SIC/SIC composite thruster for a non-toxic liquid propellant rocket engine

Combustion chamber and nozzle for a non-toxic liquid rocket engine made by Tyrano ZMI SiC fiber reinforced SiC matrix composite were tested under sea level combustion tests. Combustion chamber and nozzle are the key hot parts for small liquid propellant engine, since chamber wall needs to be cooled by fuel rich low temperature gas. To create fuel rich low temperature gas, excess amount of fuel is consumed. Consequently, high temperature heat resisting material is indispensable to have better performance rocket engine. Nb based alloy are commonly used in combustion chamber and nozzle for a liquid propellant rocket engine for a satellite maneuver system with the maximum operating temperature around 1300°C. In this study, SiC/SiC combustion chamber with nozzle were examined and its performance was demonstrated by sea level static combustion tests in air and under vacuum. Tyrano ZMI SiC fiber (Ube Industry) was used as reinforcing fiber and carbon interface was selected to have higher temperature resistance. Fiber preform was fabricated by tri-axial braiding technique and carbon interface and SiC matrix were formed by chemical vapor infiltration (CVI). After CVI process, further densification was conducted by polymer infiltration and pyrolysis (PIP) process until no gas leak was detected under low pressure of 0.2 MPa. Largest inner diameter of the chamber was designed as 65 mm and the smallest inner diameter of 26 mm as a nozzle throat. Nozzle was designed with opening area ratio of 25 to investigate manufacturability. The combustion chamber and nozzle attached with a core engine as shown in Figure 1. Non-toxic fuel, ethanol, and oxidizer, N2O, were supplied through the showerhead type injection into combustion chamber. Sea level static combustion tests were conducted both in air and under vacuum (1.3 kPa). The engine combustion tests were successful (30s in air and 19 s in vacuum) and no damage could be found. The performance of the engine improved to specific impulse of 290s with assumption of nozzle area ratio 100. The maximum surface temperature reached to 1250°C, where the inner wall temperature could be calculated about 1600°C. Prototype engine development program successfully completed and we are preparing to start real application project of this engine system as a final stage of solid propellant satellite launcher Please click Additional Files below to see the full abstract

Layered double hydroxide composite monoliths with three-dimensional hierarchical channels: structural control and adsorption behavior

Hierarchically porous layered double hydroxide (LDH) materials have potential in anion-exchange, adsorption and catalysis applications, because of their large surface areas and liquid transportation capabilities. The preparation of monolithic LDH-Al(OH)3 composites with hierarchical µm/nm-scale channels and their adsorption behavior is reported. Monolithic gels were synthesized via sol-gel processing, from metal salt precursor solutions. m-scale macrochannels spontaneously formed by inducing phase separation during sol-gel transition. nm-scale mesochannels were accommodated as interstices between primary/secondary particles. In this study, these hierarchical channel sizes were controlled. The macrochannel size was controlled by tuning the degree of phase separation. The mesochannel size was controlled independently, by tuning the crystallite size of LDH under different solvothermal conditions. The relationship between pore characteristics and adsorption behavior of tailored hierarchically porous LDH-Al(OH)3 monolithic gels were investigated by using dye molecules as adsorbates. Monolithic gels with larger macrochannels and mesochannels exhibit faster adsorption rate and higher affinity, respectively. LDH-Al(OH)3 monolithic gels with hierarchical channels may have potential in some applications such as biosensing, water purification and catalysis.The study was supported by a Grant-in-Aid for Scientific Research (B) (No. 22360276) and a Grant-in-Aid for Young Scientists (B) (No. 24750206), from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan Society for the Promotion of Science (JSPS)

Layered Double Hydroxide (LDH)-based Monolith with Interconnected Hierarchical Channels: Enhanced Sorption Affinity for Anionic Species

Monolithic layered double hydroxides (LDHs) with interconnected channels have been expected to enhance sorption rate as well as increase accumulation of anions. Although powder molding can form easy-handled LDH compacts, interconnected channel formation therein has not been achieved. Herein, we demonstrate cm-scale monolithic LDH-based composites with interconnected hierarchical channels via a spontaneous sol−gel reaction. The synthesis was performed on Mg−Al hydrotalcite-type LDHs starting from metal chlorides aqueous/ethanolic solution with poly(ethylene oxide) incorporated. Addition of propylene oxide triggers sol−gel reaction to form monolithic xerogels with a formula of [Mg0.66Al0.33(OH)2Cl0.33·2.92H2O]·3.1Al(OH)3. LDH crystals together with aluminum hydroxide crystals homogeneously build up gel skeletons with well-defined hierarchical channels. The interconnected channels in μm range (macrochannel) are formed as a phase-separated structure, whereas the channels in nm range (nanochannel) are as interstices of primary particles. The channel architectures are preserved in the course of rehydration process, affording enhanced sorption affinity for anion species in the process. Both of macro and mesochannels as well as high charge density of the obtained LDHs (Mg/Al=2.0) contribute enhanced anion sorption in the monolithic xerogels. The materials obtained here opens up applications of high performance adsorbent and ion-storage free from diffusion limitation.The present work is partially supported by Grant-in-Aid for Scientific Research (B) (No. 22360276), and Grant-in-Aid for Young Scientists (B) (No. 24750206) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), administrated by Japan Society for the Promotion of Science (JSPS). Y. T. is also partially supported financially by a research grant from The Murata Scientific Foundation

