Preparation of long alumina fibers by sol-gel method using tartaric acid

Long alumina fibers were prepared by sol-gel method.The spinning sol was obtained by mixing aluminum nitrate,tartaric acid,and polyvinylpyrrolidone with a mass ratio of 10∶3∶1.5.Thermogravimetry-differential scanning calorimetry （TG-DSC）,Fourier transform infrared （FT-IR） spectra,X-ray diffraction （XRD）,and scanning electron microscopy （SEM） were used to characterize the properties of the gel and ceramic fibers.A little of α-Al2O3 phase is observed in the alumina precursor gel fibers sintered at 1273 K.The fibers with a uniform diameter can be obtained when sintered at 1473 K,and its main phase is also indentified as α-Al2O3.

Preparation of Long Alumina Fibers in Aqueous Solution Using Oxalic Acid and Aluminum Nitrate

Long alumina .fibers with 60 cm in length were pre- pared by sol - gel method. The spinning sol was ob- tained by mixing aluminum nitrate, oxalic acid, and polyvinylpyrrolidone with a mass ratio of 10： 3： 2. Fourier transform infrared （ FTIR ） spectra, X-ray diffraction （XRD） , and scanning electron microscopy （SEM） were used to characterize the properties of the gel and ce- ramic fibers. The fibers with uniform diameter and smooth surface were obtained by sintering at 1 200℃ for 1 h, and their main phase was indentified as α-Al2O3.

Effects of Different Raw Materials and Additions on Wave Transparency of Alumina Fiber Products

Fiber products for microwave kilns were prepared using alumina fibers with alumina contents of 72 mass%and 80 mass%,and calcined alumina powder(4-6μm)as the main raw materials,silica sol as the binder,and cationic starch as the flocculant.Effects of different raw materials and their additions on the wave transparency of fiber products were researched.The results show that as the alumina fiber(72%)addition increases,the heating rate of the samples first decreases and then increases,and the corresponding wave transparency of the sample first increases and then decreases.When the alumina fibers addition is 40 mass%and the alumina powder addition is 30 mass%,the prepared microwave kiln lining material has a higher mullite content,which improves the wave transparency of the sample.The sample prepared from alumina fibers with an alumina content of 80%has a suitable glass-mullite phase ratio,performs lower overall dielectric constant and good wave transparency,and is a suitable lining material for microwave kilns.

Recent Progress on Fabrication of Thermal Conductive Aluminum Nitride Fibers

Among nitride fibers,aluminum nitride(AlN)fibers have been developed for various advanced applications due to their mechanical flexibility,high thermal conductivity,and excellent electrical insulation and chemical stability.This article presents an overview on the recent progress of AlN fibers.The properties of AlN,particularly the thermal conductivity of AlN in polymer matrix composites are introduced.Afterward,two major approaches,carbothermal reduction and nitriding polycrystalline alumina fiber,for the preparation of AlN fibers are discussed.The carbothermal reduction includes electrospinning,solution blow spinning,and chemical vapor deposition.Furthermore,some perspectives on the future directions for the preparation and application of fibrous AlN are highlighted.This review is expected to provide readers with valuable guidance on the preparation of AlN fibers and inspire researchers to explore more potential applications.

Atomic layer deposition of Al_2O_3 on porous polypropylene hollow fibers for enhanced membrane performances

Porous polypropylene hollow fiber(PPHF) membranes are widely used in liquid purification. However, the hydrophobicity of polypropylene(PP) has limited its applications in water treatment. Herein, we demonstrate that, for the first time, atomic layer deposition(ALD) is an effective strategy to conveniently upgrade the filtration performances of PPHF membranes. The chemical and morphological changes of the deposited PPHF membranes are characterized by spectral, compositional, microscopic characterizations and protein adsorption measurements. Al_2O_3 is distributed along the cross section of the PP hollow fibers, with decreasing concentration from the outer surface to the inner surface. The pore size of the outer surface can be easily turned by altering the ALD cycles. Interestingly, the hollow fibers become much more ductile after deposition as their elongation at break is increased more than six times after deposition with 100 cycles. The deposited membranes show simultaneously enhanced water permeance and retention after deposition with moderate ALD cycle numbers.For instance, after 50 ALD cycles a 17% increase in water permeance and one-fold increase in BSA rejection are observed. Moreover, the PP membranes exhibit improved fouling-resistance after ALD deposition.

