A novel fabrication procedure for producing high strength hydroxyapatite ceramic scaffolds with high porosity

Hydroxyapatite (HA) scaffolds were fabricated using the space holder method with a pressureless sintering process in a systematically developed manner at different fabrication stages to increase the strength of the scaffold at high porosity. Polyvinyl alcohol (PVA) and Polymethyl methacrylate (PMMA) were used as binders and space holder agents, respectively. The physical properties of the HA scaffolds were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), linear shrinkage test, and porosity measurements. The mechanical properties of the HA scaffolds were analyzed using compressive strength measurements. The results revealed that the HA scaffold met the expected quality requirements with a compressive strength of 2.2 MPa at a porosity of 65.6% with pore sizes distributed in the range of 126–385 μm. The shrinkage of the scaffold diameter occurred by 20.27%, this diameter shrinkage predominantly to the shrinkage of the HA scaffold caused by sintering. Besides, suspect that a higher PMMA concentration causes pore size shrinkage upon sintering. The formation of pore interconnections was evidenced by SEM observations and the ‘translucent light method’ developed in this study. The results of the scaffold phase test using XRD showed that the final scaffold consisted only of the HA phase, as the PVA and PMMA phases burned out during the sintering process.     

高强度堇青石-莫来石棚板的研制

以堇青石(1～0.5、0.5～0.2、<0.088 mm)和莫来石熟料(M60,1～0.5 mm)为主要原料,加入25%(w)的由轻烧MgO粉、α-Al2O3微粉及添加剂(紫木节和KOH)组成的混合粉,按堇青石与莫来石的质量比分别为40:35、42.5:32.5和45:30配料、混练、成型后,分别在1 300、1 350和1 400℃均保温3 h条件下烧成,合成出堇青石-莫来石质棚板试样,并检测试样的常温及高温物理性能,同时进行XRD、SEM及EDS分析.结果表明:按m(堇青石):m(莫来石)=45:30配料,在1 350℃ 3 h合成的棚板材料的各项性能指标最好,其主要晶相为堇青石和莫来石,且显微结构均匀,晶间生成大量的原位堇青石和莫来石晶粒,骨料之间的"联接桥"发育良好,材料具有较高的抗折强度.     

高熔体强度聚丙烯的研制

用过氧化物引发聚丙烯(PP)交联制备高熔体强度聚丙烯(HMSPP),研究了过氧化物的用量、反应温度、螺杆转速对HMSPP性能的影响。得到的HMSPP比普通PP的熔体强度提高约3倍。用所研制的HMSPP进行发泡实验,制得泡孔结构较均匀且闭孔的发泡制品。     

Preparation of dense and high-purity SiC ceramics by pressureless solid-state-sintering

High-purity SiC materials have been used in semiconductor processes due to their excellent properties. However, they are difficult to densify without sintering aids. In this work, dense and high-purity SiC ceramics have been obtained by pressureless solid-state-sintering with ultra-low contents of sintering additives. The amount of residual B, C and O in the high-purity SiC ceramics was less than 0.15 wt%, respectively, and the total content of other impurity elements (such as aluminum, magnesium, calcium, iron, etc.) was less than 0.015 wt%. Finally, the purity of the as-prepared SiC ceramics was more than 99.5 wt%.     

ZrC/C aerogel with high compressive strength by a carbothermic process

The ZrC/C aerogel is successfully prepared through copolymerization sols combined with carbothermal reduction method, using the ZrOC and phenol formaldehyde (PF) as the sols, and hexamethylenetetramine (HMTA) as cross-linker, respectively. The effects of heating treatment temperatures on physical and thermal properties of the aerogels are also investigated. XRD, SEM, and XPS measurements were adopted to characterize the morphology and microstructure of aerogels. Aerogels displayed low bulk density (0.262?0.379 g/cm³), relatively low thermal conductivity (0.0896?0.1064 W/m?K), and high compressive strength (0.87–4.42 MPa). XRD results show that the aerogel is composed of ZrC and ZrO₂ phases at 1400 °C and ZrC at 1500 °C or even high temperature, respectively, indicating that phase transformation of ZrO₂ into ZrC. XPS results demonstrated that the element Zr, C, and O are based on ZrOC, ZrC, and ZrO valence band binding, respectively. ZrC/C aerogels with excellent physical and thermal properties may be used in high-temperature field soon.     

