Water Vapor Adsorption Properties of Amorphous Cefditoren Pivoxil Evaluated by Adsorption Isotherms and Microcalorimetry

Water vapor adsorption of ground cefditoren pivoxil was studied. The amount of water adsorbed increased with a decrease in the crystallinity of cefditoren pivoxil. It was found from the microcalorimetric measurements that the differential heat of water vapor adsorption at 1.5% adsorbed water increased with decreasing crystallinity of cefditoren pivoxil, suggesting that hygroscopicity of cefditoren pivoxil was enhanced by grinding. These results indicated that hydrophilic adsorption sites in cefditoren pivoxil increased through the grinding process. The results of infrared (IR) spectra examination suggested that the increment of hydrophilic adsorption sites through the grinding process resulted from the change of the environment of the carbonyl groups in two esters and amide.     

Adsorption isotherms and heats of adsorption of hydrogen,neon and nitrogen on activated charcoal

The results of measurements of adsorption isotherms of hydrogn, neon and nitrogen on charcoal in the temperature range of 77 K to 400 K and the pressure range of 1 atm to 80 atm are given. The heats of adsorption were calculated from the measured isotherms. The isotherms were fitted to a semi-empirical generalized expression of the type

$\text{C =}\text{M}\text{b}\text{α}\text{exp}\text{(?γx)}$

It was found that within the experimental uncertainty, the expression was a fairly good representation of the isotherm data for these pressure and temperature ranges, if an appropriate potential function x was chosen for the correlation. The heats of adsorption derived from the generalized equations compared well with the experimental data.     

吸油烟树脂的制备及其性能的研究

采用悬浮法制备了一系列憎水性、高比表面积的多孔树脂,讨论了交联剂用量、致孔剂用量和组成对多孔树脂的吸油烟性能的影响.结果表明,当采用10份质量的DMA作为反应单体,采用90份质量的TRIM作为交联剂,采用100质量的致孔剂(其中甲苯为90份质量,正庚烷为10份质量)时所制得的多孔树脂的吸油烟率最大,达到0.305g/g...     

Thermal crystallization kinetics and crystallite size distribution of amorphous ITO film deposited in the presence or absence of water vapor

The isothermal crystallization process of amorphous indium tin oxide films was investigated by examining the peak intensity, obtained through high-temperature X-ray diffraction analysis. The introduction of water vapor (5 × 10^− 5 Torr) during sputtering-deposition significantly reduced the rate of crystallization. This can be attributed to the presence of chemically bonded hydrogen. Classical kinetic analysis based on the Kolmogorov-Johnson-Mehl-Avrami equation indicated three distinct changes caused by the introduction of water vapor: it reduced the kinetic exponent (n) from approximately 5/2 (2.59 ± 0.12) to 3/2 (1.53 ± 0.10), increased the activation energy (E_a) from 79.9 to 116 kJ/mol, and increased the average crystallite size from 54 to 93 nm. Site-saturated and continuous nucleation models are tentatively proposed, to account for the crystallization of amorphous ITO films deposited in the presence and absence of water vapor, respectively.     

Structural properties of microcrystalline Si films prepared by hot-wire/catalytic chemical vapor deposition under conditions close to the transition from amorphous to microcrystalline growth

The structural properties of microcrystalline Si films prepared by hot-wire/catalytic chemical vapor deposition, with various dilution ratios of silane in hydrogen, were investigated as regards to the role of hydrogen. A large surface roughness correlated with a low crystalline nuclei density was observed for microcrystalline Si films deposited near the transition from amorphous to microcrystalline growth. Investigations of hydrogen-related properties suggest the presence of molecular hydrogen in these films. We tentatively propose that the diffusion of atomic hydrogen into the subsurface layer of growing films, which leads to the relaxation of amorphous Si network and to the generation of molecular hydrogen, plays an important role for determining the film properties, besides top surface reactions.     

Structure and properties of laser-cladded Ni-based amorphous composite coatings

A (N_i0.6Fe_0.4)₆₅B₁₈Si₁₀Nb₄C₃ amorphous composite coating has been fabricated on a mild steel substrate by a laser cladding process under different heat inputs. Observation of the structure and phase showed that the thickness of the coating decreased and the amorphous fraction increased when the laser cladding heat input was lower. The cooling rate increases when the heat input decreases, which favours the formation of amorphous phase. Microhardness and wear resistance test results indicated that a lower heat input led to higher microhardness and better wear resistance of the coating. An average microhardness of 1187.0 HV0.2 was obtained with a heat input of 69?J?mm^–1.     

