化学气相沉积ZrO_2涂层的表面微观形貌演变

采用ZrCl4-CO2-H2-Ar体系,在不同温度或氢气流量条件下采用常压化学气相沉积法(APCVD)通过不同沉积流程在C/C样品表面制备ZrO2涂层。用X射线衍射分析仪(XRD)和扫描电镜(SEM)分析涂层的物相组成和形貌特征。结果表明:随沉积温度升高,ZrO2涂层表面形貌由小颗粒堆积态向大尺寸多晶转变;氢气流量为0时,只在局部区域出现了少量ZrO2,当氢气流量为400mL/min时,ZrO2涂层晶粒尺寸较大且晶体学平面特征最明显;在氢气流量为800mL/min时沉积出现了副产物ZrC与C;在氢气流量为1600mL/min时,出现沉积副产物ZrC;连续沉积时,得到的ZrO2涂层为山峰状形貌。     

Three-dimensional mathematical model for transport phenomena in horizontal chemical vapor deposition reactors

A three-dimensional (3-D) mathematical model describes the transport phenomena and the resulting rate of deposition in horizontal chemical vapor deposition (CVD) reactors. The model employs a finite difference scheme to solve the governing partial differential equations to predict the velocity field, temperature distribution, and concentration profiles of various gas species. The rate of silicon deposition by the reaction of SiCl₄ and H₂ is predicted. The model shows that the buoyancy-driven flow in such reactors has a marked effect on the uniformity of deposition. In these calculations, the concepts of local equilibrium at the substrate and thermal diffusion of SiCl₂ away from the substrate were considered in evaluating the rate of silicon deposition. Incorporation of these factors has significantly improved the predictive capability of the model. The rates of silicon deposition were calculated for two different thermal boundary conditions which had a pronounced effect on the uniformity of deposition. Substrate tilt contributes to the production of a more uniform silicon deposition. The model was used as a computer-aided design tool for process optimization; a simple addition of two fins to the top wall (without any substrate tilt) of the reactor can significantly reduce the secondary roll cell formation and should lead to more uniform deposition.     

化学气相沉积制备粉体材料的原理及研究进展

采用化学气相沉积法(chemical vapor deposition,简称CVD)不仅可以制备金属粉未,也可以制备氧化物、碳化物、氮化物等化合物粉体材料.该法是以挥发性的金属卤化物、氢化物或有机金属化合物等物质的蒸气为原料,通过化学气相反应合成所需粉末,因其制备的粉末纯度高,比表而积大,结晶度高,粒径分御均匀、可控,在粉体材料制备方面的应用日趋广泛.该文主要介绍CVD技术制粉的形成机理和研究进程.CVD法制粉主要包括化学反应、晶核形成、粒子生长以及粒子凝并与聚结4个步骤.按照加热方式不同,CVD技术分为电阻CVD、等离子CVD、激光CVD和火焰CVD等,用这4种技术制备超细粉末各有其优缺点,选择合适的气源,开发更为安全、环保的生产工艺,以及加强尾气处理是使CVD法制备超细粉体材料付诸于工业应用的重要保证.     

金属有机化学气相沉积W薄膜

以W(CO)6为前驱体,采用金属有机化学气相沉积法(MOCVD)在Cu基体表面进行了沉积W薄膜的研究.通过调整W(CO)6热解温度、W(CO)6气化温度及载气(高纯氢气)的流量等工艺参数,成功制备了均匀、致密的W薄膜;研究了沉积速率与上述参数之间的关系,并得出了在本试验条件下应用金属有机化学气相沉积法(MOCVD)制备...     

Extraction and mutual separation of rare earths from used polishes by chemical vapor transport

A dry recovery process for rare earths from used polishes has been investigated by using a chemical vapor transport method via the formation of vapor complexes RAl _n Cl_3+3n (R=rare earth). The used polishes were chlorinated with N₂+Cl₂ gas mixture at 1273 K, and the resulting rare earth chlorides were transported chemically with the vapor complexes along the temperature gradient. Most rare earth chlorides, AlCl₃, and FeCl₃ were transported during 82 hours of heating. The rare earth chlorides were mainly condensed over the temperature range of 1220 to 730 K. On the other hand, AlCl₃ and FeCl₃ were deposited at temperatures below 400 K. The highest LaCl₃ and CeCl₃ purity of about 80 pct was obtained in the process.     

