Ultralight Silicon Nitride Ceramic Foams from Foams Stabilized by Partially Hydrophobic Particles

Ultralight Si₃N₄ ceramic foams have been successfully prepared through particle‐stabilized foams method, which is based on the adsorption of in situ hydrophobized Si₃N₄ particles to the liquid/air interface of the foams. Here, we firstly used a long‐chain surfactant cetyltrimethylammonium chloride to render the Si₃N₄ particles partially hydrophobic. By tailoring the surfactant concentration and pH values of the suspensions, the wet foams were stabilized to avoid coarsening and coalescence. SEM results show that the Si₃N₄ ceramic foams possess single strut walls with elongated β‐Si₃N₄ grains interlocking with each other, and their pores are uniform with an average pore size of 95 μm. The obtained ceramic foams maintain compressive strength of 1.34 ± 0.13 MPa with porosity of 92.0%, when the suspension contains 3 mmol/L surfactant at the pH of 11.0.     

Ceramic/Polyaniline Composite Porous Membranes

Ceramic/polyaniline composite porous membranes are successfully made by diffusing ammonium peroxydisulfate and aniline into inorganic membrane disks. The ceramic disks are fabricated by mixing CMC, water, kaolin and alumina followed by the processes of drying, milling, sieving, pressing at 4000 pounds, and firing. The pore size of the disk is approximately 1 m.When the concentration of the oxidant is 0.25 M and that of the monomer is 1 M, the incorporation of polyaniline into the ceramic disks levels off after about 40 hours. The maximum incorporation percentage is approximately 4.86 wt% (0.18 g of polymer/3.7 g of disk). Characterizations of the ceramic disk and its composites include N2-flow tests, solubility tests, BET, SEM, OM and acid diffusion studies. Nitrogen-flow tests indicate that the incorporated polyaniline is structurally unstable. However, after applying N2 gas of 23 psig for about 40 min, no further degradation is observed in these composite membranes even under 40 psig of N2 gas. BET shows that the surface area of the composite is greater than that of the ceramic disk. SEM reveals that polyaniline is grown on the surface of the pores of the ceramic disks. Time constants, corresponding to the time when the pH value reaches 36.8% of the initial value, are estimated from the results of acid diffusion studies. The magnitude of the time constant is in the following order: ceramic/Peani base > ceramic/Peani salt > ceramic/Pani base > ceramic/Pani salt > plain ceramic.     

Processable Thermally Conductive Polyurethane Composite Fibers

The demand for wearable electronics has resulted in an increasing interest in the development of functional fibers, with a specific focus upon the development of electrically conductive fibers incorporable into garments. However, the production of thermally conductive fibers for heat dissipation has been largely neglected. Owing to the very rapid development of miniaturized wearable electronics, there is an increasing need for the development of thermally conductive fibers as heat sinks and thermal management processes. In this study, thermally conductive but electrically insulating boron nitride nanopowder (BNNP) fillers are used to effectively enhance the thermal conductivity and mechanical properties of elastomeric polyurethane fibers. Thermal conductivity enhancement of more than 160% is achieved at very low loadings of BNNP (less than 5 wt%) with an improvement in the mechanical properties of the unmodified fiber. These thermally conductive fibers are also incorporated into 3D textile structures as a proof of processability.     

不同粒径氮化硼填充环氧树脂/玻璃纤维绝缘导热复合材料的研究

以聚砜改性环氧树脂为基体,通过高温模压制备了环氧树脂/玻璃纤维/氮化硼复合材料,研究了不同粒径及不同氮化硼导热粒子用量对复合材料导热性能、力学性能和电性能的影响。结果表明,大粒径粒子有利于复合材料力学性能的提高,小粒径有利于导热性能的提高;随着氮化硼用量的增加,复合材料的导热性能升高,力学性能呈现先增后降趋势,当氮化硼用量为10%(质量分数,下同)时,复合材料的冲击强度和弯曲强度均达到最佳,当氮化硼用量为20%时,复合材料仍保持较好的电性能。     

