微波烧结多孔β-TCP/HA双相生物陶瓷的性能

用微波烧结法制备出多孔β-TCP/HA双相生物陶瓷,研究了烧结温度、烧结时间及加热速度对生物陶瓷性能的影响.优化烧结工艺后,得到了平均晶粒尺寸约400 nm,气孔率约48%,强度为1.10 MPa的多孔β-TCP/HA双相陶瓷.用微波烧结方法可以制备出良好的多孔β-TCP/HA双相生物陶瓷,其线收缩率和抗压强度随着烧结温度的升高和烧结时间的延长而增大.与常规马弗炉烧结相比,在多孔β-TCP/HA双相生物陶瓷的线收缩率和抗压强度相同的情况下,微波烧结温度降低了大约100℃,提高了烧结效率,降低了能耗.微波烧结钙磷生物陶瓷具有更好的生物活性.     

多孔硅酸钙生物陶瓷的制备及体外活性和降解性研究

以聚乙二醇为造孔剂,制备了多孔硅酸钙生物陶瓷.应用本文提供的方法,可制得孔连通性好、气孔率53.7%-73.6%、抗压强度4.9-48.5MPa、大孔孔径200-500μm的多孔陶瓷.研究表明,多孔硅酸钙生物陶瓷的力学强度随造孔剂含量的增加而明显降低,而气孔率则相反.应用模拟体液浸泡实验研究了多孔陶瓷的体外生物活性和降解性.研究表明,样品在模拟体液中浸泡1天表面就全部被碳酸代羟基磷灰石层覆盖住.气孔率为63.1%的样品7天的降解率达7.14%,具有良好的降解性.研究结果显示多孔硅酸钙生物陶瓷有望作为硬组织修复支架材料用.     

光固化3D打印磷酸钙基生物陶瓷支架的研究进展

磷酸钙基生物陶瓷多孔支架是临床中实现骨缺损再生修复的常用骨移植物。光固化3D打印技术以其优异的打印精度和复杂结构成形特性能够精确地控制支架孔尺寸、孔形状、孔连通率,在制备生物陶瓷多孔支架领域展现出巨大的应用潜力。然而,利用光固化3D打印技术制备磷酸钙基生物陶瓷多孔支架仍面临亟需克服的挑战,如缺乏性能优异的磷酸钙基陶瓷打印浆料、打印及后处理工艺不成熟、制备的磷酸钙基陶瓷多孔支架的性能还有待提升。本文首先介绍了几种常用的光固化3D打印技术基本原理与特征,然后从3D打印成形工艺、力学性能、生物活性、支架结构及功能化等方面系统探讨了光固化3D打印技术在制备磷酸钙基生物陶瓷多孔支架领域的研究进展及存在的问题,最后展望了光固化3D打印磷酸钙基生物陶瓷多孔支架的发展趋势和突破点,为利用光固化3D打印技术制备成本低、综合性能优异的磷酸钙基生物陶瓷多孔支架提供参考。     

烧结温度对包混/复合添加工艺制备多孔SiC陶瓷性能的影响

采用包混工艺合成了核壳结构的先驱体粉体,并引入一定量Al2O3、SiO2和Y2O3复合添加剂,通过成型、炭化和烧结工艺制备了多孔碳化硅陶瓷;分析了样品的物相、表面形貌、孔隙率、热导率、热膨胀系数、抗弯强度和抗热震性能。结果表明,在较低的烧结温度下制得了多孔碳化硅陶瓷,在1650℃烧结的多孔碳化硅陶瓷综合性能较好。     

自蔓延高温合成氮化硅多孔陶瓷的研究进展

多孔氮化硅陶瓷兼具有高气孔率和陶瓷的优异性能, 在吸声减震、过滤等领域具有非常广泛的应用。然而, 目前常规的制备方法如气压/常压烧结、反应烧结-重烧结以及碳热还原烧结存在烧结时间长、能耗高、设备要求高等不足, 导致多孔Si₃N₄陶瓷的制备成本居高不下。因此, 探索新的快速、低成本的制备方法具有重要意义。近年来, 采用自蔓延高温合成法直接制备多孔氮化硅陶瓷展现出巨大潜力, 其可以利用Si粉氮化的剧烈放热同时完成多孔氮化硅陶瓷的烧结。本文综述了自蔓延反应的引发以及所制备多孔氮化硅陶瓷的微观形貌、力学性能和可靠性。通过组分设计和工艺优化, 可以制备得到氮化完全、晶粒发育良好、力学性能与可靠性优异的多孔氮化硅陶瓷。此外还综述了自蔓延合成多孔Si₃N₄陶瓷晶界相性质与高温力学性能之间的关系, 最后展望了自蔓延高温合成多孔Si₃N₄陶瓷的发展方向。     

