高致密度低氧含量 3D 打印用球形钼粉的制备研究

本文通过"等离子球化+氢还原"的方法制备了高致密度低氧含量的3D打印用球形钼粉,分析了球形钼粉的特性。通过优化等离子过程中的功率、送粉量和气体流量参数,制备了高致密度球形钼粉;并且采用氢气还原球形钼粉,降低其氧含量。试验结果表明:与原始粉末相比,制备的3D打印用球形钼粉的松比从2.3 g/cm~3提高到6.01 g/cm~3;流动性从35 s/50 g提高到10.5 s/50 g;氧含量降低到270 ppm。     

喷雾干燥法制备球形喷涂钼粉及烧结工艺的研究

本文采用球磨工艺制备钼粉料浆,通过喷雾干燥法制备球形团聚钼粉,然后经过保护气氛脱脂烧结制备出球形喷涂钼粉,同时对烧结前后球形钼粉的松比、流动性及组织形貌进行了表征与分析。结果表明,料浆与钼粉颗粒尺寸的均匀性、粘结剂、固含量以及球磨时间密切相关,合适的固含量和粘结剂含量、较长的球磨时间下可以获得具有较好形貌和完整性的球形钼粉;在喷雾干燥的过程中,转速是影响球形钼粉颗粒大小的很重要因素;在保护气氛脱脂烧结过程中,烧结温度对钼粉的松装密度及流动性影响较大,提高烧结温度是改善钼粉松比及流动性的主要途径。     

球形钛及钛合金粉制备工艺研究现状

球形钛粉具有球形度高、流动性好、松装密度大、氧含量低等特点。介绍了球形钛粉的几种常见制备工艺的基本原理及目前的研究现状,包括:雾化法、等离子旋转电极法、等离子火炬雾化法和射频等离子球化法。雾化法是生产球形钛粉的主流生产方法,包括惰性气体雾化法和离心雾化法,其中惰性气体雾化法具有生产效率高、粒径分布宽、细粉回收率高等特点,是目前生产球形钛粉的主要方法;等离子旋转电极法生产出的粉末具有球形度高、流动性好,但细粉回收率低等特点;等离子火炬雾化法可以生产出球形度高、流动性好的粉末,但设备生产成本较高;射频等离子球化法生产出的粉末球形度高、流动性好,但产能较低。最后对比了几种工艺生产出的粉末特征,指出中国目前在球形钛粉制备工艺过程中存在的问题,对球形钛粉制备及发展方向进行了展望。     

球形/类球形钽粉的制备

研究了用氢化破碎技术制备球形/类球形钽粉的工艺及钽粉的性能。以二次电子束高温轰击的高纯钽锭为原料,经过氢化吸氢,球磨机磨筛制粉,然后经过脱氢处理,再经气流粉碎机进行气流整形,得到形貌改善的原粉,通过酸水洗除杂,真空热处理及镁还原降氧过程,得到球形/类球形钽粉。这种钽粉由独立的、单一的粉末颗粒组成,钽粉的粒度分布范围集中,D90小,流动性好,氧含量低,可以满足3D打印、喷涂等方面的应用要求。     

增材制造用W-Nb合金粉末的制备与应用

结合钨合金的特性及增材制造过程对粉末均匀性、稳定性的要求，以微米级球形钨粉和纳米级铌粉为原料，采用行星球磨工艺制备了可用于增材制造的W-Nb复合型粉末，利用球磨过程中的作用力，将纳米粉末分散并均匀吸附在球形钨粉表面，形成面包覆结构；分析了球磨时间对粉末形貌及物理性能的影响。结果表明，随着球磨时间的延长粉末主要发生以下变化：（1）球形钨粉形貌不变，纳米铌粉之间存在明显的团聚；（2）球形钨粉形貌不变，纳米铌粉充分分散且在球形钨粉表面吸附；（3）吸附在球形钨粉表面的铌粉之间发生一定的冷焊，球形钨粉表面开始出现破损；（4）铌在钨中发生一定的固溶，但是球形钨粉大量破损。采用粉床型电子束增材制造技术对复合粉末的工艺适应性进行了验证，复合粉末铺展均匀、稳定，成形样品成分均匀，晶界处不存在明显的铌元素富集。     