氧化铝层状自润滑复合陶瓷的宏/微观结构设计及性能调控

自润滑复合陶瓷是极端环境服役运动部件的最佳候选材料之一,其中仿生层状结 构自润滑复合陶瓷由于具有优异的综合性能而倍受人们的青睐。基于宏/微观结构设计是实现其 结构/润滑功能一体化和可靠性提升的关键。本文结合作者所在课题组的相关工作,综述了层状 结构几何参数和界面微结构、参数与组分对氧化铝层状自润滑复合陶瓷力学性能、摩擦学性能 和服役可靠性的影响规律及作用机制,并提出了层状自润滑复合陶瓷的结构与界面优化设计准 则,以期指导自润滑复合陶瓷性能提升和推动其在高技术装备中的应用。     

PF泡沫塑料对PF/EPS复合泡沫塑料性能的影响

研究出一种具有较好稳定性、保温性能、力学性能和阻燃性能的酚醛树脂(PF)/可发性聚苯乙烯(EPS)复合泡沫塑料。在PF泡沫塑料颗粒基体中加入EPS发泡颗粒,充分混合固化,使PF泡沫塑料颗粒与EPS发泡颗粒紧密结合,EPS发泡颗粒被PF泡沫塑料颗粒包围并相互隔离,再用模具发泡成型得到该复合泡沫塑料。实验结果表明,PF的含量越高,稳定性、力学性能和阻燃性能越好,保温性能呈现先升高后下降的趋势,当PF的含量为80%时,PF/EPS复合泡沫塑料的表观密度为38.4 kg/m3,热导率为0.024 W/(m·K),弯曲强度为0.134 k Pa,压缩强度为323 k Pa,极限氧指数为47.9%,烟密度等级小于15,热释放速率峰值小于250 k W/m2,综合性能最好。     

无机盐/石英基复合相变储能材料多孔陶瓷基体的制备

以石英为骨料,钾长石为高温粘结剂,木炭为造孔剂制备无机盐/石英基复合相变储能材料用的微米孔石英多孔陶瓷基体,采用正交实验法系统研究了骨料颗粒粒度、造孔剂粒度、造孔剂含量、高温粘结剂含量及烧成温度对石英多孔陶瓷的显气孔率和抗折强度的影响.研究结果表明,影响石英多孔陶瓷抗折强度的最主要因素是长石含量,其次是骨料粒度和造孔剂粒度;影响石英多孔陶瓷显气孔率的主要因素是造孔剂含量.制备微米孔石英多孔陶瓷的优化配方和工艺是:石英、木炭和长石均过325目筛,三者质量比为7:2:1,烧成温度为1270f,保温时间为1h.该陶瓷具有以下优良的性能:显气孔率为55.12％,体积密度为1.14 g,/cm3,抗折强度为3.14 MPa,抗压强度为7.12 MPa,平均孔径为13.87 μm且孔径分布范围较窄,96％的气孔孔径在9～21 μm之间.     

Compressive response of PMMA microcellular foams at low and high strain rates

Microcellular foams are widely applied in various applications in both civil and military applications for barriers and energy absorption materials. Poly(methyl methacrylate) microcellular foams were fabricated via supercritical foaming method. Field emission scanning electron microscopy, differential scanning calorimetry, and mechanical test machine were used to visualize the foam structure and test the quasi‐static compression properties. Moreover, Split Hopkinson Bar (SHPB) setups were adopted to explore the dynamic compression properties. The experimental results show that the microcellular foams have homogeneous cell size distribution and exhibit superior compressive behavior at both quasi‐static and high strain rates. The mechanical properties depend on both foam density and strain rate. Strain rate effects are clearly observed. At quasi‐static strain rate and 7500 S^?1 regime, cell wall bucking and folding are the main failure mechanism. However, at high strain rate regime, softening phenomenon is observed. By roughly calculating the energy absorbed and the temperature rise, the temperature of the foams will rise up to as high as 130 °C after conducting high strain rate compression, and it is postulated that the generated heat will destroy the cell structure of the foams. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46044.     