Trends in odor intensity for human and electronic noses: relative roles of odorant vapor pressure vs. molecularly specific odorant binding

Response data were collected for a carbon black-polymer composite electronic nose array during exposure to homologous series of alkanes and alcohols. The mean response intensity of the electronic nose detectors and the response intensity of the most strongly driven set of electronic nose detectors were essentially constant for members of a chemically homologous odorant series when the concentration of each odorant in the gas phase was maintained at a constant fraction of the odorant's vapor pressure. A similar trend is observed in human odor detection threshold values for these same homologous series of odorants. Because the thermodynamic activity of an odorant at equilibrium in a sorbent phase is equal to the partial pressure of the odorant in the gas phase divided by the vapor pressure of the odorant and because the activity coefficients are similar within these homologous series of odorants for sorption of the vapors into specific polymer films, the data imply that the trends in detector response can be understood based on the thermodynamic tendency to establish a relatively constant concentration of sorbed odorant into each of the polymeric films of the electronic nose at a constant fraction of the odorant's vapor pressure. Similarly, the data are consistent with the hypothesis that the odor detection thresholds observed in human psychophysical experiments for the odorants studied herein are driven predominantly by the similarity in odorant concentrations sorbed into the olfactory epithelium at a constant fraction of the odorant's vapor pressure.     

NPs vs. MDs

The cardioprotective effect of cytochrome c preparations was evaluated according to the test for restriction of the size of the myocardial infarct and the effect on the course of acute myocardial ischemia in acute experiments on dogs. Cytochrome c of biotechnological and animal origin and hemtetradecapeptide caused a marked decrease in the size of the myocardial necrosis in experiments on rats: from 68 +/- 4.3% in the control to 32 +/- 3.4, 46 +/- 8.3 and 44 +/- 4.7%, respectively. In dog experiments the cytochrome c agents reduced the intensity of dp/dt decline and decreased the collateral coronary blood flow in acute myocardial ischemic. They produced a beneficial effect on heart bioenergetics, namely, reduced the lactate level in blood flowing from the zone of the ischemia and glucose consumption by the ischemic myocardium. The cardioprotective effect of biotechnological cytochrome c hemtetradecapeptide was practically identical to the effect of the enzyme of animal origin.     

Effects of Pt incorporation on the isothermal oxidation behavior of chemical vapor deposition aluminide coatings

The effects of Pt incorporation on the isothermal oxidation and diffusion behavior of low-sulfur aluminide bond coatings were investigated. Aluminide (NiAl) coatings and Pt-modified aluminide (Ni,Pt)Al coatings were synthesized on a low-sulfur, yttrium-free single-crystal Ni-based superalloy by a high-purity, low-activity chemical vapor deposition (CVD) aluminizing procedure. The isothermal oxidation kinetics and scale adhesion behavior of CVD NiAl and (Ni,Pt)Al coatings before and after isothermal oxidation were determined by electron microprobe analysis. Platinum did not reduce oxide-scale growth kinetics. No significant differences in bulk refractory metal (W, Ta, Re, and Mo) distributions were observed as a result of Pt incorporation. Spallation of the alumina scale and the formation of large voids along the oxide-metal interface were commonly observed over the NiAl coating grain boundaries after 100 hours at 1150 °C. In contrast, no spallation of Al₂O₃ scales occurred on (Ni,Pt)Al coating surfaces or grain boundaries, although the sulfur content in the CVD (Ni,Pt)Al coatings was higher than that of the CVD NiAl coatings. Most significantly, no voids were observed at the oxide-metal interface on (Ni,Pt)Al coating surfaces or cross sections after 200 hours at 1150 °C. It was concluded that a major beneficial effect of Pt incorporation on an aluminide coatings oxidation resistance is the elimination of void growth at the oxide-metal interface, likely by mitigation of detrimental sulfur effects.     

