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1.
《Ceramics International》2020,46(6):7861-7870
This study proposes a combustion-based ceramic matrix composite processing technique intended on single-step in situ deposition of single-crystal SiC nanowires (SiCnw) on the surface of carbon fibers (Cf) and formation of SiCnw–reinforced SiC matrix. This was accomplished by Ta-catalyzed combustion of poly-(C2F4)-containing reactive mixtures with pre-mixed chopped Cf. Depending on the combustion conditions, carbon fiber surface is subjected either to formation of diffusion layers, ceramic particle incrustation or growth of continuous arrays of carbon-coated single-crystal SiCnw with a nearly defect-free lattice, 10–50 nm diameter and 15–20 μm length. Thermodynamics, phase and structure formation mechanisms are explored, and the optimal conditions are outlined for reproducible Cf/in situ SiCnw dual reinforcement of SiC-based ceramics. Hot pressing at 1500 °C produced Cf/in situ SiCnw-reinforced ceramic SiC–TaSi2 specimens with a relative density of 97%, 19 GPa Vickers hardness, 3-point flexural strength σ = 420 ± 70 MPa and fracture toughness K1C = 12.5 MPa m1/2.  相似文献   

2.
To investigate the effects of different structure units on the ablation properties of C/C-ZrC-SiC composites produced from 2D needled carbon fiber preforms as reinforcements, non-woven layer, short-cut fiber web and the surface of laminated layers of the composites were ablated by oxyacetylene flame respectively. Results showed that the formation ability of surface protective layer and the fiber orientation were the key factors, determining ablation properties of different structure units. Short-cut fiber web presented the best ablation resistance due to the forming of compactly integrated ZrO2 self-protection coating because of its sufficient ceramic content. However, only scattered oxide particles formed on the ablated surface of non-woven layer, which resulted in serious erosion of carbon fibers and carbon matrices, leading to the poor ablation resistance. Compared with the non-woven layer perpendicular to the flame, the anti-ablation property was even worse when it paralleled to the flame.  相似文献   

3.
Direct use of lignocelluloses fibers as substrate for fabrication of conductive, electroactive, biodegradable, and low‐cost electrode materials are in demand for high‐tech applications of ion‐exchange and energy storage devices. This article presents the preparation and characterizations of conductive and electroactive lignocelluloses‐polyaniline (cellulose/PANI) composite paper. Lignocelluloses fibers were directly collected from the stem of self‐growing plant, Typha Angusitfolia, and subsequently coated with the conductive and electroactive layer of PANI through chemical synthesis. Individual PANI‐coated lignocelluloses fibers were converted into sheet and further characterized with Scanning Electron Microscopy, Fourier Transform Infrared, Thermogravimetric Analysis, electronic conductivity, and Cyclic Voltammetry. Cellulose/PANI composite paper revealed superior thermal characteristics and used as a working electrode in three different electrolytes for ion‐exchange properties. Conductive composite paper (CCP) showed the charge storage capacity of ~52 C/g at scan rate of 5 mV/s in 2M HCl solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42293.  相似文献   

4.
司班表面活性剂对氢氧化铝表面改性的研究   总被引:1,自引:0,他引:1  
对司班表面活性剂湿法改性氢氧化铝的工艺条件进行了探讨,并利用接触角测试、粒径分析、红外光谱(IR)及热重-差示扫描量热(TG-DSC)等测试表征手段,对氢氧化铝的改性效果进行了分析。结果表明,改性剂用量、改性温度及时间等工艺条件对氢氧化铝的改性效果有显著影响,且不同司班表面活性剂对应的最佳工艺条件也有差别,其中以S-60作为改性剂,在用量为0.03(与氢氧化铝的质量比),温度为85 ℃时,经60 min改性得到的氢氧化铝效果最好。通过改性,氢氧化铝的粒径分布变得更加均匀,颗粒表面的润湿性由亲水转变为亲油。司班表面活性剂主要通过物理吸附作用实现对氢氧化铝的改性,因此氢氧化铝的化学结构没有发生变化,热稳定性也未受到明显影响。  相似文献   