熔盐电解制备骨骼3D打印用非球形高纯钛粉

通过熔盐电解的方法,制备出了适用于骨骼3D打印用的非球形高纯钛粉,其成本不到球形钛粉的十分之一。熔盐电解制备出的金属钛粉,具有高比表面积和高纯的特点,在进行骨骼3D打印的时候,更容易形成多孔状,而其高纯性更是保证了人体的健康。通过SEM分析钛粉的微观形貌,研究了骨骼3D打印用非球形高纯钛粉的特点,电解钛粉由于只存在一步的电沉积反应,颗粒的生成非常有规律,这也是电解钛粉虽然不是球形,但却有着很好流动性的原因;通过循环伏安曲线,分析了钛离子的阴极沉积过程,确定了钛粉的沉积电位。     

高致密球形钼粉制备工艺研究

采用感应等离子设备制备出球形钼粉,研究了工艺参数对制备高致密度球形钼粉的影响。用霍耳流速仪检测球形钼粉的流速,斯科特容量计检测球形钼粉的松装密度,用电子扫描显微镜（SEM）观测球化钼粉的微观形貌。研究表明,等离子体处理可以使钼粉形状由不规则变为球形,钼粉流动性显著提高,松装密度增大,实现了钼粉的致密化,同时纯度提高。且当输入功率为25kW·h、送粉量50g／min钼粉的球化最为理想,流速达16s／50g,松装密度为4．8g/cm3。     

316L、317L的MIM注射成形生坯件溶剂脱脂工艺研究

介绍了316L、317L两种不锈钢MIM生坯溶剂脱脂过程中溶剂种类、溶剂温度、工件厚度、钢粉的粒度及形貌对溶剂脱脂过程的影响。结果表明：选择正己烷作溶剂，控制溶剂温度37℃可以避免溶剂脱脂过程中工件开裂、鼓泡问题，而且能减少对环境的污染，给操作者提供更好的劳动条件；溶剂脱脂早期大粒度球形钢粉的生坯要比小粒度不规则形状钢粉的生坯脱脂速度快，但后期小粒度不规则形状钢粉的生坯脱脂较大粒度球形钢粉的生坯速度快。     

水热合成W-25Cu复合粉的热力学分析

以钨酸钠(Na2WO4·2H2O)和硝酸铜[Cu(NO3)2·3H2O]为原料,采用水热合成法制备W-Cu复合粉,计算在不同pH值条件下水热合成W-Cu复合粉的回收率,并对制取W-Cu复合粉前驱体的过程进行热力学分析。采用XRD、SEM、EDS和TEM对所制备W-25Cu复合粉的物相、形貌和微观组织进行表征。结果表明:在不同溶液浓度和pH值下的离子回收率不同。当钨酸钠浓度为0.6mol/L,硝酸铜浓度为0.578 6mol/L且pH值为5.5时,离子以CuWO4·2H2O形式析出,溶液中离子的回收率达到99%以上。水热合成产物具有分散性好,粒度均匀,大小为15~20nm。经500℃煅烧、800℃氢还原60min,得到了W和Cu元素分布均匀的W-Cu复合粉,具有近球形的W包覆Cu结构,粒度为100~200nm。     

松比大、纯度高、球形团聚钼粉制备工艺研究

研究了松比大、纯度高、球形团聚钼粉的制备工艺过程,该工艺过程包括原料钼粉的喷雾造粒、喷雾造粒钼粉的脱脂、烧结(喷雾造粒—脱脂—烧结).结果表明:该制备工艺中,喷雾造粒是控制粉末的形貌和粒度的主要环节;脱脂温度是控制粉末纯度的重要参数;烧结是控制成品粉末物理性能及组织形貌的关键工艺;采用该工艺制备的团聚球形钼粉松比大、流动性好、纯度高,不仅适用于喷涂作业,还可用于精密器件的制备.     