Curettage vs. hysteroscopic resection

The aim of the present study was to evaluate the therapeutic efficacy of curettage vs hysteroscopic resection in the treatment of endometrial polyps. A group of 25 patients were examined and during surgery underwent diagnostic hysteroscopy, curettage of the uterine cavity, control hysteroscopy and resectoscopy in the event of residual polyps. Thirteen cases revealed the total persistence of the polyp after curettage and in 6 cases the polyp was only partially removed; the polyp was detached but not removed from the uterine cavity in 4 cases and the polyp was fully removed using the curette in only 2 cases. The considerable limits of curettage which emerge from this study appear to be linked to three main factors: the localization, nature and size of endometrial polyps. Curettage may therefore now be considered a method which has been surpassed in not only diagnostic but also therapeutic terms by hysteroscopic techniques.     

Data vs. Capta or Sumpta.

In a recent book called Becoming, Gordon Allport points out that there are two approaches to psychology which historically have been called empiricism and rationalism and which he prefers to designate as Lockean and Leibnitzian. The former put the emphasis on the external world and described the human mind as essentially passive; the latter stressed the activity of the individual rather than the environment. With considerable philosophical insight, Allport showed that American psychology followed the leadership of British empiricism-behaviorism and operationalism are good examples of it. The rational position has been more current in Europe. In the psychology of personality, the Leibnitzian position has slowly gained some prominence. But despite the emphasis we are putting on the self and its creative nature, the terminology we use unfortunately is the old language of empiricism. When the word data is used, whether the writer is trying to emphasize what is empirically given or what is phenomenally taken is uncertain. This article recommends a different terminology for the phenomenologist. One might use the word capta for that which is taken from experience or sumpta for that which one takes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cell yield. ThinPrep vs. cytocentrifuge

The results of treatment of severe respiratory distress syndrome in premature infants with gestational age < or = 32 weeks are reported. During the two-year period 1991-92, the department participated in both the Osiris study (Exosurf) and the Curosurf 4 study (Curosurf). Five of the 23 infants treated with Exosurf died and 16 survived without major sequelae. 14 of the 25 infants treated with Curosurf died and six survived without major sequelae. Four of the infants treated with Curosurf developed severe retinopathy of prematurity. During the study period this complication occurred in one additional patient who was not eligible for inclusion in the study. The results show the need to study differences in the physiological effects of surfactants more closely, in order both to improve the basis for selection of surfactant for individual patients, and to define the indications for treatment. The results raise the question of whether such studies should continue to include control patients.     

铁纤维对气相沉积碳材料生长和形貌的影响

化学气相沉积法制备的纳米碳材料（碳纳米管，碳纤维）的生长和形貌取决于其制备工艺条件，包括催化剂的组成，制备温度，碳源的种类等。以铁纤维为催化剂、甲烷为碳源气体、在不锈钢基底上制备碳材料后，通过扫描电子显微镜分析和考察铁纤维对产物的生长和形貌的影响。研究发现：在有铁纤维的位置，甲烷裂解生成的活性碳原子移动形成的碳层成为生长内核，生成直径为100-300nm的碳纳米管；在没有铁纤维的位置，含有硅元素的小质点成为形核点，生成直径为1～2μm的碳纤维。     

Porcine aortic wall flexibility. Fresh vs Denacol fixed vs glutaraldehyde fixed

It has been postulated that, in theory, stentless bioprosthetic heart valves provide improved hemodynamics and durability over their stented counterparts. A number of glutaraldehyde modified porcine stentless valves are currently either on the market or in clinical trials. Polyepoxy compound as an alternative cross-linking reagent to glutaraldehyde for bioprostheses has been reported to mitigate calcification. The present study was to investigate the effect of the fixation methods on porcine aortic wall flexibility. Ring specimens were selected from three groups of porcine roots: fresh, low pressure glutaraldehyde fixed, and low pressure Denacol (polyepoxy compound) fixed. Pulled between two rods on a tensile tester, a ring specimen's load-deformation relationship was recorded and analyzed to numerically compute the tissue modulus at low strains. The results showed that the Young's moduli were 0.113 +/- 0.036, 0.494 +/- 0.113, and 1.320 +/- 0.292 MPa (mean +/- SD, n = 10) for the fresh, Denacol fixed, and glutaraldehyde fixed aortic walls, respectively. The Denacol fixed aortic wall was more flexible than the glutaraldehyde fixed one. It was also found that the Denacol fixed aortic wall maintained most of the natural residual strains, while the glutaraldehyde fixed aortic wall did not.