Study on Properties of Magnesia-Hercynite Brick

Using magnesia and hercynite as materials, we researched the magnesia-hercynite brick in order to solve the problem of chrome-free brick used in the burning zone of cement rotary kiln. Effect of different firing temperature and different content of hercynite on properties of the brick were studied. The results show that the magnesiahercynite specimen fired at 1600℃ was densified and when the hercynite content is 7%, the cold crushing strength and the adhesive strength of rupture of the specimen have the highest value.     

Influence of Nano-Al_2O_3 on Properties of Magnesia Chrome Refractories

Magnesia chrome bricks were prepared with fused MgO-Cr2O3 synthesized material,fused magnesite and chrome ore as main starting materials. Nano-Al2O3 was added into refractories ( 2% ,4% and 6% in mass) substituting for Al2O3 micropowder. After mixing and shaping,the bricks were fired at 1 550 ℃ ,1 600 ℃ , 1 650 ℃ and 1 750 ℃ ,respectively. The microstruc-ture,sintering property,mechanical properties,thermal shock resistance and slag resistance of the specimens with the addition of nano-Al2O3 were investigated. The re-sults indicate that the performance of brick with 4 mass% of nano-Al2O3 is greatly improved after firing at 1 650 ℃ .     

Antioxidant Coating of SEN for Thin Slab Con-casting

The SEN for thin slab con-casting is easy to break and damage because of the oxidation during preheating and application. The enamel coating material is generally applied on the surface of SEN to avoid the oxidation. The coating material with born glass and silicon as main starting materials and silica sol as binder was studied. ZrO2 - C and Al2O3 - C materials containing 15% carbon were isostatic pressed, and heated at 600 ℃ , 900 ℃ , 1 200 ℃ , 1 500 ℃ for 2 h, respectively. The results show that the coating material with 70% of boron glass and 30% of silicon bonded by silica sol can form denser protection layer in the above mentioned materials at the range of 600 -1 500 ℃. The oxidation area ratio and weight loss ratio with the coating are much lower than those without the coating.     

Effects of B_4 C and Si Antioxidant on Oxidation Resistance of Low-carbon MgO-C Brick

Low-carbon MgO-C specimens with dimension of 36 mm×36 mm were prepared using fused magnesia, flake graphite and carbon black as main starting materials, thermoplastic phenolic resin as binder, hexamethylene tetramine as curing agent, Si powder (w(Si)＞80%, particle size <0.074 mm) and B4C (d90=36.5 μm) as antioxidant, pressing under 200 MPa and drying at 200 ℃ for 24 h. The oxidation resistance tests were conducted at 600 ℃, 1 000 ℃ and 1 400 ℃ for 2 h, respectively. Effects of B4C and Si antioxidant on oxidation resistance of low-carbon MgO-C brick were studied by comparing the areas of the decarburized layers. The results show that: (1) When Si powder addition is 3%, at 600 ℃ and 1 000 ℃, the specimens with 0.5% B4C perform good oxidation resistance; at 1 400 ℃, the oxidation resistance of the specimens is improved with the addition of B4C increasing, and that of the specimen with 0.7% B4C is the best. (2) When B4C addition is 0.5%, at 600 ℃ and 1 000 ℃,the oxidation resistances of the specimens with 3% and 5% Si powder are similar, which are better than that of the specimen with 1% Si powder; and at 1 400 ℃, the oxidation resistance of the specimens is improved obviously with the addition of Si powder increasing, and that of the specimen with 5% Si powder is the best. (3) Based on the results, it is believed that the low-carbon MgO-C brick with 0.5% B4C and 3% Si powder performs the best oxidation resistance.     

Effect of Pyrophyllite Addition on Properties of Lightweight Insulation Refractory Materials

To solve the problem of over-high density of lightweight insulation refractory bricks prepared with fly ash,new lightweight insulation refractory materials with density 0. 89 g·cm~(-3) were synthesized using pyrophyllite,fly ash,and Suzhou clay as the main starting materials and saw dust as the pore forming substance,and controlling the addition of the pyrophyllite( 20%,30%,and 40% by mass) and the treating temperature( 1 250,1 300,1 350,and 1 400 ℃). The synthesized materials were characterized by the XRD,SEM and the thermal conductivity measuring instrument. The results show at pyrophyllite addition of 30% and treat temperature of 1 400 ℃,the material can achieve linear shrinkage of 6. 6%,apparent porosity of 57%,bulk density of 0. 75 g·cm~(-3),compressive strength of 2. 7 MPa,and thermal conductivity at 350 ℃ of 0. 152-0. 216 W·( m·K)~(-1). This indicates that the pyrophyllite decomposition at high temperatures forms mullite and amorphous quartz introducing volume expansion,which counteracts some shrinkage at high temperatures.So it is feasible to use pyrophyllite,fly ash waste and clay to prepare lightweight insulation refractory materials.     