NDA-150树脂在含酚废水处理中的应用

采用新型大孔吸附树脂NDA-150处理水杨酸生产中产生的含酚废水,研究了pH值、温度、吸附速率对树脂吸附能力的影响,不同脱附剂浓度、温度条件下的解吸效率。通过对最佳吸附、脱附条件的研究,确定了树脂法处理水杨酸含酚废水的最佳工艺条件,不仅减少了对环境的污染,而且回收了废水中的苯酚和水杨酸,具有明显的经济效益和环境效益。     

Human vitreous hyaluronidase: isolation and characterization

PURPOSE: Hyaluronic acid (HA) is the predominant glycosaminoglycan (GAG) of the human vitreous. Interaction of this HA with vitreous collagen is important for maintaining gel structure. The mechanism of HA homeostasis in the vitreous is incompletely understood. The aim of this study was to determine whether hyaluronidase, an endoglycosidase that degrades HA, was present in human vitreous. METHODS: Vitreous samples were collected from post-mortem eye bank specimens and from non-hemorrhagic, non-inflamed biopsy specimens. Vitreous hyaluronidase was purified by a series of column chromatographic steps, and its activity was measured by an ELISA-like assay and by substrate gel electrophoresis through and HA-impregnated gel. The purified hyaluronidase was also analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and by Western blotting. RESULTS: Hyaluronidase activity was detected in vitreous samples from both post-mortem and biopsy specimens. The enzyme was most active at acid pH, but demonstrated significant activity at neutral pH. The partially purified enzyme migrated as a 59 kDa protein on SDS-PAGE, and a single band on Western blots. CONCLUSIONS: Hyaluronidase is present in the human vitreous. Thus, hyaluronidase may be involved in HA catabolism in the vitreous and may play a role in determining its gel structure.     

某铅锌矿选矿废水的治理与回用试验研究

某铅锌矿选矿废水成分复杂,含有多种重金属离子、多种残余选矿药剂,废水中SS、CODcr、pH、Pb^2＋、Znb^2＋等指标超标。直接回用对选矿指标影响很大,直接排放会对生态环境产生很大的影响和污染。试验依据该选矿废水特点和选矿工艺要求,采用“混凝沉淀-酸碱中和一氧化-澄清”的废水处理工艺,对该选矿废水进行治理,处理水水质达到污水综合排放标准一级标准。通过对选矿药剂制度的创新和选矿工艺的优化,选矿废水处理后成功地进行了回用,实现了零排放。     

Zinc phosphating of 6061-Al alloy using REN as additive

Zinc phosphate coating formed on 6061-A1 alloy was studied with the help of electrochemical measurements, Fourier Transform Infrared （FTIR）, and Scanning Electron Microscopy （SEM）, after dipping it in phosphating solutions containing different concentrations of Rare Earth Nitrate （REN）. REN, which acted as an accelerator in the phosphating solution, could catalyze the surface reaction and accelerate the phosphating process. REN mainly enabled the P in the phosphate coating to exist in the form of PO4^3- and promoted the hydrolysis of phosphatic acid in a liquid layer at the cathodes. This resulted in the evolution of H2 at the cathodes, which increased the local pH value and in turn drove the precipitation of the phosphate coating. Additionally, REN was adsorbed on the surface of the aluminum substrates to form a gel during the phosphating process. These gel particles were good crystal seeds, which helped to form phosphate crystal nuclei and possess the function of a nucleation agent that could decrease the phosphate crystal size. The corrosion resistance of the formed zinc phosphate coatings was improved.     

