Properties of the surface layer and combustion behavior of metallized solid propellants

The properties of the surface layer of burning metallized solid propellants are analyzed on the basis of available experimental data. A general physical concept of processes in the surface layer is developed. The structure called a skeleton layer is shown to play a key role in combustion. The factors influencing the properties of the skeleton layer are determined, and the effect of these of properties on the properties of condensed combustion products and the propellant burning-rate law is studied. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 4, pp. 156–165, July–August, 2009.     

Refractory Plastic Masses Based on Highly Concentrated Ceramic Binding Suspensions (HCBS). II. Structural and Mechanical Properties of Plasticized HCBS in the System SiO2 – Clay

Rheological properties of individual suspensions of quartz sand, quartz glass, and Nizhne-Uvel'skoe (NU) clay and compound suspensions of these components containing 20 – 80% NU clay are studied. The effect of NU content on rheological properties of the compound suspensions is considered. Structural and mechanical properties of plastic masses (with a moisture content of 10 – 20%) based on compound suspensions using a Tolstoi plastometer are studied. The data obtained are used to determine the main elastoplastoviscous and structural-mechanical properties of the plastic masses. The effect of the added HCBS on the rheological characteristics is considered.     

Effect of γ-Radiation on the Dielectric Behaviour of Some Agricultural Wastes

Abstract

Dielectric properties of some agricultural wastes e.g., cotton stalks, Cs, rice straw, Rs and bagasse, B, are studied. The chemical constituents as well as the morphology of these material play a big roll on their dielectric properties. The effect of γ-irradiation on the dielectric properties of these lignocellulosic materials is also investigated. Grafting of these raw materials with acrylamide using γ-irradiation at dose of 20 M rad is also studied. Dielectric properties of these grafted materials and its complexes with Co⁺⁺ is clarified. The mechanism of the interaction of γ-radiation with the investigated samples is also studied.     

油田三采助剂对原油性质的影响

以油田常用的三采助剂为研究对象,通过模拟原油开采过程,研究了油田三采助剂对南阳原油性质的影响。研究结果如下:油田三采助剂在正常使用量范围内不会影响原油的性质,超过使用量则负作用明显;使用三采助剂不会影响原油中S、Cl、N含量,但磺酸盐类、高Cl助剂除外;应控制或限制高CL助剂使用;三采助剂与原油中的乳化层存在一定关联,应引起注意。     

Prediction of elastic properties for single-walled carbon nanotubes

Based on a link between molecular and solid mechanics, an analytical method was developed for modeling the elastic properties of single-walled carbon nanotubes (SWNTs). A SWNT is regarded as a continuum-shell model which is composed of the discrete molecular structures linked by the carbon-to-carbon bonds. The elastic properties were investigated for the SWNTs as a function of the nanotube size in terms of the chiral vector integers (n,m). The theoretical prediction on elastic properties agreed reasonably with the existing experiment and theoretical results. The present formulas are able to serve as a good approximation of the elastic properties for SWNTs.     

VCD Studies on Chiral Characters of Metal Complex Oligomers

The present article reviews the results on the application of vibrational circular dichroism (VCD) spectroscopy to the study of stereochemical properties of chiral metal complexes in solution. The chiral characters reflecting on the vibrational properties of metal complexes are revealed by measurements of a series of β-diketonato complexes with the help of theoretical calculation. Attention is paid to the effects of electronic properties of a central metal ion on vibrational energy levels or low-lying electronic states. The investigation is further extended to the oligomers of β-diketonato complex units. The induction of chiral structures is confirmed by the VCD spectra when chiral inert moieties are connected with labile metal ions. These results have demonstrated how VCD spectroscopy is efficient in revealing the static and dynamic properties of mononuclear and multinuclear chiral metal complexes, which are difficult to clarify by means of other spectroscopes.     

Difficulty inflammable organoplastic

The effect of a phosphorus-containing epoxy oligomer on the properties of an organoplastic fabricated by the pultrusion process was investigated. It was found that the material is difficultly inflammable, self-extinguishing, and is as good as the starting flammable organoplastic with respect to the level of the physicomechanical properties. The positive effect of additional heat treatment (155–250°C temperature range) of samples of the organoplastic on their physicomechanical properties was demonstrated.Tekhnologiya Obninsk Scientific-Industrial Enterprise. Translated from Khimicheskie Volokna, No 3, pp. 35–37, May–June, 1996.     

Effects on Dielectric Properties of Modified Bismaleimide Resins

Abstract

Six modified bismaleimide (BMI) resin systems are developed. The modifier is diallyl bisphenol A, diallyl bisphenol A ether. TDE-85 epoxy/MNA anhydride, and styrene. respectively. In view of structure of those cured resins, relationships between structure and dielectric properties have been studied emphatically, while effects of postcure temperature and catalysts on dielectric properties were also shown. Results indicate that dielectric properties lie on structure of cured resin and postcure temperature; catalysts can strikingly improve the heat-resistance of materials, but has little effect on the dielectric properties. In addition, mechanical and thermal properties of neat resins were also shown.     