Effect of Microsilica on Chemical Bond of Calcium Aluminate Cement Bonded Corundum Castable at Low and Intermediate Temperatures

Calcium aluminate cement bonded corundum castable specimens were prepared using brown fused corundum( 8- 5,5- 3,3- 1 mm),white fused corundum( ≤ 1,≤ 0. 045 mm),micro-sized α-Al_2O_3 and microsilica as starting materials. This work focused on investigating the relationship between the bond change in the castable matrix and the strength of the castable with 5 mass% microsilica or without microsilica after heat treatment at 110,800 and 1 000 ℃, respectively.Chemical bond changes between the microsilica and hydrates of calcium aluminate cement after drying at110 ℃ or firing at 800 ℃ were investigated by XPS and FTIR. The results show that Si—O—Al bonds form between the microsilica and hydrates of calcium aluminate cement after drying at 110 ℃ or firing at 800 ℃.Therefore,the increased strength of castable specimens is attributed to the formation of Si—O—Al bonds from110 ℃ to 800 ℃.     

Effect of KCI on Growth of Carbon Fibers During Carbonization of Phenolic Resin

Effects of the KCl additions( 1%,3%,5% and7% of the phenolic resin mass) on phase composition and microstructure of the resin carbon and the growth mechanism of carbon fibers were investigated by using commercial liquid phenolic resin as carbon source and micron-scaled KCl as catalyzer,mixing,hexamethylenetetramine solidification treating,carbon-embedded firing at 1 000 ℃ for 3h in order to accelerate the graphitization of phenolic resin during carbonization. The results show that the graphitization degree of resin carbon is improved by catalysis of KCl,numerous carbon fibers with30-200 nm in diameter and 10-20 μm in length and sheet-like carbon in situ grow in resin carbon. The optimal addition of KCl is 5% when lots of carbon fibers can be found in resin carbon,and d002 diffraction peak of graphite appears obviously in the XRD pattern. The growth mechanism of carbon fiber is that the molten KCl at high temperatures absorbs carbonaceous gas from the decomposition of phenolic resin,accelerating the diffusion of solid C atoms in liquid KCl; after the dissolution of C saturates,carbon atoms separate continuously in local parts to form carbon fibers or flakes; meanwhile,the concentration gradient formed by local carbon atoms in the melt offers growth drive for the separation of carbon fibers or flakes on KCl surface.     

Preparation of ZrN （ZrON）-SiAlON Composite Ceramics via a Pressureless Sintering Process

ZrN-SiAlON composite materials were synthesized at 1 550 ℃ for 6 h via a carbothermal reduction nitridation route using fly ash （≤74 μm）,zircon （≤ 44 μm） and active carbon as starting materials.The processed ZrN-SiAlON composite micropowders were mixed with polyvinyl alcohol as binder to prepare ZrN （ZrON）-SiAlON composite ceramics by carbon-embedded pressureless firing at 1 450,1 500 and 1 550 ℃ for 1 h,respectively.Influences of firing temperature on the phase compositions,microstructure and sintering properties of the ceramics were investigated.The results show that：（1） β-SiAlON based composite ceramics with different compositions can be prepared by controlling firing temperature,and the main crystalline phases of the specimen fired at 1 550 ℃ for 1 h involve ZrN,ZrON and β-SiAlON （z =2,Si4Al2O2N6）; （2） ZrN （ZrON）,β-SiAlON and a Fe-Si based compound can be observed in the microstructures of the specimens fired at different temperatures.ZrN （ZrON） particles distribute homogeneously in the β-SiAlON matrix; （3） raising firing temperature can increase the shrinkage ratio of the ceramics,and the volume shrinkage ratio increases from 19.4％ to 40.3％ when the firing temperature rises from 1 450 to 1 550 ℃.     