先驱体转化法制备多孔陶瓷的发展现状

多孔陶瓷材料因其优异的性能在各种领域的应用越来越广泛,其制备方法也不断的发展.先驱体转化法制备多孔陶瓷是20世纪末才出现的一种新型工艺,它具有烧结温度低、成型工艺简单、所得制品强度高等优点,引起了科学技术界的广泛兴趣.根据所得多孔陶瓷的形态,先驱体转化法制备多孔陶瓷大致可分为两类:制备本征结构的多孔陶瓷,制备泡沫陶瓷.本文介绍了先驱体转化制备这两类多孔陶瓷的工艺、结构和性能的研究现状,以及其存在的急需解决的问题.     

硅溶胶添加对氧化铝多孔陶瓷烧结性能的影响

以煅烧α-Al2 O3粉末为原料,硅溶胶为高温结合剂,羧甲基纤维素钠为成型黏结剂,通过混料、困料、模压成型、高温烧结等工序制备氧化铝多孔陶瓷,利用SEM和XRD对多孔陶瓷微观形貌和晶体结构进行测试,并对多孔陶瓷的线收缩率、体积密度、显气孔率和抗弯强度进行表征,系统地研究硅溶胶添加对氧化铝多孔陶瓷高温烧结特性的影响.结果表明:低温下硅溶胶的热解产物石英型SiO2将氧化铝颗粒黏结起来,形成物理黏结,能提高多孔陶瓷的力学性能;烧结温度达1500℃时,SiO2开始与氧化铝反应形成莫来石,莫来石结合相的生成使得氧化铝多孔陶瓷趋于致密,力学性能优异,抗弯强度可达(105.5±8.0)MPa;随烧结温度的升高莫来石生成量增多,导致氧化铝多孔陶瓷的体积膨胀,进而使得孔隙率增大,力学性能降低.烧结温度介于1400～1500℃之间时,可以得到微观结构合理、力学性能优异、孔隙率适中的氧化铝多孔陶瓷.     

烧成工艺制度对石英砂基多孔陶瓷材料孔结构及性能的影响

以节约粘土资源及开发新型节能建筑材料为目的,利用长江沿岸低品位石英砂开发研制多孔陶瓷.研究了烧成工艺对石英砂基多孔陶瓷孔结构及性能的影响,为新型隔热保温材料的开发提供了工艺参考依据.研究结果表明,利用长江沿岸低品位石英砂成功地研制出多孔陶瓷,其密度随烧结温度的升高或保温时间的延长而增大,气孔率则随烧结温度的升高或保温时间的延长而降低.从能耗、成本与性能3方面考虑,石英砂基多孔陶瓷较合理的制备工艺参数为烧结温度1100℃、保温时间60min.     

陶瓷中空纤维透氧膜的制备与性能

应用相转化法制备了La_0.6Sr_0.4Co_0.2Fe_0.8O_3-α(LSCF)氧离子-电子混合传导陶瓷中空纤维膜, 该陶瓷中空纤维膜具有由多孔层和致密层组成的非对称结构. 经 1300℃的4h烧结后, 可得到致密的LSCF陶瓷中空纤维膜. 烧结后, LSCF粒度变大而其钙钛矿型晶相结构没有发生变化. LSCF中空纤维膜的透氧速率大大高于一般管式膜的氧透量.     

多孔CaO-P2O5-SiO2系生物陶瓷的原位合成

本文采用原位合成技术制备了多孔CaO-P2O5-SiO2系生物陶瓷.研究表明:240°C水热合成8h、1020°C下烧结2h,主晶相为β-TCP,次晶相为HA,此外,尚含有SiO2;并有1.3～1.7mm大孔,在大孔内表面有大量的0.6～2.8μ微孔,在大孔孔壁内部有大量的1.0～3.0μ微孔,从而形成大孔通过0.6～3.0μ微孔相互贯通的三维网络状孔结构.二次水热处理工艺后,多孔生物陶瓷中的颗粒状β-TCP向针状缺钙型HA转变.     

