MgO加入量和煅烧温度对镁橄榄石材料相组成的影响

采用河南西峡的橄榄石原矿,分别配以0、6%、12%、15%、18%、24%(质量分数)的轻烧镁粉和31.85%的菱镁石粉(Mgo质量分数为47.1%),以亚硫酸纸浆废液为结合剂制成φ50 mm×50 mm的圆柱试样,在1 000、1 200、1 300和1 550℃保温3 h煅烧后,采用XRD和SEM分析试样的相组成和显微结构.结果表明:与菱镁石粉比较,轻烧镁粉与橄榄石的反应活性较高;加入6%的轻烧镁粉基本可使橄榄石矿中的顽火辉石和磁铁矿分别转化为镁橄榄石和镁铁尖晶石(煅烧温度1 300℃以上);加入轻烧镁粉或菱镁石粉的试样经1 300℃煅烧后的矿物相趋于稳定.     

烧结温度对合成镁橄榄石性能的影响

以电熔镁砂、二氧化硅微粉为原料,采用固相反应法合成镁橄榄石,研究了不同烧结温度及不同配比对合成镁橄榄石材料性能的影响.研究结果表明:以镁橄榄石的理论配比配料合成镁橄榄石,在温度较低时在镁砂表面形成一层镁橄榄石,随着温度的升高,镁橄榄石层变厚,方镁石颗粒被镁橄榄石层包围;烧结温度从1350℃升到1600℃,试样的显气孔率降低,组织结构变得致密,接近镁橄榄石理论配比的试样综合性能较优.     

轻质镁橄榄石砖的研制

以陕西商南的镁橄榄石为原料,以石油焦粉为造孔剂(其加入质量分数分别为30%、35%、40%),分别采用羧甲基纤维素、硅溶胶、MgCl2.6H2O为结合剂,以5 kN的压力成型后,分别于1 250、1 300、1 350℃保温3 h煅烧,测试烧后试样的线变化率、体积密度及耐压强度。结果表明:以MgCl2.6H2O为结合剂,加入40%质量分数的石油焦,经1 300℃保温3 h煅烧,可制备出体积密度为1.15 g.cm-3,耐压强度为3.58 MPa的轻质镁橄榄石砖。     

增孔剂对镁橄榄石质隔热耐火材料结构和性能的影响

采用天然镁橄榄石和镁砂为原料,以粘土为结合剂,在以泡沫法制备镁橄榄石质微孔高强耐火材料工艺的基础上,通过添加增孔剂碳黑和碳酸镁微粉,分析其对试样结构和性能的影响.实验结果表明:加入碳黑的试样,试样中可以形成大量的微气孔且分布均匀.     

泡沫法制备镁橄榄石隔热耐火材料

以镁橄榄石、硅微粉、轻烧氧化镁、六水氯化镁为主要原料,减水剂、聚乙烯醇、磷酸为外加剂,菱镁水泥作为结合剂,采用泡沫法制备了镁橄榄石隔热耐火材料,研究烧结温度对显微结构及物理性能的影响.结果表明:加入硅微粉后能提高料浆的流变性能,高温烧结后,试样孔结构发生了显著的改变,由椭圆形孔变为结构不规则且有层状空隙的h孔结构,且烧后孔壁棱角分明,孔壁中有微孔结构存在.随着温度的升高,试样的线收缩率和耐压强度逐渐增大,1100℃前增大速率较小,且数值较小,1100℃后显著增大.     

镁橄榄石质浇注料的研究

采用灼碱为９％的橄榄石生料为骨料,研制了镁质浇注料。结果表明,选用适当的结合剂并加入ＳｉＣ或ＺｒＳｉＯ,可以制得性能优良的镁橄榄石质浇注料。     

基于正交设计优化镁橄榄石轻质球形骨料的制备工艺

为了研究各因素对镁橄榄石轻质球形骨料性能的影响以优化其制备工艺,以菱镁矿细粉（<0.045 mm）、天然硅石粉（<0.048 mm）和二氧化硅微粉为起始物料,使用浓度15%（w）的硫酸镁溶液为结合剂,采用圆盘造粒机成型料球,经高温煅烧后制备了镁橄榄石轻质球形骨料。选取二氧化硅微粉加入量（5%、10%、15%,w）、罐磨机转速(300、400、500 r·min^-1)、研磨时间（1、1.5、2 h）和煅烧温度（1 400、1 420、1 450℃）为研究因素,每个因素各选取3个水平进行正交设计,分析了各因素对球形骨料性能的影响。结果表明：二氧化硅微粉加入量和煅烧温度为主要影响因素,而罐磨机转速和研磨时间为次要影响因素。综合考虑,最优工艺路线为二氧化硅微粉加入量、罐磨机转速、研磨时间和煅烧温度分别为10%（w）、300 r·min^-1、1 h和1 420℃。采用优化工艺生产的轻质球形骨料的性能优良,孔径分布均匀,微孔数量增加,有望作为优良的碱性隔热耐火原料。     

