Polygonal Single-Crystal Aluminum Borate Microtubes

In this paper we report the synthesis of polygonal single-crystal aluminum borate microtubes by the direct calcination of alumina and boron nitride powders in air. The diameters of the obtained tubes vary between 1 and 15 μm; and the lengths are in the range of tens to hundreds of micrometers. The cross-sections of the microtubes are in the shapes of rectangular, hexagonal, and quasi-circle. A new solid–liquid–solid growth mechanism was proposed to account for the formation of microtubes instead of whiskers.     

Formation of spheres and siliceous plugs in synthesizing MCF materials

The unique pore structure combined with its high pore volume and large pore size make MCF material attractive as a catalyst support related to reactions with large molecules or as a capsule for storing and controlled release of organic guest substances. By varying the amount of TEOS, or the stirring temperature or the aging conditions in the synthesis, spheres are formed among the products. Siliceous plugs inside the MCF structures can also be produced in case of aging the synthesis mixtures at relatively low temperatures in flasks in oil baths instead of using the autoclave procedure. If the aging temperature is relatively high (such as 80°C), normal MCF material is also obtainable with this simplified procedure. These observations provide a further possibility to tune the morphology and the textural properties of the MCF materials.     

A Composite Material in the Al – B – C System

Results of a study of a material prepared by impregnating boron carbide with aluminum are reported. A shortcoming of this composite material is that it tends to degrade (at a different rate depending on the conditions) into a powder. Introduction of boron and magnesium diboride enhances the material stability; however, specimens high in aluminum carbide are the most prone to degradation. It is assumed that the process of degradation involves hydrolysis of residual (free) aluminum in the presence of aluminum carbide.     

微波消解-电感耦合等离子体原子发射光谱法测定酚醛树脂合成材料中铝钙硼镁锌

提出了微波消解电感耦合等离子体原子发射光谱法测定酚醛树脂合成材料中铝、钙、硼、镁、锌的分析方法。在密闭容器中,用硝酸和氢氟酸混酸做溶剂在微波状态下消解酚醛树脂合成材料样品,样品溶解完毕泄压后,定容,用电感耦合等离子体原子发射光谱仪测定铝、钙、硼、镁、锌的含量。同时考察了微波消解称样量、溶剂用量及共存离子对分析结果的影响,其样品的测定结果与化学法测定值一致。本法适应于酚醛树脂合成材料中铝、钙、硼、镁、锌的测定。     

水平管降膜蒸发器的传热性能

在换热面积为2.375m2的水平管降膜蒸发试验平台上,采用5052铝合金管作为换热管,以实际海水为原料,进行了低温多效海水淡化中水平管降膜蒸发器传热性能研究试验。研究了料液喷淋密度、管外蒸发温度、总传热温差、海水盐度以及管内蒸汽中不凝气含量等因素对海水淡化过程降膜蒸发器总传热系数的影响。结果表明,在试验条件范围内,总传热系数随着料液喷淋密度和管外蒸发温度的升高而增加,随着传热温差的增大而降低;冷凝侧有不凝气存在时,总传热系数下降幅度较大;海水浓度对传热系数影响较小;在控制不凝气含量的条件下,传热系数在3500W/(m2?℃)以上。试验结果为海水淡化的工程设计和生产优化提供了依据。     

Synthesis of nanozeolite A from natural clinoptilolite and aluminum sulfate; Optimization of the method

The zeolite NaA was synthesized from natural clinoptilolite as Si source and aluminum sulfate or sodium aluminate as Al source. The use of aluminum sulfate for the synthesis of zeolite A has not been reported in the literature. This study presents as the first time a synthesis approach in which the low cost and available source is used to prepare zeolite NaA. These nano particles of zeolite were prepared at different conditions in autoclave and a mixer was designed specifically for this purpose. The synthesized zeolites were characterized by instrumental analysis methods, such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM) and wet chemical analysis by atomic absorption spectroscopy (AAS). Cation exchange capacity (CEC) and loss on ignition (LOI) have been also measured on the prepared samples. The influences of different parameters such as reaction time, temperature, initial gel concentration, mechanical stirring and drying conditions on the improvement of the final products were experienced and the procedure for the efficient synthesis of zeolite NaA was optimized with available quality control tests. Solubility of clinoptilolite as the Si source in alkaline solutions was also investigated.     

Synthesis and characterization of boron carbide films by plasma-enhanced chemical vapor deposition

The plasma-enhanced chemical vapor deposition of boron carbide was investigated on quartz glass and alumina substrates from a gas mixture of BCl 3 , H 2 , and CH 4 in an inductively coupled plasma (ICP) medium produced by a radio frequency (RF) discharged onto the gases passing through a tubular reactor under atmospheric pressure. A thin solid boron carbide coating with a gray color was deposited on both substrates. The results of XRD revealed that the major solid phase formed in the coating material was β-rhombohedral B 4 C. The SEM analysis showed that the surface homogeneity increased with an increase in the exposure time, and different boron carbide structures were formed at different RF powers and exposure times.     