Artificially controlling of inner structure to porous hydroxyapatite ceramic by using solidified coated fibers

Porous hydroxyapatite (HA) ceramic was fabricated by 3D fiber network. These fibers as channel underprops were treated by surface coating with acidic macromolecule glue. The solidified coated fibers in ceramic block could form run-through channels and also etch stripes on channel walls for cell attachment. The channels formed in sintering process by fibers volatilization may be directed artificially according to beforehand design of structure for ceramic block. The results showed that the pore characteristics and the inner structure of the sample made from this technique have settled for essential requests of porous bioceramic. The channels in sintered scaffold shown in SEM (scanning electron microscopy) micrographs have directional connection, equal distribution, intact configuration and existence of thin stripes on inner walls. All of these characteristics have met requests for tissue cell developing, transplanting and attaching. The samples have appropriate interconnectivity and reasonable structure with equable pore-arranging and uniform size of pore. XRD (X-ray diffraction) patterns of sample indicated no major change of the crystalline structure.     

Microstructure and scintillation characteristics of BaF2 ceramics

This paper examines how the transformation of BaF₂ from a single-crystalline to polycrystalline state as a result of uniaxial hot-forming influences its properties. With increasing strain, the microstructure of the material changes from a nonuniform polycrystalline one, with a block size of about 1 mm, to a classic ceramic structure made up of grains in which dislocations form walls, resulting in a subgrain structure. The best mechanical characteristics are offered by the ceramic produced at a strain on the order of 700%. The intensity of the fast X-ray luminescence component (band at 220 nm) is independent of strain, whereas that of the slow component (band at 310 nm) decreases with increasing strain.     

The yarn size dependence of tensile and in-plane shear properties of three-dimensional needled textile reinforced ceramic matrix composites

The yarn size scaling of tensile and in-plane shear properties is examined for three-dimensional needled textile reinforced ceramic matrix composites (3DN CMC) fabricated by chemical vapor infiltration. The results showed that large yarn size would cause the nonwoven yarn of 3DN CMC crimp and lower composite density, resulting in decrease of tensile and in-plane shear properties. The “modified lamina modeling” was presented to predict the tensile and shear elastic moduli of 3DN CMC with different yarn size. Other two methods were also proposed to evaluate the tensile and in-plane shear strengths of 3DN CMC with different yarn size, respectively. All predicted results showed consistent well with the experimental results.     

Woven fabric reinforcement of cement matrix

The performance of woven fabric reinforced cement was studied to resolve the influence of the structure of the fabric on its reinforcing efficiency. Special fabrics were produced for this study in which the longitudinal (warp) yarn density was kept constant and the perpendicular (fill) yarn density was varied, in the range of 0 to 22 yarns per centimeter. Specimens for flexural and pull out testing were produced from the fabrics and crimped yarns untied from the fabric. Scanning electron microscope tests were carried out to resolve the microstructure of the composite, in particular at the yarn-matrix interface. The results point to three main conclusions: (1) Woven fabric structure improved the bonding capacity as compared to polyethylene monofilament fibers and cement matrix. (2) The crimped structure of the yarns in the fabric plays an important role in this improvement of the bond, providing mechanical anchoring between the woven fabric and the cement matrix. (3) There is an optimal density of fill yarn in the fabric, which causes the higher flexural strength within the tested densities and matrix formulations. This optimum is achieved in the fabric with five fill yarns per centimeter, and it may be accounted for by the fact that at higher density the matrix does not penetrate efficiently into the spaces in the fabric.     

Titelbild: Mauerwerk 6/2017

The office block from Andreas Heupel Architekten in the old city harbour of Münster, is a seven‐storey, 26 m high hybrid timber building. For the facade, the architects chose green glazed ceramic facade tiles with a fine horizontal relief structure, which were individually produced after close discussions with the manufacturer the company Moeding and change according to daylight and weather. (photo: Anke Müllerklein)     

Delaminationsverhalten von langfaserverstärkten thermoplastischen UD-Verbunden hergestellt aus unterschiedlichen Hybridgarnstrukturen

Characterisation of the delamination behaviour of thermoplastic UD-composites made by different hybrid yarn structures In order to determine delamination behaviour of glass-fibre-reinforced polyamid composites the compression shear test and the DCB (Double Cantilever Beam)-, SEN- and NBT-test for mode-I- and the ENF (End Notched Flexure)-test for mode II-loading were used. By these tests the energy release rate G respectively K and the R cure (crack resistance curve) have been measured which characterise the crack resistance of the material against delamination. The composites were made by different hybrid yarn structures produced by air texturing (commingled yarn: COM), side-by-side arrangement (SBS), friction spinning (FS), Kemafil (KEM)- and Schappe(SCH)-technology. The influence of different glass fibre sizings was investigated. The results demonstrate the significant influence of different hybrid yarn structures and glass fibre coatings on fracture thoughness during crack propagation along the fibre/matrix interface. The best values were obtained for composites produced on the basis of commingled yarn structure.     

