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1.
对含稀释剂A12O3和Cr2O3的A1-Cr2O3体系燃烧合成反应进行了热力学计算与分析,讨论了起始反应温度T0、稀释剂A12O3和Cr2O3的含量对绝热反应温度Tad的影响,并得出T0与Tad在特定温度段上的近似线性关系以及该关系在指导材料成分设计上的应用;揭示了反应驱动力——GibbS自由能(△G)随反应温度(T)的变化关系,得出该体系的反应为扩散控制型反应;结合实验结果与分析,描述了该体系热爆反应的微观模型。  相似文献   

2.
用Ni(OH)2浆化氢还原法制备纳米金属镍粉的反应机制   总被引:12,自引:0,他引:12  
用Ni(OH)2浆流水热氢还原法制备了纳米金属镍粉,通过对不同反应阶段样品性质的分析,研究了反应机制,结果表明,在酸性条件下,通过复盐离解出的镍离子在溶液中与氢发生反应,在碱性条件下,Ni(OH)2固体颗粒直接与活性氢发生反应。  相似文献   

3.
刘建科  解晨  朱建锋  叶兰 《功能材料》2015,(7):7143-7147
以Ti、TiC、Al和TiO2为原料,通过原位热压反应烧结法在1 350℃合成Ti2AlC/Al2O3复合材料。利用XRD详细研究了其反应过程,并分析了Al2O3对材料微观结构和性能的影响。结果表明,该体系在热压过程中的反应分多步进行,主要包括Ti粉与Al粉反应生成Ti-Al金属间化合物,TiO2与Al反应生成Al2O3以及Ti-Al金属间化合物与TiC反应生成Ti2AlC材料。原位反应生成的Al2O3均匀分布在Ti2AlC晶界上,抑制了Ti2A1C晶体的异常生长,从而使基体相Ti2AlC晶粒细小、均匀。力学性能测试表明Ti2AlC/12%(质量分数)Al2O3复合材料的硬度、抗压强度、抗弯强度和断裂韧性较Ti2AlC单相材料分别提高了66%,126%,130%和19.3%,并分析了其改性机理。  相似文献   

4.
以氨水为沉淀剂,采用共沉淀法按一定比例分别制备了ZrO2-Al2O3-CeO2、ZrO2-Al2O3-CeO2、ZrO2-Al2O3-CeO2等4种前驱复合粉体。利用差热-热重分析(DTA/TG)和X射线衍射(XRD)对4种粉体的热转变过程以及不同温度煅烧后的物相组成进行了对比分析,研究了ZrO2-Al2O3-CeO2复合粉体间在煅烧过程中的化学反应及相互影响。结果表明:CeO2与ZrO2优先形成固溶体,CeO2与Al2O3直到1300℃也未发生任何反应;Al2O3的存在明显提高了c-(Ce,Zr)O2的结晶温度,1300℃退火后t-(Ce,Zr)O2仍能保留到室温。  相似文献   

5.
二氧化钛-二氧化硅复合材举制备研究及应用   总被引:2,自引:0,他引:2  
对TiO2-SiO2复合材料的的制备方法进行了综述,同时讨论了在化妆品、涂料、食品抗菌、光催化、亲水薄膜等方面的应用,总结了针对不同的使用目的进行的TiO2包覆SiO2、TiO2包覆SiO2、TiO2与SiO2相互交联反应,并对其机理和应用进行了简单的介绍。  相似文献   

6.
ZrO2氧敏陶瓷在汽车发动机、电厂等燃烧设备、高温冶炼、环保与计量等方面有着重要的作用。本文综述了ZrO2氧敏陶瓷的导电与反应机理,指出了此浓差电池型材料在制备与应用过程中的影响因素,并对近年来ZrO2氧敏陶瓷材料的研究进展及存在的问题进行了分析,指出了发展方向。  相似文献   

7.
通过分部固相法制备ZrW2O8粉体。以ZrW2O8、CuSO4·5H2O(分析纯)和无水Na2CO3(分析纯)为原料,采用非均匀沉淀法制备了Cu包覆ZrW2O8复合粉体,并利用XRD、SEM、EDS测试手段,分析包覆粉的物相和形貌,研究了反应液浓度、表面活性剂、反应液滴加速度等反应条件对包覆效果的影响。研究表明:通过非均匀沉淀法可以制备Cu包覆ZrW2O8复合粉体,其关键是控制反应液的浓度和滴加速度,同时,不同分子量的表面活性剂对包覆前驱体的分散性影响很大.  相似文献   

8.
以P2O5与CaF2为原料,采用加热的方法制备PF5气体,并研究了反应温度、反应时间及P2O5和CaF2质量比对PF5产率的影响。结果表明,制备PF5的最佳条件:反应温度控制在280-300℃,反应时间5h,PF5和CaF2质量比为2.5:1。  相似文献   

