放电等离子烧结法制备以升华性材料为造孔剂的人体植入骨替代多孔镁块体材料

以萘为造孔剂, 采用放电等离子烧结技术(spark plasma sintering, SPS)制备多孔镁块体材料。结果表明, 采用放电等离子烧结技术在470℃时可以制备出结构与尺寸可控性好、开孔率与孔隙率(44.25%)较高、粉体颗粒无明显长大的多孔金属镁块体材料。升华性造孔剂可对孔隙体积进行有效调节, 实现多孔镁材料体内小孔与大孔的合理搭配, 进一步改善多孔镁材料孔隙之间的连通性。将升华性造孔剂与放电等离子烧结技术相结合后, 对于开孔性与颗粒连接性要求较高的多孔金属材料制备具有技术优势, 并对解决传统造孔剂法制备生物多孔金属材料所面临的二次污染问题具有很好的借鉴意义。     

添加升华性造孔剂的放电等离子法制备多孔铝块体材料

为解决高孔隙率多孔金属材料制备过程中的污染问题,以升华性萘颗粒为造孔剂,采用放电等离子脉冲烧结法(SPS)进行多孔铝块体材料的制备。结果表明,升华性造孔剂可在实现多孔铝材料高孔隙率的同时,有效提高其洁净度。采用该方法在350℃时可以制备出结构与尺寸可控性好、开孔效果好、孔隙率(63.33%)较高、粉体颗粒无明显长大的多孔金属铝块体材料。升华性造孔剂可对孔隙体积进行有效调节,实现多孔铝材料体内小孔与大孔的合理搭配,进一步改善多孔铝材料孔隙之间的连通性,该方法与SPS烧结技术相结合后,对于开孔性与颗粒连接性要求较高的多孔金属材料制备具有技术优势。     

Porous Permeable Polymers

Features of extrusion for mixtures of polyvinyl chloride and a pore-forming agent with the aim of preparing very porous materials are studied. It is shown that extrusion rate depends on the particle size of the pore-forming agent with the same volume content. This is explained by the difference in the structure of mixtures with respect to pore-forming agent. Marked anisotropy is established for the porous structure of materials in the extrusion direction and perpendicular to it. The hydraulic and mechanical properties of porous materials are determined and possible fields for their application (aeration in fish breeding, capillary transport for under-root irrigation, etc.) are suggested.     

Cu基热管芯体多孔材料增孔补强的研究

对不同粒径Cu粉、不同造孔剂(CuCl2.2H2O、NaCl)及其含量的Cu基热管芯进行了对比试验,分别对其开孔隙度、渗透系数、压缩性能进行了测试;并用扫描电镜(SEM)观测芯体的孔洞特征及烧结颈的形成情况,进一步探讨了烧结强化机理。结果表明:球形Cu粉粒径越大,Cu基热管芯的孔隙度和渗透系数较大,但强度越低;添加造孔剂CuCl2.2H2O有造孔和强化基体的双重作用;添加NaCl增加孔洞效果明显,但仅有造孔作用。     

新型多孔粒状赤泥吸附材料的制备及表征

采用微波造孔活化技术,在不添加造孔剂的情况下,对赤泥实现造孔活化和强化来制备新型吸附材料。利用XRD、SEM、FTIR等手段对制备的吸附材料进行了表征。结果表明,该粒状赤泥经活化后,孔道清晰,所制备的吸附材料为多孔制,表面具有更多的吸附活性孔位。     

Properties of the capillary structure of copper powder

Conclusions The properties of capillary structures of type PMS copper powder of different particle size composition obtained by sintering of freely poured material and by pressing with and without a poreforming material with subsequent sintering were investigated experimentally. It was shown that the capillary structures obtained by pressing with a pore-forming material possess uniformly high transport properties and a good quality of interparticle contacts.Translated from Poroshkovaya Metallurgiya, No. 8 (272), pp. 86–90, August, 1985.     

Effect of the structure of the pore space on the mechanical properties of highly porous materials produced with pore-forming agents

Correlation between the mechanical properties of porous materials obtained with use of a pore-forming agent, and the pore structures has been studied. It was shown that the larger the pores, the higher the bending strength and elastic modulus. The curve of mechanica properties versus porosity is S-shaped. A theoretical equation has been derived for this curve. The region of the bend in the S curve was established to correspond to the phase transition of the metallic claster from a quasi-three-dimensional to a quasi-two-dimensional structure.     

pH-dependent stability and membrane interaction of the pore-forming domain of colicin A

