Chemical Analysis of Magnesia and Magnesia-Alumina Refractory Materials——Flame atomic absorption spectrometric method for determination of calcium oxide content

1 Scope This standard specifics the determination of calcium oxide coutent by flame atomic absorption spectrometric method.

Chemical Analysis Method for Carbon Bearing Refractory Products——Determination of Magnesium Oxide Content by CyDTA Volumetric Method

This standard specifies the method summary, reagents, apparatus, sampling, procedure, test results calculation and permissible tolerance of the determination of magnesium oxide by CyDTA volumetric method.

Removal of magnesium and calcium from electric furnace titanium slag by H_3PO_4 oxidation roasting-leaching process

H3PO4 oxidation roasting followed by HCl acid leaching was proposed to remove magnesium and calcium from electric furnace titanium slag containing 3.12% MgO and 0.86% CaO. XRF, XRD and SEM techniques were used to characterize the composition, mineral phase component and microstructure of the titanium slag. The H3PO4 oxidation thermodynamic, mineral phase transformation, microstructure, element distribution in titanium slag during H3PO4 oxidation process and leaching process were investigated. The thermodynamic analysis indicated that H3PO4 could promote the decomposition of MgTi2O5 and CaSiO3. The results indicated that H3PO4 could effectively promote the transformation of titanium-bearing mineral to rutile and enrich the impurities in MxTi（3-x）O5 into phosphate which could be removed by acid leaching process. Under the studied conditions, the leaching rates of magnesium and calcium reached 94.68% and 87.19%, respectively. The acid leached slag containing 0.19% MgO and 0.13% CaO（mass fraction） was obtained.

A tightly bonded reduced graphene oxide coating on magnesium alloy with photothermal effect for tumor therapy

Photothermal therapy becomes a hotspot in the treatment of bone tumors. Magnesium and its alloys are regarded as potential bone implants for their favorable mechanical property and biodegradable in vivo. However, there is few research devoted to fabricating a photothermal coating on Mg alloy. In the present study, reduced graphene oxide coating with a strong photothermal effect was prepared on the surface of AZ31via two steps. Firstly, graphene oxide coating was deposited on the surface via electrophoresis deposited(GO#), followed by a reduction process of the graphene oxide coating in ultrapure water(rGO#). GO# and rGO# coatings were characterized by SEM, Raman, XRD, FTIR,and XPS. The results revealed that, compared with GO# coating, the content of oxygen-containing(C-O/C-O-C, C=O, O-C=O) groups on rGO# coating was significantly decreased. rGO# coating was found tightly adhered to AZ31 substrate. According to the first-principles calculations, the well-bonded heterostructure between MgO and rGO is the main reason for the strong bonding force. Moreover, the prepared rGO# coating showed a superior photothermal effect, which brings a new strategy to the treatment of bone tumors with Mg-based implants.

Effect of nitric oxide synthase inhibitor N^G-nitro-L-arginine on the content of amino acid in ischemic brain tissues of rats