硫化发泡体系对硅橡胶泡沫材料应力松弛性能的影响

考察了过氧化二异丙苯/N,N-二亚硝基五次甲基四胺(DCP/H)、2,5-二甲基-2,5-二叔丁基过氧化己烷/偶氮二甲酰胺(双二五/AC)和过氧化苯甲酰(BPO)/AK 3种硫化发泡体系及助交联剂TAIC对硅橡胶泡沫材料力学性能和压缩应力松弛性能以及泡孔结构的影响。结果表明,DCP/H硫化发泡体系的力学性能和应力松弛性能优于双二五/AC和BPO/AK,添加适量助交联剂TAIC有助于进一步降低硅橡胶泡沫材料的应力松弛性能。扫描电镜(SEM)观察发现,DCP/H硫化发泡体系对应的硅橡胶发泡材料泡孔较小且分布均匀,当加入适量的助交联剂TAIC后,硅橡胶泡沫材料的泡孔更加细小均匀。     

Study of the Effect of Nano-silica Particles on Resin-Bonded Moulding Sand Properties and Quality of Casting

The cast quality in chemical bonded sand mould system is influenced primarily by sand mould properties such as, compression strength, permeability, gas evolution, and collapsibility. Amount of resin and hardener, curing time and number of strokes influence the sand mould properties. The experiments are conducted with the above mentioned input output, as per Taguchi’s L₉ orthogonal array. Pareto analysis of variance is conducted to determine the percent contribution of inputs on output, individually. The optimal factor level is determined for each output separately. The conflicting requirements in foundry sand mould properties can be solved by multiple objective optimization. Principal component analysis is applied to determine the relative importance of individual output. Grey relational analysis is used to convert multiple objective functions to a single objective function for optimization task. Pareto analysis is utilized to determine the optimal input factor combination and their relative percent contribution towards moulding sand properties. The nano-silica particles are used as additive to enhance the moulding sand properties. The results have shown that, the nano-silica particles pose a remarkable improvement in sand mould properties and casting quality.     

Strengthening of Al2O3 porous composites with a glass-ceramic binder doped with nanocopper

Glass ceramics are the result of controlled crystallisation of one or more crystalline phases embedded in the glass matrix, which usually results in better mechanical properties than conventional glasses. Crystalline phases precipitated in the vitrified bond improve mechanical strength and provide new functions that are not present in the original glass. The most widely encountered issue in standard composites is the presence of inclusions, generated during the process of thermal treatment, of finely dispersed crystalline phases, which are spread in the amorphous phase.Another way of increasing the mechanical properties of composites is via surface crystallisation of the binder. The mechanical strength can be significantly and permanently increased by inducing compressive stress at the glass surface. In the case of the binder designed here, the generated crystalline phase is willemite (Zn₂SiO₄), which is characterised by a low coefficient of thermal expansion (CTE). Zn₂SiO₄ usually crystallises at the glass surface, which results in the development of favourable compressive stresses in the glass-crystalline binder.Transition metal oxides significantly affect the crystallisation characteristics, thus influencing the thermal behaviour of glass ceramics. The majority of current publications focus on studies of the influence of copper on certain properties, and mainly the optical and photonic properties, and the influence of copper on the mechanical properties of silicate systems is still poorly recognised. This article investigates the mechanical and physical properties of porous Al₂O₃ composites with a glass-ceramic bond doped with nanocopper.     

Physical properties of high-pressure ethylene vinylacetate copolymers and their saponified derivatives

The physical properties of high-pressure ethylene vinylacetate (EVA) copolymers having an average melt index of 8.5 g/10 min and a mol% of VA less than 20 are studied. A comparison is made with the properties of their saponified derivatives, the ethylene vinylalcohol (EVAl) co- and ethylene vinylalcohol vinylacetate (EVAlVA) terpolymers. A melt-index effect is noted. Density, thermal, and mechanical properties of EVA copolymers are determined by the degree of crystallinity, which depends on the mol% VA and on the degree of alkyl shortchain branches. EVAlVA terpolymer properties depend on the residual mol% VA. EVAl copolymers proved to have some properties similar to low-density polyethylene. The hydrogen-bonding effect via hydroxyl groups was negligible for this level of vinylalcohol incorporation.     

Effect of technological parameters on the properties of Cuo-TiO2 sol-gel films

The effect of technological parameters on the properties of 2-and 42-day film-forming solutions of the system CuO-TiO₂ is analyzed. It is found that the initial components have a strong effect on the maturing of film-forming colloidal solutions (FCS) and the properties of coatings. The properties of coatings obtained from solutions of different age are associated with changes in their microstructure. The index of refraction and the thickness of the films from 42-day FCS are essentially independent of the calcination regime; the variation of the refractive coefficient and chemical stability is inconsistent.     