High Alumina Fiber Composite SiO_2 Based Nanoporous Insulation Boards

The specimens were prepared with high alumina fiber accounting for 0. 5% , 10% or 15% by mass of the total amount of amorphous silica and high alumina fiber, using phenolic resin as binder, and extra-adding 0 or 0. 5% ZnO as sunscreen to cut the cost of SiO2 nanoporous insulation board. The hot volume stability and thermal conductivity （flat plate method ） of the specimens were tested and multi-Jimetion simulation equipment was used to study the thermal insulation performante. The results show that： （1） with high alumina fiber addition increasing, the linear shrinkage rate decreases, but thermal eonductivity changes a little; （2） adding ZnO can decrease thermal conductivity obviously; （3）for the specimen with ZnO and 15% of high alumina fiber, its cold face temperature hardly rises during the simulation experiment at 1 000 ℃ for 2 h, and the cold face temperature of the specimen with the smallest thickness of 2 cm doesn＇t exceed 180 ℃.

Influence of Heating Rate and Calcining Temperature on Properties of 95 Polycrystalline Alumina Fiber

The swung gel fibers were hea, ted to 400 ℃ at 0. .5 ,1, 1.5,2,2.5,3and4 ℃ min^-1 of heating rate, respectivel, and soaked.for 1 h ; then heated to 600 ℃ at 3 ℃ min ^-1 of.heating rate amt soaked for 1 h at last calcined m 1 000, 1 100, 1 200, 1 300, and 1 400 ℃.for 1 h, respectively.

Structural and thermophysical properties characterization of continuously reinforced cast Al matrix composite

In this work the process of manufacturing a continuously reinforced cast Al matrix composite and its properties are presented. The described technology permits obtaining a structural material of competitive properties compared to either heat treatable aluminum alloys or polymer composites for several types of applications. The examined thermophysical properties and structural characterization, including material anisotropy, coupled with the results of previous measurements of the mechanical properties of both Al2O3 reinforcing filaments and metallic prepregs have proven the high quality of this material and the possibility of its operation under special loading modes and environmental conditions. Microscopic examinations (LM, SEM) were carried out to reveal the range of morphological homogeneity of the microstructure, the anisotropy of the filament band distribution, and simultaneously the adhesive behavior of the metal/fbier interface. The 3D morphology of the chosen microstructure components was revealed by computed tomography. The obtained results indicate that special properties of the examined prepreg materials have been strongly influenced, on the one hand, by the geometry of its internal microstructure, i.e. spatial distribution and volume fraction of the Al2O3 reinforcing filaments and, on the other hand, by a very good compatibility obtained between the individual metal prepreg components.

Application of ceramic short fiber reinforced Al alloy matrix composite on piston for internal combustion engines

The preparation and properties of ceramic short fiber reinforced Al-Si alloy matrix composite and it's application on the piston for internal combustion engines are presented. Alumina or aluminosilicatefiibers reinforced Al-Si alloy matrix composite has more excellent synthetical properties at elevated temperature than the matrix alloys. A partially reinforced Al-Si alloy matrix composite piston produced by squeeze casting technique has a firm interface between reinforced and unreinforced areas, low reject rate and good technical tolerance. As a new kind of piston material, it has been used for mass production of about 400,000 pieces of automobile engines piston. China has become one of a few countries in which aluminum alloy matrix composite materials have been used in automobile industry and attained industrialization.