Thermal stability of the pore-forming domain of colicin A was studied by high sensitivity differential scanning calorimetry and circular dichroism spectroscopy. In the pH range between 8 and 5, the thermal denaturation of the protein in solution occurs at 66-69 degrees C and is characterized by the calorimetric enthalpy of approximately 90 kcal/M. At pH below 5, there is a rapid pH-dependent destabilization of the pore-forming domain resulting in the lowering of the midpoint denaturation temperature and a decrease in the calorimetric enthalpy of denaturation. Circular dichroism spectra in the near and far ultraviolet show that the thermotropic transition is associated with collapse of the native tertiary structure of the pore-forming domain, although a large proportion of the helical secondary structure remains preserved. The present data indicate some similarity also between acid-induced and temperature-induced denaturation of the pore-forming domain of colicin A. Association of the pore-forming domain with phospholipid vesicles of dioleoylphosphatidylglycerol results in total disappearance of the calorimetric transition, even at pH values as high as 7. Since lipid binding also induces collapse of the near ultraviolet circular dichroism spectrum, these data indicate that interaction with the membrane facilitates a conformational change within the pore-forming domain to a looser (denaturated-like) state. These findings are discussed in relation to the recent model (van der Goot, F. G., Gonzalez-Manas, J. M., Lakey, J. H., Pattus, F. (1991) Nature 354, 408-410) which postulates that a flexible "molten globule" state is an intermediate on the pathway to membrane insertion of colicin A.     

注射成形制备TiNi多孔材料

利用粉末注射成形工艺制备了TiNi多孔材料,研究了注射喂料的流变性能,造孔剂NaCl对多孔材料性能的影响。试验结果表明:喂料的流变性能良好;造孔剂可以显著提高材料的孔隙度、孔径;能谱分析和X射线物相分析没有发现NaCl残留,TiNi多孔材料主要由Ni3Ti、Ti2Ni、TiNi、TiC相组成。     

Amoebapores, a family of membranolytic peptides from cytoplasmic granules of Entamoeba histolytica: isolation, primary structure, and pore formation in bacterial cytoplasmic membranes

Three peptides with pore-forming activity were isolated from the cytoplasmic granules of pathogenic Entamoeba histolytica by acidic extraction, gel filtration and reversed-phase high-performance liquid chromatography. Partial amino acid sequence analysis of the three active peptides revealed that the most abundant of them was amoebapore and the other two were isoforms thereof. Cloning and sequencing of genomic DNA resolved the amino acid sequence of the two newly recognized peptides. The three peptides designated amoebapores A, B and C were found to have the same molecular size but to differ markedly in their primary structure, although all six cysteine residues are conserved. Despite sequence divergence, structural implications predict for the three peptides a similar amphipathic alpha-helical conformation stabilized by disulphide bonds. All three isoforms exhibit pore-forming activity toward lipid vesicles, but they differ in their kinetics. They also are capable of perturbing the integrity of bacterial cytoplasmic membranes and thereby kill Gram-positive bacteria. The amoebapores represent a distinct family of membrane-active peptides that may function intracellularly as antimicrobial agents but may also confer cytolytic activity on the parasite.     

Formation of highly-porous ceramic based on silicon carbide

Data for the effect of charge composition and characteristics of the starting silicon carbide powder and poreforming agent on the formation of highly porous SiC-base ceramics are studied and summarized. It is shown that porous (up to 70%) polycrystal SiC materials obtained on the basis of finely crystalline (3–5 µm) silicon carbide with introduction of ammonium bicarbonate (grain size 0.1–0.2 mm) as a pore-forming agent into the initial charge have the best structural parameters with sufficient mechanical strength and high gas permeability.Institute of Problems of Materials Science, National Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, No. 5–6, pp. 48–54, May–June, 1994.     

多孔金属材料制备工艺及展望

本文介绍了多孔金属材料现阶段的发展状况、常用制备工艺及功能应用,并对多孔金属材料的发展趋势进行了展望。制备方法主要是从熔体、粉末、沉积几方面展开概述,再对各种工艺的制备原理、优缺点、孔隙率和金属材料进行了综述,并列举了近年国际、国内采用新型发泡剂和造孔剂对多孔金属的研究状况和成果。多孔金属材料既可以用于结构材料也可以用于功能材料,在减振、吸能及轻量化方面有着广阔的应用前景。     

染料敏化太阳能电池中多孔电极制备及性能

将喷涂法应用于制备染料敏化太阳能电池光阳极,具有浆料制备简单、易操作、成本低廉等优势.本文以钛酸丁酯和P25为原料配制浆料,采用喷涂法制备二氧化钛薄膜,选择乙二醇作为造孔剂,探索了乙二醇的最佳加入量.通过对电池I-V曲线,二氧化钛薄膜表面粗糙度、染料吸附量和漫反射谱,以及光阳极的扫描电镜照片和交流阻抗图谱的分析,得到如下结果:当乙二醇与钛酸丁酯的体积比为1:1时,二氧化钛薄膜的粗糙度最大,即孔隙率和比表面积最大,因此染料吸附量达到1.47×10-7mol·cm-2,电池性能最好,其中开路电压为0.69 V,短路电流为13.0 mA·cm-2,光电转化效率达到5.38%,比不加造孔剂时增加了将近1倍,此时电子的扩散转移电阻也最小.      