BACKGROUND： Nitric oxide synthase （NOS） inhibrtors have been widely used to investigate the role of NO on cerebral ischemic injury, but the results are controversial. Moreover, it has been considered to aggravate the ischemic neuronal damage with the release of excessively excitatory amino acids （EAA） during cerebral ischemia. On the other hand, some inhibitory amino acid is suggested to be important for the neuronal protection against ischemic brain damage. Our study has recently showed that treatment with the NOS inhibitor NG-nitro-L-arginine （L-NA） reduced focal cerebral ischemic damage. The effect of L-NA on the contents of excitatory and inhibitory amino acid in the rat brain following cerebral ischemia is still unclear. OBJECTIVE： By evaluating the effect of NOS inhibitor, L-NA on the contents of aspartate, glutamate, glycine and γ-aminobutyric acid （GABA） in striatum, hippocampus and cortex in the rat brain following cerebral ischemia respectively, to investigate the beneficial effect of L-NA on cerebral ischemic injury and the possible mechanism. DESIGN： A randomized and controlled experiment SETTING ： Department of Pharmacology, Hebei Academy of Medical Sciences MATERIALS： A total of 42 male healthy SD rats （grade Ⅱ, weighting 250-300 g） were provided by the Experimental Animal Center of Hebei Province （Certification： 04036）. Aspartate, glutamate, glycine, GABA, L-NA and 2,3,5-triphenyltetrazolium chloride （TTC） were obtained from Sigma Chemicals Co, St Louis, MO, USA. HPLC-ultraviolet detector system consisted of Agilent 1100 HPLC. METHODS： The experiment was carried out in Department of Pharmrcology, Hebei Academy of Medical Sciences from June 2005 to June 2006. Rats were randomly divided into three groups： sham-operated group （n = 6）, ischemic group （n = 18）, L-NA group （n = 18）. The model of focal cerebral ischemia in rat was prepared with intraluminal line occlusion methods. In sham-operated rats, the external carotid artery was surgically prepared, but the filament was not inserted. Each group was further divided into 3 subgroups （n = 6 for each）： drugs were administrated at 2, 6 and 12 hours after the middle cerebral artery occlusion （MCAO） respectively. L-NA （20 mg/kg, ip） was administrated, twice a day, for 3 consecutive days. Same volume of normal saline was administrated in ischemic and sham operation groups. The changes of infarcted volume and the contents of amino acids were respectively assayed. Image analysis software was used for the measurement of the infarcted area. The results were expressed as a percentage of the infarcted volume of cerebral/volume of whole brain （IV%） in order to control for edema formation. The contents of aspartate, glutamate, glycine and GABA in striatum, hippocampus and cortex in the rat brain following cerebral ischemia were respectively measured by HPLC method. All data were analyzed with one-way ANOVA and Dunnett＇s test. MAIN OUTCOME MEASURES： （1） The volume of cerebral infarction; （2） The contents of aspartate, glutamate glycine and GABA in brain tissue after cerebral ischemia. RESULTS ： All 42 rats were involved in the final analysis. （1） Infarcted volume： Volume was 0 in sham-operated group. When L-NA was administrated at 2 and 6 hours after MCAO, the infarcted volume was （20.13±3.59）% and （23.12±5.84）% in L-NA group, which was not similar to that in ischemic group [（22.10±3.98）%, （25.38± 5.37）%, P〉 0.05]. However, the infarcted volume was markedly decreased compared with that of ischemic group when L-NA was administrated at 12 hours after MCAO [（26.11±3.55）% and （37.15±3.58）%, P 〈 0.01]. Changes of amino acid content： At 2 and 6 hours after ischemia, the contents of aspartate, glutamate, glycine and GABA in striatum, hippocampus and cortex in ischemic group were significantly increased compared with those in sham-operated group （ P〈 0.05-0.01）. However, contents in L-NA group were similar to those in ischemic group （P 〉 0.05）. At 12 hours after ischemia, the contents of aspartate [（0.21 ±0.06）, （0.36±0.05）, （0.29±0.12） mg/g] and glutamate [（0.55±0.06）, （0.78±0.10）, （0.52±0.10） mg/g] in striatum, hippocampus and cortex in L-NA group were significantly decreased compared with those in ischemic group [（0.49±0.17）, （0.63± 0.03）, （0.51±0.15） mg/g; （0.98±0.30）, （1.15±0.15）, （0.93±0.15） mg/g, P〈 0.05-0.01]. Glycine in hippocampus was （0.40±0.07） mg/g, which was higher than that in ischemic group [（0.21±0.07） mg/g, P 〈 0.05]. GABA in striatum, hippocampus and cortex was （0.93±0.10）, （0.62±0.12） and （0.81 ±0.10） mg/g, respectively, which was higher than that in ischemic group [（0.60±0.08）, （0.37±0.17）, （0.59±0.10） mg/g, P 〈 0.05-0.01]. CONCLUSION ： It may be concluded that L-NA have beneficial effect on ischemic cerebral injury in ischemic later stage in rats. The possible mechanism is that L-NA can decrease the contents of aspartate and glutamate, increase the contents of glycine and GABA.