Hydrogenated amorphous carbon and carbon nitride films deposited at low pressure by plasma enhanced chemical vapor deposition

Hydrogenated amorphous carbon (a-C:H) films were deposited by plasma enhanced chemical vapor deposition from methane, argon diluted methane, and nitrogen diluted methane at 26.7 Pa with a 13.56 MHz RF power supply. In this pressure regime, multiple-scattering of carbon species within the plasma phase is expected during the transport to the substrates placed on both the driven and the earthed electrodes. These films were analyzed using UV-VIS optical transmittance, monochromatic ellipsometry, Raman spectroscopy and current-voltage measurements. From these results, the effect of the plasma conditions and the effective flux of the carbon species controlled by the input power through the negative self bias are found to be important in the deposition process. The growth conditions at the higher pressure regime are important to synthesize a-C:H films from low energetic carbon species, since it reduces the defect density and improves the quality of the films. Furthermore, the effect of nitrogen on the growth conditions of a-C:H:N films is observed.     

Cold deposition of large-area amorphous hydrogenated silicon films by dielectric barrier discharge chemical vapor deposition

Amorphous hydrogenated silicon films were deposited on glass substrates at room temperature. This cold deposition process was operated in a dielectric barrier discharge CVD reactor with a fixed strip-shaped plasma matched with a moving substrate holder. The maximum film area was 300 × 600 mm². The film deposition rate as a function of applied peak voltage of DBD power was investigated under different hydrogen-diluted silane concentrations, and the film surface smoothness, continuity, and film/glass adherence were also studied. The maximum deposition rate was 12.2 Å/s, which was performed under the applied peak voltage of 16 kV and a hydrogen-diluted silane concentration of 50%. IR measurements reveal that the silane concentration plays a key role in determining the hydrogen-silicon bonding configurations. With increasing hydrogen-diluted silane concentration, the H-Si bonding configurations shift gradually from Si-H₃ to Si-H. The variation of photo/dark conductivity ratio and optical bandgap versus hydrogen-diluted silane concentration were investigated. The use of DBD-CVD for deposition of a-Si:H films offers certain advantages, such as colder substrate, faster film growth rate, and larger deposition area. However, the consumption of silane for the DBD-PECVD procedure is much greater than for the RF-PECVD process.     

Electron-emission properties of carbon nanotube micro-tips coated by amorphous carbon nitride films

An approach to the preparation of a tip-type of field emitter that is made up of carbon nanotubes (CNTs) coated with amorphous carbon nitride (a-CN_x) films is presented for the purpose of enhancing its electron emission property. CNTs were directly grown on nano-sized conical-type tungsten tips via the inductively coupled plasma-chemical vapor deposition system, and a-CN_x films were coated on the CNTs using an radio frequency magnetron sputtering system. The morphologies and microstructures of the a-CN_x-coated CNTs were analyzed via field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy. The electron emission properties of the a-CN_x/CNT hetero-structures were measured using a high-vacuum field emission measurement system. The best field emission properties, such as a very low turn-on voltage of 500 V and a maximum emission current of 176 μA were achieved for the CNT emitter coated with the 5 nm-thick a-CN_x film. In addition, this emitter showed a highly stable behavior in long-term (up to 25 h) electron emission.     

Specific surfaces and heat of adsorption of some indian clays by dye-adsorption technique

Adsorption of basic dye methylene blue by some Indian clays has been studied. BET plotting of the adsorption isotherms was applied to determine the specific surfaces of clays and heat of adsorption. About 10–20% lower values of specific surfaces were obtained when compared with the most accurate gas-adsorption BET results and its probable reasons discussed. The calculated heat of adsorption values confirm the physical adsorption.     

Effects of argon and oxygen flow rate on water vapor barrier properties of silicon oxide coatings deposited on polyethylene terephthalate by plasma enhanced chemical vapor deposition

Plasma polymer coatings were deposited from hexamethyldisiloxane on polyethylene terephthalate (PET) substrates while varying the operating conditions, such as the Ar and O₂ flow rates, at a fixed radio frequency power of 300 W. The water vapor transmission rate (WVTR) of the untreated PET was 54.56 g/m²/day and was decreased after depositing the silicon oxide (SiO_x) coatings. The minimum WVTR, 0.47 g/m²/day, was observed at Ar and O₂ flow rates of 4 and 20 sccm, respectively, with a coating thickness of 415.44 nm. The intensity of the peaks for the Si-O-Si bending at 800-820 cm^− 1 and Si-O-Si stretching at 1000-1150 cm^− 1 varied depending on the Ar and O₂ flow rates. The contact angle of the SiO_x coated PET increased as the Ar flow rate was increased from 2 to 8 sccm at a fixed O₂ flow rate of 20 sccm. It decreased gradually as the oxygen flow rate increased from 12 to 28 sccm at a fixed Ar carrier gas flow rate. The examination by atomic force microscopy revealed a correlation of the SiO_x morphology and the water vapor barrier performance with the Ar and O₂ flow rates. The roughness of the deposited coatings increased when either the O₂ or Ar flow rate was increased.     

