Nitridation reaction of aluminum powder in flowing ammonia

AlN powder was prepared by the nitridation of metal Al in flowing NH₃. The effects of reaction temperature and the temperature gradient of the reaction zone on the nitridation of Al were investigated. Comparative analysis of products formed in different reaction zones and reaction temperatures suggested that the nitridation reaction of liquid Al particles in flowing NH₃ was through the following mechanisms: NH₃ dissociated into reactive nitrogen (N) and hydrogen (H) radicals at the surface of Al particles. N reacted with Al to form AlN, while H promoted the decomposition of NH₃, which provided enough energy for the dissociation of NH₃. All of the experimental results had been discussed on the basis of this model, which indicated high reaction temperature or positive temperature gradient was favorable for the nitridation of Al.     

化妆品用超细结晶蚕丝粉末的制备及表征

用质量分数为85%的磷酸催化水解桑蚕茧,茧与磷酸的质量体积比为1∶4时,在100℃条件下反应,可制得平均粒径为250 nm的结晶性丝粉,收率达70%以上.并对样品进行了扫描电镜、示差热分析、X-射线粉末衍射等表征分析.     

无氟结晶器保护渣结晶矿相研究

实验室自制无氟渣,其熔化温度为1034℃,结晶温度为950℃,满足裂纹敏感性弱的钢种高速连铸的要求,并利用AX IOPLAN万能显微镜和PH ILPS PW 1700型X射线衍射仪对该无氟实验渣的结晶矿相进行了研究分析,结果表明,结晶矿相为黄长石,实际上是铝黄长石(Ca2A 2lS iO7)、镁黄长石(Ca2M gS i2O7)和钠黄长石(N aCaA lS i2O7)的固溶体,其中以镁黄长石为主,通过调整渣膜中黄长石的析晶率,同样可控制结晶器与坯壳间的传热,从而解决无氟渣冷凝过程中因不能析出枪晶石而无法控制传热的问题。     

Formation and Photoreaction of PbI2, HgI2, and BiI3 Layered Ultrasmall Particles

Formation of ultrasmall particles of PbI₂ in methanol was observed by means of stroboscopic stopped-flow spectroscopy. Pulse-laser induced electron transfer from PbI₂, HgI₂, and BiI₃ to viologens was measured for various laser intensities and for various viologen concentrations. The electron transfer yields were 0.24, 0.08, and 0.03 for HgI₂, PbI₂, and BiI₃, respectively. The laser-intensity dependence differed from the previous observation for CdS and showed that the low yield is not attributable to the direct electron-hole recombination in the particle.     

Exfoliated and intercalated polyamide-imide nanocomposites with montmorillonite

Polyamide-imide (PAI) is a high performance condensation polymer, which has high heat resistance and high radiation resistance. Solvent suspensions of PAI are widely used in magnetic wire coatings. Montmorillonite (MMT) nanocomposites were investigated for the concentration effects on dispersion, glass transition, degradation, and mechanical properties. Samples were prepared using a controlled torque stirrer and slow solvent extraction was followed for the cast samples. Optical microscopy shows that the surface of the cast sample has increased edge-edge clay platelet attraction. Transmission electron microscopy of the through thickness sample indicated platelet edges, increased face-face coagulated states and some edge-edge flocculated states of tactoid formation. X-ray diffraction indicated that for 1% sample a highly exfoliated structure was obtained while between 1.5 and 3% intercalated and exfoliated dispersions were obtained. The glass transition was not significantly affected by clay presence but a drop in specific heat change was observed for all samples showing a 001 clay peak presence. The first heating scan showed PAI solvent and MMT organic emission but these emissions did not affect the PAI chemically. Degradation was altered by the level of matrix shielding by the clay. Hardness values were increased with clay presence but unaffected by concentration.     