Mssbauer study of function of magnesium in iron oxide catalysts

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Magnesium-L-threonate exhibited a neuroprotective effect against oxidative stress damage in HT22 cells and Alzheimer’s disease mouse model

BACKGROUND Oxidative stress results in the production of excess reactive oxygen species(ROS)and triggers hippocampal neuronal damage as well as occupies a key role in the pathological mechanisms of neurodegenerative disorders such as Alzheimer’s disease(AD).A recent study confirmed that magnesium had an inhibitory effect against oxidative stress-related malondialdehyde in vitro.However,whether Magnesium-L-threonate(MgT)is capable of suppressing oxidative stress damage in amyloidβ(Aβ)_(25-35)-treated HT22 cells and the AD mouse model still remains to be investigated.AIM To explore the neuroprotective effect of MgT against oxidative stress injury in vitro and in vivo,and investigate the mechanism.METHODS Aβ_(25-35)-induced HT22 cells were preconditioned with MgT for 12 h.APPswe/PS1dE9(APP/PS1)mice were orally administered with MgT daily for 3 mo.After MgT treatment,the viability of Aβ_(25-35)-treated HT22 cells was determined via conducting cell counting kit-8 test and the cognition of APP/PS1 mice was measured through the Morris Water Maze.Flow cytometry experiments were applied to assess the ROS levels of HT22 cells and measure the apoptosis rate of HT22 cells or hippocampal neurons.Expression of B-cell lymphoma 2(Bcl-2),Bcl-2-associated X(Bax),hypoxiainducible factor(HIF)-1α,NADPH oxidase(NOX)4,Aβ_(1-42) and phosphatidylinositol-3-kinase(PI3K)/protein kinase B(Akt)pathway proteins was quantified by Western blot.RESULTS In vitro data confirmed that Aβ_(25-35)-induced HT22 cells had a significantly lower cell viability,higher ROS level and higher apoptosis rates compared with those of control cells(all P<0.001).MgT prevented the Aβ_(25-35)-triggered oxidative stress damage by elevating viability and decreasing ROS formation and apoptosis of HT22 cells(all P<0.001).APP/PS1 mice exhibited worse cognitive performance and higher apoptosis rate of hippocampal neurons than wild-type(WT)mice(all P<0.01).Meanwhile,significant higher expression of Aβ_(1-42) and NOX4 proteins was detected in APP/PS1 mice than those of WT mice(both P<0.01).MgT also ameliorated the cognitive deficit,suppressed the apoptosis of hippocampal neuron and downregulated the expression of Aβ_(1-42) and NOX4 proteins in APP/PS1 mouse(all P<0.05).Moreover,MgT intervention significantly downregulated HIF-1αand Bax,upregulated Bcl-2 and activated the PI3K/Akt pathway both in vitro and in vivo(all P<0.05).CONCLUSION MgT exhibits neuroprotective effects against oxidative stress and hippocampal neuronal apoptosis in Aβ_(25-35)-treated HT22 cells and APP/PS1 mice.

