二氧化硅改性片状铁粒子的微波吸收性能

The preparation and microwave-absorbing behavior of micrometric silica-modified platelet iron particles (SMPLIP) were investigated. Through precipitation， hydrothermal reaction， silica-modification and reduction with hydrogen， micrometric porous SMPLIP were yielded. The permittivity values of SMPLIP had been significantly decreased due to the presence of silica. Measurements and calculations showed that a 1.93mm thick sample containing SMPLIP as much as 60% by weight was capable of absorbing X band(8.2～12.4GHz) microwaves with reflection loss being greater than -10dB within the frequency range of 8.2～11.36GHz， while the maximum re-flection loss was -14.8dB at 9.4GHz. The results had also shown that it was practicable to prepare thin， light-weight microwave absorbent with SMPLIP.     

Structure and Properties of β-Polypropylene Reinforced by Polypropylene Fiber and Polyamide Fiber

Matrix/fiber composites of β-form isotactic polypropylene(iPP) matrix and α-iPP or PA6 fibers were prepared by laminating technique under different preparation temperatures. The mechanical properties and interfacial morphologies of these composites were studied by tensile test, optical microscopy and scanning electron microscopy, respectively. The experimental results show that the tensile yield load and tensile modulus of β-iPP/PA6 matrix/fiber systems increased significantly at the expense of elongation at break. These mechanical properties show essentially no dependence on the sample preparation temperature. On the other hand, the mechanical properties of iPP matrix/fiber single polymer composites depend strongly on the sample preparation temperature. At low sample preparation temperature, e.g., 172 ℃, the solid α-iPP fiber induces α-iPP crystallization, leading to the formation of α-iPP transcrystalline layer around the fiber. This results in a remarkable increment of the tensile yield load and tensile modulus. The elongation at break is also much better than that of the iPP/PA6 matrix/fiber system. It reflects a better interfacial adhesion of the single polymer composite compared with the iPP/PA6 composite. At higher sample preparation temperature, e.g., 174 ℃ or 176 ℃, the partial surface melting of the oriented fiber allows interdiffusion of iPP molecular chains in the molten fiber and matrix melt. The penetration of matrix chains into the molten iPP fiber results in some iPP molecular chains being included partially in the recrystallized fiber and the induced β-transcrystalline layers. This kind of configuration leads to an improvement of interfacial adhesion between the fiber and matrix, which causes a simultaneous increase of the tensile yield load, tensile modulus and elongation at break of β-iPP.     

Effect of Draw Ratio on the Morphologies and Properties of BPDA/PMDA/ODA Polyimide Fibers

3,3,4,4-Biphenyltetracarboxylic dianhydride/pyromellitic dianhydride/4,4-oxydianiline（BPDA/PMDA/ODA） polyimide copolymer fibers with different draw ratios were prepared from the imidization of polyacrylic acid（PAA） fibers via a dry-jet wet-spinning process.Their morphologies,microcrystal orientations,thermal stabilities,and mechanical properties were investigated via scanning electron microscopy（SEM）,wide angle X-ray diffraction（WAXD）,thermogravimetric analysis（TGA）,and tensile experiments.In order to acquire fibers with better mechanical performance,we aimed at obtaining the optimal draw ratio.Drawing during thermal imidization resulted in a decreased diameter of fiber from 25.8 μm to 16.9 μm corresponding to draw ratio from 1 to 3.5.WAXD results show that the degree of the orientation of the undrawn sample is 64.1％,whereas that of the drawn sample is up to 82％.The as-spun fiber and those with different draw ratios all exhibit high thermal stabilities,i.e.,the temperature at a mass loss of 5％ can reach as high as 570 ℃.The tensile strengths and tensile modulus of the fibers increase with the draw ratios,and the maximum tensile strength and modulus are 0.90 and 12.61 GPa,respectively.     

Preparation of novel Ni-Ir/r-Al2O3 catalyst via high-frequency cold plasma direct reduction process

The novel Ni-Ir/γ-Al2O3 catalyst was prepared by high-frequency cold plasma direct reduction method (NIA-P) under ambient conditions without thermal treatment, and the conventional sample was prepared by impregnation, thermal calcination, and then by H2 reduction method (NIA-CR). The effects of reduction methods on catalysts for ammonia decomposition were studied, and the catalysts were characterized by XRD, N2 adsorption, XPS, and H2-TPD. It was found that the plasma-reduced NIA-P sample showed a better catalytic performance, over which ammonia conversion was 68.9%, at T = 450 ℃, P = 1 atm, and GHSV = 30, 000 h−1. It was 31.7% higher than that of the conventional NIA-CR sample. XRD results showed that the crystallite size decreased for the sample with plasma reduction, and the dispersion of active components was improved. There were more active components on the surface of the NIA-P sample from the XPS results. This effect resulted in the higher activity for decomposition of ammonia. Meanwhile, the plasma process significantly decreased the time of preparing catalyst.     

Preparation of A New Fiber by Sol-gel Technology in Solid-phase Microextraction （SPME）

The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-polar analytes. Efficient SPME-GC-FID analyses of benzenetoluene-ethylbenzene-xylenes (BTEXs) and low-polar halocarbon were achieved by the sol-gel coated DSDA-DDBT-TiO2 fiber. Some parameters of the SPME fiber for the determination of halocarbon in aqueous sample were investigated.     