玻璃短纤维-热塑性聚氨酯复合材料的性能研究

研究了玻璃短纤维热塑性聚氨酯复合材料中短纤维用量对应力应变曲线、拉伸强度和撕裂强度的影响。试验结果表明,随着复合材料中短纤维用量的增大,复合材料的刚性明显提高、应力应变曲线从典型的粘弹性曲线变为弹性特性曲线、拉伸强度增大（短纤维用量超过１１份）,横向撕裂强度远低于纵向撕裂强度。     

热塑性木塑复合材料研究进展

热塑性木塑复合材料（WPC）是一种兼有木材的力学性能和热塑性塑料易加工的新型材料。阐述木塑复合材料国内外最新研究进展和应用前景。指出热塑性木塑复合材料作为一种新型环保材料,具有广阔的应用前景。     

Effect of cellular uniformity on the necking propagation of foam injection Molded PP/HDPE blend parts

Necking propagation (NP) is an important phenomenon that is facilitated by the superductility of many materials, although necking is often considered to be a type of unstable and heterogeneous deformation under tensile loading. In this study, the NP of samples produced with injection molding of polypropylene (PP) and high-density polyethylene (HDPE) blends with or without a blowing agent was investigated by standard tensile testing, and the foam morphology and cellular structure were characterized with scanning electron microscopy. It was found that the foam parts fabricated with the PP/HDPE blends had the ability to be superductile under a low tensile test speed, which was attributed to the necking spreading throughout the tested gauge section stably and reliably. However, the NP of the foam PP/HDPE blend samples strongly depended on the distribution of the cellular foam. To investigate the relationship between the cellular structure and NP, a design of experiment approach based on the Taguchi method was used to fabricate many samples with different foam structures. The tensile test results of these samples suggested that the cellular uniformity, which was determined based on the statistical results of the fracture surface morphology, played an important role in the NP. The results suggested that there is a close relationship between the NP and the cellular uniformity. Using nonlinear fitting, it was straightforward to obtain a model between the NP length and cellular uniformity index for PP/HDPE molded foam parts.     

热塑性复合材料研究进展

综述热塑性复合材料的优点、国内外热塑性复合材料的概况、国内玻纤增强聚丙烯(PP)、增强尼龙(PA)、玻纤增强聚对苯二甲酸丁二酯(PBT)等热塑性复合材料研究情况、热塑性复合材料在汽车工业、航空航天、军事领域等的应用情况,并预测了应用前景。     

Thermoplastic Soy Protein Nanocomposites Reinforced by Carbon Nanotubes

MWNTs of various sizes were compounded into SPI matrix by solution mixing and then compression‐molded into nanocomposite sheets, which were characterized by XRD, SEM, TEM, and tensile and water uptake testing. The resultant nanocomposites showed improved mechanical performance and higher water resistance depending on MWNT size and content. This work details a strategy to achieve improved performance, especially in terms of mechanical properties, using MWNTs of various sizes to regulate the entanglement and penetration between SPI and MWNTs.

     

聚合物/新型导热填料复合电介质的研究进展

综述了非常规新型导热粒子如纳米金刚石、碳化物、铁电陶瓷及其他无机功能粒子及其填充聚合物电介质的最新研究进展,重点探讨了新型导热粒子的含量、表面改性、加工方式等对聚合物复合材料的导热及介电性能的影响。介绍和分析了基于有机分子晶体为连续声子传递通路改性聚合物导热性能的研究及机理;在基体树脂内利用无机导热粒子及有机分子晶体可构筑连续的声子导热通路,从而达到降低界面热阻、提高体系热导率的目的。相比传统导热粒子,新型导热粒子在提高绝缘聚合物热导率的同时,还赋予体系其他物理性能如磁性、优良介电性能及储能等性能。     

Effect of Pluronic F127 on the 3D pore morphology of poly(N-isopropylacrylamide-co-acrylic acid) hydrogels and their nitric oxide release from S-nitrosoglutathione