Role of Calcium Magnesium Aluminate in Carbon-containing Bricks for Steel Ladle

Calcium magnesium aluminate,with the commercial name of MagArmour,is a synthetic material consisting of 70 mass%Al_(2)O_(3),20 mass%MgO and 10 mass%CaO,approximately.It is characterized by porous microstructure,intergranular aluminates phases and micro-crystalline spinel.Since globally launched in 2017,MagArmour has been successfully applied to various carbon-containing refractories serving for steel refining process.Lots of cases have demonstrated the role of MagArmour in enhancing the service life of carbon containing bricks for ladle lining.The benefits embody in formation of protective coating on hot surface,relief of drilling corrosion in joint positions,and elimination of grooves or cracks caused by mechanical stress concentration.In addition,MagArmour is effective in protecting graphite from deep oxidization so as to be capable of replacing the metallic or carbide anti-oxidants in carbon-containing bricks entirely.By means of chemical analysis and microstructural dissection,postmortem investigations on the used MgO-C bricks from both metal and slag zones of 120t steel refining ladle were conducted to clarify the working mechanism of MagArmour.The formation of protective coating on hot face is attributed to the dissolution of micro-crystalline spinel into contacting slag,which changes the slag chemistry so as to enhance viscosity.The improvement in corrosion/erosion resistance is highly related to the porous microstructure and dispersive aluminates.As well known,evaporation of Mg,Al and SiO,and/or internal migration,occurs in MgO-C bricks at elevated temperatures.The gaseous phases are absorbed by MagArmour particles due to the high surface area of porous microstructure and condense as corresponding oxides.These oxides react with the intergranular calcium aluminates forming liquid phase.With increasing temperature,the liquid phase seeps into the matrix under capillary force.The increased liquid amount improves the flexibility of the matrix and thus releases the internal stresses concentration resulting from mechanical stress and temperature gradient.Meanwhile,densification of the matrix microstructure occurs under the static pressure generated by liquid steel and molten slag,which blocks the channels of oxygen infiltration.

组合膨胀剂对风电灌浆料早期膨胀性能的影响

基于改进的竖向膨胀率(εv)测试方法,获得了高强风电灌浆料0~24 h、1~7 d的εv发展全曲线;并研究了掺合料比例及组合膨胀剂比例对灌浆料εv、流动度、力学强度的影响.结果表明:灌浆料0~24 h竖向膨胀率曲线呈“四阶段”特征;在0%~20%掺量范围内提高硅灰掺量,灌浆料流动度下降,0~24 h内εv曲线峰值先增大后减小;塑性膨胀剂(PEA)对24 h内εv发展起主导作用,复掺氧化钙-硫铝酸钙双源膨胀剂(HP-CSA)后,εv峰值减小,24 hεv下降、3 hεv增大,有利于控制24 h与3 h的εv差值;在1~7 d内,0.03%掺量的PEA即可促进HP-CSA膨胀效能的发挥,6%以上掺量的HP-CSA可较好补偿竖向自收缩变形而获得净膨胀灌浆料;PEA与HP-CSA组合,可发挥时间上接力、效果上协同的膨胀调控作用,可分阶段、按需设计,从而实现对灌浆料7 d内竖向膨胀率的精细调控;随组合膨胀剂掺量增加,灌浆料初始和30 min流动度无明显变化,28 d抗压强度先增大后减小;在本文研究范围内,0.06%PEA+6%HP-CSA是最优掺量组合.

金属离子抗炎作用的分子机制

背景:抵抗炎症反应是促进损伤组织修复的重要环节,改善医用生物植入材料所造成的局部炎症反应是近几年有待解决的关键问题。目的:综述常见金属离子的抗炎作用及相关分子机制,为改善生物植入材料导致的宿主早期炎症反应提供一定理论参考。方法:利用计算机检索PubMed、Web of Science、中国知网及万方数据库中相关文献,以“金属离子,镁离子,锌离子,银离子,铜离子,炎症,抗炎作用,氧化应激,免疫调节,信号通路”为中文检索词,以“metal ions,magnesium ion,zinc ion,silver ion,copper ion,inflammation,anti-inflammatory effects,oxidative stress,immunoregulation,signaling pathway”为英文检索词进行检索,通过阅读文题和摘要进行初步筛选,最终纳入80篇文献进行结果分析与总结。结果与结论:①镁、锌、银、铜等金属离子具有良好的抗炎作用,该抗炎作用的强弱与其剂量及作用时间具有强相关性,未来可考虑通过控制离子的释放速率以及调节适宜治疗浓度以达到最佳抗炎效果。②镁离子和锌离子表现出优异的抗炎活性,镁离子常以硫酸镁等化合物形式在抗炎治疗中发挥益处,锌离子则以锌饲料作为锌的主要补充来源调节机体炎症反应。③银离子和铜离子具有一定抗炎作用,但仍以优异的抗菌活性占首要地位,主要以纳米颗粒及生物涂层等方式发挥作用。④镁、锌等金属离子可与天然提取物结合形成复合物发挥抗炎作用,该方法具有价格低廉、来源广泛的优点,是可持续的绿色途径,值得临床推广。⑤镁、锌、银、铜等金属离子通过减少宿主氧化应激损伤、调节免疫细胞、抑制核转录因子κB、Toll样受体、STAT3和NOD等炎症信号通路共同发挥抗炎作用。⑥金属离子抗炎相关分子机制是一个复杂网络,并非是某个单一通路的作用,而应该是多个信号通路的集合,目前仍有许多潜在机制尚未被发掘,未来需要更加系统地阐明各个信号通路之间的相互联系。