Zinc phosphating of 6061-Al alloy using REN as additive

Zinc phosphate coating formed on 6061-Al alloy was studied with the help of electrochemical measurements, Fourier Transform Infrared (FTIR), and Scanning Electron Microscopy (SEM), after dipping it in phosphating solutions containing different concentrations of Rare Earth Nitrate (REN). REN, which acted as an accelerator in the phosphating solution, could catalyze the surface reaction and accelerate the phosphating process. REN mainly enabled the P in the phosphate coating to exist in the form of PO43- and promoted the hydrolysis of phosphatic acid in a liquid layer at the cathodes. This resulted in the evolution of H2 at the cathodes, which increased the local pH value and in turn drove the precipitation of the phosphate coating. Additionally, REN was adsorbed on the surface of the aluminum substrates to form a gel during the phosphating process. These gel particles were good crystal seeds, which helped to form phosphate crystal nuclei and possess the function of a nucleation agent that could decrease the phosphate crystal size. The corrosion resistance of the formed zinc phosphate coatings was improved.     

Gastroduodenal mucosal protection

The barrier that protects the undamaged gastroduodenal mucosa from autodigestion by gastric juice is a dynamic multicomponent system. The major elements of this barrier are the adherent mucus gel layer, which is percolated by the HCO3- secretion from the underlying epithelial cells; the epithelial layer itself, which provides a permeability barrier and can rapidly repair superficial damage by a process of cell migration referred to as reepithelization or restitution; and a specially adapted vasculature, which provides a supply of HCO3- for transcellular transport and/or diffusion into the mucus layer. Passive diffusion of intestinal HCO3- into the lumen is particularly important when there is superficial damage resulting in increased leakiness of the mucosal epithelium. The process of reepithelization occurs by the migration of performed cells from gastric pits or duodenal crypts. This process is quite distinct from the wound healing and associated inflammatory response that accompany more severe injury or chronic damage. The adherent mucus gel acts as a physical barrier against luminal pepsin and provides a stable unstirred layer that supports surface neutralization of acid by mucosal HCO3-. Surface neutralization by mucosal HCO3- provides a major mechanism of protection against acid in the proximal duodenum. In the stomach, where luminal acidity can fall to around pH 1, other mechanisms of protection must exist, since the surface pH gradient is reported to collapse when luminal H+ exceeds approximately 10 mM. This collapse of the surface pH gradients may reflect, at least in part, that such studies have been mostly performed on non-acid-secreting mucosa where the supply of HCO3- to the interstitium from the parietal cells will be reduced. However, because the gastric mucosa can withstand prolonged exposure to acid without apparent damage, this implies an intrinsic resistance of the epithelial apical surface. This is amply illustrated within the gastric glands that do not secrete mucus and HCO3- yet are exposed to undiluted pepsin and an isotonic solution of HCl. Bicarbonate and mucus secretions together with mucosal blood flow are under paracrine, endocrine, and neural control. The rate of reepithelialization will depend on local chemotactic factors, adhesion mechanisms, and the creation of an acid/pepsin/irritant-free environment under a protective gelatinous or mucoid cap. If optimal conditions are met, then the rate of reepithelialization appears to depend primarily on the intrinsic properties of the migrating cells themselves rather than control by exogenous mediators.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of mild acid treatment on the survival, enteropathogenicity, and protein production in vibrio parahaemolyticus