低成本制造高强度聚酯纤维研究进展

利用低生产成本的熔融纺丝技术制造高强度PET纤维,通过近年来的许多探索工作,尤其是目前正在日本所开展的以熔体结构控制为核心,结合分子质量控制和拉伸、热处理技术的研究以及数学模型的建立等工作结果表明,这个目标是有希望实现的。     

高强度刚玉碳化硅浇注料的研制

以棕刚玉和碳化硅为主要原料、铝酸钙水泥为结合剂,制备出了一种高强度的刚玉碳化硅浇注料。通过优化颗粒级配,调整水泥和复合微粉的加入量,测定试样在各种因素影响下的常温和高温强度。结果表明,研制出的刚玉碳化硅浇注料既具有较高的常温强度,又具有很高的高温强度。     

高强度莫来石基质耐火浇注料的研制

以煅烧二级矾土熟料为集料，合成莫来石、白刚玉粉、ＳｉＯ２微粉、Ａｌ２Ｏ３微粉为粉料，两种纯铝酸钙水泥为结合剂（加入量５％－７％），复合聚磷酸盐作分散剂，研制出高强度莫来石基质浇注料。经１５５０℃，３ｈ热处理后，浇注料的体积密度为２．４２８／ｃｍ３，耐压强度达８７．７ＭＰａ，烧后线变化率＋０．１５％，抗铁法侵蚀性、抗剥落性良好。用于武钢４＃取向硅钢加热炉的步进梁、固定梁和立柱上，寿命比原ＣＭ１６Ｃ浇注料高２．５倍。     

两段中和法制备高品质羟基磷酸钙

开发出将磷酸与方解石、石灰依次中和制备高品质羟基磷酸钙的两段中和法。介绍了反应原理,并通过实验确定了工艺参数（搅拌转速、投料比例、反应温度、反应时间、反应物浓度等）,比较了3种干燥方式的优缺点,并以选用“卧螺离心沉降 + 强力粉碎干燥”的干燥方式为例详细叙述了工艺流程。将两段中和法所得产品和磷酸与方解石中和法所得产品进行了比较,结果显示两段中和法产品具有纯度高、有害杂质少、灼烧减量低等优点,产品质量完全符合中国现行产品标准GB 25558-2010的要求。     

Crystallisation kinetics of hydroxyapatite thin films prepared by sol-gel process

Abstract

Abstract

In this study, the crystallisation of nano hydroxyapatite (HA) films on stainless steel 316L was studied. The film was prepared by sol-gel technique. The process was started with preparation of an HA sol. After aging of the sol at room temperature, a stainless steel 316L substrate was dip coated and then was heat treated from 350 to 450°C at different periods of time in air. The crystallisation behaviour and the transformation-temperature-time diagram of HA films were achieved and analysed using the avrami equation. The results showed that the crystallisation of HA began at 250°C and was increased up to 450°C. The obtained HA film showed a nanostructure character with a suitable crystalinity after heat treatment.     

Microstructure and mechanical properties of hydroxyapatite obtained by gel-casting process

In the present work, well-shaped HAp green bodies were obtained by the gel-casting process with 50 vol.% slurry. After drying, the microstructure and pore distribution of the green body were investigated. The density, compressive strength and flexural strength of the green body were 1.621 g/cm³, 32.6 ± 3.2 MPa and 13.8 ± 1.0 MPa, respectively. After pressureless sintering at the range of 1100–1300 °C for 2 h, the relative density of the final product ranges from 71.8 to 97.1% th. The maximum value of flexural strength, elastic modulus, hardness and fracture toughness were 84.6 ± 12.6 MPa, 138 ± 7 GPa, 4.45 ± 0.18 GPa and 0.95 ± 0.13 MPa m^1/2, respectively. SEM images show a compact and uniform microstructure; the average grain size was found by using the linear intercept method. XRD and FTIR determined the phase and the radical preserved after sintering.     

Characterization of a high strength hydroxyapatite cement with dual chelate-setting using phytic acid and citric acid

With the development of biomaterials, a hydroxyapatite (HA) bone cement based on chelation has gradually attracted attention. This paper presents an investigation on the micromorphology and mechanical property of HA bone cement prepared by HA powders modified by inositol hexaphosphate (IP6, phytic acid). With the citric acid monohydrate (CA) solution used as setting liquid, scanning electron microscopy (SEM) and universal testing machine were employed to investigate the influence of parameters including concentrations of CA as well as powder–liquid ratio on the properties of HA bone cement. In addition, the setting mechanism of chelating cement was analyzed. The results showed that when CA concentration was more than 20 wt.%, the curing products of IP6/CA dual chelating HA cement contained calcium citrate tetrahydrate and tricalcium phosphate (TCP) besides HA. The compressive strength of dual chelated cement increased with the CA concentration. With 10 000 ppm-IP6-HA used as the starting powder, the maximum compressive strength of bone cement prepared with 40 wt.% CA as the setting liquid was up to 57 MPa. Furthermore, the temperature, pH, antibacterial activity measurement, and cell studies in vitro were carried on, suggesting that chelate-setting HA cement has potential development in orthopedic materials.     