Contribuition to development of self-compacting concrete

Orientador: Vladimir Antonio PaulonDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia CivilResumo: A presente dissertação tem como objetivo o desenvolvimento da especialidade da tecnologia do concreto de elevado desempenho, o concreto auto-adensável. A tendência do mercado em construir cada vez mais estruturas arrojadas exige o desenvolvimento de tecnologias que coadunem com a realidade técnico-econômica da obra. A concretagem destas estruturas, quando realizada em formas irregulares e em armação densa, ocasiona, na maioria das vezes, problemas no adensamento, formando descontinuidade e/ou segregação na peça concretada. Contudo, quando executada em concreto auto-adensável, estas ocorrências tendem a diminuir. Este trabalho apresenta a confrontação da metodologia de avaliação do concreto autoadensável no estado fresco com o método da caixa L e o utilizado atualmente na Alemanha conforme a norma DIN 1045 -2 DAfStb- Richtlinie Selbstverdichtender Beton (SVB-Richtlinie), com o propósito de levar para a prática procedimentos simples e de fácil análise do controle de trabalhabilidade do concreto, e também a aplicação do concreto auto-adensável em estruturas de escala real para analisar a segregação do concreto quando lançados a 4,00 metros de altura.Abstract: This study concerns a special kind of high performance concrete technology development, called self-compacting concrete. The growing market tendency to build bold structures requires construction technology development, which fits real technical-economical needs. The concrete placing in irregular shape structures, and reinforced concrete structures, most of time brings compacting problems and result on segregation, and/or not satisfactory concrete surfacing. However, the use of self-compacting concrete can reduce these problems. The main objective of this research is to compare L box method and the German standard DIN 1045 -2 DAfStb- Richtlinie Selbstverdichtender Beton (SVB-Richtlinie) for fresh self compacting concrete workability analysis, in order to propose the L box method as an practical and easy way test to control the fresh concrete quality. This study also provides an accurate description of self-compaction concrete history, its development and the advantages reached by the structures based on concrete selfcompacting concrete, as well. Furthermore this research sets a real beam and column structure concrete applications from 4,00 m high filling to analyze segregation behavior.MestradoEdificaçõesMestre em Engenharia Civi

Fabrication of hierarchically porous monolithic layered double hydroxide composites with tunable microcages for effective oxyanion adsorption

Removal of toxic substances from industrial wastes is an urgent issue for realizing a sustainable society. Layered double hydroxides (LDHs) are expected to be an effective adsorbent for toxic anions, especially oxyanions, because of their high anion adsorption capacity and reusability. Monolithic LDH materials with rational meso- and macropores are expected to show high adsorption capacity/rate towards targeted toxic substances owing to their large specific surface area and liquid transport property. Besides fabricating hierarchical pores, size control of microcages in LDH crystals is required to achieve selective removal of oxyanions. Herein, we prepared hierarchically porous monolithic LDH composites with tunable microcages by changing the combination of cationic species in the LDH crystal. Monolithic Mg-, Mn-, Fe-, Co- and Ni-Al type LDH composites with hierarchical pores were successfully prepared via an epoxide-mediated sol-gel reaction accompanying with phase separation. The monolithic Co-Al type LDH composite with hierarchical pores exhibited the highest CrO42− adsorption capacity because its microcage size well fits the CrO42− size. Also Co-Al type LDH composite adsorbed different oxyanions, depending on their affinity with the LDH, in SO42−, CrO42−, MoO42− and HVO42− co-existing solution. The pore size controllability in discrete length-scales of micrometers, nanometers, and picometers offers LDHs with tailored surface chemistries and physical properties desirable for effective and selective oxyanion adsorption.The study was supported by JSPS KAKENHI (No. 26288108, 26630322).This work is partially supported by the Kazuchika Okura Memorial Foundation and the Hosokawa Powder Technology Foundation