5.
p-Si electrodes coated with linear polyethylenimine (L-PEI) allow the fabrication of a pH sensitive film for potentiometric transducers. The coating is realized in one step through the anodic oxidation of pure ethylenediamine (EDA) charged with 0.1 M LiCF3SO3 (Lithium Triflate). Such an electrochemical procedure leads to the thickness control of the coating. The best silicon surface pre-treatment before any coating is obtained with potassium dichromate in sulfuric acid, which leads to OH-terminated p-Si. This pre-treatment allows a uniform thin coating. In this work, the thickness is 2.6 nm. The pH response is high and close to 50 mV per pH unit.  相似文献   

6.
7.
采用机械球磨法,以磷酸二氢铝和磷酸为改性剂,制备了抗水解氮化铝粉末,并研究了改性氮化铝粉末在水基球磨过程中的稳定性。通过X射线衍射(XRD)和氮含量测定对改性前后氮化铝粉末进行了表征,并讨论了磷酸二氢铝和磷酸的加入量、球磨时间和球料质量比对改性效果的影响。结果表明:在磷酸二氢铝和磷酸的添加质量分别为氮化铝质量的1%和2.5%、球磨时间为2 h、球料质量比为3∶1的条件下,氮化铝的改性效果最佳;改性氮化铝粉末在60℃水中浸泡24 h后,其氮质量分数为32.97%,且其X射线衍射谱图中未发现氢氧化铝相,说明其抗水解能力得到显著提高;改性氮化铝粉末在水中高速球磨16 h后,其氮质量分数约为32%,氮化铝悬浮液的pH约为6,说明其在水基球磨过程中具有较好的稳定性。  相似文献   

8.
采用辊式涂布的方法在纸基材料上构建超疏水表面,并对超疏水表面的牢固性、自清洁性和疏水性能进行评价。用γ-氨丙基三乙氧基硅烷和1H,1H,2H,2H-全氟辛基三乙氧基硅烷(POTS)对微米级和纳米级两种尺寸的TiO2粒子进行疏水改性处理,然后将改性后的微/纳米TiO2涂布在纸基材料表面。采用红外光谱(FTIR)对改性后的微/纳米TiO2的化学组成进行了分析,采用扫描电镜(SEM)对涂布纸表面结构进行了表征,通过接触角、耐磨性和自洁净测试评价了涂层表面的超疏水性、牢固性和自清洁性。改性TiO2的FTIR分析显示在1000~1500cm-1之间出现多个C—F键的伸缩振动峰,表明POTS通过化学键与TiO2表面发生了结合。涂布纸表面的SEM分析可以看出,纸基材料表面上均匀分布了微米和纳米尺寸的TiO2颗粒,具备了类似荷叶表面微-纳结构的粗糙表面。涂层表面的水接触角为153°±1.5°,滚动角为3.5°±0.5°,水滴在涂层表面呈球形,极易滑落,涂层在水中浸泡7天后,接触角没有发生明显变化,表明纸张表面具备了优异的超疏水性能,且疏水稳定性较好。涂层表面经过10次循环磨损试验后,接触角仍能达到150°,滚动角为9°,表明机械摩擦没有对涂布纸表面的化学成分和粗糙结构造成明显的破坏,超疏水表面的牢固性较好。自洁净测试表明,涂布纸表面具有良好的自清洁和防污性能。该工艺过程操作简单,易于实现工业化生产,为在纸基表面构建综合性能优异的超疏水表面提供了一种新的便利途径。  相似文献   