9.
Al-Ti-TiO2体系燃烧合成及其反应过程研究   总被引:9,自引:0,他引:9  
利用Al-Ti-TiO2体系放热反应,采用自蔓延高温合成工艺,原位合成了TiAl基体和Al2O3颗粒,成功制备出TiAl/Al2O3复合材料。结合差热分析,通过对不同温度下反应产物相组成分析,对Al-Ti-TiO2体系燃烧反应过程进行了初步研究。结果表明,铝热还原反应是一个分步过程,先期发生的Al-Ti,Ti-TiO2反应降低了Al-TiO2还原反应的起始温度。  相似文献   

10.
Q235钢表面反应火焰喷涂TiB2/Mo2FeB2复相陶瓷涂层的耐蚀性   总被引:1,自引:0,他引:1  
马壮  潘锐  李智超  董世知  王伟 《材料保护》2011,44(12):57-59
为了研究TiB2/M02FeB2复相陶瓷涂层的耐蚀性,以Mo粉、FeB粉、Fe粉及TiB2粉为原料,采用反应火焰喷涂技术在Q235钢上制备了TiB2/Mo2FeB2复相陶瓷涂层。采用x射线衍射仪(XRD)、扫描电镜(SEM)分析了粉体和涂层的物相组成与表面形貌,通过浸泡法测试了涂层耐蚀性。结果表明:涂层内含硬质相TiB...  相似文献   

11.
真空膜蒸馏技术可用于分离水溶液中的有机挥发性化合物(VOCs),是一种治理遭受VOCs污染工业废水的新方法.对低浓度乙醇水溶液二元体系下的真空膜蒸馏过程展开了模拟分析,膜内的传质按Knudsen扩散原理考虑,界面上的平衡关系按Van Laar活度系数法给出.模拟结果表明:过程的操作参数对分离效率有较大的影响,进口温度、料液流量、浓度和真空度增加,膜通量将增加;分离因子随进口温度、真空度、浓度增加而减少,料液流量对分离因子影响与真空侧流动形式有关.真空侧流动形式对分离因子有一定的影响,并流条件下,分离因子最大.  相似文献   

12.
The degradation of a model molecule, 2,4-dichlorophenol (2,4-DCP), was studied using an activated sludge hydrolytic–aerobic recycling process (HARP). 2,4-DCP and chemical oxygen demand (COD) total removal efficiency in the recycling process was 98% and 96% at the recycling flux of 15 mL/min after 24 h degradation, respectively. With the recycling flux increasing, the peak values of the concentration of volatile fatty acid (VFA) declined. Polysaccharide and protein contents in EPS were dramatically increased as recycling flux increasing from 5 to 15 mL/min in the HARP. There is obviously fit to the linear correlation between the PN/PS ratios and recycling flux. The zeta potentials decreased with recycling flux increasing. As the recycling flux increasing at a certain degree, the increase in polysaccharide and protein contents of EPS could more favor the stability of the HARP.  相似文献   

13.
Given the time scale of biological, biochemical, biophysical and physical effects in a radiation exposure of living tissue, the first physical stage can be considered to be independent of time. All the physical interactions caused by the incident photons happen at the same starting time. From this point of view it would seem that the evolution of photon tracks is not a relevant topic for analysis; however, if the photon track is considered as a sequence of several interactions, there are several steps until the total degradation of the energy of the primary photon. We can characterise the photon track structure by the probability p(E,j), that is, the probability that a photon with energy E suffers j secondary interactions. The aim of this work is to analyse the photon track structure by considering j as a step of the photon track evolution towards the total degradation of the photon energy. Low energy photons (<150 keV) are considered, with water phantoms and half-extended geometry. The photon track evolution concept is presented and compared with the energy deposition along the track and also with the spatial distribution of the several steps in the photon track.  相似文献   

14.
A continuously stirred hydrogen-based membrane biofilm reactor (MBfR) with polyvinyl chloride (PVC) hollow fiber membrane was investigated for removing 2-chlorophenol (2-CP) from contaminated drinking water. The bioreactor startup was achieved by acclimating the microorganisms from a denitrifying and sulfate-reducing MBfR to the drinking water contaminated by 2-CP. The effects of some major factors, including 2-CP loading, H(2) pressure, nitrate loading, and sulfate loading, on the removal of 2-CP by the MBfR were systematically investigated. Although the effluent 2-CP concentration increased with its increasing influent loading, the removing efficiency of 2-CP by the MBfR could be up to 94.7% under a high influent loading (25.71 mg/L d). The removing efficiency of 2-CP by the MBfR could be improved by higher H(2) pressure, and lower influent nitrate concentration and sulfate concentration. A high H(2) pressure can assure enough available H(2) as the electron donor for 2-CP degradation. The competition in the electron donor made nitrate and sulfate inhibit the degradation of 2-CP in the MBfR. The electron flux analyses indicated that the degradation of 2-CP only accounted for a small part of electron flux, and the autohydrogenotrophic bacteria in the MBfR were highly efficient for the 2-CP removal.  相似文献   