粉状磷酸一铵装置液氨气化系统技术改进

随着粉状磷酸一铵装置产能的扩大,液氨气化系统出现热效率低、操作复杂等问题。对粉状磷酸一铵装置液氨气化系统从工艺、设备、理论消耗计算等方面就用蒸汽气化代替用热水气化进行可行性研究分析。通过对液氨气化系统进行改进,用U型管换热器替代固定管板式换热器,提高了蒸汽利用率,减少了热量损失,气化液氨的蒸汽消耗下降了9.15%。可以进一步降低生产成本。     

配合物[BiI3（5-NH2-phen）（DMAC）]n的合成与晶体结构

用溶液挥发法合成了一个新的配合物[Bi I3(5-NH2-phen)(DMAC)]n(phen=1,10-phenanthroline),并通过X-射线单晶衍射仪对其进行结构表征。化合物1属于单斜晶系,P21/n空间群,a=8.3181(17)?,b=17.621(4)?,c=15.374(3)?,β=96.16(3)°,V=2240.4(8)?3,Z=4。相邻的簇与簇之间通过π-π堆积和氢键作用形成二维超分子网状结构。     

Comparing the caking behaviours of skim milk powder, amorphous maltodextrin and crystalline common salt

This work examined and compared the caking behaviour of three physically and chemically different food powders. The food powders studied were maltodextrin DE21 which is an amorphous powder, common salt which consists of crystalline NaCl, and skim milk powder (SMP) which contains a mixture of components including 51% lactose. The three powders were all exposed to high relative humidities (76% or 100%) over a 1-week period and to a humidity cycle to investigate their caking behaviour and interpret their caking mechanisms. The humidity cycle consisted of 2-day exposure to a high relative humidity (RH) followed by 2-day exposure to low RH of 11% and finally 2-day exposure to the original high RH. At the end of each day, cake strength was measured using a force displacement tester and cake water content was also measured. All three powders sorbed much water when exposed to high relative humidities; however, their cake strengths were very different. Cake strength was influenced by glass transition and the ability of the powders to form sinter bridges. All three powders had similar water content profiles during the humidity cycle with water gain at high RH and loss at low RH. The cake strength profile of the amorphous maltodextrin powder and amorphous SMP were different even though the maltodextrin and lactose glass transition temperatures were reduced below the powder temperature during exposure to high RH. The cake strength of maltodextrin decreased during low RH exposure while it increased for SMP. The cake strength profile of the SMP was similar to the crystalline NaCl. The paper presents an interpretation of the caking mechanisms behind the caking behaviour of each powder.     

A comparison of the electrochromic properties of WO3 films intercalated with H+, Li+ and Na+

The electrochromic response of W03 thin films under electrochemical insertion from nonaqueous electrolytes of one of the three different ions: protons, lithium and sodium cations is reported. In spite of the common belief that the nature of the ion does not change the electrochromic effect, we show that the sample colouring and bleaching are dependent on the intercalant ion and on the insertion rate. The facile insertion of protons is responsible for the highest optical contrast and the quickest response time of this intercalation electrode. Lithium and sodium-intercalated electrodes do not show large optical difference from the proton-intercalated tungsten trioxide unless large charging currents are used. Subtle changes in electrochromic efficiency and in the optical contrast in the red part of the spectrum can be detected; these are larger for the sodium than for the lithium intercalant. According to our analysis, the slow insertion kinetics of Na⁺ and the formation of a new M _x WO₃ (M=Li, Na) compound is responsible for most of the observed differences.     

磷铵洗氨生产浓氨水工艺介绍

介绍了焦炉煤气脱氨技术,磷铵洗氨生产浓氨水工艺与其他煤气脱氨工艺相比较,所产浓氨水纯度高,且浓氨水应用广泛,工艺经济效益较好,目前已经实现国产化设计。     

Preparation and properties of pure crystalline perovskite CeFeO3 thin films with vanadium doping

Cerium ferrite (CeFeO₃) thin films doped with vanadium (V:CeFeO₃) were grown on SiO₂ quartz glass and <100>‐oriented SrTiO₃ (STO) crystal substrates by the radio‐frequency magnetron sputtering method in this study. The effects of crystallization, substrate, and V‐doping on the quality, the magnetic property and the magneto‐optical property of as‐prepared films are investigated. V:CeFeO₃ film grown on STO substrate has better crystallinity and has better lattice integrity due to the higher lattice matching between substrate and film. The magnetic hysteresis loop and the magnetic circular dichroism spectra show that the magnetization strength and the magneto‐optical properties of V:CeFeO₃ films have the significant anisotropy. Moreover, V‐doping and the stress lead to the change in easy magnetization direction of film. It shows that the perovskite B‐site doping with transition‐metal ion has significant influence on the magnetic and the magneto‐optical properties of CeFeO₃ thin films.     