硫化剂及填料对氯醚橡胶力学性能和老化性能的影响研究

研究了3种硫化剂——2,3-二巯基-喹喔啉(DNR-12A)、三巯基均三嗪(TCY)和亚乙基硫脲(NA-22)及3种填料——高耐磨炭黑(N330)、木质素-蒙脱土复合物填料(BL-MMT)和碱性木质素(lignin)对共聚型氯醚橡胶(ECO)硫化特性、交联密度、力学性能和老化性能的影响。结果表明,固定填料为N330时,用NA-22硫化的胶料的力学性能最好,但热氧老化性能最差;改变填料后NA-22硫化胶料的老化性能得到提高,固定硫化剂为NA-22时,以碱性lignin为填料的胶料的力学性能与热氧老化性能均最好,拉伸强度达15.5 MPa,断裂伸长率达394%,100%定伸应力达6.4 MPa,老化后拉伸强度保持率为103.2%。     

The effect of boron nitride nanosheets on the mechanical and thermal properties of aluminum nitride ceramics

The boron nitride nanosheets (BNNSs)/aluminum nitride (AlN) composites were prepared by hot press sintering at 1600°C. The microstructure, mechanical properties, and thermal conductivity of the samples were measured, and the effect of adding BNNSs to AlN ceramics on the properties was studied. It is found that the addition of BNNSs can effectively improve the mechanical properties of AlN. When the additional amount is 1 wt%, the bending strength of the sample reaches the maximum value of 456.6 MPa, which is 23.1% higher than that of the AlN sample without BNNSs. The fracture toughness of the sample is 4.47 MPa m^1/2, a 68.7% improvement over the sample without BNNSs. The composites obtained in the experiment have brilliant mechanical properties.     

Sol-Gel Luminophors Based on Diopside

A relationship is established between the conditions of sol-gel synthesis of powders, their crystallization capacity, and the luminescence properties of crystal phosphors of the composition CaMgSi₂O₆ : Ti⁴⁺. The properties of materials produced using one-stage and two-stage procedures for heat treatment of the gels are compared. It is shown that the calcination stage has a positive effect on the crystallization process and on the luminescence properties of the articles, and the calcination-stage temperature is a deciding factor in optimization of the heat-treatment procedure.     

Study on the Friction and Wear Behaviors of Modified PA66 Composites

The wear-resistant polyamide 66 (PA66) composites were prepared and the mechanical properties, friction and wear properties were inspected. Results show that GF, PTFE and MoS₂ can improve the mechanical, friction and wear properties of PA66 composites. PTFE is more effective on the friction and wear properties than MoS₂ when GF is 30%wt. The best effect of the modification is 35%wt GF when both PTFE and MoS₂ were added. Friction coefficient first increase, then reduce to be stable as sliding time increases. Friction coefficient and wear mass loss increase as load increases. The main wear mechanisms are fatigue and abrasion wears.     

Effect of two types of layered silicate on mechanical and barrier properties of hydrogenated acrylonitrile butadiene rubber (HNBR)/layered silicate nanocomposites

Abstract

The role of the type of layered silicate platelets, OMMT and rectorite on the mechanical properties, aging resistance and oxygen permeation properties of HNBR/layered silicate nanocomposites was investigated. The effect of peroxide vulcanising agent on the dispersion of layered silicate in the HNBR matrix was also studied. HNBR was mechanically mixed with layered silicate via melt blending method. The results of the test show remarkable improvement in tensile strength, tear strength, aging resistance and oxygen permeation properties of HNBR nanocomposites than that of unfilled HNBR. It is obvious that the OMMT filled nanocomposites have far better properties than that of rectorite filled HNBR.     

Mechanical properties of HAp–ZrO2 composites

Hydroxyapatite is a well-known and valuable implant material with bioactive properties. Full utilisation of the unique properties of hydroxyapatite ceramics is, however, possible only after its proper reinforcement, i.e., by preparation of composites. In the present work zirconia reinforced hydroxyapatite composites were obtained by hot pressing method. The reinforcing phase in the form of ZrO₂ particles was selected due to the satisfactory biocompatibility of ZrO₂ and also because of its exceptional mechanical properties.Our investigations were aimed at assessing the influence of varying ZrO₂ on the phase composition and mechanical properties of HAp–ZrO₂ composites. In order to produce dense sinters, we used three types of initial zirconia powders which differed in morphology and contents of the tetragonal and monoclinic phases. We studied the influence of these oxides on thermal stability of hydroxyapatite matrix as well as on the phase composition and mechanical properties of the composite materials produced.     

Synthesis of manganese ferrite from non-standard raw materials using ceramic technique

Manganese ferrite spinel has been synthesized by using mill scale and fines of manganese ore sinter as sources of iron oxide and manganese oxide, respectively. The magnetic and physico-mechanical properties of the produced sample are largely dependent not only on the sintering condition but also on the Mn:Fe mole ratio. The effect of silica (which is one of the constituents of the fines of manganese ore sinter) on the properties of the sintered samples is investigated. The results show that a single phase of manganese ferrite spinel with weak magnetic properties is obtained in a sample containing a Mn:Fe mole ratio of 1.4:2 and sintered at 1300 °C for 2 h. On the other hand, a maximum saturation magnetization (62 emu/g) with reasonable physico-mechanical properties is obtained for a sample containing a Mn:Fe mole ratio of 1.3:2 and sintered at the same sintering conditions.