Vibrio parahaemolyticus is an important food-borne enteropathogen that encounters various adverse conditions in its native environment or during infection. Effects of mild acid treatment on survival under stress conditions, enteropathogenicity, and protein production in this pathogen were investigated. Logarithmically grown cells, at pH 7.5 shifted to pH 5.0 for 30 min, were more resistant to subsequent acid challenge at pH 4.4. A two-phase adaptive procedure (pH 5.8 for 30 min; pH 5.0 for 30 min) was better than a single-phase procedure for enhancing the acid tolerance of this pathogen. The acid-adapted cells were cross-protected against the challenges of low salinity and thermal inactivation. One-dimensional polyacrylamide gel electrophoresis revealed that proteins with molecular masses of 6.4, 9.0, 13.6, 16.3, 18.9, 22.9, 24.4, 28.3, 33. 9, 36.9, 41.2, 47.6, 58.1, 65.6, 80.5, 88.2, and 96.9 kDa were induced or significantly enhanced, while proteins of 25.3, 30.1, 30. 7, and 91.7 kDa were significantly inhibited. Two-dimensional polyacrylamide gel electrophoresis revealed that 20 species of proteins were induced or significantly enhanced, while 26 species were inhibited. In assays conducted using the suckling mouse model, enteropathogenicity of the acid-adapted cells was significantly enhanced in terms of intestine/body weight ratio and in vivo recovery of infected cells.     

Importance of selected inhaler characteristics and acceptance of a new breath-actuated powder inhalation device

Proteins were extracted from uric acid stones with 6M guanidine chloride (pH 8.5), which were successively developed by 12% polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). Amino acid sequence analysis of each band on SDS-PAGE revealed that major components in uric acid stones were immunoglobulin alpha heavy and kappa light chains. Although immunoglobulin heavy chain (gamma and mu, as well as alpha) and a kappa light chain were clearly detected in uric acid stones by Western blotting using their specific antibodies, no lambda chains whatsoever could be detected. The results suggest that immunoglobulins selectively containing kappa light chain might have specific functions in uric acid stone formation as stone matrices.     

Purification and partial characterization of acid phosphatase from Candida lipolytica

Non-specific acid phosphatase from Candida lipolytica cells was purified 111-fold by chromatography on DEAE-cellulose and gel filtration on Sephadex G-100 and Sepharose 4B. The enzyme is a glycoprotein containing 67% neutral sugars. The molecular mass of the highly purified acid phosphatase was found to be approximately 95 kDa by both SDS-PAGE and gel filtration. The pH and temperature optima were 5.8 and 55 degrees C, respectively. The enzyme was stable at pH values between 3.5 and 5.5 and at temperatures up to 60 degrees C. The purified phosphatase had a Km value of 3.64 mM for p-nitrophenyl phosphate and showed broad substrate specificity.     

Characterisation of basic proteins from Spiroplasma melliferum using novel immobilised pH gradients

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) has become the method of choice for efficient separation of complex protein mixtures. Previously, analysis of the Spiroplasma melliferum proteome (protein complement of a genome) has been performed with pH 3-10 and narrow range pH 4-7 IPG gel strips. We report here on the use of novel 18 cm basic (pH 6-11) immobilised pH gradients (IPG) to increase the resolution of protein spots visible within 2-D gels. These gradients were synthesised to emulate the gradient of commercially available IPG gel strips in a 5 cm region of overlap so as to attempt construction of a more complete map of cellular protein expression. Approximately 50 additional gene products were detected from S. melliferum that were not previously well-resolved or visible using wide-range pH 3-10 IPG gel strips. Twenty-seven of these were electrotransferred to polyvinylidene difluoride (PVDF) membrane and analysed by N-terminal protein microsequencing. Protein spots with an initial peak yield of as little as 100 femtomoles (fm) were sequenced to 5-10 amino acid residues, demonstrating the importance of improved sample handling procedures and analytical technologies. Many essential metabolic enzymes were shown to have basic pI, including: glyceraldehyde-3-phosphate dehydrogenase, pyruvate kinase, carbamate kinase and lactate dehydrogenase. A very basic protein (pI approximately 11.0) was identified as uridylate kinase, an enzyme indirectly associated with pyrimidine biosynthesis and thought be absent in some members of the bacterial class Mollicutes. The advent of novel basic (pH 6-11) IPGs has allowed the visualisation of a significantly greater percentage of the 'functional proteome', that portion of the total protein complement of a genome actively translated within a specific time frame, on 2-D electrophoresis gels. This will aid in the characterisation of translated gene products in conjunction with genome sequencing initiatives.