高粘合强度复合钢带的研制

以兰化丁腈橡胶（1704）为主体材料,并用长寿氯丁橡胶（120型）,以MEGUM（底涂3270/面涂14550）为粘合剂,研制了具有粘合强度高、耐寒性好、能够采用连续硫化方式硫化的大规格钢带制品,制品所用配合剂均为国产原材料,其基本性能可以达到：橡胶与不锈钢材料剥离强度10kN/m,胶料脆性温度为-50℃。     

一种新型聚氨酯高强胶布的研制

按特种护舷制作要求,研制了一种强度高、柔软性好的新型聚氨酯胶布。这种新型高强胶布采用了聚醚型聚氨酯基础胶料和聚酯纤维骨架材料,进行了耐光老化和耐磨性能改性研究,设计采用了一次挤出热熔涂覆成型新工艺,研制生产的新型胶布强度和粘合强度得到较大提升,并达到了特种护舷制作的性能要求。     

高强度双组分聚氨酯胶粘剂的研制

合成了ε-己内酯-MOCA加成物。以聚碳酸酯二元醇,ε-己内酯-MOCA加成物以及MD I为主体材料制备的双组分结构胶综合性能优异:剪切强度为27.7 MPa,180°剥离强度为5.22 kN/m,定位时间为5 m in,耐温100~120℃。MOCA或者ε-己内酯-MOCA加成物在聚氨酯胶粘剂中的含量大于临界含量时,胶粘剂的固化速度明显加快,粘接性能显著提高。制备的双组分胶粘剂甲乙组分的最佳配比为10∶15.5,此时粘接强度最高,甲乙组分的配比对粘接强度影响较大。     

高铁早强矿渣硅酸盐水泥的研制

湖北某水泥厂在８．３万Ｔ立窑水泥生产线上，成功地开发高铁早强矿渣水泥，并通过了国家建材局水泥专家参加的省级鉴定。该水泥具有早强高，硬化快，抗硫酸盐侵蚀和胶凝性能好等性。     

高强镁质捣打料的研制与应用

通过颗粒级配、结合剂和添加物的选择和加入量的试验，研制出中温（１０００℃，３ｈ）耐压强度达５０ＭＰａ以上的镁质捣打料。试验发现，采用聚磷酸盐作结合剂，添加适量的复合金属粉，可有效提高中温强度。     

Aqueous tape casting process for hydroxyapatite

The condition for the preparation of stable hydroxyapaptite (HA) slurries by aqueous tape casting was identified. To acquire stable low-viscosity slurries, the influences of dispersant, binder and plasticizer on the rheological properties were investigated. The slurries of submicron sized HA behaved as near Newtonian up to a solid loading of 56.1 vol%. Films of HA had very good qualities, such as homogeneity, surface quality, and so on. Results indicated that slurries at selected conditions met the needs of tape casting process.     

新型碳纤维用原丝——高强高模Lyocell纤维纺丝工艺研究

采用天然高相对分子质量纤维素脱脂棉为原料 ,制备了高强高模纤维素纤维 ( L yocell纤维 ) ,并用此作为碳纤维原丝 ,成功制得了强度优于粘胶基碳纤维的 L yocell基碳纤维。考察了高相对分子质量纤维素的溶解特点 ,纺丝工艺对 L yocell纤维聚集态及性能的影响 ,比较了 L yocell纤维和粘胶原丝的表面及截面形态。实验表明 :高相对分子质量纤维素溶解的静溶胀时间和温度对其溶解有明显的影响 ;纺丝过程中 ,大的气隙长度对提高纤维的性能有利 ;随着凝固浴中 N -甲基吗啉 N -氧化物( NMMO )的浓度增加 ,纤维的强度和模量增加 ,当其在凝固浴中的质量分数达到 10 %时 ,强度模量最大 ,浓度继续增加 ,纤维的力学性能开始下降 ;拉伸比增加 ,L yocell纤维的强度模量增加 ,当拉伸比大于 3.0时 ,纤维的性能略有下降