Preparation and Performance of HGM/PPENK-based High Temperature-resistant Thermal Insulating Coatings

Novel high temperature-resistant coatings with high mechanical strength and thermal-insulating performance were prepared with poly(ether nitrile ketone)(PPENK) resin as matrix and hollow glass microspheres(HGMs) as thermal-insulating filler. The corresponding mechanical and thermal-insulating study indicated that the mechanical properties of the coatings decreased with the increase of HGM content,and were improved after surface modification of HGM by KH570 resulting in enhancement of interaction between HGM and PPENK resin. The thermal conductivity of HGM/PPENK thermal-insulating coating decreased with the increase of HGM content and coating thickness, along with the decrease of the true density. It also showed slight increase trend due to HGMs surface modification. The HGM/PPENK coating filled with modified HGMs showed better thermal resistance than that of unmodified HGM/PPENK coating. The thermal decomposition temperature at 5%weight loss of the coating containing modified HGMs was 10 °C lower than that of pure PPENK, and 40 °C higher than that of neat HGM/PPENK coating. The coating exhibited commendable appearance after 400 °C for 30 min. The merits of HGM/PPENK-based thermal coatings obviously demonstrated promising prospect in thermal protection fields.     

替代M-型钡铁氧体纳米粒子的微波吸收性能

The microwave-absorbing behavior of substituted M-type barium ferrite nano-particles was investigated. The nano-particles were synthesized with coprecipitation-melted salt method. For the purpose of comparison, corre-sponding micro-particles were also prepared through direct coprecipitation and sintering. XRD and TEM of the nano-particles showed that the ferrite was hexagonal in structure and widely distributed in size with particle size being less than 100nm, the complex permittivity and permeability of a 1.50mm thick specimen and a 1.40mm thick specimen containing 60% by weight of substituted M-type barium ferrite nano-particles and micro-particles were measured respectively in X band (8.2～12.4GHz) range, from which the reflection loss (R.L.) of microwaves was calculated and two comparative absorption curves were given. The results showed that the synthetic nano-particles could well absorb microwaves in X band. The absorption was larger than 10dB in the range of 9.2～12.4GHz while the maximum absorption was 38.6dB at 10.6GHz.     

Synthesis and Characterization of High-purity Aluminum Titanate with Water Quenching Method

High-purity aluminum titanate was synthesized via a water quenching method with waste-residue in the aluminum factory and industrial TiO2 as the main raw materials, which belongs to the comprehensive utilization of solid wastes. Compared with the conventional method, it can reduce synthesis temperature, effectively inhibit decomposition and raise the content of AT; the addition of tiny silicon powder can improve the sintering and optimize the properties of AT. The crystalline phase structure and microstructure of each sample were characterized with XRD and SEM methods; the content of each crystalline phase in each sample was confirmed with Rietveld Quantification method; the properties of each sample were also tested. The experimental results showed that No. 4 is the optimum specimen, with the corresponding mass ratio of Al2O3/TiO2 to be 1.27 and the content of AT of 97.2 wt%. The addition of optimum tiny silicon powder is confirmed to be 8wt%; its corresponding bulk density is 2.63 g/cm^3, bending strength is 46.34 MPa, and the retention of one thermal vibration bending strength is 71.5%.     

Simultaneous Removal of COS and H2S at Low Temperatures over Nanoparticle α-FeOOH Based Catalysts

Catalysts using α-FeOOH nanoparticles as the active ingredient were tested by a microreactorchromatography assessing apparatus at atmospheric pressure between 25 and 60℃ with a gas hourly space velocity of 10,000h^-1,while the removal performance of H2S with catalysts was investigated using the thermal gravimetric method.The results show that the catalysts are highly active for COS hydrolysis at low temperatures(≤℃）and high gas hourly space velocity,and the highest activity can reach 100%.The catalyst is particularly stable for 12h,and no deactivation is observed.Nanoparticle α-FeOOH prepared using hydrated iron sulfate shows higher COS hydrolysis activity,and the optimum calcination temperature for the catalyst is 260℃.In addition,the catalysts can remove COS and H2S simultaneously,and 60℃ is favorable for the removal of H2S.The compensation effect exists in nanoparticle-based catalysts.     

Dehydration Kinetics of Zinc Phosphate Tetrahydrate α-Zn3（PO4）2·4H2O Nanoparticle

TG-DTG technique and Harcourt-Esson integrated equation were used to study the dehydration process of zinc phosphate tetrahydrate α-Zn3（PO4）2·4H2O nanoparticle and its thermal decomposition kinetics. The results show that there are three stages of dehydration between 300 and 800 K during the thermal decomposition of α-Zn3（PO4）2·4H2O nanoparticle. The first stage is controlled by chemical reaction with an activation energy of 69.48 kJ·mol^-1 and a pre-exponential factor of 1.77×10^6 s^-1. The second is controlled by nucleation and growth with an activation energy of 78.74 kJ·mol^-1 and a pre-exponential factor of 5.86×10^9 s^-1. The third is controlled by nucleation and growth with an activation energy of 141.5 kJ·mol^-1 and a pre-exponential factor of 1.01×10^12 s^-1. The kinetic compensative effects not only exist in Arrhenius equation but also in Harcourt-Esson equation. Activation energy E is dependent on both the decomposition fraction α and temperature T.