Effect of thermal annealing on the structural and mechanical properties of amorphous silicon carbide films prepared by polymer-source chemical vapor deposition

We report on the effect of thermal annealing on the structural and mechanical properties of amorphous SiC thin films prepared by means of a polymer-source chemical vapor deposition process. The chemical bondings of the a-SiC:H films were systematically examined by means of Fourier transform infrared spectroscopy (FTIR). The film composition was measured by X-ray photoelectron spectroscopy, while X-ray reflectivity measurements were used to account for the film density variations caused by the post-annealing treatments over the 750-1200 °C range. In addition, their mechanical properties (hardness and Young's modulus) were investigated by using the nano-indentation technique. FTIR measurements revealed that not only the intensity of a-SiC absorption band linearly increases but also its position is found to shift to a higher wave number as a result of annealing. In addition, the bond density of Si―C is found to increase from (101.6-224.5) × 10²¹ bond·cm^− 3 accompanied by a decrease of Si―H bond density from (2.58-0.46)× 10²¹ bond·cm^− 3 as a result of increasing the annealing temperature (T_a) from 750 to 1200 °C. Annealing-induced film densification is confirmed, as the a-SiC film density is found to increase from 2.36 to ∼ 2.75 g/cm^− 3 when T_a is raised from 750 to 1200 °C. In addition, as T_a is increased from 750 to 1200 °C, both hardness and Young's modulus are found to increase from 15.5 to 17.6 GPa and 155 to 178 GPa, respectively. Our results confirm the previously established linear correlation between the mechanical properties of the a-SiC films and their bond densities.     

纯无定形氧化硅纳米线热气相法制备及其光致发光性质

在氮气气氛和常压下,采用无金属催化的单步热气相法在单晶硅片上制备大量纯非晶氧化硅纳米线,采用SEM、HRTEM、EDS、XRD和荧光光谱（PL）研究氧化硅纳米线形貌、结构和光致发光性质,并分析其发光中心。结果表明1100℃可形成纳米棒,1200℃则获得光滑均匀纳米线,而1300℃得到的纳米线具有较多弯曲结构,氧化硅纳米线中硅氧原子比接近1∶2,且1300℃制得纳米线中氧含量略高于1200℃,氧化硅纳米线呈无定型态。SiO气化分解和氧化时在硅片上形成氧化硅纳米簇,成为无定形氧化硅纳米线生长的成核中心。氧化硅纳米线的两个光致发光峰值波长为467和364nm,其发光机制是纳米线生长过程中产生的不同点缺陷结构构成了蓝光和紫外光辐射复合中心。     

沙柳基磁性多孔炭的制备及其吸附亚甲基蓝性能研究

采用水热法原位改性沙柳生物炭制备磁性多孔炭复合材料,利用SEM、XRD、FT-IR、XPS和BET分别对多孔炭的形貌、结构表征,并研究磁性多孔炭吸附去除废水中亚甲基蓝性能.系列表征分析结果表明磁性复合材料表面疏松多孔,比表面积为63.01 m2/g,含有-COOH、-OH等丰富的官能团.在亚甲基蓝初始质量浓度为50 m...     

炭纤维和活性炭甲醇气相吸附动力学和等温线

采用不同原料、不同活化过程的两种活性炭和两种炭纤维(PAN、Rayon基)进行了甲醇气相静态吸附,结合其吸附动力学和等温线的数据研究了有关扩散问题,发现温度与所用样品表面化学性质、中孔率、孔隙(形态与大小)微织构对其吸附动力学有影响。     

In-vitro and in-vivo study of amorphous spironolactone prepared by adsorption method using supercritical CO2

Objective: The aim of this study was to improve the oral bioavailability of spironolactone (SP).

Method: SP was adsorbed on the fumed silica using supercritical CO₂ (scCO₂) technology and further compressed into tablets. The morphology was observed by scanning electron microscopy (SEM), and the crystalline form was investigated by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The dissolution test was performed in water, 0.1?M HCl solution, pH 4.5 acetate buffers and pH 6.8 phosphate buffers using the paddle method. The pharmacokinetics was undertaken in six dogs in a crossover fashion.