SYNTHESIS AND CHARACTERIZATION OF BORON CARBIDE FILMS BY PLASMA-ENHANCED CHEMICAL VAPOR DEPOSITION

The plasma-enhanced chemical vapor deposition of boron carbide was investigated on quartz glass and alumina substrates from a gas mixture of BCl 3 , H 2 , and CH 4 in an inductively coupled plasma (ICP) medium produced by a radio frequency (RF) discharged onto the gases passing through a tubular reactor under atmospheric pressure. A thin solid boron carbide coating with a gray color was deposited on both substrates. The results of XRD revealed that the major solid phase formed in the coating material was β-rhombohedral B 4 C. The SEM analysis showed that the surface homogeneity increased with an increase in the exposure time, and different boron carbide structures were formed at different RF powers and exposure times.     

Characterization of aluminum and boron containing beta zeolites prepared by solid-state recrystallization of magadiite

A method for the preparation of phase-pure [Al]-BEA and [Al,B]-BEA zeolites based on solid-state recrystallization of synthetic aluminum-containing magadiites is presented. For comparison [B]-BEA was prepared by conventional hydrothermal synthesis. From X-ray diffraction (XRD) measurements conclusions could be drawn in respect to kinetics and mechanism of the recrystallization process. Coordination state and resistance to hydrolysis of framework boron species in as-synthesized and ion-exchanged BEA varieties were investigated by ¹¹B MAS NMR spectroscopy. The acidity of the samples was studied by temperature-programmed ammonia elimination (TPAE) from the NH₄-forms and by IR spectroscopy using pyridine as probe molecule. An effect of framework boron on the acid strength of bridged hydroxyls associated with framework aluminum could not be evidenced. Nevertheless, incorporated boron gives rise to weak acid sites which are involved in ion-exchange processes. The number of strong Brønsted sites can be controlled by the aluminum content of the layer silicate.     

氮化硼陶瓷纤维的制备与应用

氮化硼陶瓷纤维是一种正在发展的新型高性能材料,然而传统的高温法很难制备高质量的氮化硼陶瓷纤维材料,只能通过前驱体转化法实现。概述了氮化硼陶瓷纤维的合成路线以及各种前驱体制备氮化硼陶瓷纤维的优缺点,并对前驱体法制备氮化硼陶瓷纤维的发展趋势做了展望。     

Synthesis of nanocrystalline boron nitride by combustion process

Nanocrystalline boron nitride powders were synthesized by combustion process using urea as a fuel. Experiments were carried out by heating boric acid and urea in an N₂ atmosphere at 850°C. Boric acid was used as a source of boron while urea, as a source of nitrogen. The reactions were carried out in an autoclave with provisions for purging with nitrogen gas. The samples were characterized by powder X-ray diffraction, Fourier transform IR spectroscopy (FT-IR), FT-Raman spectroscopy, UV-VIS spectroscopy, and SEM. The article is published in the original.     

含硼温压型燃料的爆炸性能

研究了超细硼粒子在温压型燃料爆炸中的能量效率，通过理论计算、实验室测试和外场实验比较了硼、镁、铝等添加剂在温压燃料中的性能。结果表明，虽然含硼燃料的能量明显高于含镁、铝燃料，但其点火和燃烧条件较为苛刻。爆炸试验时，在相同爆心距处，含硼温压燃料试样的爆炸冲击波压力与含镁、铝温压燃料试样相比没有明显优势。含硼燃料试样的爆炸火球温度较高、高温维持时间更长。为了提高燃料中硼粉的能量效率，需要提供初始高温环境和适当的氧浓度，改善硼粒子的燃烧性能。     

Structure and mechanical characteristics of a layered composite material based on TiB/TiAl/Ti

In this work, a TiB/TiAl/α-Ti layered composite material has been obtained by unrestricted SHS compression using titanium, boron, and aluminum as the initial components. It has been found that combustion and subsequent high-temperature shear deformation (thermal and mechanical conditions of unrestricted SHS compression) results in composite ceramic (TiB/Ti) and intermetallic (TiAl, Ti₃Al) macrolayers to be oriented along the direction of material flow and perpendicularly to the applied load. It is shown that the synthesis of the material proceeds according to the solid/liquid-phase mechanism. The mechanical characteristics of the obtained layered composite material have been studied, namely hardness, microhardness, and fracture toughness. The mechanism of crack propagation has been established and the dependence of the values of the stress intensity factor on the orientation of microvolumes in the material has been determined.     

Lightweight and thermally insulating aluminum borate nanofibrous porous ceramics

Aluminum borate porous ceramics are excellent candidates for high-temperature insulation applications. Current research on aluminum borate-based porous ceramics mainly focuses on porous ceramics made up of aluminum borate whiskers, whose low aspect ratio leads to a relatively dense porous structure; this results in porous ceramics with low porosity and relatively high thermal conductivity. In this study, we report the manufacturing of aluminum borate nanofibrous porous ceramics by an agar-based gel casting method using electrospun nanofibers with a high aspect ratio as the three-dimensional skeleton structure. We explored the effect of the alumina/boron oxide molar ratio on the microscopic morphology and crystal phase composition of the aluminum borate nanofibers and that of the sintering temperature on the micro and macro properties of porous ceramics based on the nanofibers. The results showed that aluminum borate nanofibers with an alumina/boron oxide molar ratio of 7:2 had the densest microscopic morphology, and the corresponding porous ceramics exhibited a higher porosity (91%) and lower thermal conductivity (0.11 W m^?1 K^?1) after sintering at 1200 °C than aluminum borate porous ceramics with aluminum borate whiskers as the skeleton. The successful synthesis of aluminum borate nanofibrous porous ceramics provides new insights into the development of high-temperature insulators.     