9.
《Ceramics International》2022,48(8):10911-10920
A novel MoSi2–Al2O3 composite coating was prepared on Mo-based TZM alloy by slurry sintering method. The oxidation behavior of the coating was evaluated at 1600 °C in static air. Microstructure and phase composition of the as-prepared and oxidized coatings were characterized, and the antioxidant mechanism of the coating at high temperature was discussed. A three-layer structure was observed in the as-prepared coating, consisting of a ~2 μm thick Mo5Si3 diffusion layer, a ~65 μm thick MoSi2 inner layer and a ~36 μm thick outer layer of mixture of MoSi2 and Al2O3. After oxidation at 1600 °C for 5 h, all MoSi2 phases were completely converted to intermediate silicide Mo5Si3 by solid-state diffusion, and the formed Mo5Si3 phase would be transformed into Mo3Si phase with further extending the oxidation time. Furthermore, a dense oxide layer of SiO2-mullite was formed on the specimen surface, which can effectively protect the material to further oxidation. The MoSi2–Al2O3 coating could protect the substrate effectively at 1600 °C for 20 h without failure. The enhanced oxidation resistance of MoSi2–Al2O3 coating is due to the formation of multi-layer structure containing a SiO2-mullite composite oxide outer layer with high thermal stability and low oxygen permeability.  相似文献   

10.
In order to improve the interfacial adhesion between aramid fiber (AF) and rubber matrix, a simple and facile method of aramid nanofiber (ANF) coating is demonstrated in this article. Tannic acid (TA) and polyethyleneimine (PEI) are polymerized in an alkaline solution to form a thin TA/PEI (TP) layer that is deposited on the surface of AF to introduce functional groups such as hydroxyl and amino groups. Then, the ANF coating is utilized to construct nanostructures on the surface of AF to improve the interfacial adhesion between the fiber and the rubber. Through hydrogen bonding and/or π-π stacking between the TP layer and the ANF, the ANF coating is firmly attached to the surface of AF. Compared with the untreated fiber, the interfacial adhesion of AF coated with ANF after 1, 3, 5, 7, 9 deposition cycles is increased by 27.8%, 29.1%, 31.5%, 43.1%, and 30.3%, and the mechanical properties of the fibers remain almost unchanged. This method shows its advantages of simple, facile, and time-effective, which is of great significance for industrial applications.  相似文献   

11.
Nano polyurethane (Nano PU) was used for the fabrication of multilayer nanocomposite film deposition on wool fabrics by electrostatic self-assembly to improve the anti-felting properties. Oppositely charged cationic poly (diallyldimethylammonium chloride) (PDDA) and anionic Nano PU were alternately deposited on the surface of wool fabrics. 8, 12 and 16 multilayer films of PDDA/Nano PU were deposited on the wool fabric surfaces using a padder. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR) and Scanning Electron Microscopy (SEM-EDX) were used to verify the presence of deposit nanolayers. Breaking strength, whiteness and yellowness value analysis was performed on the fabrics before and after the treatment with Nano PU by the electrostatic self-assembly method. The build-up of the multilayer films and the level of colour strength (K/S) achieved are discussed after the acid dyeing process. To examine the anti-felting properties of the multilayered fabrics, the fabric shrinkage after washing was determined.  相似文献   

12.
《Ceramics International》2017,43(8):5968-5973
A dicalcium phosphate dehydrate (DCPD) coating was successfully fabricated on carbon fiber with in-situ grown graphene (IGN) interlayer. The obtained coating was analyzed using XRD, SEM, XPS, Raman, TEM and Thermo-gravimetric analysis(TGA). The in-vitro bioactivity of the obtained coating was investigated by simulated body fluid (SBF) immersion test. The results showed that the IGN interlayer grew homogenously on the carbon fiber with a wavy shape. The IGN interlayer was 40–90 nm in length and less than 10 nm in thickness. The DCPD exhibited a flake shape with a size of 10–50 nm. The IGN could bond with the DCPD tightly and form a uniform distribution within the DCPD coating. TGA test revealed that the carbon fiber with IGN interlayer was more effective for DCPD attachment and deposition than pure carbon fiber. The SBF tests showed that the DCPD coating could induce the formation of a cloud shaped apatite layer. The DCPD coated carbon fiber with IGN interlayer would be possible for potential application in tissue engineering.  相似文献   