蛋白发泡法制备泡沫陶瓷固化工艺研究

选用蛋清蛋白作为发泡剂, 采用蛋白发泡法制备了高孔隙率的泡沫氮化硅陶瓷. 设计了三种不同固化工艺: 常压固化、恒压固化和高压固化, 固化气压依次升高, 研究了固化气压对泡沫陶瓷开孔率、孔隙形貌和孔径分布的影响. 其中, 恒压固化制品的平均孔径和开孔率最高, 分别为210 μm和78.6%, 且孔径分布比较均匀, 常压固化次之, 高压固化制品开孔率和平均孔径最低. 常压和恒压固化制品为椭球形孔洞, 有一定的排列取向, 而高压固化制品多为规则的球形孔. 随着固化气压的升高, 制品孔壁厚度增加, 高压固化制品的孔壁厚度最高, 其压缩强度接近50 MPa.     

A numerical investigation of the influence of friction on energy absorption by a high-strength fabric subjected to ballistic impact

A finite element analysis was conducted to study the influence of friction during ballistic impact of a rigid sphere onto a square fabric panel that was firmly clamped along its four edges. Projectile-fabric friction and yarn–yarn friction were investigated. Modeling indicates that friction dramatically affects the local fabric structure at the impact region by hindering the lateral mobility of principal yarns. Reduction of lateral yarn mobility allows the projectile to load and break more yarns so that fabric possessing a high level of friction absorbs more energy than fabric with no friction. The projectile-fabric friction delays yarn breakage by distributing the maximum stress along the periphery of the projectile-fabric contact zone. The delay of yarn breakage substantially increases the fabric energy absorption during the later stages of the impact. The yarn–yarn friction hinders the relative motion between yarns and thus resists de-crimping of fabric weave tightness. It induces the fabric to fail earlier during the impact process. The overall influence of projectile-fabric friction and yarn–yarn friction cannot be calculated by simply adding their individual effects.     

Properties of cotton/T‐400 and 100% cotton plain knitted fabric made from ring spun yarn

This research studies the properties of a plain knitted fabric made from cotton/T‐400 ring core spun yarn and 100% cotton ring spun yarn. Properties of plain knitted fabric made from 100% cotton ring spun yarn were compared with one made from cotton/T‐400 (70.4C/29.6T). We focused on knitted fabric properties such as the bursting strength, elongation at break, tensile strength, air permeability as well as pilling properties. The two yarn samples were produced on the ring frame which had a special attachment for core spun yarn. Fabrics were then knitted using a circular machine, for consistence of results plain knit structure was adopted for all samples. Knitted fabric properties were then tested and results statistically analyzed. Research results show that, plain knitted fabrics made from cotton/T‐400 (70.4C/29.6T) ring core spun yarn exhibit better elongation at break, bursting strength and air permeability. Whereas the fabric made from 100% cotton showed better pilling resistance and tensile strength compared to cotton/T‐400 (70.4C/29.6T) plain knitted fabric. Results show that T‐400 filament has very significant influence on resulting fabric properties and hence can be technically manipulated to suit different fabric end use requirements.     

Finite element modelling of tow geometry in 3D woven fabrics

A finite element model of a 3D woven angle interlock fabric undergoing compaction based on the multi-element digital chain technique has been developed. The aim was to create a kinematic model to predict the internal architectural features in a commercial off-the-shelf code. A statistical analysis of yarn crimp and resin channel size was carried out on sections from the model at increasing levels of compaction and compared to laboratory-manufactured samples with the same weave style. Results show a good correlation between overall mean crimp values in the warp, weft and weaver yarns as well as reasonable accuracy in the frequency distribution of local crimp angles. The trend in resin channel size with respect to increasing levels of compaction was also good but significant discrepancies in the absolute dimensions of a resin channel were present due to limitations in controlling the yarn bundle internal interactions in the model.