Principles of the design of highly porous layered composites working in the bending mode

A comparative analysis is made of the spesific mechanical characteristics of a sandwich-type laminated porous composite under bending. The external layers of the composite are compact while the internal layer consists of a highly porous material made by using a pore-forming agent. The specific stiffness, strength, and yield load as a function of the volume fraction of pores Θ and the porous/compact-layer thickness ratio λ are considered. The stiffness, strength, and yield load are shown to be affected by variations of Θ and λ when the weight of the composite is constant. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(412), pp. 70–78, March–April, 2000.     

红外辐射多孔陶瓷的研制

为了研制1种新型轻质热工材料——红外辐射多孔陶瓷,研究了其配方组成及制备工艺,对材料的微观结构、气孔的尺寸和分布、气孔率、体积密度、导热系数、机械性能及热发射率分别进行了测定。结果表明:采用发泡和添加造孔剂相结合的制备工艺,可获得孔径小且分布均匀,具有优良绝热性能及较高常温耐压强度的红外辐射多孔陶瓷材料,且掺入由过渡族氧化物组成的高辐射率材料,可使该材料在整个红外辐射波段都具有很高的发射率。     

Study of the cellular solidification structure in a continuously cast high purity copper

The aim of this paper is to characterize the principal microstructural features of continuously cast high purity copper (99.999 pct Cu), particularly those which might influence high temperature creep. This material contains a cellular solidification structure resulting from impurity segregation due to constitutional supercooling of the melt during solidification. This structure could not be eliminated from the solid copper by thermomechanical treatment. The grown-in structure was studied using optical and electron metallography as well as etch-pitting techniques. In the as-cast material a loose network of dislocation tangles was observed, and in certain locations, preferential etching attack. In addition, small voids were found within the dislocation tangles. Thermomechanical treatment eliminated the dislocation tangles almost entirely, but left locations susceptible to preferential etching attack. At those locations impurities were probably concentrated into zones of a size of a few 1000Å. From solubility and concentration considerations, small precipitates (less than 80Å in size) or clusters of carbon are suspected.     

转炉镁质喷补料的研制

探讨了影响转炉喷补料的主要因素：原料的对比、粒度的影响、结合剂的影响等,通过使用复合结合剂,提高了喷补料的粘附率及其高温强度,降低大颗粒的比例,减少了颗粒的反弹,在转炉上使用实践表明,效果满意。     

拜耳法赤泥质陶粒滤料去除水中溶解油的研究

研究了不同配方的拜耳法赤泥质陶粒滤料对水中石油类溶解油的吸附除油效果。结果表明,在拜耳法赤泥、煤矸石、河道底泥、造孔剂质量比分别为40∶12∶40∶8和45∶17∶30∶8时,陶粒滤料除油效果显著,在相同条件下,陶粒的除油率接近活性炭但高于砂粒,废水中少量碳酸钠的存在更有助于陶粒的除油。     

Ni-Cr-Co-W-Mo-Al-Ti合金制备多孔材料的组织与性能研究

用粉末烧结法制备了孔结构为球形中空孔和线型中空孔的镍基多孔高温合金材料.对试样进行显微组织观察和力学性能测试.结果表明:制备的多孔高温合金材料的孔隙分布均匀,孔径大小一致.通过高温烧结,多孔合金骨架处的金属颗粒之间形成了烧结颈,发生了烧结结合.生成孔的孔隙度随造孔剂(尿素)的添加量增加而增加,当造孔剂的质量分数为40%时,可得到孔隙度为81.62%的球形多孔材料.多孔材料具有优良的能量吸收性能,其压缩性能随孔隙度和孔径的增加而下降.     

Nucleotide sequence of 5''-upstream region and expression of a silkworm gene encoding a new member of the attacin family

The morphometric and morphological changes in the mesothelial cell population were studied in rabbits in peritoneal dialysis with lactate and bicarbonate buffer solution. During dialysis the mesothelial population underwent radical changes in morphology and morphometric analysis showed a significant increase in cell size. Light microscope examination showed two types of changes: hyperplasia of the mesothelial cell with diameters of up to 80 microns, nucleus proportional to the cytoplasm, a large nucleole giving an owl's eye appearance and cytoplasm rich in granular material. The second change was multiple nuclei and arrest of cell division. Nuclear division occurred, but no separation of the cytoplasm. The cells became larger than 200 microns, packed with nuclei and relatively little cytoplasm. Electron microscopy confirmed that the hyperplastic cells had perfect structure whereas the polynucleate cells contained vacuoles and little cytoplasmic reticulum. Immunohistochemistry using monoclonal antibodies SK2-27 and SK 60-61 specific to cytokeratins 14, 16, 17 and 8, 18, respectively, identified the cells as mesothelial. The changes were related to the glucose content of the peritoneal dialysis solution. Glucose is therefore the bioincompatible agent that modifies the mesothelium during peritoneal dialysis, causing it to become hyperplastic or blocking replication.