13.
表面包覆Al(OH)3改性石墨的研究   总被引:5,自引:2,他引:5  
采用异相成核法在天然鳞片石墨水悬浮液中 ,使硫酸铝水解 ,在石墨表面包覆一层Al(OH) 3对石墨进行表面改性处理。介绍了包覆条件对石墨表面改性的影响 ,对改性后的石墨进行了形貌观察、接触角测定、差热 -热重分析。研究结果表明 :在适当的条件下 ,可在石墨表面形成Al(OH) 3包覆层 ,pH值为 4 .0时 ,包覆效果最好 ;包覆后石墨的抗氧化性及对水的润湿性均有所提高  相似文献   

14.
Cellulose nanofibers (CNFs) have many useful properties, including high strength and low thermal expansion, and are also environmentally friendly, readily renewable, safe, and biodegradable. The focus of this study was the development of lightweight thermoplastic polymer composites with good mechanical properties based on the incorporation of CNFs that have undergone surface pretreatment with a cationic reagent. The polyamide (PA12) was mixed with surface‐treated CNFs using a twin screw extruder and the resulting pellets were injection molded. The Izod impact strength without notch of CNF‐based composites exceeded that of composites incorporating organophilic montmorillonite (OMMT), a representative nanocomposite material. When the Izod impact test without notch, the impact hammer was stopped by the specimen with incorporation of surface treated CNF. Furthermore, the bending modulus and strength were equal to or greater than that of OMMT composites. The heat distortion temperature was improved as 33°C from neat PA12, and moreover improved as 29°C from OMMT composites. Cationic pretreatment of the CNF surfaces was found to increase the dispersion of the fibers and also to greatly improve the mechanical and thermal properties of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40920.  相似文献   

15.
As an environmentally friendly biomacromolecular material, microcrystalline cellulose (MCC) enhances the performance of natural rubber latex (NRL) composites. However, MCC has strong polarity, which weakens the interfacial interaction between MCC and the non-polar NRL matrix and reduces the reinforcing performance due to the many hydroxyl groups on its surface. In this paper, the ionic liquid (IL) modified MCC/IL material was prepared, and AIR-FTIR, x-ray diffraction, and XPS photoelectron spectroscopy were performed to detect it from the perspective of environmental protection. And natural latex/microcrystalline cellulose/ionic liquid (NRL/MCC/IL) composites with excellent properties were prepared by latex blending. The activation energy, vulcanization characteristics, basic mechanical properties, dynamic mechanical properties, and filler-rubber interfacial interactions of NRL/MCC/IL composites were investigated. The results showed that the vulcanization rate constant of NRL/MCC/IL composites increase, the activation energy decreases and the mechanical properties were significantly improved. At the same time, the matrix interface interaction of composites was quantitatively calculated using Ayala parameters. The results showed that the interfacial interaction force of the composite was stronger after an appropriate amount of IL pretreatment. The whole process is not only conformed to the concept of green development, but also broadens the application of MCC in rubber materials.  相似文献   

16.
The effect of surface modification of various wood fibers [e.g. woodflour and chemithermomechanical pulp (CTMP) of hardwood aspen, and woodflour of softwood spruce] by precoating with only maleic anhydride (MA) and/or poly[methylene (polyphenyl isocyanate)] (PMPPIC) in the presence of benzoyl peroxide (BPO) on the mechanical performance of modified fiber-filled polystyrene (PS 201 and PS 525) composites has been studied. The effects of the concentration of fiber, MA, PMPPIC, and BPO on the mechanical properties of the composites have also been evaluated. As opposed to unmodified fiber-filled composites, most of the mechanical properties of the modified fiber-filled composites increased with an increase in the concentration of BPO, MA, and/or PMPPIC up to a certain limit, and then either decreased or levelled off. The properties improved even more when both MA and PMPPIC were used as compared with the use of only one of them. The optimum concentrations of BPO, MA, PMPPIC, and fiber vary according to the wood species, the nature of the fiber, and the type of polystyrene. Compared with woodflour, CTMP is believed to be by far the best as far as the mechanical properties of the modified fiber-filled composites are concerned.  相似文献   