镁橄榄石质浇注料的研究

采用灼减为９％的橄榄石生料为骨料,研制了镁质浇注料。结果表明,选用适当的结合剂并加入ＳiＣ或ＺｒSｉＯ4可以制得性能优良的镁橄榄石质浇注料。     

料浆稠度对镁橄榄石制品性能的影响

以镁橄榄石和镁砂为主要原料 ,粘土为结合剂 ,利用泡沫法制备了微孔、高强度的镁橄榄石制品。研究了泡沫法制备工艺过程中 ,料浆稠度对孔径分布和制品强度的影响。结果表明 :稠度为6 0mm时 ,试样中 <2 0 μm的微孔数量最多 ,且耐压强度最高     

Synthesis of hollow forsterite by coating method and study of its dielectric properties

Wireless communication technologies are operating at higher frequencies in the current ubiquitous age, dielectrics with low dielectric constant and low dielectric loss are highly desired. A novel coating method was used for the synthesis of hollow forsterite ceramics. Here, magnesium glycolate with relatively high and high specific surface area (243.44 m²/g) and pore width (1.35 nm) is used as core material. Highly pure uniform-sized forsterite phases were obtained at a low calcination temperature of 900 °C/2 h. Scanning electron microscope, Transmission electron microscope, and X-ray diffraction were used to characterize the morphology and phase development at different calcination temperatures. The dielectric properties were measured in the range of microwave frequencies. As prepared, forsterite (Mg₂SiO₄) ceramics had shown excellent dielectric properties with ε_r = 1.85 and dielectric loss = 0.007 at 1 GHz. As wave propagation delay and attenuation depend on dielectric constant and dielectric loss. This ultra-low ε_r of 1.85 will enhance the signal speed in the microwave frequencies region which makes forsterite a promising candidate for electronics packaging applications.     

Sr-doped forsterite nanopowder: Synthesis and biological properties

Nanoscale forsterite (Mg₂SiO₄) has recently been proposed for bone tissue engineering application. Due to the special role of strontium (Sr) in bone remodeling, the stimulation of bone formation and reduction in bone resorption, the modification of forsterite by doping with Sr is expected to increase bioactivity and biocompatibility. The aim of this study was to incorporate Sr (0, 0.05, 0.1, 0.2 and 0.4 at%) into forsterite using sol-gel method and to investigate the effect of Sr content on the phase composition, in vitro apatite-formation ability as well as osteoblast-like MG63 viability. Results demonstrated that while forsterite was the main phase of all Sr-doped forsterite nanopowders, Sr₂MgSi₂O₇, MgO and MgSiO₃ were present as the minor phases depending on the Sr content. Moreover, the presence of Sr atom influenced the crystallite and particle size as well as lattice parameters of the forsterite powder, while did not significantly change the morphology of particles. Noticeably, the incorporation of Sr up to 0.2 at% enhanced the average crystallite size (from 25.3 nm to 45.9 nm) and particle size (31.0 ± 3.9 nm to 62.9 ± 11.8 nm) of pure forsterite powder. Additionally, according to the Rietveld refinement, the incorporation of Sr up to 0.2 at% increased the lattice parameters of forsterite more than 0.1%, depending on the Sr content. In vitro bioactivity assessment in simulated body fluid (SBF) revealed while all Sr-forsterite samples possessed greater bioactivity than pure forsterite nanopowder, the incorporation of 0.1 at% Sr revealed improved bioactivity compared to other Sr-forsterite samples. However, according to MTT assay, while all forsterite-based ceramics significantly improved the cell proliferation compared to tissue culture plate (TCP) and forsterite nanopowder, Sr-forsterite nanopowders consisting of 0.05–0.1 at% Sr revealed a considerably promoted cell proliferation. In conclusion, Sr-forsterite nanopowder could be a promising candidate for bone tissue engineering and reconstruction of bone defects such as osteoporosis.     

原位分解制备高强度轻质镁橄榄石材料

以菱镁矿、粉石英、二氧化硅微粉为原料,利用原位分解形成气孔技术制备轻质镁橄榄石材料,并借助XRD和SEM等方法研究了烧成温度(分别为1200℃、1300℃、1350℃、1400℃和1450℃)对轻质材料的物相组成和显微结构的影响。结果表明:制备轻质镁橄榄石材料的最佳烧成温度为1300～1400℃,在这一温度范围内烧成制得的轻质镁橄榄石材料有较高的气孔率,气孔平均孔径<10μm,且分布均匀,耐压强度可达40～50MPa,是一种高强度的轻质耐火材料。     

Influence of spherical porous aggregate content on microstructures and properties of gas-permeable mullite-corundum refractories

In this study, six gas-permeable mullite-corundum refractories with 45–95 wt% spherical porous mullite aggregates were prepared. The influence of the spherical porous aggregate content (SPAC) on the microstructure, gas permeability, and mechanical properties was analysed by XRD, SEM, EDS and image analysis method, etc. It's found that the SPAC affected the pore characteristics and mechanical properties through changing the packing and sintering behaviours of the aggregate and matrix in the refractories. When the SPAC was 45–65 wt%, the refractories had higher strengths as well as two gas-permeable channels in the aggregate and matrix respectively. Whereas, when the SPAC increased to 75–95 wt%, the refractories had lower strength as well as one gas-permeable channel in the matrix. The optimized product contained 65 wt% spherical porous aggregate and combined a high gas permeability of 4.9 × 10⁻¹² m², a high compressive strength of 18.5 MPa, a good thermal shock resistance and well-distributed gas-permeable channels.     