β-SiAlON Hollow Spheres Prepared from Coal Fly Ash Microspheres

β-SiAlON hollow spheres were prepared by carbothermal reduction method, using coal fly ash (＜15 μm, 43-77 μm, and ＞100 μm) and active carbon in some proportion (20% less than theoretical addition, theoretical addition and 10% excess theoretical addition) as starting materials, putting into alumina crucible in high temperature nitriding furnace after well mixed, and holding at 1 300 ℃, 1 350 ℃, 1 400 ℃, 1 450 ℃, and 1 500 ℃ for 6 h. Effects of temperature, particle size of the microsphere, and addition of active carbon on the phase composition and microstructure of the nitridized products were studied by means of XRD and SEM. The results show that the nitridation reaction starts at 1 300 ℃; excess active carbon is necessary to form β-SiAlON hollow spheres, and particle size is the important parameter to form the hollow spheres nitridized products β-SiAlON; at 1 500 ℃, when the active carbon is 10% in excess, the β-SiAlON hollow spheres, which were prepared using coal fly ash with particle size＞100 μm, are featured with rough surface, high hollowness and low density.     

Effect of Ti （C,N） on Properties of Low-carbon MgO- C Bricks

The effect of Ti （ C, N） on properties of low-carbon MgO - C bricks was investigated. The phase composition and the microstructure of the matrix of low-carbon MgO - C brick containing Ti （ C, N） were studied by XRD and SEM analysis together with EDS. The results showed that Ti （ C, N） distributed in the matrix of lowcarbon MgO - C brick uniformly after being treated at 1 600 ~C for 3 h in coke powder bed, and Ti （C, N） and MgO formed a solid solution. After the treatment at 1 600 ℃ for 3 h in coke powder bed, the bulk density and cold crushing strength of low-carbon MgO - C brick with Ti （ C, N） decreased, and the apparent porosity and linear change rate of specimens increased. The oxidation resistance of low-carbon MgO - C brick with Ti（ C, N） was superior to that of low-carbon MgO - C brick with no additives, but inferior to that of low-car- bon MgO - C brick with Al powder. The slag resistance of the specimen with Ti （ C, N） was excellent as well.     

磷灰石中氟的测定

研究了采用1mol／L盐酸低温分解矿样，以二甲酚橙-锆减色法测定矿石中的氟，铝的干扰可在显色后放置一定时间予以消除，该法具有灵敏度高、重现性好、易掌握等特点。     

制氟技术及氟的应用

氟是非常独特的元素,它赋予含氟材料和含氟化学品许多优异的性能,在国民经济领域应用广泛,因此研究制氟技术具有重要现实意义。本文主要介绍电解法、化学药剂法和等离子体裂解法制氟技术,并对每种技术的特点和研究现状进行分析,同时对氟气的应用进行概述。     

无机氟化工氟资源综合利用发展现状与建议

无机氟化工被誉为"黄金"产业,在国民经济和社会发展中占有重要地位。介绍和分析了中国氟资源的存在形式、综合利用现状以及存在的问题。指出中国氟资源主要存在于萤石、磷肥副产物和电解铝废渣中。目前,中国氟化工生产主要以萤石资源为主,而萤石是不可再生资源,且面临资源短缺问题;磷肥副产物中的氟仍未充分开发和利用,造成大量氟资源的浪费;电解铝含氟废渣中的氟回收利用有待开发。提出了中国氟资源综合利用发展建议。     

Microwave-assisted solvothermal synthesis of sodium metal fluoride (NaxMFy) nanopowders

In this study, we have developed a simple, versatile, and rapid solvothermal process for the preparation of sodium metal fluoride (Na_xMF_y) nanopowders (NaCoF₃, NaMnF₃, and Na₃FeF₆) using a microwave digestion system. Microwave heating significantly reduces the reaction time compared to conventional heating methods. The Na_xMF_y nanopowders have cluster structures consisting of small primary nanoparticles, thus resulting in a large surface area of >60 m² g⁻¹. The effect of an essential additive is also investigated to confirm the optimal conditions for obtaining large-surface-area Na_xMF_y nanopowders without impurities. We expect that this study will promote further research into the development and application of various nanostructured Na_xMF_y materials.     