溶胶浸渗结合电沉积制备氧化镁-磷酸钙复合抗菌涂层

背景:磷酸钙(CaP)涂层被广泛用于改善钛植入物与骨的整合,但存在感染风险,因此有必要赋予CaP涂层抗菌能力。目的:通过氧化镁(MgO)溶胶浸渗制备MgO-CaP复合涂层,评价其体外抗菌能力和细胞相容性。方法:通过滴定法确定CaP电沉积的电解液条件,在钛表面制备CaP涂层(记为Ti-CaP);采用不同质量分数(15%,30%,50%)的MgO溶胶浸渗处理CaP涂层并煅烧成为MgO-CaP复合涂层,分别记为Ti-CaP-15Mg、Ti-CaP-30Mg和Ti-CaP-50Mg,表征涂层的微观形貌、拉伸性能、临界载荷与体外Mg^(2+)释放情况。将金黄色葡萄球菌菌液分别接种于纯钛片及Ti-CaP、Ti-CaP-15Mg、Ti-CaP-30Mg和Ti-CaP-50Mg表面,24,48 h后采用稀释涂布平板法检测抗菌率。将小鼠成骨细胞悬液分别接种于纯钛片及Ti-CaP、Ti-CaP-15Mg、Ti-CaP-30Mg和Ti-CaP-50Mg涂层钛片表面,采用CCK-8法检测细胞增殖,计算细胞存活率;同时观察复合涂层浸泡于DMEM培养基中的微观形貌变化。结果与结论:①电沉积在钛表面制备出由片状磷酸八钙晶体堆积组成的多孔CaP涂层,经浸渗-煅烧处理后,MgO颗粒聚集填充磷酸八钙晶体的间隙,并且填充程度随MgO含量增加而上升;3组复合涂层第1天均出现Mg^(2+)快速释放,从第3天开始Mg^(2+)释放速率明显下降,至第7天仍可检测出少量Mg^(2+)释放;Ti-CaP-30Mg涂层钛片的屈服强度、抗拉强度、断裂生长率与纯钛片比较差异均无显著性意义(P>0.05);Ti-CaP、Ti-CaP-15Mg、Ti-CaP-30Mg和Ti-CaP-50Mg组临界载荷比较差异无显著性意义(P>0.05)。②除纯钛片及Ti-CaP无抗菌性能外,其余样品均具有良好的抗菌性能,并且抗菌率随涂层中MgO含量的增加而增大。③共培养1,3 d,Ti-CaP-15Mg组、Ti-CaP-30Mg组和Ti-CaP-50Mg组细胞存活率低于纯钛组、Ti-CaP组(P<0.05);培养5,7 d,5组间细胞存活率比较差异无显著性意义(P>0.05);随着浸泡于培养基中时间的延长,涂层中MgO的含量逐渐减少。④结果表明,通过MgO浸渗处理赋予CaP涂层抗菌性的同时保持了其生物相容性。