Liquid crystalline thermosets as binder for powder coatings: Thermoanalytical study of the cure characteristics of a carboxylated main chain liquid crystalline oligoester

The curing behavior of a liquid crystalline oligoester (LCO), based on 4,4′-diacetoxybiphenyl and dodecanedioic acid, as a model resin for powder coatings, in presence of triglycidyl isocyanurate (TGIC), as a curing agent, was studied by isothermal differential scanning calorimetry (DSC). The analysis of isothermal data was performed using the model-free isoconversional method. Activation energy as a function of extent of conversion, , has been calculated by the Friedman technique. It showed an ascending trend from about 133.7 kJ/mol, at =0.1 to 177.2 kJ/mol, at =0.4, then it reached approximately a constant value of about 150±5% kJ/mol in the range of 50–90%.

The results indicated that the kinetic process does not follow a single-step curing reaction model. To verify the isothermal analysis result, we carried out further, non-isothermal differential scanning calorimetry and depolarizing transmittance measurements on the stoichiometric mixture of LCO/TGIC, at different heating rates. The results of these experiments exhibited that the kinetic process of the investigated system is strongly influenced by curing condition which alters the liquid crystalline state of the sample.     

Nanodiamonds intercalated with metals: structure and diamond-graphite phase transitions

We used X-ray diffraction, small-angle X-ray scattering, and scanning electron microscopy (SEM) to study the diamond graphite phase transition in detonation nanodiamond (ND) intercalated with Cu, Ni, Co and Fe for the first time. The study has been made before and after annealing in hydrogen and argon. The SEM data obtained support the idea of the hierarchic structure of ND with a size of primary cluster of about 5 nm. There are several levels of aggregation of primary clusters. We have shown that all the samples of ND are surface fractals. It means the structure can be characterized by three parameters: coherent scattering region (CSR), the size of scatterer A and fractal dimensionality D.The transition degree was identified by X-ray diffractometry from the peaks of bulk nanographite. Scanning electron microscopy was used to determine the sizes of metallic and carbon aggregates. We have found from the CRS, A and D data that the intercalation does not practically change the diamond core at annealing in hydrogen and its size is similar to that reported earlier. However the changes of the scatterer size and fractal dimensionality depend on type of intercalated metals in hydrogen annealing.     

Organoclay/thermotropic liquid crystalline polymer nanocomposites. Part VI: Effects of intercalated organoclay on nanocomposite morphology,thermal and rheological properties

A study of a typical intercalated structure of a thermotropic liquid crystalline polymer (TLCP) with organoclay was performed to elucidate the influence of intercalated organoclay on the TLCP molecules, especially on their liquid crystallinity, thermal and rheological properties. The intercalated structures were confirmed in TLCP and organoclay formed molecular interactions with TLCP molecules in the system. Such intercalated structures caused the glass transition temperature of the nanocomposite to become invisible in thermal measurement and also caused loss of liquid crystallinity. The TLCP molecules inside the organoclay galleries showed higher thermal stability and transition temperatures, but the orderly structure of the TLCP molecules outside the galleries was destroyed by the organoclay, causing the TLCP to display lower thermal stability and transition temperatures than pristine TLCP. At 185°C, where TLCP is in the nematic phase, the nanocomposite had three orders of magnitude higher viscosity in the linear viscoelastic region than that of TLCP, with chain mobility and relaxation time slowed due to the intercalated effects in the nanocomposite. Steady shear altered the domain sizes and oriented the highly anisotropic organoclay layers or tactoids along the shear direction.     

Study on reduction reaction of MoO2 powder with NH3

Reaction mechanism between MoO₂ powder and NH₃ in the temperature range of 1028‐1273 K has been investigated. The results show that reduction products are strongly dependent on the reaction temperature employed. It is found that molybdenum nitride (Mo₂N) can be successfully synthesized when the temperature is below 1078 K, with the morphologies keep the same as that of the raw material MoO₂. Although the temperature is above 1078 K, metal Mo powder will be turned up; at the even higher temperatures, the thermodynamically stable phase will be metal Mo. In addition, MoO_xN_1?x as an intermediate product is formed during the reduction processes.