17.
Aramid fibers have excellent mechanical properties as the main reinforcing filler in high-performance composites. However, the adhesion properties between fibers and most polymer matrices were poor. In this study, aramid fiber (AF) was modified by KH550 through surface coating based on the treatment with CaCl2 solution. The new surface treated with complexing agents could act as an active platform for secondary reactions for further modification. The surface morphology and composition of the treated aramid fibers were tested by scanning electron spectroscopy and X-ray photoelectron spectroscopy, the interlaminar shear strength and the tensile strength of aramid fiber-reinforced polymer (AFRP) of were evaluated. The results showed that the silane coupling agent KH550 was successfully grafted onto the surface of aramid fibers after treatment with CaCl2. Interlayer shear strength is greatly improved and the tensile strength of AFRP through further grafting with KH550 on the surface treated with CaCl2 was improved by 48.7%, compared with untreated aramid fiber. In the current scenario, this study is of immense importance because it validates the possibility of secondary modification after fiber complexation modification and useful modification methods, and provides a new direction for the modification of AF.  相似文献   

18.
The low affinity between hydrophilic cellulose fibers and hydrophobic matrices leads to poor interfacial bonding, reducing the mechanical performances of natural cellulose fiber-reinforced composites. This study illustrates plasma-induced addition polymerization of propylene to create a hydrophobic surface on ramie fibers for enhancing their bonding with polypropylene (PP). Plasma treatment with propane is applied for comparison. The advancing contact angles of the plasma-treated ramie fibers are raised from 66.3° to 106.1° and the interfacial shear strengths with PP are enhanced up to 36.4%, likely resulted from the increase in fiber surface roughness observed under a scanning electron microscope and the introduction of plasma-grafted PP and alkyl groups on fibers surfaces proven by X-ray photoelectron spectroscopy. It is also revealed that plasma treatment with propylene is highly effective in increasing surface carbon content (from 68.3% to 82.4% in 0.5 min) and more efficient than the treatment with propane, though both plasma treatments show substantial modification efficacies to the fiber surfaces. The treatment duration affects surface roughness more than surface chemical composition, and the optimized treatment time is around 1 min. The modification method developed in this research has the potential to be used for surface modification of fibers for many applications.  相似文献   

19.
Carbon fibre reinforced ultra-high temperature ceramic (UHTC) matrix composites were fabricated coupling water-based powder slurry infiltration, Polymer Infiltration and Pyrolysis (PIP) and Hot Pressing (HP) techniques. This study aims to identify the best sequence of consolidation techniques to better integrate the carbon fibre cloths into an ultra-refractory sintered ceramic matrix of ZrB2-SiC. Infiltrated preforms with UHTC powder slurry were densified via: a) a pre-sintering step by HP followed by two PIP cycles with polycarbosilane, and vice versa, b) two PIP cycles followed by a cycle of HP. Flexural strengths at room temperature and at 1500 °C (167 MPa and 592 MPa, respectively) were found to be significantly higher for composites obtained by the second route, suggesting that sintering of polymer-derived SiC during HP improves the structural properties of Cf/ZrB2-SiC composites. This work presents an effective method for UHTCMC manufacturing in a shorter time than traditional PIP process.  相似文献   

20.
《Ceramics International》2020,46(8):11819-11827
In this study, an alumina/mullite coating was synthesized on the surface of fused silica powders to form an alumina/mullite-silica core-shell structure. The effects of the alumina/mullite coating on the cristobalite crystallization, thermal properties, and leachability of the silica-based ceramic cores were investigated using the simulated casting process. The X-ray diffraction results indicated that the crystallization of cristobalite was significant at the simulated casting temperature of approximately 1400 °C. An increase in the cristobalite content during this stage resulted in a large thermal expansion because of its higher coefficient of thermal expansion compared with that for fused silica. The addition of optimum amounts of the alumina/mullite powders resulted in an increase in the initial shrinkage temperature and a decrease in the shrinkage of the specimens. When the coating powders were added at 43 wt%, the initial shrinkage temperature increased from 1092 °C to 1200 °C and the shrinkage decreased sharply. Leaching tests showed that the silica-based ceramic cores were removed in the form of stripped layers. The washing and shaking process accelerated the disintegration of the ceramic core and improved its leachability.  相似文献   

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