氧化镁膨胀剂与纳米二氧化硅协同作用对UHPC性能的影响

研究了氧化镁膨胀剂(MEA)和纳米二氧化硅(NS)对超高性能混凝土(UHPC)的力学性能和早期自收缩的影响,并采用XRD及SEM等对其早期水化反应过程和水化产物进行微观测试。结果表明,MEA和NS的掺入均会降低UHPC的流动性,二者复掺时流动性会进一步降低;掺入MEA会降低不同龄期UHPC的抗压强度,但掺入适量的NS和MEA可以明显改善UHPC的抗压强度及早期自收缩。XRD及SEM微观测试结果表明,NS可有效降低UHPC体系中氢氧化钙含量,复掺0.5%NS和6.0%MEA的UHPC体系结构更为致密,无明显的宏观孔和片状氢氧化钙,使得该UHPC具有良好的体积稳定性和力学性能。

电感耦合等离子体发射光谱法快速测定白云石、石灰石中高含量氧化钙

建立电感耦合等离子体发射光谱法测定白云石、石灰石中高含量氧化钙。样品经10 mL盐酸溶液(1∶1)、1.5 mL浓硝酸溶解后,设定测试功率为1 150 W,分析谱线波长为373.6 nm,氩气流量为0.7 L/min,辅助气流量为0.5L/min,氩气压力为0.2 MPa,观测高度为13 mm,泵转速为50 r/min,采用等离子体原子发射光谱法进行测定。钙的质量浓度在0~10.0μg/L范围内与信号强度线性良好,相关系数为0.999 9,方法检出限为3.2μg/L。采用所建方法分别测定白云石和石灰石标准样品,测定结果的相对标准偏差分别为0.28%~0.31%、0.19%~0.25%(n=6),测定平均值与标准值的相对误差分别为0.20%~0.48%、0.18%~0.22%。分别用所建方法与GB/T 3286.1—2012方法测定白云石、石灰石样品,测定结果的相对误差分别为0.26%~0.29%、0.34%~0.48%。该方法满足白云石、石灰石中高含量氧化钙的测定要求。

粉煤灰中氧化钙含量对多孔陶瓷性能的影响

以工业废弃物粉煤灰为主料,制备多孔陶瓷具有来源广、成本低的优点,但粉煤灰的化学成分因煤的产地、燃烧方式有很大差异。笔者以粉煤灰为主原料,添加少量Al_(2)O_(3)和粘结剂干压成形后,在较低温度下烧制成多孔陶瓷,研究粉体粒径以及氧化钙含量对多孔陶瓷性能的影响。其结果表明:在相同烧成温度下,原料粒径对制品性能有较大影响;与常规粉煤灰相比,高钙粉煤灰具有优良的烧结活性,高的抗折强度和纯水渗透率。在1150℃保温2 h,烧成时性能最优,抗折强度为72 MPa、纯水渗透率为10783 L·m^(-2)·h^(-1)·bar^(-1)。

跳仓法与补偿收缩混凝土组合技术在地下室工程中的应用研究

采用钙镁复合膨胀剂配制补偿收缩混凝土能够弥补跳仓法施工的混凝土存在收缩变形过大的缺陷,跳仓法与补偿收缩混凝土组合技术在工程实体结构应用中具有较好的裂缝控制效果。实体结构监测数据表明,混凝土内部早期温度修正后微应变为31με~104με,60 d龄期内缓慢降低至-153με~-48με,采用钙镁复合膨胀剂配制的补偿收缩混凝土在较长龄期内收缩量较小,开裂风险较低;不同板块收缩变形量与跳仓接壤板块数量和分块结构尺寸2个因素有关;可通过增加保温材料层数或厚度以控制早期降温速率和温降收缩量。