Results: SP was successfully prepared into tablets and presented in amorphous state. SP-silica scCO₂ tablets displayed higher dissolution profiles than SP-silica physical mixtures tablets in different media. The AUC_0–t and C_max of SP-silica supercritical CO₂ was 1.61- and 1.52-fold greater than those of SP-silica physical mixtures (p?Conclusion: It is a promising method in improving dissolution and bioavailability by adsorbing SP, a poorly soluble drug, on the fumed silica using rapid expansion of supercritical solutions.     

Preparation and characterization of carbon molecular sieves from chestnut shell by chemical vapor deposition

In this study, carbon molecular sieves (CMS) were produced from chestnut shell by chemical activation process followed by chemical vapor deposition (CVD) of methane. The influences of deposition temperature (800–900?°C), time (15–60?min) and flow rate of CH₄ (100–300?mL/min) on pore development of carbon molecular sieve were investigated. The produced CMSs were characterized by several techniques such as N₂ adsorption, CO₂ adsorption, CH₄ adsorption, elemental analysis, FTIR analysis and SEM analysis. The textural analysis of the CMS samples showed the successful deposition of methane on pores of the produced activated carbon derived from chestnut shell to yield a microporous CMS with a narrow pore size distribution. The deposition temperature, time and flow rate of CH₄ were shown to strongly affect the pore structure of the CMS. The maximum CO₂ adsorption capacity (525.7?mg/g) was obtained at a deposition temperature of 850?°C, time of 30?min, and CH₄ flow rate of 100?mL/min.     

Deposition of silicon doped and pure hydrogenated amorphous carbon coatings on quartz crystal microbalance sensors for protein adsorption studies

In this study hydrogenated amorphous carbon films (a-C:H) and silicon doped hydrogenated amorphous carbon films (a-C:H:Si) with different hydrogen and silicon contents were deposited onto sensors of a quartz crystal microbalance with dissipation detection (QCM-D). The resulting films were investigated with regard to their structural and elemental compositions using Raman spectroscopy, elastic recoil detection analysis and Rutherford backscattering spectroscopy. Furthermore the surface free energy (SFE) of the films was determined using contact angle measurements. The polar part of SFE of the a-C:H:Si films was found to be adjustable by the silicon content in these films and increased by increasing amounts of silicon. Carbon films with a broad range of chemical composition showed similar structure and properties when deposited on QCM-D sensors as compared with the deposition on silicon wafers. Subsequently, the amorphous carbon coated QCM-D sensors were used to study the adsorption of human serum albumin. These QCM-D results were related to the surface properties of the films.     

Magnetic and optical properties of amorphous NdFeCo thin films by pulsed laser deposition technique

Rare earth and transition metal doped (NdFeCo) thin films were fabricated on Si (100) substrate by pulsed laser deposition technique keeping the substrate at constant temperature of 300 °C. A KrF Excimer laser (248 nm, 20 ns) was used as an energy source for the deposition. Thin films were deposited without and under the influence of transverse magnetic field applied across the plume. The applied magnetic field was varied from 3 to 6 kOe. The deposited films were characterized by XRD, FESEM, VSM and SE (Spectroscopic Ellipsometry). The deposited films were amorphous in nature. All the films regardless of the applied magnetic field exhibit perpendicular magnetic anisotropy. The thickness of the thin films was found to increase monotonically from 166 to 266 nm with the increase in the applied external magnetic field. The saturation magnetization has a maximum value of 1682 emu/cc for the film deposited under 4.5 kOe magnetic field. The value of optical band gap energy for the same film is found to have a maximum value of 3.1 eV. The values of both the saturation magnetization and the band gap energy were decreased with the increase in the applied magnetic field.     

Impact of hydrogen dilution on optical properties of intrinsic hydrogenated amorphous silicon films prepared by high density plasma chemical vapor deposition for solar cell applications

P-i-n single-junction hydrogenated amorphous silicon (a-Si:H) thin film solar cells were successfully fabricated in this study on a glass substrate by high density plasma chemical vapor deposition (HDP-CVD) at low power of 50 W, low temperature of 200°C and various hydrogen dilution ratios (R). The open circuit voltage (V_oc ), short circuit current density (J_sc ), fill factor (FF) and conversion efficiency (η) of the solar cell as well as the refractive index (n) and absorption coefficient (α) of the i-layer at 600 nm wavelength rise with increasing R until an abrupt drop at high hydrogen dilution, i.e. R > 0.95. However, the optical energy bandgap (E_g ) of the i-layer decreases with the R increase. V_oc and α are inversely correlated with E_g . The hydrogen content affects the i-layer and p/i interface quality of the a-Si:H thin film solar cell with an optimal value of R = 0.95, which corresponds to solar cell conversion efficiency of 3.85%. The proposed a-Si:H thin film solar cell is expected to be improved in performance.