全球含氟农药品种概况及新开发的含氟农药

氟化学品是人们开发的热点,含氟农药也是人们开发的关注点。阐述了全球含氟农药的概况,并介绍了近年新开发的含氟农药。     

Phase Diagram of the System KF–AlF3

The system KF–AlF₃ was reinvestigated precisely by differential thermal analysis, X-ray diffractometry, and visual observation. All of the samples for the present investigation were prepared by solution synthesis. The results verified the existence of 2KF·AlF₃ (K₂AlF₅) and KF·4AlF₃ in the phase diagram; both compounds were orthorhombic. The cell parameters of the compounds were, respectively, a = 10.87 ± 0.03 Å, b = 10.36 ± 0.01 Å, c = 7.83 ± 0.03 Å, and a = 7.89 ± 0.01 Å, b = 7.57 ± 0.01 Å, c = 6.94 ± 0.01 Å. KAlF₄ was confirmed to melt congruently at 575°± 2°C by careful examination.     

Performance and structure evolution of fluoindinate glass at high temperatures

Fluoindinate glass (FIG) is considered an ideal material for fiber laser devices and mid-infrared bulk optics components owing to its ultra-low phonon energy and broad transparency window. However, the heat generated by devices fabricated with FIG during their operation limits its application. Therefore, there is an urgent need to study its high-temperature properties. In this study, the thermal properties, microstructure, crystal phase behaviors, and optical and luminescent properties of high-temperature FIG were comprehensively evaluated. We also attempted to reveal the changes in its structure at high temperatures using variable-temperature Raman spectroscopy. We first found that the stretching vibration intensity of nonbridging F(F_nb) decreases, and the bending vibration of FIG increases with an increase in temperature, indicating that high temperatures could lead to the fracture of bridge bonds between some [InF₆]³⁻ octahedrons. Certainly, this will lead to glass structural instability, which will further increase the tendency of FIG to undergo devitrification in high-temperature conditions. We believe that this work will provide a reference for the performance improvement and application of fluoride glass at high temperatures.     

热固性氟树脂在卷材涂料及喷涂铝单板涂料中的应用

热固性氟树脂用于卷材涂料涂装涉及到多项性能的平衡调整,本文从底漆和氟碳面漆的角度探讨了这些性能的影响因素。并根据树脂和配漆两方面所进行的试验,介绍了解决这些问题的方法。     

NMR Studies of Fluorine in Aluminosilicate–Lanthanum Fluoride Glasses and Glass-Ceramics

NMR determinations of fluorine environments in transparent oxyfluoride glass-ceramics were made to learn about the crystallization of LaF₃, as well as to ascertain the structural role of fluorine in the surrounding glassy matrix. The fraction of fluorine in LaF₃ was measured as a function of heat treatments, demonstrating significant differences between glasses modified with barium and those containing sodium. The results of these measurements showed that not all of the fluorine formed LaF₃ in these glass-ceramics, with resolution of additional fluoride sites at −135 and −185 ppm, due primarily to Si–F and Al–F bonding, respectively. Not only is the evidence of Si–F bonding unexpected, given the presence of aluminum, but the amount of Si–F bonding is sensitive to the type of modifier in the glass. Samples containing barium oxide as the modifier showed a higher fraction of Si–F bonding than those modified with sodium oxide.     

Pressureless Sintering and Mechanical and Biological Properties of Fluor-hydroxyapatite Composites with Zirconia

Fluor-hydroxyapatite (FHA) fabricated by a reaction between fluorapatite (FA) and hydroxyapatite (HA) was mixed with ZrO₂ to produce FHA–ZrO₂ composites. When the relative amount of FA to HA increased, the decomposition of the composite was decreased gradually because of the formation of thermally stable FHA solid solutions. With such suppression of decomposition, the FHA–ZrO₂ composites retained fully densified bodies. As a result, significant enhancements in mechanical properties, such as hardness, flexural strength, and fracture toughness, were achieved as the relative amount of FA to HA increased. The highest values in strength and toughness were 220 MPa and 2.5 MPa·m^1/2, respectively, with FHA–40 vol% ZrO₂ composites. In vitro proliferation of osteoblast-like cells (MG63) on the composites showed behavior similar to that observed on pure HA and FHA. Alkaline phosphatase (ALP) activity of the growing cells (HOS) on the composites was slightly down-regulated compared with that on pure HA and FHA at prolonged periods.