, 0.97, 1.40, and 2.00) mol kg⁻¹ binary aqueous CaCl₂ solutions has been measured with a capillary-flow technique. Measurements were made at pressures up to 60 MPa. The range of temperature was from 293 to 575 K. The total uncertainty of viscosity, pressure, temperature, and composition measurements was estimated to be less than 1.6%, 0.05%, 15 mK, and 0.014%, respectively. The effect of temperature, pressure, and concentration on viscosity of binary aqueous CaCl₂ solutions was studied. The measured values of viscosity of CaCl₂(aq) were compared with data, predictions, and correlations reported in the literature. The temperature and pressure coefficients of viscosity of CaCl₂(aq) were studied as a function of concentration and temperature. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for the relative viscosity (η/η₀) to accurate calculate the values of viscosity A- and B-coefficients as a function of temperature. The derived values of the viscosity B-coefficients were compared with the values calculated from the ionic B-coefficient data. The physical meaning parameters V and E in the absolute rate theory of viscosity and hydrodynamic molar volume (effective rigid molar volume of salt) V_k were calculated using present experimental viscosity data. TTG model has been used to compare predicted values of the viscosity of CaCl₂(aq) solutions with experimental values at high pressures.     

Novel instrument for high temperature thermogravimetric measurements in high water vapour contents

Summary A novel instrument for high temperature thermogravimetric measurements in atmospheres containing high water vapour contents was developed in a collaboration between Netzsch and Risø National Laboratory. The development of the instrument was initiated to facilitate the investigation of high temperature corrosion of steels in humidified atmospheres. The instrument consists of a standard thermal analyser unit, including a new water vapour furnace, balance and sample carrier. The design of the instrument is discussed and thermogravimetric measurements on a Fe₇₈Cr₂₂ steel are presented.     

Stabilization at high temperatures

A general detailed model of polymer oxidative degradation in the presence of a stabilizer-oxygen acceptor was considered. The motion of the degradation zone boundary and the sample lifetime were obtained for various conditions of the process. In particular, it is shown that within the given concentration immobile oxygen acceptor has the best stabilizing properties. The theoretical results are compared with the experimental data obtained by using two independent methods: polymer sample cracking and a change in the ESR signal. Good agreement between theory and experiment was obtained.     

Phthalonitrile-based high temperature resin

An aromatic, diether-linked phthalonitrile resin, prepared from 4,4′-bis(3,4-dicyanophenoxy)biphenyl, exhibits excellent thermo-oxidative properties. The resin is easily processed from the melt of the monomer in a controlled manner as a function of the amine curing agent and processing temperatures. Polymerization occurs by a cyclic addition reaction without the formation of volatile by-products. The polymerization reaction can be stopped at a prepolymer stage. The prepolymer can be stored indefinitely at ambient conditions without further reaction. The modulus and viscoelastic properties of the resin were found to be a function of the postcuring conditions.     

Synthesis of high molecular weight polystyrene using AGET ATRP under high pressure

High molecular weight polystyrene (PS) was synthesized by ATRP. Under atmospheric pressure (1 bar), PS with M_n up to 200,000 was prepared using either ARGET or ICAR ATRP. Under high pressure (6 kbar), higher molecular weight PS could be obtained due to accelerated radical propagation and diminished radical termination in polymerization of styrene. Therefore, it was possible to synthesize PS with M_n > 1,000,000 and M_w/M_n < 1.25 using AGET ATRP under a pressure of 6 kbar at room temperature. This is the highest molecular weight linear PS prepared by a controlled radical polymerization.