Properties of super heat-resistant silicon carbide fibres with in situ BN coating

An in situ BN coating was prepared on the surface of a nearly stoichiometric continuous SiC fibre with trademark Cansas-3301 (C3). The coated fibre was then subjected to continuous pyrolysis at 1800 °C, obtaining a fibre named Cansas-BN-1800 (C18). After annealing in Ar at 1500 °C for 1 h, the strength retention ratio of C3 was 49%, and that of C18 was almost unchanged. The strength decrease of the C3 fibre was mainly caused by the formation of surface defects resulting from fibre decomposition and active oxidation. However, the in situ BN coating on C18 protected the fibre from forming surface defects, resulting in high strength. Due to slight growth of the grain and purification of the grain boundary during fast heating at 1800 °C, C18 showed excellent creep resistance in the range of 1200–1500 °C.     

沥青纤维的预氧化研究(Ⅰ)——纤维结构的变化

为了对国产各向同性石油沥青纤维的氧化性能进行分析,给今后深入系统地研究其氧化规律打下基础,本文用自制的氧化炉将软化点在220～243℃范围内的四种沥青纤维于空气中进行了预氧化处理,对原丝及预氧化丝进行了增重分析、元素分析、红外分析和在氯仿中的不溶性分析。结果表明:在选定的氧化条件下,沥青纤维的分子之间产生了交联结构,预氧化丝的耐热性和不溶解性都得到了明显的改善。这说明国产通用级石油沥青具有制造碳纤维所需的氧化性能。     

Effect of carbonization temperature on the structure and microwave absorbing properties of hollow carbon fibres

A series of polyacrylonitrile-based hollow carbon fibres (PAN-HCFs) were prepared by carbonizing polyacrylonitrile (PAN) hollow cured fibres at temperature ranging from 550 to 950 °C for 1 h in nitrogen. The effects of carbonization temperature on the structure, elemental compositions, surface electrical conductivity, electromagnetic parameters and reflectivity of PAN-HCFs were investigated. Results indicate that the obtained PAN-HCFs have not been graphitized and the C content and surface electrical conductivity increases as the carbonization temperature increases. The reflectivity of composites of PAN-HCFs and resin is −7.50 dB at 6.06 GHz and the band of the reflectivity under −5 dB is 6 GHz when the carbonization temperature is 750 °C.     

Electrochemical insertion of sodium into hard carbons

The electrochemical insertion of sodium ions into different types of hard carbons was achieved in electrolytes composed of ethylene carbonate as the solvent and NaClO₄ as the salt. For all the materials studied the sodium uptake increases when the carbon highest heat treatment temperature (HTT) decreases. PAN-based carbon fibres appear to be suitable structures to allow significant sodium insertion. Thus, T650 ex-PAN fibres lead to a reversible capacity close to 209 mAh g⁻¹. In that case, sodium insertion occurs in two main ways: one is the adsorption on the single graphene layers and the other is the concomitant insertion into the porosity that occurs below 0.1 V versus Na⁺/Na. This second mechanism, which is indicated by a low-voltage plateau on the electrochemical curves, allows significant insertion. The compared electrochemical study of two saccharose-coke samples corresponding to different regions of Dahn's classification underlines the importance of the carbon precursor and of the manufacture process. The reversible capacity is equal to 184 mAh g⁻¹ for the sample heat treated at 800 °C which presents a high hydrogen content whereas it is close to 145 mAh g⁻¹ for the one characterized by a HTT of about 1500 °C and a low hydrogen content. The best electrochemical performances are obtained for pyrolyzed cellulose carbons. Indeed, the reversible capacity is about 279 mAh g⁻¹. Outgassing these carbons at 950 °C results in such a decrease of the reversible capacity down to 145 mAh g⁻¹. That can be related either to the thermal elimination of heteroelements or to modifications of the pore size distribution. Consequently, the most suitable hard carbon material for anodic applications in rechargeable sodium-ion batteries should both present a high residual hydrogen content and a significant microporosity.     