取向硅钢表面点状露金成因研究

对取向硅钢表面的点状露金缺陷的形成原因进行了模拟和研究,采用金相显微镜观察缺陷表面形貌,再采用扫描电镜的面扫描功能分析缺陷成分分布。研究结果表明:取向硅钢在夏季及秋季生产时,因为降雨量多且气温高,空气湿度大,空气中的水蒸气会冷凝在硅钢卷上,硅钢卷表面氧化镁的含水率升高,在水和氧气的作用下,硅钢基体表面产生很多氧化腐蚀点。这些氧化腐蚀点会阻碍高温退火过程中硅酸镁底层的形成,并且在温度升高后与罩室炉内的氢气反应,氧化产物被还原,经酸洗后,最终成品表面留下圆形的白色露金。

ICP-AES法测定含铝预熔性渣洗料中钙、镁、硅、铝氧化物

研究使用电感耦合等离子体发射光谱法测定炼钢含铝预熔性渣洗料中钙、镁、硅、铝氧化物的分析条件以及处理样品的方式方法,为便于区别金属铝和三氧化二铝,创建了一种新型的仪器分析方法。由于试样中金属铝的存在,采用先酸溶再碱融的处理方式,并采用配置相似基体的方法消除基体干扰。研究了渣洗料的溶样过程、仪器分析参数的选择、基体的干扰消除等对分析结果影响,在优化仪器分析参数和分解试样实验过程中,试样分析结果相对标准偏差远小于1.0%,分析结果准确度和精密度都很高。因此,该方法可取代化学分析法,是一种准确、快速的仪器分析方法。

氧化镁作为沉淀剂制备氢氧化镍钴产品的沉淀结晶试验

根据海外某公司生产工艺中采用氢氧化钠作为沉淀剂来生产氢氧化镍钴产品,在生产过程中存在沉淀结晶、干燥脱水等有关工艺问题,造成产品含水率高,进而使得产品海外运回中国的运输成本过高,开展了氢氧化镍钴结晶和干燥工艺研究,在不改变现有生产工艺主流程的前提下,拟探索研究以氧化镁作为沉淀剂制备氢氧化镍钴产品,降低产品的含水率。通过系统的实验研究,以国外某氧化镁作为沉淀剂得到的氢氧化镍钴产品中Ni、Co的含量略有下降,产品含水率得到显著下降,有进一步用于工业应用的可能。

外约束作用对钢管内混凝土力学性能的影响

试验研究了掺入不同组成的钙镁复合膨胀剂对管内混凝土工作与力学性能的影响。结果表明,复合膨胀剂中氧化镁比例的增加会降低管内自密实混凝土流动性,而对间隙通过性和抗离析性影响不大。对于掺有复合膨胀剂的管内混凝土而言,相较于不受外约束作用的自由试件,其二维、三维外约束试件不同龄期抗压强度与弹性模量均显著增加。复合膨胀材料中氧化钙比例较高时,这一提升作用更加明显,可作为管内混凝土配合比设计时的安全储备。

Preparation of TiCl4 with the Titanium Slag Containing Magnesia and Calcia in a Combined Fluidized Bed

This paper describes a new method for producing TiCl4 by chloridizing materials of high content CaO and MgO, in which a combined fluidized bed is used as a reactor to avoid agglomeration between particles caused by molten CaCl2 and MgCl2. The combined fluidized bed consists of at least a riser tube and a semi-circulating fluidized bed. Two kinds of high titanium slag, in which the total mass content of CaO and MgO is 2.03% and 9.09% respectively, are employed to examine the anti-agglomeration effect and the conversion of the materials when the temperature ranges are between 923.15K and 1073.15K, gas apparent velocity 0.7--1.1m.s-1, and inlet amount of solid materials is 4.6-7.0kg·h^-1. It is found that the anti-agglomeration effect in the combined fluidized bed is satisfactory and the new method can achieve a TiCl4 production capacity of 14.0-75.4t·m^-2·d^-1 in relation to 25.0-- 40.0t·m^-2·d^-1 from the conventional bubble bed. Furthermore, low-temperature chloridization, for example, at 923K or 973K, can also be used to produce TiCl4 and avoid agglomeration.