Nanoscale synthesis of single-phase forsterite by reverse strike co-precipitation and its high optical and mechanical properties

Forsterite is a magnesium silicon oxide mineral with an olivine structure and a diverse spectrum of applications, ranging from biomedical to optical devices. Controlled purity and crystalline phases are key requirements for such applications, but the literature shows a limited understanding of the synthetic routes that would enable such control, in particular at the nanoscale. In this work, single-phase forsterite nanopowder with a crystallite size of 15.3 nm was synthesized by reverse strike co-precipitation. A reaction mechanism for the synthesis was proposed based on DSC/TGA analysis and intermediate products. Forsterite pellets using the nanopowder were produced by low-cost cold-pressing and showed high transparency and densities above 93%. The nanosized crystals allowed for lower sintering temperatures and enhanced hardness.     

Effect of waste serpentine on the properties of basic insulating refractories

Basic insulating refractories were fabricated by the pressing route using dead-burned magnesia, pure calcined alumina, expanded perlite, and calcined waste serpentine as starting raw materials in four compositions from F1 to F4. Periclase and forsterite were major phases in F1 and F2 compositions, while spinel was also detected in the XRD patterns of F3 and F4 samples. Quantitative phase analysis showed that F4 sample sintered at 1450?°C has the highest forsterite content among all other samples. On the other hand, it has lower thermal conductivity compared to F1 to F3, and even lower than aluminosilicate IFBs with the same bulk density. It is concluded that forsterite is a highly insulating material, compared to periclase, corundum, periclase-spinel, aluminosilicates, such as mullite, etc.     

镁橄榄石对中间包镁质干式料性能的影响

在中间包镁质干式料中分别引入不同质量分数(分别为0、25%、30%、35%、40%和45%)的轻烧镁橄榄石或生镁橄榄石,成型后分别在220和1 500℃热处理,然后检测试样的体积密度、加热永久线变化、耐压强度、抗折强度和抗渣性能。结果表明:随着生镁橄榄石或轻烧镁橄榄石加入量的增加,试样的体积密度和强度均有一定程度的下降,烧后收缩率逐渐减小,最后表现为膨胀,但抗渣性差别不大;加入生镁橄榄石与加入轻烧镁橄榄石对试样性能影响的差别较小。     

Synthesis and characterization of high-density B2O3-added forsterite ceramics

Boria (B₂O₃)-added forsterite (Mg₂SiO₄) ceramics were synthesized and their properties were characterized. The addition of B₂O₃ was aimed to produce high density forsterite ceramics at a low sintering temperature. The raw materials were purified silica sand and commercial magnesia powders. Fosterite powder was produced from a solid reaction between the raw powders at 1100 °C prior to addition of B₂O₃, uniaxial pressing and sintering at 1200 °C. The amount of added B₂O₃ varied between 0%, 4%, and 8% by weight. Elemental analysis was performed by X-ray fluorescence (XRF) spectroscopy on the purified silica powder, whereas phase analyses were obtained from X-ray diffraction (XRD) data. Characterization of the ceramics included diameter shrinkage, density-porosity, thermal expansion, Vickers hardness, and dielectric constant. The results showed that the silica powder contained 98.7 at% Si with minor impurities, including 0.5 at% Ti, but the only identified crystalline phase was quartz. Further phase analysis of the ceramics showed that the addition of B₂O₃ reduced the amount of formed forsterite and increased the amount of cristobalite, proto- and clino-enstatite (MgSiO₃) as well as suanite (Mg₂B₂O₅). The highest forsterite content was found in B₂O₃-free ceramics, approximately 88.1 wt%. Moreover, the addition of B₂O₃ also reduced the diameter of the sample by more than 21%, resulting in a very dense ceramic with an apparent porosity of only 0.3%. The Vickers hardness significantly increased from 0.3 GPa for the B₂O₃-free ceramic to 10.9 GPa for the 4% B₂O₃ sample. The dielectric constant of the B₂O₃-added forsterite ceramics was improved by approximately 2–6 times that of the B₂O₃-free ceramic, which was primarily attributed to the loss of porosity in the samples.     

再生骨料对混凝土力学性能及耐久性影响的研究

针对再生骨料由于本身结构缺陷的原因,造成混凝土力学性能和耐久性不良的问题,采用再生骨料裹浆预处理和密实骨架堆积配合比设计方法,弥补再生骨料的结构缺陷,提高混凝土密实程度,使得再生骨料混凝土的抗压强度和抗碳化性能、抗氯离子渗透性能得到有效改善。