Preparation of Aluminum-Doped Zinc Oxide Films by a Normal-Pressure CVD Method

Aluminum-doped zinc oxide films prepared using a normal-pressure CVD (NP-CVD) method were studied as a transparent electrode material. The films were prepared on fused quartz substrates at 500°C using bis(2,4-pentanedionato)zinc and tris(2,4-pentanedionato)aluminum as source material. The transparent films, ∼0.3 μm in thickness, with a transmittance above 80% at a wavelength between 400 and 820 nm, were easily obtained. The optical band gap of the films increased from 3.3 to 3.6 eV with increasing amounts of aluminum dopant. The minimum resistivity of the film was about 4.9 × 10⁻⁵Ω·m.     

质量法测定铝基碳化硼材料中碳化硼的含量

采用HCl溶解质量法测定铝基碳化硼材料中碳化硼的含量。对称样量、水浴温度等实验条件进行了优化,并验证了方法的精密度和准确度。结果表明,质量法测定铝基碳化硼材料中碳化硼的含量,简单、快速,精密度高,结果准确可靠,可用于批量样品测试。     

Use of boron oxide and boric acid to improve flame retardancy of an organophosphorus compound in neat and fiber reinforced polyamide‐6

The aim of this study was to investigate the usability of boron oxide and boric acid to enhance flame retardancy of (aluminum diethyl phosphinate)‐type organophosphorus compound in polyamide‐6 and its 15 wt% of short (glass fiber)‐reinforced composite. Materials were compounded by melt‐mixing method via a twin‐screw extruder, and the specimens for testing and analyses were shaped by injection and compression‐molding. For the neat polyamide‐6 specimens, mass loss cone calorimetry analyses indicated that replacement of a certain amount of aluminum diethyl phosphinate with boron oxide or boric acid could result in significant improvements in many flame‐retardancy parameters. For instance, the suppression in peak heat release rate value of polyamide‐6 could be as much as 84% or 86% for boron oxide and boric acid, respectively, whereas it was only 32% when aluminum diethyl phosphinate was used alone. Char microscopy, thermogravimetric analyses, X‐ray diffraction, and evolved gas analyses revealed that the main contribution of boron oxide and boric acid to the barrier mechanism of aluminum diethyl phosphinate was the formation of additional glassy boron oxide layers and boron phosphate layers. J. VINYL ADDIT. TECHNOL., 22:300–310, 2016. © 2014 Society of Plastics Engineers     

Secondary Phases in Hot-Pressed Aluminum-Boron-Carbon–Silicon Carbide

Silicon carbide hot-pressed with aluminum, boron, and carbon as sintering aids (ABC–SiC), was studied by transmission electron microscopy. Both grain-boundary films and inclusions were prevalent in this material. The present study characterized the inclusions located in triple-junctions, grain boundaries, and the interior of the SiC grains, with emphases on phases not scrutinized before. These inclusions were crystalline, in contrast to the amorphous grain-boundary films. Two dominant types of boron-free triple-junction phases containing Al(Si)-O-C-(S) and Al(Si)-O were identified, where sulfur was an unexpected contaminant, and silicon came from SiO₂ or from dissolution of SiC. Boron-containing inclusions with a composition Al-O-B-C were frequently observed inside SiC grains. Although the boron-free aluminum-rich phases wet the grain boundaries completely and are, therefore, effective sintering additives, the boron-containing Al(Si)-O-B-C did not wet the grain boundaries. The structure and chemical composition of these boron-containing intragranular inclusions were determined, and their mechanism of formation is discussed.     

Purification of Quartz Via Low-Temperature Microwave Chlorinated Calcination Combined with Acid Leaching and its Mechanism

Silicon - As an indispensable raw material for the semiconductor industry, high-purity quartz has great economic and strategic value. Since aluminum (Al) is a common impurity existing in quartz,...     

Synthesis of Aluminum Nitride/Boron Nitride Composite Materials

Aluminum nitride/boron nitride composite was synthesized by using boric acid, urea, and aluminum chloride (or aluminum lactate) as the starting compounds. The starting materials were dissolved in water and mixed homogeneously. Ammonolysis of this aqueous solution resulted in the formation of a precomposite gel, which converted into the aluminum nitride/boron nitride composite on further heat treatment. Characterization of both the precomposite and the composite powders included powder X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Analysis of the composite revealed that the aluminum nitride phase had a hexagonal structure, and the boron nitride phase a turbostratic structures.