15.
Carbon containing C_TiO2 nanoparticles with rutile mass fractions about 20%, carbon mass fractions from 0-22%, having normal size distributions with mean sizes from 24-62 nm are synthesized by the oxidation of TiCl4 in industrial propane/air diffusion flame. Photodegradation of VOCs of formaldehyde, benzene, toluene and methanol by the C_TiO2 nanoparticles have been investigated by using a tubular photoreactor with C_TiO2 thin films coated on the wall of the tubular reactor by a sedimentation method. Effects of effective thickness of C_TiO2 thin films from 60-150 nm, relative humidity from 8-100%, and initial concentration of VOCs loaded air stream from 0.06-3 g/m3 on degradation degree have been investigated. Comparisons are made on degradation degree between the C_TiO2 nanoparticles and P25 photocatalyst and the results show that the photocatalytic activity of the C_TiO2 nanoparticles and P25 are comparative.  相似文献   

16.
Kirk JT 《Applied optics》1999,38(15):3134-3140
It is shown that where mu (s) is the average cosine of scattering, then for any set of photons that undergoes exactly n scatterings per photon, the average cosine after scattering is mu (0)mu (s)(n), where mu (0) is the average cosine of the photon flux before scattering. For a set of photons that has traversed distance d through a medium with scattering coefficient b, the average cosine is mu (0) exp[-bd(1 - mu (s))]. For water bodies in which loss of upward-scattered photons through the surface is small enough to be disregarded, the value of mu (c) (the average cosine of all the photons instantaneously present in the water column) for any given incoming flux of photons with average cosine mu (0) is determined entirely by the inherent optical properties of the water in accordance with mu (c)= mu (0)/[1 + (b/a)(1 - mu (s))], where a and b are the absorption and scattering coefficients.  相似文献   

17.
Dynamic and flow-through flux chambers are convenient tools for field measurements of gas or VOC emission flux from solid surfaces in the field. This study was undertaken to collect on site and quantify the emissions of volatile organic compounds (VOCs) released from athletic running tracks. Three typical types of tracks, one synthetic rubber and two tracks (types I and II) consisting mainly of polyurethane, were studied. They were all installed with adhesives and backings, both of which contributed significant amount of VOCs. VOCs released from the track surface were collected with a flux chamber and subsequently analyzed by a gas chromatograph/mass spectrometer (GC/MS). Also, for each track and at each selected time the emission flux and mass emission were measured on site under outdoor conditions over a period of 40 min. GC/MS analyses show that the VOCs emitted include 2-methyl furan, butanal, methyl ethyl ketone, benzene, heptane, methyl isobutyl ketone, toluene+octane, hexanal, nonane+ethylbenzene, xylenes+styrene, propyl benzene, decane, 1,3,5-trimethyl benzene, 1,2,4-trimethyl benzene, 1,2, 3-trimethyl benzene and undecane. Of these, hexanal was the common and principal compound for all three types of tracks. 2-Methyl furan and methyl isobutyl ketone were the characteristic compounds for the synthetic rubber and the type II of polyurethane tracks, respectively. In the field studies, no unique compounds were found in the type I of polyurethane tracks. For each of these three types of tracks the total-VOCs emission flux was correlated to the track age and track surface temperature. The results of multiple regression analysis showed good correlation. The type II polyurethane track had the highest decay rate, while the synthetic rubber track had the lowest decay rate. Two years after the track installation, the VOC concentrations measured at 1.5 m above the track, the breathing height of school children, were not significantly higher than the background levels.  相似文献   

18.
The aim of this study is to obtain by Monte Carlo method the high energy photon flux due to neutron capture in the internals and vessel layers of the experimental reactor LR-0 located in REZ, Czech Republic, and loaded with VVER-1000 fuel. The calclated neutron, photon and photon to neutron flux ratio are compared with experimental measurements performed with a multi-parameter stilbene detector. The results show clear underestimation of photon flux in downcomer and some overestimation at vessel surface and 1/4 thickness but a good fitting for deeper points in vessel.  相似文献   

19.
We describe a noniterative method for recovering optical absorption coefficient distribution from the absorbed energy map reconstructed using simulated and noisy boundary pressure measurements. The source reconstruction problem is first solved for the absorbed energy map corresponding to single- and multiple-source illuminations from the side of the imaging plane. It is shown that the absorbed energy map and the absorption coefficient distribution, recovered from the single-source illumination with a large variation in photon flux distribution, have signal-to-noise ratios comparable to those of the reconstructed parameters from a more uniform photon density distribution corresponding to multiple-source illuminations. The absorbed energy map is input as absorption coefficient times photon flux in the time-independent diffusion equation (DE) governing photon transport to recover the photon flux in a single step. The recovered photon flux is used to compute the optical absorption coefficient distribution from the absorbed energy map. In the absence of experimental data, we obtain the boundary measurements through Monte Carlo simulations, and we attempt to address the possible limitations of the DE model in the overall reconstruction procedure.  相似文献   

20.
The second law, the Planck equation, and the Gibbs-Duhem relation are used to deduce intrinsic thermodynamic properties of individual photons. It is found that intrinsic photon entropy is independent of the photon wavelength. The intrinsic entropy flux associated with individual photons supplements the entropy flux obtained from standard statistical mechanics. Implications of intrinsic photon entropy for isolated photon systems, a fundamental Planck temperature, and the net photon production of the earth are discussed.  相似文献   

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