Growth and Characterization of InAs1-xSbx with Different Sb Compositions on GaAs Substrates

InAs1-xSbx with different compositions is grown by molecular beam epitaxy on （100）-oriented semi-insulating GaAs substrates. The increase of Sb content in the epilayer results in the deterioration of crystal quality and surface morphology. Hall measurements show that the carrier concentration increases with the composition of Sb. The electron mobility decreases initially, when Sb composition exceeds a certain value, and the mobility increases slightly. In this work, we emphasize the comparison of crystal quality, surface morphology and electrical properties of epilayers with different Sb compositions.

Germination and Early Seedling Growth of Moringa oleifera Lam with Different Seeds Soaking Time and Substrates at the Yongka Western Highlands Research Garden Park (YWHRGP) Nkwen-Bamenda, North-West Cameroon

Moringa oleifera is a multipurpose tree used to remedy problems related to food insecurity and soil fertility degradation. Proper husbandry of this crop is contingent on the use of seedlings of good quality. This study aimed at assessing the germination and early seedling growth with different soaking durations and substrates composition. The seeds were obtained from the Far North region of Cameroon. A randomized complete block design with three replications was used. Two factors were tested;soaking duration with 4 treatment levels of 0 day, 4 days, 8 days and 12 days and substrates with 8 treatment levels: 100% soil, 75% soil + 25% poultry manure (PM), 50% soil + 50% PM, 25% soil + 75% PM, 100% sand, 75% sand + 25% PM, 50% sand + 50% PM and 25% sand + 75% PM. Germinated seeds and growth parameters were collected after every 5 days. The results showed that soaking duration and substrate composition influence germination and initial development of M. oleifera (p ≤ 0.05). At 25 days after soaking (DAS), soaking durations of 0 day (68.7%) and 8 days (53.1%) showed the highest germination percentages while seeds soaked for 12 days occupied the least position with 37.5%. At the same time, 75% soil + 25% PM (68.7%), 100% sand (64.5%) and 100% soil (60.5%) with the unsoaked seeds showed the highest germination percentages. The least germination percentages were represented by 50% sand + 50% PM and 25% sand + 75% PM with 35.5% and 27%, respectively. Unsoaked seeds with the substrates of 50% soil + 50% PM are the best practice for M. oleifera seedling production in the nursery.

Variation in Enzymes Activities of Rhizospheric Substrate and Influencing Factors during Nursing of Watermelon Seedlings

[Objective] This study aimed to investigate the effects of substrate en- zymes activities on nursing of watermelon seedlings. [Method] The composted mushroom residue was mixed with garden soil according to a certain proportion to prepare nursing substrate for watermelon seedlings. During the nursing, the activity variation in alkaline phosphatase, acid phosphatase, neutral phosphatase and urease was investigated. In addition, the correlations between pH value, total nitrogen con- tent, total phosphorus content and organic matter content in substrate and enzyme activity were studied. At different young seedling stages, the rhizospheric substrates with different formulas were sampled for determination of enzymes activities. [Result] The enzyme activity differed significantly among different substrates. The correlation analysis results showed that the higher the organic matter content and total nitrogen content in substrate are, the higher the urease activity is; the phosphatase activity was significantly related to the organic matter content, total nitrogen content and to- tal phosphorus content in substrate; the pH value of substrate was significantly relat- ed to rhizospheric alkaline phosphatase activity; the shoot dry weight was positively related to urease activity; there was a significant correlation between phosphatase activity and root dry weight. [Conclusion] Through determining enzymes activities in the rhizospheric substrate for nursing watermelon seedlings, the optimum substrate M3 was screened out. The activities of rhizospheric urease, alkaline phosphatase, acid phosphatase and neutral phosphatase in the substrate M3 were all higher than those in the substrate fertilized with manure.

Effects of Different Substrate Composition on Growth of Gesneriaceae Plants

The cultivation experiment was carried out to investigate the effects of dif-ferent proportions of peat soil, perlite, vermiculite and yel ow mud on growth of Gesneriaceae species （Chirita gueilinensis, Sinningia speciosa, Lysionotus pauci-florus, Hemiboea henryi, Aeschynanthus acuminatus, Saintpaulia ionantha）. The growth traits of each plant growing in 7 different matrix materials were investigated. The plant height, crown width and chlorophyl content of each plant were mea-sured. The results showed that the best substrate ratio was peat soil∶vermiculite=2∶1 for C. gueilinensis, L. pauciflorus and H. henryi; peat soil∶perlite∶vermiculite = 2∶1∶1 for S. ionantha; peat soil∶vermiculite∶yel ow mud=2∶1∶1 for S. speciosa; peat soil∶per-lite∶vermiculite∶yel ow mud=2∶1∶1∶1 for A. acuminatus.

Photocatalytic properties of P25-doped TiO_2 composite film synthesized via sol–gel method on cement substrate

TiO2 films have received increasing attention for the removal of organic pollutants via photocatalysis. To develop a simple and effective method for improving the photodegradation efficiency of pollutants in surface water, we herein examined the preparation of a P25-TiO2 composite film on a cement substrate via a sol–gel method. In this case, Rhodamine B（Rh B）was employed as the target organic pollutant. The self-generated TiO2 film and the P25-TiO2 composite film were characterized by X-ray diffraction（XRD）, N2 adsorption/desorption measurements, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and diffuse reflectance spectroscopy（DRS）. The photodegradation efficiencies of the two films were studied by Rh B removal in water under UV（ultraviolet） irradiation. Over 4 day exposure, the P25-TiO2 composite film exhibited higher photocatalytic performance than the self-generated TiO2 film. The photodegradation rate indicated that the efficiency of the P25-TiO2 composite film was enhanced by the addition of the rutile phase Degussa P25 powder. As such, cooperation between the anatase TiO2 and rutile P25 nanoparticles was beneficial for separation of the photo-induced electrons and holes. In addition, the influence of P25 doping on the P25-TiO2 composite films was evaluated. We found that up to a certain saturation point, increased doping enhanced the photodegradation ability of the composite film. Thus, we herein demonstrated that the doping of P25 powders is a simple but effective strategy to prepare a P25-TiO2 composite film on a cement substrate, and the resulting film exhibits excellent removal efficiency in the degradation of organic pollutants.

Cyclic Oxidation Behavior of an EB-PVD CoCrAlY Coating Influenced by Substrate/coating Interdiffusion

To reveal the influence of substrate/coating interdiffusion on the cyclic oxidation property of a metallic coating, cyclic oxida- tion behavior of an EB-PVD CoCrAIY coating on directionally solidified Ni-based superalloy DZ125 at 1 050℃ is investigated. The 40 μm thick CoCrA1Y coating has a cyclic oxidation life of around 160 h, and the oxidation constant is 1.915× 10^-7 mg4.cm^-8.s-1. However, severe spallation of the oxides containing Co, Cr, Ni, Ta and Ti occurs with longer cyclic oxidation. The degradation in oxidation resistance for the coating is related to the depletion of A1 due to the oxide spallation and interdiffu- sion. Severe interdiffusion between the coating and underlying substrate occurs at 1 050 ℃. The composition of the substrate has an important effect on the thermal cycling lifetime of the coating. The influencing mechanism is discussed.