松弛热定型对可染丙纶结晶结构及上染率的影响

本文以松弛热定型的方式对分散染料可染丙纶分别在１０５，１１０，１２０，１３０，１３５，１４０℃处理２０ｍｉｎ．采用Ｘ－ｒａｙ衍射法测定试样的结晶度，并计算（１１０）晶面法线方向的晶粒尺寸；测定了定型前后的试样在常压沸染下的上染率．从而，研究了试样定型前结晶结构与纺丝成形条件的关系、定型后结晶结构的变化及其与上染率的有机联系．     

Acetone—Formaldehyde—Phenol based IPNs for Glass Fibre Reinforced Composite Applications

Abstract

Three component IPNs Glass fibre reinforced composites (GRC) have been prepared from acetone-formaldehyde-phenol (AF-P) resin, Diglycedyl ether of bisphenol-A (DGEBA) (a commercial epoxy resin) and methyl methacrylate (MMA) (a vinyl monomer). The curing catalyst hexamethylene tetramine (HMTA) for AF-P, radical initiators 2,2′-azobisisobutyronitrile (AIBN) for MMA and curing catalyst 4,4′-diamino diphenyl methane (DDM) for epoxy resin were employed. All the IPN GRCs were characterized in terms of their resistance to chemical reagents, thermal behaviour (DSC, TGA) and mechanical properties.     

催化燃烧法净化碳纤维含氰废气的试验研究

使用 NZP—4型催化剂,对吉林炭素厂含氰废气进行催化燃烧试验,取得了满意的结果。     

Electrically conducting nylon 6,6–polyaniline short composite fibres synthesised by the solvent coagulation method

Polyaniline (PANI) was blended with nylon 6,6 in concentrated H₂SO₄ and HCl solutions. The solvent coagulation method was utilised to extract short composite fibres of a centimetre in length. A solution of n-butyl acetate, acetone, toluene, 1 μM HCl and chloroform were used as coagulating bath to extract the fibres. The diameters of the fibres ranged from 200 to 300 nm, while the length measured approximately 1 cm, as determined from Scanning Electron Microscopy (SEM). The electrical conductivity varied from 10⁻⁴ to 10⁻² S/cm for different mass fractions of PANI (x_PANI) in the composite fibres. The percolation threshold was reached at x_PANI values between 0.15 and 0.2, and further addition of PANI resulted in saturation of the conductivity of the composite fibre. To observe the effect of MWCNTs on the electrical conductivity of the nylon–PANI fibres, 0.04 g, 0.08 g, 0.4 g and 0.5 g of MWCNTs (1, 2, 10, 12.5 weight percentage, respectively) were added into the nylon–PANI solution and were extracted as fibres in the aforementioned solvents. The electrical conductivity of the short fibres increased by an order of magnitude (0.372 S/cm at 12.5 wt.%) when they were extracted in the presence of the MWCNTs. PANI doped in concentrated HCl exhibited an electrical conductivity of 4.46 S/cm.     

聚丙烯纤维着色技术进展

本文对改性聚丙烯纤维及未改性聚丙烯纤维染色技术及色母粒着色技术近期进展作了综述,并对其发展前景进行了预测、讨论.     

Effect of carbonization time on the structure and electromagnetic parameters of porous-hollow carbon fibres

A series of polyacrylonitrile-based porous-hollow carbon fibres (PAN-PHCFs) were prepared by carbonizing PAN porous-hollow cured fibres at 1073 K for different times in nitrogen. The effects of carbonization time on the structure, electrical volume conductivity and electromagnetic parameters were investigated. Results indicate that the degree of graphitization increases as carbonization time increases. The electrical volume conductivity increases as the degree of graphitization and carbonization time increase. The real and imaginary parts of the complex permittivity (′ and ″) increase with carbonization time increasing. The values of ′ and ″ of composites of PAN-PHCFs and paraffin are 13.76 and 10.09 when the carbonization time is 240 min, and the electrical volume conductivity of PAN-PHCFs is 190.47 Ω⁻¹ m⁻¹.