Changing the pore morphology of hydrogels can be an effective strategy to modulate their drug release profiles. Herein, Pluronic F127 was used to change the three-dimensional pore morphology of crosslinked poly(N-isopropylacrylamide-co-acrylic acid) (P[NIPAm-co-AAc]) hydrogels. F127 reduced the pore diameters from 20 ± 4 to 2.9 ± 0.4 μm and from 11 ± 1 to 1.4 ± 0.4 μm in hydrogels synthesized at 8 and 30°C, respectively. Small-angle X-ray scattering indicates that the segregation of the F127 during the polymerization process induces F127 phase transitions from unimers (at 8°C) or cubic-packed micelles (at 30°C) to a lamellar structure. P(NIPAm-co-AAc) hydrogels charged with S-nitrosoglutathione (GSNO), released nitric oxide (NO) spontaneously during hydration. The decrease in the pore diameter led to a twofold to threefold increase in the rate of water absorption and a fourfold to sixfold increase in the rate of NO release of the hydrogels. F127 can be used to change the pore morphology of P(NIPAm-co-AAc) hydrogels, with concomitant changes in their rate of hydration and NO release from GSNO, opening a new perspective for their use in topical NO delivery.     

氯化锌活化法制备多孔炭陶复合吸附材料

以氯化锌浸渍的木屑为原料,黏土为粘结剂,制备炭陶复合吸附材料。讨论了炭化温度和保温时间对其吸附性能的影响,并对其孔隙结构进行了表征。结果表明,随温度和保温时间的增加,炭陶复合吸附材料的碘吸附值和亚甲基蓝吸附值呈先上升后下降的趋势;木屑受到活化作用形成活性炭而发生收缩,在活性炭和陶土之间形成空隙,有利于形成孔隙结构发达的炭陶复合吸附材料。在温度500℃、保温时间1 h的较佳工艺条件下,制得炭陶复合吸附材料的比表面积为809.5 m²/g,总孔容积为0.298 cm³/g,中孔容积为0.185 cm³/g,微孔容积为0.113 cm³/g,炭陶的含炭量为60.7%,碘吸附值为680.5 mg/g,亚甲基蓝吸附值为165.0 mg/g。     

热塑性淀粉／反应性聚酰胺复合膜的力学性能研究

为了提高淀粉基复合膜的干/湿态力学性能,将反应性聚酰胺(RPA)、烷基烯酮二聚体(AKD)与热塑性玉米淀粉(St)复合后采用浇铸法制备新型疏水化复合膜。研究了RPA、AKD及丙三醇(GL)对复合膜力学性能的影响。结果表明:反应性聚酰胺、烷基烯酮二聚体能够明显改善淀粉基复合膜的力学性能,尤其是湿态复合膜的拉伸强度。复合膜的较佳组成为St:GL:RPA:AKD=10．0:(3．0-4．0):(4．0-5．0):(0．5-0．7);复合膜的干态拉伸强度和断裂伸长率分别可以达到12．10MPa和45．70％以上,湿态拉伸强度和断裂伸长率则分别可以达到5．40MPa和30．0％以上。     

AlN—BN复合陶瓷的研究

本文用热压法烧结制备出ＡｌＮ—ＢＮ复合陶瓷，讨论了组成及烧结条件对ＡｌＮ—ＢＮ复合陶瓷性能及显微结构的影响。通过优化组成，使ＡｌＮ—ＢＮ复合陶瓷垂直于加压方向的导热率最大达１０３Ｗ／ｍ·Ｋ。ＡｌＮ—ＢＮ复合陶瓷的导热率和显微结构各向异性较显著。     

环氧树脂/氧化锌晶须/氮化硼导热绝缘复合材料的研究

以环氧树(脂EP)为基体,分别以氧化锌晶(须ZnOw)和ZnOw/氮化硼(BN)混合物为导热填料,制备了EP导热绝缘复合材料。研究了填料含量对复合材料导热性能、电绝缘性能及力学性能的影响,并利用扫描电镜对复合材料的断面形貌进行了观察。结果表明:随着导热填料含量的增大,复合材料的导热系数和介电常数增大,体积电阻率下降,而拉伸强度呈先增大后减小的趋势;在填料含量相同的情况下,EP/ZnOw/BN复合材料比EP/ZnOw复合材料具有更好的导热性能;当填料体积分数为15%时,EP/ZnOw/BN复合材料的热导率为1.06W/(mK)而,EP/ZnOw复合材料的热导率仅为0.98W/(mK)。